Background: Identification of the prevalence and spread of ESBL-mediated antibiotic resistance is essential especially in the hospital setting. It is for this reason, more and more studies are highlighting the importance of complementing phenotypic ESBL-detection techniques with molecular techniques in order to understand the basis and extent of this form of resistance among clinically evolved bacterial populations, especially those belonging to the Enterobacteriaceae family. However, in Trinidad and Tobago and other Caribbean countries, very little is known regarding ESBL detection rates and/or the prevalence of genes conferring ESBL resistance.
Methodology: Sixty-six Klebsiella pneumoniae isolates from clinical specimens phenotypically identified by the Microscan Walkaway-96 System as potential ESBL-producers were analysed in this study. Screening and confirmation of these isolates as ESBL producers was done by the Clinical and Laboratory Standards Institute (CLSI) approved methods. Polymerase chain reaction amplification of beta-lactamase genes bla TEM, bla SHV, bla CTX-M1, bla CTX-M2 and bla AmpC was performed to identify mechanisms of β-lactam resistance.
Results: ESBL-producing K. pneumoniae was confirmed in 78.8% (41/52) from isolates collected from a variety of sources during the period, April-July 2015. bla SHV (84.8%) and bla CTX-M (46.9%) were the predominant β-lactamase genes identified. A single K. pneumoniae isolate possessed a bla CTX-M group 2 beta-lactamase gene. RAPD analysis identified a number of epidemiologically related isolates. However, current isolates were unrelated to isolates from previous years.
Conclusion: This study revealed that among K. pneumoniae isolates exhibiting extended spectrum β-lactam resistance, there was a high prevalence of bla SHV and bla CTX-M genes. This result highlights the need for a reliable epidemiological apparatus that involves the molecular characterisation of ESBL resistance.
Keywords: Extended-spectrum beta-lactamase; Polymerase chain reaction; Random amplification of polymorphic DNA; Trinidad and Tobago.