Classification of medically important bacteria
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Classification of medically important bacteria. Bacteria. Unicellular, Microscopic, Prokaryotic Organisms, Multiply By Binary Fission. Comparison Between Bacteria And Fungi And Protozoa Bacteria Fungi & Protozoa Type Prokaryotic Eukaryotic Chromosome One Multiple

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Classification of medically important bacteria

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Classification of medically important bacteria


Bacteria

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

Comparison Between Bacteria And Fungi And Protozoa

BacteriaFungi & Protozoa

Type Prokaryotic Eukaryotic

Chromosome One Multiple

(Number)

Nuclear Absent Present

Membrane


Comparison Between Bacteria and Fungi and Protozoa (Continued)

BacteriaFungi & Protozoa

MitochondriaAbsentPresent

Ribosomes70s80s

SterolsAbsent (ExceptUsually In Mycoplasma)Present

Cell WallRigid Layer OfNo Peptido-

Peptidoglycan Glycan (Absent In(In some cases

Mycoplasma) cellulose present)


Bacteria can be divided into:

  • Filamentous Bacteria (Actinomycete) Most capable of branching

  • True (Euobacteria): Divide by Binary Fission

  • Spirocheates: Divide by Transverse Binary Fission

  • Mycoplasma Which Lack Rigid Cell Wall

  • Ricketssiae, and Chlamydia which are strict Intracellular parasites

Vibrio (coma shape)

Cocci

Bacilli (rods)


Formal RankExample

Taxonomic Ranks

________________________________________________________________________________________________________________________

Kingdom Prokaryotae

Division Gracilicutes

Class Scotobacteria

Order Eubacteriales

FamilyEnterobacteriae

GenusEschirichia, Streptococcus, Staphylococcus, Streptococcus, Klebsiella

Species coli Pyogenes aureus pneumoniae pneumonia


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

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

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


The Gram stain has four steps:

  • 1. crystal violet, the primary stain: followed by

  • 2.gramsiodine, which acts as a mordant by forming a crystal violet-iodine complex, then

  • 3. alcohol, which decolorizes, followed by

  • 4. safranin, the counterstain.


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


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


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

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

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

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

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


Classification based on

  • Shape

  • Gram reaction

  • Oxygen

  • Free living & non free living


Simplified Classification of Medically – Important Gram-positive BacteriaFree living

Arranged in Micrococcus

Aerobes or clusters

facultative Staphylococcus

Anaerobes

Cocci Arranged in Streptococcus

chains

Anaerobes

Peptostreptococcus


Simplified Classification of Medically – Important Gram-positive bacteria

SporingBacillus

Aerobes or facultative anaerobes Corynebacterium

Non-Listeria

sporingLactobacillus

Nocardia

Mycobacterium

RODS

Sporing Clostridium

Anaerobes

Non- Actinomycosces

sporing


Simplified Classification Of Medically – Important Gram-negative Bacteria

AerobesNeisseria

Cocci

AnaerobesVeillonella


Important Gram-negative Bacteria

AerobesPseudomonas

Salmonella

Shigella

enterKlebsiella

obacProteus

teriaeEscherichia

Facultative caeYersinia

Anaerobes

BACILLIrespirleigonellaBordetella

Haemophilus

zoonotBrucella

Pasteurella

francisella

yersinia

Vibrio(curved)

AnaerobesBacteroids

Fusobacterium

MicroaerophilicCamplylobacter


Simplified Classification Of Medically – Important 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 bacteria


Diagrams Showing The Structure Of Bacterial Cell Walls


Microbiology And The Patient

Medical Microbiology – concerned with:

  • Aetiology (cause)

  • Pathogenesis (Mechanism of production of disease)

  • Laboratory Diagnosis

  • Treatment of infection

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

  • Control and prevention in community


Laboratory Methods: Collection of specimens

  • MicroscopyStained Specimens

    Unstained Specimens

  • Culture

  • Identification of the organism

  • Tests for Antimicrobial agents serology

  • 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

  • Correct selection, use, monitoring of anti-microbial therapy

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


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