[Prevalence and risk factors of methicillin-resistant Staphylococcus aureus colonization among residents living in long-term care facilities in southern Spain].

Introduction: Methicillin-resistant Staphylococcus aureus (MRSA) has become the most important problem related to multiresistant microorganisms in the health care system. Long-term-care facilities (LTCFs) are one of the main reservoirs of this microorganism. The objective of our study was to determine the prevalence and factors associated with MRSA colonization among subjects living in LTCFs in southern Spain.

Methods: During the period from 1st April 2009 to 30th June 2010, all subjects living in 17 LTCFs of our area were included in a cross-sectional study. Patients were screened by using nasal swabs and these were cultured in a chromogenic media. Suspected S. aureus colonies were identified by the latex agglutination test. Testing for antimicrobial identification and susceptibility was performed by an automated system. A logistic regression model was built, in which to be colonized by MRSA was the dependent variable, and covariates were entered if a difference with P<.2 was detected in the bivariate analysis. Residents were classified as MRSA carriers, methicillin-susceptible S. aureus carriers and non-carriers.

Results: Seven hundreds and forty-four subjects were included. There were 481 (65%) females. The median (Q1-Q3) age was 81 (74-86) years. Seventy-nine (10.6%) and 67 (9%) were colonized by MRSA and methicillin-susceptible S. aureus, respectively. Significant risk factors for MRSA carriers were recent antibiotic use, previous hospital admission in the last three months, a high comorbidity measured by Charlson index and a history of colonization by MRSA.

Conclusions: The prevalence of MRSA colonization in the LTCFs of our area is similar to that described in others European countries. In our institutions, subjects with recent antibiotic use, a high comorbidity, a history of MRSA colonization and a hospital admission in the last three months are more susceptible to be colonized by MRSA.