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19 Cards in this Set
- Front
- Back
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General characteristics of G- anaerobes
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Normal flora
opportunistic pathogens benefit from co-infecting many form bifilms |
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Common virulence factors of G- anaerobs
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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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1.5-4.5 um long
Encapsulated Gut normal flora Drug resistance plasmids |
Bacteroides fragilis
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Pathogenesis of Bacteroides fragilis
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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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clinical syndromes of Bacteroides fragilis
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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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Short coccoid rods
Produces black pigment Requires vitamin K Weak endotoxin Other sp.: P. oralis |
Prevotella melaninogenica
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Gram negative, short, rod-shaped, pleiomorphic, anaerobic bacteria
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Porphyromonas gingivalis
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Virulence factors of Porphyromonas gingivalis
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Fimbriae (adherence)
Capsule (antiphagocytic) Many degradative enzymes (proteases, collagenase, hemolysin) |
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Pathogenesis of Porphyromonas gingivalis
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Aggressive periodontal pathogen in humans and animals
Found almost exclusively at subgingival sites |
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Gram-negative anaerobe
Spindle shape, with sharp ends Similar to Bacteroides 5-10um long Butyric acid fermenters |
Fusobacterium nucleatum
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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. |
Fusobacterium nucleatum
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Necrotizing infection of the pharynx
Unilateral with same side earache Bleeding ulcer on one tonsil Antibiotics and debridement recommended F. nucleatum + Treponema vincentii |
Vincent’s Angina
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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 |
Fusobacterium necrophorum
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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. |
Leptotrichia
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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 |
Campylobacter
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commensal flora of birds
many other animals serve as vehicles for human infection usually through he consumption of contaminated food the major cause of food-borne bacterial infection of humans |
Campylobacter
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Sites of infetion of Campylobater
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Small and Large intestine
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Virulence factors
Enterotoxin Endotoxin Adhesins Ability to penetrate cells Intracellular survival |
Campylobacter
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Clinical significance
Gastroenteritis Caused mainly by C. jejuni and C. coli Systemic infections Usually due to C. fetus ssp. fetus Occurs in debilitated or immunocompromised individuals |
Campylobacter
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