Outcomes for patients with bacteremic Streptococcus pneumoniae were significantly worse than those for patients with Legionnaire’s disease (LD) based on data from 106 individuals.
Reported cases of LD in the United States have increased in recent decades, but they are likely underreported, wrote Sima Salahie, MD, of Wayne State University School of Medicine, Detroit, Michigan, and Central Michigan University College of Medicine, Grosse Pointe Woods, Michigan, and colleagues.
Clinical presentations may be similar for both conditions, but different antimicrobial therapies are needed; therefore, identifying distinguishing factors can promote better management of hospitalized patients, they reported.
In a retrospective case companion study published in the American Journal of the Medical Sciences, the researchers reviewed data from 51 adults with LD and 55 with bacteremic S. pneumoniae pneumonia (SP) who were hospitalized at a single center between 2013 and 2018. Diagnoses were confirmed by laboratory and radiology results. In addition, data were collected on clinical features including body mass index, systolic and diastolic blood pressure, pulse, respiratory rate, and temperature.
Overall, patients with SP were significantly more likely than those with LD to require mechanical ventilation (P =.04), intensive care unit stay (P =.004), and die (P =.002). Patients with SP also had higher rates of septic shock compared to LD patients, although this difference fell short of statistical significance (49.1% vs 30.4%; P =.06).
In a multivariate analysis, male sex, diarrhea, higher body mass index, hyponatremia, and lower Charleston Weighted Index of Comorbidity (CWIC) score were significant independent predictors of LD, with odds ratios of 21.6, 4.5, 1.13, 5.6, and 0.61, respectively.
The incidence of LD peaked in summer, while the incidence of SP peaked in the winter, the researchers noted. “Seasonality is a variable that has not always been included in previous scoring systems but should be considered in future modeling,” they said.
“Noteworthy is that LD represented almost as many cases as documented bacteremic pneumococcal pneumonia,” the researchers wrote in their discussion. “This occurred at a time when there was no outbreak of L. pneumophila in our community and as these were all community acquired there was no evidence of a nosocomial outbreak in our institution,” they said.
The study findings were limited by several factors including the possible underestimation of SP because of the requirement for positive blood cultures, and the lack of other methods of diagnosing SP, the researchers noted.
“However, the data suggest variables to distinguish LD from SP, they said. Establishing reliable clinical and laboratory parameters embedded in a simple diagnostic score that can accurately identify patients with LD may be helpful in aiding physicians’ early diagnosis in distinguishing LD from SP but will need to be defined,” they concluded.
The study received no outside funding. The researchers disclose no financial conflicts.
American Journal of the Medical Sciences. March 10, 2022. Abstract.
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