Clinical and microbiological evaluation of hemodialysis-associated pneumonia (HDAP): should HDAP be included in healthcare-associated pneumonia?

Although hemodialysis-associated pneumonia (HDAP) was included among the healthcare-associated pneumonias (HCAP) in the 2005 American Thoracic Society (ATS)/Infectious Diseases Society of America (IDSA) guideline, little information relevant to clinical epidemiology, especially microbiological characteristics, is available. This study aimed to reveal microbiological characteristics and clinical outcomes of HDAP and to assess whether HDAP should be included in the HCAP category. We retrospectively analyzed 69 HDAP patients [42 with moderate and 27 with severe disease based on A-DROP (age, dehydration, respiratory failure, orientation disturbance, and low blood pressure)] in whom sputum cultures were performed at our hospital between 2007 and 2009. The most common pathogens were Staphylococcus aureus (37.7%), which were composed of methicillin-resistant S. aureus (MRSA) (27.5%) and methicillin-sensitive S. aureus (MSSA) (10.1%), followed by Streptococcus pneumoniae (10.1%), Klebsiella pneumoniae (8.7%), Haemophilus influenzae (7.2%), and Moraxella catarrhalis (5.8%). This distribution mostly resembled the microbiological characteristics of HCAP reported previously, except that the frequency of multi-drug-resistant (MDR) gram negatives such as Pseudomonas aeruginosa (2.9%) was clearly lower and that of MRSA was higher. There were no significant differences in microbiological findings, including the incidence of MDR pathogens, between the two severity groups. Despite most cases (82.6%) receiving only monotherapy, the prognosis (30-day survival and in-hospital mortality rates were 88.4% and, 17.4%, respectively) was similar to the past HCAP reports, but there were no significant correlations between prognosis and presence of MDR pathogens (30-day mortality rates 18.2% in MDR positive vs. 8.5% in MDR negative; p = 0.242). Assessment for not only MDR pathogens, but also severity of illness by the A-DROP system made it possible to conduct stratification based on prognosis. Our results suggest that HDAP should be included in the HCAP category, while understanding that there are some differences.