Molecular Epidemiology of MRSA Among Patients and Employees in a Surgical Intensive Care Unit

Methicillin-resistant Staphylococcus aureus (MRSA) is a pervasive drug resistant human pathogen and has become widespread in hospitals around the world. MRSA infections cause approximately 19,000 deaths among hospitalized Americans annually. It is one of the leading causes of healthcare associated, or nosocomial infections, particularly in intensive care units. Hospital acquired MRSA (HA-MRSA) has been a battle for inpatients since the 1960's. However, in the late 1990's, a new strain of MRSA emerged. It appeared outside of the hospital setting and has been termed, community associated MRSA (CA-MRSA). Presently, CA-MRSA has been found to be spreading into the healthcare system presenting a new obstacle for patients and hospitals to overcome.   It has been suggested that employees play a role in transmission of MRSA to hospitalized patients. Since healthcare workers are at the interface between hospitals and the community, they may serve as a potential reservoir for spreading MRSA. However, there are a limited number of studies that investigate employee MRSA colonization and subsequent transmission to patients.   This study seeks to provide molecular evidence supporting the likelihood that employees play a role in MRSA transmission to patients. Furthermore, with the implementation of a version of "search and destroy", an infection control strategy, we show how reductions of hospital-acquired infections are achieved using this method.  M.S

Evaluation of Methicillin-Resistant Staphylococcus aureus Carriage and High Livestock Production Areas in North Carolina through Active Case Finding at a Tertiary Care Hospital

: Recent reports from the Netherlands document the emergence of novel multilocus sequence typing (MLST) types (e.g., ST-398) of methicillin-resistant Staphylococcus aureus (MRSA) in livestock, particularly swine. In Eastern North Carolina (NC), one of the densest pig farming areas in the United States, as many as 14% of MRSA isolates from active case finding in our medical center have no matches in a repetitive sequence-based polymerase chain reaction (rep-PCR) library. The current study was designed to determine if these non-matched MRSA (NM-MRSA) were geographically associated with exposure to pig farming in Eastern NC. While residential proximity to farm waste lagoons lacked association with NM-MRSA in a logistic regression model, a spatial cluster was identified in the county with highest pig density. Using MLST, we found a heterogeneous distribution of strain types comprising the NM-MRSA isolates from the most pig dense regions, including ST-5 and ST-398. Our study raises the warning that patients in Eastern NC harbor livestock associated MRSA strains are not easily identifiable by rep-PCR. Future MRSA studies in livestock dense areas in the U.S. should investigate further the role of pig–human interactions

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

Evaluation of Methicillin-Resistant Staphylococcus aureus Carriage and High Livestock Production Areas in North Carolina through Active Case Finding at a Tertiary Care Hospital

: Recent reports from the Netherlands document the emergence of novel multilocus sequencetyping (MLST) types (e.g., ST-398) of methicillin-resistant Staphylococcus aureus (MRSA) in livestock,particularly swine. In Eastern North Carolina (NC), one of the densest pig farming areas in the UnitedStates, as many as 14% of MRSA isolates from active case finding in our medical center have nomatches in a repetitive sequence-based polymerase chain reaction (rep-PCR) library. The currentstudy was designed to determine if these non-matched MRSA (NM-MRSA) were geographicallyassociated with exposure to pig farming in Eastern NC. While residential proximity to farm wastelagoons lacked association with NM-MRSA in a logistic regression model, a spatial cluster wasidentified in the county with highest pig density. Using MLST, we found a heterogeneous distributionof strain types comprising the NM-MRSA isolates from the most pig dense regions, including ST-5and ST-398. Our study raises the warning that patients in Eastern NC harbor livestock associatedMRSA strains are not easily identifiable by rep-PCR. Future MRSA studies in livestock dense areas inthe U.S. should investigate further the role of pig--human interactions

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 livestockand livestock workers. Industrial food animal production may be an important environmental reservoir for humancarriage of these pathogenic bacteria. The objective of this study was to investigate environmental andoccupational 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 aboutrecent environmental and occupational exposures. Home addresses were geocoded and publicly available datawere used to estimate the density of swine in residential census block groups of residence. Conditional logisticregression models were used to derive odds ratio (OR) estimates and 95% confidence intervals (CI). Presence of thescn gene in MRSA isolates was assessed. In addition, multi locus sequence typing (MLST) of the MRSA isolates wasperformed, 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 controlsthan cases were current workforce members (41.2% vs. 31.6%) Cases had a higher odds of living in census blockgroups with medium densities of swine (OR: 4.76, 95% CI: 1.36-16.69) and of reporting the ability to smell odor froma farm with animals when they were home (OR: 1.51, 95% CI: 0.80-2.86). Of 49 culture positive MRSA isolates, allwere scn positive. Twenty-two isolates belonged to clonal complex 5.Conclusions: Absence of livestock workers in this study precluded evaluation of occupational exposures. Higherodds of MRSA in medium swine density areas could reflect environmental exposure to swine or poultry

Open Access

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 regio