Solid-phase enrichment uncovers a hidden Salmonella transmission chain in a recurrent pediatric household cluster: a case report.

OBJECTIVES

To describe a household cluster of recurrent pediatric non-typhoidal Salmonella (NTS) infection and compare the yield of conventional culture, solid-phase enrichment, and shotgun metagenomic sequencing across symptomatic children and household contacts.

METHODS

Longitudinal fecal specimens from a 4-year-old boy (Mo) with three discrete NTS episodes in 2 months, his monozygotic twin (TB), and three adult co-residents were processed by conventional culture; specimens from Episode 2 onwards and all contact specimens additionally received solid-phase enrichment, and a subset shotgun metagenomics. Isolates were characterized by VITEK 2, XbaI-PFGE, and whole-genome sequencing.

RESULTS

None of Mo's episodes met sepsis criteria (peak WBC 12.52 × 10?/L, CRP 5.46 mg/L, PCT 1.14 ng/mL); TB had one self-limited episode, both parents had brief symptomatic periods, and the grandmother was asymptomatic. Conventional culture was positive only at Mo's first episode, whereas solid-phase enrichment recovered Salmonella from three culture-negative pediatric acute-phase specimens (Mo 4.12, TB 4.16, Mo 5.1). Adult contacts were negative by both culture-based methods, but metagenomic sequencing detected Salmonella reads in all three. Mo_0412 and TB_0416 were S. enterica serovar Enteritidis ST11, with identical cgMLST, 99.9966% ANI, and 97% PFGE similarity, indicating a clonal household source. Mo received antibiotics across four classes during his recurrences, vs. two sequential agents in TB.

CONCLUSION

Conventional culture, solid-phase enrichment, and metagenomic sequencing functioned as complementary modalities, each recovering Salmonella the others missed, supporting a tiered diagnostic strategy for household NTS investigation. Cumulative antibiotic exposure may have contributed to Mo's differential susceptibility, a hypothesis warranting prospective study.