Presence of Soil-Dwelling Clostridia in Commercial Powdered Infant Formulas

Abstract

Because Clostridium botulinum was isolated from powdered infant formula (PIF) fed to an infant in the United Kingdom who subsequently developed infant botulism and from unopened PIF from the same manufacturer, we tested PIF manufactured in the United States for the presence of clostridial spores. Thirty PIF ingested by 19 California infants with botulism within 4 weeks of onset of illness (48% of all patients fed PIF during study) in 2006-2007 were cultured anaerobically to isolate clostridia. All isolated clostridia were identified to the species level and enumerated with standard microbiologic and molecular methods. Five of 30 (17%) PIF samples ingested by patients contained clostridial spores. Spores were also found in 7 of 9 (78%) market-purchased PIF samples. Clostridium sporogenes was isolated most frequently, followed by Clostridium butyricum and at least 10 other soil-dwelling clostridial species. No neurotoxigenic clostridia were isolated. The most probable number of clostridial spores in PIF ranged between 1.1 to >23 per 100 g. With the notable exception of production of botulinum neurotoxin, C sporogenes is physiologically comparable with proteolytic strains of C botulinum, and both share the same natural reservoir (soils and dust worldwide). The isolation of C sporogenes and potentially pathogenic clostridia from U.S.-manufactured PIF suggests that neurotoxigenic clostridial spores have the potential to be present in these products.