Home » Microbiology » Bacteroides and Prevotella

Bacteroides and Prevotella

Bacteroides and Prevotella are gram negative rods, non- spore forming, encapsulated, anaerobic and non-motile bacteria.

Route of entry
Part of normal flora, colonize human colon and vagina.

Pathogenesis

•    Infections are endogenous, following a break in the mucosal surface, organism causes infections.
•    Local abscesses are formed at the site of mucosal breaks.
•    Metastatic abscesses form by hematogenous spread to other organs.
•    Lung abscesses occur by aspiration of oral flora.
•    Facultative anaerobic conditions are required.
•    Endotoxin (lipopolysaccharide) produces sepsis and septic shock
•    Enzymes causes tissue damage:

  • Hyaluronidese
  • Collagenose
  • Phospholipase

•    Polysaccharide capsule is antiphagocytic

Virulence Factors
•    Capsule
•    Endotoxin-LPS
•    Hyaluronidase
•    Collagenase.
•    Phospholipase
•    B- lactamase

Predisposing Factors
•    Surgery
•    Trauma
•    Chronic disease
•    Local tissue necrosis
•    Impaired blood supply
•    Growth of facultative anaerobes at the site

Clinical Symptoms  
•    Intra-abdominal infections
•    Pelvic abscesses
•    Necrotizing bacteremia

Bacillus Fragilis causes disease below the diaphragm and B. melaninogenicus causes disease above the diaphragm.

Lab Diagnosis

Specimen
•    Pus
•    Exudates
•    Inflected tissue
•    Blood

Microscopy

Important features observed under microscope include:
•    Gram- negative rods
•    Non- spore forming
•    Capsulate
•    Anaerobic
•    Non- Motile

Bacteroides growing on blood agar
Bacteroides growing on blood agar

Culture

Blood agar plus vancomycin    
Grey, glistening colonies are formed which are non- haemolytic

Biochemical Tests
•     Sugar fermentation
•    Organic acid production detected by gas chromatography

Serological Tests
•    PCR

Treatment
•    Penicillin resistant because of B- lactamose
•    Metronidazole with clindamycin is given

Check Also

Macroconidia of Epidermophyton floccosum and filamentous hyphae

Cutaneous Mycoses

Cutaneous mycoses are the diseases caused by fungi and involving the skin, hair and nails. …