1. MICROBIOLOGY FOR
MEDICAL GRADUATES
WHAT YOU SHOULD KNOW
Dr.T.V.Rao MD
DR.T.V.RAO MD 11/16/2012 1
2. AIMS FOR LEARNING MEDICAL
MICROBIOLOGY
• What is medical microbiology?
• Why is it relevant?
• Some important concepts.
• Basic classification of organisms.
• Classifying bacteria.
DR.T.V.RAO MD 11/16/2012 2
3. WHAT IS MEDICAL MICROBIOLOGY?
The study of microorganisms
“
(including bacteria, viruses, fungi
and parasites) which are of
medical importance and are
capable of causing diseases in
human beings”
DR.T.V.RAO MD 11/16/2012 3
4. THE EARLY YEARS OF MICROBIOLOGY
CONTRIBUTED BY DISCOVERY OF MICROSCOPE
DR.T.V.RAO MD 11/16/2012 4
5. THE FIRST OBSERVATIONS
• 1673-1723, Antoni
van Leeuwenhoek
described live
microorganisms that
he observed in
teeth scrapings, rain
water, and
peppercorn
infusions.
DR.T.V.RAO MD 11/16/2012 5
Figure 1.2b
6. THE EARLY YEARS OF
MICROBIOLOGY
• How Can Microbes Be Classified?
• Carolus Linnaeus (Swedish) developed taxonomic system for
naming plants and animals and grouping similar organisms
together
• Leeuwenhoek’s microorganisms grouped into six categories as
follows:
• Fungi
• Protozoa
• Algae
• Bacteria
• Archaea
• Small animals
DR.T.V.RAO MD 11/16/2012 6
7. WHAT IS MEDICAL MICROBIOLOGY?
THE PURPOSE OF LEARNING
What organisms cause
infection?
How they cause infection.
How to treat them.
How to prevent infection.
DR.T.V.RAO MD 11/16/2012 7
8. WHY IS IT IMPORTANT?
• Infection is one of the most important
causes of mortality and morbidity in the
population.
• Approximately 30% of hospital patients
are on antibiotics at any one time
• 1 in 10 patients acquires an infection
whilst in hospital.
DR.T.V.RAO MD 11/16/2012 8
9. THE HISTORICAL CONTRIBUTION IN THE
SUBJECT OF MICROBIOLOGY BY …
Darwin
• Linnaeus •
• Salk
• Jenner • Watson & Crick
• Jacob and Monod
• Hooke • McClintock
Woese
• Leeuwenhoek •
• Venter?
• Lister
• Pasteur
• Koch
DR.T.V.RAO MD 11/16/2012 9
10. DEFINITIONS
• Bacteriology is the study of bacteria.
• Mycology is the study of fungi.
• Parasitology is the study of protozoa and parasitic worms.
• Recent advances in genomics, the study of an organism’s
genes, have provided new tools for classifying
microorganisms.
• Proteomics is looking at the gene products
DR.T.V.RAO MD 11/16/2012 10
11. LEARN THE CLASSIFICATION OF
ORGANISMS
• All living organisms are classified into:
• Kingdom
• Phylum (family)
• Genus
• Species
• Organisms that can cause disease are many and varied and include:
• Viruses
• Bacteria
• Fungi
• Parasites
DR.T.V.RAO MD 11/16/2012 11
12. RELEVANCE OF CLASSIFICATION
• Different:
• Diseases
• Modes of
transmission
• Treatment-e.g.
routinely use
antibiotics don’t cure
vira lfungalinfections
DR.T.V.RAO MD 11/16/2012 12
13. THE GOLDEN AGE OF MICROBIOLOGY
LOUIS PASTEUR CHANGES THE FUTURE OF
MICROBIOLOGY
DR.T.V.RAO MD 11/16/2012 13
14. FERMENTATION AND PASTEURIZATION
• Pasteur demonstrated that
these spoilage bacteria could
be killed by heat that was not
hot enough to evaporate the
alcohol in wine.
• Pasteurization is the
application of a high heat for a
short time.
DR.T.V.RAO MD 11/16/2012 14
Figure 1.4 (1 of 3)
15. THE GOLDEN AGE OF MICROBIOLOGY
DR.T.V.RAO MD 11/16/2012 15
16. THE GOLDEN AGE OF MICROBIOLOGY
• Koch’s Postulates
• Suspected causative agent must be found in
every case of the disease and be absent from
healthy hosts
• Agent must be isolated and grown outside the
host
• When agent is introduced into a healthy,
susceptible host, the host must get the disease
• Same agent must be reisolated from now-
diseased experimental host
DR.T.V.RAO MD 11/16/2012 16
17. NORMAL MICROBIOTA
• Normal Microbiota prevent growth of
pathogens.
• Normal Microbiota produce growth factors
such as folic acid and vitamin K.
• Resistance is the ability of the body to
ward off disease.
• Resistance factors include skin,
stomach acid, and antimicrobial
chemicals.
• Biofilms are extremely important in
microbial ecology
DR.T.V.RAO MD 11/16/2012 17
18. NORMAL MICRO BIOTA ON THE HUMAN BODY
DR.T.V.RAO MD 11/16/2012
Table 18
14.1
19. NORMAL MICROBIOTA
• Animals, including humans, are usually germfree
in utero.
• Microorganisms begin colonization in and on the
surface of the body soon after birth.
• Microorganisms that establish permanent colonies
inside or on the body without producing disease
make up the normal microbiota.
• Transient microbiota are microbes that are
present for various periods and then
disappear.
DR.T.V.RAO MD 11/16/2012 19
20. WE HAVE MORE MICROBES OCCUPYING OUR BODY
THAN OUR OWN CELLS
DR.T.V.RAO MD 11/16/2012 20
21. CLASSIFYING BACTERIA
Why bother?
Different bacteria:
• cause different diseases
• are susceptible/resistant to
different antibiotics
• some bacteria are common
normal flora whilst other
closely related species are
pathogens
DR.T.V.RAO MD 11/16/2012 21
22. CLASSIFYING BACTERIA
How?
• 1st into broad groups based
on microscopic appearance
• Then divided into species
based on a range of
different properties-often
biochemical reactions e.g.
some may be able to
metabolise a sugar that
others cannot.
DR.T.V.RAO MD 11/16/2012 22
23. GRAM STAIN
Method of differentiating bacteria.
Can be either Gram +ve or Gram –
ve depending on how they
appear with the stain.
Can then be further grouped based
on shape (rod=long thin or
coccus=round).
Thus we end up with 4
combinations:
G+ rod, G+ coccus, G- rod, G-
coccus
DR.T.V.RAO MD 11/16/2012 23
25. GRAM STAIN
G+ve G-ve
• STAIN the slide with
crystal violet for 1-2 min.
• Flood slide with Gram's
iodine for 1-2 min.
• Decolourise by washing
the slide briefly with
acetone (2-3 seconds).
• Stain with safranin
counterstain for 2 min.
• View under microscope
DR.T.V.RAO MD 11/16/2012 25
26. GRAM STAIN
Gives an initial idea of the
possible identity of the
organism.
Can be done without growing
the organism (i.e. rapid
result)
Thus can be done on pus, joint
fluid, sputum, CSF
1st result available on blood
cultures
DR.T.V.RAO MD 11/16/2012 26
27. GRAM STAIN
Relevance of Gram reaction.
• Gram +ve and gram –ve
organisms ae susceptible
to different groups of
antibiotics.
• Cause different diseases
• Differ in their ability to
survive in the environment-
cleaning, infection control,
outbreak management.
DR.T.V.RAO MD 11/16/2012 27
28. GRAM POSITIVE COCCI
• Clusters: usually
characteristic of
Staphylococcus spp., such as
S. aureus
• Chain or pairs: usually characteristic
of Streptococcus spp., such as
S. pneumoniae
DR.T.V.RAO MD 11/16/2012 28
29. GRAM POSITIVE BACILLI
• Thick : usually
characteristic of
Clostridium spp., such
as C. perfringens, C.
difficle, C. tetani
• Thin: e.g. Listeria spp.
DR.T.V.RAO MD 11/16/2012 29
30. GRAM NEGATIVE BACILLI
• Thin rods: usually
characteristic of
enterobacteriaceae
(coliforms), such as E. Coli
• Coccobacilli: usually
characteristic of
Haemophilus spp., such as
H. influenzae
DR.T.V.RAO MD 11/16/2012 30
31. GRAM NEGATIVE BACILLI
• Curved: usually
characteristic of Vibrio
spp.or Campylobacter spp.,
such as V. cholerae C. jejuni
• Thin needle shape: usually
characteristic of
Fusobacterium spp.
DR.T.V.RAO MD 11/16/2012 31
32. GRAM NEGATIVE COCCI
• Diplococci: usually characteristic of
Neisseria spp., such as N.
meningitides or N. gonorrhea.
Though In addition, Moraxella spp.
and Acinetobacter spp.are often
diplococcal in morphology.
• Coccobacilli: usually characteristic
of Acinetobacter spp., which can be
either Gram-positive or Gram-
negative, and is often called Gram-
variable.
DR.T.V.RAO MD 11/16/2012 32
33. WHAT CAN YOU SEE ON THE SLIDE?
1. Gram +ve cocci
2. Gram +ve bacilli
3. Gram –ve cocci
4. Gram –ve bacilli
53%
47%
0% 0%
Staphylococcus aureus – 100x
i
lli
lli
i
cc
cc
ci
ci
co
co
ba
ba
e
e
e
e
+v
–v
+v
–v
m
m
m
m
ra
ra
ra
ra
G
G
G
G
DR.T.V.RAO MD 11/16/2012 33
34. WHAT CAN YOU SEE ON THE SLIDE?
1. Gram +ve cocci
2. Gram +ve bacilli Streptococcus pneumoniae
3. Gram –ve cocci
4. Gram –ve bacilli
68%
16%
11%
5%
i
lli
lli
i
cc
cc
ci
ci
co
co
ba
ba
e
e
e
e
+v
–v
+v
–v
m
m
m
m
ra
ra
ra
ra
G
G
G
G
DR.T.V.RAO MD 11/16/2012 34
35. WHAT CAN YOU SEE ON THE SLIDE?
1. Gram +ve cocci
2. Gram +ve bacilli
3. Gram –ve cocci
4. Gram –ve bacilli
36% 36%
14% 14%
Pseudomonas aeruginosa
i
lli
lli
i
cc
cc
ci
ci
co
co
ba
ba
e
e
e
e
+v
–v
+v
–v
m
m
m
m
ra
ra
ra
ra
G
G
G
G
DR.T.V.RAO MD 11/16/2012 35
36. VIRUSES
Small (50-300nm)
Unable to replicate
independently
Invade host cells and use
their cellular machinery to
replicate
Influenza, Chickenpox
(varicella), Herpes,
Rhinovirus, HIV/AIDS
Often difficult to treat
DR.T.V.RAO MD 11/16/2012 36
37. FUNGI
• Complex, large organisms
• Eukaryotes (as are humans!)
• Divided into yeasts & moulds
• Cause a range of diseases
e.g.:
• Thrush
• Athletes foot
• Invasive & allergic aspergillosis
• Many diseases are
opportunistic.
DR.T.V.RAO MD 11/16/2012 37
38. PROTOZOA
• Eukaryotes
• Absorb or ingest
organic chemicals
• May be motile via
pseudopods, cilia,
or flagella
DR.T.V.RAO MD 11/16/2012 38
Figure 1.1c
39. MULTICELLULAR ANIMAL
PARASITES
• Eukaryote
• Multicellular animals
• Parasitic flatworms and round worms are called Helminths.
• Microscopic stages in life cycles.
DR.T.V.RAO MD 11/16/2012 39
Figure 12.28a
40. THE ETIOLOGY OF INFECTIOUS DISEASES
• Koch’s postulates are criteria for establishing that
specific microbes cause specific diseases.
• Koch’s postulates have the following requirements:
(a) the same pathogen must be present in every case of
the disease;
(b) the pathogen must be isolated in pure culture;
(c) the pathogen isolated from pure culture must cause the
same disease in a healthy, susceptible laboratory
animal;
(d) the pathogen must be reisolated from the inoculated
laboratory animal.
DR.T.V.RAO MD 11/16/2012 40
42. EXCEPTIONS TO KOCH’S POSTULATES
• Koch’s postulates are modified to establish etiologies of
diseases caused by viruses and some bacteria, which cannot
be grown on artificial media.
• Some diseases, such as tetanus, have unequivocal signs
and symptoms.
• Some diseases, such as pneumonia and nephritis, may be
caused by a variety of microbes.
• Some pathogens, such as S. pyrogenes, cause several
different diseases.
• Certain pathogens, such as HIV, cause disease in humans
only.
DR.T.V.RAO MD 11/16/2012 42
43. Diseases and Infections
• Disease-causing microorganisms are
called pathogens.
• Pathogenic microorganisms have special
properties that allow them to invade the
human body or produce toxins.
• When a microorganism overcomes the
body’s defenses, a state of disease
results.
DR.T.V.RAO MD 11/16/2012 43
44. PATHOLOGY, INFECTION, AND DISEASE
• Pathology is the scientific study of disease.
• Pathology is concerned with the
• etiology (cause),
• pathogenesis (development),
• effects of disease – structural and functional changes brought
about by disease.
• Infection is the invasion and growth of pathogens in the body.
• A host is an organism that shelters and supports the growth of
pathogens.
• Disease is an abnormal state in which part or all of the body is not
properly adjusted or is incapable of performing normal functions.
• Infection disease – presence of particular microorganism in part of
the body where is not usually found.
DR.T.V.RAO MD 11/16/2012 44
46. CLASSIFYING INFECTIOUS DISEASES
• Every disease alters body structures and functions
• A patient may exhibit
• symptoms (subjective changes in body functions)
• Pain or body discomfort
• signs (measurable changes), which a physician uses to
make a diagnosis (identification of the disease)
• Fever, swelling, paralysis
• A specific group of symptoms or signs that always
accompanies a specific disease is called a
syndrome.
DR.T.V.RAO MD 11/16/2012 46
48. CLASSIFYING INFECTIOUS DISEASES
• Communicable diseases are transmitted directly
or indirectly from one host to another.
• Chicken pox, genital herpes,
• A contagious disease is one that is easily
spread from one person to another.
• Noncommunicable diseases are caused by
microorganisms that normally grow outside the
human body and are not transmitted from one
host to another
• Tetanus, Clostridium tetani
DR.T.V.RAO MD 11/16/2012 48
49. THE MODERN AGE OF MICROBIOLOGY
DR.T.V.RAO MD 11/16/2012 49
50. THE MODERN AGE OF MICROBIOLOGY
• Microbial Genetics
• Avery, MacLeod, and McCarty determined genes are
contained in molecules of DNA
• Beadle and Tatum established that a gene’s activity is
related to protein function
• Translation of genetic information into protein
explained
• Rates and mechanisms of genetic mutation
investigated
• Control of genetic expression by cells described
DR.T.V.RAO MD 11/16/2012 50
51. THE MODERN AGE OF MICROBIOLOGY
• Molecular Biology
• Explanation of cell function at the molecular level
• Genome sequencing
• Pauling proposed that gene sequences could
• Provide understanding of evolutionary relationships and processes
• Establish taxonomic categories that reflect these relationships
• Identify existence of microbes that have never been cultured
• Woese determined that cells belong to bacteria, archaea, or eukaryotes
• Cat-scratch fever caused by unculturable organism
DR.T.V.RAO MD 11/16/2012 51
52. THE MODERN AGE OF
MICROBIOLOGY
• Recombinant DNA Technology
• Genes in microbes, plants, and
animals manipulated for practical
applications
• Production of human blood-
clotting factor by E. coli to aid
hemophiliacs
• Gene Therapy
• Inserting a missing gene or
repairing a defective one in
humans by inserting desired gene
into host cells
DR.T.V.RAO MD 11/16/2012 52
53. DISCOVERY OF ANTIMICROBIAL AGENTS
_________
Alexander Fleming (1881 – 1955), a
Scottish biologist and
pharmacologist, observed
bacterial staphylococci colonies
disappearing on plates
contaminated with mold.
Fleming extracted the
compound from the mold
responsible for destruction of
the bacterial colonies.
The product of the mold was
named penicillin, after the
Penicillium mold from which it
was derived.
Nobel Prize in Physiology of
Medicine in 1945.
Images: Penicillium mold, PHIL #8396; Staphylococcus aureus on
DR.T.V.RAO MD 11/16/2012 53
antibiotic test plate, PHIL #2641; Poster attached to a mailbox
From the Virtual Microbiology Classroom on ScienceProfOnline.com offering advice to World War II servicemen, 1944, NIH
54. THE MODERN AGE OF
MICROBIOLOGY
• How Do We Defend Against Disease?
• Serology
• The study of blood serum
• Von Behring and Kitasato – existence in the blood of
chemicals and cells that fight infection
• Immunology
• The study of the body’s defense against specific pathogens
• Chemotherapy
• Fleming discovered penicillin
• Domagk discovered sulfa drugs
DR.T.V.RAO MD 11/16/2012 54
55. THE BIRTH OF MODERN
CHEMOTHERAPY
• Treatment with chemicals is chemotherapy.
• Chemotherapeutic agents used to treat infectious disease
can be synthetic drugs or antibiotics.
• Antibiotics are chemicals produced by bacteria and fungi
that inhibit or kill other microbes.
• Quinine from tree bark was long used to treat malaria.
• 1910: Paul Ehrlich developed a synthetic arsenic drug,
salvarsan, to treat syphilis.
• 1930s: Sulfonamides were synthesized.
DR.T.V.RAO MD 11/16/2012 55
56. THE BIRTH OF MODERN CHEMOTHERAPY
• 1928: Alexander
Fleming discovered the
first antibiotic.
• He observed that
Penicillium fungus
made an antibiotic,
penicillin, that killed S.
aureus.
• 1940s: Penicillin was
tested clinically and
mass produced.
DR.T.V.RAO MD 11/16/2012 56
57. MODERN DEVELOPMENTS IN MICROBIOLOGY
• Immunology is the study of
immunity. Vaccines and
interferons are being investigated
to prevent and cure viral
diseases.
• The use of immunology to identify
some bacteria according to
serotypes (variants within a
species) was proposed by
Rebecca Lancefield in 1933.
DR.T.V.RAO MD 11/16/2012 57
Figure 1.4 (3 of 3)
58. MODERN BIOTECHNOLOGY AND GENETIC
ENGINEERING
• Biotechnology, the use of
microbes to produce foods
and chemicals, is centuries
old.
• Genetic engineering is a
new technique for
biotechnology. Through
genetic engineering,
bacteria and fungi can
produce a variety of
proteins including vaccines
and enzymes.
DR.T.V.RAO MD 11/16/2012 58
59. SELECTED NOBEL PRIZES IN PHYSIOLOGY
OR MEDICINE
1901* von Behring Diphtheria antitoxin
1902 Ross Malaria transmission
1905 Koch TB bacterium
1908 Metchnikoff Phagocytes
1945 Fleming, Chain, Florey Penicillin
1952 Waksman Streptomycin
1969 Delbrück, Hershey, Luria Viral replication
1987 Tonegawa Antibody genetics
.
1997 Prusiner Prions
DR.T.V.RAO MD 11/16/2012 59
60. SELECTED NOVEL PRIZES IN PHYSIOLOGY OR
MEDICINE
1901* von Behring Diphtheria antitoxin
1902 Ross Malaria transmission
1905 Koch TB bacterium
1908 Metchnikoff Phagocytes
1945 Fleming, Chain, Florey Penicillin
1952 Waksman Streptomycin
1969 Delbrück, Hershey, Luria Viral replication
1987 Tonegawa Antibody genetics
1997Prusiner Prions
2003Agre, Mackirron water and ion channels
2005 Marshall, Warren Helicobacter and ulcers
2008 Hausen Papilloma and viruses
* The first Nobel Prize in Physiology or Medicine.
DR.T.V.RAO MD 11/16/2012 60
61. UNIVERSAL PRECAUTIONS SET
UP BY CDC
• Use gloves, gowns, masks and goggles
• Minimize risk of needle sticks
• Disinfections procedure
• Preventative treatment after exposure
• Reduce risk
• Treat all patients the same
• HBV greater risk than HIV
DR.T.V.RAO MD 11/16/2012 61
62. DEAR STUDENTS NEVER FORGET TO WASH HANDS
AFTER HANDLING PATIENTS OR INFECTED
MATERIAL
DR.T.V.RAO MD 11/16/2012 62
63. VISIT ME FOR MORE ARTICLES OF INTEREST ON
MICROBIOLOGY, INFECTIOUS DISEASES…
DR.T.V.RAO MD 11/16/2012 63
64. • Programme Created by Dr.T.V.Rao MD
for Undergraduate Medical and
Paramedical Students for orientation in
Learning Medical Microbiology
• email
• doctortvrao@gmail.com
DR.T.V.RAO MD 11/16/2012 64