Search PubMed⌕ Search

Biomedical subjects

A L Barry

Publications and source records attributed to A L Barry.

At least 217 records · Page 12Linked to original sources
PubMed1987

Netilmicin disk susceptibility tests: effect of cations on the MIC correlates.

When testing Pseudomonas aeruginosa against netilmicin, MICs were markedly affected by the concentration of cations added to the test medium. A susceptible disk test result (zone greater than or equal to 15 mm) corresponded to MIC less than or equal to 4.0 micrograms/ml in unsupplemented broth, less than or equal to 12 micrograms/ml in broth with half the usual amount of cations and less than or equal to 32 micrograms/ml in broth with the recommended concentration of cations. Tests with 30 micrograms netilmicin disks best predicted susceptibility as determined by MICs in broth without added cations. When the MICs were determined in cation supplemented broth, the number of interpretive discrepancies increased to an unacceptably high level.

Cations↗
PubMed1987

Comparative in vitro activity of amifloxacin and five other fluoroquinolone antimicrobial agents and preliminary criteria for the disk susceptibility test.

Amifloxacin is a fluoroquinolone with a spectrum of activity similar to that of ofloxacin, pefloxacin, enoxacin, norfloxacin and ciprofloxacin. For disk susceptibility tests, 10 micrograms amifloxacin disks are recommended with zone size interpretive standards of less than or equal to 16 mm and greater than or equal to 20 mm for the resistant and susceptible categories respectively.

Anti-Bacterial Agents↗
PubMed1987

Disk diffusion and disk elution tests with A-56268 and erythromycin.

Zones of inhibition around 15 micrograms A-56268 disks were essentially the same size as those around 15 micrograms erythromycin disks. If the same MIC breakpoints are to be used for defining susceptible categories for both macrolides, interpretive zone size standards for erythromycin disk tests may also be used for A-56268 disk tests. Against anaerobic bacteria, the two macrolides were only marginally effective when broth dilution tests were incubated in anaerobic jars. The aerobically incubated thioglycolate broth disk elution test indicated that both macrolides were much more effective against anaerobes. Three 15 micrograms disks eluted in 5 ml thioglycolate provided satisfactory results.

Bacteria↗
PubMed1987

CI-934, a new difluoroquinolone: in vitro antibacterial activity and proposed disk diffusion test interpretive criteria.

The susceptibility of 7,763 clinical isolates at four medical centers to CI-934 and three comparative quinolones was tested. CI-934 was the most active compound against Gram-positive isolates, such as staphylococci (MIC 90 = 0.25 microgram/ml), and enterococci (MIC 90 = 0.5 microgram/ml). CI-934 was the least active of these drugs against Pseudomonas spp. (MIC 90 = greater than 8.0 micrograms/ml). Against all other organisms CI-934 was very effective, being most comparable with enoxacin. With a selected group of isolates, CI-934 demonstrated high activity against Haemophilus influenzae (MIC 90 = 0.06 microgram/ml), Neisseria meningitidis and N. gonorrhoeae (MIC 90 = 0.13 microgram/ml), Listeria monocytogenes (MIC 90 = 1.0 microgram/ml), methicillin-resistant staphylococci (MIC 90 = 0.13 microgram/ml), and modest activity against anaerobes. Disk diffusion susceptibility testing of CI-934 was evaluated using 3-, 5-, and 10-micrograms disks. Because of its lower interpretive error rate, the 3-micrograms disk is tentatively recommended. With less than or equal to 2 micrograms/ml and greater than 4 micrograms/ml as the susceptible and resistant MIC breakpoints, the corresponding 3-micrograms disk zone diameters breakpoints are greater than or equal to 15 mm and less than or equal to 11 mm. Because most isolates of Pseudomonas spp. are not susceptible to CI-934 and the zone size interpretive error rate is particularly high (33%) with Pseudomonas spp., we suggest that isolates of this genus not be tested for clinical purposes.

Anti-Bacterial Agents↗
PubMed1987

Antimicrobial activity of Ro 19-5247 (T-2525), a new oral cephalosporin, tested against 7,745 recent clinical isolates.

The susceptibility testing of 7,745 recent clinical isolates from four medical centers showed Ro 19-5247 to be eight- to greater than 64-fold more active than cephalexin against the Enterobacteriaceae. Ro 19-5247 was comparable with cephalexin in anti-staphylococcal activity (MIC50, 4.0 micrograms/ml) and fourfold more active than cefixime. None of the oral cephalosporins were effective (MIC50, greater than 32 micrograms/ml) against enterococci, Pseudomonas aeruginosa and P. maltophilia. beta-lactamase hydrolysis experiments failed to demonstrate significant Ro 19-5247 inactivation by ten commonly encountered chromosomal- or plasmid-mediated enzymes (P99, K1, K14, TEM, CARB, OXA).

Bacteria↗
PubMed1987

Effect of beta-lactamase inhibitors on the antimicrobial activity of cefoperazone, cefotaxime, and ceftizoxime against aerobic and anaerobic beta-lactamase producing bacteria.

Clavulanic acid (2.0 micrograms/ml) lowered the minimal inhibitory concentrations (MICs) of ceftizoxime and cefotaxime against 49 strains of the Bacteroides fragilis group by a mean of 4.0 and 3.4 log2 concentrations, respectively. Sulbactam plus ceftizoxime gave almost identical results. Sulbactam lowered cefoperazone MICs by a mean of 2 log2 concentrations. Against 52 aerobic and facultative isolates producing a variety of beta-lactamase types, the use of beta-lactamase inhibitors (sulbactam) was most effective in reducing the MICs of cefoperazone.

Bacteria, Aerobic↗
PubMed1987

In vitro evaluations of U-76,252 (CS-807): antimicrobial spectrum, beta-lactamase stability, and enzyme inhibition.

Compound U-76,252 (Upjohn) is a cephalosporin ester that enhances oral absorption of the active free acid cephem, U-76,253. The active form structurally resembles parenteral aminothiazolyl-methoxyimino cephalosporins such as cefotaxime and its desacetyl metabolite. The g-negative antimicrobial activity of U-76,253 A (sodium salt of U-76,253) was most similar to that of cefixime and more potent than that of cefaclor or cefuroxime among the orally administered cephalosporins. Against g-positive bacteria, U-76,253 A was more active than cefixime. U-76,253 A was relatively stable to hydrolysis by five beta-lactamases (Type Ia, TEM-1, K1, CARB-2, and OXA-1), a stability most similar to cefotaxime and superior to that of cefaclor. Only the Type Ia (P99) enzyme was significantly inhibited by U-76,253 (IC 50 = 2.0 microM).

Anti-Bacterial Agents↗
PubMed1987

RO 23-6240 (AM-833), a new fluoroquinolone: in vitro antimicrobial activity and tentative disk diffusion interpretive criteria.

The susceptibility of over 7000 recent clinical bacterial isolates to RO 23-6240, a new trifluorinated quinolone, was determined at four medical centers. Over 99% of Enterobacteriaceae and 97% of staphylococci were inhibited by less than or equal to 2.0 micrograms/ml of RO 23-6240. Only 71% of Pseudomonas spp. were inhibited by this concentration. Streptococci and enterococci were resistant to RO 23-6240. Clinical isolates of Haemophilus spp., pathogenic Neisseria spp., and Branhamella catarrhalis were inhibited by less than or equal to 0.25 micrograms/ml of RO 23-6240. This drug's antibacterial activity was comparable with that of enoxacin and norfloxacin, but was less than that of ciprofloxacin against most species. Using less than or equal to 2.0 micrograms/ml and greater than or equal to 8.0 micrograms/ml as the susceptible and resistant MIC breakpoints for RO 23-6240, the regression analysis-derived disk diffusion zone diameter breakpoints for the 5 micrograms disk are: Susceptible greater than or equal to 19 mm intermediate 16-18 mm, and resistant less than or equal to 15 mm.

Anti-Bacterial Agents↗
PubMed1987

Antimicrobial activity of coumermycin and recommendations for disk diffusion tests with 5- and 15-micrograms disks.

Coumermycin was found to be extremely active against methicillin-susceptible and -resistant Staphylococcus spp. (MIC 90, less than or equal to 0.002 microgram/ml). Vancomycin and coumermycin were equally active against Streptococcus spp. (MIC 90s, 0.5 microgram/ml) and both were superior to fusidic acid (MIC 90, 8.0 micrograms/ml). The enterococci had the highest MICs for all three drugs. Disk diffusion susceptibility tests using either 5 or 15 micrograms coumermycin disks seem reliable. The tentative interpretive breakpoints for testing the Staphylococcus spp. only are: 5 micrograms disk-susceptible greater than or equal to 17 and resistant less than or equal to 13 mm; 15 micrograms disk-susceptible greater than or equal to 20 mm and resistant less than or equal to 16 mm. These zone criteria have approximate coumermycin MIC correlates of less than or equal to 0.12 microgram/ml for susceptible and greater than or equal to 0.5 microgram/ml for resistant.

Aminocoumarins↗
PubMed1987

Quality control limits for microdilution susceptibility tests with aztreonam, imipenem, ceftriaxone, ceftazidime, ceftizoxime, cefuroxime, and cefonicid.

A six-laboratory collaborative study was performed in order to define quality control limits for microdilution tests with seven new beta-lactams (aztreonam, imipenem, ceftriaxone, ceftazidime, ceftizoxime, cefuroxime, and cefonicid). Four standard control strains were tested and the expected MIC limits for each of the appropriate drug-microorganism combinations were defined.

Anti-Bacterial Agents↗
PubMed1987

Resistance to ten different fluoroquinolone antibiotics following in vitro exposures to nalidixic acid.

Ten different fluoroquinolone antibiotics were tested against selected Enterobacteriaceae. Against nalidixic acid-resistant clinical isolates, minimal inhibitory concentrations for all 10 drugs were eightfold to 32-fold greater than those against comparable nalidixic acid-susceptible strains. When the latter strains were serially exposed to increasing concentrations of nalidixic acid, susceptibility to all 10 fluoroquinolones decreased as resistance to nalidixic acid and cinoxacin was acquired in vitro.

Anti-Bacterial Agents↗
PubMed1987

Bactericidal activities of ten different fluoroquinolones against selected Enterobacteriaceae.

Ten fluoroquinolone compounds and two other 4-quinolones were tested in a microdilution system. Minimal inhibitory concentrations and minimal bactericidal concentrations were determined with 1 X 10(7) and 5 X 10(5) colony forming units per milliliter. All 12 compounds were bactericidal. Continued inhibition by drug carried over in the subcultured samples was documented and that represents a potential source of technical error that needs to be controlled when determining minimal bactericidal concentrations for these extremely potent drugs.

Anti-Bacterial Agents↗
PubMed1987

Ceftizoxime and cefoxitin susceptibility testing against anaerobic bacteria: comparison of results from three NCCLS methods and quality control recommendations for the reference agar dilution procedure.

Ceftizoxime and cefoxitin (control) were tested against 99 anaerobic bacteria using three commonly used susceptibility testing methods. The cefoxitin MIC results with the National Committee for Clinical Laboratory Standards (NCCLS) reference agar dilution (RAD) method and the broth microdilution (BMD) method did not differ by more than one log2 dilution step. However, the ceftizoxime BMD MIC results were 2- to 4-fold lower than those produced by the RAD procedure. Broth disk elution (BDE) tests for both cephalosporins (ceftizoxime and cefoxitin) had very high rates of false-susceptible and false-resistant error when compared to the RAD MICs: the BDE tests are not recommended for either cephalosporin. Findings indicate that because of method and possible medium or technical variability, ceftizoxime MICs should be determined only by the NCCLS RAD method. Also, cefoxitin susceptibility should be assessed primarily by RAD or BMD procedures. This should minimize confusion related to ceftizoxime's spectrum and activity against anaerobic bacteria compared to similar beta-lactam drugs. Ceftizoxime quality control guidelines were established for Bacteroides fragilis (ATCC 25285): mode, 64 micrograms/ml, range 32-128 micrograms/ml. Other control strains were not reliable.

Agar↗
PubMed1987

Comparative antimicrobial activity of aminothiazolyl methoxyimino cephalosporins against anaerobic bacteria, including 100 cefoxitin-resistant isolates.

Three aminothiazolyl methoxyimino cephalosporins (ceftizoxime, ceftriaxone, and cefotaxime with and without its metabolite) were tested against 500 strains of anaerobic bacteria using the NCCLS reference agar dilution procedure. Eighty-seven percent of all strains tested were from the Bacteroides fragilis group. When tested against a collection of 100 cefoxitin-resistant isolates, ceftizoxime and the cefotaxime/desacetyl-cefotaxime combination were the most active in vitro, inhibiting 32-38% of strains. Ceftriaxone inhibited the greatest number (87%) of cefoxitin-susceptible anaerobes at less than or equal to 32 micrograms/ml. A regional variation in the activity of these drugs was confirmed when an additional 300 isolates were examined from three medical centers. Cefotaxime, ceftizoxime, and ceftriaxone were essentially equal in overall antimicrobial activity, although each drug was judged the best at one of the three locations. Cefoxitin resistance (MIC greater than or equal to 32 micrograms/ml) was consistent among the institutions at a 25% incidence for all organisms tested, and 28% cefoxitin resistance among the B. fragilis group strains. Cefoxitin resistance was not determined to be associated with a beta-lactamase mechanism, but ceftriaxone and other aminothiazolyl cephems were hydrolyzed, thus elevating their MICs. Regional variation in anaerobic organism susceptibility to cephamycins and cephalosporins in company with the variable beta-lactam resistance mechanisms seems to require periodic, epidemiologic monitoring of in vitro drug activity by appropriate methods to assure continued antimicrobial efficacy.

Bacteria, Anaerobic↗
PubMed1987

Antimicrobial activity of imipenem and SCH34343 against Legionella species.

Twenty-seven Legionella spp. strains were tested against four beta-lactams, erythromycin and rifampin by a buffered ACES-yeast extract broth microdilution method. The minimum concentrations inhibiting 90% of strains were imipenem 0.06 micrograms/ml, SCH34343 0.25 micrograms/ml, amoxicillin 0.5 micrograms/ml, cefotaxime less than or equal to 0.12 micrograms/ml, erythromycin 0.25 micrograms/ml, and rifampin less than or equal to 0.008 micrograms/ml.

Amoxicillin↗