Pathogens in the lower respiratory tract of intensive care unit patients: Impact of duration of hospital care and mechanical ventilation

Abstract

Ventilator-associated pneumonia (VAP), the most common hospital-acquired infection in intensive care unit (ICU) patients, is caused by bacteria in the lower respiratory tract of mechanically ventilated patients. The current study was focused on 443 bacterial isolates from the lower respiratory tract of mechanically ventilated ICU patients (n = 346) in a Swedish University Hospital. Data were obtained from a prospective infection control database covering 9 y (2002-2010). We analysed the correlation between duration of hospital care and mechanical ventilation at the time of sampling on the occurrence of different pathogens. Duration of hospital care and mechanical ventilation prior to sampling was similarly short for Streptococcus pneumoniae, beta-streptococci, and Haemophilus influenzae (≤ 2 days). In contrast, duration of hospital care and mechanical ventilation were longest for Stenotrophomonas maltophilia (6 and 11 days). For Staphylococcus aureus, the most common Gram-positive isolate, the duration was longer than for S. pneumoniae but shorter than for most Gram-negative bacteria. With the exception of S. maltophilia and Pseudomonas aeruginosa, the median duration of mechanical ventilation was short and similar for most bacteria. In samples taken on the first day of mechanical ventilation, the rate of pathogens expected to be resistant to cefotaxime was 23%. The occurrence of pathogens with high antibiotic resistance in the lower respiratory tract increases with increased duration of hospital care and mechanical ventilation. An equally important result is that pathogens resistant to third-generation cephalosporins were more common than expected, even after a very short duration of hospital care and mechanical ventilation.