Identification and characterization of an invasive, hyper-aerotolerant <i>Campylobacter jejuni</i> strain causing bacteremia in a pediatric leukemia patient
Ximin Zeng, K. C. Kent Lloyd, Rana F. Hamdy, Craig Shapiro, Mark Fisher, Jun Lin, Baoming Liu
Abstract
ABSTRACT Background Campylobacter jejuni is a leading pathogen causing gastroenteritis in humans. Invasive C. jejuni strains crossing the gut-blood barrier can cause bacteremia. Despite its microaerophilicity (preferring <5% O 2 atmosphere), hyper-aerotolerant (HAT) C. jejuni has recently been isolated from intestines in poultry and humans. Elevated aerotolerance may enhance C. jejuni survival in the ecosystem, thereby promoting its transmission. However, invasive HAT isolates of C. jejuni have not been reported in bacteremia in humans. Case Summary A C. jejuni strain (CNH-HAT-1) was isolated from a 7% CO 2 (~16% O 2 ) atmosphere subculture of an aerobic blood culture from a 5-year-old boy with B-cell acute lymphoblastic leukemia presenting with bloody stool, fever, and neutropenia. The organism identification was determined by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and 16S-rRNA sequencing. HAT phenotype of this isolate was confirmed by aerotolerance testing. Belonging to the ST-21 clonal complex, CNH-HAT-1 is phylogenetically close to recently reported invasive C. jejuni sheep abortion strains and some bacteremia-associated strains. CNH-HAT-1 possesses a CJIE-1 prophage element, a functional enterobactin receptor CfrB, and G250A mutation in the major outer-membrane protein PorA, which likely contributes to C. jejuni invasiveness. CNH-HAT-1 is resistant to penicillins/cephalosporins but susceptible to aminoglycosides, fluoroquinolones, and macrolides. The patient improved with intravenous gentamicin, followed by enteral therapy with azithromycin. Conclusion We identified a novel invasive bloodstream C. jejuni strain proven in vitro to be HAT, shedding light on key genomic features linking with its pathogenesis. Given its enhanced survival of HAT C. jejuni in ecosystem, a clinical microbiology lab should be vigilant with detecting them from blood cultures.