Susceptibility of
            <i>Bacteroides fragilis</i>
            to Six Antibiotics Determined by Standardized Antimicrobial Disc Susceptibility Testing

Sutter, Vera L.; Kwok, Yung-Yuan; Finegold, Sydney M.

doi:10.1128/aac.3.2.188

Cited by 66 publications

(25 citation statements)

References 13 publications

(8 reference statements)

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“…These two methods of inoculum preparation apparently yield comparable results in agar dilution testing (15). However, using the SGE method, we have found that preparing the inoculum from a broth culture in logarithmic phase yields consistently lower MICs than preparing an inoculum by suspending colonies (presumably in stationary phase) to the proper density (116 (104). Recently, modifications of the technique were evaluated, and good correlation with the reference method was seen for certain antimicrobial agents (8,10,58).…”

Section: P-lactamase Testsmentioning

confidence: 99%

Susceptibility testing of anaerobic bacteria: myth, magic, or method?

Wexler

1991

Clin Microbiol Rev

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The demand for susceptibility testing of anaerobes has increased, yet consensus as to procedure and interpretation in this area has not been achieved. While routine testing of anaerobic isolates is not needed, certain isolates in specific clinical settings should be tested. Also, laboratories may monitor their local antibiograms by doing periodic surveillance batch testing. The National Committee for Clinical Laboratory Standards has published a protocol of methods approved for susceptibility testing of anaerobic bacteria. Both agar and broth microdilution are included; however, the broth disk elution method is no longer approved by the National Committee for Clinical Laboratory Standards because of method-related interpretive errors. A number of newer methods are undergoing evaluation and seem promising. Clinicians and microbiologists reviewing susceptibility reports should be aware of sources of variability in the test results. Variables in susceptibility testing of anaerobes include the media and methods used, organisms chosen for testing, breakpoints chosen for interpretation, antibiotic, and determination of endpoint. Clustering of MICs around the breakpoint may lead to significant variability in test results. Adherence of testing laboratories to approved methods and careful descriptions of the method and the breakpoints used for interpretation would facilitate interlaboratory comparisons and allow problems of emerging resistance to be noted. A variety of resistance mechanisms occurs in anaerobic bacteria, including the production of beta-lactamase and other drug-inactivating enzymes, alteration of target proteins, and inability of the drug to penetrate the bacterial wall. Antimicrobial resistance patterns in the United States and abroad are described.

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Section: P-lactamase Testsmentioning

confidence: 99%

Susceptibility testing of anaerobic bacteria: myth, magic, or method?

Wexler

1991

Clin Microbiol Rev

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“…A: number of workers have demonstrated the in vitro susceptibility of anaerobes to carbenicillin (3,5,16,25,34,41 (24). We believe that the use of the regression line to develop interpretive schemes in certain studies (17,29,34,35,36,41) can be questioned for the reasons cited.…”

Section: Discussionmentioning

confidence: 99%

Susceptibility Testing of Anaerobic Bacteria with 100-μg Carbenicillin Disks

Laslie

Lambe

1976

Antimicrob Agents Chemother

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“…Their greatest discrepancies were with erythromycin also, although the disagreements we found with this antibiotic were not confined to Peptococcus magnus as were theirs. This problem with erythromycin has been experienced by others (6,8). Attempts have been made to explain this on the basis of the reduced activity of erythromycin in the presence of CO2.…”

Section: C02-mentioning

confidence: 93%

Evaluation of the Modified Broth-Disk Method for Determining Antibiotic Susceptibilities of Anaerobic Bacteria

Blazevic

1975

Antimicrob Agents Chemother

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A total of 110 strains of anaerobic bacteria including 9 different genera was tested for antibiotic susceptibility by the modified broth-disk method of Wilkins and Thiel (1973), using prereduced media and the VPI anaerobic culture system. Results were compared with those obtained with an agar dilution technique with incubation in a GasPak jar. There was greater than 95% agreement between the two methods with ampicillin, cephalothin, chloramphenicol, and clindamycin, and 90% or greater agreement with erythromycin, penicillin, and tetracycline.Routine susceptibility testing of anaerobes has been a problem for clinical laboratories because of the lack of a standardized disk diffusion method that is adequate for use with the anaerobic bacteria which show such wide variations in generation time. In 1973, Wilkins and Thiel (9) published a simple method for determining the susceptibility of anaerobic bacteria to antibiotics. Their method is a modified broth dilution technique using only one concentration of antibiotic and commercially available disks as the source of antibiotic. The purpose of the present study was to compare the broth-disk method with the more accepted agar dilution technique in order to evaluate its accuracy. MATERIALS AND METHODSA total of 110 strains of anaerobic bacteria isolated in the years 1971 to 1973 from clinical specimens in the Diagnostic Microbiology Laboratory of the University of Minnesota Hospitals was used. The strains used included 46 Bacteroides fragilis, 3 Bacteroides melaninogenicus, 7 Bacteroides sp., 8 Bifidobacterium sp., 9 Clostridium perfringens, 7 Clostridium sp., 7 Eubacterium sp., 2 Fusobacterium sp., 1 Lactobacillus sp., 10 Peptococcus sp., 7 Peptostreptococcus sp., and 3 Veillonella sp. All organisms were identified by methods and characteristics defined by Holdeman and Moore (3).All prereduced media used were purchased from Scott Laboratories, Fiskeville, R. I. Culture in prereduced media was carried out by using the VPI anaerobic culture system (Bellco) and oxygen-free C02-The modified broth-disk method was performed as described by Wilkins and Thiel (9). One drop of an overnight culture in prereduced chopped meatglucose broth was used as inoculum for the tests. The antibiotic disks used were obtained from Bioquest.For the agar dilution technique, plates were prepared with brain heart infusion agar supplemented with hemin and vitamin K (Scott Laboratories; 1 ml per 100 ml of agar) and containing serial twofold dilutions of each antibiotic. The plates were held overnight at room temperature before inoculation. For the inoculum, a 1:100 dilution in prereduced brain heart infusion broth was made of the same overnight chopped meat-glucose culture used for the broth-disk method. The agar dilution plates were inoculated with the diluted cultures by using the replicator device of Steers et al. (7). Two plates without any antibiotic were also inoculated for a growth control and an aerobic check. The plates were inoculated in room air, and only 20 organisms were replicated at a...

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Susceptibility of Bacteroides fragilis to Six Antibiotics Determined by Standardized Antimicrobial Disc Susceptibility Testing

Cited by 66 publications

References 13 publications

Susceptibility testing of anaerobic bacteria: myth, magic, or method?

Susceptibility testing of anaerobic bacteria: myth, magic, or method?

Susceptibility Testing of Anaerobic Bacteria with 100-μg Carbenicillin Disks

Evaluation of the Modified Broth-Disk Method for Determining Antibiotic Susceptibilities of Anaerobic Bacteria

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