Detection of extended spectrum beta-lactamases-producing isolates and effect of AmpC overlapping

Manal I Hassan,Alhusain J Alzahrani,Khaled R Alkharsah,Amar H Khamis,Asim Diab,Obeid E Obeid

doi:10.3855/jidc.2919

Abstract

Few reports about the prevalence and genetic basis of extended spectrum beta-lactamases (ESBLs) are available from Saudi Arabia. We sought to determine the prevalence of ESBL-producing Enterobacteriaceae in a university hospital in eastern Saudi Arabia and to characterize the ESBLs produced by these isolates at the molecular level. All clinical isolates of Escherichia coli, Klebsiella spp., and Proteus spp. collected over two years were evaluated for susceptibility to a panel of antimicrobials and were analyzed for the ESBL phenotype using screening and confirmatory tests. ESBL-positive isolates were then screened for the presence of genes encoding CTX-M, SHV, and TEM beta-lactamases by PCR. The overall prevalence of ESBL-producing isolates was 4.8% (253/5256). Most isolates (80%) were from the inpatient department. The ESBL phenotype was more frequently detected in K. pneumonia. CTX-M genes were the most prevalent ESBL genes, detected in 82% of the studied isolates. The ESBL producers demonstrated a high multidrug resistance rate (96.6%). In transconjugation assay, the same ESBL gene pattern was transmitted from 29.7% of K. pneumoniae donors to the recipient strain, and the latter exhibited concomitant decreased aminoglycosides and co-trimoxazole susceptibility. We observed the presence of ESBL screen-positive but confirmatory-negative isolates (8.9%). Phenotypic tests for the production of AmpC β-lactamase tested positive in 52% of these isolates. Further studies are needed for appropriate detection of concomitant ESBL and AmpC enzyme production among such isolates. Continued surveillance and judicious antibiotic usage together with the implementation of efficient infection control measures are absolutely required.

Highlights

Few reports about the prevalence and genetic basis of extended spectrum beta-lactamases (ESBLs) are available from Saudi Arabia
The study included all consecutive, non-duplicate ESBL-producing E. coli, Klebsiella spp, and Proteus spp that were isolated over the period of two years from various clinical specimens obtained by the clinical microbiology laboratory at a university hospital in eastern Saudi Arabia as part of routine diagnostic activities
47), other Klebsiella species (n = 29), P. mirabilis (n = 359), P. vulgaris (n = 23) and other Proteus species (n = 20)] that were screened for ESBL phenotype

Summary

Introduction

Few reports about the prevalence and genetic basis of extended spectrum beta-lactamases (ESBLs) are available from Saudi Arabia. Numerous outbreaks of infection with organisms producing extended-spectrum beta-lactamases (ESBLs) have been observed in many countries throughout the world [2,3], and these organisms have achieved notoriety for causing nosocomial infections that lead to prolonged hospital stay, increased morbidity and mortality, and increased health-care associated costs [4,5]. ESBLs evolved via point mutations of key amino acids in parent, broad spectrum beta-lactamases (TEM-1, TEM-2 and SHV-1). They have an extended spectrum profile that permits hydrolysis of oxyiminocephalosporins and monobactams but not 7-alphamethoxy-cephalosporins (cephamycins). ESBLs undergo continuous mutations, causing the Hassan et al – ESBL and AmpC production

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Discussion

Conclusion