45 Anaerobes I Flashcards
anaerobes fail to grow on the surface of what?
solid media in air (18% O2) supplemented w/5-10% CO2
moderate anaerobe: 2-8% O2 (eg propionibacterium, clostridium)
strict anaerobe:
probiotics containing anaerobes (eg _____ & _______) are ingested by many people to maintain indigenous anaerobe flora.
lactobacilli, bifidobacteria
majority of anaerobic infections are endogenous or exogenous?
endogenous, but most exogenous infections are caused by clostridia
what is the disease assoc w/each?: C.tetani C.botulinum C.perfringens C.difficile
C.tetani - tetanus
C.botulinum - botulism
C.perfringens - food poisoning, cellulitis, myositis, myonecrosis
C.difficile - diarrhea, pseudomembraneous colitis
body parts w/highest [Anaerobes]?
teeth, gingiba, colon, vagina (not stomach because of acidic pH)
which anaerobic bacteria is the outlier that colonizes the skin?
propironibacterium
infection w/a facultative anaerobe does what to anaerobes?
uses up the already diminished O2 supply and thus encouraces growth of obligate anaerobes
clinical and lab clues for anaerobic infections?
- foul odor from lesion or discharge
- infection near mucosal surface
- tissue necrosis, gangrene, abscess formation w/gas
- assoc w/malignancy
- diarrhea assoc w/Abx tx
- massive hemolysis
- sulfur granules in discharge
- unique gram stain morphology
- fail to grow aerobically
problems w/identification of anaerobic infections?
- derived from normal flora - is it a pathogen or contaminant? Tell by clinical sxs
- death by air
- slow growth of orgs (due to inefficiency of fermentation)
appropriate specimens for anaerobic cx?
- collected in a sterile manner
- tissue biopsies, surgical specimens, needle aspirates, blood
NOT: contaminated w/orgs colonizing the skin and mucosal surfaces like swabs, sputum, or urines
anaerobic, non-spore forming GP rods?
actinomyces, lactobacillus, mobiluncus, propionibacterium
anaerobic GP cocci?
peptostreptococcus
peptostreptococcus disease?
Polymicrobial infections:
- Sinusitis, pleuropulm infecteions, brain abscesses
- intraabd. Infections
- endometritis, pelvic abscesses
- cellulitis, necrotizing fasciitis
- osteomyelitis
peptostreptococcus treatment?
- usu susceptible to penicillin but tx should cover all orgs of infection – generally combination therapy: beta-lactam-beta-lactamase inhibitor, can include metronidazole combined w/extended spectrum cephalosporin, aminoglycoside, or FQ
- empiric therapy adjusted when results of susceptibility tests available
actinomyces general characteristics?
- delicate filamentous structure
- sulfur granules colony
actinomyces pathogenesis?
- chronic lesions that become suppurative and form abscesses connected by sinus tracts
- involves disruption of mucosal barrier (surgery like dental procedures/GI surgery, trauma, aspiration, foreign body like IUD, diverticulitis, appendicitis)
actinomyces disease?
Actinomycosis
- cerebral
- cervicofacial
- thoracic
- abdominal
- pelvic
Chronic infection w/relapsing/remitting course assoc w/abscess, draining sinuses, fibrosis
- often mistaken for malignancy
actinomyces treatment?
Abx: penicicllin; erythromycin or clindamycin
Surgical debridement (liver is highly vascular, thus [Abx] is high enough and don’t need debridement)
lactobacillus general characteristics?
long, thin GP rods (non-spore-forming)
mostly clinically insignificant (found in probiotics)
lactobacillus disease?
may cause septicemia in immunocompromised or endocarditis in ppl w/underlying valve abnormalities
- bloodstream infection of lactobacillus causing endocarditis
lactobacillus treatment?
Abx: high [penicillin] and gentamicin (pcn or a combo of Abx) – bacteria resistant to vancomycin
mobiluncus general characteristics?
curved rod, GN or G-variable
colonizes genital tract
mobiluncus disease? dx? tx?
- multiplies to high numbers in women w/ bacterial vaginosis (may be impt cause or marker of disease)
- clue cells suggest Dx of BV
- tx of BV w/metronidazole (even though Mobiluncus itself is resistant)
propionibacterium general characteristics?
clumps of short rods
- most commonly isolated anaerobe in microbiology lab
propionibacterium disease and treatment?
- acne
- invasive infections in pts w/indwelling foreign bodies: prosthetic heart valves, prosthetic joints, indwelling catheters
- topical benzoyl peroxide
- penicillin, tetracyclines, erythromycin, clindamycin
bacteroides fragillis general characteristics?
anaerobic GN rod w/LPS but lacks endotoxin activity
most common clinically significant anaerobe
grows easily in culture (pleimorphic GNRs w/inflammatory cells)
B.fragilis virulence?
polysaccharide capsule prevents phagocytosis and stimulates abscess formation
other factors too
B.fragilis disease? dx? treatment?
abscess formation:
- intraabdominal infections
- PID and endometritis
- surgical wound infections
- S/ST infections after surgery or trauma
dx: grows well in culture, always consider post-op (tends to be necrotic and thus crepitus present)
tx: - resistant to penicillins
- metronidazole plus active vs other organisms in infection (polymicrobial)
- surgical debridement
fusobacterium general characteristics?
anaerobic GNR
- normal flora of oropharynx, GI and GU, long, filamentous
fusobacterium pathogenesis?
- untreated dental caries extend to dental alveoli and result in osteomyelitis or may spread into mandible
- spreads to thorax via parapharyngeal spaces
fusobacterium disease?
- acute necrotizing ulcerative gingivitis (“trench mouth”)
- pharyngitis, tonsillitis (Vincent’s angina)
- Jugular venous thrombophlebitis (Lemierre’s syndrome) = pharyngitis complicated by peritonsillar abscess w/subsequent spread through pharyngeal spaces inferiorly into internal jugular localized thrombophlebitis clots embolize to other organs (**lung) and form abscesses at those sites
fusobacterium treatment?
- penicillin and clindamycin
For Lemierre’s: B-lactam-B-lactamase inhibitor and debridement of abscess
