Comparison of Disc Diffusion Methods for the Detection of Extended-Spectrum Beta Lactamase-Producing Enterobacteriaceae

Abstract

Background:Resistance to broad-spectrum β lactams, mediated by extended-spectrum β lactamases (ESBLs), is an increasing problem world wide. This resistance poses problems for in vitro testing and reporting. Increased prevalence of ESBLs among Enterobacteriaceae creates a great need for laboratory testing methods that will accurately identify their presence.Materials and Methods:During the study, the Enterobacteriaceae isolated were tested for the presence of ESBL by the National Committee for Clinical Laboratory Standards (NCCLS) screening test, Jarlier double disc synergy (approximation) test (DDST) and NCCLS phenotypic confirmatory test (PCT), and compared their efficiency in detection.Results:A total of 313 Enterobacteriaceae were isolated and tested for the presence of ESBL. NCCLS PCT identified 200 (63.89%) as ESBL producers and DDST identified 176 (56.23%), with a P-value of <0.001. Among the screening agents, ceftazidime had a better sensitivity (89.49%) and specificity (95.74%).Conclusions:Close monitoring of the susceptibility pattern of isolates and careful spacing with specific discs can identify many ESBL producers. Ceftazidime has a better sensitivity and specificity as a screening agent. A combination of different tests can be useful for accurate identification.

Comparison Between Phenotypic Confirmatory Test & Double Disc Synergy Test in Detection of Extended Spectrum b-Lactamases Producers Among Gram-Negative Bacilli

“…Closely similar to the present study, Dalela (2012) 14 . Of the two tests, used in the study, phenotypic confirmatory test found to be more sensitive procedure than double disc synergy test for the detection of ESBLs producing organisms.…”

“…Similar findings were also reported by some other studies 1,16,17,18 . For this reason, some authors recommended phenotypic confirmatory test for the detection of ESBLs producers 14,18,19 .…”

Phenotypic ESBL Detection in <i>Acinetobacter baumannii</i>: A Real Challenge

“…The present study confirms that PCDDT is efficient in detection of ESBL (Babypadmini and Appalaraju, 2004) as compared to DDST (Lim et al, 2007), and detected 100 ESBL-producers as opposed to ~15% by DDST. The PCDDT is reported as efficient method among all tested ESBL detection methods which identified majority of the ESBL producing isolates from elsewhere too (Giriyapur et al, 2011;Ndiba, 2013). The DDST is not a standardized procedure and the choice of the drug to be tested and the optimum distance between the discs varies in different studies (Datta et al, 2004).…”

Phenotypic Cofirmatory Disc Diffusion Test (PCDDT), Double Disc Synergy Test (DDST), E-Test Os Diagnostic Tool for Detection of Extended Spectrum Beta Lactamase (ESΒL) Producing Uropathogens

“…and may disseminate new host, for example, produced by Neisseria gonorrhea and Hemophillus influenza [9]. ESBLs are plasmid or chromosomal mediated β-lactamases (β-lactamases are enzymes that cleave the β-lactam ring) of already existing mutant β-lactamases (SHV-1, TEM-1 and TEM-2) as a result of frequent use of third generation cephalosporin's and aztreonam [10,11]. Clavulanic acid or sulbactum are used as inhibitors of ESBLs [5].…”