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36 Cards in this Set

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Drugs

Metronidazole, clindamycin, fidaxomicin, chloramphenicol (rare in US)

Metronidazole

metabolized inside anaerobic bacteria, damages bacterial DNA




IV and PO forms; can penetrate CNS




most effective against Gm- anaerobes, Clostridia spp., Gardnerella vaginalis, Helicobacter pylori

Metronidazole S/E

nausea, diarrhea, metallic taste, seizures, peripheral neuropathy, disulfiram-like rxn with alcohol

Metronidazole indications

anaerobic infections, AB-associated colitis, bacterial vaginosis, H. pylori peptic ulcers

Clindamycin

binds to 50s ribosomal subunit, facilitates opsonization, phagocytosis, intracellular killing




IV and PO forms, does NOT penetrate CNS

Clindamycin activity

most anaerobes outside CNS, increased resistance among Bacteroides fragilis




most aerobic Gm+ (pneumococci, strep, MSSAs, some CA-MRSA)

Clindamycin S/E

AB-associated diarrhea due to Clostridium difficile; anorexia, N/V; neutropenia and thrombocytopenia rare

Chloramphenicol

binds to 50s subunit; active vs. most anaerobes and several aerobes




severe s/e: aplastic anemia and neonatal toxicity (Grey baby syndrome), effective for some rickettsial diseases

O2 and anaerobes

anaerobes don't have superoxide dismutase (can't break down superoxide)

Anaerobic infections

causes: breakdown of normal mucosal barrier (poor blood supply, trauma, tissue destruction, necrosis)




many species normally involved

Clostridium species

spore-forming, gram-positive rods "box cars"


in soil and animal intestines




release protein toxins, some invade tissues to cause wounds and abscesses



Clostridium botulinum

heat-resistant spores release neurotoxin types A-G that prevent release of NT acetylcholine

Food-borne botulism

flaccid paralysis 12-36 h post-ingestion; CNs affected first (diplopia, blurred vision, swallowing difficulty)




descending paralysis, death from resp. failure

Infant botulism

Rare, large intestine colonized w/ slow absorption of toxin




hypotonia, weak cry and suck reflex

Wound botulism

rare, toxins produced at wound site and absorbed into tissues

Clostridium tetani

Tetanospasmin = major toxin that inhibits NT release and normal inhibitory input causing spastic paralysis; lock jaw followed by descending disease




Rx: antitoxin, pen G, wound care, support


Prevent: tetanus toxoid vaccine



Clostridium perfringens

Food poisoning: meat poorly cooked then re-warmed; enterotoxin produced that acts as a superAg in GI tract - watery diarrhea, crampy ab pain




Gas gangrene: lecithinase alpha-toxin damages cell membranes; wound pain, discoloration, crepitation, myonecrosis

Clostridium difficile infection

dormant in large bowel; normal GI flora suppressed by AB but resistance allows overgrowth, secretion of exotoxins




toxins inactive Rho family of guanosine TPs

Clostridium difficile: epidemiology

toxinotype III BI/NAP1/027 strain - mortality rates 3X those of less virulent strains

C. difficile risk factors

AB use: ampicillin, amoxicillin, cephalosporins, clindamycin




old age, IBD, organ transplant, chemo, CKD, immunodeficiency

C. difficile clinical manifestations

mild: afebrile, mild abd. pain, labs OK


moderate: non-bloody diarrhea, mod. abd pain, nausea w/ occasional vomiting, dehydration


severe: severe or bloody diarrhea, pseudomembranous colitis, severe abd. pain, tenderness, vomiting


complicated: toxic megacolon, perotinitis, resp. distress, hemodynamic instability

Clostridium difficile Rx

Mild: Metronidazole po


Moderate: Metronidazole po, vancomycin po


Severe: hospitalization, vancomycin, metronidazole IV



C. difficlile-assoc. diarrhea therapy

Fidaxomicin: macrocyclic AB that inhibits protein synthesis




not active against Gm- anaerobes or aerobes (gut flora)

Gram-positive anaerobic cocci

pepto-, strepto-, peptrostreptococcus




normal: mouth, skin, GI tract, vagina


infections: aspiration pneumonia, surgical wounds, intraabdominal, female pelvic



Gram-negative anaerobic cocci

Veillonella




normal: mouth, vagina


infections: human bite wounds, PID

Anaerobic cocci Rx

penicillins, metronidazole, clindamycin

Bacteroides fragilis

non-sporulating Gm-neg. bacillus




forms abcesses, bacteremia




normal colon flora




infections: intraabdominal inf., pelvic, decubitus ulcers, diabetic foot ulcers

Bacteroides fragilis Rx

metronidazole, beta-lactam/beta-lactamase inhibitor combinations, carbapenems

Prevotella

non-sporulating anaerobe, Gm-




oropharynx, GI and GU tracts


mouth, lung, intraabdominal infections

Fusobacteria

non-sporulating anaerobe, Gm-




oropharynx, GI and GU tracts


sinusitis, chronic otitis, dental, can cause brain abscess

Propionibacterium acnes

non-sporulating anaerobe, Gm+




skin flora, causes acne

Actinomyces

aerobe that grows best anaerobically; filamentous, branching, Gm+




infections: head/neck, chest and abdomen, draining sinuses




Rx: high dose Pen G

Head & neck infections

Fusobacterium, Prevotella, Gm-pos. cocci




Infections: dental, chronic sinusitis, chronic otitis, brain abscesses

Pleuropulmonary infections

Fusobacterium, Prevotella, Gm-pos. cocci




Infections: pneumonia with lung abscess cavity, empyema

Intraabdominal infections

Bacteroides, Clostridium, Fusobacterium, Gram-positive cocci, aerobes




infections: abscesses and/or peritonitis

OB-GYN infections

Bacteroides, Gm-pos. cocci, Clostridium




infections: tubo-ovarian abscess, pelvic abscess, septic abortion, endometritis, post-op