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Biomedical subjects

A L Barry

Publications and source records attributed to A L Barry.

At least 145 records · Page 8Linked to original sources
PubMed1992

Proposed interpretive criteria and quality control parameters for testing susceptibility of Neisseria gonorrhoeae to beta-lactam-clavulanate combinations.

To support future clinical studies, in vitro susceptibility tests were examined to determine whether Neisseria gonorrhoeae could be tested reliably against two beta-lactam-clavulanate combinations. All isolates that were tested appeared to be susceptible to amoxicillin and ticarcillin in combination with clavulanic acid. In the absence of resistant isolates, only a breakpoint for a susceptible category could be defined for agar dilution tests with amoxicillin-clavulanic acid (MIC of less than or equal to 2.0/1.0 micrograms/ml is tentatively proposed). For disk diffusion tests, a corresponding breakpoint zone diameter of greater than or equal to 28 mm is suggested. The validity of the breakpoints for penicillinase-negative penicillin-resistant strains awaits clinical data. Proposed quality control limits for testing amoxicillin-clavulanic acid by agar dilution and disk diffusion methods are a MIC of 0.25/0.125 to 1.0/0.5 micrograms/ml and zones of 30 to 40 mm in diameter for N. gonorrhoeae ATCC 49226, a MIC of 0.125/0.06 to 0.5/0.25 micrograms/ml for Staphylococcus aureus ATCC 29213, and zones of 30 to 38 mm for S. aureus ATCC 25923. Ticarcillin-clavulanate is currently tested against other species by preparing doubling dilutions of ticarcillin with a constant 2 micrograms of clavulanate per ml. By that method, all gonococci were susceptible to low concentrations. However, the amount of clavulanic acid that is included (2 micrograms/ml) will, by itself, inhibit many strains of N. gonorrhoeae. Consequently, the role of ticarcillin in the combination cannot be determined, and such tests are not recommended.

Amoxicillin↗
PubMed1991

Antistaphylococcal activity of the fluoroquinolones CI-960, PD 131628, sparfloxacin, ofloxacin and ciprofloxacin.

Five fluoroquinolones were tested against 300 staphylococci from a wide variety of US medical centers including 150 strains resistant to penicillinase-resistant penicillins (PRP-resistant). Ten ciprofloxacin-resistant strains of PRP-resistant Staphylococcus aureus were relatively resistant to the other fluoroquinolones, but the remaining 290 isolates were susceptible to all five drugs at established or anticipated breakpoint concentrations. The relative potency of the study drugs could be ranked as follows: CI-960 greater than PD 131628 greater than sparfloxacin greater than ciprofloxacin greater than ofloxacin. All five drugs were bactericidal against PRP-resistant and PRP-susceptible staphylococci.

Anti-Infective Agents↗
PubMed1991

Influence of the test medium on azithromycin and erythromycin regression statistics.

Azithromycin and erythromycin disk test results were compared to MIC values obtained in six different media. One hundred isolates were tested in triplicate, and geometric mean MICs were plotted against arithmetic mean zone diameters and regression statistics calculated. The test media evaluated did not markedly influence MIC values, but incubation in 5-7% CO2 resulted in a two- to four-fold decrease in the activity of both drugs. For testing Haemophilus influenzae and other species that need to be tested in 5-7% CO2, interpretive breakpoints for the macrolides and azalides should be modified to compensate for the anticipated decrease in activity.

Azithromycin↗
PubMed1991

Cross-resistance and cross-susceptibility between fluoroquinolone agents.

The results of broth microdilution susceptibility tests with 750 bacterial isolates were used to directly compare six different fluoroquinolone antibiotics (ciprofloxacin, enoxacin, fleroxacin, lomefloxacin, ofloxacin and temafloxacin). Against enteric bacilli, enoxacin and lomefloxacin were similar in their spectra of activity but they differed from the other drugs tested. Against the non-enteric gram-negative bacilli, ciprofloxacin differed from enoxacin and lomefloxacin: fleroxacin, ofloxacin and temafloxacin were nearly identical in their activity. For routine susceptibility tests, ofloxacin and fleroxacin were similar in activity and either drug could be used as a class representative for predicting susceptibility to the other fluoroquinolone agents. Occasionally, strains that are resistant to the class representative may be susceptible to other members of the fluoroquinolone class, but those that are susceptible to the class representative are rarely resistant to the other compounds.

Anti-Infective Agents↗
PubMed1991

Reproducibility of disc susceptibility tests with Haemophilus influenzae.

Triplicate susceptibility tests were performed in each of three laboratories with 45 strains of Haemophilus influenzae and a single lot of Haemophilus test medium (HTM) agar plates. Using clarithromycin, erythromycin and chloramphenicol discs. zone sizes varied over ranges averaging only 4.3-5.8 mm. Ampicillin zone sizes were more variable, especially when beta-lactamase-producing strains were being tested, but the latter strains were consistently categorized as being resistant. A 94% interpretive consistency was observed with the two macrolides.

Ampicillin↗
PubMed1991

Anti-staphylococcal activity of temafloxacin, ciprofloxacin, ofloxacin and enoxacin.

Four fluoroquinolones were tested for antimicrobial activity against 300 isolates of staphylococci collected from medical centres throughout the United States. No cross-resistance to methicillin or oxacillin and the fluoroquinolones was observed. All four drugs were bactericidal agents and all ciprofloxacin-susceptible strains were inhibited at recommended breakpoint concentrations. Ciprofloxacin-resistant strains showed complete cross-resistance to the other fluoroquinolones. The relative potency of the study drugs as judged by MIC/MBC determinations was: temafloxacin greater than ciprofloxacin greater than ofloxacin greater than enoxacin.

Anti-Infective Agents↗
PubMed1991

In vitro inactivation of aminoglycosides by sulbactam, other beta-lactams, and sulbactam-beta-lactam combinations.

At clinically achievable levels (e.g., 25 micrograms/ml), sulbactam exerted no effect on aminoglycoside concentrations when incubated together in pooled serum at 37 degrees C for up to 24 h. Sulbactam alone and in combination with ampicillin or cefoperazone inactivated tobramycin, gentamicin, netilmicin, and amikacin in vitro when the sulbactam concentration was 200 to 225 micrograms/ml. At 75 micrograms/ml, sulbactam inactivated only tobramycin. Inactivation of tobramycin by high concentrations of sulbactam occurred even at -20 degrees C, but not at -70 degrees C, and was influenced by the serum matrix.

Amikacin↗
PubMed1991

Multicenter evaluation of the in vitro activities of three new quinolones, sparfloxacin, CI-960, and PD 131,628, compared with the activity of ciprofloxacin against 5,252 clinical bacterial isolates.

The in vitro activities of three new quinolones (sparfloxacin, CI-960, and PD 131,628) were compared with that of ciprofloxacin against 5,252 routine clinical aerobic and facultatively anaerobic bacterial isolates. Overall, CI-960 was the most active drug in vitro (MIC for 90% of the strains tested, 0.13 micrograms/ml); ciprofloxacin and sparfloxacin were the least active (MIC for 90% of the strains tested, 1.0 micrograms/ml). All three new quinolones, but particularly CI-960 and PD 131,628, exhibited significantly greater activity than ciprofloxacin against enterococci and staphylococci.

Anti-Infective Agents↗
PubMed1991

In vitro activities of sparfloxacin, tosufloxacin, ciprofloxacin, and fleroxacin.

The in vitro activity of sparfloxacin was compared with those of tosufloxacin, ciprofloxacin, and fleroxacin against 730 bacterial isolates representing 49 different species. Sparfloxacin and ciprofloxacin had similar spectra of activity, but sparfloxacin was less active against Pseudomonas aeruginosa and more active against many gram-positive cocci and anaerobic bacteria. Tosufloxacin MICs were generally 8- to 16-fold lower than those for sparfloxacin or ciprofloxacin. All four fluoroquinolones were active against nalidixic acid-susceptible strains of the family Enterobacteriaceae (MIC for 90% of the isolates [MIC90], less than or equal to 0.25 micrograms/ml) but nalidixic acid-resistant strains were less susceptible (MIC90, greater than or equal to 4.0 micrograms/ml). Against Pseudomonas aeruginosa isolates, MIC90s were 1.0 micrograms/ml for tosufloxacin, 2.0 micrograms/ml for ciprofloxacin, and 4.0 micrograms/ml for sparfloxacin. Against Enterococcus faecalis, sparfloxacin and ciprofloxacin MIC90s were 1.0 and 2.0 micrograms/ml, respectively. MIC90s for ciprofloxacin-susceptible Staphylococcus aureus were 0.016 micrograms/ml for tosufloxacin, 0.06 micrograms/ml for sparfloxacin, and 0.5 micrograms/ml for both ciprofloxacin and fleroxacin. With four species of gram-negative bacilli, mutants resistant to two to four times the sparfloxacin MIC occurred spontaneously at frequencies of 10(-7) to 10(-9): single-step high-level resistance was not observed. In vitro-selected sparfloxacin-resistant mutants displayed cross-resistance to other quinolones, as did clinical isolates of ciprofloxacin-resistant S. aureus. Tosufloxacin MICs with broth microdilution methods were four- to eightfold greater than those obtained with agar dilution methods. The two procedures gave comparable results when sparfloxacin or ciprofloxacin was being tested.

Anti-Infective Agents↗
PubMed1991

In vitro susceptibility testing procedures for fosfomycin tromethamine.

Fosfomycin tromethamine (previously fosfomycin trometamol) is an orally administered fosfomycin which may be used for single-dose therapy of uncomplicated urinary tract infections. Fosfomycin tromethamine, norfloxacin, and trimethoprim-sulfamethoxazole inhibited greater than 90% of 352 bacterial isolates representing 25 different species; trimethoprim and nalidixic acid had narrower spectrums of activity. Strains of Escherichia, Citrobacter, Enterobacter, and Klebsiella species were much more susceptible when glucose-6-phosphate was added to the test medium, but isolates belonging to other genera were not affected.

Bacteria↗
PubMed1991

Proposed interpretive criteria and quality control parameters for testing in vitro susceptibility of Neisseria gonorrhoeae to ciprofloxacin.

Ciprofloxacin was subjected to a multilaboratory study designed to determine its in vitro susceptibility criteria for Neisseria gonorrhoeae and its quality control parameters for both agar dilution and disk diffusion susceptibility testing for this species. All clinical isolates were susceptible, i.e., MICs were less than or equal to 0.06 microgram/ml and zones of inhibition were greater than or equal to 36 mm. A resistant category could not be defined, but in vitro-selected mutants gave zones of less than or equal to 35 mm, and MICs for these strains were greater than or equal to 0.12 microgram/ml. For quality control of ciprofloxacin agar dilution tests on supplemented GC agar, MICs for Staphylococcus aureus ATCC 29213 ranged from 0.12 to 0.5 microgram/ml. For quality control of 5-micrograms ciprofloxacin disk tests, N. gonorrhoeae ATCC 49226 and S. aureus ATCC 25923 produced acceptable zone diameter ranges of 48 to 58 mm and 22 to 26 mm, respectively.

Ciprofloxacin↗