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

New Stability Indicating RP-HPLC Method for the Estimation of Cefpirome Sulphate in Bulk and Pharmaceutical Dosage Forms

A simple stability indicating reversed-phase HPLC method was developed and subsequently validated for estimation of Cefpirome sulphate (CPS) present in pharmaceutical dosage forms. The proposed RP-HPLC method utilizes a LiChroCART-Lichrosphere100, C18 RP column (250 mm × 4mm × 5 μm) in an isocratic separation mode with mobile phase consisting of methanol and water in the proportion of 50:50 % (v/v), at a flow rate 1ml/min, and the effluent was monitored at 270 nm. The retention time of CPS was 2.733 min and its formulation was exposed to acidic, alkaline, photolytic, thermal and oxidative stress conditions, and the stressed samples were analyzed by the proposed method. The described method was linear over a range of 0.5-200μg/ml. The percentage recovery was 99.46. F-test and t-test at 95% confidence level were used to check the intermediate precision data obtained under different experimental setups; the calculated value was found to be less than the critical value.

Community-acquired Acinetobacter baumannii bacteremia in adult patients in Taiwan

We determined the clinical and microbiologic characteristics of community-acquired Acinetobacter baumannii bacteremia in 19 adult patients. We found that malignancy was the most frequent underlying disease. The overall mortality rate was 58%. All 14 available isolates were identified as genomic species 2 (A. baumannii) by 16S ribosomal DNA sequencing and were found to be genetically distinct by pulsed-field gel electrophoresis.

Evaluation of the in vitro activity of six broad-spectrum beta-lactam antimicrobial agents tested against over 2,000 clinical isolates from 22 medical centers in Japan. Japan Antimicrobial Resistance Study Group

Numerous broad-spectrum beta-lactam antimicrobial agents have been introduced into medical practice since 1985. Although several of these compounds have advanced, infectious disease therapy resistances to them has also emerged world-wide. In 1997, a Japanese 22 medical center investigation was initiated to assess the continued utility of these agents (oxacillin or piperacillin, ceftazidime, cefepime, cefpirome, cefoperazone/sulbactam [C/S], imipenem). The participating medical centers represented a wide geographic distribution, and a common protocol and reagents were applied. Three control strains and a set of challenge organisms were provided to participant centers. Etest (AB BIODISK, Solna, Sweden) strips were used in concurrent tests of these organisms and a qualitative determination of participant skills in the identification of resistant and susceptible phenotypes was established. The quantitative controls demonstrated 97.7-99.2% of MIC values within established QC limits, and the qualitative (susceptibility category) controls documented a 97.3% agreement of participant results with that of reference values (1,320 total results). Only 0.2% of values were false-susceptible errors. After the participant quality was assured, a total of 2,015 clinical strains were tested (10 strains from 10 different organism groups including methicillin-susceptible Staphylococcus aureus and coagulase-negative staphylococci [CoNS], Escherichia coli, Klebsiella spp., Citrobacter freundii, Enterobacter spp., indole-positive Proteae, Serratia spp., Acinetobacter spp., and Pseudomonas aeruginosa). The staphylococci were uniformly susceptible to all drugs tested except ceftazidime (MIC90, 24 micrograms/ml) that had a potency six- to 12-fold less than either cefepime or cefpirome. Only 3.7 and 45.1% of S. aureus and CoNS were susceptible to ceftazidime, respectively. Among E. coli and Klebsiella spp. the rank order of antimicrobial spectrum was imipenem = "fourth-generation" cephalosporins > ceftazidime > C/S > piperacillin. Possible extended spectrum beta-lactamase phenotypes were identified in 2.9-8.6% of these isolates. Isolates of C. freundii, Enterobacter spp., Proteae, and Serratia spp. that were resistant to ceftazidime and piperacillin remained susceptible to imipenem (0.0-4.5% resistance) and cefepime (0.0-5.0%). Acinetobacters were inhibited best by C/S (99.5% susceptible) and least susceptible to piperacillin (MIC90, > 256 micrograms/ml; 21.7% susceptible) activity. P. aeruginosa isolates were most susceptible to cefepime (83.6%) and this zwitterionic cephalosporin also had the lowest level of resistance (9.1% of MICs at > or = 32 micrograms/ml). Several multi-resistant organisms were identified in participant medical centers including S. marcescens strains resistant to cefepime, imipenem, or both observed in six hospitals. Clonal spread was documented in two medical centers; one hospital having two distinct epidemic clusters. Also a multi-resistant E. cloacae was found in two patients in the same hospital. Evaluations of carbapenem resistance in four species discovered only two strains (in same hospital) among 40 P. aeruginosa isolates (5.0%) with a metallo-enzyme, with nearly all of the remaining strains inhibited by an Ambler Class C enzyme inhibitor (BRL42715) indicating a hyperproduction of a chromosomal cephalosporinase. These results indicate that most newer beta-lactams remain widely useable in medical centers in Japan, but emerging often clonal, resistances have occurred. The overall rank order of antimicrobial spectrum against all ten tested bacterial groups favors the "fourth-generation" cephalosporin, cefepime (96.4% susceptible) as an equal to imipenem (95.9%) > C/S (90.9%) = cefpirome (90.0%) > ceftazidime (75.1%) = penicillins, either oxacillin or piperacillin (76.4%).

Bactericidal activity of cefpirome (HR 810) against 513 gram-negative bacteria isolated from blood of septicemic patients

The profile of antibacterial activity of cefpirome was compared with that of nine other antimicrobial agents against 513 gram-negative bacteria isolated from septicemic patients. All strains were evaluated for their sensitivity by disc diffusion and broth dilution tests (MIC and MBC). Cefpirome was compared to cefazolin, cefuroxime, ceftazidime, ceftriaxone, aztreonam, imipenem, ticarcillin, tobramycin and ciprofloxacin. Among the five cephalosporins tested in this study, cefpirome was the most active against all isolates. The MIC50 and MIC90 of eight isolates of Acinetobacter calcoaceticus were 2 and 4 mg/l and those of 89 Pseudomonas aeruginosa were 2 and 8 mg/l, respectively. The MIC90 values of cefpirome for all other groups of bacteria were < or = 1 mg/l. The activity of cefpirome against gram-negative bacteria is at least as good as that of aztreonam and imipenem. The only drug showing a better profile of activity than cefpirome is ciprofloxacin. The scattergram of the 513 isolates for cefpirome MICs and inhibitory zones with the 30 micrograms disc, showed that only eight isolates were not susceptible to cefpirome. These data suggest that the in vitro activity of cefpirome is comparable to if not better than that of other beta-lactams and tobramycin.

Effects of blood medium supplements on activities of newer cephalosporins tested against enterococci

This comparative study determined the effect of blood on the antienterococcal activities of the newer cephalosporins. Standardized disk diffusion susceptibility tests were performed with 57 strains of enterococci (30 Enterococcus faecalis strains) on Mueller-Hinton agar with and without 5% sheep blood supplementation. Twelve cephalosporins representing five different structural groups (based on the 7-alpha position substitution) were tested. The greatest frequency of activity enhancement by blood was observed with cefdaloxime and cefdinir (7-alpha hydroxyimino group) against E. faecalis. Cephalosporins with a 7-alpha methoxyimino group (cefpodoxime, cefepime, and cefpirome) had marked increases in zone diameters (3 to > 9 mm) when tested with the blood supplement. Cephems with 7-alpha amino or carboxy substitutions did not demonstrate any enhanced activity. Awareness of this phenomenon is important for the interpretation and accuracy of cephalosporin susceptibility testing.

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.

Microanalytical high-performance liquid chromatography assay for cefpirome (HR 810) in serum

We report a microanalytical high-performance liquid chromatography method for quantitation of cefpirome (HR 810) from serum. The drug was extracted from 0.05 ml of serum with 0.2 ml of isopropanol containing beta-hydroxypropyltheophylline, the internal standard. Separations were performed on a C18 column at ambient temperature with detection at 240 nm. The mobile phase consisted of acetate buffer (0.05 M sodium acetate) containing tetrabutylammonium hydroxide and methanol (pH 5.1; 70:30, vol/vol). The method was linear to 500 micrograms of cefpirome per ml and had a sensitivity of 0.6 micrograms/ml. Analytical recovery was greater than 86%, and the between-day coefficient of variation was less than 4.2%. The stability for 1 week at 4 to 8 degrees C and for 30 days at -20 degrees C was documented. Interference with commonly used antibiotics, analgesics, methylxanthines, and anticonvulsants was not found. The small sample volume and ease of preparation make this method suitable for use in pediatric pharmacokinetic investigations of cefpirome.

Interpretive criteria for the agar diffusion susceptibility test with ofloxacin

Regression analyses to determine the correlation of minimal inhibitory concentrations (MICs) and inhibition zones produced by ofloxacin discs were carried out with 300 freshly isolated cultures of infective organisms (20 strains from each of 15 species). After pilot studies, 5 micrograms loaded discs were chosen. Studies were performed simultaneously by using ICS/DIN and Kirby-Bauer/NCCLS methods on Mueller-Hinton agar. It was found that the correlation becomes poorer with increasing disc loads and when the Kirby-Bauer method is used. Based on preliminary MIC breakpoints of greater than or equal to 2 mg/L and greater than or equal to 8 mg/L and by calculations from regression equations, the following zone interpretations using the NCCLS method are recommended: resistant up to 12mm, intermediate 13 to 15mm, susceptible 16mm or more. The values for the DIN method are: resistant up to 13mm, intermediate 14 to 17mm, susceptible 18mm or more. No major errors were found in zone interpretations. Minor errors were observed in 0.7% when the NCCLS method was used, and in 1.3% with the DIN method.

Cefpirome (HR810) disk diffusion susceptibility tests: confirmation of interpretive criteria using cefotaxime and cefoperazone-resistant strains and effects of blood supplemented media

Cefpirome (formerly HR810) is a wide-spectrum, beta-lactamase-stable cephalosporin with antimicrobial activity against Pseudomonas species, Enterobacteriaceae, and gram-positive species. Reevaluation of the 30-microgram disk diffusion tests with commercially prepared disks using strains resistant to "third generation," cephalosporins confirms the proposed susceptibility breakpoint zone of greater than or equal to 18 mm (minimal inhibitory concentration correlate, less than or equal to 8.0 micrograms/ml) and the resistance breakpoint zone of less than or equal to 14 mm (minimal inhibitory concentration correlate, greater than or equal to 32 micrograms/ml). Major and minor interpretive errors were only 3.8%, and these errors could be further reduced (2.3%) by not testing methicillin-resistant Staphylococcus species. The addition of 5% sheep blood or chocolated blood to Mueller-Hinton agar slightly increased the cefpirome zone diameters (17.7-22.2 mm) for nearly 60% of Streptococcus faecalis strains tested.

Tentative disk diffusion susceptibility interpretive criteria for BMY-28142, a new cephalosporin

A total of 750 bacterial isolates, including 37 different species, were tested for susceptibility to BMY-28142 by standardized broth microdilution and disk diffusion tests. The zone diameter interpretive criteria tentatively suggested for the 30-micrograms BMY-28142 disk are as follows: susceptible = greater than or equal to 18 mm (MIC less than or equal to 8.0 micrograms/ml), resistant = less than or equal to 14 mm (MIC greater than or equal to 32 micrograms/ml), and indeterminate = 15 to 17 mm.

In vitro activity of cefpirome (HR810) against antibiotic-resistant gram-positive and gram-negative bacteria including organisms with inducible resistance

The activity of cefpirome (HR810) was compared with seven beta-lactam antibiotics against selected gram-positive and gram-negative bacteria. Cefpirome was the most active antibiotic tested against all groups of Enterobacteriaceae; 46% of the isolates of Pseudomonas aeruginosa were inhibited by less than or equal to 8 micrograms/ml of cefpirome. Fifty percent of the oxacillin-resistant Staphylococcus aureus isolates and 82% of the Streptococcus faecalis isolates were inhibited by less than or equal to 8 micrograms/ml of cefpirome. All Enterobacteriaceae and two of five P. aeruginosa isolates that were induced to produce beta-lactamase by prior exposure to cefoxitin remained susceptibile to cefpirome.

Comparative in vitro inhibitory and killing activity of cefpirome, ceftazidime, and cefotaxime against Pseudomonas aeruginosa, enterococci, Staphylococcus epidermidis, and methicillin-susceptible and -resistant and tolerant and nontolerant Staphylococcus aureus

With a macrotube dilution method, MICs and MBCs were determined for three aminothiazolyl cephalosporins, cefpirome (HR 810), ceftazidime, and cefotaxime, against Pseudomonas aeruginosa, enterococci, Staphylococcus epidermidis, and methicillin-resistant, -susceptible, and -tolerant strains of Staphylococcus aureus. Comparatively, cefpirome was the most active agent against all gram-positive cocci, including enterococci and methicillin-resistant S. aureus, and was as active as ceftazidime against P. aeruginosa. MBCs of cefpirome were within two dilutions of the MICs for 91% of P. aeruginosa and 90% of gram-positive cocci strains tested, except methicillin-resistant S. aureus, for which the MBCs were within three dilutions for 90% of strains.

Antimicrobial activity of HR810 against 419 strict anaerobic bacteria

HR810 and four other new beta-lactams were tested against 419 recent clinical anaerobic bacterial isolates. HR810 was found to have an antimicrobial spectrum most similar to that of cefotaxime, inhibiting 52.6% of Bacteroides fragilis group strains and 97.2% of all other anaerobic strains at an MIC of less than or equal to 16 micrograms/ml. Cefoxitin was found to have a narrower antimicrobial spectrum against the gram-positive anaerobic bacteria (8.4 to 10.1% less) than HR810 and cefotaxime, respectively.