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Classification of medically Classification of medically important bacteriaimportant bacteria
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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
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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)
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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)
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Taxonomic RanksTaxonomic Ranks
________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
Kingdom ProkaryotaeDivision GracilicutesClass ScotobacteriaOrder EubacterialesFamily Enterobacteriae
Genus Eschirichia, Streptococcus, Staphylococcus, Streptococcus, KlebsiellaSpecies coli Pyogenes aureus pneumoniae pneumonia
Formal Rank Example
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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.
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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..
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Is this gram stain positive or negative? Is this gram stain positive or negative? Identify the bacteria.Identify the bacteria.
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Is this gram stain positive or negative? Is this gram stain positive or negative? Identify the bacteria.Identify the bacteria.
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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.
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Classification based onClassification based on
ShapeShape Gram reactionGram reaction Oxygen Oxygen Free living & non free livingFree living & non free living
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Arranged in Micrococcus
Aerobes or clustersfacultative
StaphylococcusAnaerobes
Cocci Arranged in Streptococcus chains
Anaerobes Peptostreptococcus
Simplified Classification of Medically – Important Gram-positive Bacteria
Free living
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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
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Simplified Classification Of Medically – Simplified Classification Of Medically – Important Gram-negative BacteriaImportant Gram-negative Bacteria
Aerobes Neisseria
Cocci
Anaerobes Veillonella
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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
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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
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Capsule Present in Certain Bacteria.
Polysaccharide; occasionally protein
e.g. Bacillus anthracis
importance
a. Inhibit Phagocytosis
b. Antigenic
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Study template for bacteriaStudy template for bacteria
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Diagrams Showing The Structure Of Bacterial Diagrams Showing The Structure Of Bacterial Cell WallsCell Walls
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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
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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
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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.