Short course antibiotic therapy for Gram-negative hospital-acquired pneumonia in the critically ill

Hospital-acquired pneumonia (HAP) is a common cause of morbidity and mortality in the critically ill, yet the optimal duration of antibiotic therapy is unknown. Too short a course may lead to treatment failure, whereas too long a course may lead to increased antibiotic resistance, antibiotic-related morbidity and increased costs. Standard duration of antibiotic therapy for Gram-negative (GN-)HAP at our institution is 5 days, significantly shorter than advocated in many current guidelines. We performed a retrospective review of all cases of GN-HAP on our critical care unit fulfilling clinical and microbiological criteria to investigate recurrence rate and mortality following short course antibiotic therapy. Seventy-nine eligible patients with GN-HAP were identified. Of these, 79% were receiving mechanical respiratory support at diagnosis; 42% had GN-HAP due to non-fermenting Gram-negative bacilli (NF-GNB) and 72% were treated with the recommended 5 day course of antibiotics. Two patients had clear evidence of non-resolution of pneumonia after 5 days of therapy. Overall recurrence rate was 14%, with relapse rates significantly higher among patients with NF-GNB when compared to patients with other Gram-negative organisms (17% vs 2%; P=0.03). The overall recurrence rate was no higher than rates reported in earlier studies (17-41%). Critical care mortality (34.2%) was also not in excess of previously reported values (18-57%). In this limited study, use of a 5 day course of appropriate antibiotics for GN-HAP does not appear to increase risk of recurrence or mortality when pneumonia resolution has been achieved prior to the cessation of therapy.