Epidemiology of Ventilator-Associated Pneumonia, microbiological diagnostics and the length of antimicrobial treatment in the Polish Intensive Care Units in the years 2013-2015

Background: Ventilator-associated pneumonia (VAP) is a common nosocomial infection in intensive care units (ICUs). The objective of this study was to describe the epidemiology and microbiology of VAP in Polish ICUs from 2013 to 2015, as well as to understand how these depended on the diagnostic methods used to identify VAP pathogens and the clinical strategy for VAP treatment. Methods: This observational study was carried out in seven Polish adult ICUs. VAP surveillance was based on the European Healthcare-associated Infections Surveillance Network recommendations and was defined as pneumonia occurring more than 48 h after receiving mechanical ventilation, with symptom onset 3 days or more after the hospital stay. Depending on the microbiological diagnostic method, VAP cases were classified as PNEU-1 (positive quantitative culture from minimally contaminated lower respiratory tract specimen such as broncho-alveolar lavage, protected brush or distal protected aspirate) or other VAP cases. Results: The incidence of VAP was 8.0% and the incidence density: 12.3/1000 ventilator days. Microbiological diagnosis was made using PNEU-1 in 80 cases (39%); over the study duration, the proportion of cases diagnosed with PNEU-1 increased from 14 to 60% (p < 0.001). The predominant etiologic agents causing VAP were Enterobacteriaceae (32.6%) and non-fermenting Gram-negative bacteria (27.6%). The causative microbe varied significantly depending on the diagnostic method: in cases diagnosed using PNEU-1, Staphylococcus aureus (21.3%) and Klebsiella pneumoniae (12.5%) were the dominant organisms, whereas in other VAP cases, Acinetobacter baumannii (23.8%) was commonly observed. The length of antibiotic treatment in cases diagnosed with PNEU-1 was shorter than for other VAP cases (7.2 vs. 9.1 days, p < 0.005), as was the duration of hospitalization (49 vs. 51.8 days, p < 0.001). Antibiotic resistance was a particular concern for A. baumannii isolates, which were highly resistance to imipenem (70.6%) and meropenem or doripenem (52.9%). K. pneumoniae isolates demonstrated resistance to ampicillin (90.3%), ceftazidime (71.0%) and third-generation cephalosporins (74.2%). Conclusion: A change over time was observed in the microbiological diagnostic methods used for patients with VAP. A. baumannii was observed mainly in VAP cases diagnosed using substandard methods (non-PNEU-1). The duration of treatment for VAP patients diagnosed properly using PNEU-1 was shorter.