Citation
Weng, Poh Leng
(2013)
Characterization of Enterococcus faecium and Enterococcus faecalis clinical isolates in a Malaysian Hospital.
Masters thesis, Universiti Putra Malaysia.
Abstract
Enterococcus faecium and Enterococcus faecalis have been well documented as
ubiquitous, Gram-positive cocci, opportunistic nosocomial pathogens. In recent
decades, they have been recognized as the primary agent for nosocomial infections
in many countries worldwide. The aims of the study were to determine the molecular
characterization of E. faecium and E. faecalis isolated from patients in a Malaysian
hospital focused on enterococcal surface protein (esp) gene, biofilm formation,
association of esp gene with antibiotic resistance and genetic relatedness amongst
the isolates collected. Samples were collected from a local tertiary hospital from May
2009 to March 2010 and subjected to characterization via biochemical identification,
antibiotic susceptibitilty tests and DNA extraction. PCR was performed for genotypic
identification and esp gene detection and MLST of isolates. Association of biofilm
with the presence of esp gene was also examined with crystal violet assay.
Enzymatic digestion with SmaI and PFGE typing were used to determine genetic
relatedness of some strains. In this study, E. faecalis (n=52) was found to be most commonly isolated amongst 80 isolates followed by E. faecium (n=28). The higher
resistance rates were exhibited by E. faecium in decreasing order: tazobactampiperacillin
(96.4%), ampicillin (92.9%), high-level gentamicin (89.3%) and penicillin
(82.1%). Whereas E. faecalis demonstrated slightly lower resistance rates: high-level
gentamicin (25.0%), penicillin (7.7%), ampicillin (1.9%) and tazobactam-piperacillin
(1.9%) respectively. No vancomycin and teicoplanin resistant enterococci was found.
The prevalence of esp gene was found higher in E. faecium (78.5%) compared to E.
faecalis (46.2%). However, the prevalence of this gene was more predominantly
found in isolates that were resistant to ampicillin (74.1%) and tazobactam-piperacillin
(65.8%). Ampicillin–resistant strains and esp gene were strongly associated with the
genetic clustering in clonal complex-17. A significant strength of relationship between
esp gene and biofilm formation was strongly observed in E. faecium than in E.
faecalis. Some isolates without the esp gene were also found to form biofilms and
these findings suggest esp might play a significant role although multiple factors
might also be involved apart from environmental conditions. PFGE typing revealed
high genetic diversity of enterococcal isolates and no indication of outbreaks.
Clonally related ST types (ST6, ST16, ST28, E. faecalis; ST17, ST 78, ST203, E.
faecium), which are circulating globally and two new ST types (ST399, E. faecalis;
ST601, E. faecium) were obtained via MLST. ST6, ST16, ST28 and ST179 of E.
faecalis were documented and of particular concern ST6 is associated with clonalcomplex
2, a representative of hospital adapted complexes and the most often
reported amongst hospital isolates ST type. ST type of E. faecium: ST17, ST78 and
ST203, have been widely linked to CC17, which is associated worldwide spread and
hospital outbreaks. The conclusion drawn from this study is that E. faecium exhibited
high resistance rate, which is expected and observed in other countries. Strong association of esp gene with biofilm formation in E. faecium would suggest esp gene
as a potential marker for line-associated infections. In addition, detection of several
ST types in both species should prompt proper surveillance system to be carried out
in the near future.
Download File
Additional Metadata
Actions (login required)
|
View Item |