关键词:
Serratia marcescens
Infant formulae
Cross-contamination
Pathogens
Baby milk
摘要:
The application of good hygiene practices for the reconstitution of infant formulae, preparation and consumption of feeding bottles, according to manufacturer's instructions, is essential to ensure the microbiological safety and quality of feeding bottles. This study investigated the growth of Serratia marcescens, a bacterium widely present in home environments with the ability to cause pink coloration resulting from growth in intentionally contaminated reconstituted infant formulae, stored at 32 C (as a simulation of inappropriate storage in tropical regions). In addition, poor hygiene practices such as lack of bottle wash after use, inadequate bottle washing and heat sanitisation, or use of contaminated kitchen cloths to wipe dry sterilised baby bottles were investigated as leading causes of microbial contamination and transfer during preparation of feeding bottles. Infant formulae powders represent a negligible risk of S. marcescens contamination, because finished product specifications require absence of Enterobacteriaceae (EB), and all lots are tested for absence of EB before release. The results of the simulation of inadequate hygiene practices during preparation of feeding bottles showed that bottles or reconstituted milk can be readily contaminated with S. marcescens by using a dirty cloth. The resulting contamination level in prepared milk was as high as 4 log CFU/mL. A similar contamination level was associated with inappropriate bottle washing and sanitation. Poor hygiene practices leading to such contamination levels are undesirable even if the feeding bottles are consumed immediately. S. marcescens was able to initiate grow in artificially inoculated infant formulae (3.2 log CFU/ml) within 4 h (lag-phase) and reach levels of 6 and 8 log CFU/ml after 8 h and 12 h at 32 C respectively. A maximum growth rate of 0.42 11-1 was determined. The first sign of a distinctly pink discoloration was noticed at 32 C within 24 h when cell concentration was above 9 log