ABSTRACT
Objectives: Extended spectrum beta lactamase (ESBL) producers have posed a great threat to the use of many classes of antibiotics, particularly cephalosporins. Their detection has proved to be difficult for many laboratories because the resistant ESBL producing organisms appear to be susceptible by in vitro routine testing but result in treatment failure.The present study aims to detect the prevalence of ESBLs in organisms like E.coli and Klebsiella spp. which are responsible for many serious infections. Method: Isolates were screened for ESBL production using cefotaxime, ceftazidime and ceftriaxone by disk diffusion method. Isolates showing resistance to one or more than one of these drugs were futher subjected to Phenotypic Confirmatory Test (PCT) using CAZ/CAZ-CAC as per CLSI guidelines. Results: Of the 230 isolates, 116 (50.43%) tested positive by initial screening method. But on PCT only 94 tested positive. Out of 94 ESBL producers, 59 (62.76%) were E.coli and 35(37.23%) were Klebsiella spp. Of the various clinical samples urine 90(39%) showed maximum number of ESBL producers (32, 34%), followed by pus (27, 29%). Out of 230, 126 (54.7%) were females and 104 (45.2%) were males with a male to female ratio of 0.82:1 showing female preponderance. This study also showed increasing resistance to fluoroquinolones among ESBL producers. Conclusion: The results of our study show that there is an increased prevalence of ESBL producers in our tertiary care centre and also an increased resistance to fluoroquinolones among ESBL producers. Hence infections caused by E.coli and Klebsiella spp. which are prime producers of ESBL have to be considered seriously and proper screening methods and antibiotic policies have to be drawn to confine their spread.
ABSTRACT
BACKGROUND: The aim of this study was to compare the BD Phoenix (Beckton Dickinson Diagnostic Systems, USA) extended-spectrum beta-lactamase (ESBL) test with the Clinical and Laboratory Standards Institute (CLSI) ESBL phenotypic confirmatory test by disk diffusion (CLSI ESBL test) in Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca and Proteus mirabilis. METHODS: We tested 224 clinical isolates of E. coli, K. pneumoniae, K. oxytoca and P. mirabilis during May 2006 to March 2007. These isolates were examined by the Phoenix and the CLSI ESBL tests simultaneously. For the isolates showing discordant results between the two tests, boronic acid disk test was performed to differentiate AmpC beta-lactamase and ESBL. RESULTS: Among the 224 clinical isolates, 75 and 79 isolates were positive for ESBL by CLSI ESBL test and Phoenix test, respectively. Having detected 4 more isolates as ESBL-producers, Phoenix test showed a 98.2% agreement with a 100% sensitivity and 97.3% specificity compared with CLSI ESBL test. Among the four false positive isolates, three were AmpC-positive but ESBL-negative. CONCLUSIONS: The BD Phoenix ESBL test was sensitive and specific, and can be used as a rapid and reliable method to detect ESBL production in E. coli, Klebsiella species, and P. mirabilis.