In previous uncontrolled studies, acinetobacter baumannii appears to be a rare but important cause of community acquired pneumonia (CAP-AB), that may run a fulminant course. We performed a retrospective study of CAP-AB to characterize its clinical course and outcome, by comparing it with a control group of patients with hospital acquired pneumonia caused by acinetobacter baumannii (HAP-AB).
This is a retrospective case-control study comparing CAP-AB with HAP-AB between July 2000 and December 2003. Clinical, laboratory, radiological and microbiological data were analyzed.
There were 19 cases of CAP-AB (16 male and 3 female, mean age 72.6 ± 9.6 years) and 74 cases of HAP-AB during the 42-month study period. When compared to HAP-AB group, CAP-AB group has more ever smokers (84.3% vs. 55.4%, p = 0.031), more patients with COPD (63.2% vs. 29.7%, p = 0.014), and lower number of past hospitalization in the previous year (range: 0-0 vs. 0-6, p = 0.049). CAP-AB group had a higher prevalence of bacteremia (31.6% vs. 0%, p < 0.001). Strains causing HAP-AB were generally more resistant. There were higher frequencies of adult respiratory distress syndrome (ARDS) (84.2% vs. 17.6%, p < 0.001) and disseminated intravascular coagulation (DIC) (57.9% vs. 8.1%, p < 0.001) in the CAP-AB group. Moreover, the median survival was only 8 days in the CAP-AB group, versus 103 days in the HAP-AB (p=0.0026). Unexpectedly, early appropriate antibiotics in CAP-AB was not assoicated with better survival. Factors associated with higher mortality in the CAP-AB group included the presence of AB bacteremia (p = 0.040), platelet count < 120 x 10^9/L (p = 0.026), pH< 7.35 on presentation (p = 0.047) and presence of DIC (p = 0.004).
CAP-AB appears to be a distinct clinical entity with a high incidence of bacteremia, ARDS, DIC and death, when compared to HAP-AB. Early appropriate antibiotics in CAP-AB was not assoicated with better survival.
Further studies are needed to investigate the mechanism of the fulminant nature of CAP-AB.
Wah Leung, None.