Medical and Household Characteristics Associated with Methicillin Resistant Staphylococcus aureus Nasal Carriage among Patients Admitted to a Rural Tertiary Care Hospital

Leah Schinasi,David B Richardson,Steve Wing,Kerri L.Augustino,Delores L Nobles,Keith M Ramsey,Pia D M Macdonald,Jill R Stewart,Tara C Smith

doi:10.1371/journal.pone.0073595

Abstract

BackgroundMethicillin resistant Staphylococcus aureus (MRSA) poses a threat to patient safety and public health. Understanding how MRSA is acquired is important for prevention efforts. This study investigates risk factors for MRSA nasal carriage among patients at an eastern North Carolina hospital in 2011.MethodsUsing a case-control design, hospitalized patients ages 18 – 65 years were enrolled between July 25, 2011 and December 15, 2011 at Vidant Medical Center, a tertiary care hospital that screens all admitted patients for nasal MRSA carriage. Cases, defined as MRSA nasal carriers, were age and gender matched to controls, non-MRSA carriers. In-hospital interviews were conducted, and medical records were reviewed to obtain information on medical and household exposures. Multivariable conditional logistic regression was used to derive odds ratio (OR) estimates of association between MRSA carriage and medical and household exposures.ResultsIn total, 117 cases and 119 controls were recruited to participate. Risk factors for MRSA carriage included having household members who took antibiotics or were hospitalized (OR: 3.27; 95% Confidence Interval (CI): 1.24–8.57) and prior hospitalization with a positive MRSA screen (OR: 3.21; 95% CI: 1.12–9.23). A lower proportion of cases than controls were previously hospitalized without a past positive MRSA screen (OR: 0.40; 95% CI: 0.19–0.87).ConclusionThese findings suggest that household exposures are important determinants of MRSA nasal carriage in hospitalized patients screened at admission.

Highlights

When it was first identified in the 1960s, Methicillin resistant Staphylococcus aureus (MRSA) was a nosocomial pathogen [1]
To increase the probability of exposure to livestock for the parent study, participants were restricted to residents of swine-producing zip codes in which the permitted number of swine was equal to or greater than the median number listed with the North Carolina Division of Water Quality (North Carolina zip codes with 1,032,750 or more permitted swine)
4 cases and 3 controls were excluded based on having addresses outside the eligible zip codes, leaving 117 cases and 119 controls for analysis

Summary

Introduction

When it was first identified in the 1960s, Methicillin resistant Staphylococcus aureus (MRSA) was a nosocomial pathogen [1]. In the 1990s, the epidemiology of this virulent pathogen changed; it was identified in people without recent medical contact [2]. Healthcare associated (HA) and community associated (CA) MRSA strains are genetically distinct [3]. The epidemiology of MRSA is complex and distinctions between CA and HA strains are increasingly difficult to disentangle. Clinical and demographic differences in the epidemiology of MRSA have been observed among regions and sub-communities within the same area [13,14]. Region specific investigations of the sources of acquisition are important for informing infection prevention. Methicillin resistant Staphylococcus aureus (MRSA) poses a threat to patient safety and public health. This study investigates risk factors for MRSA nasal carriage among patients at an eastern North Carolina hospital in 2011

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