Molecular epidemiology and virulence markers of Salmonella Infantis isolated over 25years in São Paulo State, Brazil

Abstract

Infection of humans and animals caused by Salmonella is a major public health problem worldwide. Among the more than 2500 serovars, S. Infantis has been one of the 15 most isolated serovars in the world. Despite its clinical importance, little is known about the molecular characteristics of S. Infantis strains from Brazil. The aims of this study were to type S. Infantis isolates of this country and to assess their pathogenic potential. The molecular epidemiology of 35 S. Infantis strains, isolated from human sources (25) and food items (10) between 1984 and 2009 in São Paulo State, Brazil, were investigated using ERIC-PCR, PFGE and MLST. Furthermore, the presence of some virulence markers from Salmonella pathogenicity islands (SPIs) SPI-1 and SPI-2 and from the virulence plasmid was assessed by PCR. Using ERIC-PCR, 34 S. Infantis strains exhibited a high genetic similarity (≥ 93.7%) and using PFGE, 32 strains exhibited a similarity ≥ 80.6%. Additionally, MLST showed a high clonal similarity among strains that all presented the same ST32. Thirty-two isolates under investigation contained the virulence markers invA, sopB, sopD, sipA, sipD, ssaR, sifA, flgK, fljB and flgL. In conclusion, the S. Infantis strains studied were genetically similar, suggesting that a prevalent subtype has been causing disease and food contamination during a 25year period in São Paulo State, an important metropolitan region in Brazil. Furthermore, the contamination between strains from food items and sick humans indicates that better control measures for S. Infantis may be needed in this country.

Antibiotic Resistance and Molecular Studies on Salmonella Enterica Subspecies Enterica Serovar Infantis Isolated in Human Cases and Broiler Carcasses

“…A similar study was conducted in Brazil, where in 35 isolates of S. Infantis derived from patients suffering from food poisoning, during the period from 1984 to 2009 a degree of similarity of ≥ 80.6% was determined, as well as 23 PFGE profi les [23].…”

Genotypic diversity, pathogenic potential and the resistance profile of Salmonella Typhimurium strains isolated from humans and food from 1983 to 2013 in Brazil

“…A template PCR without DNA was used as a negative control and S. Typhimurium ATCC 13311 was used as a positive control. Analyses of the amplicons were performed as described previously by Almeida et al (2013). The results were obtained after incubating the strains for 24 h at 37 uC and were interpreted according to CLSI (2014).…”

“…The final extension was at 72 uC for 2 min. The analysis was performed as described by Almeida et al (2013).…”

“…Salmonella pathogenicity is largely related to gene markers of virulence presented mainly in Salmonella pathogenicity island (SPI) 1, SPI-2 and plasmids (Campioni et al, 2012;Almeida et al, 2013). The SPI-1-associated proteins include the following: Sop (SopA-E), effector proteins; SipA and InvA, associated with invasion; SipD, a translocon assembly protein; and FlgK, FljB and FlgL proteins, associated with flagella.…”

“…Molecular typing is an important tool for bacterial characterization and can help us better understand their epidemiology and genotypic diversity. Various molecular typing techniques have been used successfully for subtyping Salmonella serovars such as enterobacterial repetitive intergenic consensus PCR (ERIC-PCR), PFGE, multiple-locus variable number of tandem repeats analysis (MLVA) and multilocus sequence typing, among others (Hur et al, 2011;Campioni et al, 2012Campioni et al, , 2013Campioni et al, , 2014Almeida et al, 2013;Ngoi et al, 2013).…”