Antimicrobial are the drug produced by microorganisms which inhibits or kill other microorganism at very low concentration

1. MICROBIOLOGY
MICROBIOLOGY

2. Microbiology is the study of
microorganisms.
Microorganisms can be classified
into:
1.Eukaryotes
2.Prokaryotes

3. Eukaryotes are microorganisms
containing true intracellular nucleus.
Eg. Fungi, Other Algae, Moulds and
Protozoa
Prokaryotes are microorganisms that
contain nucleic material but lack well
defined membrane bound true nucleus.
e.g. Bacteria, Blue Green Algae

4. Commensal flora
These are the microorganisms that live in our various
body surfaces without causing any harm.
In fact these microorganism benefit us by protecting us
from other pathogenic microorganisms.
In return human being provide them food and shelter.
These are the microbes that live in and on our various
body parts.
Commensals that get into the “wrong” place can do
untold damage.
Urinary tract infections are most frequently caused
when gut organisms or the skin flora gain access to the
bladder.

5. Pathogenic Organisms
These are disease causing organisms.
Bacteria
• They are prokaryotes and have a
simple structures.
• They have a unicellular structure.

6. Bacterial shapes:
Bacteria is classified according to its shape or
appearance.
Cocci - spiral or oval.
Bacilli - rod shaped.
Vibrio – comma shaped curved rods.
Spirilla - rigid spiral shaped.
Spirochetes – flexible spiral forms.
Actinomycetes – branching filamentous like
radiating sun rays with rigid cell wall.
Mycoplasm – no stable morphology i.e. no cell
wall.

9. Characteristic cellular arrangement
Cocci
Pairs- Diplococci
Chains - Streptococci
Four - Tetrads
Eight - Sarcina
Grape like clusters - Staphyloccocci
Bacilli
Chains – Streptobacilli
In pairs- Diplobacillis

12. Bacterial Cell Wall
Bacteria have a cell wall containing a
special polymer called peptidoglycan.
The cell wall lies outside the cell
membrane.
The rigid peptidoglycan is important in
defining the shape of the cell, and gives
the cell strength.

13.  The cell wall of Gram-positive bacteria is
largely made up of peptidoglycan. There may
be up to 40 layers of this polymer, giving
enormous strength to the cell wall.
 The cell envelope of Gram- negative bacteria
is complex. It consist of various lipid layers
like phospholipids, lipoprotein and lipo
polysaccharide.
 One or two layers of peptidoglycan lie beyond
the lipid layer.
 Gram-ve bacteria are thus mechanically much
weaker than Gram+ve ones.

14. Gram Staining
Primary stain –crystal violet
Fixation - Dilute iodine
Decolourisation with organic
solvent: Ethanol, acetone
Safranine or neutral red

15. Cells with many layers of
peptidoglycan can retain a crystal
violet-iodine complex when treated
with acetone.
Hence, Gram-positive bacteria appear
blue-black or purple when stained
using Gram's method.

16. Due to the presence of lipid layers in
Gram-negative bacteria, the crystal
violet is washed away by decolorizing
agent along with the lipid layer.
Hence cannot retain the crystal violet-
iodine complex.
These need counterstaining with another
dye to be seen using Gram's method. A
red dye such as safranine is often used.

17. The Genetic Makeup of Bacteria
The bacterial chromosomal DNA is
located in nucleoid in cytoplasm.
Bacteria is a prokaryote hence does not
have true, membrane bound nucleus.

18. Cell Contents
Cell Wall
Cytoplasmic Membrane
Cytoplasm
Ribosome
Mesosomes
Bacterial Appendages
Flagella
Fimbriae
Pilli
Capsules

20. Cytoplasmic Membrane
A thin membrane layer lining the inner
surface of the cell wall separating it
from the cytoplasm.
Semi permeable membrane which
permits the passage of selected
materials.

21. Cytoplasm
It is a system of variety of organic and
inorganic solutes in a viscous watery
solution.
Absence of endoplasmic reticulum and
mitochondria like the prokaryotes

22. Ribosome
Centre for protein synthesis.
Mesosomes
Principle sites of respiratory enzymes.

23. Bacterial Appendages
Flagella
Flagella
 Responsible for the motility of bacteria
specially in pathogenic bacteria.
 Flagella are inserted through the cell walls
of bacteria.
 At their base can be found wheel-like
structures.

26. Fimbriae
Gram-negative pathogenic bacteria may
be covered in fine hairs called Fimbriae
(singular: fimbria).
These are important in adhesion.
If a microbe is to cause an infection, first
it must attach to its surface.

28. Pilli
 Bacteria have additional structures called Pilli.
 Pilli can attach two bacterial cells together: sex
pilli are necessary for the transfer genetic
materials between bacteria.
 They exchange genetic material in a process of
conjugation that involves cells being joined by
sex pilli, tube-like structures through which
DNA is passed.

29. A viscid material is secreted by the
bacteria around the cell surface
If it is organized into a sharply defined
structure it is called Capsules.
When it a loose secretion, it is called
slime layer.

30. Encapsulated bacteria are highly
resistant to the lytic effect of the
phagocytes and hence are not
susceptible to killing as easily as bacteria
that lack capsules
Slime to help bacteria to stick to
surfaces. Slime is produced by several
types of pathogenic microbes, and is
usually made up from polysaccharides.

31. Bacterial spores
A few species of bacteria have the
ability to produce highly resistant
structures known as endospores (or
simply spores).
These resist a range of hazardous
environment, and protect against heat,
radiation, and desiccation.

32. Diseases caused by sporing bacteria
include
Botulism (Clostridium botulinum),
Gas gangrene (Clostridium perfringens),
Tetanus (Clostridium tetani)
Acute food poisoning (Clostridium
perfringens)

33. Obligate Aerobes
These bacteria have an absolute
requirement for oxygen.
Facultative Anaerobes
These can survive in the absence as
well as the presence of oxygen.
Obligate Anaerobes
These are killed by traces of oxygen

34. Psychrotrophs
Bacteria that grow at very low
temperature.
Thermophiles
Bacteria that are found to grow at
high temperatures.
Mesophiles
Those that grow at moderate
temperatures .

35. Viruses
They entirely rely upon other cells for
their replication.
Viruses are obligate intracellular
parasites which require to live within a
cell in its host.

36. They comprise a nucleic acid core,
(either DNA or RNA but not both)
wrapped in a protein coat.
Some viruses have an envelope, made of
lipid and usually derived from the cell
in which they grow. Other viruses are
naked.
There is a special class of virus that
attacks bacteria - BACTERIOPHAGE.

37. Fungi
All fungi are eukaryotic.
Most possess a rigid cell wall made of
chitin (Insoluble Polysaccharide)
They reproduce both sexually or
asexually.
Multicellular or unicellular.

38. Fungi are heterotrophic.
Saprophytic fungi grow on dead organic
matter.
Parasitic fungi grow on living tissues.

39. Moulds
 Fungi that grow in mats of tiny filaments are
known as hyphae (singular: hypha, Greek for
a thread) or mycelia (singular: mycelium, from
the Greek mukes, meaning a mushroom).
 These may or may not be subdivided into
separate compartments by cross walls known
as septa (singular: septum).
 Moulds are multicellular organisms and are in
some degree related to the mushrooms.

40. Unicellular fungi: the yeasts.
Most familiar of the yeasts is
Saccharomyces cerevisiae. Baker's yeast,
used in the production of leavened bread,
or brewer's yeast, used in alcohol
production
Yeasts grow and multiply by budding
daughter cells off from a mother cell.

41. Moulds cause a variety of common,
superficial infections such as
ringworm and athlete's foot.
The most common yeast infection is
"thrush" caused by Candida albicans.

42. One of the most important of fungi is
Penicillium.
It is from this fungi that penicillins is
derived.
These were the first antibiotics and are
still among the most used antimicrobial
agents world-wide

43. Protozoa
 Protozoa are unicellular eukaryotes.
 Many protozoa are free living, but others
cause serious infections.
 Protozoa can infect any human tissue, and are
the cause of a variety of diseases.
 They spread using a variety of strategies.
 Some produce cysts to survive outside the
body, others are spread by insects, and yet
others spread during human sexual contact.

44. Infections caused by protozoa include
 Amoebic Meningitis
 Malaria by Plasmodium vivax
 Trypanosomiasis
 Leishmaniasis (Kala-Azar)
 Amoebic Dysentery
 Diarrhoa caused by Cryptosporidium
 Vaginal infections may be caused by
Trichomonas vaginalis
 Amoebiasis

45.  A pathogen: This is an organism that is able
to invade the various normal defenses of the
human host to cause infection.
 Infection: This is when an organism enters
the body, increases in number and causes
damage to the host in the process.
Stages of Infection
The incubation period - The time between the exposure to
an agent and the first appearance of clinical symptoms.
Although there are no symptoms, the organism may be
causing substantial damage during this interval.
Prodrome, - where non-specific signs and symptoms such
as headache, fever and lethargy are noted.

46. Clinical Illness - Development of a
specific symptom, typical acute or
chronic, suggestive of a classical
infectious disease such as pneumonia,
diarrhoea.
Period of resolution - the severity of
the symptoms gradually decreases
Convalescence - where the symptoms
have largely gone, but the body is still
recovering.

47. Nosocomial infection: infections
that are transmitted in hospitals.
Some of these may be opportunistic
infections mentioned above
affecting seriously ill patients,
others, for example infections with
Methicillin-Resistant
Staphylococcus aureus (MRSA),
may occur because of the special
nature of the hospital environment.

48. Acute infection:
o Rapid Onset (Hours or days);
o Brief duration (Days or weeks)
o Diptheria
Chronic Infection:
o Prolonged duration (Month or Years)
o Tuberculosis, leprosy

49. Re-infections
 Renewed occurrence of a certain illness
caused by a different type of pathogen from
the first infection. For e.g. a first infection of
the upper urinary tract can be caused by E.
coli and the re-infection by Klebsiella. This is
typical of recurrent urinary tract infections
in females.
 A 'relapse' is a renewed occurrence of a
certain illness caused by the same species of
pathogen as in the first infection. Example of
relapses, when latent infections (whose
pathogens can persist in the body for years
and decades) recur. E.g. viral herpes simplex
infection.

50. Bacteria
Bacteria

51. A)Gram-positive
1) Gram-positive cocci
a) Staphylococci
Staphylococcus aureus. , Staphylococcus albus ,
Staphylococcus epidermidis, Staphylococcus
capitis, Staphylococcus saprophyticus.
b) Streptococci
a-haemolytic - Streptococcus pneumoniae.
b-haemolytic streptococci - Streptococcus
pyogenes.
Enterococci - Enterococcus faecalis ,
Enterococcus faecium.

52. 2) Gram-positive Bacilli
a) Bacillus
Bacillus anthracis - the cause of anthrax.
Bacillus cereus - a cause of food poisoning.
b) Clostridia
Clostridium perfringens or Clostridium welchii
–a principal cause of gangrene, Clostridium
tetani, the cause of tetanus, Clostridium
botulinum – the cause of the fatal food
poisoning – botulism.
c) Other Gram-positive bacilli
Listeria monocytogenes , Corynebacterium
diphtheriae , Propionibacterium acnes,
associated with acne.

53. 3) Mycobacteria
Mycobacterium tuberculosis
Mycobacterium leprae
B) Gram-negative
1) Gram-negative cocci
Neisseria meningitides is an important cause of bacterial
meningitis, Neisseria gonorrhoeae causes gonorrhoea.
2) Gram-negative bacilli
a) Enterobacteriaceae – Escherichia coli , Klebsiella,
salmonellas , shigellas and proteeae Yersinia pestis,
the cause of plague, Salmonella typhi, the cause of
typhoid, Shigella dysenteriae, the cause of bacilliary
dysentery, and Salmonella enteritidis implicated in
many cases of food poisoning.

54. b) Pseudomonads
Pseudomonas aeruginosa - wound infections
c) Curved Gram-negative rods
Vibrio cholerae- causes cholera, a
waterborne infection., Campylobacters,
Helicobacter pylori.
d) Others
Moraxella, Acinetobacter, Legionella,
Bordetella , .Bordetella pertussis, - the cause
of whooping cough, Haemophilus,
Haemophilus influenzae , Haemophilus ,
bacteroides.

55. Antimicrobial
Antimicrobial
Agents
Agents

56.  Chemotherapy:
The treatment of disease by means of chemicals that have a
specific toxic effect upon the disease-producing
microorganisms or that selectively destroy cancerous
tissue
 Antimicrobial Agents:
Are those agents which are produced naturally, synthetically
or semisynthetically and are active against
microorganisms are called antimicrobial agent.
 Antibiotics:
Substances produced by some microorganisms which
inhibits the growth of or kill other microorganisms
selectively at very low concentrations.
 Antibacterials refer to substances that act against bacteria

57. Chemotherapy
Chemotherapy
 Chemo-chemical
 Therapy-treatment
 The treatment of systemic infections is done
using specific chemical agents or drugs
(Chemotherapeutic agents) that selectively
suppress the infecting micro-organism
without significantly affecting the host.
e. g. : Drugs used in Cancer Treatment
5-Fluorouracil(5-FU),Vinblastine

58. Antibiotic
 Substances produced by microorganism
which suppresses the growth and kill the
other microorganism , usually at very low
concentrations.
 Eg: (Cefixime is derived from
Cephalosporin C which is obtained from
fungus Cephalosporium
Cephalosporium)

59. These chemicals are not included
as antimicrobials because they
are needed in high concentration:
*Ethanol
*Lactic Acid,
*H2
O2

60. Classifications
Classifications
• Chemical Structure
• Mechanism of Action
• Type of organism they are primarily
active against
• Spectrum of Activity
• Type of Action
• Antibiotic obtained from

61. Chemical Structure
1) Sulfonamides and related drugs:
– Sulfadoxine, Sulfamethoxazole
2) Diaminopyrimidine :
– Trimethoprim, Pyremethamine
3) Quinolones:
– Nalidixic Acid, Fluroquinolones
(Ciprofloxacin, Norfloxacin, Ofloxacin)
4) β-Lactam antibiotics:
– Penicillin (Ampicillin, Cloxacillin,Amoxycillin),
Cephalosporins (Cephalexin , Cefadroxyl,
Cefaclor, Cefixime)

62. 5) Tetracycline: Oxytetracycline, Doxycycline
6) Nitrobenzene derivative: Chloramphenicol
7) Aminoglycoside: Streptomycin, Gentamicin,
Neomycin
8) Macrolide antibiotics: Erythromycin,
Roxithromycin, Azithromycin
9) Polypeptide antibiotics: Bacitracin,
Polymixin-B

63. 10) Nitrofuran antibiotics: Nitrofurantoin
11) Nitroimidazoles: Metronidazole, Tinidazole,
Albendazole (Benzimidazole )
12) Nicotinic acid derivatives: Isoniazid,
Pyrazinamide, Ethionamide
13)Polyene antibiotics: Nystatin, Amphotericin- B
14) Imidazole derivatives: Fluconazole,
Ketoconazole
15) Others: Rifampicin, Vancomycin, Ethambutol,
Griseofulvin

64. Mechanism of Action
 Inhibit cell wall synthesis: Penicillins
Cephalosporins
 Cause leakage from the cells membrane :
Polymixins, Amphotericin-B
 Inhibit protein synthesis: Tetracyclines,
Erythromycin, Azithro
 Cause misreading of mRNA code and affect
permeability : Aminoglycosides
 Inhibit DNA Gyrase: Fluroquinolones

65.  Interfere with DNA function: Rifampicin,
Metronidazole
 Interfere with DNA synthesis: Acyclovir,
Zidovudin
 Interfere with Intermediatory metabolism:
Sulfonamides, Sulphadoxine, Trimethoprim,
Pyremethamine, Ethambutol
.
Mechanism of Action cont..

66. Type of organisms they are
primarily active against
 ANTIBACTERIAL: They are active against bacteria
 Penicillins
 Aminoglycosides,
 Fluroquinolones
 Cephalosporins

67.  ANTIFUNGAL: They are active against fungi.
Griseofulvin
Ketoconazole, Fluconazole
 ANTIVIRAL: Zidovudin, Acyclovir
 ANTIPROTOZOAL: Pyremethamine, Metronidazole,
Diloxanide
 ANTHELMINTIC: Mebendazole, Pyrantel
Type of organisms they are primarily
active against cont..

68. Spectrum of Activity
Spectrum of Activity
Narrow Spectrum:
Penicillin G, Streptomycin, Erythromycin.
Broad Spectrum:
Tetracycline, Chloramphenicol
Extended Spectrum:
Extended Spectrum Penicillin G

69. Type of Action
Type of Action
Primarily Bacteriostatic:
Stasis - fixed, no further movement or growth
Inhibit the growth of bacteria but do not kill
bacteria.
Sulfonamides, Tetracycline, Chloramphenicol
Primarily Bactericidal:
Cide – kill
Kill bacteria.
Penicillins, Cephalosporins, Nalidixic Acid,
Ciprofloxacin, Cotrimoxazole

70. Antibiotics Obtained From
 Fungi: Penicillin, Cephalosporin
 Bacteria: Bacitracin, Polymixin B
 Actinomycetes: Aminoglycosides,
Macrolides, Chloramphenicol

71. Failure of Antimicrobial Therapy???
 Improper selection of Drug, dose, route or
duration of treatment
 Treatment begun too late
 Failure to take necessary adjuvant measures:
E.g.: Adjustment of urinary pH in case of UTI

72.  Infecting organism present behind barriers
 Trying to treat untreatable infection or
other cause of fever (malignancy)
 Presence of resistant dormant or altered
organism, which later give rise to a
relapse.

73. Antimicrobial Resistance
Antimicrobial Resistance
UNRESPONSIVENESS OF A
UNRESPONSIVENESS OF A
MICRO-ORGANISM TO AMA
MICRO-ORGANISM TO AMA
Natural
Natural Acquired
Acquired
Drug Resistance
Drug Resistance

74. NATURAL:
Lack Of Metabolic Process Or Target
Site
Does Not Pose Clinical Problems
ACQUIRED :
Development of resistance by an
organism (which was sensitive before)
due to use of an AMA over a period of
time.

75. ACQUIRED
. Depends upon the microorganism as well the drug.
. Some bacteria are notorious for rapid acquisition of
resistance, e.g. Staphylococci, Coliform, Tubercle bacilli,
Gonococci.
. But other like Strep. pyogenes ans Spirochetes have not
significant resistance to penicillin despite of its wide use
for more than 40 years.
Mutation
Mutation Genes transfer
Genes transfer Cross resistance
Cross resistance

76. GENES TRANSFER: ( infectious resistance)
from one organism to another can occur by:
 Conjugation: through the formation of bridge (sex
pilus) e.g. Gram negative bacilli of the same or another
species.
 This may be due to chromosomal or extra
chromosomal (plasmid) DNA. This is very important of
clinical problem.
 E.g.. Chloramphenicol to Typhoid bacilli
 Streptomycin to E. coli, Penicillin to Gonococcal

77. Transduction: Transfer of gene
carrying resistance through the
agency of bacteriophage. “R” factor
is taken up by the phage and
delivered to another bacteria which
it infects. E.g. Penicillin,
erythromycin and chloramphenicol.

78. TRANSFORMATION:
May release resistance carrying
DNA into medium and this may be
imbeded by another sensitive
organism and become unresponsive
to the drug.
It is not of clinical significance.

79. BY TRANSFER METHOD, RESISTANT
ORGANISM CAN BE:
 Drug tolerant: loss of affinity of the target
 Drug destroying: Enzyme inactivate the
drug. E.g. Beta lactamases produced by
Staphylococcus,
 Drug impermeable: Disturbance in the
transport mechanism.

80. CROSS RESISTANCE
Acquisition of resistance of one AMA
conferring resistance to another AMA,
to which the organism has not been
exposed. More commonly in chemically
or mechanistically related drug.
E.g. Resistance to one Sulfonamide
means resistance to all other.

81. PREVENTION OF RESISTANCE
1. No indiscriminate and inadequate or unduly
prolonged use of AMAs.
2 Prefer rapidly acting and selective (narrow) AMA.
Broad spectrum – when specific cannot be
determined.
3 Use combination of AMAs wherever prolonged
therapy is undertaken. E.g.. Tuberculosis, Sub Acute
Bacterial Endocarditis
Notorious organism( Staph. aureus, E.coli, M.
tuberculosis, proteus etc) must be treated intensively.

82. Natural Resistance
They may lack a target for the antibiotic:
Chlamydiae do not have peptidoglycan
and are not susceptible to the action of
penicillins.

83. The antibiotic target may be inaccessible:
Peptidoglycan in Gram-negative bacteria
is inaccessible to penicillins that cannot
penetrate the Gram-negative outer
membrane.
Efflux pumps can actively pump out
antibiotics from cells. Gram-negative
bacteria resist the activity of tetracyclines
by this important mechanism.

84. The antibiotic target may be modified
to prevent the action of the drug
 Trimethoprim resistance is manifested
by alterations in the DHFR target
enzyme
 Quinolone resistance is affected by
point mutations in the DNA gyrase,
which prevent binding of the drug to its
target.

85.  The antibiotic may be chemically modified or
destroyed
 Important examples include the huge range of β-
lactamases and the various aminoglycosides-
modifying enzymes.
 Chloramphenicol resistance is most often
manifested by acetylation by the
chloramphenicol acetyl transferase enzyme

86.  Bacteria may elaborate alternative
pathways, avoiding the drug target
Methicillin resistance in methicillin-
resistant Staphylococcus aureus results
from the production of an additional
penicillin binding protein: PBP2, which
is not susceptible to inhibition by
penicillins.

87. THANK YOU