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T L Gavan

Publications and source records attributed to T L Gavan.

At least 55 records · Page 3Linked to original sources
PubMed1982

Evaluation of the MICUR system for quantitative antimicrobial susceptibility testing: a multiphasic comparison with reference methods.

Four laboratories participated in a three-phase study to evaluate the MICUR antimicrobial broth microdilution system (Boehringer Mannheim Diagnostics, Inc., Houston, Tex.). The dried-antimicrobial agent MICUR system was compared with a reference broth microdilution method (National Committee for Clinical Laboratory Standards) by using 304 recently isolated clinical strains and two collections of stock or challenge organisms. Of 7,092 minimum inhibitory concentration (MIC) datum pairs derived from the clinical isolates, 96.6% were within an acceptable (+/- 1 log2 dilution) range. MICUR MICs agreed with the reference broth microdilution method MICs in 95.3% of 6,840 MIC pair determinations performed on stock or challenge cultures. The MICUR intralaboratory reproducibility within +/- 1 log2 dilution step for the clinical isolates was 98.4%. The MICUR intralaboratory and interlaboratory reproducibilities for 26 stock cultures were 98.4 and 95.1%, respectively. For 180 challenge cultures (4,199 MIC pairs) which were included in the MICUR testing to provide a wide variety of antimicrobial susceptibility and resistance patterns, the results for 92.5% were in close agreement with the reference broth microdilution results. No specific resistance mechanism went unrecognized by this new commercial system. The MICUR system gives comparable MIC results when evaluated against the reference broth microdilution method, and it would be acceptable for use in clinical microbiology laboratories.

Anti-Bacterial Agents↗
PubMed1982

Evaluation of the MS-2 urine screening method for detection of bacteriuria.

A collaborative evaluation of the MS-2 urine screening system indicated that the automated method could successfully identify at least 84% of urine specimens that contained greater than or equal to 10(5) colony-forming units per ml. Most specimens not detected as positive by the system contained primarily diphtheroids and yeasts. Excluding those specimens which contained diphtheroids and yeasts, the MS-2 system correctly identified as positive 94.8% of specimens that contained greater than or equal to 10(5) colony-forming units per ml and as negative 96.1% of specimens that contained less than 10(4) colony-forming units per ml. The automated system is an attractive method for the screening of urine specimens for significant bacteriuria.

Bacteriuria↗
PubMed1981

Evaluation of the Sceptor microdilution antibiotic susceptibility testing system: a collaborative investigation.

A multiwell, dried antimicrobial agent susceptibility test system, Sceptor (BBL Microbiology Systems, Cockeysville, Md.), was tested. The system was compared directly with a reference microdilution method by using two collections of stock cultures and 305 fresh clinical isolates. Sceptor was found to be in agreement (+/- log2 dilution) with the reference microdilution method in 96.9 to 98.3% of 9,840 minimal inhibitory concentration determinations performed on stock strains and 95.0% of 7,308 minimal inhibitory concentrations obtained from the clinical isolates. The intralaboratory and interlaboratory reproducibility on stock strains was 97.6 and 97.2%, respectively. The intralaboratory reproducibility for the clinical isolates was 96.9%. Sceptor accurately categorized representative challenge strains of methicillin-resistant staphylococci, beta-lactamase-producing bacteria, organisms producing other antimicrobial agent-inactivating enzymes, and permeability mutants as resistant. Only 0.2% very major errors (false-sensitive minimal inhibitory concentrations by Sceptor) were identified among the clinical isolate test results, the majority being clinically insignificant. The product is accurate and reliable, has a long shelf life, and seems applicable for routine use in clinical laboratories.

Anti-Bacterial Agents↗
PubMed1981

Quality control limits for ampicillin, carbenicillin, mezlocillin, and piperacillin disk diffusion susceptibility tests: a collaborative study.

A multilaboratory in vitro study was carried out to determine disk diffusion susceptibility testing quality control limits for two new semisynthetic penicillins, mezlocillin and piperacillin. Existing limits for carbenicillin and ampicillin were reevaluated. Multiple tests (which followed standards set by the National Committee for Clinical Laboratory Standards ASM-2 revised) were performed in nine laboratories by different technologists using disks and Mueller-Hinton agar from different manufacturers. Clinically significant differences between disks produced by different manufacturers were not noted. Inhibitory zone diameter measurements from all laboratories were analyzed, and upper and lower control limits were established by using the overall median +/-0.5 the median range of the individual laboratory measurements as determining parameters. Close agreement of the data in this study with the results of national proficiency testing and quality control programs for ampicillin and carbenicillin supports the validity of our approach to making initial recommendations for quality control guidelines for new antimicrobial agents.

Ampicillin↗
PubMed1980

Evaluation of the Sensititre system for quantitative antimicrobial drug susceptibility testing: a collaborative study.

This three-center collaborative study was conducted to evaluate samples of Sensititre antimicrobial microdilution panels (GIBCO/INVENEX). Sensititre minimum inhibitory concentrations of 27 bacterial isolates were compared with those obtained by a reference microdilution method. The Sensititre and microdilution minimum inhibitory concentrations were equivalent within +/- 1 dilution in 87.6% of the comparable test results. Intralaboratory reproducibilities of the Sensititre and microdilution endpoints were equivalent with 80.4 and 82.4%, respetively, of on-scale endpoints in absolute agreement. Sensititre was more reproducible among laboratories, with nearly a 10% greater agreement of triplicate results. The Sensititre microdilution test as evaluated gave results which were essentially equivalent to those obtained with a standardized microdilution method.

Aminoglycosides↗
PubMed1980

Cefoperazone (T-1551), a new semisynthetic cephalosporin: comparison with cephalothin and gentamicin.

The in vitro activity of cefoperazone (T-1551) against almost 9,000 recent clinical isolates at six institutions was tested and compared with that of cephalothin and gentamicin. The modal minimum inhibitory concentrations of cefoperazone were 16- and 4-fold less than those of cephalothin and gentamicin, respectively, against 5,503 strains of Enterobacteriaceae. Species normally resistant to cephalothin, such as indole-positive protease and enterobacters, were almost universally susceptible to cefoperazone. Cefoperazone demonstrated activity comparable to gentamicin against Pseudomonas aeruginosa and other pseudomonads.

Bacteria↗
PubMed1980

Moxalactam (LY127935), a new semisynthetic 1-oxa-beta-lactam antibiotic with remarkable antimicrobial activity: in vitro comparison with cefamandole and tobramycin.

Moxalactam (LY127935) exhibited greater in vitro activity than cefamandole and tobramycin against clinical isolates of Enterobacteriaceae, Aeromonas hydrophila, and Pseudomonas maltophilia. The activities of the three drugs against other microorganisms were as follows: for staphylococci, cefamandole = tobramycin greater than moxalactam; for streptococci, cefamandole greater than moxalactam greater than tobramycin; and for Pseudomonas aeruginosa, tobramycin greater than moxalactam greater than cefamandole. Moxalactam also demonstrated significant activity against the Bacteroides fragilis group and other anaerobes. Moxalactam was comparable to cefotaxime (HR756) in its inhibition of cephalothin-resistant and aminoglycoside-resistant clinical isolates.

Aminoglycosides↗
PubMed1980

Rapid determination of minimum inhibitory concentrations of antimicrobial agents by the Autobac method: a collaborative study.

Four laboratories collaborated in an evaluation of the Autobac minimum inhibitory concentration (MIC) test system. The MICs of ranges of MICs determined in this system were compared with the MICs obtained with a microtube modification of the International Collaborative Study broth dilution technique. A total of 1,260 strains, mostly recent clinical isolates and including multiresistant strains, were tested by the four laboratories against 10 antibiotics; 9,360 separate MIC determinations were made. There was an overall agreement of approximately 95% between the two methods. Levels of agreement below 80% were obtained with only 4 of the 104 antibiotic-species pairs. In only one of the four major organism groups (staphylococci and penicillin G) was agreement less than 85%. There was a symmetrical distribution of MIC differences between the two methods. Tests with 56 selected strains were performed in each of four laboratories in an inter- and intra-laboratory reproducibility study. Both methods showed a standard deviation (both inter- and intra-laboratory) of one-half of a twofold dilution step. The Autobac method was actually less variable than the reference method and had equivalent reproducibility. This was particularly true when the Autobac system was operated so that the results generated permitted calculations of MICs via regression analysis.

Anti-Bacterial Agents↗
PubMed1980

Cefotaxime: in vitro activity and tentative interpretive standards for disk susceptibility testing.

Tested against 9,412 recent clinical isolates, cefotaxime exhibited 8 to 64 times greater activity against the Enterobacteriaceae than did cephalothin and two to four times greater activity against Pseudomonas aeruginosa, but only one-half to one-eighth the activity of cephalothin against staphylococci. Using 420 different clinical isolates, but with comparable minimal inhibitory concentration (MIC) distributions, disk diffusion-MIC regression analyses were performed, using 5- and 30-micrograms cefotaxime disks. Cefotaxime MIC susceptible and resistant breakpoints of less than or equal to 8 and greater than 32 micrograms/ml are tentatively proposed. Based on the MIC breakpoints, the data showed the best discrimination among the three susceptibility categories (susceptible, indeterminate, and resistant) when the 30-micrograms cefotaxime disk was used. The zone diameter breakpoints as determined by the error rate-bounded method and regression analysis were greater than or equal to 23 mm for susceptible, 15 to 22 mm for indeterminate, and less than or equal to 14 mm for resistant.

Bacteria↗
PubMed1980

Collaborative investigation of the AutoMicrobic System Enterobacteriaceae biochemical card.

The Enterobacteriaceae biochemical card used in six separate laboratories to identify 170 representatives of Enterobacteriaceae. The AutoMicrobic System (Vitek Systems, Inc.) performed with an accuracy of 97.8% as compared with 98.1% by the standard method selected and 97.6% by a commerically prepared manual system approach. During this time, 5,450 clinical isolates belonging to Enterobacteriaceae were analyzed. Compared with the routine methods used in the various laboratories, the AutoMicrobic System identified 96.4% correctly

Bacteriological Techniques↗
PubMed1979

Interpretation of the disk diffusion susceptibility test for amikacin: report of a collaborative study.

Because excessively high rates of false resistance have been encountered with the 10-mug amikacin disk in diffusion susceptibility tests, a study was performed to examine existing zone diameter interpretative criteria and to compare the accuracy of 10- and 30-mug amikacin disks by the error rate-bounded classification scheme. Although current zone diameter interpretative criteria eliminate false susceptibles, there is an unacceptably high rate of false resistants. This problem can be resolved in most instances by revising the zone diameter interpretative criteria for the 10-mug disk (resistant, </=9 mm; indeterminate, 10 to 11 mm; susceptible, >/=12 mm) or, preferably, by replacing the 10-mug disk with a 30-mug disk and adopting new interpretative criteria (resistant, </=14 mm; indeterminate, 15 to 16 mm; susceptible, >/=17 mm). Because of significant differences in performance among media, it is necessary to include Pseudomonas aeruginosa ATCC 27853 among controls routinely tested and to exclude from use lots of Mueller-Hinton agar yielding results outside the 75% tolerance (90% confidence) limits for amikacin.

Amikacin↗