Molecular Tracing and Molecular Characteristics of Strains from <i>Campylobacter jejuni</i> Bacteremia in a 23-Day-Old Infant in China

<i>Campylobacter jejuni</i> (<i>C. jejuni</i>), a common foodborne zoonotic pathogen, usually causes gastroenteritis and rarely causes extraintestinal infections such as bacteremia. This study investigates a rare case of invasive <i>C. jejuni</i> bacteremia in a 23-day-old infant in Nanchang, China. Epidemiological data were collected from the infant's cohabitants (3). The cohabitants' anal swabs (3), milk powder (1), a feeding bottle (1), and kitchen items (3) were collected and screened for <i>C. jejuni</i>. Antimicrobial susceptibility testing was conducted, and whole genome sequencing was performed for genetic analysis, including whole genome multilocus sequence typing (wgMLST), single-nucleotide polymorphism, antimicrobial resistance (AMR) and virulence gene profiling. As a result, three <i>C. jejuni</i> strains were isolated from the infant, the infant's grandmother, and the feeding bottle. The results revealed that the three <i>C. jejuni</i> isolates were clonally related, sharing minimal genetic differences. The infant's grandmother, who had slaughtered a live chicken 4 days before the infant's illness, was identified as the likely source of transmission. AMR profiles showed resistance to fluoroquinolones and cephalosporins. The three isolates were found to carry the <i>blaOXA-184</i> gene and a chromosomal mutation in <i>gyrA</i> (T86I). Additionally, 69 virulence genes were identified in all isolates, including those associated with adherence (4), glycosylation system (23), motility and export apparatus (38), cytolethal toxin (3), and invasion (1). This case represents the third reported instance of <i>C. jejuni</i> bacteremia in an infant in China. The analysis confirmed a transmission pathway from the grandmother.