Background: In healthcare facilities, conventional surveillance techniques using rule-based guidelines may result in\nunder- or over-reporting of methicillin-resistant Staphylococcus aureus (MRSA) outbreaks, as these guidelines are\ngenerally unvalidated. The objectives of this study were to investigate the utility of the temporal scan statistic for\ndetecting MRSA clusters, validate clusters using molecular techniques and hospital records, and determine significant\ndifferences in the rate of MRSA cases using regression models.\nMethods: Patients admitted to a community hospital between August 2006 and February 2011, and identified with\nMRSA > 48 hours following hospital admission, were included in this study. Between March 2010 and February 2011,\nMRSA specimens were obtained for spa typing. MRSA clusters were investigated using a retrospective temporal\nscan statistic. Tests were conducted on a monthly scale and significant clusters were compared to MRSA outbreaks\nidentified by hospital personnel. Associations between the rate of MRSA cases and the variables year, month, and\nseason were investigated using a negative binomial regression model.\nResults: During the study period, 735 MRSA cases were identified and 167 MRSA isolates were spa typed. Nine\ndifferent spa types were identified with spa type 2/t002 (88.6%) the most prevalent. The temporal scan statistic\nidentified significant MRSA clusters at the hospital (n = 2), service (n = 16), and ward (n = 10) levels (P ? 0.05). Seven\nclusters were concordant with nine MRSA outbreaks identified by hospital staff. For the remaining clusters, seven\nevents may have been equivalent to true outbreaks and six clusters demonstrated possible transmission events.\nThe regression analysis indicated years 2009ââ?¬â??2011, compared to 2006, and months March and April, compared to\nJanuary, were associated with an increase in the rate of MRSA cases (P ? 0.05).\nConclusions: The application of the temporal scan statistic identified several MRSA clusters that were not\ndetected by hospital personnel. The identification of specific years and months with increased MRSA rates may\nbe attributable to several hospital level factors including the presence of other pathogens. Within hospitals, the\nincorporation of the temporal scan statistic to standard surveillance techniques is a valuable tool for healthcare\nworkers to evaluate surveillance strategies and aid in the identification of MRSA clusters.
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