S Shivaprakasha, K Radhakrishnan, A Gireesh, P Shamsul Karim
e.coli, enterobacteriaciae, esbl
S Shivaprakasha, K Radhakrishnan, A Gireesh, P Shamsul Karim. Routine Screening For ESBL Production, A Necessity Of Today. The Internet Journal of Microbiology. 2006 Volume 3 Number 1.
The extended spectrum beta lactamase (ESBL) enzymes are plasmid-mediated enzymes capable of hydrolyzing and inactivating a wide variety of beta lactams, including third generation cephalosporins, penicillins and aztreonam.(1) Plasmids responsible for ESBL production carry resistance to many antibiotics like aminoglycosides, fluoroquinolones, tetracyclines, chloramphenicol and co-trimoxazole.(2,3) The ESBL producing organisms are reported in increasing numbers worldwide.(4,5,6,7) National Committee for Clinical Laboratory Standards (NCCLS), now called Clinical Laboratory Standards Institute (CLSI) recommends screening for ESBL production among
Materials and Methods
Between July 2004 to Dec 2004, a total of 1889 clinically significant Gram negative bacilli belonging to Enterobacteriaciae isolated from various clinical specimens were subjected to ESBL screening. The isolates were identified by standard techniques. Antimicrobial susceptibility testing was performed by Kirby-Bauer method and interpretation of results was as recommended by NCCLS.(8)
ESBL production was tested by using ceftazidime (30mcg) and ceftazidime plus clavulanic acid (30/10mcg) discs on Mueller-Hinton agar. Organism was considered as an ESBL producer if there was a ≥5mm increase in zone diameter around ceftazidime/clavulanic acid disc compared to zone around ceftazidime disc alone. ESBL production was tested in parallel with the antibiotic susceptibility testing on a separate Mueller Hinton agar plate. As per NCCLS guidelines, an isolate was reported as resistant to all penicillins, cephalosporins and aztreonam, if it was an ESBL producer.
The analysis was done by SPSS (Statistical Package for Social Sciences) version 11. Categorical variables were reported using frequencies and chi-square test was used to analyse the significance of different ESBL producers against the location in the hospital
The most frequent Enterobacteriaciae isolated was
Sensitivity to meropenem was 99.8% (n=1150/1152), piperacillin tazobactam 96.8% (n=1115/1152), cefoperazone sulbactam 93.3% (n=1075/1152), cotrimoxazole 21.7% (n=250/1152), ciprofloxacin 16.6% (n=191/1152), gentamicin 13.3% (153/1152), amikacin 53% (610/1152). Urinary isolates were tested against nitrofurantoin, norfloxacin, nalidixic acid. These showed susceptibility rate of 66.35% (n=355/535), 16.4% (n=88/535) and 12.3% (n=66/535) respectively [Table 4].
The frequency of ESBL producers of 60.98% in our study is comparable to previous Indian studies.(11,12,13) The most frequent isolates in our study were
Our study shows that there is a significant difference in the type of organism isolated from different locations of the hospital (
It is an established fact that, ESBL producers show cross resistance to other antibiotics also, thus limiting the therapeutic choice. We have noted this in our study as well. Sensitivity to meropenem was almost absolute (99.8%). Sensitivity to piperacillin tazobactam (96.8%) and cefoperazone sulbactam (93.3%) was also good. Whereas sensitivity to gentamicin, ciprofloxacin, co-trimoxazole, nalidixic acid and norfloxacin was poor and not suitable for empirical selection. Urinary isolates showed >50% susceptibility to amikacin and nitrofurantoin. These are the alternative cheaper antibiotics which can be considered for empirical therapy. The routine susceptibility testing by clinical laboratories fail to detect ESBL positive strains and shows false invitro sensitivity to cephalosporins.(16) Screening for ESBL production as a routine procedure in clinical laboratories gives valuable information to the clinician in appropriate selection of antibiotics. Hence, we conclude based on our study that, there is a high prevalence rate of ESBL producers among Enterobacteriaciae.
Dr.Shashikala.S.,M.D Asst. Professor, Department of Microbiology, Amrita Institute of Medical Sciences and Research Centre, Kochi, Kerala-PIN-682 026 India Tel : 04842801234, 04845008010 Fax : 04842802020 firstname.lastname@example.org