Clostridioides (Clostridium) difficile colonization is very common among infants but the serological sequelae of infant C. difficile colonization are poorly understood, according to researchers. But a new prospective cohort study of healthy infants indicates TCD colonization was associated with a humoral immune response against toxins A and B, with evidence of toxin B neutralization in vitro.
Stools were serially collected among babies between 1 to 2 months and 9 to 12 months old and tested for non-toxigenic and toxigenic C. difficile (TCD). Cultured isolates underwent whole genome sequencing. Serum collected at 9 to 12 months old underwent measurement of IgA, IgG, and IgM against TCD toxins A and B and neutralizing antibody (NAb) titers against toxin B. For comparison, anti-toxin IgG and NAb were measured in cord blood from 50 mothers unrelated to study infants.
Among 32 infants, 16 (50%) were colonized with TCD; 12 were first colonized >1 month prior to serology measurements. A variety of sequence types were identified, and there was evidence of putative in-home (enrolled siblings) and outpatient clinic transmission.
Infants first colonized with TCD >1 month prior had significantly greater serum anti-toxin IgA and IgG against toxins A and B compared to non-TCD-colonized infants, and greater IgG compared to unrelated cord blood.
Five of 12 (42%) colonized infants had detectable NAb titers compared to zero non-TCD-colonized infants. Breastfeeding was not associated with differences in serological measurements.
The extent and duration of protection against CDI later in life afforded by natural C. difficile immunization events requires further investigation.
