Community-acquired bacteria frequently detected by means of quantitative polymerase chain reaction in nosocomial early-onset ventilator-associated pneumonia. 
To test whether real-time polymerase chain reaction allows for rapid quantitative detection of Streptococcus pneumoniae, Chlamydia pneumoniae, Mycoplasma pneumoniae, and Legionella pneumophila in bronchoalveolar lavage fluids and to determine the prevalence of these pathogens in nosocomial ventilator-associated pneumonia.  Prospective epidemiologic study applying a new molecular biology-based diagnostic tool during a 27-month period.  Three medical intensive care units of a tertiary care university hospital.  One hundred patients suffering from nosocomial ventilator-associated pneumonia, hospitalized for > or =14 days, intubated for reasons other than pneumonia, and mechanically ventilated for >48 hrs.  None.  S. pneumoniae, M. pneumoniae, and C. pneumoniae were detected in bronchoalveolar lavage fluids of 100 patients in 20 (20%), three (3%), and two (2%) cases, respectively.  There of 17 (71%) revealed no growth or no significant growth by conventional culture.  In one patient, S. pneumoniae and M. pneumoniae were detected simultaneously.  Corresponding colony-forming units/mL were partly up to 10 CFU/mL with Gram stainings showing signs of acute inflammation in 80%.  A significant temporary correlation between the number of days on ventilator, development of nosocomial pneumonia, and the frequency of detection of these pathogens was found for day 4.  S. pneumoniae, M. pneumoniae, and C. pneumoniae should be considered as causative agents in critically ill patients who develop early-onset nosocomial ventilator-associated pneumonia.  Thus, empirical antimicrobial regimens should cover S. pneumoniae, Chlamydia, and Mycoplasma alike.  Quantitative polymerase chain reaction is a fast diagnostic tool allowing for detection of these bacteria within 3 hrs in pretreated patients.