A case control study of environmental and occupational exposures associated with methicillin resistant Staphylococcus aureus nasal carriage in patients admitted to a rural tertiary care hospital in a high density swine region.

BACKGROUND: Distinct strains of methicillin resistant Staphylococcus aureus (MRSA) have been identified on livestock and livestock workers. Industrial food animal production may be an important environmental reservoir for human carriage of these pathogenic bacteria. The objective of this study was to investigate environmental and occupational exposures associated with nasal carriage of MRSA in patients hospitalized at Vidant Medical Center, a tertiary hospital serving a region with intensive livestock production in eastern North Carolina. METHODS: MRSA nasal carriage was identified via nasal swabs collected within 24 hours of hospital admission. MRSA carriers (cases) were gender and age matched to non-carriers (controls). Participants were interviewed about recent environmental and occupational exposures. Home addresses were geocoded and publicly available data were used to estimate the density of swine in residential census block groups of residence. Conditional logistic regression models were used to derive odds ratio (OR) estimates and 95% confidence intervals (CI). Presence of the scn gene in MRSA isolates was assessed. In addition, multi locus sequence typing (MLST) of the MRSA isolates was performed, and the Diversilab® system was used to match the isolates to USA pulsed field gel electrophoresis types. RESULTS: From July - December 2011, 117 cases and 119 controls were enrolled. A higher proportion of controls than cases were current workforce members (41.2% vs. 31.6%) Cases had a higher odds of living in census block groups with medium densities of swine (OR: 4.76, 95% CI: 1.36-16.69) and of reporting the ability to smell odor from a farm with animals when they were home (OR: 1.51, 95% CI: 0.80-2.86). Of 49 culture positive MRSA isolates, all were scn positive. Twenty-two isolates belonged to clonal complex 5. CONCLUSIONS: Absence of livestock workers in this study precluded evaluation of occupational exposures. Higher odds of MRSA in medium swine density areas could reflect environmental exposure to swine or poultry.

The impact of a "search and destroy" strategy for the prevention of methicillin-resistant Staphylococcus aureus infections in an inpatient rehabilitation facility.

OBJECTIVE: To determine how the implementation of a methicillin-resistant Staphylococcus aureus (MRSA) control program in an inpatient rehabilitation facility (IRF) affects MRSA health care-associated infections (MRSA-HAIs). DESIGN: A retrospective chart review. SETTING: IRF affiliated with Vidant Medical Center, an 861-bed, acute-care teaching hospital for The Brody School of Medicine at East Carolina University. PATIENTS: Seventy-nine adult patients in the IRF who developed a MRSA-HAI from February 2005 through January 2011. INTERVENTIONS: Both the acute care hospital and the affiliated inpatient rehabilitation unit began screening 100% of admissions for MRSA nasal carriage, with decolonization of positive carriers, starting in February 2007. MAIN OUTCOME MEASUREMENTS: Yearly rates of MRSA-HAI per 1000 patient-days were compared in the IRF before and after the intervention. RESULTS: The weighted mean monthly infection rate before the intervention (February 2005 through January 2007) was 1.0714 per 1000 patient days compared with 0.6557 per 1000 patient days after the intervention (February 2007 through January 2011). The decreased infection rates after the intervention were statistically significant (P = .0315). CONCLUSIONS: The implementation of an all-admissions MRSA screening program with decolonization of positive carriers in an IRF affiliated with an acute care hospital resulted in decreased MRSA-HAI rates in the IRF. When developing surveillance guidelines for MRSA, IRFs should be cognizant of infection rate trends and of the affiliated hospital's scope of policies and practices for infection prevention and control.

Medical and household characteristics associated with methicillin resistant Staphylococcus aureus nasal carriage among patients admitted to a rural tertiary care hospital.

BACKGROUND: Methicillin 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. METHODS: Using 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. RESULTS: In 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). CONCLUSION: These findings suggest that household exposures are important determinants of MRSA nasal carriage in hospitalized patients screened at admission.

Importance of methicillin-resistant Staphylococcus aureus eradication in carriers to prevent postoperative methicillin-resistant Staphylococcus aureus surgical site infection.

Although infrequent, postoperative methicillin-resistant Staphylococcus aureus (MRSA) surgical site infection (SSI) is associated with significant morbidity and cost. Previous studies have identified the importance of MRSA screening to diminish the risk of postoperative MRSA SSI. The current study quantifies the importance of eradication of the MRSA carrier state to prevent MRSA SSI. Beginning February 2007, all admissions to an 800-bed tertiary care hospital were screened for MRSA by nasal swab using rapid polymerase chain reaction-based testing. Patients found to be nasal carriers of MRSA were treated with 2 per cent mupirocin nasal ointment and 4 per cent chlorhexidine soap before surgery. The subset of patients undergoing procedures that are part of the Surgical Care Improvement Project (SCIP) were followed for MRSA SSI (n = 8980). The results of preoperative MRSA screening and eradication of the carrier state were analyzed. Since the initiation of universal MRSA screening, 11 patients undergoing SCIP procedures have developed MRSA SSI (0.12%). Of these, six patients (55%) had negative preoperative screens. Of the five patients with positive preoperative screens, only one received treatment to eradicate the carrier state. In patients who develop MRSA SSI, failure to treat the carrier state before surgery results in MRSA SSI.

Active surveillance screening of MRSA and eradication of the carrier state decreases surgical-site infections caused by MRSA.

BACKGROUND: Surgical-site infections (SSI), because of MRSA, are a challenge for acute care hospitals. The current study examines the impact of best practices and active surveillance screening for MRSA on reduction of MRSA SSIs. STUDY DESIGN: Beginning February 2007, all admissions to a 761-bed tertiary care hospital were screened for MRSA by nasal swab using polymerase chain reaction-based testing. Positive nasal carriers of MRSA were treated before operation. The subset of patients undergoing procedures that are part of the Surgical Infection Prevention Project were followed for MRSA SSIs. SSI rates (per 100 procedures) were determined using the National Nosocomial Infection Surveillance definitions. MRSA SSI rates were compared before and after the MRSA screening intervention. Differences were analyzed using Fisher's exact test and chi-square with Yate's continuity correction. Where specimens were available, genotyping of MRSA was performed using a commercially available assay. RESULTS: After universal MRSA surveillance, 5,094 patients underwent Surgical Infection Prevention Project procedures. The rate of MRSA SSI decreased from 0.23% to 0.09%. The reduction was most pronounced in joint-replacement procedures (0.30% to 0%; p = 0.04). No other differences were statistically significant. Of the seven patients in whom MRSA SSI developed after universal screening, four had positive MRSA screens; none had received preoperative eradication of MRSA. In two of these patients, the genotype of MRSA detected on screening and in SSI was genetically indistinguishable. CONCLUSIONS: Surveillance for MRSA and eradication of the carrier state reduces the rate of MRSA SSI.