Differentiation of Salmonella serovar infantis isolates from human and animal sources by fingerprinting IS200 and 16S rrn loci

Abstract

We genotyped SalmoneUla serovar infantis (referred to as S. infantis), which is the most widespread serovar among animals and the third most common cause of human salmonellosis in Finland. Molecular fingerprinting of the 16S rrn locus and the Salmonella-specific insertion sequence IS200 was used to type the 131 isolates originating from the main sources of S. infantis infection. The number of IS200 elements in S. infantis varied from zero to seven; three or more copies were present in 97% of the isolates, and 71% had four copies. There were four conserved chromosomal positions of IS200, which allowed us to group the isolates into three major clonal groups. We defined 11 unique IS200 profiles and five different ribotypes which, in combination, generated 15 genotypes highly restricted to the infection sources: 8 genotypes were typical of isolates from broiler chickens and cattle and seven genotypes were typical of isolates from humans. The eight genotypes of isolates from chickens represented two clonal groups which were differentially associated with chickenproducing companies. The typing scheme allows efficient discrimination between isolates from various infection sources and within sources and, therefore, provides a unique molecular tool for use in the study of the epidemiology of S. infantis infection.

Identification and Characterization of Salmonella Isolates by Automated Ribotyping

“…Thus, the greatest sensitiv-ity for typing Salmonella was achieved when serotyping and automated ribotyping were applied together. Other investigators (2,10,13,14) have reached similar conclusions, i.e., that it is best to use more than one typing method when conducting epidemiological investigations of Salmonella outbreaks.…”

A comparison of three molecular typing methods for the discrimination ofSalmonella entericaserovar Infantis

“…Infantis is acknowledged as a significant Salmonella serovar. It has been routinely isolated from both human and environmental sources in a number of geographically diverse countries including Brazil (Fonseca et al , 2006), Argentina (Merino et al , 2003), Japan (Shahada et al , 2006; Asai et al , 2007) and Finland (Pelkonen et al , 1994; Lindqvist & Pelkonen, 2007).…”

“…A number of typing methods have been used in the past for the identification of likely causative agents. These include antimicrobial sensitivity profiles, ribotyping, amplified fragment length polymorphism, multilocus sequence typing (MLST), REP (repetitive DNA sequence)‐PCR, enterobacterial repetitive intergenic consensus sequences‐based PCR (ERIC‐PCR), IS‐200 profiling, plasmid profiling and pulsed‐field gel electrophoresis (PFGE) (Pelkonen et al , 1994; Kotetishvili et al , 2002; Merino et al , 2003; Ross & Heuzenroeder, 2005a; Fonseca et al , 2006; Shahada et al , 2006; Asai et al , 2007; Lindqvist & Pelkonen, 2007). Phage typing systems, similar to those used for specific S. enterica serovars including Typhimurium and Enteritidis, have been developed previously for S .…”

Analysis of the clonal relationship among clinical isolates of Salmonella enterica serovar Infantis by different typing methods

“…Various typing techniques have been used in epidemiological studies to differentiate isolates of Salmonella serovars, but only a few of them have been used to discriminate Salmonella Infantis strains, since this serovar is infrequently encountered causing human disease in developed countries 8,17,23 . The applied epidemiological tools include biotyping, phage typing, colicine typing, antimicrobial susceptibility testing, plasmid profiling, restriction endonuclease analysis of whole chromosomal DNA by pulsed field gel electrophoresis (PFGE), repetitive extragenic palindromic (REP) sequences analysis by PCR, enterobacterial repetitive intergenic consensus (ERIC) analysis by PCR, restriction fragment length polymorphism (RFLP) of 16S rRNA and insertion sequence IS200 13,14,22 .…”