Multilocus sequence typing analysis of Cronobacter spp. isolated from China.

Multilocus sequence typing (MLST) has proven to be an effective approach for the subtyping isolates of the Cronobacter genus and to exhibit a high level of discrimination between isolates. In this study, 151 Cronobacter strains were isolated from different sources and provinces across China from 2010 to 2012 and analyzed by MLST. Their sequence type profiles were compared with strains from other countries which were widely geographically and temporally distributed. Out of 151 strains in this study, the majority of strains were Cronobacter sakazakii (70.9 %), C. malonaticus (15.9 %), C. dublinensis (10.6 %), C. turicensis (2.0 %), and C. muytjensii (0.7 %). The strains were divided into 85 sequence types (STs), among which only 17 had previously been reported in other countries. The 85 identified STs for the Cronobacter genus were grouped into 14 clonal complexes and 47 singletons according to eBURST algorithm. The Cronobacter isolated from China showed a high diversity when they were subtyped using the MLST method. When compared to the Cronobacter PubMLST database, some sequence types of strains cultured from food and/or water in this study were also the same with strains isolated from patients in other countries as reported previously. This result showed the potential hazard of strains contaminating water and weaning food from China.

[The pathogenic ecology research on plague in Qinghai plateau].

OBJECTIVE: To study the pathogenic ecology characteristics of plague in Qinghai plateau. METHODS: Applied molecular biology techniques, conventional technologies and geographic information system (GIS) to study phenotypic traits, plasmid spectrum, genotype, infected host and media spectrum etc.of 952 Yersinia pestis strains in Qinghai plateau plague foci, which were separated from different host and media in different regions during 1954 to 2012. RESULTS: The ecotypes of these strains were Qingzang plateau (91.49%, 871/952),Qilian mountain (6.41%, 61/952) and Microtus fuscus (1.26%, 12/952).83.6% (796/952) of these strains contained all the 4 virulence factors (Fr1, Pesticin1,Virulence antigen, and Pigmentation), 93.26% (367/392) were velogenic strains confirmed by virulence test.725 Yersinia pestis strains were separated from Qinghai plateau plague foci carried 9 kinds of plasmid, among which 713 strains from Marmot himalayan plague foci carried 9 kinds of plasmid, the Mr were 6×10(6), 7×10(6), 23×10(6), 27×10(6), 30×10(6), 45×10(6), 52×10(6), 65×10(6) and 92×10(6) respectively. 12 Yersinia pestis strains were separated from Microtus fuscus plague foci carried only 3 kinds of plasmid, the Mr were 6×10(6), 45×10(6), 65×10(6). Meanwhile, the strains carrying large plasmid (52×10(6), 65×10(6) and 92×10(6)) were only distributed in particular geographical location, which had the category property. The research also confirmed that 841 Yersinia pestis strains from two kinds of plague foci in Qinghai plateau had 11 genomovars. The strains of Marmot himalayan plague foci were given priority to genomovar 5 and 8, amounted to 611 strains, genomovar 8 accounted for 56.00% (471/841), genomovar 5 accounted for 23.07% (194/841). Besides, 3 new genomovars, including new 1(62 strains), new 2(52 strains), new 3(48 strains) were newly founded, and 12 strains of Microtus fuscus plague foci were genomovar 14. CONCLUSION: The main host and media of Qinghai plateau plague foci directly affected the spatial distribution regularities of plague epidemic and the pathogens characteristics, meanwhile the polymorphism of plague ecological geographic landscape leds to the complexity of Yersinia pestis' genotype.

[Study on the pathogen of plague in Sanjiangyuan area in Qinghai province].

OBJECTIVE: To study the biological characteristics of Yersinia pestis and to develop prevention and control program on plague in Sanjiangyuan areas, Qinghai province. METHODS: To identify the biologic types and molecular biological features of Y.pestis isolated in Sanjiangyuan area from 1954-2007. RESULTS: Among the 411 strains of Y. pestis, 12 strains belonged to the microtus type Y. pestis with denitrification (-) and donkey-hide gelatin carbohydrate (-) and glycerine (+). 399 strains belonged to classic type Y. pestis with denitrification (+) and donkey-hide gelatin carbohydrate (+) and glycerine (+). 411 Y. pestis strains had factor F I and Pst I. Among them, VW+ strains of Y. pestis accounted for 95.13% (391/411), VW-accounted for 4.87% (20/411), Pgm(+) accounted for 80.78% (332/ 411), Pgm(+/-) accounted for 9% (37/411) and Pgm(-) accounted for 10.22% (42/411) respectively. 96.82% (213/220) of the Y. pestis strains showed strong virulence to laboratory mice while 3.18% (7/220) of the strains carried medium virulence. 90.02% of the tested Y. pestis (370/411) strains had 6 x10(6), 45 x 10(6), 65 x 10(6) plasmids. 8 types of genome were found among 80 strains of Y. pestis, with 6 of them resembling ZHOU Dongsheng' s classification. Two new genome types were found. CONCLUSION: The Y. pestis in the Sanjiangyuan area had the characteristics of plague pathogen, identified in Qinghai-Tibet plateau. It is estimated that human beings are highly susceptible to the disease which spread fast, causing serious signs and symptoms with high death rate.