PubMed Health⌕ Search

Biomedical subjects

A Henderberg

Publications and source records attributed to A Henderberg.

8 recordsLinked to original sources
PubMed1994

A five-year multicenter study of the susceptibility of the Bacteroides fragilis group isolates to cephalosporins, cephamins, penicillins, clindamycin, and metronidazole in the United States.

Over 2800 clinical strains of the Bacteroides fragilis group were collected during a 5-year period from ten geographically separate sites and tested for their susceptibility to various antimicrobial agents using a broth microdilution method. Among the cephalosporins, ceftizoxime was the most active (13% resistance) and importantly exhibited relatively equal activity against both B. fragilis species and non-B. fragilis species. Cefotaxime exhibited similar activity with an overall resistance rate of 18%. Both ceftriaxone and cefoperazone were appreciably less active cephalosporins especially against non-B. fragilis species. With regard to cephamycins, cefoxitin (MIC90, 32 micrograms/ml) was more active than cefotetan (MIC90, > or = 256 micrograms/ml) and cefmetazole (MIC90, 64 micrograms/ml). Non-B. fragilis species were highly resistant to cefotetan and cefmetazole. Imipenem was highly active against all strains with the exception of four strains of B. fragilis. Ampicillin-sulbactam, amoxicillin-clavulanate, piperacillin-tazobactam, and cefoperazone-sulbactam were all highly active with resistance rates < 2%. No resistance was detected to metronidazole, whereas 14% of isolates were resistant to clindamycin. When compared with other studies, these findings underscore the wide variability in susceptibility patterns reported nationwide and the need to continue monitoring these patterns to aid in choosing the most active compounds for therapy.

Anti-Bacterial Agents↗
PubMed1990

In-vitro study of the susceptibility of cefoxitin/cefotetan resistant Bacteroides fragilis group strains to various other antimicrobial agents.

The in-vitro activity of various beta-lactam antibiotics, beta-lactam/beta-lactamase inhibitor combinations, clindamycin, and metronidazole was determined against Bacteroides fragilis group isolates that were resistant to both cefoxitin and cefotetan. Among the cephalosporins tested ceftizoxime was the most active with 80% of the strains susceptible, followed by cefotaxime (65% susceptible), and cefoperazone (47% susceptible). Piperacillin and clindamycin showed comparable activity to ceftizoxime with 80% and 81% susceptible, respectively. The addition of a beta-lactamase inhibitor (sulbactam, clavulanate, or tazobactam) enhanced the activity of the various beta-lactam agents from 4-fold to 16-fold overall. One strain of B. fragilis was found that was resistant to all beta-lactam agents either alone or in combination. All strains in this study were susceptible to less than or equal to 4 mg/l of metronidazole.

Aminoglycosides↗
PubMed1990

Discordant results between the broth disk elution and broth microdilution susceptibility tests with Bacteroides fragilis group isolates.

Susceptibility testing of 161 clinical isolates of the Bacteroides fragilis group was performed to compare interpretive results generated by the broth disk elution and broth microdilution methods recommended by the National Committee for Clinical Laboratory Standards. Among the cephalosporin-cephamycin compounds tested, correlation was poorest for ceftizoxime (71%), ceftriaxone (57%), and cefotaxime (47%); when the tests did not correlate, false resistance was seen 92, 95, and 93% of the time, respectively. Cefotetan and cefoperazone showed lack of correlation in 19 and 20% of the tests, respectively. For cefotetan, false resistance was more frequent, while with cefoperazone, false susceptibility occurred more often. Cefoxitin produced the fewest discrepancies; 10% of the disk elution tests produced either false-resistance or false-susceptibility results. Mezlocillin and piperacillin showed lack of correlation in 8 and 14% of the tests, respectively, and discrepancies were due primarily to false-resistance results. Overall with the beta-lactams, 84% of the discordant interpretive results were false resistance by the broth disk elution test. Clindamycin had a discrepancy rate of 10%, with the majority of discrepancies being false susceptibility disk elution results. Because of the high number of discrepancies noted with ceftizoxime, ceftriaxone, and cefotaxime, we recommend that these drugs not be tested by the disk elution method and that they be tested by a quantitative MIC method such as the broth microdilution test. Furthermore, caution should be exercised when interpreting broth disk elution results with all the beta-lactams included in this study except imipenem. These data indicate the lack of correlation of results between these two tests for many beta-lactams and suggest the need for a reexamination of the disk elution method to provide a more accurately standardized test.

Bacteroides fragilis↗
PubMed1988

Biosynthetic origin of aflatoxin G1: confirmation of sterigmatocystin and lack of confirmation of aflatoxin B1 as precursors.

The origin of aflatoxin G1 was studied using mutant strains of Aspergillus parasiticus blocked early in the pathway and by tracing 14C-labelled aflatoxin B1 (AFB1) in wild-type A. flavus and A. parasiticus strains. Sterigmatocystin (ST) was a precursor of AFB1, AFG1 and AFG2 in the four mutants examined. The identity of AFG1 was confirmed by mass spectrometry. No evidence for conversion of AFB1 to AFG1 was found. A rigorously controlled study of conversions of radioactivity based on preparative thin-layer chromatography of aflatoxins demonstrated that low levels of aflatoxin interconversions previously reported in the literature might actually be artifacts.

Aflatoxin B1↗
PubMedDate not supplied

Lomefloxacin, a new fluoroquinolone. Studies on in vitro antimicrobial spectrum, potency, and development of resistance.

Lomefloxacin (NY-198; SC-47111), a potent new difluoroquinolone, was studied to compare its in vitro activity with that of other antimicrobials against 2194 clinical isolates. Lomefloxacin showed excellent inhibitory and bactericidal activity against strains of Enterobacteriaceae and inhibited greater than 99% of the isolates at a concentration of 4 micrograms/ml or less. Lomefloxacin exhibited good-to-moderate activity against strains of Acinetobacter (MIC90 4 micrograms/ml) and Pseudomonas aeruginosa (MIC90 8 micrograms/ml), but poor activity for Pseudomonas cepacia (MIC90 greater than 16 micrograms/ml). Staphylococcus aureus, and Staphylococcus epidermidis isolates, both oxacillin-susceptible and -resistant strains, were susceptible (MIC90 1 micrograms/ml) to lomefloxacin and the other fluoroquinolones. Strains of Haemophilus influenzae, (MIC90 less than or equal to 0.13 micrograms/ml) Neisseria gonorrhoeae (MIC90 less than or equal to 0.03 micrograms/ml), and Branhamella catarrhalis (MIC90 less than or equal to 0.03 micrograms/ml) were highly susceptible to lomefloxacin. Streptococcal isolates, especially viridans streptococci, were considerably less susceptible to the fluoroquinolones. Overall, lomefloxacin had comparable activity to norfloxacin, fleroxacin, and ofloxacin, and against many facultative anaerobes lomefloxacin was more active than imipenem, cefotaxime, ceftazidime, ticarcillin/clavulanic acid, aztreonam, trimethoprim/sulfamethoxazole and gentamicin. Development of resistance to lomefloxacin by spontaneous mutation was low and comparable to that of other fluoroquinolones. Growth in subinhibitory concentrations resulted in increased resistance to fluoroquinolones for selected test strains.

4-Quinolones↗
PubMedDate not supplied

Lomefloxacin (SC 47111 or NY-198), a new difluorinated quinolone: comparison of the in vitro activity with other broad spectrum antimicrobials against Enterobacteriaceae, Acinetobacter spp, Aeromonas spp, and Pseudomonas aeruginosa.

Using a broth microdilution method, we compared the in vitro activity of lomefloxacin to other broad spectrum antimicrobials against clinical strains of Enterobacteriaceae, Acinetobacter spp, Aeromonas spp, and P. aeruginosa. Against the Enterobacteriaceae and A. hydrophila, lomefloxacin showed excellent activity with MIC50 values ranging from 0.12-0.5 micrograms/ml and MIC90 values ranging from 0.12-1.0 micrograms/ml. By comparison, lomefloxacin had superior activity to nalidixic acid and difloxacin, comparable activity to norfloxacin and fleroxacin, and slightly less activity than ciprofloxacin. Lomefloxacin was also more active than imipenem, ceftazidime, aztreonam, ticarcillin/clavulanic acid (T-CA), and gentamicin. Lomefloxacin was less active (MIC90, 4 micrograms/ml) against Acinetobacter strains than Enterobacteriaceae strains. Against these same Acinetobacter strains, lomefloxacin was 8- to 64-fold more active than ceftazidime, aztreonam, T-CA, and gentamicin but slightly less active than imipenem. Lomefloxacin was 2- to 8-fold more active than fleroxacin, difloxacin, and nalidixic acid against strains of P. aeruginosa. However, lomefloxacin was less active than ciprofloxacin and norfloxacin. Lomefloxacin had comparable activity to imipenem but was 2- to 16-fold more active than ceftazidime, aztreonam, T-CA, and gentamicin. Thus, lomefloxacin demonstrated comparable activity to other fluorinated quinolones in that it possesses high active against clinical strains of Enterobacteriaceae and had good-to-moderate activity against most strains of Acinetobacter and P. aeruginosa.

4-Quinolones↗