Microbial aetiology of healthcare associated pneumonia in Spain: a prospective, multicentre, case-control study

Healthcare-associated pneumonia (HCAP) is actually considered a subgroup of hospital-acquired pneumonia due to the reported high risk of multidrug-resistant pathogens in the USA. Therefore, current American Thoracic Society/Infectious Diseases Society of America guidelines suggest a nosocomial antibiotic treatment for HCAP. Unfortunately, the scientific evidence supporting this is contradictory.

We conducted a prospective multicentre case-control study in Spain, comparing clinical presentation, outcomes and microbial aetiology of HCAP and community-acquired pneumonia (CAP) patients matched by age (±10 years), gender and period of admission (±10 weeks).

476 patients (238 cases, 238 controls) were recruited for 2 years from June 2008. HCAP cases showed significantly more comorbidities (including dysphagia), higher frequency of previous antibiotic use in the preceding month, higher pneumonia severity score and worse clinical status (Charslon and Barthel scores). While microbial aetiology did not differ between the two groups (HCAP and CAP: Streptococcus pneumoniae: 51% vs 55%; viruses: 22% vs 12%; Legionella: 4% vs 9%; Gram-negative bacilli: 5% vs 4%; Pseudomonas aeruginosa: 4% vs 1%), HCAP patients showed worse mortality rates (1-month: HCAP, 12%; CAP 5%; 1-year: HCAP, 24%; CAP, 9%), length of hospital stay (9 vs 7 days), 1-month treatment failure (5.5% vs 1.5%) and readmission rate (18% vs 11%) (p<0.05, each).

Despite a similar clinical presentation, HCAP was more severe due to patients' conditions (comorbidities) and showed worse clinical outcomes. Microbial aetiology of HCAP did not differ from CAP indicating that it is not related to increased mortality and in Spain most HCAP patients do not need nosocomial antibiotic coverage.