Epidemiologia clássica e molecular de pneumonias associadas à ventilação mecânica por Acinetobacter baumannii resistente/susceptível ao imipenem em pacientes internados na unidade de terapia intensiva de adultos do hospital de clínicas da Universidade Federal de Uberlândia

Abstract

Introduction: Ventilator-associated pneumonia (VAP) is associated with significant morbidity and mortality, adding considerable costs to hospital care, aspects even more significant when related to multiresistant microorganisms. Objectives: To conduct an epidemiological study of classical and molecular VAP caused by Acinetobacter baumannii, evaluate risk factors associated with these infections versus those by Pseudomonas aeruginosa, detect contamination of surfaces near patients with VAP by A. baumannii before and after cleaning, and to characterize the mechanisms of resistance to carbapenems and the clonal spread of this microorganism recovered from clinical specimen and surface. Methods: We conducted a prospective cohort study to assess the potential risk factors associated with PAVs by A. baumannii vs. P. aeruginosa in an adult intensive care unit of the Uberlandia Federal University-Hospital Clinic (UFU-HC), from April 2011 to June 2012. Clinical and epidemiological data were obtained from patient charts and evaluated by univariate and multivariate statistical analyzes. Only clinical isolates of A. baumannii were obtained from cultures of endotracheal aspirate and patients identified as having VAP by this microorganism were selected for environmental sampling. The antimicrobial susceptibility testing was performed using the automated system VITEK® 2 or by disk diffusion method and the phenotypic detection of oxacilinases through the modified Hodge test. Multiplex polymerase chain reaction was used to detect blaOXA genes and pulsed-field gel electrophoresis was performed for molecular typing. The research was approved by the ethics committee of UFU. Results: Overall, we detected 30 patients with VAP by A. baumannii and 30 by P. aeruginosa during the study period and after multiple logistic regression analysis, only trauma admission diagnosis (OR 7.2122, 95% CI 1.62 - 32.10, p = 0.0095) and inappropriate antimicrobial therapy (OR 17.2911, 95% CI 2.61 - 114.50, p = 0.0031) remained as an independent variables associated with the development of A. baumannii VAP. The hospital mortality rate (30 days) was higher, but not significant (p> 0.05) in the group with VAP by P. aeruginosa (36.67%) than by A. baumannii (29.63%). The majority (56.7%) of clinical isolates were resistant to imipenem and all those, clinical or of surface, with resistance to this antibiotic, presented the gene encoding OXA-23. Environmental contamination was more expressive in the bed rail independent of the time of collection. Overall, eight genotypes were identified, four of them with 80% similarity, with genotypes A (n = 9, 52.9%, clinical isolates) and H (n = 4, 66.6%, isolates of surface) predominating. Conclusions: Trauma as admission diagnosis and inappropriate antimicrobial therapy were the only independent risk factors associated with cases of A. baumannii VAP. Most isolates of clinical cases of A. baumannii were resistant to imipenem and presented the blaOXA-23 gene, including those recovered from surface, and were identified the coexistence of several pulsotypes in the unit, with a higher prevalence of two distinct clones A and H, respectively, in the cases of VAP and on surface.