Anaerobic Infections and Normal Flora Flashcards
(29 cards)
Common Features of Anaerobic Infections
Abscesses originate from native flora.
Characterized by foul-smelling, gas in necrotic tissue
Look for predisposing conditions.
Mixed infections with at least one anaerobe
Depending on whether the infection is located above or below the diaphragm what distinction can be made?
B. fragilis is located below the diaphragm and is penicillin resistant.
Why does knowledge of local flora aid in empirical therapy?
Because anaerobic cultures more than 48 hours
What is used for identification and characterization of clinically important anaerobic bacteria?
Gram stain, morphology and production of unusual fatty acids
Bacteroides fragilis
Most common Gram - rod, pleiomorphic. Large numbers in intestine, results in septicemia, Penicillin Resistant. C. perfringens and B fragilis cause almost all anaerobic septicemias.
Prevotella melaniongenicus
Gram - rod, oral infections, peridontal disease, black pigment grown on bld agar
Fusobacterium
Gram - rod, tapered ends and very thin, penicillin and O2 sensitive. Oral infections, lung abcesses
What are the anaerobic gram negative rods that cause infection?
Bacteroides fragilis, prevotella melaniogenicus, Fusobacterium
What are the non-spore forming anaerobic gram positive rods that cause infection?
Bifidobacterium, Corynebacterium, Lactobacillus, Actinomyces, Clostridia
Bifidobacterium
Gram + rod, branching, large numbers in large intestine, rarely cause infection
Corynebacterium
Pleomorphic rod, normal inhabitant of skin not usually cause infection
Lactobacillus
Gram + rod, normal intestinal flora, important in maintaining low pH coverts sugar to lactic acid
Actinomyces
Gram + branching rod, dental abscesses, sinus tracts, sulfur granules!
Peptostreptococcus
Gram + cocci chains, anaerobic. normal flora of mouth, widely involved in infections
Anaerobic Methodology
Use very little air exposure, gram stain important, anticipate mixed infections. Do not submit oral or fecal cultures for anaerobes.
Media include: thioglycollate broth, which removes oxygen from liquid media
Treatment for Anaerobic infections
Penicillin, except b. fragilis, clindamycin, surgical drainage in abscesses
What is the importance of normal flora?
Protection from pathogens.
Nutritional function - produce B and K vit
Bacterial overgrowth in small bowel can cause fat malabsorption and B12 deficiency
Bacterial overgrowth in small bowel can cause…
fat malabsorption and B12 deficiency
Four Aerobes in Normal Mouth flora
Viridans streptococci - Gram + rod
Neisseria - Gram - diplococci
Diphtheroids - Gram + pleomorphic rod
S. epidermidis - Gram + cocci grape clusters
Virdians streptococci
Gram + rod, may be in chains. predominant in mouth, most common cause of subacute bacterial endocarditis
Neisseria
Gram - diplococci, some species are non-pathogens
Diptheriods
pleomorphic Gram + rods, most common contaminants of blood cultures since also colonize skin. Rare cases of infection
Staphylococcus Epidermidis
Gram + cocci, grape-like clusters, coagulase negative
Anaerobes in Oral Cavity
DO NOT extend below trachea, aspiration pneumonia
Fusobacterium - Gram - cigar rod, penicillin sensitive
Prevotella - Gram - rod penicillin sensitive
Anaerobic streptococci - Gram + chain, penicillin sensitive
Actinomyces - Gram + branching rod
