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Anaerobic Bacteria Neglected but Important
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Neglected in diagnostic labs- but they
outnumber the aerobic bacteria including
most sites of human and animal body.
Mouth and skin -10-30 times more frequent
than aerobic bacteria.
The numbers of anaerobes have been
estimated to be 10 4-10 5/ml in small
intestine,10 8/ml in saliva and 10 11/g in the
colon
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Aerobes and facultative anaerobes have
metabolic systems listed below, whereas
anaerobic bacteria do not
▪ Cytochrome system of metabolism of oxygen.
▪ Superoxide dismutase, which catalyses the following
reaction:
▪ O-2+O-2----H2O2+O2
▪ Catalase, which catalyses the following reaction.
▪ 2H2O2----2H2O+O2 (gas bubbles).
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7. Anaerobic bacteria do not have cytochrome
systems for metabolism.
Less fastidious anaerobes have low levels of
superoxide dismutase and may not have
catalase.
Obligate anaerobes usually lack superoxide
dismutase and catalase and are susceptible to
lethal effects of oxygen radicals.
Most human infections are caused by
moderately obligate anaerobes.
Ability to tolerate oxygen varies from species to
species.
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They cause following infections
Divided into Graminfections,wound
Genital positive and Gram
negative cocci
infections,gangrenous
Peptococci,peptostreptococci.-cocci small
appendicitis,urinary tract
size 0.2-2.5 µ. Many aerotolerent.
infections,osteomyelitis,absc
Normal flora of vagina,intestinesand mouth.
ess in the brain,lungs and
Peptostreptococcusorgans
other internal anaerobicuspuerperal sepsis.
P.magnus-Abscess
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GNC of varying sizes occurring as
diplococci,short chains or groups
They are normal inhabitants of
mouth,intestinal and genital tract
All anaerobic cocci are generally sensitive to
penicillin,chloramphenicol,and
metronidazole and resistant to streptomycin
and gentamicin
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BACTERIAL VAGINOSIS
Eubacterium- periodintitis
POLYMICROBIAL INFECTION OF
Lactobacillus usually non CHARACTERIZED BY THIN
VAGINA pathogenic
MALODOUROUS VAGINAL
L.catenaformae-bronchopulmonary
DISCHARGE
KOH TEST
infections
VAGINAL PH IS MORE THAN 4.5
CLUE CELL SEEN
Bifidobacterium-branching MICROSCOPICALLY
IN FRAM STAINED SMEARSMobiluncus-M.mulieris,M.curtisii-Bacterial
vaginosis.
What is bacterial vaginosis?
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Large group of GNB appear as slender rods or
cocobacilli.
Normal commensal of intestine.
Normal stool-1011 B.fragilis/gram.
Commonly isolatedB.fragilis,B.ovatus,B.distasonis,B.vulgatus,B.
thetaiotamicron and others.
Contamination by contents of colon where
they may cause suppuration-perotinitis
18. Constitutes less than 10% of Bacteroides species
in the normal colon, however, is the most
common isolate of anaerobes.
Major virulence factor: capsular
polysaccharides, which may cause abscess
formation when injected into the rat abdomen.
Resistant to penicillin.
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Classification is based on colonial and
biochemical features and characteristic short
chain fatty acid patterns in gas liquid
chromatography.
Associated with anaerobic coccipeptostreptococci and others.
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GNB-slender rods and cocobacilli
Common-P.melaninogenica.
Found in lung and brain abscess,in empyema
and in pelvic inflammatory diseases,and
tuboverian abscess.
Often polymicrobial –
peptostreptococci,anaerobic gram positive
rods and fusobacterium species.
Black colonies produced by this.
Colonies show-red fluorescence in UV rays
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Pleomorphic GNB.
Most species produce butyric acid and
convert threonine to propionic acid.
Isolated from mixed bacterial infections-oral
infection pleuropulmonary sepsis.
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Now-a-days techniques are simplified for
their isolation & identification.
Endogenous infections.
Trauma, tissue
Precipitating factors are there.
necrosis,foregin
Anaerobicdiabetes, malnutrition,
body, infections-polymicrobial
malignancy, prolonged
treatment with
aminoglycosides
25. Site and type of infection
Bacteria commonly responsible
Central nervous system-brain abscess
B.fragilis,peptostreptococcus
ENT-chronic sinusitis,otitis
media,mastoiditis,orbital cellulitis
Fusobacteria
Mouth and jaw-ulcerative gingivitis,dental
abscess,cellulitis,abscess or sinus of jaw
Fusobacteria,spirochetes,mouth
anaerobes,actinomycetes,
Respiratory-aspiration pneumonia,lung
abscess,bronchiectasis,empyema
Fusobacteria,P.melaninogenica,anaerobic
cocci,B.fragilis
Abdominal-shbphrenic,hepatic
abscess,appenditicitis,peritonitis,ischiorec
tal abscess,wound infection after
colorectal surgery
B.Fragilis
Female genitialia-purperal sepsis etc
P.melaninogenica,anaerobic cocci,B.fragilis
Skin and soft tissue
Anaerobic cocci
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Interpretation should be done cautiously.
Avoid resident flora contamination.
Avoid or minimise the exposure with oxygen.
In laboratory exposure should me limited to
minimum
Gram staining shows large variety of different
organisms and numerous pus cells
Occasionally-brain abscess-single organism.
UV examination-bright red fluorescence?
Gas liquid chromatography
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Freshly prepared blood agar with
neomycin,yeast extract,hemin and vitamin K
is adequate
Incubated at 37oC with 10%CO2.
Gas pak Jar is used
Examine plates after 24-48 hrs
Parallel aerobic cultures shd. Be always put.
31. Methods for excluding oxygen
1. Fluid media containing
fresh animal tissue or 0.1%
agar containing a reducing
agent, thioglycollate.
2. Anaerobic jar
3. Anaerobic glove chamber