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
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
Bacteroides and Prevotella – howMed
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:
• 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
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