Background Since the original community-acquired cases of methicillin-resistant Staphylococcus aureus (MRSA) were first described in the early 1980s, there is an increased awareness of this pathogen throughout the United States. Originally described as outbreaks among those living in close quarters, there appears to be an increase in cases among patients without traditional risk factors.
Objectives To determine if the prevalence of CA-MRSA at the University of Mississippi Medical Center (UMMC) is increasing from June 2000-May 2001 to June 2004-May 2005. Secondary objectives are to determine the relationships that health risks, race, gender, and age play in this complex health care issue.
Methods All cases of MRSA-positive cultures were identified by the UMMC Microbiology Laboratory from June 2000-May 2001 and June 2004-May 2005. Using previously described inclusion criteria, charts were reviewed and cases were determined to be community acquired. These cases were further characterized by age, sex, ethnicity, and comorbid conditions.
Results Of the 453 MRSA cases in 2000-2001, 33 (7%) were determined to be community acquired. Of the 935 cases in 2004-2005, 219 (23%) were determined to be community acquired. This represented a statistically significant increase in the prevalence of outpatient cases from 24 to 129 cases per 100,000 (p < .01). The percentages of MRSA cases that were considered to be community acquired also showed a statistically significant increase from 7% in the first time period to 23% in the later time period (p < .01). There was noted to be a shift in the ethnic diversity of patients with CA-MRSA with a decrease in the percentage of cases in African Americans from 87.9 to 60.7% (p < .01) and a significant increase in the percentage of Caucasian patients from 12.1 to 35.2% (p < .01) over these two time periods. Other measured outcomes, including age, gender, illicit drug use, human immunodeficiency virus (HIV), diabetes mellitus, liver disease, and illicit drug use, did not change significantly over these time periods. HIV and diabetes mellitus continued to be associated risk factors with CA-MRSA, with 13.2% having HIV (p < .01) and 17.8% having diabetes mellitus (p < .01) during the last time period. Although there was a large percentage who had comorbidities, the majority of patients (54.3%) had no traditional risk factors.
Conclusion As has been observed in other parts of the country, CA-MRSA cases have increased in our institution, as have the percentage of MRSA cases that are community acquired. African American ethnicity appears to no longer be associated with a higher prevalence of CA-MRSA in our institution. Although diabetes mellitus and HIV continue to be associated with a higher prevalence of CA-MRSA, the majority of patients with CA-MRSA do not have underlying risk factors.
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