The susceptibility of 453 clinical bacterial isolates was determined by broth microdilution and disk diffusion methods to cefotaxime (CTX), desacetylcefotaxime (dCTX), and various combinations of CTX plus dCTX. With a 1:1 ratio of CTX/dCTX, 97% of the minimal inhibitory concentrations were within one doubling dilution of those for CTX alone. With the disk diffusion test, the 30/30 micrograms disk of CTX/dCTX produced zone diameters very similar to those of the 30 micrograms CTX disk, averaging 0.4 mm larger than the latter. Regression analysis demonstrated that the 30 micrograms CTX disk was equally predictive for CTX and a 1:1 ratio of CTX/dCTX.

Bacteria↗

PubMedDate not supplied

Statistical criteria for selecting quality control limits for broth microdilution susceptibility tests with 39 different antimicrobial agents. Collaborative Antimicrobial Susceptibility Testing Group.

Multilaboratory studies have been carried out to establish quality control limits for broth microdilution susceptibility tests with 39 different antimicrobial agents and four different control strains. For each drug-microorganism combination, 100 MIC values were recorded (20 from each of five laboratories). An acceptable range of MICs was defined as values that included greater than 95% of those 100 MICs. In a series of consecutive tests, less than or equal to 5% of the MIC values might be expected to be one doubling dilution interval above or below the limits defined in that way: at least 95% of those MIC determinations should be within the narrow control limits. The 39 antimicrobial agents provided 111 drug-microorganism combinations for which usable quality control limits could be defined. The greater than 95% rule yielded a narrow range (including only two dilution steps) with 58 of the 111 control limits, and 53 control limits permitted a more traditional three-dilution step range of MICs.

Anti-Bacterial Agents↗

PubMedDate not supplied

Interpretive criteria, quality control guidelines, and drug stability studies for susceptibility testing of cefotaxime, cefoxitin, ceftazidime, and cefuroxime against Neisseria gonorrhoeae.

Cefotaxime, cefoxitin, ceftazidime, and cefuroxime were tested in a multicenter study to establish susceptibility testing criteria and quality control guidelines for Neisseria gonorrhoeae. Interpretive criteria were established by using triplicate testing of at least 100 gonococcal strains having various susceptibility patterns to currently utilized drug regimens. Only a susceptible category was proposed for cefotaxime and ceftazidime (greater than or equal to 31 mm and less than or equal to 0.5 micrograms/ml) because of rare resistant isolates. The other interpretive crtieria were cefoxitin susceptible, greater than or equal to 28 mm (less than or equal to 2 micrograms/ml); intermediate, 24-27 mm (4 micrograms/ml), and resistant, less than or equal to 23 mm (greater than or equal to 8 micrograms/ml); cefuroxime-susceptible, greater than or equal to 31 mm (less than or equal to 1 micrograms/ml); moderately susceptible, 26-30 mm (2 micrograms/ml); and resistant, less than or equal to 25 mm (greater than or equal to 4 micrograms/ml). Quality control criteria were established by using multiple agar lots, three disk lots, and a number of replicates consistent with National Committee for Clinical Laboratory Standards M23-T guidelines.

Cefotaxime↗

PubMedDate not supplied

Antimicrobial activity of cefpirome. An update compared to five third-generation cephalosporins against nearly 6000 recent clinical isolates from five medical centers.

Cefpirome, cefotaxime, ceftazidime, cefoperazone, ceftizoxime, and ceftriaxone were tested against approximately 6000 fresh clinical isolates from five medical centers. For 3031 strains of Enterobacteriaceae tested, cefpirome consistently had the lowest MIC50s and lowest percentage of resistant strains. Cefpirome was also the most active agent against the 2138 Gram-positive cocci tested; Staphylococcus haemolyticus was uniformly resistant to all agents tested. Against 791 nonenteric Gram-negative bacilli, the activity of cefpirome was most comparable to that of cefoperazone and slightly less active than ceftazidime. Among the current third-generation cephalosporins, cefotaxime and cefoperazone emerged as having better overall balanced activity. Ceftazidime displayed poorest coverage against Enterobacteriaceae and Gram-positive organisms. Ceftizoxime also provided compromised coverage of staphylococci and nonenteric Gram-negative bacilli. Cefpirome remains as active as originally described in 1984 and possesses a slightly wider spectrum of activity against contemporary aerobic pathogens compared to currently marketed third-generation cephalosporins.

Bacteria↗

PubMedDate not supplied

In vitro activity of ampicillin, amoxicillin, ampicillin-sulbactam, and amoxicillin-clavulanic acid against consecutive clinical isolates of Enterobacteriaceae.

Ampicillin was generally twice as active as amoxicillin against 2440 consecutive isolates of Enterobacteriaceae from five medical centers. When beta-lactamase inhibitors were added to the penicillins, there was a significant increase in susceptibility. The magnitude of the increased susceptibility to ampicillin-sulbactam (A-S) and amoxicillin-clavulanic (A-C) acid varied with the species and types of beta-lactamases elaborated. Although cross-susceptibility and cross-resistance between ampicillin and amoxicillin was nearly complete, major differences were documented between A-S and A-C with 6.7% of our consecutive isolates of Enterobacteriaceae. The clinical significance of these findings remains uncertain, but they may help explain some of the discrepancies occasionally observed by clinical microbiologists with the combination drugs.

Amoxicillin↗

PubMedDate not supplied

Multilaboratory evaluation of the in vitro activity of 13 beta-lactam antibiotics against 1474 clinical isolates of aerobic and anaerobic bacteria.

The in vitro activity of 13 beta-lactam antibiotics against 1474 recent clinical isolates was evaluated in a multilaboratory study. The most active antibiotic tested in this study was imipenem (98.5% of the strains were susceptible), followed by ticarcillin-clavulanate (91.4%), cefoperazone (90.0%), ceftazidime (87.9%), cefotaxime (87.7%), ceftriaxone (87.0%), ceftizoxime (86.3%), cefotetan (78.5%), ampicillin-sulbactam (77.9%), cefoxitin (73.5%), cefuroxime (70.9%), cefonicid (64.5%), and cefazolin (57.9%).

Anti-Bacterial Agents↗

PubMedDate not supplied

RP 59500, a new streptogramin highly active against recent isolates of North American staphylococci.

To assess the potential clinical utility of RP 59500, 10 investigators from separate locations in the United States and Canada each tested approximately 200 current isolates of staphylococci (Staphylococcus aureus and coagulase-negative staphylococci) by a standard protocol. RP 59500 was highly active (MIC90 < or = 2 micrograms/ml) against all strains, including those that were resistant to oxacillin, ciprofloxacin, erythromycin, and spiramycin.

Coagulase↗

PubMedDate not supplied

Cefditoren in vitro activity and spectrum: a review of international studies using reference methods.

Cefditoren, a broad-spectrum orally administered cephalosporin ester, has documented in vitro efficacy against many Gram-positive and -negative pathogens and stability against clinically important beta-lactamases. We have reviewed the microbiology and the pharmacokinetic/pharmacodynamic literature regarding the spectrum and potency of this newer agent against the major etiologic agents of community-acquired respiratory infection, (Streptococcus pneumoniae, Hemophilus influenzae and Moraxella catarrhalis), as well as the Enterobacteriaceae and non-enteric Gram-negative bacilli, staphylococci, and other aerobic and anaerobic Gram-positive cocci. The level of cefditoren activity against S. pneumoniae (MIC(90,) 0.5 microg/mL) was superior to all marketed oral cephalosporins and at least equal to amoxicillin +/- clavulanate. H. influenzae (MIC(90,) 0.016-0.03 microg/mL) and M. catarrhalis (MIC(90,) 0.06-0.5 microg/mL) were also very susceptible to cefditoren. In contrast to cefixime and ceftibuten, cefditoren was active against oxacillin-susceptible staphylococci (MIC(90,) < or = 1 microg/mL) at a level comparable to cefuroxime axetil, cefaclor or cefprozil. Enterococci, Pseudomonas aeruginosa and most anaerobes (Gram-negative) were not cefditoren-susceptible, but most Enterobacteriaceae, beta-haemolytic and viridans group streptococci were highly susceptible. Furthermore, an overview of key in vitro susceptibility testing methods and issues including disk diffusion testing and Etest (AB BIODISK, Solna, Sweden) method accuracy, interpretive criteria, and pharmacodynamic considerations for the selection of a breakpoint concentration are provided. The rapid bactericidal nature of the antibacterial activity of cefditoren, its post antibiotic effect, penicillin binding protein targets, and extent of beta-lactamase stability are all favorable qualities. In conclusion, this orally administered (BID) beta-lactam possesses promise for use against commonly isolated problematic respiratory tract pathogens such as penicillin-non-susceptible pneumococci and beta-lactamase-positive M. catarrhalis or H. influenzae. Success in the clinical trials will further define the role of cefditoren in this era of emerging resistant bacterial pathogens.

Cephalosporins↗

PubMedDate not supplied

Dilemmas of the beta-lactam explosion.

Explore the source record for details and available documents.

Bacterial Infections↗

PubMedDate not supplied

Multilaboratory evaluation of an agar diffusion disk susceptibility test for rapidly growing anaerobic bacteria.

A multilaboratory collaborative study was undertaken to determine whether the anaerobic disk diffusion test of Horn et al. could be performed reproducibly and accurately. Tests with nine different antimicrobial disks were evaluated. Reproducibility of the agar diffusion disk method was similar to that of the reference agar dilution test procedure. The anaerobic disk diffusion procedure was found to be a potentially useful method for testing some antimicrobial agents against rapidly growing anaerobes belonging to the Bacteroides fragilis group. These promising results warrant further investigations and validations.

Bacteria, Anaerobic↗

PubMedDate not supplied

Antimicrobial susceptibility tests with cefotaxime and correlation with clinical bacteriologic response.

Cefotaxime is a new cephalosporin with a wide spectrum of antimicrobial activity. For broth and agar dilution tests, the MIC breakpoints suggested for defining bacterial susceptibility are less than or equal to 8 microgram/ml for susceptible, 16-32 microgram/ml for moderately susceptible (indeterminate), and greater than 32 microgram/ml for resistant. For disk diffusion tests, the zone diameter breakpoints suggested are greater than or equal to 23 mm for susceptible, 15-22 mm for moderately susceptible, and less than or equal to 14 mm for resistant. Examination of the bacteriologic outcome of infection for 1,440 patients treated with cefotaxime shows that the results of disk diffusion tests correlated well with clinical response. The organisms that had cefotaxime disk zones of greater than or equal to 23 mm were eradicated in 89% of cases. Clinical response of urinary tract infections due to Pseudomonas aeruginosa was unrelated to disk results for bacterial isolates; the rate of bacteriologic cure was 55%-64% regardless of category. It is further recommended that cefotaxime and other cephalosporins not be tested against the enterococci.

Acinetobacter↗

PubMedDate not supplied

Piperacillin/tazobactam (YTR 830) combination. Comparative antimicrobial activity against 5889 recent aerobic clinical isolates and 60 Bacteroides fragilis group strains.

Piperacillin combined with tazobactam (formerly YTR 830) was tested at a ratio of 8:1 against 5889 aerobic isolates and 50 strains from the Bacteroides fragilis group. Imipenem was the most active agent tested against Enterobacteriaceae (99.3% at less than or equal to 4 micrograms/ml), ceftazidime was most effective against nonenteric Gram-negative bacilli (80.7% at less than or equal to 8 micrograms/ml), and piperacillin/tazobactam possessed a superior spectrum against Gram-positive cocci (92.2% at less than or equal to 16/2 micrograms/ml). Against all aerobic strains, piperacillin/tazobactam had a spectrum (90.3% at less than or equal to 16/2 micrograms/ml) comparable to imipenem (93.6% at less than or equal to 4 micrograms/ml) and was distinctly greater than that of ticarcillin/clavulanic acid (73.3% at less than or equal to 16/2 micrograms/ml) and ceftazidime (75.5% at less than or equal to 8 micrograms/ml). Against the B. fragilis group isolates, all piperacillin/tazobactam MICs were less than or equal to 64/8 micrograms/ml. This activity was superior to piperacillin alone (MIC:50, 8-64 micrograms/ml) and cefoxitin (MIC50, 4-64 micrograms/ml). Piperacillin/tazobactam appears to be a promising parenteral antimicrobial combination, with a spectrum effective against a wide variety of clinical pathogens.

Bacteria, Aerobic↗

PubMedDate not supplied

Ticarcillin: a collaborative in vitro comparison with carbenicillin against over 9,000 clinical bacterial isolates.

The minimal inhibitory concentrations of ticarcillin and carbenicillin were determined for 9,236 clinical bacterial isolates by the broth microdilution method at four participating laboratories. Ticarcillin showed significantly increased activity against Klebsiella pneumoniae (P less than .001), Pseudomonas aeruginosa (P less than .001) and Aeromonas hydrophilia (P less than .005) when compared to carbenicillin, but no signifcant differences were observed against other gram-negative organisms. Ticarcillin was consistently less active against the gram-positive cocci, and these differences were significant for Staphylococcus aureus (P less than .001), Streptococcus agalactiae (P less than .001), Staphylococcus epidermidis (P less than .001) and Streptococcus viridans (P less than .005). Significant regional and institutional differences in susceptibility to the two drugs were observed for several species, including common nosocomial pathogens such as S. aureus, P. aeruginosa, K. pneumoniae and Escherichia coli.

Bacillus↗