Bacillus Cereus prevalence in human milk donations in a North Italy human milk bank

• Published in: European journal of public health Vol. 33; no. Supplement_2
• Main Authors: Abdul, M E, Magagna, G, Todeschi, S, Finazzi, G, Filipello, V, Rossi, F, Risso, F M, Pezzotti, E, Dioni, E, Losio, M N
• Format: Journal Article
• Language: English
• Published: Oxford University Press 24.10.2023
• Subjects: Poster Walks
• ISSN: 1101-1262; 1464-360X
• DOI: 10.1093/eurpub/ckad160.942

Abstract Background The importance of human milk in infants’ diets is well-known in the medical community. Unfortunately, breastfeeding isn't always possible for various reasons, human milk donation represents the main solution to this problem. The donated milk goes through a pasteurization treatment (62.5 °C for 30 minutes). Before consumption, the milk is tested to analyze the microbiological safety aspect, specifically: the protocol of a North Italian bank, provides for the total count of microorganisms and of Bacillus Cereus. The presence of B. Cereus in pasteurized milk samples has been witnessed in the last few years. B. Cereus infections in infants have consistently been reported and banked human milk could be one of the possible sources. This work aims to study the prevalence of B. Cereus in banked human milk sampled before and after pasteurization treatment. Methods Between 2020 and 2023 we tested 1055 samples, before and after the pasteurization treatment. The enumeration of B. cereus is performed in accordance with ISO 7932:2004. 100 µL of pure raw milk and two consecutive decimal dilutions in buffered peptone water were seeded on Bacillus cereus Agar (BCA) at 30° for 24h-48h. B. Cereus strains isolated were typed using the hemolysis test and BCA. Results We found 46 samples positives for B. Cereus from 1055 samples analyzed before the heat treatment. The number increased to 57 in the pasteurized samples. These data are confirmed by the typing of the isolated strains from the human milk. Conclusions The 4% of not pasteurized milk is discarded due to B. Cereus presence, and the rate increase to 5% in pasteurized milk. This information suggests that the heat treatment isn't capable to inhibit all the B. Cereus, and the increase of B. Cereus from not pasteurized to pasteurized need to be studied. Key messages • B. Cereus represents one of the main causes of noncompliance in banked human milk. • Implementation of preventive/corrective actions is needed to prevent the contaminations led by the operators.