奶粉中阪崎克罗诺杆菌耐干燥性与MLST分型的研究

Study on Desiccation Tolerance and MLST of Cronobacter sakazakii in Milk Powder

为了解奶粉中阪崎克罗诺杆菌耐干燥性及多位点序列分型(multilocus sequence typing,MLST)间的关系,对实验室保存的35株阪崎克罗诺杆菌进行干燥试验,并采用MLST对所有菌株进行分子遗传学分析。经过6 d干燥试验处理,结果显示,35株阪崎克罗诺杆菌中,耐干燥能力较强的IQCC10409(1号)、IQCC10455(6号)和110609-3(31号)菌株失活率分别为63.73 %、56.94 %和44.43 %,其中31号菌株耐干燥能力最强,它们分别属于ST73、ST73和ST23型。MLST分析表明,全部菌株共分成16个不同的序列型(sequence type,ST),其中,属于ST1型(20号、24号、27号、28号、33号)和ST4型(4号、6号、7号、9号、11号)的菌株较多,分别有5株菌。结果表明阪崎克罗诺杆菌基因多样性程度较高,而耐干燥性较强的菌株主要集中于ST73和ST4型,另外还发现,即使相同ST型的菌株,其耐干燥能力也不定相同。

In order to understand the relationship between desiccation tolerance and multi locus sequence typing (MLST) of food-borne Cronobacter sakazakii in milk powder, a total of 35 C. sakazakii isolated were collected to detect desiccation tolerance. Molecular genetic analysis of all strains were analyzed by multilocus sequence typing. After 6 days of desiccation treatment, the results showed that among the 35 strains of C. sakazakii IQCC10409 (No. 1), IQCC10455 (No. 6) and 110609-3 (No. 31) with strong desiccation tolerance,which belonged to ST73,ST73 and ST23, respectively. And the inactivation rates of strains No. 1, No. 6 and No. 31 were 63.73 %, 56.94 % and 44.43 %, indicating that No. 31 had the strongest resistance to desiccation. MLST analysis showed that all strains were divided into 16 different sequence types, among which ST1 type (including the strains of No. 20, 24, 27, 28, 33) and ST4 type (including the strains of No. 4, 6, 7, 9 ,11) were the most dominant STs which both contained five C. sakazakii isolates. A great genetic diversity of poultry isolates was found in C. sakazakii. The strains with strong desiccation tolerance are mainly concentrated in the ST73 and ST4 type, and it was also found that even the same ST strains had the different desiccation tolerance.