[Antimicrobial resistance of clinical isolates of Stenotrophomonas maltophilia].

OBJECTIVE: To investigate the antimicrobial resistance of clinical isolates of Stenotrophomonas matophilia (SMA) and the mechanisms of their drug resistance. METHODS: Disc diffusion method (NCCLS) was used to detect the resistant patterns of 88 initial SMA isolates resistant to 12 antibiotics isolated from a local hospital in the past 4 years. PCR was used to detect the 7 aminoglycosides modifying enzymes genes (AME) against amikacin and gentamicin. Metal-beta-lactamases (MBLs) were screened by synergic method, and extended-spectrum beta-lactamases (ESBLs) were detected by double-disk synergy test. RESULTS: The resistance rates of the SMA isolates were 0%-9.7% to minocycline, 12.5%-22.6% to ticarcillin-clavulanic acid, 12.5%-28.6% to levofloxacin, 18.8%-33.3% to doxycycline, 18.8%-40% to sulfamethoxazole compound, 50%-65.7% to ciprofloxacin, 50%-66.7% to cehazindme, 54.8%-66.7% to amikacin, 75%-100% to gentamicin, 81.3%-100% to piperacillin, 87.5%-100% to aztreonam and 93.5%-100% to imipenem. Aac(3)-I and ant(4')-II were not detected in these strains. The positive rates of the other 5 AME genes of aac(3)-II, ant(2'')-I, aac(6')-I, aac(3)-III, aac(3)-IV were 2.3%, 5.7%, 8%, 10%, and 10%, respectively. SMA strains producing ESBLs were found at the rate of 38.6%; 25% of the strains were MBL-producing, and 13.6% produced both ESBLs and MBLs. CONCLUSION: Most of the SMAs we isolated are multidrug-resistant through various mechanisms. The choice of antibiotics should be made according to the susceptibility results.

[Surveillance of antimicrobial resistance among nosocomial gram-negative pathogens from 15 teaching hospitals in China in 2005].

OBJECTIVE: To investigate the antimicrobial resistance among the nosocomial gram-negative pathogens from 15 teaching hospitals located in different areas in China in 2005. METHODS: A total of 1927 non-repetitive nosocomial gram-negative pathogens were collected from 15 teaching hospitals in different areas in China and sent to the central lab for reidentification and susceptibility testing. The levels of minimal inhibitory concentration (MIC) of 18 antimicrobial agents were determined by agar dilution method. WHONET 5.4 software was used to analyze the data. RESULTS: The strains of Escherichia coli, Klebsiella pneumoniae, and Proteous mirabilis isolates that did not produce extended spectrum beta lactamases (ESBLs) showed high sensitivity to beta-lactams. The antibiotics with a susceptibility rates over 80% against the strains of Entorobacter cloacae, Enterobacter aerogene, Citrobacter spp, Serratia spp, and Proteous vulgaris producing AmpC enzyme included meropenem, imipenem, and piperacillin-tazobactam, and these 3 drugs showed a susceptibility rate of more than 80% against the ESBL-producing strains of Escherichia coli and Klebsiella pneumoniae. Other antimicrobial agents showing a relatively high activity against Enterobacter spp, Citrobacter spp, Serratia spp and Proteous vulgaris included cefepime (67.3% - 100%), amikacin (67.3% - 95.2%), ceftazidime (52.9% - 100%) and cefoperazone-sulbactam (51.9% - 100%). The susceptibility rate of fluoroquinolones was 34.8% - 36.1% against non-ESBL-producing Escherichia coli and was 13.4% - 17.1% against ESBL-producing isolates. The most active agent against Pseudomonas aeruginosa was polymyxin B (95.6%). The agents with the activity rates of 70% - 80% included meropenem, imipenem, amikacin, and piperacillin-tazobactam. The antibiotic with a high susceptible rate against Acinetobacter baumannii was polymyxin B (98.3%), followed by imipenem (80.8%), meropenem (76.2%), and minocycline (67.4%). The susceptible rates of other agents were all below 60%. The agents with relatively high activity against Stenotrophomonas maltophilia included minocycline (85%), levofloxacin (82.5%), and trimethoprim-sulfamethoxazole (77.5%). The agents with a relatively high activity against Burkholderia cepacia included minocycline (77.2%) and meropenem (61.4%). CONCLUSION: Carbapenem, piperacillin-tazobactam, amikacin and cefepime remained relatively high activity against nosocomial Enterobacteriaceae, Non-fermenting pathogens have lower susceptibility to the antimicrobial agents than before.

[Genotype of TEM- and SHV-type beta-lactamase producing Klebsiella pneumoniae in Guangzhou area].

OBJECTIVE: To determine the prevalence and genotypes of TEM- and SHV-type beta-lactamase-producing Klebsiella pneumoniae in Guangzhou area. METHODS: Genotype determination of TEM- and SHV-type beta-lactamases were performed by PCR amplification followed by denaturing high-performance liquid chromatography (DHPLC) and DNA sequencing among 57 strain of klebsiella pneumonia obtained from the hospitals in Guangzhou. RESULTS: The genes bla(TEM) and bla(SHV) were amplified from all strains. TEM-116 type ESBLs were found in 56.14% (32/57) of the isolates. SHV-12 (n = 19), -11 (n = 11), -2a (n = 6), -28 (n = 4), -26 (n = 1), -33 (n = 1) and five novel SHV-type beta-lactamases were identified among the SHV-type beta-lactamases. These novel enzymes were designated from SHV-64, -65, -66, -67 and SHV-69, which derived from SHV-1 beta-lactamase or SHV-12 ESBL. A total of 94.74% of the isolates (54/57) produced both TEM- and SHV-type beta-lactamases simultaneously, in which 13.0% were TEM-116 and SHV-12 (n = 12). CONCLUSION: TEM-116 and SHV-12 are the predominant TEM- and SHV-type genotypes of Klebsiella pneumoniae producing beta-lactamases in Guangzhou. This area is confronted with the prevalence of the phenotypes of Klebsiella pneumoniae that simultaneously produce TEM- and SHV-type beta-lactamases.