Epidemiology and microbiology of severe community-acquired pneumonia in Central Australia: a retrospective study

Background: Severe community-acquired pneumonia (SCAP) has high mortality and morbidity. Aims: To describe the epidemiology and microbiology of SCAP in Central Australia. Methods: A retrospective epidemiological study describing the characteristics, incidence rates (IR) and microbiological aetiology of SCAP in Central Australia. Adult patients admitted to Alice Springs Hospital Intensive Care Unit (ICU) between 2011 and 2014 that fitted the Infectious Diseases Society of America and American Thoracic Society definition of SCAP were included. Medical records were reviewed and compared between indigenous and non-indigenous patients. Primary outcomes were incidence rate and microbiological aetiology of SCAP. Secondary outcomes were 30-day mortality, and ICU and hospital length of stay (LoS). Results: A total of 185 patents were included (156 indigenous; 29 non-indigenous). The overall SCAP IR per 1000 person-years was 3.24 (3.75 indigenous; 1.87 non-indigenous) with an IR difference of 2.71 after adjustment (P < 0.001). Those aged ≥50 years had an IR 74.8% higher than those younger. Male IR was 50% higher than females. There was a significant difference between indigenous and non-indigenous groups for age (48 vs 64 years), but not for 30-day mortality (7.7% vs 10.3%), ICU LoS (4.8 vs 4.6 days) and hospital LoS (10.9 vs 15.1 days) respectively. Likely causative pathogen(s) were identified in 117 patients; Streptococcus pneumoniae was the most common pathogen (28.2%), followed by Haemophilus influenzae (19.7%), Influenza A/B (16.2%) and Staphylococcus aureus (14.5%). Conclusion: A high incidence of SCAP was observed in Central Australia, disproportionately affecting the indigenous population. Prevention strategies are imperative, as well as early identification of SCAP and appropriate empiric antibiotic regimens.