Biomedical subjects

A L Barry

Publications and source records attributed to A L Barry.

At least 307 records · Page 17Linked to original sources

PubMed1984

Disk diffusion susceptibility testing of ticarcillin plus clavulanic acid.

Disk diffusion susceptibility testing of ticarcillin plus the beta-lactamase inhibitor clavulanic acid was performed on 489 clinical isolates, and the results were compared with reference broth microdilution susceptibilities. Four different disks containing 75 micrograms of ticarcillin plus 2.5, 5, 10, and 15 micrograms of clavulanic acid were evaluated. Based on test performance and clavulanic acid stability, the 75-10-micrograms disk is recommended. Interpretive criteria for ticarcillin as published by the National Committee for Clinical Laboratory Standards appear to be satisfactory for the combination drug, but because the number of ticarcillin-clavulanic acid-resistant isolates was small, this proposal must be considered only tentative.

Bacteria↗

PubMed1984

Interpretive criteria and tentative quality control limits for apalcillin disk susceptibility tests.

In vitro studies with 661 bacterial isolates were performed to establish interpretive criteria. In addition, a nine-laboratory study was performed to establish quality control limits for tests with 100-micrograms apalcillin disks and to confirm testing criteria for tests with 100-micrograms piperacillin disks. The two drugs were very similar, and nearly identical criteria were recommended for interpretation and for control of the two types of disks. Neither disk is recommended for testing Staphylococcus spp. or Haemophilus spp.; with other microorganisms, zone size limits of less than or equal to 13 mm (resistant) and greater than or equal to 18 mm (susceptible) are proposed for tests with 100-micrograms apalcillin disks.

Ampicillin↗

PubMed1984

Disk diffusion testing, quality control guidelines, and antimicrobial spectrum of HR810, a fourth-generation cephalosporin, in clinical microbiology laboratories.

HR810 is a new, very broad-spectrum cephalosporin with significant activity against members of the family Enterobacteriaceae, pseudomonads, gram-positive cocci, and anaerobes that is generally greater than the third-generation cephalosporins (99.6% of 4,128 clinical facultative enteric isolates were inhibited by less than or equal to 8.0 micrograms of HR810 per ml). Tests and statistical methods to establish in vitro antimicrobial susceptibility test criteria favor tentative breakpoints of greater than or equal to 18 mm (less than or equal to 8.0 micrograms/ml) as susceptible and less than or equal to 14 mm (greater than or equal to 32 micrograms/ml) as resistant. This provides a 93.7 to 98.3% absolute interpretive accuracy. Several preliminary ranges for zone sizes obtained with quality control organisms are proposed for the 30-micrograms HR810 disk diffusion test used during the clinical trials.

Bacteria↗

PubMed1984

Quality control of susceptibility tests with 5-micrograms trimethoprim disks.

In 1981 and again in 1984, we performed multi-laboratory studies to develop quality control limits for susceptibility tests with 5-micrograms trimethoprim disks. Zone size limits of 21 to 28 mm are recommended for tests with Escherichia coli ATCC 25922, and limits of 19 to 26 mm are recommended for tests with Staphylococcus aureus ATCC 25923. For screening Mueller-Hinton agar, tests with Streptococcus faecalis ATCC 33186 or ATCC 29212 are recommended: zones should be fairly clear and greater than or equal to 22 mm (trimethoprim disks) or greater than or equal to 24 mm (trimethoprim-sulfamethoxazole disks).

Drug Combinations↗

PubMed1984

Determination of susceptibility of anaerobic bacteria to cefotetan and cefoxitin by the thioglycolate disk elution method.

The in vitro activities of two cephamycins, cefotetan and cefoxitin, against 107 anaerobic bacteria were evaluated. The aerobically incubated thioglycolate disk elution technique of Kurzynski et al. (Antimicrob. Agents Chemother. 10:727-732, 1976) was also evaluated to establish the appropriate number of 30-micrograms disks to be added to each tube, assuming that strains with MICs of less than or equal to 16 micrograms/ml are susceptible. Optimal predictive values were obtained when two tubes were prepared for each antimicrobial agent, one with two 30-micrograms disks and the other with three 30-micrograms disks. After 48 h of incubation, resistant strains grew in both tubes and susceptible strains provided no growth or growth less than or equal to 50% of that in the control broth. Growth in one tube but not in the other was considered an equivocal test result indicating the need for additional tests; 5 to 7% of our strains gave equivocal results. Reproducibility studies confirmed that broth microdilution tests were more reproducible than disk elution susceptibility tests.

Bacteria, Anaerobic↗

PubMed1984

Interpretive standards and quality control guidelines for imipenem susceptibility tests with 10-micrograms disks.

Tests with 10-micrograms imipenem disks accurately categorized 98.5% of 551 bacterial isolates when interpretive breakpoints of less than or equal to 13 mm for resistant and greater than or equal to 16 mm for susceptible were used. Because a sufficient number of resistant or moderately susceptible strains were not available for testing, these interpretive standards must be considered tentative. Quality control limits for tests with Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853 are 26 to 32 and 20 to 28 mm, respectively. Zones obtained with Staphylococcus aureus ATCC 25923 were too large and variable to be useful for quality control purposes.

Anti-Bacterial Agents↗

PubMed1984

The activity of cefotaxime and desacetylcefotaxime alone and in combination against anaerobes and staphylococci.

Cefotaxime (CTX) and desacetylcefotaxime (des-CTX) alone and in combination were tested against anaerobic bacteria collected from clinical infections from several geographically diverse medical centers. The CTX minimum inhibitory concentration (MIC) inhibiting 50% of tested Bacteroides fragilis strains was in the moderately susceptible range (32 micrograms/ml), but when placed in combination with des-CTX it had a potency compatible to cefoxitin (MIC50, 8.0 micrograms/ml). Other B. fragilis group species (B. distasonis and B. vulgatus) were also susceptible to CTX and des-CTX alone at the MIC50 level. MIC90 statistics for CTX, cefoxitin, and ticarcillin were generally in the resistant range. Synergy studies showed that 80% of tested anaerobes were synergistically killed by the combination of CTX and des-CTX. Most of these strains had their synergy occur at drug levels that could be achieved in vivo. A large number of the B. thetaiotaomicron strains must be considered resistant to the combination because of the very high levels of des-CTX required to produce synergistic killing. Other drugs routinely used for anaerobic infections (clindamycin, chloramphenicol, and metronidazole) also had elevated B. thetaiotaomicron MICs. Endemic difference in susceptibility to the beta-lactam drugs were observed, especially the CTX-des-CTX combination. The combination and other beta-lactams were most usable for strains isolated from the Portland metropolitan area, were moderately active against those from Cleveland, and were rarely usable on Bacteroides isolates at Northwestern in Chicago. Laboratories are urged to monitor the cephalosporin and semisynthetic penicillin in vitro efficacy and not rely on published statistics. Staphylococcus aureus strains were susceptible to CTX alone, but were even more susceptible (two- to fourfold reduction in MICs) when used in combination with des-CTX. These data show CTX to be the most active antistaphylococcal compound among the new cephalosporins and to be comparable to cefamandole and cefuroxime, but superior to the anaerobe-active cefoxitin.

Bacteria, Anaerobic↗

PubMed1984

Preparation of amniotic membranes for surgical use with antibiotic solutions.

A comparative study was conducted to investigate the effectiveness of antibiotic solutions for disinfecting vaginally delivered amniotic membranes. The microbial flora of eight amniotic membranes was defined and six antibiotic solutions were tested for their effectiveness in eliminating aerobic and anaerobic organisms. A solution containing 600 micrograms lincomycin HCl/ml, 500 micrograms neomycin sulfate/ml, 25 micrograms polymyxin B sulfate/ml, and 25 micrograms amphotericin B sulfate/ml in 0.5N saline was found to be capable of disinfecting amniotic membranes stored at 4 degrees C for 24 hours. This solution is now being used to disinfect surgically used amniotic membranes at our institution.

Amnion↗

PubMed1983

Ceftriaxone: a summary of in vitro antibacterial qualities including recommendations for susceptibility tests with 30-micrograms disks.

The new aminothiazoyl-cephalosporin, ceftriaxone (Ro 13-9904), was found to have excellent inhibitory activity against the Enterobacteriaceae (minimum inhibitory concentration needed to inhibit 50% of isolates (MIC50) less than or equal to 0.004-0.5 microgram/ml, Haemophilus influenzae (MIC50 less than or equal to 0.004 micrograms/ml), Neisseria species (MIC50 less than or equal to 0.001 microgram/ml), pneumococci (MIC50 0.25 micrograms/ml), Staphylococcus aureus (MIC50 2.0 micrograms/ml), and Streptococcus pyogenes (MIC50 0.015 micrograms/ml). Ceftriaxone was less effective against Acinetobacter species, Pseudomonas aeruginosa, and other Pseudomonas species (MIC50 8.0-16 micrograms/ml). Methicillin-resistant S. aureus and enterococci were not significantly inhibited by ceftriaxone. Ceftriaxone was very resistant to beta-lactamase hydrolysis, although the type IV cephalosporinase minimally destroyed the compound at 16.4-19.9% of the rates for cephaloridine. Type I cephalosporinases were inhibited by ceftriaxone and related enzyme-stable cephalosporins. Based on analysis of disk-MIC regression statistics, tentative recommendations for the disk test of the National Committee for Clinical Laboratory Standards are 21 mm or more = susceptible, 14-20 mm = moderately susceptible, and 13 mm or less = resistant. These criteria produce interpretive accuracy of more than 92%, with very rare major errors. Ceftriaxone was comparable to cefotaxime in spectrum and activity, thus allowing the use of the "spectrum-class" concept (for example, cefotaxime tests in vitro to predict ceftriaxone susceptibility, and vice versa).

Acinetobacter↗

PubMed1983

Norfloxacin (MK-0366, AM-715): in vitro activity and cross-resistance with other organic acids including quality control limits for disk diffusion testing.

Norfloxacin is a new organic acid antimicrobic with an expanded spectrum that includes Staphylococcus spp, most Pseudomonas spp, Acinetobacter calcoaceticus ssp anitratus, some streptococci, as well as nearly all enteric bacilli. The drug appears to be bactericidal. Its expanded spectrum suggests that it should be tested separately by disk diffusion or other susceptibility testing methods. Tentative norfloxacin disk test quality control limits were derived from the results of a multi-laboratory study: Escherichia coli, 28-36 mm; S. aureus, 17-28 mm, and Pseudomonas aeruginosa, 22-29 mm.

Acinetobacter↗

PubMed1983

Cefuroxime, cefamandole, cefoxitin, and cephalothin in vitro susceptibility tests: reassessment of the "class representative" concept, confirmation of disk interpretive criteria, and proposed quality control guidelines.

The relationship of cefuroxime in vitro susceptibility tests to similar cephalosporins (cefamandole, cefoxitin, and cephalothin) was evaluated using 396 recent clinical isolates. The previously published interpretive criteria of greater than or equal to 18 mm (less than or equal to 8.0 micrograms/mL) = susceptible and less than or equal to 14 mm (greater than or equal to 32 micrograms/mL) = resistant for each drug were considered appropriate. The results of all study methods demonstrated cefuroxime to be slightly less active than cefamandole against most species, yet both drugs possessed nearly identical antimicrobial spectra. Cephalothin and cefoxitin were confirmed to have spectra significantly different from cefamandole and from each other, thus requiring separate testing. The application of the "class representative" concept to cefuroxime and cefamandole seems justified. Use of a 30-micrograms cefuroxime disk yielded the best predictive results and minimized the number of false-susceptible (very major) interpretive errors. Quality control guidelines are presented in a tentative form for cefuroxime, and modifications in the cephalothin and cefamandole zone limits are suggested.

Bacteria↗

PubMed1983

In vitro evaluation of Augmentin by broth microdilution and disk diffusion susceptibility testing: regression analysis, tentative interpretive criteria, and quality control limits.

Augmentin (Beecham Laboratories, Bristol, Tenn.), a combination drug consisting of two parts amoxicillin to one part clavulanic acid and a potent beta-lactamase inhibitor, was evaluated in vitro in comparison with ampicillin or amoxicillin or both for its inhibitory and bactericidal activities against selected clinical isolates. Regression analysis was performed and tentative disk diffusion susceptibility breakpoints were determined. A multicenter performance study of the disk diffusion test was conducted with three quality control organisms to determine tentative quality control limits. All methicillin-susceptible staphylococci and Haemophilus influenzae isolates were susceptible to Augmentin, although the minimal inhibitory concentrations for beta-lactamase-producing strains of both groups were, on the average, fourfold higher than those for enzyme-negative strains. Among the Enterobacteriaceae, Augmentin exhibited significantly greater activity than did ampicillin against Klebsiella pneumoniae, Citrobacter diversus, Proteus vulgaris, and about one-third of the Escherichia coli strains tested. Bactericidal activity usually occurred at the minimal inhibitory concentration. There was a slight inoculum concentration effect on the Augmentin minimal inhibitory concentrations. On the basis of regression and error rate-bounded analyses, the suggested interpretive disk diffusion susceptibility breakpoints for Augmentin are: susceptible, greater than or equal to 18 mm; resistant, less than or equal to 13 mm (gram-negative bacilli); and susceptible, greater than or equal to 20 mm (staphylococci and H. influenzae). The use of a beta-lactamase-producing organism, such as E. coli Beecham 1532, is recommended for quality assurance of Augmentin susceptibility testing.

Amoxicillin↗

PubMed1983

In vitro evaluation of three new macrolide antimicrobial agents, RU28965, RU29065, and RU29702, and comparisons with other orally administered drugs.

Three new macrolide drugs (RU28965, RU29065, and RU29702) were compared in vitro with erythromycin and five other orally administered antimicrobial agents by using 733 recent clinical isolates. All of the investigational macrolides had a spectrum very similar to that of erythromycin, but with slightly higher (two- to fourfold) minimum inhibitory concentrations against Haemophilus influenzae, staphylococci, and streptococci including Streptococcus faecalis. RU29065 and RU29702 were more active than erythromycin against Neisseria gonorrhoeae and Neisseria meningitidis. The drugs appeared to be predominantly bacteriostatic and were ineffective against gram-negative bacilli, and their minimum inhibitory concentrations were greatly increased by high inoculum concentrations. Cross-resistance between the macrolides was nearly complete, favoring the use of a single agent for in vitro susceptibility test if in vivo therapeutic differences are not observed.

Administration, Oral↗

PubMed1983

Antimicrobial activity and other in vitro properties of cefoperazone A, the principal metabolite of cefoperazone sodium.

Cefoperazone A, the principal metabolite of cefoperazone, was found to have an antimicrobial activity ranging from slightly below to 16-fold less than that of the parent drug. Like cefoperazone, the metabolite is bactericidal, penetrates well into bacterial cells, and has moderate beta-lactamase stability, some strains of members of the family Enterobacteriaceae produce an inoculum effect on the metabolite activity.

Bacteria↗

PubMed1983

Evaluation of the cefonicid disk test criteria, including disk quality control guidelines.

Cefonicid (SKF 75073) is a second-generation cephalosporin which has a spectrum of antimicrobial activity similar to that of cefamandole, but cefoxitin (a cephamycin) and cephalothin have uniquely different spectra of activity. The second-generation cephalosporins tested displayed comparable susceptibility to beta-lactamases and inhibited type I beta-lactamases. Although cefonicid has a longer serum half-life (3 to 4 h) compared with the currently used drugs, the same minimal inhibitory concentration breakpoints separating susceptible and resistant categories were applied to tests with cefonicid, cefamandole, and cephalothin. Regression analysis of the disk diffusion test results confirmed the use of identical zone size breakpoints for 30-micrograms cefonicid, cefamandole, and cephalothin disks: all three produced similar parabolic regression lines. Further analysis of disk test data confirmed the fact that cefonicid and cefamandole disks might be used interchangeably. But for routine tests, cefonicid disks might be preferred in order to minimize the number of very major (false-susceptible) interpretive errors. Suggested cefonicid 30-micrograms disk interpretive criteria are: susceptible, greater than or equal to 18 mm (less than or equal to 8.0 micrograms/ml), and resistant, less than or equal to 14 mm (greater than 16 micrograms/ml). Quality control zone diameter limits were calculated from data obtained in a multilaboratory collaborative study.

Bacteria↗

PubMed1983

Collaborative evaluation of the microbial profile system for quantitative antimicrobial susceptibility testing.

This three-center collaborative study was conducted to evaluate samples of the Microbial Profile System (MPS) antimicrobial microdilution panels [previously produced by Minnesota Mining & Manufacturing Co., (3M Co.), St. Paul, Minn. and currently produced by Flow Laboratories, Inc., Rockville, Md.). This was a three-phase study. In phase I, the inter- and intralaboratory agreement was determined by using strains with selected ranges of susceptibility. The MPS and reference microdilution minimum inhibitory concentrations were within acceptable variation, +/- 1 dilution for 97.7% for the MPS and 98.8% for the reference microdilution panels for the intralaboratory comparisons. The percentage of strains with minimum inhibitory concentrations in the acceptable range for the interlaboratory variation was 96.2% for the MPS and 96.0% for the reference microdilution panels. The phase II studies used strains with known resistance mechanisms. The percent agreement with these strains was: Enterobacteriaceae, 94.5%; nonenteric gram-negative rods, 95.4%; staphylococci, 92.3%; and streptococci, 96.6%. The overall agreement within acceptable limits was 94.7% with these strains. When testing 359 clinical isolates, the frequency of strains within the acceptable range of agreement between the two methods was 97.3%. The MPS panels gave results in each of the three study phases equivalent to those obtained with the reference microdilution panels.

Anti-Bacterial Agents↗

PubMed1983

Quality control of moxalactam susceptibility disks.

In vitro evaluation of two types of moxalactam disks revealed significant performance differences when Staphylococcus aureus was being tested. The differences were traced to the amount of decarboxylated moxalactam present in the disks. The decarboxylated analog was much more active than the parent compound against S. aureus, not active against Pseudomonas aeruginosa, and approximately as active as the parent compound against Escherichia coli. A nine-laboratory coordinated study was performed to establish quality control parameters for 30-micrograms moxalactam disks. Problems with the establishment of interpretive standards for moxalactam disk tests were evaluated in the light of differences between disks utilized in earlier studies and those that are now commercially available. The type of disk greatly influences standards for tests with S. aureus but has insignificant influence on testing gram-negative bacilli.

Bacteria↗

PubMed1983

Comparison of the antibacterial spectra of cephalexin and cefaclor with those of cephalothin and newer cephalosporins: reevaluation of the class representative concept of susceptibility testing.

The validity of the class representative concept for in vitro susceptibility testing of older cephalosporins was reevaluated. Two oral cephalosporins, cephalexin and cefaclor, were compared with the established cephalosporin class representative, cephalothin, by using reference microdilution minimal inhibitory concentrations of 528 isolates of a wide variety of gram-positive and gram-negative bacterial pathogens. For each comparison, there were only 15 (2.8%) random major and very major interpretive discrepancies. Additional comparisons confirmed the need to test second-generation (cefamandole) and third-generation (cefotaxime) cephalosporins separately. These results provide reasonable assurance that the use of cephalothin as an in vitro predictor of qualitative bacterial susceptibility to these two oral cephalosporins remains an acceptable alternative to testing each antibiotic individually.

Bacteria↗