Biomedical subjects

L A Maher

Publications and source records attributed to L A Maher.

24 records · Page 2Linked to original sources

PubMed1988

National collaborative study of the prevalence of antimicrobial resistance among clinical isolates of Haemophilus influenzae.

A total of 2,811 clinical isolates of Haemophilus influenzae were obtained during 1986 from 30 medical centers and one nationwide private independent laboratory in the United States. Among these, 757 (26.9%) were type b strains. The overall rate of beta-lactamase-mediated ampicillin resistance was 20.0%. Type b strains were approximately twice as likely as non-type b strains to produce beta-lactamase (31.7 versus 15.6%). The MICs of 12 antimicrobial agents were determined for all isolates. Ampicillin resistance among strains that lacked beta-lactamase activity was extremely uncommon (0.1%). Percentages of study isolates susceptible to cefamandole, cefaclor, cephalothin, and cephalexin were 98.7, 94.5, 87.3, and 43.3%, respectively. For 14 strains (0.5% of the total), chloramphenicol MICs were greater than or equal to 8.0 micrograms, and thus the strains were considered resistant. All of these resistant strains produced chloramphenicol acetyltransferase. In addition, all 14 strains were resistant to tetracycline; 11 produced beta-lactamase. The percentage of isolates susceptible to tetracycline was 97.7%. In contrast, erythromycin and sulfisoxazole were relatively inactive. The combination of erythromycin-sulfisoxazole (1/64) was more active than erythromycin alone but essentially equivalent in activity to sulfisoxazole alone. Finally, small numbers of clinical isolates of H. influenzae were resistant to trimethoprim-sulfamethoxazole and rifampin.

Ampicillin Resistance↗

PubMed1988

Salt-supplemented medium for testing methicillin-resistant staphylococci with newer beta-lactams.

The addition of 2% NaCl to cation-supplemented Mueller-Hinton broth (CSMHB) was evaluated for microdilution testing of the susceptibility of staphylococci to five cephalosporins, imipenem, amoxicillin-clavulanate, and ticarcillin-clavulanate. With Staphylococcus aureus, NaCl improved the recognition of methicillin (oxacillin) resistance to cefamandole, imipenem, or ticarcillin-clavulanate. Resistance to amoxicillin-clavulanate was readily determined, irrespective of the presence of added salt. The addition of 2% NaCl to CSMHB did not significantly improve detection of resistance to any of the beta-lactams among coagulase-negative staphylococci. Since the addition of NaCl did not have significant adverse effects on tests with coagulase-negative staphylococci, the routine addition of 2% NaCl to oxacillin or methicillin tests with staphylococci may be justifiable on the basis of convenience or standardization. However, addition of NaCl to susceptibility tests of other beta-lactams does not consistently improve recognition of resistance among staphylococci and thus cannot be recommended for routine use.

Amoxicillin↗

PubMed1988

Disk diffusion interpretive criteria for extended-spectrum cephalosporins with Haemophilus influenzae.

Disk diffusion interpretive zone size criteria for use with Haemophilus test medium are proposed for five extended-spectrum cephalosporins. With cefuroxime, zones greater than or equal to 24 mm in diameter indicated susceptibility, while zones less than or equal to 20 mm implied resistance. With cefotaxime, ceftizoxime, and ceftriaxone, a single susceptible-zone size, greater than or equal to 26 mm, is proposed.

Cephalosporins↗

PubMed1987

In vitro activity of LY146032 (daptomycin) against selected aerobic bacteria.

The in vitro activity of the new lipopeptide antibiotic LY146032 was generally four-fold greater (MIC 90 less than or equal to 0.5 microgram/ml) than that of vancomycin against methicillin-susceptible or methicillin-resistant Staphylococcus aureus and coagulase-negative species of Staphylococcus. Enterococci, Streptococcus bovis, group B and viridans streptococci, and Corynebacterium group J-K isolates were inhibited by less than or equal to 4 micrograms/ml of LY146032, which represented activity equivalent to or greater than that of vancomycin. Unlike vancomycin, LY146032 was bactericidal for Enterococcus faecalis, Enterococcus faecium and Listeria monocytogenes. Due to its bactericidal properties LY146032 appeared to represent an improvement over vancomycin and teicoplanin.

Anti-Bacterial Agents↗

PubMed1987

Improved medium for antimicrobial susceptibility testing of Haemophilus influenzae.

The need for complex growth media has complicated routine susceptibility testing of Haemophilus influenzae because of antagonism of certain antimicrobial agents by the medium or because of difficulties in interpretation of growth endpoints. Haemophilus test medium (HTM) is a simple, transparent medium for broth- or agar-based tests with H. influenzae. HTM incorporates Mueller-Hinton medium with additions of 15 micrograms of hematin per ml, 15 micrograms of NAD per ml, and 5 mg of yeast extract per ml as growth-promoting additives. Agar or broth microdilution MICs of 10 antimicrobial agents for a collection of 179 H. influenzae isolates determined by using HTM compared favorably with MICs determined by the conventional agar or broth dilution methods recommended by the National Committee for Clinical Laboratory Standards. Disk diffusion tests performed with HTM allowed accurate categorization of susceptible and resistant strains and were easier to interpret than tests performed with Mueller-Hinton chocolate agar. A particular advantage of HTM was the reliability of broth- or agar-based test results with trimethoprim-sulfamethoxazole. The results of the study suggest modification of current National Committee for Clinical Laboratory Standards MIC-interpretive criteria for H. influenzae with amoxicillin-clavulanate, chloramphenicol, and trimethoprim-sulfamethoxazole. Error rate-bounded analysis of MICs and disk diffusion zone sizes also suggest modified zone-interpretive criteria for ampicillin, amoxicillin-clavulanate, chloramphenicol, and tetracycline with HTM or conventional media. Interpretive zone sizes are newly proposed for cefaclor and rifampin disk diffusion tests.

Anti-Bacterial Agents↗

PubMed1980

Evaluation of cefamandole susceptibility testing of Enterobacteriacea by the autobac 1 system.

A total of 509 clinical isolates of Enterobacteriaceae were tested for susceptibility to cefamandole by Autobac 1 and Bauer-Kirby disk diffusion methods, using commercially available 30-micrograms cefamandole disks. Minimal inhibitory concentrations were determined for all organisms showing major or very major discrepancies. Overall agreement between Autobac 1 and disk diffusion was 89.8%, with 5.1% major or very major and 5.1% minor discrepancies. When considering only the genera for which 20 or more isolates were tested, overall agreement was 90.8%. Discrepancies for Escherichia coli showed a trend toward resistance by Autobac 1, with minimal inhibitory concentrations generally in agreement with disk diffusion results. No trends were detected for other genera. The rate of agreement was lower for Enterobacter species (75.4%), but minimal inhibitory concentrations, determined for all discrepancies in this genus, agreed with Autobafc 1 as often a with disk diffusion results.

Cefamandole↗