Molecular characterisation of beta-lactamases-producing Enterobacteriaceae members from critical care patients

Background: This study was done to assess the prevalence of beta-lactamases and biofilm production in general and blaCTX-M, blaTEM, blaSHV and blaAmpC in particular amongst Enterobacteriaceae members in Intensive Care Unit (ICU) patients. Materials and Methods: Samples were collected aseptically from 210 ICU patients from February 2012 to December 2015. Culture, identification, antimicrobial susceptibility, extended-spectrum beta-lactamases (ESBLs), AmpC, metallo-beta-lactamase (MBL) and biofilm detection were done according to the standard protocol. Polymerase chain reaction analysis for beta-lactamase genes of the family CTX-M, TEM, SHV and AmpC was carried out. Results: Amongst 200 pathogens, most commonly isolated Enterobacteriaceae member was Escherichia coli (2 [26%]), Klebsiella pneumonia (37 [18.5%]), Klebsiella oxytoca (12 [6%]), followed by Citrobacter species (33 [16.5%]) and Serratia species (15 [8%]). E. coli (29 [55.7%]) was most commonly associated with urinary tract infection; however, the frequency of K. pneumoniae (18 [48.6%]), K. oxytoca (5 [41.6%]) and Citrobacter koseri (20 [33%]) was higher in lower respiratory tract, bloodstream and surgical site infections, respectively. Phenotypically, prevalence of ESBL, AmpC and MBL amongst Enterobacteriaceae members was 50.2%, 36.6% and 12.3%, respectively. However, blaCTX-M and blaAmpC genes were detected in 48% and 32.4% of members, respectively. BlaTEM and blaSHV were not detected in any of the isolates. The average hospital stay of ICU patients was 21 days and was associated with 48.5% mortality. Conclusion: There is a great need for informed antibiotic treatment guided by not only routine antimicrobial susceptibility but also by knowledge of ESBL, AmpC and MBL status of the isolate.