Bacteria come in a variety of shapes, including rods and spheres. They are classified based on cell wall structure and how they take stain. Bacteria require nutrients like carbon, nitrogen, and phosphorus for growth. They multiply by binary fission, with growth occurring in lag, exponential, stationary, and death phases according to a growth curve. Temperature, pH, oxygen, salt concentration, and nutrients all impact bacterial growth rates.
This document discusses the physiology of microorganisms, including their growth, metabolism, and cultivation. It explains that bacteria multiply through binary fission, which allows populations to double within a set generation time. Growth occurs in distinct phases on a curve and is influenced by temperature, pH, oxygen levels, and other environmental factors. Metabolism involves both catabolism, through processes like respiration and fermentation, and anabolism to build cell structures. Microbes can be cultivated using culture media tailored to their physical and nutritional requirements.
The document discusses different types of microorganisms that can be found on foods, including bacteria, molds, and yeasts. It describes their structures, modes of reproduction, and optimal temperature and moisture conditions for growth. Several pathogens that can cause foodborne illness are also identified. Food preservation aims to prevent spoilage and ensure safety by controlling factors like pH, water activity, temperature, and oxygen levels that influence microbial growth.
MC3 - Week 3 Microbial Growth and Control.pptMCFototana1
This document discusses microbial growth and methods for controlling microbial growth. It covers the following key points:
1) Microbial growth refers to the increase in number of microbial cells through processes like binary fission rather than an increase in cell size. Growth is influenced by available nutrients, temperature, pH, oxygen levels and other environmental factors.
2) Methods for controlling microbial growth include physical agents like heat, radiation, filtration and desiccation as well as chemical disinfectants, antiseptics and antibiotics. These work by killing microbes or inhibiting their growth.
3) Proper control of microbial growth is important for preventing disease transmission and food spoilage. A variety of chemical and physical methods can be
3 bio265 microbial growth instructor dr di bonaventuraShabab Ali
Microbial growth requires certain physical, chemical, and energy requirements to be met. Understanding these growth requirements allows us to control microbes, especially pathogens. Key growth factors include temperature, pH, oxygen levels, and nutrients. Different microbes have varying optimal temperature, pH, and oxygen ranges. Using specialized culture media that provide appropriate conditions enables isolation and growth of microbes from clinical specimens in the laboratory, facilitating identification of pathogens.
The document summarizes microbial growth requirements and culture techniques. It discusses the temperature, pH, oxygen, pressure, and nutritional requirements for microbial growth. It also describes different types of culture media such as selective, differential and enrichment media. Various culture methods are outlined, including anaerobic culturing and preserving cultures through lyophilization or deep freezing.
Lag phase
Adaptation, preparation for division, increase in size and density.
Log phase (logarithmic or exponential).
Max. growth rate, increase linearly with time.
Growth yield and growth rate.
Stationary phase
Depletion of nutrient, accumulation of toxic. materials, cell crowding.
Decline phase
Bacteria come in a variety of shapes, including rods and spheres. They are classified based on cell wall structure and how they take stain. Bacteria require nutrients like carbon, nitrogen, and phosphorus for growth. They multiply by binary fission, with growth occurring in lag, exponential, stationary, and death phases according to a growth curve. Temperature, pH, oxygen, salt concentration, and nutrients all impact bacterial growth rates.
This document discusses the physiology of microorganisms, including their growth, metabolism, and cultivation. It explains that bacteria multiply through binary fission, which allows populations to double within a set generation time. Growth occurs in distinct phases on a curve and is influenced by temperature, pH, oxygen levels, and other environmental factors. Metabolism involves both catabolism, through processes like respiration and fermentation, and anabolism to build cell structures. Microbes can be cultivated using culture media tailored to their physical and nutritional requirements.
The document discusses different types of microorganisms that can be found on foods, including bacteria, molds, and yeasts. It describes their structures, modes of reproduction, and optimal temperature and moisture conditions for growth. Several pathogens that can cause foodborne illness are also identified. Food preservation aims to prevent spoilage and ensure safety by controlling factors like pH, water activity, temperature, and oxygen levels that influence microbial growth.
MC3 - Week 3 Microbial Growth and Control.pptMCFototana1
This document discusses microbial growth and methods for controlling microbial growth. It covers the following key points:
1) Microbial growth refers to the increase in number of microbial cells through processes like binary fission rather than an increase in cell size. Growth is influenced by available nutrients, temperature, pH, oxygen levels and other environmental factors.
2) Methods for controlling microbial growth include physical agents like heat, radiation, filtration and desiccation as well as chemical disinfectants, antiseptics and antibiotics. These work by killing microbes or inhibiting their growth.
3) Proper control of microbial growth is important for preventing disease transmission and food spoilage. A variety of chemical and physical methods can be
3 bio265 microbial growth instructor dr di bonaventuraShabab Ali
Microbial growth requires certain physical, chemical, and energy requirements to be met. Understanding these growth requirements allows us to control microbes, especially pathogens. Key growth factors include temperature, pH, oxygen levels, and nutrients. Different microbes have varying optimal temperature, pH, and oxygen ranges. Using specialized culture media that provide appropriate conditions enables isolation and growth of microbes from clinical specimens in the laboratory, facilitating identification of pathogens.
The document summarizes microbial growth requirements and culture techniques. It discusses the temperature, pH, oxygen, pressure, and nutritional requirements for microbial growth. It also describes different types of culture media such as selective, differential and enrichment media. Various culture methods are outlined, including anaerobic culturing and preserving cultures through lyophilization or deep freezing.
Lag phase
Adaptation, preparation for division, increase in size and density.
Log phase (logarithmic or exponential).
Max. growth rate, increase linearly with time.
Growth yield and growth rate.
Stationary phase
Depletion of nutrient, accumulation of toxic. materials, cell crowding.
Decline phase
This document discusses various methods for controlling microbial growth, including sterilization, disinfection, sanitization, and pasteurization. It describes how physical methods like heat, refrigeration, drying, and filtration can be used to destroy or inhibit microbes. The effectiveness of different antimicrobial methods depends on factors like the site being treated, the microorganism's susceptibility, environmental conditions, and the presence of organic materials. Precautions range from biosafety level 1 with minimal procedures to level 4 with the most stringent isolation and protective equipment.
The document discusses different types of microorganisms including bacteria, algae, fungi, protozoa, and viruses. It describes their key characteristics and provides examples. The document also discusses how abiotic factors like nutrients, pH, temperature, and light intensity affect microbial activity. It explains how some microorganisms are useful as decomposers, for nitrogen fixation, and in human and termite digestion. Additionally, it covers how harmful microorganisms can cause disease and food spoilage and how pathogens are transmitted. Methods for controlling pathogens and uses of microorganisms in biotechnology are also summarized.
Bacterial growth and metabolism can be summarized in 3 points:
1. Bacteria multiply through binary fission and grow in colonies, turbid suspensions, or biofilms. Their growth rate is measured by doubling time.
2. Bacterial growth occurs in four phases - lag, exponential, stationary, and decline - as seen in an idealized growth curve obtained from broth culture.
3. Bacteria metabolize nutrients through various pathways like glycolysis and the TCA cycle to generate energy in the form of ATP. They can adapt and respond to different environmental stresses through stress responses and regulatory systems.
cell culture define as removal of cells from an animal or plant and their subsequent growth in a favorable artificial environment.
Today, it has large prospective, Used in cellular and molecular biology
Studying the normal physiology and biochemistry of cells(e.g., metabolic studies, aging)
Used in drug screening and development and large scale manufacturing of biological compounds (e.g., vaccines, therapeutic proteins) etc.
The document discusses mammalian cell culture and its applications. It provides details on the conditions needed for cell culture, including aseptic conditions, growth medium, temperature, pH, and gas exchange. It also discusses primary and continuous mammalian cell cultures. Primary cultures have a limited lifespan while continuous cell lines can divide indefinitely and are used for research and biotechnology applications.
This document discusses microbial nutrition and growth. It explains that microbes require nutrients for energy, cellular activities, and constructing new cellular components. The main nutrients include carbon, nitrogen, phosphorus, and trace elements. It categorizes microbes based on their carbon and energy sources. It also describes the physical and chemical requirements for microbial growth, including temperature, pH, oxygen levels, and nutrients. It discusses culture media, methods for measuring growth, and techniques for obtaining pure cultures.
This document summarizes bacterial growth and requirements. It discusses that bacterial growth involves an increase in all cellular components through binary fission. Bacteria require nutrients and physical conditions to promote growth. Bacterial growth is exponential, and the generation time is the time it takes the population to double. Most bacteria live in biofilms, which are resistant to antibiotics. Bacteria are grown in pure culture using techniques like streak plating. Nutrients like carbon, nitrogen, water and minerals as well as temperature, pH, oxygen and osmotic conditions impact bacterial growth. Bacterial growth follows distinct phases of lag, log, stationary and death.
The document discusses the nutritional requirements and environmental factors affecting the growth of bacteria. It states that bacteria require a source of carbon, nitrogen, water, inorganic salts, and growth factors for optimal growth. The main environmental factors that affect bacterial growth are temperature, pH, oxygen levels, moisture, carbon dioxide, light, osmotic pressure, and mechanical or sonic stress. The document also describes bacterial metabolism, including aerobic respiration and anaerobic fermentation, and outlines the different phases of a bacterial growth curve.
bacteria3.pptFirst discovered in extreme environments Methanogens: Harvest en...MANISHPARIDA1
Bacteria are microscopic single-celled organisms that can cause disease in humans. They come in different shapes (coccus, bacillus, spirillum) and are classified by their cell structure and staining (Gram-positive, Gram-negative). Bacteria reproduce through binary fission and conjugation. Many diseases are caused by pathogenic bacteria, such as strep throat, tuberculosis, cholera, and tetanus. Antibiotics can treat bacterial infections by inhibiting bacterial cell wall synthesis or protein/DNA synthesis. Vaccines work by exposing the immune system to killed or weakened bacteria to develop immunity against disease. Proper cooking, sanitization, and antibiotics control bacterial growth and spread of disease.
Factors that affecting-microbial-growth.pdfdawitg2
Microbial growth requires both physical and nutritional requirements to be met. Bacteria will grow within a certain temperature, pH, oxygen, and osmotic pressure range. Nutritionally, bacteria require carbon, nitrogen, phosphorus, sulfur, and trace elements which they obtain from organic and inorganic sources. Bacterial growth occurs in four phases - lag, log/exponential, stationary, and death - as seen in a bacterial growth curve. Factors like temperature, nutrients, water, oxygen levels, and pH can affect the bacterial growth rate. Bacteria are enumerated using methods like viable plate counts and direct microscopic cell counts.
This document discusses various topics relating to bacterial growth, including:
- Bacterial growth occurs through binary fission or budding, where a parent cell splits into two daughter cells. Generation time is the time required for a cell to divide.
- Bacterial growth can be measured directly through plate counts, which involve serial dilutions and counting colony-forming units, or indirectly through metabolic activity.
- Bacterial growth phases include a lag phase, log/exponential phase, stationary phase, and death phase.
- Bacteria have various physical and chemical requirements for growth, such as appropriate temperatures, pH levels, oxygen levels, carbon sources, and nutrients.
- Culture media such as solid and liquid
The document discusses microorganisms classified by their significance to food, including pathogenic organisms that cause foodborne diseases, spoilage organisms, and useful organisms used to produce fermented foods. It covers the major bacteria, viruses, parasites, and toxigenic moulds that can contaminate foods like meat, milk, eggs, fish, vegetables, fruits, and more. It also addresses the ecological factors influencing microbial growth, such as temperature, pH, water activity, and oxygen tension. The ecology of various foodborne pathogens is described.
Food microbiology is the study of microorganisms that are present in foods and can affect food quality and safety. Microbes can be beneficial, neutral, or harmful to humans. Foods provide excellent nutrients to support microbial growth. There are many factors that affect microbial growth in foods, including intrinsic factors like pH, moisture content, and nutrients as well as extrinsic factors like temperature, relative humidity, gases, and time. Microbial spoilage of foods is evidenced by changes in appearance, texture, odor, and flavor and is caused by bacteria, molds, and yeasts growing in the food.
The document discusses mammalian cell culture and microbiology. It provides information on:
1) The importance of cell culture for biotechnology and research applications like studying drug effects and genetically engineering bacteria.
2) The optimal conditions needed for cell growth, including the type of growth medium, temperature, pH, and aseptic techniques.
3) How microbial cells can be cultured on small or large scales for uses in food production, chemical synthesis, and more.
The document discusses several types of anaerobic spore-forming bacilli including Clostridium species. It describes their morphology, growth characteristics, toxin production and role in various diseases. Specifically, it covers Clostridium perfringens, Clostridium tetani, Clostridium botulinum, and Clostridium difficile. It notes their clinical significance, including the potent neurotoxins produced by C. tetani and C. botulinum that cause tetanus and botulism respectively.
The material describes components of industrial fermentation media with their respective metabolic importance for the industrial microbes. it also addresses industrial scale sterilization methods.
This document discusses bacterial metabolism and classification of nonfermenting gram-negative bacilli (GNB). It describes how bacteria derive energy from carbohydrate degradation pathways and how they are classified based on this. Key nonfermenters like Pseudomonas aeruginosa, Burkholderia cepacia, and Acinetobacter baumannii are then discussed in detail regarding their laboratory identification, clinical significance, and antibiotic treatment.
This document discusses various methods for controlling microbial growth, including sterilization, disinfection, sanitization, and pasteurization. It describes how physical methods like heat, refrigeration, drying, and filtration can be used to destroy or inhibit microbes. The effectiveness of different antimicrobial methods depends on factors like the site being treated, the microorganism's susceptibility, environmental conditions, and the presence of organic materials. Precautions range from biosafety level 1 with minimal procedures to level 4 with the most stringent isolation and protective equipment.
The document discusses different types of microorganisms including bacteria, algae, fungi, protozoa, and viruses. It describes their key characteristics and provides examples. The document also discusses how abiotic factors like nutrients, pH, temperature, and light intensity affect microbial activity. It explains how some microorganisms are useful as decomposers, for nitrogen fixation, and in human and termite digestion. Additionally, it covers how harmful microorganisms can cause disease and food spoilage and how pathogens are transmitted. Methods for controlling pathogens and uses of microorganisms in biotechnology are also summarized.
Bacterial growth and metabolism can be summarized in 3 points:
1. Bacteria multiply through binary fission and grow in colonies, turbid suspensions, or biofilms. Their growth rate is measured by doubling time.
2. Bacterial growth occurs in four phases - lag, exponential, stationary, and decline - as seen in an idealized growth curve obtained from broth culture.
3. Bacteria metabolize nutrients through various pathways like glycolysis and the TCA cycle to generate energy in the form of ATP. They can adapt and respond to different environmental stresses through stress responses and regulatory systems.
cell culture define as removal of cells from an animal or plant and their subsequent growth in a favorable artificial environment.
Today, it has large prospective, Used in cellular and molecular biology
Studying the normal physiology and biochemistry of cells(e.g., metabolic studies, aging)
Used in drug screening and development and large scale manufacturing of biological compounds (e.g., vaccines, therapeutic proteins) etc.
The document discusses mammalian cell culture and its applications. It provides details on the conditions needed for cell culture, including aseptic conditions, growth medium, temperature, pH, and gas exchange. It also discusses primary and continuous mammalian cell cultures. Primary cultures have a limited lifespan while continuous cell lines can divide indefinitely and are used for research and biotechnology applications.
This document discusses microbial nutrition and growth. It explains that microbes require nutrients for energy, cellular activities, and constructing new cellular components. The main nutrients include carbon, nitrogen, phosphorus, and trace elements. It categorizes microbes based on their carbon and energy sources. It also describes the physical and chemical requirements for microbial growth, including temperature, pH, oxygen levels, and nutrients. It discusses culture media, methods for measuring growth, and techniques for obtaining pure cultures.
This document summarizes bacterial growth and requirements. It discusses that bacterial growth involves an increase in all cellular components through binary fission. Bacteria require nutrients and physical conditions to promote growth. Bacterial growth is exponential, and the generation time is the time it takes the population to double. Most bacteria live in biofilms, which are resistant to antibiotics. Bacteria are grown in pure culture using techniques like streak plating. Nutrients like carbon, nitrogen, water and minerals as well as temperature, pH, oxygen and osmotic conditions impact bacterial growth. Bacterial growth follows distinct phases of lag, log, stationary and death.
The document discusses the nutritional requirements and environmental factors affecting the growth of bacteria. It states that bacteria require a source of carbon, nitrogen, water, inorganic salts, and growth factors for optimal growth. The main environmental factors that affect bacterial growth are temperature, pH, oxygen levels, moisture, carbon dioxide, light, osmotic pressure, and mechanical or sonic stress. The document also describes bacterial metabolism, including aerobic respiration and anaerobic fermentation, and outlines the different phases of a bacterial growth curve.
bacteria3.pptFirst discovered in extreme environments Methanogens: Harvest en...MANISHPARIDA1
Bacteria are microscopic single-celled organisms that can cause disease in humans. They come in different shapes (coccus, bacillus, spirillum) and are classified by their cell structure and staining (Gram-positive, Gram-negative). Bacteria reproduce through binary fission and conjugation. Many diseases are caused by pathogenic bacteria, such as strep throat, tuberculosis, cholera, and tetanus. Antibiotics can treat bacterial infections by inhibiting bacterial cell wall synthesis or protein/DNA synthesis. Vaccines work by exposing the immune system to killed or weakened bacteria to develop immunity against disease. Proper cooking, sanitization, and antibiotics control bacterial growth and spread of disease.
Factors that affecting-microbial-growth.pdfdawitg2
Microbial growth requires both physical and nutritional requirements to be met. Bacteria will grow within a certain temperature, pH, oxygen, and osmotic pressure range. Nutritionally, bacteria require carbon, nitrogen, phosphorus, sulfur, and trace elements which they obtain from organic and inorganic sources. Bacterial growth occurs in four phases - lag, log/exponential, stationary, and death - as seen in a bacterial growth curve. Factors like temperature, nutrients, water, oxygen levels, and pH can affect the bacterial growth rate. Bacteria are enumerated using methods like viable plate counts and direct microscopic cell counts.
This document discusses various topics relating to bacterial growth, including:
- Bacterial growth occurs through binary fission or budding, where a parent cell splits into two daughter cells. Generation time is the time required for a cell to divide.
- Bacterial growth can be measured directly through plate counts, which involve serial dilutions and counting colony-forming units, or indirectly through metabolic activity.
- Bacterial growth phases include a lag phase, log/exponential phase, stationary phase, and death phase.
- Bacteria have various physical and chemical requirements for growth, such as appropriate temperatures, pH levels, oxygen levels, carbon sources, and nutrients.
- Culture media such as solid and liquid
The document discusses microorganisms classified by their significance to food, including pathogenic organisms that cause foodborne diseases, spoilage organisms, and useful organisms used to produce fermented foods. It covers the major bacteria, viruses, parasites, and toxigenic moulds that can contaminate foods like meat, milk, eggs, fish, vegetables, fruits, and more. It also addresses the ecological factors influencing microbial growth, such as temperature, pH, water activity, and oxygen tension. The ecology of various foodborne pathogens is described.
Food microbiology is the study of microorganisms that are present in foods and can affect food quality and safety. Microbes can be beneficial, neutral, or harmful to humans. Foods provide excellent nutrients to support microbial growth. There are many factors that affect microbial growth in foods, including intrinsic factors like pH, moisture content, and nutrients as well as extrinsic factors like temperature, relative humidity, gases, and time. Microbial spoilage of foods is evidenced by changes in appearance, texture, odor, and flavor and is caused by bacteria, molds, and yeasts growing in the food.
The document discusses mammalian cell culture and microbiology. It provides information on:
1) The importance of cell culture for biotechnology and research applications like studying drug effects and genetically engineering bacteria.
2) The optimal conditions needed for cell growth, including the type of growth medium, temperature, pH, and aseptic techniques.
3) How microbial cells can be cultured on small or large scales for uses in food production, chemical synthesis, and more.
The document discusses several types of anaerobic spore-forming bacilli including Clostridium species. It describes their morphology, growth characteristics, toxin production and role in various diseases. Specifically, it covers Clostridium perfringens, Clostridium tetani, Clostridium botulinum, and Clostridium difficile. It notes their clinical significance, including the potent neurotoxins produced by C. tetani and C. botulinum that cause tetanus and botulism respectively.
The material describes components of industrial fermentation media with their respective metabolic importance for the industrial microbes. it also addresses industrial scale sterilization methods.
This document discusses bacterial metabolism and classification of nonfermenting gram-negative bacilli (GNB). It describes how bacteria derive energy from carbohydrate degradation pathways and how they are classified based on this. Key nonfermenters like Pseudomonas aeruginosa, Burkholderia cepacia, and Acinetobacter baumannii are then discussed in detail regarding their laboratory identification, clinical significance, and antibiotic treatment.
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2. At the end of this lecture students should be able to
Explain why bacteria are used for metabolic studies
Explain how microorganisms acquire energy and nutrients
Explain the growth (culture) media
Discuss the four main factors that affect microbial growth
Differentiate among the various media used in culturing
microorganisms
Know the significance of sterility in growing microorganisms
Explain the bacterial growth patterns in broth and on agar
Explain why bacteria die during the death phase
Define the different terms (e.g. –cidal, -static, sepsis) associated
with the control of microbial growth
BSc N/M CUNIMA 2
3. Vital life processes
Bacteria mostly used for such studies
Inexpensive
Take up little space
Quick reproduction
Easily observable morphology, nutritional needs and metabolic
reactions
Available species to represent all forms nutritional types
Each bacteria produce cells like itself
BSc N/M CUNIMA 3
4. Nutrition required for cellular structure formation,
development, multiplication and vitality
Carbon, oxygen, hydrogen, nitrogen, sulphur, phosphorous,
(macro elements)
Micro elements include; manganese, potassium, calcium,
magnesium, iron zinc, cobalt, molybdenum, nickel and
copper
Essential nutrients: materials not synthesized by
organisms
BSc N/M CUNIMA 4
5. Phototrophs: Use light as energy source
Chemotrophs:
Lithotrophs: Use inorganic chemicals for energy
Organotrophs: Use organic materials as energy source
Autotrophs: Use CO2 as source of carbon
Heterotrophs: Use organic compounds
Photoautotrophs: Use light and CO2 (e.g cynanobacteria)
Photoheterotphs: Use light and organic compounds (e.g.
nonsulfur bacteria)
Chemoautotrophs: Chemical and CO2
Chemoheterotrophs: Use chemical energy and organic
compounds for carbon
BSc N/M CUNIMA 5
6. Optimal growth condition necessary
Inability to sustain optimum condition limit growth and lead to
massive death of microorganisms
Survivors of sub-optimum conditions lose some phenotypic
characteristics
4 major factors affect bacterial growth
Physical factors
Chemical factors
Biological factors
Mechanical factors
BSc N/M CUNIMA 6
7. Temperature
Heat
Significantly affect growth
Different species have maximum and minimum growth temperatures
Generally optimum growth temperature 5-10C lower than the maximum but 20-
30C higher than the minimum
Pathogenic microorganisms have a narrow temperature growth range
Optimum growth temperature may not be appropriate for synthesis of some
essential components or bacterial products
BSc N/M CUNIMA 7
8. Bacteria classified into 4 groups based on their temperature ranges
of growth
Psychrophiles: 5-15C e.g. A. salmonicida
Mesophiles: 30-45C most pathogenic bacteria
Thermophiles: 50-60C e.g. B. stearothermophilus, Pyrolobus
fumarii
BSc N/M CUNIMA 8
16. Aseptically prepared environment to grow microorganisms
Some mo grow on simple defined media
Many organisms require complex media
Available in liquid and solid forms
Solid media obtained by addition of agar into the media
Some ingredients in media restrict growth of certain organisms while
permitting others e.g. antibiotics in fungal media
Media for yeasts and moulds have lower pH than bacterial
BSc N/M CUNIMA 16
17. Basal media: Simple synthetic media with a carbon and energy source
plus an inorganic source of nitrogen e.g. peptone water or nutrient broth
Enriched media: Meets nutritional requirements of most bacteria e.g.
blood agar
Selective media: Suppress unwanted microbes, or encourage desired
microbes
Differential media: Distinguish colonies of specific microbes from others
Enrichment media: Similar to selective media but designed to increase
the numbers of desired microorganisms to a detectable level without
stimulating the rest of the bacterial population
Transport media: Devised to maintain the viability of desired pathogens
and avoid overgrowth of other contaminants
BSc N/M CUNIMA 17
18. Peptone: Consists of water soluble products from lean meat or other
protein material e.g. casein, fibrin, soya flour etc
Available as golden granular powder with low moisture content
Highly hygroscopic
Meat extract: Used as a substitute to fresh meat infusion
Yeast extract: Prepared from washed cells of brewer’s yeast
Contains amino acids, growth factors and inorganic salts
Comprehensive source of growth, can be substituted by meat extract
Blood: Aseptically collected blood should be used
Should be rendered non-coagulating by defibrination, heparinization or
adding citrate or oxalate
Blood so treated can be kept for 2 months but should not be allowed to
freeze
Serum: Used in some media
Can be filter-sterilized
BSc N/M CUNIMA 18
19. Water: Use glass distilled or demineralised water
Agar: Prepared from seaweed
1-1.5% w/v concentration enough to gel
Composed of long chain polysaccharide of D-galactopyranose
Has impurities such as inorganic salts and traces of long chain fatty acids
Dissolves at about 100C
Does not add to the nutritive properties of a medium
Can be decomposed by some marine bacteria
Carbohydrates: Used in the form of starch or sugars
Glucose (dextrose) only sugar used as nutrient
Ability to ferment sugar aid in identification
BSc N/M CUNIMA 19
20. Bacteria and yeasts divide by binary fission
Doubling of macromolecules
Septum formation
Constriction
Generation time
Growth consistent till stationary
Broth
◦ turbidity
Agar
◦ Colony
◦ Yeast colonies
◦ Mould colonies
Planktonic (free) and sessile (attached) growth
BSc N/M CUNIMA 20
22. A: The lag phase
Cells adjust to new growth conditions and growth is unbalanced
Length of the period depend on the extent of change
B: Exponential (log) Phase
Cells divide at a constant rate depending on the composition of the growth medium
and the conditions of incubation
C: Stationary Phase
Exponential growth cannot be continued forever in a batch culture (e.g. a closed
system such as a test tube or flask)
Population growth is limited by factors such as
Exhaustion of available nutrients
Accumulation of inhibitory metabolites or end products
Lack of "biological space".
D: Death Phase
BSc N/M CUNIMA 22
23. Restricted growth
Exposed to numerous factors
Difficulty in accessing nutrients by organisms on the apex
Nutrients underneath and on the sides get depleted
Secondary metabolic activities not released
Degeneration of apex colonies due to starvation
Growth of other colonies exacerbate the scarcity of available nutrients
Colonies underneath affected by the weight of the colonies above hence degeneration
takes place
Toxic metabolites by organisms underneath spread through the agar
Diffusion made more difficult by the drying of the media
Colony: A cluster of organisms growing on the surface of or within a solid medium,
usually cultured from a single cell
BSc N/M CUNIMA 23
27. Germicide/Biocide A chemical agent that kills microorganisms
Antisepsis Refers to the destruction of microbial life on a living object
Disinfection
Refers to the killing of microbes on inanimate objects or
materials
Sterilization Kills or removes all forms of life, including bacterial endospores
Static Processes or chemical agents that inhibit microbial growth
Sanitization
Usually used by the food industry. Reduces microbes on eating
utensils to safe, acceptable levels for public health.
Pasteurization
A heating process that reduces the number of spoilage germs
and eliminates pathogens in milk and other heat sensitive foods
Clean
Refers to the removal of visible dirt and debris from tissues or
objects
BSc N/M CUNIMA 27
30. Most frequently used means to destroy microbes
Economical and easily controlled
Death occurs more rapidly as temperature increases.
The nature of heat is also important:
◦ Moist heat penetrates better than dry heat
BSc N/M CUNIMA 30
31. Moist Heat
Boiling: Kills in 10 min but some bacteria resistant
Autoclaving: 121⁰C at 15psi (pounds per square inch) for at least 15 min
Pasteurization:
◦ 63⁰C for 30 min (LTLT)
◦ 72 ⁰C for 15 sec (HTST)
◦ 140⁰ C for 15 sec (Ultra-High Temp)
◦ 149⁰C for 0.5 sec (UHT)
Tyndallization steam for 30 minutes on each of three successive days.
Dry Heat
Flaming of inoculating loops and the sterilization of glassware in hot air
drying ovens
BSc N/M CUNIMA 31
32. o Effect of heat on bacteria is determined by
o Temperature
o Type of the bacteria involved
o Number of bacterial cells
o Presence/absence of organic matters
o pH
o Growth phase
o Humidity
o Period
BSc N/M CUNIMA 8
33. Slow down and inhibit the growth of most microbes
Some spoilage germs and psychrophiles can continue to
replicate at cooler temperatures
BSc N/M CUNIMA 33
34. Lag phase increased towards freezing
Only psychrophiles continue growth at chilling temperatures
Reaction to freezing range from virtually no effect to injury and cell death
Most spores survive with nearly no effect
Gram negative more sensitive to freezing than Gram positives
Freezing may cause sublethal injury of bacteria which in turn lead to
underestimation of cell count if done from frozen specimen
-2 to -10C very detrimental to bacterial cells
Slow freezing causes maximum injury while minimum injury is observed during
rapid freezing
BSc N/M CUNIMA 10
35. Commonly employed for substances that can not tolerate heat
Membrane filters with pore sizes between 0.2-0.45 µm are used
Remove particles from solutions that can't be autoclaved
Membrane filtration of beer eliminates spoilage germs and
pasteurization is no longer needed
Sub-micron filters also marketed for removal of protozoan cysts from
drinking water.
BSc N/M CUNIMA 35
36. Effects of types of radiation depend on three important factors:
◦ Time (of exposure)
◦ Distance (from the source)
◦ Shielding (how penetrating is the radiation?)
Nonionizing radiation
Microwaves and ultra violet radiation.
◦ The killing effect of microwaves are largely due to the heat that they generate.
◦ radiation is of short wavelength, between 220 and 300 nm and is not very penetrating
◦ Kill exposed microbes by causing damage to their DNA.
Ionizing radiation
Includes gamma rays and X rays which are highly penetrating to cells
and tissues and have potent antimicrobial effects.
Irradiation approved for sterilization of surgical supplies, vaccines and
drugs and in food industries
Irradiation known to eliminate E. coli Listeria, Campylobacter and
Salmonella from meat.
BSc N/M CUNIMA 36
37. A very useful means of food preservation and to control the growth of
spoilage germs and pathogens
Foods that have a high water activity are most subject to spoilage
and typically must be refrigerated or frozen
This process creates hypertonic conditions and causes water to
leave bacterial cells (plasmolysis)
Lyophilization, a process in which liquids are quick-frozen and then
subjected to evacuation, which dries the material
BSc N/M CUNIMA 37
38. Properties of an ideal antimicrobial
agent
Fast-acting
Acts against many microbes without
harming tissues (selective toxicity)
Penetrating power (improves if dirt and
debris are first removed)
Inexpensive
Easy to prepare
Chemically stable
Inoffensive odor
Not harmful to the environment
BSc N/M CUNIMA 38
39. Microbial Targets Chemical(s)
Vegetative bacterium:
Cell wall
Formaldehyde , Chlorine-releasing agents (CRAs),
Mercury, Phenols
Cytoplasmic coagulation
Chlorhexidine , Glutaraldehyde , Hexachlorophene ,
Mercurial compounds , Silver salts, QACS
Cell membrane: membrane
potential or electron transport
Hexachlorophene , Phenols, Parabens , Weak acids
used as food preservatives such as benzoic, sorbic
and proprionic acids
Leakage of cell components Phenols, Chlorhexidine , Alcohols , QACs
Nucleic acids Alkylating agents such as ethylene oxide gas
Bacterial endospores:
Spore core Glutaraldehyde , Formaldehyde
Spore cortex
CRAs, Glutaraldehyde , Nitrous acid , Nitrates/nitrates
act as food preservatives by preventing
germination of endosporesBSc N/M CUNIMA 39
42. Antimicrobial agent
◦ Substance with inhibitory properties against microorganisms
(includes antibiotics and synthetic compounds) but minimal effects
on mammalian cells
Antibiotic
◦ Produced by microorganisms and acts on other microorganisms
Semi-synthetic antibiotics
◦ Antibiotics chemically altered to improve properties
Antimicrobial spectrum
◦ Range of activity of an antimicrobial against bacteria
◦ “Broad-spectrum” vs “narrow spectrum”
42
BSc N/M CUNIMA
43. Bacteriostatic
◦ When growth of an organsim is inhibited by the antibacterial
Bactericidal (viricidal, fungicidal)
◦ When the organism is killed by the antibacterial
Additive
◦ Combined effect of antibacterials is equal to sum of individual agents
Synergistic
◦ Combined effect is greater than that achieved with addition
Antagonistic
◦ Drugs inhibit the action of each other
43
BSc N/M CUNIMA
46. Most have β-lactam ring
Bactericidal
Action
◦ Interfere with cross-linking of peptidoglycan by inhibiting
carboxypeptidase and transpeptidase reactions which form a link
between N-acetylglucosamine and N-acetylmuramic acid
◦ Cell wall weakened and lysis of microorganism occurs
46
BSc N/M CUNIMA
48. Type of antibiotic derived from Penicillium fungi
Originally discovered by accident in 1928. Alexander Fleming
Given Orally or IM/IV
48
BSc N/M CUNIMA
49. Pharmacokinetics
◦ Wide distribution, mainly renal excretion
Toxicity
◦ Hypersensitivity reactions include anaphylaxis and skin rashes
◦ 10% of pen-allergic also allergic to cephalosporins
Antibacterial resistance
◦ Alteration of target site eg PBP mutation in S. pneumoniae, mecA
of MRSA
◦ β-lactamases
◦ Cell membrane alterations reducing uptake or increasing loss from
the cell
49
BSc N/M CUNIMA
50. Benzylpenicillin (also known as penicillin G (PenG) or BENPEN)
◦ Gram +ve orgs and Gram –ve cocci
◦ Streptococcal infections, gonorrhoea, meningococcal meningitis
Phenoxymethylpenicillin is a narrow spectrum antibiotic also
commonly referred to as Penicillin V or Penicillin VK
Flucloxacillin
◦ Active vs b-lactamase positive strains of staphylococcus
◦ S. aureus infections
Amoxicillin/ampicillin
◦ More active against Enterococcus, Haemophilus and some Gram
–ve aerobes
◦ Urinary and respiratory tract infections
Piperacillin
◦ Wider activity against coliforms and Pseudomonas aeruginosa
◦ Severe Gram –ve infections
50
BSc N/M CUNIMA
51. First generation “narrow spectrum” eg cephradine
Second generation “expanded spectrum” eg cefuroxime
Third generation “broad spectrum” eg ceftriaxone
Fourth generation “extended spectum” eg cefpirome
◦ Same mechanism of action as penicillins, wider spectrum, resistant to many β-
lactamases, improved pharmocokinetics.
Toxicity/SEs
◦ Hypersensitivity with rashes
Resistance
◦ Similar to penicillins
51
BSc N/M CUNIMA
52. Structure
◦ Similar to penicillins
◦ Broad spectrum antimicrobial spectrum of activity
Pharmacokinetics
◦ Given iv once daily, renal excretion
Toxicity/SEs
◦ Hypersensitivity with rashes, !0% cross reactivity with penicillins
Resistance
◦ Hydrolysis by carbapenemases
◦ Reduced uptake by cell
Examples
◦ Imipenem, meropenem, ertapenem
Clinical application
◦ Severe gram –ve sepsis. Neutropenic sepsis
52
BSc N/M CUNIMA
53. Pharmacokinetics
◦ Must be given iv, widely distributed, renal excretion
Mechanism of action
◦ Interact with the terminal of pentapeptide side chains of peptidoglycan and thus
interferes with bridge formation between peptidoglycan chains, cause cell lysis
and death
Only active against Gram positive bacteria. Used to treat infections
caused by oxacillin resistant staphylococci and other gram positive
b-lactam resistant bacteria
Resistance
◦ Intrinsic, plasmid mediated
Examples include: Dalbavancin, oritavancin, ramoplanin teicoplanin,
telavancin, vancomycin
53
BSc N/M CUNIMA
54. Pharmacokinetics
◦ Poor absorption from gut, poor penetration into tissue and fluids
◦ Renal excretion, serum levels should be monitored
Mechanism of action
◦ Bind irreversibly to the 30S ribosomal protein.
Antimicrobial spectrum of activity
◦ Bactericidal, staphylococci and aerobic Gram –ves. Synergy with β-lactams
Toxicity
◦ Hypersensitivity, ototoxicity, nephrotoxicity
Resistance
◦ Mutation of binding site, decreased uptake into cell, increased expulsion from cell,
enzymatic modification of antibiotic
Examples
◦ Amikacin, apramycin, arbekacin, astromicin, bekanamycin, dibekacin,
dihydrostreptomycin, framycetin, gentamicin, isepamicin, kanamycin, micronomicin,
neomycin, netilmicin, paromomycin, ribostamycin, sisomicin, streptoduocin, streptomycin,
tobramycin
Use
◦ Severe sepsis caused by Gram negative bacteria
54
BSc N/M CUNIMA
55. Pharmacokinetics
◦ Absorbed orally, iv, well distributed, excretion in bile
Mechanism of action
◦ Bind to 50S ribosomal RNA unit, predominantly bacteriostatic
Antimicrobial spectrum of activity
◦ Gram positive, Haemophilus, Bordetella, Neisseria, chlamydia, rickettsiae and
mycoplasmas
Toxicity
◦ GI upset, rashes, hepatic damage (rare
Resistance
◦ Alteration of RNA target or drug efflux
Examples
◦ Erythromycin, azithromycin, clarithromycin
Clinical application
◦ Strep and staph soft tissue infections, RTI
55
BSc N/M CUNIMA
56. Pharmacokinetics
◦ Rapidly absorbed after oral administration, good tissue penetration inc. brain,
hepatic metabolism then renal excretion
Mechanism of action
◦ Binds to 50S ribosomal subunit, Bacteriostatic
Antimicrobial spectrum of activity
◦ Wide range of organisms including chlamdiae, mycoplasmas and rickettsiae
Toxicity/SEs
◦ Dose related depressant effect on bone marrow, rarely aplasia, grey baby
syndrome
Resistance
◦ Inactivation by an inducible acetylase enzyme, reduced permeability
Clinical application
◦ Meningitis, typhoid fever
56
BSc N/M CUNIMA
57. Pharmacokinetics
◦ Oral or iv, penetrate well into body fluids. Excretion via kidney and bile duct
Mechanism of action
◦ Bind to 30S ribosomal subunit, bacteriostatic
Antimicrobial spectrum of activity
◦ Broad spectrum: Gram +ve and Gram –ve, chlamydia, rickettsiae and
mycoplasmae
Toxicity/SEs
◦ GI intolerance, deposition in developing bone and teeth, skin rashes
Resistance
◦ Efflux from cell, Decreased penetration, alteration of target site
Examples
◦ Tetracyline, doxycline
Clinical application
◦ Important in treatment of infections by chlamydiae, rickettsiae and mycoplasmae
57
BSc N/M CUNIMA
58. Pharmacokinetics
◦ Generally good absorption after oral administration, penetrates well into body
tissues and fluids, eliminated by renal excretion and liver metabolism
Mechanism of action
◦ Inhibit the action of DNA gyrases which are important in “supercoiling” during
DNA synthesis, Bactericidal
Antimicrobial spectrum of activity
◦ Act against gram –ves inc. Pseudomonas. Not good for streptococci or
anaerobes
Toxicity/SEs
◦ GI disturbances, neurological, ruptured Achilles’ tendon
Resistance
mutations in DNA gyrases, efflux from cell
Examples
◦ ciprofloxacin
Clinical application
◦ Severe sepsis caused by coliforms and other Gram –ve aerobic bacilli
58
BSc N/M CUNIMA
59. Sulphonamides
◦ Act on folic acid synthesis as competitive inhibitor of p-aminobenzoic acid to
inhibit purine and thymidine synthesis. Now limited use because of toxicity and
resistance. Resistance via altered dihydropteroate synthetase enzyme
Trimethoprim (diaminopyrimidine)
◦ Prevention of tetrahydrofolic acid synthesis, resistance via production of different
dihydrofolate reductase enzymes. Broad spectrum, used for UTI and RTIs
Co-trimoxazole ( trimethoprim+ sulphamethoxazole)
◦ Synergistic antibacterial. Used for Pneumocystis jiroveci
59
BSc N/M CUNIMA
60. Pharmacokinetics
◦ Well absorbed orally, widely distributed, metabolized in the liver and excreted via
bile
Mechanism of action
◦ Binds to RNA polymerase and blocks synthesis of mRNA
Antimicrobial spectrum of activity
◦ Active vs staph, strep,neisseria, legionella, mycobacteria. Coliforms
resistant
Toxicity/SEs
◦ Skin rashes, LFT abnormalities, potent inducer of hepatic enzymes interfering
with other drugs eg warfarin
Resistance
◦ Resistant mutants ( change in single amino acid at target site) occur when used
as single drug so often combined with other agents
Clinical application
◦ Tuberculosis (part of triple/quadruple therapy), combination therapy,
chemoprophylaxis fro meningitis due to meningococcus or Hib
60
BSc N/M CUNIMA
61. Pharmacokinetics
◦ Well absorbed orally, per rectum and good tissue distribution
Mechanism of action
◦ Metabolized by nitroreductases to active intermediates which
result in DNA damage
Antimicrobial spectrum of activity
◦ Active against anaerobes, Giardia, Trichomonas and other
parasites
Toxicity
◦ Nausea, metallic taste, rarely peripheral neuropathy
Resistance
◦ Rare but can occur due to decreased uptake
Clinical applications
◦ Treatment of anaerobic infections, giardiasis, amoebiasis
61
BSc N/M CUNIMA
62. Fucidin
◦ Active vs staphylococci, acts on ribosome, rapid resistance if used
alone, can cause hepatic damage, usually used in combination
Nitrofurantoin
◦ Well absorbed, excreted in urine, for uncomplicated UTI
Nalidixic acid
◦ Quinolone, used for simple UTI
Polymixins
◦ Disrupt cell membrane, nephrotoxic, usually topical eg colistin
62
BSc N/M CUNIMA
63. Linezolid (oxazolidinone)
◦ Excellent oral absorption, used in renal failure, inhibits protein
synthesies, acts on Gram positive (MRSA and VRE)
Synercid (quinupristin and dalfopristin)
◦ For VRE
Fluoroquinolones (moxifloxacin, levofloxacin)
◦ Better Gram +ve activity inc. pneumococci
Tigecycline
◦ Use against multi-resistant, non-fermenting Gram –ves eg
Acinetobacter sp
63
BSc N/M CUNIMA
64. Alteration of the target site
◦ Mutation of ribosome, topoisomerase, PBP
Destruction/inactivation of the antibiotic
◦ B-lactamases, AG modifying enzymes
Blockage of transport of the agent into the cell
Metabolic bypass
◦ Eg dihydrofolate reductases
Increased loss of drug from cell (efflux)
Protection of target site by a bacterial protein
64
BSc N/M CUNIMA
65. Via chromosomal mutation and then
duplication during cell division
Plasmids
Transposons “jumping genes”
Bacteriophages
Integrons
65
BSc N/M CUNIMA
66. Prevalence of resistance is directly proportional to the
amount of antibiotic used
Problems
◦ Use of antibiotics without prescriptions
◦ Uncontrolled use of antibiotics in agriculture
◦ Poor prescribing habits
◦ Absence of antibiotic policies
66
BSc N/M CUNIMA
67. antiviral drugs
class of medicines particularly used for the treatment of viral infections
focused on two different approaches
Targeting the viruses themselves or the host cell factors
Antiviral drugs that directly target the viruses include the inhibitors of virus
attachment, inhibitors of virus entry, uncoating inhibitors, polymerase inhibitors,
protease inhibitors, inhibitors of nucleoside and nucleotide reverse transcriptase
and the inhibitors of integrase
The inhibitors of protease (ritonavir, atazanavir and darunavir)
viral DNA polymerase inhibitors: (acyclovir, tenofovir, valganciclovir and
valacyclovir)
Inhibitors of integrase (raltegravir)
67
BSc N/M CUNIMA
68. Drugs with antiviral activities
Ribavirin:After intracellular phosphorylation, ribavirin triphosphate
interferes with the initial timeliness of virus translation
Lamivudine is a prescription nucleoside reverse transcriptase
inhibitor (NRTI) that is used in combination with other drugs as
antiviral treatment for human immunodeficiency virus type-1 (HIV-1)
monotherapy for hepatitis B virus (HBV)
Amantadine and rimantadine: Both drugs appear to suppress
influenza infection replication by blocking the particle channel of the
M2 protein virus
Interferon alpha: shown to be effective in the treatment of diseases
caused by human herpesvirus 8, papillomavirus (Kaposi’s sarcoma)
virus, hepatitis B and C virus 68
BSc N/M CUNIMA
69. Drugs with antiviral activities
Remdesivir: nucleotide analogue metabolised intracellularly to adenosine triphosphate analogue inhibiting the viral
RNA polymerases
acts as an inhibitor of RNA dependant RNA polymerase
has broadspectrum antiviral activity against several virus family members including the coronaviruses for example,
Middle East respiratory syndrome coronavirus (MERSCoC) and SARSCoV, and filoviruses for example, Ebola
Nitazoxanide:
Virus inactivating agents
Inhibitors of enzymes associated with virions
DNA polymerases
RNA polymerases
Viral neuraminidase
69
BSc N/M CUNIMA
73. Nucleoside/Nucleotide Reverse Transcriptase Inhibitors
nucleoside or nucleotide analogs without hydroxyl at the 3’ end that are incorporated into the growing viral
DNA strand
competitively bind to reverse transcriptase and cause premature DNA chain termination as they inhibit 3’ to
5’ phosphodiester bond formation.
Examples include: abacavir, didanosine, lamivudine, stavudine, tenofovir, and zidovudine
Non-nucleoside Reverse Transcriptase Inhibitors (NNRTIs)
bind to HIV reverse transcriptase at an allosteric, hydrophobic site causing a stereochemical change within
reverse transcriptase, thus inhibiting nucleoside binding and inhibition of DNA polymerase.
Examples include delavirdine, efavirenz, nevirapine, and rilpivirine
Protease inhibitors (PIs)
competitively inhibit the proteolytic cleavage of the gag/pol polyproteins in HIV-infected cells. These agents
result in immature, non-infectious virions.
Generally used in patients who fail their initial HAART regimen and should be administered with boosting
agents such as ritonavir or cobicistat.
Examples include atazanavir, darunavir, indinavir
73
BSc N/M CUNIMA
74. Integrase Strand Transfer Inhibitors (INSTIs)
bind viral integrase and prevent viral DNA from being incorporated into the
host cell chromosome.
Examples include: dolutegravir, elvitegravir, raltegravir
Fusion inhibitors (FIs)
bind to the envelope glycoprotein gp41 and prevent viral fusion to the CD4
T-cells.
Examples include enfuvirtide
Chemokine Receptor Antagonists (CCR5 Antagonists)
selectively and reversibly block entry into the CD4 T-cells by preventing
interaction between CD4 cells and the gp120 subunit of the viral envelope
glycoprotein
Example: maraviroc
74
BSc N/M CUNIMA
78. Choice & dose of an antifungal agent
Depends on:
Nature of the condition
Whether there are underlying diseases
Health of a patient
Whether antifungal resistance has been identified
The ideal antifungal agent should target a pathway or
process specific to the fungus
Difficult because fungi are eukaryotic organisms
78
BSc N/M CUNIMA
79. Limitations of antibiotics:
Most have profound side effects
A narrow antifungal spectrum
Poor penetration of certain tissues
Selection of resistant fungi
79
BSc N/M CUNIMA
80. CLASSES OF ANTIFUNGAL AGENTS
1. Polyenes, e.g. amphotericin B, nystatin
2. Azoles, e.g. fluconazole
3. Antimetabolites, e.g. flucytosine
4. Echinocandins, e.g. caspofungin
5. Allylamines, e.g. terbenafine
6. Miscelleanous, e.g. griseofulvin
80
BSc N/M CUNIMA
83. 1. POLYENE: AMPHOTERICIN B
Produced by Streptomyces nodosus
Binds to ergosterol in cell membranes
Alters membrane fluidity
Creating pores that cause cell leakage & eventually death
Binds weakly to cholesterol, causing the toxicity effects in the
mammalian cell
Fungicidal drug
reserved for severe cases of systemic fungal disease
83
BSc N/M CUNIMA
84. POLYENE:
Broad spectrum of activity against
Yeasts e.g. Candida spp, C. neoformans
Moulds e.g. Aspergillus spp
Dimorphic fungi e.g. H. capsulatum, B. dermatitidis
Response to drug is influenced by:
Dose & route of administration
Site of mycotic infection
Immune status of patient
Inherent susceptibility of pathogen
84
BSc N/M CUNIMA
85. 2. THE AZOLES
Have a 5-membered azole ring & divided into:
Imidazoles: have 2N in azole ring
:e.g. ketoconazole, miconazole, clotrimazole
Triazoles: have 3N in azole ring
: e.g. fluconazole, itraconazole, voriconazole
Can be used to treat a wide range of systemic and
localized infections
Fungistatic drugs
85
BSc N/M CUNIMA
86. THE AZOLES CONT’
Interfere with ergosterol biosynthesis
Binds to cytochrome P450-dependent 14 α-demethylation of
lanosterol (precursor of ergosterol)
Results in reduction in the amount of ergosterol which leads to
membrane instability, growth inhibition & cell death in some cases
86
BSc N/M CUNIMA
87. Fluconazole
Triazole compound that is active against
Yeasts e.g. Candida albicans, Crytococcus neoformans
Dimorphic fungi e.g. Histoplasma capsulatum
Ineffective against C. krusei, C. glabrata, Aspergillus spp
Useful to treat mucosal & systemic candidiasis and
cryptococcal meningitis
87
BSc N/M CUNIMA
88. 3. ANTIMETABOLITE: FLUCYTOSINE
Agent: 5-fluorocytosine- a fluorinated derivative of cytosine
(pyrimidine)
Oral antifungal agent
Mode of action
Disrupts protein synthesis by inhibiting DNA synthesis
Mainly used in conjunction with amphotericin B for
treatment of cryptococcus & candidiasis
Many fungi are inherently resistant to flucytosine
88
BSc N/M CUNIMA
89. 4. ECHINOCANDINS
New class of antifungal agent
Synthetically modified lipopeptides
Examples: caspofungin, micafungin, anidulafungin
Perturb synthesis of cell wall polysaccharide β-glucan by
inhibiting 1,3-β-glucan synthase & disrupting the cell wall
Fungicidal
Highly active against Candida spp, Aspergillus spp &
Pneumocystis jiroveci
Inactive against Zygomycetes, C. neoformans
89
BSc N/M CUNIMA
90. 5.ALLYLAMINES: TERBINAFINE
Terbinafine: systemic (oral and topical)
Naftiline: topical
Inhibit squalene epoxidase and thus decrease ergosterol
synthesis
Lipophilic, broad spectrum, few SEs
High concentrations in fatty tissues, skin, hair and nails
90
BSc N/M CUNIMA
91. 6. GRISEOFULVIN
Oral agent used vs dermatophytes
Interacts with microtubules in cell and inhibits mitosis
Often second line agent after terbinafine
Mild SEs
91
BSc N/M CUNIMA
92. Antifungal drug resistance
Primary (intrinsic) - present before exposure
to antifungal
Secondary (acquired) - develops after
exposure to antifungal
92
BSc N/M CUNIMA
94. Secondary antifungal resistance
Predominantly seen with azole (esp. fluconazole) resistance among
Candida spp.
Chronic mucosal candidiasis in AIDS patients esp. low CD4 counts,
multiple azole courses, prolonged heavy azole use (esp.
fluconazole, N.B. cross-resistance with itraconazole)
Bloodstream candidiasis in critically ill or non-AIDS
immunosuppressed patients (1-3% of C. albicans resistant)
94
BSc N/M CUNIMA
95. Prevention
Fungal infections remain serious and
underappreciated causes of illness and death.
Environmental control may be difficult
Observe and practice hygiene
Taking treatment as prescribed
95
BSc N/M CUNIMA
96. Recommended Reading
• Mims Medical Microbiology
– Goering, Dockrell et al 4th edn p37-46
• Medical Microbiology
– Greenwood et al, 17th edn p20-22 and p80-94
96
BSc N/M CUNIMA