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Biomedical subjects

A L Barry

Publications and source records attributed to A L Barry.

At least 73 records · Page 4Linked to original sources
PubMed1996

Survey of antimicrobial activity of four commonly used third generation cephalosporins tested against recent bacterial isolates from ten American medical centers, and assessment of disk diffusion test performance. AST Surveillance Group.

Over 2,000 clinical isolates from ten American medical centers were tested for susceptibility to cefotaxine, ceftriaxone, ceftizoxime, and ceftazidime by both broth microdilution and disk diffusion methods. Typically resistant (e.g. enterococci) and highly susceptible (e.g. streptococci) isolates showed no change in susceptibility patterns compared to previous surveys. Pseudomonas aeruginosa and Stenotrophomonas maltophilia exhibited significant decreases in susceptibility to these cephalosporins. Among Escherichia coli and Klebsiella spp isolates, two to three percent were resistant to one of the four drugs whereas they were very susceptible to the other three. Of the four antibiotics, the cefotaxime disk diffusion test results correlated best with the microdilution results. With the other three drugs the disk diffusion test yielded 1 to 9% more susceptible test results and 1 to 20% fewer resistant test results than broth microdilution when testing gram negative bacilli. The clinical significance of such discrepancies is not known, but the impact on antibiotic susceptibility surveys and antibiogram comparisons could be significant.

Ceftazidime↗
PubMed1996

Tentative interpretive criteria for testing the susceptibility of Streptococcus pneumoniae to eight fluoroquinolones.

Broth microdilution and disk diffusion methods were used to test ciprofloxacin, clinafloxacin, fleroxacin, grepafloxacin, ofloxacin, PD131628, sparfloxacin, and trovafloxacin against Streptococcus pneumoniae isolates. With each fluroquinolone tested, there was a striking unimodal population. With the exception of fleroxacin, over 96% of pneumococci tested were inhibited by each drug's modal MIC +/-1 twofold concentration. Over 92% of pneumococci produced inhibitory zone diameters equal to the mode +/-4 mm for each drug. For most fluoroquinolones, the interpretive criteria approved or proposed for nonfastidious organisms appear to be appropriate for pneumococci. For clinafloxacin and trovafloxacin, however, the proposed MIC breakpoints for nonfastidious organisms are four-to eightfold greater than the highest MIC encountered with pneumococci. For future surveillance efforts, low concentrations must be evaluated to detect any subtle shift in pneumococcal populations that might be undetected by testing only breakpoint concentrations.

Anti-Infective Agents↗
PubMed1996

Tentative interpretive criteria and quality control parameters for in-vitro susceptibility testing of Neisseria gonorrhoeae to two fluoroquinolones (PD 131628 and grepafloxacin (OPC 17116)).

The susceptibility of Neisseria gonorrhoeae to PD 131628 and grepafloxacin (OPC 17116) was evaluated by agar dilution and disc diffusion methods. A tentative susceptibility category for both fluoroquinolones included strains for which the MICs are < or = 0.06 mg/L and the zones of inhibition are > or = 38 mm for PD 131628 and > or = 37 mm for grepafloxacin. Quality control studies with N. gonorrhoeae ATCC 49226 suggested that agar dilution MIC limits were 0.002-0.008 mg/L and 0.004-0.03 mg/L for PD 131628 and grepafloxacin, respectively. The zone size limits were 50-58 mm for PD 131628 and 44-52 mm for grepafloxacin.

Anti-Infective Agents↗
PubMed1996

In-vitro susceptibility of Streptococcus pneumoniae to the d- and l-isomers of ofloxacin: interpretive criteria and quality control limits.

The l-isomer of ofloxacin (levofloxacin) was twice as active as ofloxacin and the d-isomer was inactive against 654 Streptococcus pneumoniae isolates. For disc susceptibility tests of pneumococci, 5 micrograms levofloxacin discs can be used with interpretive criteria of < or = 12 mm for resistant (MIC > or = 8.0 mg/L) and > or = 16 mm for susceptible (MIC < or = 2.0 mg/L). For quality control of levofloxacin tests, S. pneumoniae ATCC 49619 should give zones 20-25 mm in diameter and MICs 0.5-2.0 mg/L.

Anti-Infective Agents↗
PubMed1996

In vitro activities of five fluoroquinolone compounds against strains of Streptococcus pneumoniae with resistance to other antimicrobial agents.

Ciprofloxacin, clinafloxacin, PD 131628, sparfloxacin, and trovafloxacin were tested against 236 strains of Streptococcus pneumoniae, most of which were resistant to other agents. Resistance to multiple antibiotics did not affect the organism's susceptibility to the fluoroquinolones. The fluoroquinolones with in vitro antipneumococcal activity might be particularly useful against strains that are resistant to the more traditional therapeutic agents.

Anti-Infective Agents↗
PubMed1996

Prevalence of resistance to three fluoroquinolones: assessment of levofloxacin disk test error rates and surrogate predictors of levofloxacin susceptibility. AST Surveillance Group.

More than 3,000 consecutive clinical bacterial isolates from 10 U.S. medical centers were subjected to standard broth microdilution and disk diffusion tests to determine their susceptibilities to levofloxacin, ofloxacin, D-ofloxacin, and ciprofloxacin. Levofloxacin was confirmed to be twice as active as ofloxacin and to have activity comparable to that of ciprofloxacin, with minor variations in activity against some species. The prevalence of resistant isolates was 7.1% to levofloxacin, 9.3% to ciprofloxacin, and 11.2% to ofloxacin. The susceptibilities of some species to the quinolones were less than those reported in previous studies. Pseudomonas aeruginosa isolates had the greatest variability in their susceptibilities to the three drugs between the participating centers. Two proposed zone size breakpoints for levofloxacin disk tests yielded similar low error rates. Ofloxacin and ciprofloxacin susceptibility test results correlated reasonably well with those of levofloxacin and could be used as surrogate indicators of levofloxacin susceptibility, but that resulted in some serious errors, and thus, direct testing of levofloxacin susceptibility is preferable. Replicate testing of standard quality control strains confirmed the established and proposed quality control parameters for all three quinolones tested.

Anti-Infective Agents↗
PubMed1996

Surrogate disks for predicting cefotaxime and ceftriaxone susceptibilities of Streptococcus pneumoniae.

Cefotaxime- and ceftriaxone-resistant Streptococcus pneumoniae is now appearing in some medical centers, but 30-micrograms cefotaxime or 30-micrograms ceftriaxone disks are not reliable for detecting such strains. Studies were undertaken to select another cephalosporin disk that might be used as a screening test that could be used in conjunction with a 1-micrograms oxacillin disk. A 30-micrograms cefuroxime disk is proposed: strains with zones > or = 28 mm in diameter are predictably susceptible to cefotaxime and ceftriaxone, and those with smaller zones should be further studied to confirm resistance to either drug. A 30-micrograms ceftizoxime disk may also be used as a screening test with zones > or = 26 mm indicating susceptibility, but cefuroxime disks are preferred.

Cefotaxime↗
PubMed1996

Detection of extended-spectrum-beta-lactamase-producing members of the family Enterobacteriaceae with Vitek ESBL test.

A three-phase analysis of the Vitek ESBL test and a double-disk (2 disk) test was performed to assess their ability to detect extended-spectrum beta-lactamases (ESBLs) in members of the family Enterobacteriaceae. In the first two phases involving detection of ESBLs in 157 stains processing well-characterized beta-lactamases, sensitivity and specificity were found to be 99.5 and 100%, respectively, for the Vitek ESBl test and 98.1 and 99.4%, respectively, for the 2-disk test. In the third phase, in which the ability of each test to detect ESBLs in 295 clinical isolates was assessed, there was only one false positive (Vitek ESBL test). Across all three phases, the Vitek ESBL test was found to be much easier to perform than the 2-disk test. The latter also involved subjective interpretation of results. There were a total of 176 Escherichia coli and 157 Klebsiella pneumoniae isolates and less than 40 isolates of each of 14 other species evaluated. In a supplemental study of Klebsiella oxytoca, an organism possessing a chromosomal beta-lactamase similar to an ESBL, the Vitek ESBL test was found to be capable of detecting hyperproduction of this enzyme in strains of this species as well. These data indicate that the Vitek ESBL test is reliable for the detection of ESBLs in E. coli and K. pneumoniae, the two species in which ESBLs are most common, and of hyperproduction of the K. oxytoca beta-lactamase, a situation which engenders a level of resistance to this species similar to that seen with ESBLs.

Cephalosporins↗
PubMed1996

Fluconazole disk diffusion procedure for determining susceptibility of Candida species.

A simple disk diffusion test was defined for quick determination of the susceptibility of Candida species to fluconazole. The standard macrotube dilution reference method, the fluconazole E test, and a 25-microgram fluconazole disk test were all performed with each of 250 Candida species selected to provide a broad range of fluconazole MICs. All three methods were in excellent agreement. On RPMI 1640-glucose agar, isolates with inhibition zone diameters of > or = 19 mm were all susceptible (MIC, < or = 8.0 micrograms/ml) by the E test and 94% were susceptible by the macrotube method. Strains with smaller zones were either resistant, intermediate (dose-dependent susceptibility), or susceptible by the reference methods. The disk test did not adequately separate fully resistant strains from those with dose-dependent susceptibility: additional quantitative tests are needed for the few strains that are not unequivocally susceptible by the disk method.

Antifungal Agents↗
PubMed1995

In vitro susceptibilities of clinical yeast isolates to three antifungal agents determined by the microdilution method.

A comparative evaluation of the in vitro susceptibilities of 597 clinical yeast isolates to amphotericin B, fluconazole, and 5-fluorocytosine (5FC) was conducted. The broth macrodilution reference method of the National Committee for Clinical Laboratory Standards (NCCLS, M27-P) was adapted to the microdilution method. Microdilution endpoints for amphotericin B were scored as the lowest concentration in which a score of 0 (complete absence of growth) was observed and for 5FC and fluconazole as the lowest concentration in which a score of 2 (prominent decrease in turbidity; MIC-2) was observed compared to the growth control. The MIC values were read after 24 and 48 h incubation. A broad range of MIC values was observed with each antifungal agent. Amphotericin B was very active (MIC90 < or = 1.0 microgram/ml) against all of the yeast isolates with the exception of C. lusitaniae (MIC90 > or = 2.0 micrograms/ml). Fluconazole was most active against C. parapsilosis (MIC90 of 1.0 microgram/ml) and least active against C. krusei (MIC90 of 32 micrograms/ml). 5FC was most active against C. albicans, C. parapsilosis, C. tropicalis, and T. glabrata (MIC90 < or = 1.0 microgram/ml) and was least active against C. krusei and C. lusitaniae (MIC90 > or = 16 micrograms/ml). These data indicate that the microdilution method, performed in accordance with M27-P, provides a means of testing larger numbers of yeast isolates against an array of antifungal agents and allows this to be accomplished in a reproducible and standardized manner. Given these results, it appears that the microdilution method may be a useful alternative to the macrodilution reference method for susceptibility testing of yeasts.

Amphotericin B↗
PubMed1995

Criteria for testing the susceptibility of Streptococcus pneumoniae to cefotaxime and its desacetyl metabolite using 1 microgram or 30 micrograms cefotaxime disks.

In vitro susceptibility tests were performed with 350 selected strains of Streptococcus pneumoniae to evaluate disk diffusion tests with 30 micrograms and 1 microgram cefotaxime disks. Zones were compared to MICs of cefotaxime with and without its desacetyl metabolite. Cefotaxime was two to eight times more active than desacetyl cefotaxime, but the two compounds were additive when combined in vitro. For 30 micrograms disks, zone size breakpoints were < or = 27 mm, 28-30 mm and > or = 31 mm for resistant, intermediate and susceptible, respectively. For 1 microgram disks, those zone size criteria were reduced to < or = 13 mm, 14-16 mm and > or = 17 mm. The 30 micrograms disk that is currently available for testing other species can be used for testing pneumococci; however, the 1 microgram disk has some important advantages.

Cefotaxime↗