Antimicrobial susceptibilities of 1,292 isolates of the Bacteroides fragilis group in the United States: comparison of 1981 with 1982

Abstract

A susceptibility survey of 537 strains of the Bacteroidesfragilis group from eight centers in the United States was continued at the Tufts New England Medical Center in 1982. The results were compared with those of 755 organisms analyzed in 1981. Nine antimicrobial agents were tested by an agar dilution method. The respective percentages of resistance for 1981 and 1982 were as follows (%): cefoxitin, 8 and 10; moxalactam, 22 and 12; cefotaxime, 54 and 48; cefoperazone, 57 and 54; piperacillin, 12 and 7; clindamycin, 6 and 3; metronidazole, 0 and 0; chloramphenicol, 0 and 0; and tetracycline, 63 and 59. Regional differences in resistance rates were found. Declines in resistance to moxalactam, piperacillin, and clindamycin were noted at the participating hospitals. An outbreak of cefoxitin resistance was noted at the Tufts New England Medical Center, where the rate increased from 14 to 30%. The various species of the B. fragilis group had differing patterns of resistance; B. fragilis was the most susceptible species. Significant cross resistance among the beta-lactam agents was found. These data indicate the need to determine the susceptibility patterns of the B. fragilis group organisms within each hospital.

Susceptibilities of species of the Bacteroides fragilis group to 10 antimicrobial agents

“…Cefmetazole was less active; the MIC for 90% of the strains was 64 p,g/ml. As reported previously (3,8,16, 26) (Table 2).…”

“…Cefmetazole was less active; the MIC for 90% of the strains was 64 p,g/ml. As reported previously (3,8,16, 26) (Table 2).The results of this study indicate that several of the new beta-lactam agents are effective in vitro against the B. fragilis group. As expected, chloramphenicol and metronidazole were uniformly effective against all 94 isolates.…”

“…The incidence of clindamycin resistance in the B. fragilis group has been reported by several investigators (1,8,20,22), although there is considerable variation in the resistance rates observed in different surveys, ranging from very low (0.6%, Bourgault et al [2]) to moderate (7%, Tally et al [24], and 10%, Derriennic et al [10]) to high resistance rates similar to ours (about 20% clindamycin resistance [1,9,19,21]). …”

“…The rate of resistance to clindamycin was 21%. The results of this study demonstrate a difference in resistance rates from one species of the B. fragilis group to another.During the last few years, anaerobic bacteria have shown an increase in resistance to most of the traditionally used antimicrobial agents and some of the newer beta-lactam agents (8,12,14,24 Tables 1 and 2. ,B-Lactamase production was detected in 95% of strains.…”

In Vitro Susceptibilities of the Bacteroides fragilis Group Species: Change in Isolation Rates Significantly Affects Overall Susceptibility Data

“…The Anaerobe Working Group for the National Committee for Clinical Laboratory Standards (NCCLS) recommends that susceptibility testing of the B. fragilis group be done with a distribution of test isolates to approximate the species distribution normally isolated from infections (7). Several multicenter susceptibility studies have shown that the B. fragilis species comprises 58 to 63% of isolates (1,5,6,17). Such distribution rates have been relatively evident in studies reported during the 1980s and early 1990s.…”