Molecular epidemiology of extended-spectrum beta-lactamase (ESBL) carrying Enterobacteriaceae at ABM University Health Board.

Extended-spectrum beta-lactamases (ESBL) mediate resistance to 3rd generation cephalosporins and aztreonam in Enterobacteriaceae and pose major clinical problems. Screened Enterobacteriaceae were collected from PHW Microbiology ABM Swansea laboratory and were demonstrated phenotypically to be ESBL- producers by BSAC methods. Isolates were identified using the BD Phoenix Automated system and Bruker Daltonics MALDI Biotyper. 138 isolates were genetically defined as ESBL-producers (103 Escherichia coli, 32 Klebsiella spp., 2 Enterobacter cloacae and 1 Citrobacter freundii) and 4 isolates (2 E. coli, 1 Enterobacter cloacae and 1 Morganella morganii) were genetically confirmed as AmpC-producers. PCR analysis revealed that the most prevalent ESBLs were CTX-M (n=133), predominantly Group 1 (n=128), of which 51% (66/128) contained the I526-CTX- M-15 link region, which is characteristic for epidemic E. coli strain A. PFGE confirmed that these isolates had a clonal relatedness to epidemic E. coli strain A. Allele-specific PCR revealed that all E. coli positive for I526-CTX-M-15 belonged to clone 025b-ST131 (found internationally), which has a high virulence potential and encompasses diverse PFGE patterns. With the molecular epidemiology established; the sensitivity and performance of phenotypic screening and confirmatory assays were analysed so that optimal strategies to handle difficult-to-identify ESBL resistance traits could be determined. In this study, the sensitivity of ESBL screening increased to 100% when ceftazidime was used alongside cefpodoxime. Isolates harbouring ESBL genes are often difficult to treat, as options are greatly limited. Susceptibility to various well-established antibiotics, along with temocillin and tigecycline, were investigated. Temocillin and tigecycline were effective against 98% and 89% of all isolates tested. The carbapenems were the most active antibiotics with 100% of isolates susceptible to imipenem and meropenem and 99% susceptible to ertapenem. Biofilm production in E. coli was also investigated. The pgaABCD gene locus was detected in all ESBL and AmpC-producing E. coli isolates (n=105); however, only 38% of these produced a phenotypic biofilm