Medical MicrobiologyMedical Microbiology (Biology of Small Organisms)(Biology of Small Organisms)

Major Topics Included in Major Topics Included in MAC 221MAC 221

Bacteriology VirologyParasitologyMycologyImmunology

Introduction To Mac 221:Introduction To Mac 221:

(I) Basic Immunology and Host Parasite Relationship

(II) Bacteria and Human Diseases caused by bacteria.

(III) Parasitology Parasite & Human Diseases

(IV) Virology – Virus & Human Diseases

(V) Mycology – Fungi & Human Diseases

Microbiology And The PatientMicrobiology And The Patient

Medical Microbiology – concerned with:

(i) Aetiology (cause)

(ii) Pathogenesis (Mechanism of production of disease)

(iii) Laboratory Diagnosis

(iv) Treatment of infection

(v) Epidemiology (spread, distribution, prevalence of infection in the community)

(vi) Control and prevention in community

MIC has Close Link with:MIC has Close Link with:

(i) Pathology

(ii) Medicine (clinical)

(iii) Surgery

(iv) Pharmacology and therapeutics

(v) Preventive Medicine

MIC has a Close Link with Curative Medicine in regard to:

(i) Precise diagnosis

(ii) Rational treatment of microbial diseases

Diagnosis of Bacterial infection done by:(i) Clinical

(ii) Laboratory Methods

Laboratory Methods: Collection of specimens

(i)(i) Microscopy Stained Specimens

Unstained Specimens

(ii) Culture

(iii) Identification of the organism

(iv) Tests for Antimicrobial agents serology

(v) Demonstration of Abs

Medical Students Need to Know Medical Students Need to Know Microbiology Especially BacteriologyMicrobiology Especially Bacteriology

1) To Diagnose

Bacterial infections successfully

2) To Treat

Course Objectives

1) Basic understanding of immune system

2) Basic understanding of host-parasite relationship

3) Understandingof the pathogenesis

4) Understand the clinical features

5) Understand the Epidemiological features

6) Understand the proper use of Clinical Lab.a) Specimen collection and handling

b) Requesting appropriate tests

c) Interpretation of results of Lab. tests

7) Correct selection, use, monitoring of anti-microbial therapy

8) Understand methods of prevention of infection e.g. Vaccine, chemoprophylaxis, hygiene, isolation etc.

Course Objectives (Continued)

Diagram of Atypical Bacterial CellDiagram of Atypical Bacterial Cell

BacteriaBacteriaUnicellular, Microscopic, Prokaryotic Organisms, Multiply By Binary Fission.

Comparison Between Bacteria And Fungi And Protozoa

Bacteria Fungi & Protozoa

Type Prokaryotic EukaryoticChromosome One Multiple

(Number)

Nuclear Absent Present

Membrane

Bacteria Fungi & Protozoa

Mitochondria Absent Present

Ribosomes 70s 80s

Sterols Absent (Except Usually In Mycoplasma) Present

Cell Wall Rigid Layer Of No Peptido-Peptidoglycan Glycan

(Absent In (In some cases

Mycoplasma) cellulose present)

Comparison Between Bacteria and Fungi and Protozoa (Continued)

Bacteria can be divided into:

1. Filamentous Bacteria (Actinomycete) Most capable of branching

2. True (Euobacteria): Divide by Binary Fission

3. Spirocheates: Divide by Transverse Binary Fission

4. Mycoplasma Which Lack Rigid Cell Wall

5. Ricketssiae, and Chlamydia which are strict Intracellular parasites

Cocci Bacilli (rods) Vibrio (coma shape)

Taxonomic RanksTaxonomic Ranks

________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Kingdom ProkaryotaeDivision GracilicutesClass ScotobacteriaOrder EubacterialesFamily Enterobacteriae

Genus Eschirichia, Streptococcus, Staphylococcus, Streptococcus, KlebsiellaSpecies coli Pyogenes aureus pneumoniae pneumonia

Formal Rank Example

Simplified Classification of Medically – Important Gram-positive Bacteria

Arranged in Micrococcus

Aerobes or clustersfacultative

StaphylococcusAnaerobes

Cocci Arranged in Streptococcus chains

Anaerobes Peptostreptococcus

Simplified Classification of Medically – Simplified Classification of Medically – Important Gram-positive bacteriaImportant Gram-positive bacteria

Sporing Bacillus

Aerobes or facultative anaerobes

CorynebacteriumNon- ListeriasporingLactobacillus

Nocardia Mycobacterium

RODS Sporing Clostridium

AnaerobesNon- Actinomycoscessporing

Simplified Classification Of Medically – Simplified Classification Of Medically – Important Gram-negative BacteriaImportant Gram-negative Bacteria

Aerobes Neisseria

Cocci

Anaerobes Veillonella

Simplified Classification Of Medically – Simplified Classification Of Medically – Important Gram-negative BacteriaImportant Gram-negative Bacteria

Aerobes PseudomonasSalmonellaShigellaKlebsiellaProteusEscherichia

Facultative YersiniaAnaerobes

BACILLIBordetella

HaemophilusBrucellaPasteurellaVibrio

Anaerobes BacteroidsFusobacterium

Microaerophilic Camplylobacter

Simplified Classification Of Medically – Simplified Classification Of Medically – Important Gram-negative BacteriaImportant Gram-negative Bacteria

Aerobes Leptospira

Spirochaetes

Anaerobes Borrelia

Treponema

Cell wall --- Mycoplasma

deficient bacteria

Diagram of Atypical Bacterial CellDiagram of Atypical Bacterial Cell

External StructuresExternal StructuresI) Flagella Long Filaments

a. Responsible for motility;

b. Protein (Flagellin) similar to myosin of muscles

c. Can be polar, Bipolar or Peritrichous

Short Filaments

a. Common pili Adhesion

b. Sex pili Conjugation

III) Capsule Present in Certain Bacteria. Water (2 %) solid

Polysaccharide; occasionally protein

e.g. Bacillus anthracis

a. Inhibit Phagocytosis

b. Antigenic

Example Of Capsulated BacteriaExample Of Capsulated Bacteria

a. Pneumococci

b. Klebsiella Polysaccharide Capsules

c. Cl. perfringens

d. Bacillus anthracis Polypeptide Capsules

Flagella

Bacterial SporesBacterial Spores Hardest part of bacteria Contain calicum pectate One spore = one negative bacteria Can live for years

Example:1. Clostidia (Anaerobic)

e.g. Cl. perfringens2. Bacillus (Aerobic)

e.g. B. anthracis

CELL WALL - porous, permeable to low molecular weight (LMW) substances. Found in Algae, fungi, plants and bacteria Not found in animals

Functions Of Cell Wall

a. Confer rigidity upon bacteria

b. Protects against osmotic pressure which can be 5-20 atmospheric pressure in bacteria

c. Gives bacteria its shape

d. Participates in cell division

e. Gram staining characteristic

Structures of Cell WallStructures of Cell Wall

Basic = mucopeptide (peptidoglycan)

PEPTIDOGLYCAN = consists of

a. N-acetyl mumaric acid (M)

b. N-acetyl glucosamine (G) strands.

Theses strands are linked by peptide side chains

Peptide

chain

G

M

G

M

G

M

In Addition Gram +ve bacterial cell wall

a Thick peptidoglycan layer (many layers)

b. Teichoic acids (20% of cell wall weight)

Gram –ve cell wall

a. Thin peptidoglycan layer (1-2 layers)

b. Out layer of lipopolysaccharide, phospholipids, lipoprotein

c. Porins

Diagrams Showing The Structure Of Bacterial Diagrams Showing The Structure Of Bacterial Cell WallsCell Walls

Annual SystemA. Bacteriology + Immunology

= 50% = 50 marksPractical = 10 marksMid term = 10 marksFinal = 30 marks

B. Parasitology & Virology + Mycology= 50% = 50 marksPractical = 10 marksMid Term = 10 marksFinal Exam= 30 marks