Patients with MVAP identified during the studied period showed similar frequency to those reported in medical literature. Thus, this study corroborated that this is still a relevant medical problem in this hospital. Acinetobacter baumannii and Pseudomonas aeruginosa were the most frequently isolated microorganisms from patients with MVAP. Antimicrobial treatment, empirical or not, are still the main risk factors for the development of multidrug-resistant strains of bacteria. The rate of resistance to antibiotics of Acinetobacter baumannii and Pseudomonas aeruginosa strains isolated from patients with MVAP was higher than those isolated from infected patients without MAVP. Tigecycline and colistin were the only antibiotics fully effective against Acinetobacter baumannii strains isolated in 2011 from patients with MVAP; against Pseudomonas aeruginosa strains, only colistin was fully effective.

Objective: This observational study described the characterization of bacteria isolated from the lower respiratory tract of ventilated patients hospitalized in intensive care units.The demonstration of isolated microorganism resistance to antibiotics and a time-trend analysis of infection comparing a 48-month period were also other objectives.Method: Semi-quantitative assays of 1254 samples taken from 741 ventilated patients were performed, while pathogens were identified using the Enterotube II assay and VITEK 2 Compact equipment. Bacterial resistance to antibiotics was assessed by the Kirby-Bauer disc diffusion method and time-trend analysis of infection was based on data recorded by hospital microbiology laboratories.

INTRODUCTION Nosocomial pneumonia associated with use of mechanical ventilators is one of the greatest challenges confronted by intensivists worldwide. The literature associates several bacteria with this type of infection; most common in intensive care units are Acinetobacter baumannii, Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus and some of the Enterobacteriaceae family.OBJECTIVES To identify the causal agents of nosocomial ventilatorassociated pneumonia in patients receiving mechanical ventilation in the intensive care units of Havana's Hermanos Ameijeiras Clinical-Surgical Teaching Hospital in 2011, and to characterize their antibiotic resistance. METHODS A cross-sectional descriptive study was conducted using hospital administrative data of quantitative cultures from positive tracheal aspirates for January through December, 2011. Records were analyzed from 77 intensive care unit patients who developed nosocomial ventilator-associated pneumonia. Variables examined were age and sex, and pathogens identifi ed from culture of tracheal aspirate and related antibiotic susceptibility.RESULTS Species most frequently isolated were: Acinetobacter baumannii in 53 patients (68.8%), Pseudomonas aeruginosa in 34 patients (44.2%), other species of Pseudomonas in 15 patients (19.5%), and Serratia marcescens, Klebsiella pneumoniae, and Escherichia coli in 12 patients each (15.6%). Some patients presented more than one pathogen in concurrent or successive infections. Antimicrobial susceptibility testing found high percentages of resistance to antibiotics in all these pathogens. Least resistance was found to colistin. CONCLUSIONSThe prevalence of antibiotic resistance in bacteria causing nosocomial ventilator-associated pneumonia is of concern. Colistin is the drug of choice among the antibiotics reviewed, but sensitivity to other antibiotics should be assessed to search for more appropriate broad-spectrum antibiotics for treating nosocomial ventilator-associated pneumonia. Our results also suggest the need to strengthen infection control efforts, particularly in intensive care units, and to reassess compliance with quality control procedures. Multidisciplinary research involving microbiologists, epidemiologists, internists and intensivists is needed to fully understand the etiological and resistance patterns observed.

Contribución de los autores:Manuel Medell: caracterización de cepas y redacción del documento. Marcia Hart y María Luisa Batista: recolección de cepas y revisión del manuscrito. ARTÍCULO ORIGINAL Biomédica 2014;34(Supl.

This research corroborated that these nosocomial infections are a relevant medical problem in our context. The most prevalent bacterial infections in the lower respiratory tract of ventilated patients were by Acinetobacter spp., Pseudomonas spp. and Klebsiella spp. The panel of antibiotics used as preventive therapy was not the solution of infections and probably induced drug-resistance mechanisms in these isolated microorganisms.