Identification of genetic and phenotypic differences associated with prevalent and non-prevalent Salmonella Enteritidis phage types: analysis of variation in amino acid transport

Abstract

In this study, differences at the genetic level of 37 Salmonella Enteritidis strains from five phage types (PTs) were compared using comparative genomic hybridization (CGH) to assess differences between PTs. There were approximately 400 genes that differentiated prevalent (4, 6, 8 and 13a) and sporadic (11) PTs, of which 35 were unique to prevalent PTs, including six plasmid-borne genes, pefA, B, C, D, srgC and rck, and four chromosomal genes encoding putative amino acid transporters. Phenotype array studies also demonstrated that strains from prevalent PTs were less susceptible to urea stress and utilized L-histidine, L-glutamine, L-proline, L-aspartic acid, gly-asn and gly-gln more efficiently than PT11 strains. Complementation of a PT11 strain with the transporter genes from PT4 resulted in a significant increase in utilization of the amino acids and reduced susceptibility to urea stress. In epithelial cell association assays, PT11 strains were less invasive than other prevalent PTs. Most strains from prevalent PTs were better biofilm formers at 37 6C than at 28 6C, whilst the converse was true for PT11 strains. Collectively, the results indicate that genetic and corresponding phenotypic differences exist between strains of the prevalent PTs 4, 6, 8 and 13a and non-prevalent PT11 strains that are likely to provide a selective advantage for strains from the former PTs and could help them to enter the food chain and cause salmonellosis.

Cell invasion of poultry-associated Salmonella enterica serovar Enteritidis isolates is associated with pathogenicity, motility and proteins secreted by the type III secretion system

“…Fewer studies have been conducted to determine differences in invasiveness of field isolates of S. Enteritidis (Pan et al, 2009;Pang et al, 2006;Solano et al, 1998). Although these studies have shown that not all isolates of S. Enteritidis have similar cell invasive potential, only limited numbers of isolates recovered mostly from human, animal, food and the environment were tested.…”

“…Regardless of phage types, geographical origins or source of isolation, S. Enteritidis is one of the most genetically homogeneous serotypes of Salmonella and as a result is poorly discriminated by the commonly used genetic subtyping methods, such as phage typing, pulsed field gel electrophoresis or comparative genomic hybridization microarrays (Betancor et al, 2009;Botteldoorn et al, 2010;Hudson et al, 2001;Liebana et al, 2001;Malorny et al, 2008;Morales et al, 2005;Olsen et al, 1999;Pan et al, 2009;Pang et al, 2006;Porwollik et al, 2005;Saeed et al, 2006;Swaminathan et al, 2001). Because of its greater discriminatory capacity, MLVA was used to assess the genetic similarity among S. Enteritidis isolates tested in this study Cho et al, 2007;Malorny et al, 2008).…”

“…Enteritidis is the most genetically homogeneous serotype of Salmonella (Hudson et al, 2001;Liebana et al, 2001;Morales et al, 2005;Porwollik et al, 2005;Swaminathan et al, 2001). Despite limited genomic diversity, variation in phenotypic traits, including the ability to form biofilm, grow to high cell density, produce high-molecular-mass LPS and survive within egg albumin, has been commonly observed among field isolates of S. Enteritidis (Clavijo et al, 2006;Gast & Holt, 1995Guard-Petter, 1998;Guard-Petter et al, 1999;Jain & Chen, 2007;Lock & Board, 1992;Pan et al, 2009;Solano et al, 1998;Yim et al, 2010). S. Enteritidis strains also vary in their virulence potential in poultry, irrespective of phage types (Poppe et al, 1993) and even within clonal lineages (Olsen et al, 1999;Yim et al, 2010).…”

“…Most other studies to characterize the pathogenic potential of S. Enteritidis strains have primarily focused on isolates recovered from either human clinical cases or nonpoultry-associated environmental sources (Betancor et al, 2009;Lu et al, 1999;Pan et al, 2009; Solano et al, 1998Solano et al, , 2001; Yim et al, 2010). Humphrey et al (1996) showed that human isolates of S. Enteritidis PT4 with enhanced heat and acid tolerance were more virulent in mice and more invasive in chickens compared with poultryassociated strains of S. Enteritidis.…”

Identification of diverse Salmonella Serotypes, Virulotypes, and Antimicrobial Resistance Phenotypes in Waterfowl From Chile

“…Escherichia coli ATCC 25922 was used as a control strain. Virulence-associated genes pefA, spvC, sirA, gipA, SEN1417, trhH, and prot6e, all of which have been variably detected in the S. Enteritidis serotype (Pan et al 2009, Huehn et al 2010, were used as target sequences for the PCRbased virulotyping. DNA extraction was performed by the High Pure PCR Template preparation Kit Ò (Roche, Mannheim, Germany) following the manufacturer's recommendations.…”