克罗诺杆菌环境耐受性的评价

Evaluation of Environmental Resistance of Cronobacter spp.

婴儿配方奶粉(powdered infant formulas,PIF)是克罗诺杆菌(Cronobacter spp.)的主要污染来源,其原辅料的添加和加工环境是最为主要的传播途径。为彻底有效地对克罗诺杆菌进行预防和控制,保障乳制品的安全,本实验以8株分离自PIF及其加工环境中的克罗诺杆菌为研究对象,对其耐热性、耐酸碱性、耐干燥性及耐高渗性进行研究,分析不同菌株环境耐受性之间的差异。结果表明:8株克罗诺杆菌对热的耐受性存在差异性,其中分离自终产品的菌株耐热性相对较强;克罗诺杆菌普遍具有耐酸不耐碱的特性,在pH为1.5的酸性条件下,所有菌株在处理30 s后仍可存活;克罗诺杆菌具有较强的抗干燥能力,在室温条件下,空气相对湿度为20.7%的条件下,所有菌株在7个月的试验过程中菌数均从初始浓度10^(8)CFU/mL下降到105 CFU/mL,这种缓慢的下降趋势说明克罗诺杆菌具有很强的抵抗干燥环境的能力;克罗诺杆菌具有较强的耐高渗性,当NaCl的浓度大于8%时,所有菌株生长缓慢,且在等渗条件下,克罗诺杆菌对山梨醇的耐受性强于NaCl。

Powdered infant formula(PIF)is the main source of Cronobacter spp.contamination,among which the addition of raw and auxiliary materials and the processing environment are the most important routes of transmission.In order to effectively prevent and control Cronobacter spp.to ensure the safety of dairy products,eight strains of Cronobacter spp.isolated from PIF and its processing environment were used as the research objects.Their heat resistance,acid and alkali resistance,dryness resistance and permeability resistance were studied,and the differences of environmental resistance of different strains were analyzed.The results showed that Cronobacter spp.had different heat resistance.The strains isolated from the end products had relatively stronger heat resistance.Cronobacter spp.generally had the characteristics of acid resistance but not alkali resistance.Under the acidic conditions at pH1.5,all strains could still survive being treated for 30 s.Cronobacter spp.had strong resistance to desiccation.The bacterial count of all strains decreased from an initial concentration of 10^(8) CFU/mL to 105 CFU/mL over the course of the 7-month test at room temperature with a relative air humidity of 20.7%.The slow decreasing trend indicated that Cronobacter spp.had a strong ability to resist dry environment.Cronobacter spp.had a strong resistance to osmosis.We found that all strains grew slowly when the concentration of NaCl was over 8%and the tolerance of Cronobacter spp.to sorbitol was stronger than that to NaCl under isotonic conditions.