We present ten patients with Rickettsia typhi infection in whom next-generation sequencing of microbial cell-free DNA (mcfDNA) was used as a diagnostic tool. Rickettsia typhi mcfDNA was detected in all cases and was more rapid and specific than rickettsial serology. Rickettsia typhi mcfDNA impacted antibiotic management in 50% of patients.
Flea-borne (murine) typhus is caused by Rickettsia typhi. Infection in pregnant women can lead to adverse outcomes when diagnosis and treatment is delayed. We describe how next-generation sequencing (NGS) using the Karius® test was used to rapidly diagnose murine typhus in two pregnant women admitted to a large tertiary care center in Houston, Texas, when all initial testing was nondiagnostic.
Background
Long regarded as the second most common cause of community-acquired pneumonia (CAP), Haemophilus influenzae has recently been identified with almost equal frequency as pneumococcus in patients hospitalized for CAP. The literature lacks a detailed description of the presentation, clinical features, laboratory and radiologic findings, and outcomes in Haemophilus pneumonia.
Methods
During 2 prospective studies of patients hospitalized for CAP, we identified 33 patients with Haemophilus pneumonia. In order to provide context, we compared clinical findings in these patients with findings in 36 patients with pneumococcal pneumonia identified during the same period. We included and analyzed separately data from patients with viral coinfection. Patients with coinfection by other bacteria were excluded.
Results
Haemophilus pneumonia occurred in older adults who had underlying chronic lung disease, cardiac conditions, and alcohol use disorder, the same population at risk for pneumococcal pneumonia. However, in contrast to pneumococcal pneumonia, patients with Haemophilus pneumonia had less severe infection as shown by absence of septic shock on admission, less confusion, fewer cases of leukopenia or extreme leukocytosis, and no deaths at 30 days. Viral coinfection greatly increased the severity of Haemophilus, but not pneumococcal pneumonia.
Conclusions
We present the first thorough description of Haemophilus pneumonia, show that it is less severe than pneumococcal pneumonia, and document that viral coinfection greatly increases its severity. These distinctions are lost when the label CAP is liberally applied to all patients who come to the hospital from the community for pneumonia.
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