[Extended-spectrum beta-lactamase in Klebsiella pneumoniae and Escherichia coli isolates].

OBJECTIVE

To investigate the prevalence, drug resistance, gene typing, and epidemicity of extended-spectrum beta-lactamases (ESBL) Klebsiella pneumoniae and Escherichia coli isolates.

METHODS

559 strains of K. pneumoniae and 427 strains of E.coli were isolated form Huanshan Hospital from 1 January to 31 December 1999. The ESBL-producing strains were detected by double disc test and confirmed by minimal inhibitory concentration (MIC). The MIC of ESBL-producing strains was detected by agar dilution test. The beta-lactamase genes were detected by PCR. DNA fingerprinting was made by pulsed-field gel electrophoresis (PFGE).

RESULTS

The incidence of ESBL-producing strains was 51% among the isolated K. pneumoniae (285/559) and 23.6% among the isolated E. coli (101/427), most of which were collected from the patients in the intensive care unit and neurosurgical ward. 63.5% of the ESBL-producing K. pneumoniae strains were collected from sputum specimens, and 64.3% of the ESBL-producing E. coli strains were collected from the urine specimens. Most ESBL-producing strains were resistant to most beta-lactam antibiotics, including the third-generation cephalosporins, and non- beta-lactam antimicrobial drugs, such as fluoroquinolones, aminoglycosides, tetracycline, and chloramphenicol. Most of the ESBL-producing strains were susceptible to imipenam, cefmetazole, and beta-lactam antibiotic/clavulanic acid. TEM type beta-lactamase was the main type among those EBSL-producing strains, followed by SHV type and CTX-M type. Some ESBL-producing E. coli and most ESBL-producing K. pneumoniae produced more than one type of beta-lactamase.

CONCLUSION

ESBL-producing strains are common among hospital strains of E. coli and K. pneumoniae. Most of them are multidrug resistant. Prevalence and transmission of these strains exist in hospital.