Severe asthma patient with secondary Citrobacter koseri abdominal infection: first case report and review of the literature.

Citrobacter koseri (C. koseri) is a Gram-negative, motile, non-spore-forming facultative anaerobic bacillus belonging to the Enterobacteriaceae family. C. koseri typically utilizes citrate as the sole carbon source and constitutes part of the normal gastrointestinal flora in humans and animals. As an opportunistic pathogen, C. koseri infections are mainly observed in neonates, elderly individuals, and immunocompromised hosts. C. koseri has been one of the main etiological agents of neonatal meningitis and cerebral abscess. In recent years, an increasing number of cases have been reported in adults with severe infections caused by C. koseri. Here, we report for the first time a clinical case of concurrent C. koseri intra-abdominal infection in a patient with severe asthma and provide a brief review of the relevant literature. With this report, we hope to increase awareness and alertness among clinicians to the possibility of concurrent infection of gut commensal bacteria in asthmatic patients requiring long-term oral corticosteroid administration.