Prevalence and fimbrial genotype distribution of poultry Salmonella isolates in China (2006 to 2012)

Abstract

In this study, a total of 323 Salmonella enterica strains were isolated from 3,566 rectal swab samples of 51 poultry farms in seven regions of 12 provinces of China between 2006 and 2012. The prevalences of Salmonella sp. carriage were 12.4% in geese (66 positive/533 samples), 10.4% in turkeys (32/309), 9.8% in chickens (167/1,706), 6.8% in ducks (41/601), and 4.1% in pigeons (17/417), respectively. These isolates belonged to 20 serovars, in which the most frequent serovars were S. enterica serovar Gallinarum biovar Pullorum (herein, S. Pullorum) (55 isolates, 17.0%), S. enterica serovar Typhimurium (50 isolates, 15.5%), and S. enterica serovar Enteritidis (39 isolates, 12.1%). Overall, S. Typhimurium was the most commonly detected serovar; among the individual species, S. Pullorum was most commonly isolated from chickens, S. Enteritidis was most common in ducks, S. Typhimurium was most common in geese and pigeons, and S. enterica serovar Saintpaul was most common in turkeys. PCR determination of 20 fimbrial genes demonstrated the presence of bcfD, csgA, fimA, stdB, and sthE genes and the absence of staA and stgA genes in these isolates, and other loci were variably distributed, with frequency values ranging from 11.8 to 99.1%. These 323 Salmonella isolates were subdivided into 41 different fimbrial genotypes, and of these isolate, 285 strains (88.2%) had 12 to 14 fimbrial genes. Our findings indicated that the Salmonella isolates from different poultry species were phenotypically and genetically diverse and that some fimbrial genes are more frequently associated with serovars or serogroups.

FIG 1

Prevalence of poultry Salmonella isolation between 2006 and 2012. The prevalence of poultry Salmonella spp. from 3,566 rectal swabs did not differ significantly between the sampling times of 2006 (17.5%, 11/63), 2007 (8.6%, 36/417), 2008 (10.1, 71/703), 2009 (9.5%, 74/777), 2010 (7.0%, 55/791), 2011 (10.4%, 44/423), and 2012 (9.1%, 323/3,566).

FIG 2

Distribution of Salmonella fimbrial genes in 20 serovars investigated in this study. On the left, 20 Salmonella serotypes are ordered from top to bottom based on the number of fimbrial genes (8, 9, 10, 11, 12, 13, 14, or 15) in the Salmonella isolates. The top of this figure gives the names of 20 fimbrial genes investigated in this study. A filled box denotes the presence of the fimbrial gene, and an open box indicates the absence of the gene. Where space was insufficient to list all serovars, some were abbreviated, as indicated by an asterisk: Ko, Kottbus; Sa Saintpaul; Tm, Typhimurium; Ga, Gallinarum; En, Enteritidis, Pu, Pullorum; and Bl, Blockley.