Diversity of Salmonella spp. serovars isolated from the intestines of water buffalo calves with gastroenteritis

Abstract

BackgroundSalmonellosis in water buffalo (Bubalus bubalis) calves is a widespread disease characterized by severe gastrointestinal lesions, profuse diarrhea and severe dehydration, occasionally exhibiting a systemic course. Several Salmonella serovars seem to be able to infect water buffalo, but Salmonella isolates collected from this animal species have been poorly characterized. In the present study, the prevalence of Salmonella spp. in water buffalo calves affected by lethal gastroenteritis was assessed, and a polyphasic characterization of isolated strains of S. Typhimurium was performed.ResultsThe microbiological analysis of the intestinal contents obtained from 248 water buffalo calves affected by lethal gastroenteritis exhibited a significant prevalence of Salmonella spp. (25%), characterized by different serovars, most frequently Typhimurium (21%), Muenster (11%), and Give (11%). The 13 S. Typhimurium isolates were all associated with enterocolitis characterized by severe damage of the intestine, and only sporadically isolated with another possible causative agent responsible for gastroenteritis, such as Cryptosporidium spp., Rotavirus or Clostridium perfringens. Other Salmonella isolates were mostly isolated from minor intestinal lesions, and often (78% of cases) isolated with other microorganisms, mainly toxinogenic Escherichia coli (35%), Cryptosporidium spp. (20%) and Rotavirus (10%). The S. Typhimurium strains were characterized by phage typing and further genotyped by polymerase chain reaction (PCR) detection of 24 virulence genes. The isolates exhibited nine different phage types and 10 different genetic profiles. Three monophasic S. Typhimurium (B:4,12:i:-) isolates were also found and characterized, displaying three different phage types and three different virulotypes. The molecular characterization was extended to the 7 S. Muenster and 7 S. Give isolates collected, indicating the existence of different virulotypes also within these serovars. Three representative strains of S. Typhimurium were tested in vivo in a mouse model of mixed infection. The most pathogenic strain was characterized by a high number of virulence factors and the presence of the locus agfA, coding for a thin aggregative fimbria.ConclusionsThese results provide evidence that Salmonella is frequently associated with gastroenteritis in water buffalo calves, particularly S. Typhimurium. Moreover, the variety in the number and distribution of different virulence markers among the collected S. Typhimurium strains suggests that within this serovar there are different pathotypes potentially responsible for different clinical syndromes.

Prevalence and Fimbrial Genotype Distribution of Poultry Salmonella Isolates in China (2006 to 2012)

“…Our study of the distribution of various fimbrial genes in Salmonella serovars from poultry in China has shown that over 70% of the isolates possessed the bcfD, csgA, fimA, stdB, sthE, stbD, lpfD, stfH, stiH, safC, and steB genes, which is consistent with previous studies (10,34) and provides further evidence that these fimbrial genes are widely distributed among S. enterica. We found lower prevalences of tcfA, stkA, pefA, sefA, pegD, stcA, and stjA (11.8 to 55.7%) and no evidence of staA and stgA, two genes which were once reported in S. Pullorum from poultry, suggesting that some fimbrial genes might be serovar specific (10,12).…”

Antimicrobial susceptibility, virulence gene profiles and molecular subtypes of Salmonella Newport isolated from humans and other sources

“…In agreement with other studies, substantial variability was observed in the occurrence of phage genes among the 79 Salmonella isolates in our study (Borriello et al, 2012;Drahovska et al, 2007). The acquisition and the loss of prophage-associated…”

“…The ability of nontyphoidal Salmonella to cause invasive disease is attributed to arrays of virulence genes defined in the Salmonella pathogenicity islands (SPIs). The avrA, ssaQ, mgtC, siiD, and sopB genes are genetic markers for the presence of the SPI 1-5 in Salmonella, although their presence does not necessarily implicate the presence of the entire SPI (Borriello et al, 2012). In our study, except one isolate was negative for mgtC, siiD and sopB, and four isolates for sopB, the remaining isolates all harbored the five SPI genes, indicating that these virulence genes are widespread and highly conserved among Salmonella as previously reported (Graziani et al, 2011;Huehn et al, 2010).…”

“…Salmonella virulence factors, frequently located on Salmonella pathogenicity islands (SPIs), prophage regions and/or virulence plasmids, play a key role in the pathogenesis of Salmonella gastroenteritis (Borriello et al, 2012). The application of virulence gene identification in Salmonella typing offers a better prediction of disease-causing capacity (Graziani et al, 2011;Huehn et al, 2010).…”

Antimicrobial resistance, virulence genes and molecular subtypes of S. Enteritidis isolated from children in Shanghai

“…The plasmid-associated gene spvC is often detected in S. Enteritidis and a few other Salmonella serovars; it was found in more than 80% of the isolates we tested [27]. The avrA, ssaQ, mgtC, siiD, and sopB genes were highly conserved and were genetic markers for the presence of the SPI 1-5 in Salmonella [28]. The high percentage of these virulence genes in our study also indicated that they were widespread and highly conserved.…”