Classification of bacteria

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• Classification of bacteria
• DR.THAMINA SAYYED
• REGISTRAR
• MICROBIOLOGY
• KKUH

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Bacterial cells
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Classification System

• 3 Domains 1978 Carl Woese
• 1. Bacteria
• Unicellular prokaryotes with cell wall containing
  peptidoglycan
• 2. Archaea
• Unicellular prokaryotes with no peptodoglycan in
  cell wall
• 3. Eukarya
• Protista
• Fungi
• Plantae
• Animalia

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Comparing Prokaryotic and Eukaryotic Cells
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Taxonomic Classification Categories

• arranged in hierarchical order
• species is basic unit

Domain Kingdom Phylum or Division Class Order Fami
ly Genus Species
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Prokaryote Classification

• Technologies used to characterize
• and ID prokaryotes
• microscopic examination
• culture characteristics
• biochemical testing
• nucleic acid analysis
• combination of the above is most accurate

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• Phenotypic Genotypic classification

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Phenotypic Characteristics for Identifying
Prokaryotes

• often does not require sophisticated equipment
• can easily be done anywhere

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Microscopic Phenotypic Exam

• size and shape and arrangement
• enough information for diagnosis of certain
  infections

• Gram stain
• distinguishes between Gram and Gram bacteria
• narrows the possibilities quickly

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Microscopic Phenotypic Exam

• special stain
• allows for the distinction of microorganisms with
  unique characteristics
• capsule
• acid fast staining detects the waxy presence of
  Mycobacterium tuberculosis

Capsule staining
Acid fast staining of M. tuberculosis
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CELL WALL

• Gram positive cell wall

• Gram negative cell wall

• Consists of
• a thick, homogenous sheath of peptidoglycan 20-80
  nm thick
• tightly bound acidic polysaccharides, including
  teichoic acid and lipoteichoic acid
• cell membrane
• Retain crystal violet and stain purple

• Consists of
• an outer membrane containing lipopolysaccharide
  (LPS)
• thin shell of peptidoglycan
• periplasmic space
• inner membrane
• Lose crystal violet and stain pink from safranin
  counterstain

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Gram Positive
Gram Negative
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The Gram Stain
Gram's
Crystal
iodine
violet
Decolorise with
acetone
Gram-positives
appear purple
Counterstain with
e.g. methyl red
Gram-negatives
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appear pink
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(No Transcript)
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Gram-positive rods
Gram-positive cocci
Gram-negative rods
Gram-negative cocci
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Metabolic Phenotypic Exam

• cultural approaches
• required for positive diagnosis of infection
• isolation and ID of pathogen
• accuracy, reliability, and speed
• methods used include
• culture characteristics
• biochemical reactions process

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Serological Testing Phenotypic Exam

• serological testing uses ELISA testing
• fast and easy to use

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Classification of bacteria
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Classification of medically significant bacteria

• I.Thick rigid walled cells
• A. Free living extracellular
• 1.Gram positive
• a.Cocci Staphylococcus
  - abcess
• 
  Streptococcus - puemonia,
• 
  Pharyngitis cellulitis
• b.Spore forming rods
• Aerobic Bacillus - Anthrax
• Anaerobic Clostridium - tetanus,gas
  gangrene
• 
  botulism

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• c.Non spore forming rods (GRAM
  POSTIVE CONTD)
• 1-Non filamentous Cornybacterium
  Diphtheria
• Listeria
  - meningitis
• 2.Filamentous Actinomycetes
  Actinomycosis
• Nocardia -
  Nocardiosis

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• 2.Gram negative
• A.Cocci
  Neisseria -Gonorrhoea,
• 
  meningitis
• B.Rods
• 1.Facultative
• a. Straight
• 1.Respiratory org. Haemophillus-
  meningitis
• 
  Bordatella-Whooping cough
• 
  Legionella- Pneumonia
• 2.Zoonotic
  Brucella Brucallosis
• 
  Francisella Tularemia
• 
  Pasteurella Cellulitis
• 
  Yersinia - Plague

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• 3.enteric related (GRAM
  NEGATIVE CONTD)
• E.coli - UTI,Diarrhoea
• Enterobacter UTI
• Serratia Pneumonia
• Klebsiella Pneumonia.UTI
• Salmonella enterocolitis,typhoi
  d fever
• Shigella Enterocolitis
• Proteus UTI
• b. Curved
• Campylobacter Entericolitis
• helicobacter Gastritis,Peptic
  ulcer
• Vibrio - Cholera

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• 
  (Gram negative)
• C.Aerobic Pseudomonas
  pneumonia,UTI
• D. Anaerobic Bacteroids peritonitis
• 3.ACID FAST
• MYCOBACTERIUM - Tuberculosis
  Leprosy

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• B . Non free living obligate intracellular
  parasites
• 1.Rickettsia Rocky mountain spotted fever
• Typhus, Q fever
• 2.Chlamydia urethritis, trachoma.
  Psittacosis

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• Flexible thin walled
• Spirochaetes - Treponema
  Syphilis
• 
  Borrelia Lyme disease
• 
  Leptospira - leptospirosis
• Wall- less cells
• Mycoplasma - pneumonia

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• Subtyping Its applications
• To distinguishinguish between strains of
  different species
• Biotyping
• Serotyping
• Antimicrobial susceptibility system
• Bacteriophage typing
• Bacteriocin typing

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Genotypic Characteristics for Identifying
Prokaryotes

• the use of genotypic testing has increased with
  the availability of technology
• genotypic testing is particularly useful in the
  case of organisms that are difficult to identify
• several techniques include
• gene probes
• PCR
• sequencing rRNA

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• gene probes
• single stranded DNA that has been labeled with a
  identifiable tag, such as a fluorescent dye
• are complementary to target nucleotide sequences
• unique in DNA of pathogen

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Genotypic Characteristics used in Classifying
Prokaryotes( non culture methods)

• PCR polymerase chain reaction
• used to detect small amounts of DNA present in a
  sample (blood, food, soil)
• the PCR chain reaction is used to amplify the
  amount of DNA present

• sequencing ribosomal RNA
• of particular use for identifying prokaryotes
  impossible to grow in a culture
• focus is place on the 16S molecules of the RNA
  because of its size
• approximately 1500 nucleotides
• once the 16S molecule is sequenced, it can then
  be compared to the sequences of known organisms

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Genotypic Characteristics used in Classifying
Prokaryotes

• comparison of nucleotide sequences
• differences in DNA sequence can assist in
  determination of divergence of evolutionary path
  for organisms
• DNA hybridization
• single strands of DNA anneal
• 16S ribonucleic acid
• comparing sequence of ribosomal RNA
• relatedness to other organisms can be determined
  using numerical taxonomy
• determined by the percentage of characteristics
  two organisms have in common