Antimicrobial susceptibility of Klebsiella pneumoniae producing extended-spectrum ß-lactamase (ESBL) isolated in hospitals in Brazil

The prevalence of Klebsiella pneumoniae producing extended-spectrum ß-lactamase (ESBL) has been increasing all over the world. Infections caused by ESBL producing isolates are difficult to detect with current susceptibility test, and are difficult to treat. ESBLs confer resistence to all currently available ß-lactam, except carbapenems. In addition, ESBL, production is usually associated with resistence to other classes of antimicrobial agents such as aminoglycosides and quinolones. The objective of this study was to evaluate in vitro susceptibility patterns of ESBL producing K. pneumoniae isolated in Brazil. Seventy-two strains were tested using E test against 30 antimicrobial agents, inclusing carbapenems, second and third generation cephalosporins, aminoglycosides, quinolones, and some new compounds. The most active compounds (i.e. 100 percent susceptibility) were meropenem (MIC90,0.125µg/mL), imipenem (MIC90,0.25µg/mL), and cefotetan (MIC90,2µg/mL). Ciprofloxacin (MIC90, 1µg/mL, 94 percent susceptibility) and cefepime (MIC90, 6µg/mL, 92 percent susceptibility), were also very active against our collection of ESBL producing K. pneumoniae. None of the six aminoglycosides showed good activity against these strains (16 percent to 41 percent susceptibility) and only 39 percent of the isolates were susceptible to piperacillin/tazobactam. The results of our study indicated that the carbapenems are most active compounds against ESBL producing K.pneumoniae in Brazil, and ciprofloxaxin remains very active against these strains. Cefotetan and cefepine were also very active against ESBL producing K.pneumoniae in Brazil; however, further studies are necessary to evaluate the role of these cephalosporins in the treatment of infections due to ESBL producing strains.

Chemical stability of cefotetan disodium in 5% dextrose and 0.9% sodium chloride injections.

The chemical stability of cefotetan disodium in 5% dextrose and 0.9% sodium chloride injections has been studied using a stability-indicating high-pressure liquid chromatographic (HPLC) assay method. The drug appears to be relatively unstable at 25 degrees C (expiry time 2 days), compared with at least 41 days at 5 degrees C and at least 60 days at -10 degrees C. Thawing the frozen samples in a microwave (90 s) did not cause any significant decomposition. The manufacturer's recommended expiry time of 4 days at 5 degrees C and at least 7 days at -10 degrees C is very conservative. The HPLC method developed is accurate and precise with a relative percentage standard deviation of 1.7 based on six readings. The method appears to be stability-indicating as the samples decomposed under drastic conditions had almost no drug left and new peaks were observed in the chromatograms.