Diagnosis of hospital‐acquired pneumonia and methods of testing for pathogens

SUMMARY • Hospital‐acquired pneumonia is diagnosed in patients who, in addition to abnormal shadowing on chest radiography, have ≥2 of the following: fever, abnormal white blood cell count and purulent discharge. • Treatment effect is judged from clinical symptoms and microorganism test results 2–3 days after the start of treatment, and reassessment is made with regard to change, addition or discontinuation of antimicrobial agents. • Coordination with the microbiology laboratory is extremely important in diagnosing infectious diseases. • Microorganisms isolated from tracheal aspirate at 10 6  cfu/mL (3+), from BAL at 10 4 –10 5  cfu/mL (2+) and from a protected specimen brush at 10 3  cfu/mL (1+) have a high possibility of being the causative microorganisms. • Pneumonia can almost be ruled out when no significant microbes are detected from the lower respiratory tract in patients with suspected ventilator‐assisted pneumonia (when no change has been made to antimicrobial administration within 72 h). • When MRSA or Pseudomonas aeruginosa are not detected in sputum tests, involvement of these drug‐resistant bacteria may be considered unlikely, and the case treated accordingly. • Involvement of aspiration is suspected when a number of pathogens are observed in lower respiratory tract specimens. • When antimicrobials are administered with reference to breakpoint concentrations in Western countries, differences in dosage between these countries and Japan need to be considered.