This document discusses anaerobic bacteria and their characteristics. It describes how anaerobes generate energy through different metabolic pathways like anaerobic respiration and fermentation. It also discusses how obligate anaerobes are unable to tolerate oxygen and lack certain antioxidant enzymes. The document further provides details about the specimen collection, transport, culture, and identification of anaerobic bacteria. It lists some common sites of anaerobic infections and concludes with references.

2. M Luqman
M.Phil Microbiogy
0212
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3.  Bacteriology
Study of bacteria
 Bacteria;
On the basis -----how they generate energy
 Anaerobic
 Obligate
 Aerotolerant
 Aerobic
 Obligate
 Facultative
 Microaerophilic

4.  Obligate Anaerobes
 Require anoxic environment (grow either by anaerobic
respiration or fermentation)
 Can not tolerate O2
, O2 compounds & O2 radicals (O2
-, OH-
, H2O2, 1O2)
 Grow best at low Eh
 They lack
 Cytochrome System
 Superoxide Dismutase
O2
- + O2
- + 2H+ H2O2 + O2
 Catalase
2H2O2 2H2O + O2(Bubbles)
Cont’

5.  Peroxidase
H2O2 + NADH + H+ 2H2O + NAD+
 Superoxide Reductase
O2- + 2H+ rubredoxin reduced
H2O2 + rubredoxin oxidized
 Aerotolerants
 Strictly fermentative
 Can grow either in the absence or presence of O2

6.  Bacilli
 Gram –ve bacilli
 Bacteroides group (B fragilis)
 Prevotella (P melaninogenica)
 Porphyromonas
 Fusobacterium (Pleomorphic)
 Gram +ve, bacilli, non spore former
 Actinomyces (A israelli)
 Lactobacilus
 Propionibacterium, Pleomorphic (P acnes)
 Eubacterium, bifidobacterium
and arachnia (Pleomorphic)
 Gram +ve, bacilli, spore former
 Clostridium spp.
How they survive in aerobic host?
Fig 1; B fragilis
Fig 2; Fusobacterium spp.
Cont’

7.  Cocci
 Gram –ve
 Veillonella
 Gram +ve
 Peptostreptococcus
 Spirochetes
 Borrelia, treponema
Can microbiome be considered an organ of the body?
Fig 4; Peptostreptococcus spp.
Fig 3; Veillonella spp.

8.  Source may be endo or exogenous
 Exogenous (Environment)
 Soil
 Clostridium spp.
 Endogenous
 Oral anaerobes
 Intestinal anaerobes

9.  Resist exposure to oxygen
• Aerotolrance
 Evade host defence mechanism
• Prevent phagocytises
• Inactive complement
 Establish anaerobic environment
• Mixed infection with facultative or aerobic bacteria
• Signal host cells to increase O2 consumption
 Resistance to antibiotics
• Intrinsic resistance to penicillin
• Plasmids, transposons, insertion sequences
 Obtain nutrients for growth
• Protease
• Glycohydrolases

10. • Toxin
 Clostridial Toxins
• Endotoxin (Lipopolysaccharide)
 Promotes abscess formation
• Capsule
 Involve in abscess production
• Enzymes
 Nucleases
 lipases
 Proteases
 Hyaluronidase
 Colegenase
 β lactamase

11.  Brain abscesses
• Peptostreptococci and B fragilis
 Oropharyngeal infections
• Oropharyngeal anaerobes; actinomyces, Prevotella melaninogenica,
Fusobacterium species
 Pleuropulmonary infections
• Peptostreptococci; Fusobacterium species; P melaninogenica,
B fragilis in 20–25%
 Intra-abdominal infections
• Liver abscess:Mixed anaerobes in 40–90%; facultative organisms
 Abdominal abscesses
• B fragilis; other gastrointestinal flora
How they displace from their normal area to infected area?
Cont’

12.  Female genital tract infections
• Vulvar abscesses: Peptostreptococci and others
 Tubo-ovarian and pelvic abscesses:
• P bivia and P disiens; peptostreptococci; others
 Skin, soft tissue, and bone infections
• Mixed anaerobic flora
 Bacteremia
• B fragilis; peptostreptococci; clostridia; propionibacteria;`others
 Endocarditis
• B fragilis

13.  Anaerobic Specimens include:
• blood
• Aspirates from body fluids
 Pleural
 Pericardial
 Cerebrospinal
 Peritoneal
 Joint fluids
• Urine collection
• Abscess contents
• Deep aspirates from wounds

15. Use a two tube system
• 1st tube contains swab---anaerobic environment
• 2nd tube contains pre-reduced anaerobically
sterilized media.

16. Because of
• better survival of
pathogen
• greater quantity of
specimen
• less contamination
with extraneous
organism are often
achieved

17.  Anaerobic Transport Medium
 Transport Devices having anoxic environment (N2, H2, CO2)
 Syringes
 Swabs in;
• Tube containing CO2
• Carey and Blair semisolid media
 Tissue Specimen in;
• Anaerobic Jar
• Petri dish in a sealed bag

18.  Gram stain must be
performed in
laboratory....because...
 Organisms seen on
Gram stain that cannot
be grown in aerobic
cultures
 Typical morphology for
anaerobes on Gram
stain

19.  Anaerobic growth on proper media containing
antibiotic-suppressing aerobes
 Growth in anaerobic zone of fluid or agar
media
 Gas presence
 foul-smelling odour
 Characteristic colonies
 Colonies of pigmented Prevotella or
Porphyromonus spp. may fluoresce red under
ultraviolet light, and older colonies produce a
typical dark pigment

20.  Solid or Liquid media----must provide anaerobic environment-----
indicator resazurin pink (+ O2), no colour ( - O2)
 Anaerobic Jar
• Candle Jar
 reduces O2 environment
 only ↑ CO2 tension
• Gas Pak Jar
 Palladium Catalyst
 O2 reduced to CO2
 Sodium bicarbonate & Sodium borohydride
 Reacts with H2O to form H2 & CO2

21.  Methylene Blue Strip
• Indicator
 Blue ( O2 present)
 White ( O2 not present)
 Anaerobic Chamber
• Anaerobic environment
• Filled with inert gases
• (85% N2, 10% H2, 5% CO2)
 Oxy-Plate
• Oxyrase enzyme
• Combines O2 with H2

22.  Anaerobic Disposable
Plastic Bags
• Anaerobic bags
• Generate H2 & CO2
• Resazurin indicators
• Bag is heat sealed

23. Plates are checked at
> 18-24 hours for faster growing species like
Cl. Perfringens & B.fragilis & daily thereafter up to
> 5-7 days for slowly growing species like
Actinomyces, Eubacterium & propionibacterium
 Genus is determined by
- gram stain, cellular morphology, Gas-liquid chromatography
 Species determination is based on fermentation of sugars & other
biochemical determination

24.  Jonathen Cohen, William G Powderly and Steven M Opal, ‘Chapter 173;
Anaerobic Bacteria’, in Infectious Diseases, 3, 3rd edn, 2 vols. (Mosby
Elsevier, 2013), II.
 David J. Hentges, ‘Anaerobes: General Characteristics’, in Medical
Microbiology, ed. by Samuel Baron, 4th edn (Galveston (TX): University of
Texas Medical Branch at Galveston, 1996)
<http://www.ncbi.nlm.nih.gov/books/NBK7638/> [accessed 15 December
2013].
 Gerard J. Tortora, Berdell R. Funke and Christine L. Case, ‘Microbial
Growth’, in Microbiology An Introduction, 10th edn (Benjamin Cummings:
Pearson Education,, 2013).
 Jawet, Melnick and Adelberg, ‘Infections Caused by Anaerobic Bacteria’, in
Jawetz, Melnick, & Adelberg’s Medical Microbiology, 24th edn (The
McGraw-Hill Companies, 2013).