| BackgroundSoon after introducing the clinical use of extended-spectrum cephalosporins, such as cefetaxime, ceftriaxone, aztreonam and ceftazidime, extended-spectrum ?- lactamases (ESBLs) were firstly isolated from Enterobacteriaceae in Europe. Then, reports on ESBLs spread around the world. ESBLs were produced by Gram-negative bacteria, such as Klebsiella pneumoniae, Escherichia coli, Proteus mirabilis, Serratia marcescens, Enterobacter cloacae, Acinetobacter sp. and Pseudomonas aeniginosa, and could inactivate oxyimino- ?-lactams like third-generation cephalosporins and aztreonam, due to their wider substrates for hydrolysis than penicillinase like TEM-1, TEM-2 and SHV-1, were designated. The resistance of ESBLs-producing Enterobacteriaceae has currently become one of the most important nosocomial resistance problems around the world, and their detecting is harder in the laboratory, and due to diverse genotypes, exist distinction of resistance and detecting substrates between them. Therefore, we had a study of the best detective substrates and drug-resistance of ESBLs-producing K. pneumoniae and K coli isolates in Hefei, Anhui Province so that we could prevent regional prevalence of ESBLs producers and guide clinical therapy in order to avoid delaying therapy and wasting drugs.Without large investigation about the prevalence of ESBLs producers in our country, on the other hand, we studied ESBLs epidemiology, detecting, resistance and resistant genotypes of 299 K. pneumoniae and E. coli strains isolated from Hefei, Anhui Province China between 1999 and 2000. ObjectiveTo study the best detective substrate of ESBLs-producing K. pneumoniae and E. coli isolates in Hefei, Anhui Province between September, 1999 and September, 2000.-4-To investigate the epidemiological data and drug-resistance of ESBLs producers in Hefei, Anhui Province between September, 1999 and September, 2000.To study resistant genotypes of ESBLs producers isolated from Hefei, Anhui Province between 1999 and 2000. Materials and Methods299 clinical isolates of K. pnenmoniae and E.coli were collected from different hospitals in Hefei. The isolates were identified using Microscan Walkaway-40 system (from DADE BEHRING USA). ESBLs producers were screened by ESBLs initial screening test and phenotype affirmative test in accordance with the guidelines of the National Committee for Clinical Laboratory Standards in 1999, respectively. Their resistances to 20 antimicrobial agents were also performed by miniaturization of the broth dilution susceptibility test of this system in accordance with manufacturers' criteria, but to cefoperazone/sulbactam by Kirby-Bauer test.Four pairs of primers were designed in accordance with the basic sequences of TEM-1D, SHV-1, CTX-M-1 and OXA-1 in the GenBank, respectively. Polymerase chain reaction was performed with the four pairs primers respectively and ESBLs producers, which were determined by ESBLs phenotype affirmative test, were acted as templates. ResultsCefetaxime was the best detective substrates of ESBLs-producing K. pneimtoniae and E. coli isolates, and then ceftriaxone and aztreonam in Hefei. Relying on ceftazidime resistance as a single marker for presence of ESBLs may be unreliable.The incidences of ESBLs in K. pnenmoniae and E.coU were 50.5 percent and 24.3 percent respectively. The average incidence was 32.8 percent. Compared with the resistance rates of non-ESBLs producing strains, those of ESBLs producers to ceftazidime, aztreonam, cefepime, cefoxitin, piperacillin/tazobactam, cefoperazone/ sulbactam, amikacin and ciprofloxacin increased. But all ESBLs producers were susceptible to imipenem.Of 98 ESBLs-producers, there were 79 TEM-type $ -lactamases producers, 27 SHV-type producers, 16 CTX-M-type producers, 2 OXA-type producers, andnon-TEM-SHV-CTX-M-OXA-type producers .ConclusionsOur results showed that cefetaxime was the best detective substrate of ESBLs-producing K. pneumoniae and E. coli isolates, and then ceftriaxone and aztreonam, and relying...
|
PDF Full Text Request