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Shahreen Chowdhury

Advisor: Barbara Murray, MD

Identification of widespread clones may have important implications for pathogenesis and infection control of the significant nosocomial pathogen, Enterococcus faecalis. In this study we present a novel tri-locus sequence typing (TLST) scheme which was used for subspecies differentiation and population genetics of E. faecalis. This scheme was compared with the previously established multi-locus sequence typing (MLST) scheme based on seven house-keeping genes. The TLST scheme is based on the intragenic regions of two antigenic genes, ace and salA (encoding a collagen adhesin and a cell wall associated antigen, respectively), and a gene associated with antibiotic resistance,lsa (encoding an ABC transporter). Each of the genes were sequenced and assigned allele types for 50 E. faecalis isolates representing diverse multi-locus sequence types and a few clonally linked isolates. TLST was found to be in agreement with MLST. TLST was also compared to the “gold standard” for typing isolates for hospital- epidemiology, pulsed-field gel electrophoresis (PFGE). The scheme was applied to an unknown collection of 48 hospital isolates and the results demonstrate that TLST was able to successfully identify an outbreak clone and was in agreement with PFGE typing. TLST was also applied to a set of endocarditis isolates to look at population epidemiology. This collection contained a variety of sequence types (ST), with the largest clonal cluster represented by STT-40. This scheme proved effective for both hospital- and long-term epidemiology.

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Research Info

Tri locus sequence typing of Enterococcus faecalis