Classification of medically Classification of medically important bacteriaimportant bacteria

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

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Kingdom ProkaryotaeDivision GracilicutesClass ScotobacteriaOrder EubacterialesFamily Enterobacteriae

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

Formal Rank Example

The The Gram stainGram stain, t bacteria into two main , t bacteria into two main groups, is the first step in bacterial groups, is the first step in bacterial classfication & identification. classfication & identification. 

Bacteria stained Bacteria stained purple are Gram + purple are Gram + - their - their cell walls have thick petidoglycan and cell walls have thick petidoglycan and teichoic acid. teichoic acid.

Bacteria stained Bacteria stained pink are Gram – pink are Gram – their cell their cell walls have have thin peptidoglycan and walls have have thin peptidoglycan and lipopolysaccharides with lipopolysaccharides with nono teichoic acid. teichoic acid.

The Gram stain has four steps:The Gram stain has four steps: 1. 1. crystal violetcrystal violet,, the the primary stainprimary stain: :

followed byfollowed by

2.2.gramsgrams iodineiodine,, which acts as a which acts as a mordantmordant by forming a crystal violet-iodine complex, by forming a crystal violet-iodine complex, thenthen

3. 3. alcoholalcohol, , which which decolorizesdecolorizes, followed by, followed by

4. 4. safraninsafranin, the , the counterstaincounterstain..

Is this gram stain positive or negative? Is this gram stain positive or negative? Identify the bacteria.Identify the bacteria.

Is this gram stain positive or negative? Is this gram stain positive or negative? Identify the bacteria.Identify the bacteria.

Gram staining tests the bacterial cell wall's Gram staining tests the bacterial cell wall's ability to retain ability to retain crystal violetcrystal violet dye during solvent dye during solvent treatment. treatment.

Iodine is added as a mordant to form the Iodine is added as a mordant to form the crystal crystal violet/iodineviolet/iodine complex in order to render the dye complex in order to render the dye impossible to remove. impossible to remove.

Ethyl-alcohol solvent acts as a decolorizer and Ethyl-alcohol solvent acts as a decolorizer and dissolves the lipid layer from gram-negative dissolves the lipid layer from gram-negative cells. This enhances leaching of the primary cells. This enhances leaching of the primary stain from the cells into the surrounding solvent.stain from the cells into the surrounding solvent.

Ethyl-alcohol will dehydrate the thicker gram-Ethyl-alcohol will dehydrate the thicker gram-positive cell walls, closing the pores as the cell positive cell walls, closing the pores as the cell wall shrinks.  wall shrinks. 

For this reason, the diffusion of the crystal violet-For this reason, the diffusion of the crystal violet-iodine staining is inhibited, so the bacteria iodine staining is inhibited, so the bacteria remain stained.  remain stained. 

Classification based onClassification based on

ShapeShape Gram reactionGram reaction Oxygen Oxygen Free living & non free livingFree living & non free living

Arranged in Micrococcus

Aerobes or clustersfacultative

StaphylococcusAnaerobes

Cocci Arranged in Streptococcus chains

Anaerobes Peptostreptococcus

Simplified Classification of Medically – Important Gram-positive Bacteria

Free living

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

Important Gram-negative BacteriaImportant Gram-negative BacteriaAerobes PseudomonasSalmonellaShigella enterKlebsiella obac Proteus teriae Escherichia

Facultative cae YersiniaAnaerobes

BACILLI respir leigonellaBordetellaHaemophilus zoonot BrucellaPasteurella

francisella yersinia

Vibrio(curved)

Anaerobes BacteroidsFusobacteriumMicroaerophilic Camplylobacter

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

Aerobes Leptospira

Spirochetes Treponema

Anaerobes Borrelia

Cell wall deficient bacteria------- Mycoplasma

2.Non- free living intra cellular— Rickettsia &chlamydia

Capsule Present in Certain Bacteria.

Polysaccharide; occasionally protein

e.g. Bacillus anthracis

importance

a. Inhibit Phagocytosis

b. Antigenic

Study template for bacteriaStudy template for bacteria

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

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

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

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.