Microbiology with diseases by body system;

1. Control of microbial growth
Environment and human body
 Public health standards
 Health care facilities
 Laboratories
 Home

2. Terminology of Microbial Control
 Sepsis refers to microbial contamination
 Asepsis/Aseptic is an environment or procedure free of
contamination – specifically, absence of pathogens
 Aseptic surgery techniques prevent microbial
contamination of wounds
 Degerming is the mechanical removal of microbes by
scrubbing/swabbing
 A nurse prepares an area of skin for an injection

3.  Sterilization is the removal and destruction of all microbes
 Commercial sterilization
 Killing Clostridium botulinum endospores
 Disinfection is the use of chemicals or physical agents to kill or
inhibit the growth of microbes, specifically pathogens
 Disinfectants are used to treat inanimate objects or surfaces
 Antisepsis is the use of chemicals on skin or other tissue
 The chemicals used are called antiseptics
Terminology of Microbial Control

4. Terminology of Microbial Control
 Sanitization
 Disinfection of places or things used by the public to
meet accepted public health standards
 Pasteurization
 Heat is applied to
 Kill pathogens
 Reduce the number of microorganisms that can
cause spoilage of food and beverages

5. Methods For Controlling Microbial Growth
There are three major methods for controlling microbial growth
 Physical
 Mechanical
 Chemical

6.  Achieved with steam under
pressure (autoclave)
 A temperature of 121C (15psi
of pressure) will kill all microbes
and their endospores in 15 min
 Not prions
 Time must be adjusted
according to the type of
material properly placed in the
autoclave
Sterilization requires T above
that of boiling water
Physical Methods to Control Microbial Growth

7. Pasteurization
Process Treatment (Milk)
Historical pasteurization 63C for 30 minutes
High temperature short time (HTST) - pasteurization 72C for 15 seconds
Ultra high temperature (UHT) - pasteurization 135C for 1 second
 Pasteurization
 Kills pathogens
 Lowers total bacterial counts
 Heat resistant bacteria survive pasteurization
 Unlikely to cause disease or refrigerated products to spoil
Physical Methods to Control Microbial Growth

8.  Ionizing radiation
 X rays and Gamma rays
 Cause damages to DNA (Mutations)
 Nonionizing radiation
 UV, 260 nm
 Cause damages to DNA (Thymine dimers)
Physical Methods to Control Microbial Growth

9. Non-irradiated and Irradiated food with low-level
ionizing radiations
 Ionizing radiation is used to
sterilize
 pharmaceuticals
 plastic syringes
 surgical gloves
 catheters
 UV lamps are commonly found in hospital rooms, nurseries,
operating rooms (tables) or microbial laboratories (safety
cabinets)

10.  Filtration
 To sterilize heat-sensitive
materials
 Culture media,
drugs, vitamins, enzymes,
antibiotic solutions or vaccines
Mechanical Methods For Controlling Microbial Growth

12. Chemical methods to control the growth of
microbes on living tissue and inanimate objects

13. An ideal antimicrobial agent!!
 Antimicrobial agents should be
 Inexpensive
 Fast-acting
 Stable during storage (chemicals)
 Control growth and reproduction of every type of microbe
 Harmless to humans, animals, and objects
 However, every antimicrobial agent has limitations, advantages
and disadvantages

14. Terminology of Microbial Control
 -stasis/-static: inhibits microbial metabolism and growth but does
not kill microbes
 -cide/-cidal: destroys or permanently inactivates (kill) microbes
- stasis/static - cide/-cidal
Bacteriostatic Bactericide
Fungistatic Fungicide
Virustatic Virucide
Germicides: antimicrobial agents that kill microbes including
pathogens
 Microbial death - permanent loss of reproductive capability is the
accepted definition of microbial death

15.  Effectiveness of antimicrobial chemical agents depends on
 Numbers of microbial cells
 Exposure time – accessibility* and type of microbe**)
 Concentration of the antimicrobial agent
 Temperature and pH
 *Environment
 Many pathogens are associated with organic
materials
 Blood, saliva, vomit, or fecal material
 Can interfere or inhibit accessibility of the
antimicrobial agent
Factors that affect choice and effectiveness of
antimicrobial agents

16. Factors that affect choice and effectiveness of
antimicrobial agents
 At least three factors
must be considered
 Site to be treated
 **Susceptibility of
microorganisms involved
 Environmental
conditions
(contaminating organic
materials, T/pH)

17. Evaluate effectiveness of antimicrobial
chemical agents
 Several methods are used including
 Phenol coefficient (phenol was used as an antiseptic by J. Lister
in 1867)
 Disk-diffusion method

18. Iodine (Halogens)
 Tinctures: solution of antimicrobial agent in alcohol
 Iodophors: organic compound (containing iodine) that slowly
releases it
 Betadine
(Iodophor)
 Antiseptic used in preparation
for surgery on a hand

19.  Pure alcohol is
not an effective
antimicrobial
agent
 Requires water
to denature
proteins
 Isopropanol
 Ethanol
Alcohols

20. Disk-diffusion test with Zephiran (quat) against
Mycobacterium
 Effect of
concentration of the
antimicrobial
 Another example of quat is Cepacol (mouthwash)

21. Heavy Metals are bacteriostatic and fungistatic agents
 Silver, mercury, copper,
zinc, and arsenic
 Oligodynamic action
 Denature proteins
 Silver sulfadiazine is used
as a topical cream on
burns
 Silver nitrate was used to
prevent blindness caused
by Neisseria gonorrhoeae
in newborns

23.  The simple act of washing your hands can inhibit the spread of
pathogens in health care facilities (i.e., hospitals!!!)
 The effectiveness of hand washing depends on:
 Type of soap used
 Time taken
 Hospitals use germicidal soaps because they are very
effective at preventing transmission of pathogen
associated with nosocomial infections
 Household soaps can be effective if enough time is taken
to wash your hands thoroughly
HAND WASHING

24. Introduction to antimicrobial drugs
 Spectrum of action
 Narrow-spectrum versus broad-spectrum antimicrobials
 Selective toxicity of antimicrobials
 Targeting the pathogen and not the host cells!!!

25. Antibiotics
 Antibiotic: a substance produced by certain microorganisms that
in small amount inhibits the growth of another microorganism

26. Administration of antibiotics and side effects
 External infections
 Topical or local administration
 Internal infections
 Oral
 Intramuscular (IM) – hypodermic needle
 Intravenous (IV) – needle or catheter
 Factors to keep into consideration include
 Allergies
 Dosage and toxicity
 Disruption of the normal microbiota

27. Cellular targets of antibiotics
 Antimicrobial drugs are either bactericidal or bacteriostatic

28. Inhibition of synthesis of bacterial cell wall by
penicillin

29. Natural and semisynthetic penicillins
Chemical modification of
the side group of the b-
lactam ring can change
 Susceptibility of the
antibiotic to enzymes
called b-lactamases
 Spectrum of activity of
the antibiotic

30. Resistance to antibiotics
 MRSA (Methicillin resistant Staphylococcus aureus)
 Health care-associated MRSA
 Community-associated MRSA
 The widespread use of vancomycin to treat S. aureus infections
has led to the appearance of
 VRE (Vancomycin resistant enterococci)
 Opportunistic Gram positive pathogens
 Cause problems particularly in hospital settings
 Strains of S. aureus have become resistant to vancomycin
(VISA/VRSA) as well!!
 MDR-TB and XDR-TB (Mycobacterium tuberculosis)

31. Resistance to antibiotics  Bacteria become
resistant to antibiotics through
mutations or genetic exchange

32. Resistance to antibiotics
The therapeutic life span of a drug is based on how quickly
resistance develops
Important factors that contribute to resistance
 Overuse of antibiotics (the more an antibiotic is used, the
more quickly resistance occurs)
 Patients should always complete the full regimen of their
antibiotic prescription

33. Resistance to antibiotics
The therapeutic life span of a drug is based on how quickly
resistance develops
Important factors that contribute to resistance
 Hospitals and nursing homes (multiple resistance and cross
resistance)
 Broad-spectrum antimicrobials increase the chance that the
antibiotic will cause resistance among the patient’s normal
flora

34. Testing for susceptibility to antibiotics
 To treat infectious diseases, physicians must know which antibiotic
is most effective against a given pathogen
 Kirby-Bauer Test (disk-diffusion method)
 Compares the relative
effectiveness of different
antibiotics
 Based on the size of the
inhibition zones, organisms
are classified as:
 Susceptible
 Intermediate
 Resistant

35. Synergism or antagonism
 Synergism occurs
when the effect of
two drugs together
is greater than the
effect of either
alone
 Antagonism
occurs when the
effect of two drugs
together is less than
the effect of either
alone
 The combination has a broader
spectrum of action and reduces the
emergence of resistant strains

36. Testing for susceptibility to antibiotics
The E test is a more advanced diffusion method and it allows to
calculate the minimum inhibitory concentration (MIC)
 The plastic-coated strip contains an increasing concentration gradient of
the antibiotic. The MIC can be read from the scale printed on each strip

37. Determining the MIC using the broth dilution test
 The broth dilution test allows determination of the minimum
bactericidal concentration (MBC)