Susceptibility of Anaerobic Bacteria to 23 Antimicrobial Agents

Abstract

The antimicrobial susceptibility of 492 anaerobic bacteria, the majority of which were. recent clinical isolates, was determined by the agar dilution technique. Penicillin G was active against most of the strains tested at 32 U or less/ ml, but only 72% ofBacteroides fragilis strains were susceptible at this level and 9% required 256 U or more/ml. Ampicillin was effective against most of the strains except B. fragilis at 16 ug or less/ml. Amoxicillin was active against only 31% of B. fragilis, 76% of other Bacteroides species, and 67% of Fusobacterium species at 8 ,ug/ml. Two new penicillins, mezlocillin and azlocillin, were similar to ampicillin in their activity. Carbenicillin and ticarcillin inhibited all but a few strains at 128 ,ug or less/ml. BLP 1654 was somewhat more active than penicillin G against B. fragilis but had similar activity against other anaerobes. Cephalothin was inactive against B. fragilis, and only 65% of other Bacteroides species were inhibited by 32 ug or less/ml. It was effective against all other anaerobes at that level. Cefamandole showed somewhat greater activity than cephalothin against B. fragilis but generally less activity against gram-positive organisms. Cefazaflur (SKF 59962) was comparable to cephalothin against B.firagilis. Cefoxitin was distinctly more active than cephalothin against B.fragilis. These latter two agents were less active than cephalothin against the gram-positive anaerobes. Chloramphenicol remains active against anaerobic bacteria at 16 ,ug or less/ml, with rare exceptions. Thiamphenicol was similar to chloramphenicol in its activity. Clindamycin was very active against most ofthe anaerobes at 8 ,ug or less/ml. Erythromycin and josamycin were also tested, with josamycin showing greater activity against B. fragilis than either erythromycin or clindamycin. A new oligosaccharide, everninomicin B, was less active than clindamycin against B. fragilis but more active against clostridia and some of the other strains tested. Most of the groups of bacteria tested demonstrated a trend toward resistance to tetracycline. Doxycyline and minocycline were somewhat more active than was tetracycline. Metronidazole was active against the majority of the anaerobes tested; resistance ws demonstrated by some of the gram-positive cocci and gram-positive, non-sporeforming bacilli.

Secondary bacterial infections complicating skin lesions

“…The gram-negative anaerobic bacilli, Prevotella and Fusobacterium spp., previously susceptible to penicillins, have been shown in the past decade to have increased rates of resistance to these and other antimicrobial agents [22]. The production of â-lactamase is one of the main mechanisms of resistance to penicillins by many gram-negative anaerobic bacilli, including the Bacteroides spp.…”

Bacteriologic features and antimicrobial susceptibility in isolates from orofacial odontogenic infections

“…3,32 In cases in which infection is mild or moderate, minocycline may be effective, especially for patients allergic to penicillin or in cases of penicillin therapy failure. However, when minocycline is prescribed, an attention should be paid to its adverse effects, e.g., gastrointestinal upset, photosensitivity, tooth discoloration.…”

Penetration of clindamycin, cefoxitin, and metronidazole into pelvic peritoneal fluid of women undergoing diagnostic laparoscopy

“…Over 90% of Bacteroidesfragilis isolates are inhibited by clindamycin and metronidazole concentrations of 4 and 8 ,ug/ml, respectively (4). Thus, levels attained in peritoneal fluid in our series may be considered marginally effective for this species.…”

“…Thus, levels attained in peritoneal fluid in our series may be considered marginally effective for this species. Other pathogens, such as C. perfringens, are somewhat more susceptible in vitro and may be inhibited by documented concentrations of either antibiotic in fluid (4).…”