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Biosensor for Detection of Antibiotic Resistant Staphylococcus Bacteria
Published on: May 8, 2013
Molecular Epidemiology of a Vancomycin-Intermediate Heteroresistant Staphylococcus epidermidis Outbreak in a Neonatal
Jasmine Chong1, Caroline Quach2, Ana C Blanchard3
1Department of Epidemiology and Biostatistics, McGill University, Montreal, QC, Canada.
Abstract:
Coagulase-negative staphylococci (CoNS) have become the leading cause of bloodstream infections (BSIs) in intensive care units (ICUs), particularly in premature neonates. Vancomycin-intermediate heteroresistant CoNS (hVICoNS) have been identified as sources of BSIs worldwide, and their potential to emerge as significant pathogens in the neonatal ICU (NICU) remains uncertain. This study describes the molecular epidemiology of an outbreak of vancomycin-heteroresistant (hV) Staphylococcus epidermidis central-line-associated BSI (CLABSI) in a single tertiary care NICU and compares it to a second tertiary care NICU that had not been associated with an outbreak. Between November 2009 and April 2014, 119 S. epidermidis CLABSIs were identified in two tertiary care NICUs in Quebec, Canada. Decreased vancomycin susceptibility was identified in about 88% of all collected strains using Etest methods. However, discrepancies were found according to the Etest and population analysis profiling-area under the concentration-time curve (PAP-AUC) methods used. All strains were susceptible to linezolid, and a few isolates were nonsusceptible to daptomycin. Great genetic diversity was observed within the collection, with 31 pulsed-field gel electrophoresis (PFGE) patterns identified. The outbreak strains were all determined to be heteroresistant to vancomycin and were polyclonal. The study identified two major clones, PFGE patterns E and G, which were found in both NICUs across the 5-year study period. This suggests the persistence of highly successful clones that are well adapted to the hospital environment. hV S. epidermidis seems more common than currently realized in the NICU, and certain hV S. epidermidis clones can become endemic to the NICU. The reservoirs for these clones remain unknown at this time, and identification of the reservoirs is needed to better understand the impact of hV S. epidermidis in the NICU and to inform infection prevention strategies. In addition, there is a need to investigate and validate hV determination protocols for different species of CoNS.
Insights
Vancomycin-heteroresistant Staphylococcus epidermidis (hV S. epidermidis) bloodstream infections are a growing concern in neonatal intensive care units (NICUs). This study found persistent, genetically diverse hV S. epidermidis clones endemic in NICUs, necessitating further research into reservoirs and detection methods.
Area of Science:
- Infectious Diseases
- Microbiology
- Neonatal Medicine
Background:
- Coagulase-negative staphylococci (CoNS) are leading causes of bloodstream infections (BSIs) in neonatal intensive care units (NICUs).
- Vancomycin-intermediate heteroresistant CoNS (hVICoNS) pose a potential threat in NICUs, with their prevalence and impact not fully understood.
- Vancomycin-heteroresistant (hV) Staphylococcus epidermidis is increasingly recognized as a significant pathogen in neonatal healthcare settings.
Purpose of the Study:
- To investigate the molecular epidemiology of vancomycin-heteroresistant Staphylococcus epidermidis central-line-associated bloodstream infections (CLABSIs) in two tertiary care NICUs.
- To compare the prevalence and characteristics of hV S. epidermidis strains between NICUs with and without a documented outbreak.
- To assess the genetic diversity and clonal behavior of hV S. epidermidis causing CLABSIs over a five-year period.
Main Methods:
- Collected 119 Staphylococcus epidermidis isolates from CLABSIs in two tertiary care NICUs between November 2009 and April 2014.
- Assessed vancomycin susceptibility using Etest and population analysis profiling-area under the concentration-time curve (PAP-AUC) methods.
- Determined genetic relatedness and diversity using pulsed-field gel electrophoresis (PFGE).
Main Results:
- Approximately 88% of S. epidermidis strains exhibited decreased vancomycin susceptibility, with discrepancies noted between Etest and PAP-AUC.
- All strains remained susceptible to linezolid, with limited nonsusceptibility to daptomycin.
- Thirty-one distinct PFGE patterns were identified, indicating significant genetic diversity; two major polyclonal clones (PFGE patterns E and G) were prevalent in both NICUs throughout the study.
Conclusions:
- Vancomycin-heteroresistant S. epidermidis appears more prevalent in NICUs than previously recognized.
- Specific hV S. epidermidis clones can persist and become endemic within NICU environments.
- Further investigation into hV S. epidermidis reservoirs and validation of susceptibility testing protocols are crucial for effective infection control.
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