anaerobes

• medically important anaerobes (non-spore forming)

  • gram negative
  • Bacteroides spp.
  • Prevotella spp.
  • Fusobacterium spp.
  • Porphyromonas spp.
  • gram positive
  • Cutibacterium spp.
• non-spore forming anaerobes

  • part of normal flora in the mucosal surfaces, GI, and GU tract
  • grow in the absence of oxygen
  • microorganisms vary in their ability to tolerate oxygen
  • hospital do NOT routinely run MICs for anaerobes
• gram negative (not spore-forming) anaerobic infections

  • aspiration pneumonia
  • intra-abdominal infections
  • abscesses (usually polymicrobial)
  • pelvic infections
  • appendicitis, diverticulitis
  • skin infections
  • bites
  • oral/dental infections
  • rare --> bacteremia
  • diagnosis typically via culture
• anaerobic GPC - cutibacterium acnes

  • common colonizer
  • formerly known Propionibacterium acnes
  • in inpatient setting, common contaminant in blood cultures and generally not treated
  • exception: multiple positive blood cxs w/ same organism
  • in cases when it causes true infection, it is most commonly implicated in acne vulgaris
• medically important anaerobes (spore forming)

  • Clostridium spp. (gram + rods)
  • Clostridium difficile
  • Clostridium perfringens
• clostridium difficile

  • largely acquired as a nosocomial pathogen from hospitals and nursing homes
  • transmission: shed in feces --> spores survive on contaminated surfaces (toilets, commodes, bath, tubs, etc.) --> healthcare personnel --> transmission to other patients
• clostridium difficile toxins

  • toxin A and B
  • both toxin A (enterotoxin) and toxin B (cytotoxin) stimulate fluid secretion and cause mucosal damage and inflammation
  • disruption of the tight cell-to-cel junction, increased permeability of the intestinal wall, and diarrhea
  • 10 - 30 % of C. difficile strains are non-toxin producing and are colonizers
  • C. difficile associated colitis --> diarrhea
  • laboratory diagnosis: PCR assay for the presence of C. diff toxin in stool
• clostridium perfringens

  • spores commonly found in the environment
  • various toxins
  • alpha toxin (lecithinase) --> lyses erythrocytes, platelets, leukocytes, and endothelial cells --> hemolysis, increased vascular permeability and bleeding, tissue destruction
  • beta toxin --> intestinal stasis and loss of mucosa --> necrotizing enteritis
  • epsilon toxin --> increases vascular permeability of the GI wall
  • iota toxin --> has necrotic activity and increases vascular permeability
  • enterotoxin --> activated when bacteria sporulate --> altered cell membrane permeability and loss of fluids and ions
• clostridium perfringens infections

  • soft tissue infections ranging from localized to very severe and necrotizing ("flesh-eating bacteria")
  • diagnosis: culture
  • this is a life-threatening infection