Epidemiological and antibiotic resistant study on extended-spectrum β-lactamase-producing Escherichia coli and Klebsiella pneumoniae in Zhejiang Province

Objective To investigate the epidemiological status of extended-spectrum β-lactamase (ESBL) producing Escherichia coli (E.coli) and Klebsiella pneumoniae (K.pneumoniae) and the drug resistance profiles of such organisms .Methods A total of 282 clinical isolates of E .coli and 180 of K .pneumoniae were collected from different districts of Zhejiang Province .Inhibitor potentiated broth dilution tests were performed for detecting extended-spectrum β-lactamases .Etests were performed to detect the drug resistance of these strains against nine commonly used antibiotics Results The prevalence of extended-spectrum β-lactamases in E .coli and K .pneumoniae was 34.0% and 38.3%, respectively .The average prevalence of extended-spectrum β-lactamases in E .coli and K .pneumoniae was 35.7% .The resistance prevalence of extended spectrum β-lactamase producing strains to ceftazidime and cefotaxime was 40% and 26% respectively, so were those to cefepime, cefoxitin, piperacillin-tazobactam, cefoperazone-sulbactam, amikacin and ciprofloxacin .All these strains were sensitive to imipenem .Conclusion The results in this study showed that the prevalence of extended-spectrum β-lactamases was high, while extended-spectrum β-lactamase producing strains were resistant to most antimicrobial agents except imipenem .     

Prevalence of extended-spectrum β-lactamases in isolates of the Enterobacter cloacae complex from German hospitals

In 2002, 119 isolates of the Enterobacter cloacae complex were collected randomly from 11 German laboratories nationwide. Antibiotic susceptibilities were tested by disk-diffusion tests according to CLSI guidelines, and MICs were determined using Etests. PCRs were performed to amplify all TEM and SHV, and most CTX-M and OXA beta-lactamase genes. PCR products were sequenced to identify the precise extended spectrum beta-lactamase (ESBL) types. Isoelectric focusing (IEF) and PM/PML Etests were used to confirm production of the respective ESBLs. According to susceptibility tests and CLSI criteria, 49 (40%) isolates were resistant to extended-spectrum cephalosporins. Seven (5.8%) isolates were positive in at least one of the PCR assays. Sequencing identified production of TEM-1 beta-lactamase genes by three (2.9%) isolates, and ESBL genes of the CTX-M and SHV beta-lactamase families by five (4.2%) isolates. IEF confirmed the production of beta-lactamases in the expected pI ranges of the respective ESBLs, and four of the five ESBL-producers were detected using the PM/PML Etest. All ESBL-producing isolates showed co-resistance to sulphonamides.     

Occurrence of qnrA-positive clinical isolates in French teaching hospitals during 2002–2005

Bacteria harbouring the novel qnrA plasmid-mediated mechanism of quinolone resistance have been described in different countries, but the frequency of their occurrence has not been investigated. In total, 1,468 clinical isolates of Enterobacteriaceae with quinolone resistance or extended-spectrum beta-lactamase (ESBL) phenotypes were collected from eight teaching hospitals in France during 2002-2005 and screened for qnrA. Overall, 28 isolates (22 Enterobacter cloacae, three Klebsiella pneumoniae, one Citrobacter freundii, one Klebsiella oxytoca and one Proteus mirabilis) were positive for qnrA, representing 1.9% of all isolates, 3.3% of ESBL-producing isolates (22% of the E. cloacae isolates) and 0% of non-ESBL-producing isolates. The prevalence of qnrA among consecutive ESBL-producing isolates in 2004 from the eight hospitals was 2.8% (18/639). Of the qnrA-positive isolates, 100% were intermediately-resistant or resistant to nalidixic acid, and 75% to ciprofloxacin. Twenty-one of the 22 qnrA-positive E. cloacae isolates were obtained from two hospitals in the Paris area, and molecular typing and plasmid content analysis showed clonal relationships for five, three and two isolates, respectively. The qnrA genetic environment was similar to that of the In36 integron. The remaining two isolates had qnrA variants (30 and 29 nucleotide differences, respectively, compared with the original sequence) and an unknown genetic environment. The ESBL gene associated with qnrA was bla(SHV-12) in most of the isolates, but bla(PER-1) and bla(SHV-2a) were found in two isolates. In France, it appears that qnrA-positive isolates are predominantly E. cloacae isolates producing SHV-12, and may be associated with the dissemination of an In36-like integron.     

Bactericidal activity of three β-lactams alone or in combination with a β-lactamase inhibitor and two aminoglycosides against Klebsiella pneumoniae harboring extended-spectrum β-lactamases

Objective: To study the bactericidal activity of β-lactam antibiotics (imipenem, cefepime, cefpirome) alone or in combination with a β-lactamase inhibitor (sulbactam) in the presence or absence of aminoglycoside (amikacin or isepamicin) against Klebsiella pneumoniae strains producing extended-spectrum β-lactamases (ESBLs).
Methods: We characterized 10 strains by means of analytic isoelectric focusing and pulsed-field gel electrophoresis. The ESBLs produced by these strains were derived from either TEM (TEM-1, TEM-2) or SHV-1. The killing-curve method was used for this bacterial investigation. Bacteria (final inoculum 5×10 ⁵ CFU/mL) were incubated with antibiotics at clinical concentrations obtained in vivo.
Results: All the combinations with cefepime or cefpirome + sulbactam were bactericidal, with a 4 log₁₀ decrease being obtained within 6 h without regrowth at 24 h, whereas imipenem alone, and combinations, gave a bactericidal effect within 6 h. The two cephalosporins alone decreased the inoculum of 4 log₁₀ at 6 h but regrowth was observed at 24 h. When the aminoglycoside was added, this bactericidal effect was obtained within 3 h with amikacin and within 1 h with isepamicin.
Conclusions: Cefepime + sulbactam or cefpirome + sulbactarn may be an alternative to imipenem for the treatment of patients with ESBL-producing K. pneumoniae. Aminoglycosides are often associated in nosocomial infections due to ESBL-producing K. pneumoniae: isepamicin acted faster than amikacin, but both worked well. To conclude, it may be prudent to avoid extended-spectrum cephalosporins as single agent when treating serious infections due to ESBL-producing K. pneumoniae. Addition of a β-lactamase inhibitor such as sulbactam ± aminoglycoside is advisable to avoid failure of treatment.     

产超广谱β-内酰胺酶大肠埃希菌和肺炎克雷伯菌的检测及耐药性

目的了解大肠埃希茵和肺炎克雷伯菌产超广谱β-内酰胺酶（ESBLs）的耐药性,为临床合理使用抗茵药物提供依据。方法细菌的鉴定及药敏采用Microscan WalkAway 40SI全自动系统。产ESBLs菌株药敏试验用琼脂纸片扩散法,根据2005年美国临床实验室标准化委员会（NCCLS）标准判断结果。结果检出产ESBLs细菌46株,检出率25．7％,其中产ESBLs大肠埃希菌33株,检出率26．7％,产ESBLs肺炎克雷伯菌13株,检出率32．5％;产ESBLs菌株对碳青霉烯类（亚胺培南）、头孢西丁及β-内酰胺酶抑制剂复合物、阿米卡星耐药性较低为0％～28．7％,对其余抗菌药物都产生较高的耐药性。结论重视产ESBLs细菌检测,根据药敏试验结果合理用药,碳青霉烯类、头孢西丁及β-内酰胺酶抑制剂复合物、阿米卡星是目前治疗产ESBLs细菌有效抗菌药物。     

Multidrug-resistant Enterobacteriaceae including metallo-β-lactamase producers are predominant pathogens of healthcare-associated infections in an Indian teaching hospital

Purpose: A study was carried out in an Indian teaching hospital in 2009 to detect the rate of surgical site infections (SSI) and peripheral vascular access site infections. Materials and Methods: The study was a point-prevalence study involving over 300 patients. The presence of infection was determined according to the CDC criteria. Swabs were taken from the infected sites and identification and sensitivity were carried out using VITEK® 2 automated system. Characterisation of β-lactamase was carried out at ARRML, Colindale, London. Results: The rate of SSI was 15% for the clean and clean-contaminated categories while that for the dirty contaminated category was 85% (NNIS risk index 0). Cultures yielded definite or probable pathogens from 64% (9/14) of the patients with SSI. In 1/3^rd of the cultures, Staphylococcus aureus was grown and the rest had Enterobacteriaceae, either extended-spectrum β-lactamase (ESBL) producers or Amp-C hyperproducers and, alarmingly, three isolates were positive for newly recognised New Delhi metallo-β-lactamase-1 (NDM-1). In medicine, 87% (n = 99) of the patients had a peripheral IV access device, 55% developed associated phlebitis/infection and, in seven, probable pathogens were isolated (Candida species and Escherichia coli producing ESBL and NDM-1, respectively, Staphylococcus aureus and Enterococcus faecium). All ESBL and metallo-β-lactamase producers were resistant to multiple classes of antimicrobials, the latter being sensitive only to colistin and tigecycline. The study also found that all post-operative patients were on antibiotics, 92% on IV [213 defined daily doses (DDD)/100 post-op patients] limited mainly to the third-generation cephalosporins (26%) and aminoglycosides (24%) and imidazole derivatives (30%). In medicine, 83% (n = 82) were on IV antibiotics (123 DDD/100 bed-days), limited mainly to the third-generation cephalosporins (74%). Conclusion: Indiscriminate use of antibiotics is a major problem predisposing patients to harm by multi-resistant pathogens. Carbapenems were in little use in this hospital, but the selection pressure exerted by cephalosporins and other unrelated classes was sufficient to select NDM-1-producing strains due to co-selection, suggesting a role of single plasmid carrying resistance genes to multiple classes.