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Multiplex PCR Assay for Typing of Staphylococcal Cassette Chromosome Mec Types I to V in Methicillin-resistant Staphylococcus aureus
Published on: September 5, 2013
Molecular concordance of methicillin-resistant Staphylococcus aureus isolates from healthcare workers and patients
Timileyin Y Adediran1, Stephanie Hitchcock2, J Kristie Johnson3,2,1
1Department of Epidemiology and Public Health, University of Maryland School of Medicine, Baltimore, Maryland.
Background:
Methicillin-resistant Staphylococcus aureus (MRSA) is a significant nosocomial pathogen in the ICU. MRSA contamination of healthcare personnel (HCP) gloves and gowns after providing care to patients with MRSA occurs at a rate of 14%-16% in the ICU setting. Little is known about whether the MRSA isolates identified on HCP gown and gloves following patient care activities are the same as MRSA isolates identified as colonizing or infecting the patient.
Methods:
From a multisite cohort of 388 independent patient MRSA isolates and their corresponding HCP gown and glove isolates, we selected 91 isolates pairs using a probability to proportion size (PPS) sampling method. To determine whether the patient and HCP gown or gloves isolates were genetically similar, we used 5 comparative genomic typing methods: phylogenetic analysis, spa typing, multilocus sequence typing (MLST), large-scale BLAST score ratio (LSBSR), and single-nucleotide variant (SNV) analysis.
Results:
We identified that 56 (61.5%) of isolate pairs were genetically similar at least by 4 of the methods. Comparably, the spa typing and the LSBSR analyses revealed that >75% of the examined isolate pairs were concordant, with the thresholds established for each analysis.
Conclusions:
Many of the patient MRSA isolates were genetically similar to those on the HCP gown or gloves following a patient care activity. This finding indicates that the patient is often the primary source of the MRSA isolates transmitted to the HCP, which can potentially be spread to other patients or hospital settings through HCP vectors. These results have important implications because they provide additional evidence for hospitals considering ending the use of contact precautions (gloves and gowns) for MRSA patients.
Insights
Methicillin-resistant Staphylococcus aureus (MRSA) on healthcare worker gloves and gowns is often genetically identical to the patient's MRSA. This suggests patients are the primary source of contamination, potentially impacting contact precaution protocols.
Area of Science:
- Infectious Diseases
- Microbiology
- Genomics
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) is a major healthcare-associated pathogen, particularly in intensive care units (ICUs).
- Contamination of healthcare personnel (HCP) gloves and gowns with MRSA occurs in 14-16% of patient care interactions in ICUs.
- Limited data exists on the genetic relatedness between MRSA found on HCP personal protective equipment and MRSA colonizing or infecting patients.
Purpose of the Study:
- To determine the genetic similarity between MRSA isolates from patients and those found on the gloves and gowns of healthcare personnel (HCP).
- To investigate the source of MRSA contamination on HCP attire following patient care activities in the ICU.
Main Methods:
- A cohort of 388 patient MRSA isolates and corresponding HCP gown/glove isolates were analyzed.
- 91 isolate pairs were selected using probability to proportion size (PPS) sampling.
- Five comparative genomic typing methods were employed: phylogenetic analysis, spa typing, multilocus sequence typing (MLST), large-scale BLAST score ratio (LSBSR), and single-nucleotide variant (SNV) analysis.
Main Results:
- 61.5% (56/91) of isolate pairs demonstrated genetic similarity by at least four typing methods.
- spa typing and LSBSR analyses showed concordance in over 75% of examined isolate pairs.
- A significant genetic similarity was observed between patient MRSA and MRSA isolates on HCP attire.
Conclusions:
- Patients are frequently the source of MRSA isolates transmitted to HCP's gloves and gowns.
- This transmission can potentially lead to the spread of MRSA within healthcare settings via HCP.
- Findings support re-evaluation of current contact precaution (gloves and gowns) policies for MRSA patients.
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