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21 Cards in this Set
- Front
- Back
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Bacteroides, Prevotella, Porphyromonas & Fusobacterium sp.
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Prevalent members of the normal flora of all mucosal surfaces; they are opportunistic pathogens
Many conditions may predispose to infection, eg open wounds, diabetes, leukopenia, corticosteroids, immunosuppression, some cancers, etc. These organisms often benefit from co-infecting, e.g. P. melaninogenica + Fusobacterium cause more serious disease in rabbits than P. melaninogenica alone Many of these species form biofilms |
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Gm- anaerobes in oral disease
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16-20% of the cultivable flora of the gingival crevice area; 8-17% of cultivable flora of dental plaque
Clinical characteristics: foul-smelling discharge, infection near mucosal surface, tissue necrosis, gas in tissue, often seen in patients on aminoglycoside antibiotics, infection may follow human bite, etc Diagnosis requires isolation or demonstration by direct staining or immunofluorescence (IFA) |
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Common virulence factors
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Anti-phagocytic capsule
Also promotes abscess formation Tissue destructive enzymes Lipases, proteases, collagenases that destroy tissue and promote abscess formation Beta-lactamase production Protects self and other species in mixed infections Superoxide dismutase production Protects bacteria from toxic O2 radicals as they move out of usual niche |
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Bacteroides fragilis
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1.5-4.5 um long
Encapsulated Gut normal flora Drug resistance plasmids |
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Bacteroides fragilis - Pathogenesis
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Fimbriae and agglutinins function as adhesins
Polysaccharide capsule Antiphagocytic Responsible for abscess formation Lipopolysaccharide Antiphagocytic Stimulates leukocyte chemotaxis and migration Contains little lipid A -> weak endotoxin activity Oxygen tolerance Superoxide dismutase Catalase Degradative enzymes, eg neuraminidase, hyaluronidase, DNAses, proteases Histolytic (tissue destruction) Inactivation of immunoglobulins (IgA, IgM, IgG proteases) Some drug resistance plasmids |
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Bacteroides fragilis Clinical syndromes
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Abscess formation in normally sterile sites
Bacteremia Intraabdominal infections: more than 80% caused by B. fragilis Gynecological infections: polymicrobial anaerobic infections with B. fragilis frequently causing abscesses Skin and soft tissue infections: most commonly associated with B. fragilis; Gm- anaerobes gain access to sites via bites or trauma Respiratory tract: polymicrobial infections including non-fragilis Bacteroides |
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Prevotella melaninogenica
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Short coccoid rods
Produces black pigment Requires vitamin K Weak endotoxin Other sp.: P. oralis |
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Porphyromonas gingivalis
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Gram negative, short, rod-shaped, pleiomorphic, anaerobic bacteria
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Porphyromonas gingivalis
virulence factors and pathogenesis |
Virulence factors
Fimbriae (adherence) Capsule (antiphagocytic) Many degradative enzymes (proteases, collagenase, hemolysin) Pathogenesis Aggressive periodontal pathogen in humans and animals Found almost exclusively at subgingival sites |
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Fusobacterium nucleatum
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Gram-negative anaerobe
Spindle shape, with sharp ends Similar to Bacteroides 5-10um long Butyric acid fermenters |
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Fusobacterium nucleatum Symptoms and diseases
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Gut normal flora
Pleuropulmonary infections Tropical skin ulcers Gingivitis Cause of trench mouth (common during WWI) Ulcerative disease of the gums associated with poor oral hygiene, fatigue, malnutrition, heavy smoking, etc. |
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F. nucleatum + Treponema vincentii -> Vincent’s Angina
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Necrotizing infection of the pharynx
Unilateral with same side earache Bleeding ulcer on one tonsil Antibiotics and debridement recommended |
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Fusobacterium necrophorum
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Normal throat flora
Lemierre’s syndrome very rare today but common before penicillin Rising incidence in children may result from encouraged reduced use of antibiotics starts with sore throat, viral cause usually is suspected, hence rarely treated with antibiotics Potentially leads to severe disease: high fever spikes, septicemia, abscesses on organs Predisposition to abscess formation, in liver, spleen and muscles Pulmonary lesions |
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Leptotrichia sp.
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Gm- thin, filamentous,
non-motile bacteria Related to Fusobacterium sp. Aerotolerant anaerobes, fastidious slow-growers Several species cause disease in humans: L. amnionii L. trevisanii L. sanguinegens L. buccalis Associated disease: periodontal disease, bacteremia, serious systemic disease in immunocompromised patients, disease of reproductive tract, etc |
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Campylobacter
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Microaerophilic
grows best at reduced O2 and CO2 concentrations of 10% Non-fermenting Motile curved rods Single polar flagellum Small: will pass through .65 uM filters that filter out most enteric bacteria Many serotypes based on O (LPS O-side chain) and H (surface proteins) antigens Five different species of Campylobacter may be isolated from clinical specimens |
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Campy - Epidemiology
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commensal flora of birds
many other animals serve as vehicles for human infection usually through the consumption of contaminated food the major cause of food-borne bacterial infection of humans |
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campy virulence factors
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Virulence factors
Enterotoxin Endotoxin Adhesins Ability to penetrate cells Intracellular survival |
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campy clinical significance
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Gastroenteritis
Caused mainly by C. jejuni and C. coli Systemic infections Usually due to C. fetus ssp. fetus Occurs in debilitated or immunocompromised individuals |
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campy pathogenesis
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invades epithelium of lower small intestine
provokes inflammatory response that may be responsible for many of the symptoms Symptoms start 1-10 days after ingestion with crampy abdominal pain, bloody diarrhea, fever Untreated patients may excrete Campy for months |
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C. jejuni pathogenesis
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Antecedent to Guillain-Barré syndrome
ascending paralysis immune in etiology Stems from autoimmune cross-reactivity with Campylobacter antigens |
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campy control (treatment)
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No vaccine
Treatment macrolides and quinolones antibiotic resistance is common |
