Úlcera por pressão colonizada por Staphylococcus aureus resistente a meticilina: reservatório, fatores de risco e evolução para infecção local e bacteremia em um hospital de ensino e instituições de longa permanência para idosos

Abstract

Introduction: pressure ulcers (PU) predispose to colonization by methicillin-resistant Staphylococcus aureus (MRSA) and represent an important reservoir of this organism in hospitals and health care institutions for elderly in the United States and Europe. Objectives: To evaluate the relationship between colonization and infection of UP by Staphylococcus aureus / MRSA, risk factors and outcome for bloodstream infection and nasal colonization by these microorganisms in patients with stage II or greater PU in hospitalized patients and residents of Long Term Care Facilities (LTCF) for elderly. Methods: The study was conducted at Clinical Hospital of Federal University of Uberlandia (CH-FUU) and three LTCF of city. The study design was prospective cohort in the hospital and an observational, longitudinal, in the LTCF. We included 226 volunteers, under active surveillance, of whom 145 were hospitalized and had stage II or greater PU, and 81 residents from LTCF, with or without PU, for 20 months period, from May to December 2005 and August 2009 - July 2010. PU were classified according to severity (stage I to IV) and the presence or absence of local infection by evaluation of clinical signs and microscopic by positive evaluation of wound s smears, by the ratio of inflammatory cells (polymorphonuclear) to epithelial cells of 2:1 per field, after staining by Giemsa. By active search, we evaluated the records of volunteers until discharge, death or transfer unit with the data reported on individual records. Clinical specimens were collected with swabs of the stage II or greater PU and nasal mucosa of volunteers in biweekly intervals until a positive result for S. aureus. The primary culture was carried through salt mannitol agar. The MRSA bloodstream infection was defined as blood culture positive. A single isolate of MRSA was found by volunteer and gender/ species identification was performed by classical phenotypic tests. The antibiogram was performed by agar diffusion technique according to CLSI standards 2005/2009. Results: Univariate statistical analysis of risk factors was performed by chi-square and Fisher exact test. The variables that showed association in the univariate analysis were analyzed by multivariate logistic regression model. The study was approved by the research ethics of the UFU, MG (118/05, 370/09). In the hospitalized group were identified 63 (43.5%) patients colonized with MRSA in UP, however, none of the analyzed risk factors was independently associated with this colonization. Association was found between patients with positive blood cultures and colonized by MRSA (OR: 19.0, 95% CI, 2.4 to 151.1, P <0.001) as well as for mortality (OR: 21.9, 95 % CI, 1.23 to 391.5, P = 0.002). The independent risk factors for MRSA bacteremia were two comorbidities (OR: 6.26 95% CI, 1.01 to 39.1, P = 0.05) and infected PU (OR: 12.75, 95% CI, 1.22 to 132.9, P = 0.03). The frequency of nasal colonization by MRSA was high in the hospitalized group, not being found in residents of LTCF. Conclusions: The study demonstrated that pressure ulcer colonized by MRSA was an epidemiologic reservoir potential of this organism in the hospital, with high-risk for MRSA bacteremia for patients and unfavorable prognosis as to the evolution. Due to the large dependence of these patients and their prolonged stay in the main hospital units, we recommend more attention on the participation of PU in the epidemiology of infections by multidrug-resistant bacteria as MRSA.