Dr.T.V.Rao MD 1

Dr.T.V.Rao MD

INTRODUCTION TO MEDICAL MICROBIOLOGY

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What is Microbiology?

Microbes, or microorganisms are minute living things that are usually unable to be viewed with the naked eye.

What are some examples of microbes?

Bacteria, fungi, protozoa, algae, viruses are examples!

Some are pathogenicMany are beneficial

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Microbiology defined as the study of organisms too small to be seen with the naked eye. These organisms include viruses, bacteria, algae, fungi, and protozoa. Microbiologists are concerned with characteristics and functions such as morphology, cytology, physiology, ecology, taxonomy, genetics, and molecular biology.

Defining Microbiology

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What is Microbiology

• Study of different Microorganisms

• Can be Bacteria Viruses Parasites Fungus

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What are Microorganisms

• Microbes are products of evolution, Consequence of Natural selection operating upon vast array of genetically diverse organisms

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History of Microbiology1673-1723, Antoni van Leeuwenhoek (Dutch) described live microorganisms that he observed in teeth scrapings, rain water, and peppercorn infusions.

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Anton van Leeuwenhoek 1674 - 1st person to actually see living microorganisms

“wee animalcules”

荷兰人吕文虎克（ Leeuwenhoek） 1632-1723

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History of Microbiology

The Germ Theory of Disease

1835: Agostino Bassi showed a silkworm disease was caused by a fungus.

1865: Pasteur believed that another silkworm disease was caused by a protozoan.

1840s: Ignaz Semmelweis advocated handwashing to prevent transmission of puerperal fever from one OB patient to another.

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The Germ Theory of Disease

• 1860s: Joseph Lister used a chemical disinfectant to prevent surgical wound infections after looking at Pasteur’s work showing microbes are in the air, can spoil food, and cause animal diseases.

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History of microbiology Anton van Leeuwenhoek (1632–1723): was the first microbiologist and the first person to observe bacteria using a single-lens microscope of his own design.

Louis Pasteur (1822–1895): Pasteur developed a process (today known as pasteurization) to kill microbes. pasteurization is accomplished by heating liquids to 63° to 65°C for 30 minutes or to 73° to 75°C for 15 seconds.

Robert Koch (1843–1910): was a pioneer in medical microbiology and worked in cholera, anthrax and tuberculosis. He was awarded a Nobel prize in 1905 (Koch's postulates) he set out criteria to test.

Alexander Fleming (1929): Discovered penicillin.

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Joseph Lister• 1860s: Joseph Lister

used a chemical disinfectant to prevent surgical wound infections after looking at Pasteur’s work showing microbes are in the air, can spoil food, and cause animal diseases.

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Course objectives• To provide the student with the basic

knowledge of micro-organisms in general

• To study the main characteristics of Microbes of medical importance

• To teach aseptic techniques• To provide an understanding of

antimicrobial agents

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Other Objectives

• To teach the basic immunological principles

• Immunological methods for the study immunological disorders

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Coverage of subject• General

Microbiology• Bacteriology• Mycology• Virology• Immunology• Parasitology

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Microbes in Our Lives

• Microorganisms are organisms that are too small to be seen with the unaided eye.

• “Germ” refers to a rapidly growing cell.

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Microbes make the Universe

• There are > 5 x 1030 types Microbes in the world

• Humans have intimate relation with Microbes > 90% of the cells in our Body are Microbes

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Classification of Microorganisms

• Three domains– Bacteria– Archaea– Eukarya

• Protists• Fungi• Plants• Animals

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Naming and Classifying Microorganisms

• Carolus Linnaeus (1735) established the system of scientific nomenclature.

• Each organism has two names: the genus and specific epithet.

• Are italicized or underlined. The genus is capitalized and the specific epithet is lower case.

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Edward Jenner Vaccinating aChild

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Louis Pasteur1922 - 95

• Contributed best in Microbiology

• Sterilization• Hot Air oven• Autoclave• Anthrax vaccine• Rabies vaccine• Built the Pasteur

Institute

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Louis Pasteur

• Pasteur coined the word Vaccine

• Vacca – Cow cow pox virus are given for the prevention of Small Pox

• Louis Pasteur considered the father of Modern Microbiology

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Robert Koch1843 - 1910

• A German scientist• Formulated the

Bacteriological techniques

• Staining Methods• Discovered the Mycobacterium and Vibrio cholera

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Biological Principles illustrated by Microbiology

Microbiology

Biochemistry MolecularBiology Genetics

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Microorganisms

Non-cellular organism

Prokaryotes

Eukaryotes

Others Prions Viroid

Fungi

Bacterium

Virus

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Organisms included in the study of Microbiology

1. Bacteria2. Protozoans3. Algae4. Parasites5. Yeasts and Molds

Fungi

6. Viruses

BacteriologyProtozoologyPhycologyParasitology

MycologyVirology

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Man has Evolved So also the Microbes

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How to Study Medical Microbiology?

Fundamentals of Microbiology

Bacteriology

Virology

Mycology

•Biological Properties• Morphology, identification, • Antigenic structure

•Pathogenesis and Pathology• Clinical findings

•Diagnostic Laboratory Tests•Immunity•Treatment & Prevention

• Epidemiology & Control

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Basic Classification of Microorganism

• Eukaryotes Large in size Mitochondria Present Membrane bound Nucleus Eg Algae Protozoa Fungi Slime Moulds Contains all enzymes for production of metabolic energy

Prokaryotes Small in Size DNA not separated from cytoplasm Mitochondria absent

Eg Bacteria

Contains all enzymes like Eukaryotes

Prokaryotic cells Eukaryote cells

Small cell (< 5µm) Larger cells (> 10 µm)

Always unicellular Often multicellular

No nucleus or any membrane bound organelles Always have nucleus and membranes bound organelles.

DNA circular, without proteins DNA is linear and associated with proteins to form chromatin.

Ribosomes are small 70S Ribosomes are large 80S

No cytoskeleton Always have cytoskeleton

Motility by rigid rotating flagellum made from flagellin

Motility by flexible waving cilia or flagella made from tubulins.

Cell division is by binary fission Cell division is by meiosis and mitosis.

Reproduction is always asexual Reproduction is sexual and asexual.

Summary of differences between prokaryote and eukaryote cells

Prokaryotic Cell Structure

Prokaryotic cells are about 10 times smaller than eukaryotic cells. A typical Escherichia coli cell is about 1 μm wide and 2 to 3 μm long. Structurally, prokaryotes are very simple cells when compared with eukaryotic cells, and yet they are able to perform the necessary processes of life. Reproduction of prokaryotic cells is by binary fission, the simple division of one cell into two cells, after DNA replication and the formation of a separating membrane and cell wall.

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Bacteria• Prokaryotes• Peptidoglycan cell

walls• Binary fission• For energy, use

organic chemicals, inorganic chemicals, or photosynthesis

Bacterial Cell Wall The structure of bacterial cell walls is quite different from the relatively simple structure of eukaryotic cell walls, although they serve the same functions, providing rigidity, strength, and protection. The main constituent of most bacterial cell walls is a complex macromolecular polymer known as peptidoglycan (murein), consisting of many polysaccharide chains linked together by small peptide (protein) chains. Peptidoglycan is only found in bacteria. The thickness of the cell wall and its exact composition vary with the species of bacteria. The cell walls of “Gram-positive bacteria” have a thick layer of peptidoglycan combined with teichoic acid and lipoteichoic acid molecules. The cell walls of “Gram-negative bacteria” have a much thinner layer of peptidoglycan, but this layer is covered with a complex layer of lipid macromolecules, usually referred to as bacteria capsule.

Figure 1-9: Gram Stain

Figure 3-1. Various forms of bacteria, including single cocci, diplococci, tetrads, octads, streptococci, staphylococci, single bacilli, diplobacilli, streptobacilli, branching bacilli, loosely coiled spirochetes, and tightly coiled spirochetes.

Morphologic arrangements of bacteria.

Capsule stain. The capsule stain is an example of a negative staining technique. The bacterial cells and the background stain, but the capsules do not. The capsules are seen as unstained “halos” around the bacterial

cells.

. Flagellar arrangement. The four basic types of flagellar arrangement on bacteria: peritrichous, flagella all over the surface; lophotrichous, a tuft of flagella at one end;

amphitrichous, one or more flagella at each end; monotrichous, one flagellum.

Binary fission. Note that DNA replication must occur before the actual splitting (fission) of the parent cell.

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Pathogenic Prokaryotes

Mycoplasma

Bacteria

Spirochetes

Rickettsia

Chlamydiae

Actinomyces

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Viruses

Viruses lack many of the attributes of cells, including the ability to replicate. Only when it infects a cell does a virus acquire the key attribute of a living system: reproduction

A viral particle consists of a nucleic acid molecule, either DNA or RNA, enclosed in a protein coat, or capsid

Viruses are known to infect all cells, including microbial cells. Host-virus interactions tend to be highly specific

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Discovery of Virus• Iwanovski

– a Russian chemist, 1892– Tobacco Mosaic Disease

• Beijerinck confirmed

• Walter Reed, USA– Yellow fever virus– Ist human virus

Tobacco mosaic disease, caused by the tobacco mosaic virus

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Viruses• A virus is not a cell!• Viruses are replicated

only when they are in a living host cell

• Consist of DNA or RNA core

• Core is surrounded by a protein coat

• Coat may be enclosed in a lipid envelope

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What are Viruses

• Viruses Dependent on Host cells for necessary functions and Multiplication

• Intracellular parasites

• Contain either DNA or RNA never both.

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PrionA kind of infectious protein that can resist the digestion of proteinase

The cellular form of the prion protein (PrPc) is encoded by the host’s chromosomal DNA

An abnormal isoform of this protein (PrPres) is the only known component of the prion and is associated with transmissibility.

Kuru, Creutzfeldt-Jakob disease (CJD), Gerstmann-Sträussler-Scheinker disease, fatal familial insomnia, and Bovine spongiform encephalopathy (BSE)

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ViroidSmall, single-stranded, covalently closed circular RNA molecules existing as highly base-pairedrod-like structures; they do not possess capsids

They range in size from 246 to 375 nucleotides in length. The extracellular form of the viroid is naked RNA—there is no capsid of any kindThe RNA molecule contains no protein-encoding genes, and the viroid is therefore totally dependent on host functions for its replicationThe RNAs of viroids have been shown to containinverted repeated base sequences at their 3' and 5' ends, a characteristic of transposable elements and retroviruses. Thus, it is likely that they have evolvedfrom transposable elements or retroviruses by the deletion of internal sequences

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Koch’s Postulates

1 The bacterium should be constantly associated with lesions of Disease

2 It should be possible to isolate the bacterium in pure culture from the lesions

3 Inoculation of such pure culture into laboratory animal should reproduce the lesions of the disease

4 It is possible to reisolate the bacterium in pure culture from the lesions produced in the experimental animal

Additional criterion specific antibodies in the serum of patients suffering with disease

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Koch’s postulates

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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.

Scientific era of Antibiotics

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Discovery of Antibiotics• Alexander Fleming (1881-1955)

Sir Alexander Fleming Ernst Boris Chain Sir Howard Walter Florey

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Microbes are used to produce Antibiotics

• Penicillin

• Mold – Pencillium notatum

• 1928 Alexander Fleming

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Modern Developments• 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.

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Microbes and Human Disease

• Normal micro biota prevent growth of pathogens.

• Normal micro biota 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.

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How to Study Medical Microbiology?

Fundamentals of Microbiology

Bacteriology

Virology

Mycology

•Biological Properties• Morphology, identification, • Antigenic structure

•Pathogenesis and Pathology• Clinical findings

•Diagnostic Laboratory Tests•Immunity•Treatment & Prevention

• Epidemiology & Control

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Bacteria - what comes to mind?• Diseases• Infections• Epidemics• Food Spoilage• Only 1% of all known bacteria cause human

diseases• About 4% of all known bacteria cause plant

diseases• 95% of known bacteria are non-pathogens

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• Staphylococcus aureus

• Staphylococcus epidermidis

• Streptococcus pneumonia

• Vibrio cholera

• Rhodospirillium rubrum

• Bacillus subtilis

• Micrococcus luteus

• Escherichia coli• Bacillus anthrasis• Salmonella enteridis• Streptococcus pyogenes• Steptococcus lactis• Streptococcus faecalis• Erlichia canis• Campylobacter jujuni• Helicobacter pylori• Enterobacter aerogenes

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Microbes Benefit Humans

1.Bacteria are primary decomposers - recycle nutrients back into the environment (sewage treatment plants)

2. Microbes produce various food products – cheese, pickles, sauerkraut, green olives– yogurt, soy sauce, vinegar, bread– Beer, Wine, Alcohol

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Microbes are also capable of causing many diseases

Pneumonia Whooping CoughBotulism Typhoid Fever MeaslesCholera Scarlet Fever MumpsSyphilis Gonorrhea Herpes 1Chlamydia Tuberculosis Herpes 2Meningitis Tetanus RMSVStrep Throat Lyme Disease AIDSBlack Plague Diarrhea Gangrene

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Progress of Hepatitis Viruses

• 1947, concepts of hepatitis A and serum-transmitted hepatitis

• 1970, Dane particle was observed (hepatitis B virus)

• 1973, hepatitis A virus• 1978, non-A, non-B hepatitis viruses

(NANBV)• 1989, hepatitis C virus (HCV), hepatitis E

virus (HEV)• 1990-1994, non A-E hepatitis viruses• 1995, hepatitis G virus (HGV)• 1997, TT virus (TTV)

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Human Immunodeficiency Virus & AIDS

• 1981, the first cases report about AIDS

• 1983, HIV was isolated• 1990s, HAART (cocktail

therapy) was employed• So far, no effective vaccine

available

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HIV – AIDS • Luc Montaigner and

Robert Gallo announce their discovery of the immunodeficiency virus (HIV) believed to cause AIDS. (American Society for Microbiology Archives)

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Parasitology• Parasitology is the study

of parasites .and their interactions with their hosts. The science of parasitology has a long history and has its roots in zoology, with its emphasis on the identification and classification of parasites and of life cycles,

Taxonomic classification of parasitic organisms

• The classification of parasites is controversial - there is no universally accepted system

• Parasites form part of the animal kingdom which comprises some 800,000 identified species categorised into 33 phyla (but it is estimated that there may be ~10m species in total)

• The parasitic organisms that are of importance for human health are eukaryotes - they have a well defined chromosome in a nuclear membrane (as opposed to prokaryotes which have no nuclear membrane, e.g. bacteria)

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Taxonomic classification of parasitic organisms

• Parasites are classified into 2 sub-kingdoms: protozoa (unicellular) and metazoa (multicellular)

• Protozoan (unicellular) parasites are classified according to morphology and means of locomotion. There are 45,000 protozoa species. Most species that cause human disease belong to the phylum's sarcomastigophora and apicomplexa

• Metazoa (multicellular) include the worms (helminths) and arthropoda (posses an external skeleton) e.g. ticks, lice

• Note that the genus starts with a capital letter and the species is always written in italics, e.g. Plasmodium falciparum, Giardia lamblia

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What Are Fungi

• Considerable variation in size.

• Internal Molecular system• Well defined cell wall

composed of polysaccharides

• Gaining importance in Immunosupressed patients and increased use of Antibiotics

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Zoonotic Diseases

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How Humans Respond to InfectionsStudy of Immunology

• In spite of Infection we survive with our ability to protect with a system inherent in our Body

• Called the Immune response comprises the Medical Immunology

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PathogenesisImmunity

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Immunity Protects the Living by Complex Mechanisms

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Why we should Medical Microbiology

• We study the Microbes which infects and causes Diseases

• We study their Diagnosis Prevention Treatment

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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 a species) was proposed by Rebecca Lancefield in 1933.

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Must learn

• Natural History of the Disease• Etiology• Pathogenesis• Laboratory Diagnosis• Treatment and Control and

Prevention

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We must be familiar with Knowledge On ….

• Names of the Microbes• Names of the diseases• Mode of transmission• Pathogenic Microbes• Commensal Organisms• Identify wether Bacteria, Virus, Parasite or

Fungi• Treating and Preventing

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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

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.

The Birth of Modern Chemotherapy

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Commonly Used Antibiotics

• Penicillin• Cephalosporins,• Tetracycline's • Quinolones• Vancomycin• Chloramphenicol• Drugs for Tuberculosis eg Streptomycin

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Vaccines Produce Immunityand Prevents Several Infections

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Commonly used Vaccines

• Small pox eradicated• BCG,• MMR• Polio oral Vaccine• Triple Antigen• Hepatitis B Vaccine

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What Skills You should Develop

Able to identify the Infective ConditionsTimely DiagnosisChoosing appropriate testsSelection of AntibioticsImplement measures to prevent diseases

in patients and Society

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Protect Yourself from Infections

• Certain infections can infect you

• Eg HIV, Hepatitis B infections,Tuberculosis,Many respiratory infections

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Working In the Hospital

• Hospitals are not safe • Follow Universal

precaution protect yourself as our patients can be source of Infection if you don't handle the matters with scientific knowledge.

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Medical Microbiology advanced Beyond our Imagination

Can we handle it ???

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* The first Nobel Prize in Physiology or Medicine.

Major 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, LuriaViral replication

1987 Tonegawa Antibody genetics

1997 Prusiner Prions

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Students requirement for the course

• Timetable • Literature – books, etc • Practical manual• Laboratory coat• Attendance and active participation• Seek advice timely

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• The Programme created by Dr.T.V.Rao MD for Medical students

in the Developing world • Email

• doctortvrao@gmail.com