Medical Microbiology for Graduates

7/30/2019 Medical Microbiology for Graduates

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Dr.T.V.Rao MD

MICROBIOLOGY FORMEDICAL GRADUATES

WHAT YOU SHOULD KNOW

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AIMS FOR LEARNING MEDICAL

MICROBIOLOGY

What is medical microbiology?

Why is it relevant?

Some important concepts.

Basic classification of organisms.

Classifying bacteria.

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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 inhuman beings

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THE EARLY YEARS OF MICROBIOLOGY

CONTRIBUTED BY DISCOVERY OF MICROSCOPE

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THE FIRST OBSERVATIONS

1673-1723, Antonivan Leeuwenhoekdescribed live

microorganisms thathe observed inteeth scrapings, rainwater, andpeppercorninfusions.

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THE EARLY YEARS OF

MICROBIOLOGY How Can Microbes Be Classified?

Carolus Linnaeus (Swedish) developed taxonomic system fornaming plants and animals and grouping similar organismstogether

Leeuwenhoeks microorganisms grouped into six categories asfollows:

Fungi

Protozoa

Algae

Bacteria

Archaea

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WHAT IS MEDICAL MICROBIOLOGY?

THE PURPOSE OF LEARNING

What organisms cause

infection?How they cause infection.

How to treat them.

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WHY IS IT IMPORTANT?

Infection is one of the most importantcauses 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 infectionwhilst in hospital.

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THE HISTORICAL CONTRIBUTION IN THE

SUBJECT OF MICROBIOLOGY BY

Linnaeus Jenner

Hooke

Leeuwenhoek

Lister

Pasteur Koch

Darwin

Salk

Watson & Crick

Jacob and Monod

McClintock

Woese

Venter?

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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 organisms

genes, have provided new tools for classifyingmicroorganisms.

Proteomics is looking at the gene products

DEFINITIONS

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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

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Different:

Diseases

Modes oftransmission

Treatment-e.g.

routinely use

antibiotics dont cure

vira lfungalinfections

RELEVANCE OF CLASSIFICATION

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THE GOLDEN AGE OF MICROBIOLOGY

LOUIS PASTEUR CHANGES THE FUTURE OF

MICROBIOLOGY

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FERMENTATION AND PASTEURIZATION

Pasteur demonstrated thatthese spoilage bacteria couldbe killed by heat that was not

hot enough to evaporate thealcohol in wine.

Pasteurization is the

application of a high heat for ashort time.

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Kochs Postulates

Suspected causative agent must be found inevery case of the disease and be absent fromhealthy hosts

Agent must be isolated and grown outside thehost

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

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Normal Microbiota prevent growth ofpathogens.

Normal Microbiota produce growth factors

such as folic acid and vitamin K.

Resistance is the ability of the body toward off disease.

Resistance factors include skin,

stomach acid, and antimicrobial

chemicals.

Biofilms are extremely important inmicrobial ecology

NORMAL MICROBIOTA

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NORMAL MICRO BIOTA ON THE HUMAN BODY

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NORMAL MICROBIOTA Animals, including humans, are usually germfree

in utero. Microorganisms begin colonization in and on thesurface of the body soon after birth.

Microorganisms that establish permanent coloniesinside or on the body without producing diseasemake up the normal microbiota.

Transient microbiota are microbes that arepresent for various periods and thendisappear.

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WE HAVE MORE MICROBES OCCUPYING OUR BODY

THAN OUR OWN CELLS

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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

CLASSIFYING BACTERIA

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How?

1st into broad groups based

on microscopic appearance

Then divided into speciesbased on a range of

different properties-often

biochemical reactions e.g.

some may be able tometabolise a sugar that

others cannot.

CLASSIFYING BACTERIA

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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 basedon shape (rod=long thin or

coccus=round).

Thus we end up with 4

combinations:

G+ rod, G+ coccus, G- rod, G-

coccus

GRAM STAIN

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BACTERIAL CELL WALL MAKES THE

BASIC DIFFERENCE

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GRAM STAIN

STAIN the slide withcrystal violet for 1-2 min.

Flood slide with Gram's

iodine for 1-2 min. Decolourise by washing

the slide briefly withacetone (2-3 seconds).

Stain with safranincounterstain for 2 min.

View under microscope

G+ve G-ve

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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, CSF1st result available on blood

cultures

GRAM STAIN

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GRAM POSITIVE COCCI

Clusters: usually

characteristic of

Staphylococcus spp., such as

S. aureus

Chain or pairs: usually characteristic

ofStreptococcus spp., such as

S. pneumoniae

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GRAM POSITIVE BACILLI Thick : usually

characteristic ofClostridium spp., suchas C. perfringens, C.

difficle,C. tetani

Thin: e.g. Listeria spp.

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GRAM NEGATIVE BACILLI

Thin rods: usuallycharacteristic ofenterobacteriaceae(coliforms), such as E. Coli

Coccobacilli: usually

characteristic ofHaemophilus spp., such asH. influenzae

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GRAM NEGATIVE BACILLI

Curved: usuallycharacteristic ofVibriospp.or Campylobacterspp.,such as V. cholerae C. jejuni

Thin needle shape: usually

characteristic ofFusobacterium spp.

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GRAM NEGATIVE COCCI

Diplococci: usually characteristic ofNeisseria spp., such as N.meningitides or N. gonorrhea.ThoughIn addition, Moraxella spp.andAcinetobacterspp.are oftendiplococcal in morphology.

Coccobacilli: usually characteristicofAcinetobacterspp., which can beeither Gram-positive or Gram-negative, and is often called Gram-variable.

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WHAT CAN YOU SEE ON THE SLIDE?

Staphylococcus aureus 100xGram

+ve

coc

ci

Gram

+ve

bacilli

Gram

ve

coc

ci

Gram

ve

bacilli

47%

0%

53%

0%

1. Gram +ve cocci

2. Gram +ve bacilli

3. Gramve cocci

4. Gramve bacilli

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Gram

+ve

coc

ci

Gram

+ve

bacilli

Gram

ve

coc

ci

Gram

ve

bacilli

16%11%

5%

68%

1. Gram +ve cocci

2. Gram +ve bacilli

3. Gramve cocci

4. Gramve bacilli

Streptococcus pneumoniae

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Pseudomonas aeruginosa

Gram

+ve

coc

ci

Gram

+ve

bacilli

Gram

ve

coc

ci

Gram

ve

bacilli

14%

36%36%

14%

1. Gram +ve cocci

2. Gram +ve bacilli

3. Gramve cocci

4. Gramve bacilli

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VIRUSES

Small (50-300nm)

Unable to replicate

independently

Invade host cells and usetheir cellular machinery to

replicate

Influenza, Chickenpox(varicella), Herpes,

Rhinovirus, HIV/AIDS

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FUNGI Complex, large organisms

Eukaryotes (as are humans!)

Divided into yeasts & moulds

Cause a range of diseasese.g.:

Thrush

Athletes foot

Invasive & allergic aspergillosis

Many diseases areopportunistic.

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PROTOZOA

Eukaryotes

Absorb or ingest

organic chemicals

May be motile via

pseudopods, cilia,

or flagella

Figure 1.1c17-11-2012DR.T.V.RAO MD 38

MULTICELLULAR ANIMAL


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MULTICELLULAR ANIMAL

PARASITES Eukaryote

Multicellular animals

Parasitic flatworms and round worms are called Helminths.

Microscopic stages in life cycles.

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THE ETIOLOGY OF INFECTIOUS DISEASES

Kochs postulates are criteria for establishing thatspecific microbes cause specific diseases.

Kochs postulates have the following requirements:

(a) the same pathogen must be present in every case ofthe disease;

(b) the pathogen must be isolated in pure culture;

(c) the pathogen isolated from pure culture must cause thesame disease in a healthy, susceptible laboratoryanimal;

(d) the pathogen must be reisolated from the inoculatedlaboratory animal.

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Figure 14.7

KOCHS POSTULATES

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EXCEPTIONS TO KOCHS POSTULATES


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EXCEPTIONS TO KOCHS POSTULATES

Kochs postulates are modified to establish etiologies of

diseases caused by viruses and some bacteria, which cannotbe grown on artificial media.

Some diseases, such as tetanus, have unequivocal signsand symptoms.

Some diseases, such as pneumonia and nephritis, may becaused 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.

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Disease-causing microorganisms arecalled pathogens.

Pathogenic microorganisms have specialproperties that allow them to invade thehuman body or produce toxins.

When a microorganism overcomes thebodys defenses, a state of diseaseresults.

Diseases and Infections

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O OG C O S S


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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 broughtabout 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

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IMMUNITY PROTECTS FROM EVENTS WITH

INFECTIONS

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CLASSIFYING INFECTIOUS DISEASES


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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 tomake a diagnosis (identification of the disease)

Fever, swelling, paralysis

A specific group of symptoms or signs that alwaysaccompanies a specific disease is called asyndrome.

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MICROORGANISMS

Figure 1.117-11-2012DR.T.V.RAO MD 47



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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

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THE MODERN AGE OF MICROBIOLOGY

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Microbial Genetics

Avery, MacLeod, and McCarty determined genes arecontained in molecules of DNA

Beadle and Tatum established that a genes activity is

related to protein function Translation of genetic information into protein

explained

Rates and mechanisms of genetic mutationinvestigated

Control of genetic expression by cells described

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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

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THE MODERN AGE OF


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Recombinant DNA Technology

Genes in microbes, plants, andanimals manipulated for practicalapplications

Production of human blood-clotting factor by E. colito aidhemophiliacs

Gene Therapy

Inserting a missing gene orrepairing a defective one in

humans by inserting desired geneinto host cells

THE MODERN AGE OF

MICROBIOLOGY

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DISCOVERY OF ANTIMICROBIAL AGENTS


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DISCOVERY OF ANTIMICROBIAL AGENTS

_________

Alexander Fleming (1881 1955),aScottish biologist andpharmacologist, observedbacterial staphylococci coloniesdisappearing on platescontaminated with mold.

Fleming extracted thecompound from the moldresponsible for destruction ofthe bacterial colonies.

The product of the mold wasnamed penicillin, after the

Penicilliummold from which itwas derived.

Nobel Prize in Physiology ofMedicine in 1945.

Images: Penicilliummold, PHIL #8396; Staphylococcus aureusonantibiotic test plate, PHIL #2641; Poster attached to a mailboxoffering advice to World War II servicemen, 1944, NIHFrom the Virtual Microbiology Classroom on ScienceProfOnline.com

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THE MODERN AGE OF
http://phil.cdc.gov/phil/home.asphttp://en.wikipedia.org/wiki/File:Staphylococcus_aureus_(AB_Test).jpghttp://en.wikipedia.org/wiki/File:Staphylococcus_aureus_(AB_Test).jpghttp://en.wikipedia.org/wiki/File:Staphylococcus_aureus_(AB_Test).jpghttp://en.wikipedia.org/wiki/File:PenicillinPSAedit.jpghttp://en.wikipedia.org/wiki/File:PenicillinPSAedit.jpghttp://www.scienceprofonline.com/virtual-micro-main.htmlhttp://www.scienceprofonline.com/http://en.wikipedia.org/wiki/File:PenicillinPSAedit.jpghttp://www.scienceprofonline.com/http://www.scienceprofonline.com/virtual-micro-main.htmlhttp://en.wikipedia.org/wiki/File:PenicillinPSAedit.jpghttp://en.wikipedia.org/wiki/File:PenicillinPSAedit.jpghttp://en.wikipedia.org/wiki/File:Staphylococcus_aureus_(AB_Test).jpghttp://en.wikipedia.org/wiki/File:Staphylococcus_aureus_(AB_Test).jpghttp://en.wikipedia.org/wiki/File:Staphylococcus_aureus_(AB_Test).jpghttp://en.wikipedia.org/wiki/File:Staphylococcus_aureus_(AB_Test).jpghttp://phil.cdc.gov/phil/home.asp


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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 ofchemicals and cells that fight infection

Immunology

The study of the bodys defense against specific pathogens

Chemotherapy

Fleming discovered penicillin

Domagk discovered sulfa drugs

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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 fungithat 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.

THE BIRTH OF MODERN

CHEMOTHERAPY

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1928: Alexander

Fleming discovered the

first antibiotic.

He observed thatPenicillium fungus

made an antibiotic,

penicillin, that killed S.

aureus.

1940s: Penicillin was

tested clinically and

mass produced.

THE BIRTH OF MODERN CHEMOTHERAPY

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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 aspecies) was proposed by

Rebecca Lancefield in 1933.

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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 canproduce a variety of

proteins including vaccines

and enzymes.

MODERN BIOTECHNOLOGY AND GENETIC

ENGINEERING

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SELECTED NOBEL PRIZES IN PHYSIOLOGY


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1901* von Behring Diphtheria antitoxin1902 Ross Malaria transmission

1905 Koch TB bacterium

1908 Metchnikoff Phagocytes

1945 Fleming, Chain, Florey Penicillin1952 Waksman Streptomycin

1969 Delbrck, Hershey, Luria Viral replication

1987 Tonegawa Antibody genetics

1997 Prusiner Prions

SELECTED NOBEL PRIZES IN PHYSIOLOGY

OR MEDICINE

.

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SELECTED NOVEL PRIZES IN PHYSIOLOGY OR


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* The first Nobel Prize in Physiology or Medicine.

SELECTED NOVEL PRIZES IN PHYSIOLOGY OR

MEDICINE1901* von Behring Diphtheria antitoxin

1902 Ross Malaria transmission1905 Koch TB bacterium

1908 Metchnikoff Phagocytes

1945 Fleming, Chain, Florey Penicillin

1952 Waksman Streptomycin

1969 Delbrck, 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

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UNIVERSAL PRECAUTIONS SET


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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

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DEAR STUDENTS NEVER FORGET TO WASH HANDS


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AFTER HANDLING PATIENTS OR INFECTED

MATERIAL

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VISIT ME FOR MORE ARTICLES OF INTEREST ON

MICROBIOLOGY, INFECTIOUS DISEASES

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Programme Created by Dr.T.V.Rao MD

for Undergraduate Medical and

Paramedical Students for orientation in

Learning Medical Microbiology

email

[email protected]

Medical Microbiology for Graduates

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