Extended Spectrum Beta-Lactamases (ESBL) in gram negative bacill at a Tertiary Care Hospital

K. L. Shobha, L. Ramachandra, G. Rao, S. Majumder, S. P. Rao

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Extended spectrum beta lactamases (ESBL) hydrolyse expanded spectrum cephalosporins like ceftazidime and cephotaxime ,which are used in the treatment of Pseudomonas and other gram negative bacteria. ESBL producing bacteria may not be detectable by the routine disk diffusion susceptibility test, which leads to inappropriate use of antibiotics and treatment failure. Not much information on ESBL producing organisms causing infection is available from the south west coastal region. An effort was therefore made to study the ESBL producing gram negative organisms by the phenotypic confirmatory test and the novel fashion method. Antibiotic susceptibility pattern of ESBL organisms were also analysed. Methods: 160 clinical strains were included in the study. Strains were obtained from adult patients who were either admitted to or attended the outpatient departments of medicine, surgery, obstetrics and gynaecology in a tertiary care hospital. The study was conducted from June 2005 to December 2005. Informed consent was taken from the patients for collecting the samples. The samples were processed for the identification of organisms and were screened for ESBLs. The isolates were also tested for antimicrobial susceptibility by the Kirby-Bauer disc diffusion technique, using Muller Hinton agar. Screening for ESBL was done as per the guidelines recommended by CLSI. Organisms were further tested for confirmation of ESBL production by the phenotypic confirmatory test and by the Novel fashion. Results And Conclusion: Out of the total 160 strains, the common organisms isolated were Klebsiella pneumoniae with 73 strains (45.62%), followed by Escherichia coli with 63 strains (39.37%) and Pseudomonas spp with 14 strains (8.75%), respectively. ESBL positive strains detected by the screening test for Klebsiella pneumoniae were 20(27.39%), for Escherichia coli were 16 (25.39%) and for Pseudomonas species were 03(21.42%), respectively. ESBL positive organisms were also found to remain positive by the Phenotypic confirmatory test, when combinations of Cefotaxime against amoxicillin/clavulanic acid and Cefipime against piperacillin/tazobactum were used. The novel fashion method showed that ESBL and de-repressed mutants in E.coli were 29(46.03%), only de-repressed mutants strains were 15 (23.80%) and inducible Amp C gene producers were 03(4.76%). Among 48(65.75%) strains, Klebsiella pneumoniae showed ESBL and de-repressed mutants, de-repressed mutants alone in 08(10.95%) strains and inducible Amp C mutants in 02(2.73%). The antimicrobial susceptibility test showed that ESBL organisms were resistant to gentamicin and trimethoprim/ sulphamethoxazole, but all were susceptible to imipenem, We conclude that clinical laboratories should develop quick screening methods to assess the different mechanisms of ESBL production, so that the patients can be treated with appropriate antibiotics.

Original languageEnglish
Pages (from-to)1307-1312
Number of pages6
JournalJournal of Clinical and Diagnostic Research
Issue number1
Publication statusPublished - 05-03-2009

All Science Journal Classification (ASJC) codes

  • Clinical Biochemistry


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