Non sporing anaerobes

Growth pattern depending upon oxygen requirement

Introduction

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

Classification

Earlier-coloney morphology,biochemical reactions and antibiotic sensitivity pattern.

Current classification-based on DNA base composition and analysis of fatty acids, end products of metabolism

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).

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.

Cocci

Gram positive

peptostreptococcus

peptococcus

Gram negative

Veillonella

Bacilli

Endospore forming

Clostridia

EUBACTERIUMPROPIONIBACTERIUM

LACTOBACILLUSMOBILUNCUS

BIFIDOBACTERIUMACTINOMYCETS

BACTER OIDESPREVOTELLA

PORPHYROMONASFUSOBACTERIUM

LEPTOTRICHA

Spirochetes

Spirochetes

Treponema Borrelia

Divided into Gram positive and Gram negative cocci

Peptococci,peptostreptococci.-cocci small size 0.2-2.5 µ. Many aerotolerent.

Normal flora of vagina,intestines and mouth.

Peptostreptococcus anaerobicus-puerperal sepsis.

P.magnus-Abscess

Anaerobic cocciThey cause following

infectionsGenital infections,wound

infections,gangrenous appendicitis,urinary tract infections,osteomyelitis,abscess in the brain,lungs and other internal organs

Veillonellae

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

Gram positive bacilli

Eubacterium- periodintitis Lactobacillus usually non pathogenic L.catenaformae-bronchopulmonary

infections Bifidobacterium-branching Mobiluncus-M.mulieris,M.curtisii-

Bacterial vaginosis. What is bacterial vaginosis?

BACTERIAL VAGINOSIS

POLYMICROBIAL INFECTION OF VAGINA CHARACTERIZED BY THIN

MALODOUROUS VAGINAL DISCHARGEKOH TEST

VAGINAL PH IS MORE THAN 4.5CLUE CELL SEEN MICROSCOPICALLY

IN FRAM STAINED SMEARS-

Bifidobacterium

Bacteroids

Large group of GNB appear as slender rods or cocobacilli.

Normal commensal of intestine. Normal stool-1011 B.fragilis/gram. Commonly isolated-

B.fragilis,B.ovatus,B.distasonis,B.vulgatus,B.thetaiotamicron and others.

Contamination by contents of colon where they may cause suppuration-perotinitis

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.

Classification is based on colonial and biochemical features and characteristic short chain fatty acid patterns in gas liquid chromatography.

Associated with anaerobic cocci-peptostreptococci and others.

Prevotella

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

Porphyromonas

Normal oral commensal. Gingival, periapical tooth infections. More commonly-

breast,axillary,perianal and male genital infections

Fusobacteria

Pleomorphic GNB. Most species produce butyric acid

and convert threonine to propionic acid.

Isolated from mixed bacterial infections-oral infection pleuropulmonary sepsis.

L.buccalis-vincent’s fusiform bacillus-fusobacterium fusiformae

It causes Vincents angina-oropharyngitis

Leptotrichia

Anaerobic infections

Now-a-days techniques are simplified for their isolation & identification.

Endogenous infections. Precipitating factors are there. Anaerobic infections-polymicrobial

Trauma, tissue necrosis,foregin body, diabetes, malnutrition,malignancy, prolonged

treatment with aminoglycosides

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,ischiorectal 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

Features that suggests anaerobic infections

Pus-putrid-foul smelling. Pronounced cellulitis.

Laboratory diagnosis

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

Swabs discouraged for anaerobic cultures

Culture

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.

1. Fluid media containing fresh animal tissue or 0.1% agar containing a reducing agent, thioglycollate.

3. Anaerobic glove chamber

2. Anaerobic jar

Methods for excluding oxygen

Thank you !