Genomic Diversity Within Phage Types ofSalmonella entericassp.entericaSerotypes Enteritidis and Typhimurium

Abstract

The diversity among 1354 strains of Salmonella enterica subsp. enterica, serotype Enteritidis (n = 847) and Typhimurium (n = 507) isolated in Finland in 1991-2002 (n = 608) and in 2003 (n = 746) were studied. The former strains were studied retrospectively by phage typing and pulsed-field gel electrophoresis (PFGE) harmonized in the European Salm-gene project. The latter strains were studied prospectively, and the results correlated to their antimicrobial susceptibility and association with travel to popular tourist destinations. During both periods, S. Enteritidis phage types (PTs) PT1 and PT4, and S. Typhimurium definite types (DTs) DT1 and DT104 were the major phenotypes. SENTXB.0001 was the dominating single PFGE type among S. Enteritidis strains (40% in 1991-2002; 57% in 2003), and accounted correspondingly for 23% and 63% of the PT1 strains, and 81% and 88% of the PT4 strains. No PFGE types dominated among the S. Typhimurium strains but a correlation was found between certain phage and PFGE types: among DT1 strains, STYMXB.0098 accounted for 66% (1991-2002) and 98% (2003) and among the DT104 strains STYMXB.0001 accounted for 84% and 97% in the two time periods, respectively. Of the S. Enteritidis strains isolated in 2003, 91% were associated with travel, most commonly to Spain, Greece, and Bulgaria. SENTXB.0001 was the major Salmonella PFGE type in these countries. In contrast, most (55%) S. Typhimurium strains were of domestic origin. While only 1.3% of the S. Enteritidis strains were multiresistant and 24% were resistant to nalidixic acid only, 30% of the S. Typhimurium strains were multiresistant. Among the multiresistant S. Typhimurium strains, R-type ACSSuT and PFGE type STYMXB.0001 of the DT104 complex dominated.

Evidence for a Second Genomic Island Conferring Multidrug Resistance in a Clonal Group of Strains of Salmonella enterica Serovar Typhimurium and its Monophasic Variant Circulating in Italy, Denmark, and the United Kingdom

“…The antimicrobials tested were those included in the Enternet reference panel (42). PFGE was performed according to the Pulsenet protocol (27) using XbaI as a restriction enzyme.…”

“…Pulsed-field gel electrophoresis (PFGE) analysis showed that these tetraresistant strains belonged to a unique clonal group, different from the DT104 ACSSpSuT clone (13). Using the PulseNet Europe database (27), it has been possible to verify that ASSuT strains of S. Typhimurium and its monophasic variant isolated in Denmark and the United Kingdom exhibited PFGE patterns that were the same as or very closely related to those of the Italian strains, suggesting that an ASSuT clonal group was circulating in different European countries.…”

Reduced Fluoroquinolone Susceptibility inSalmonella entericaIsolates from Travelers, Finland

“…Pulsed-fi eld gel electrophoresis (PFGE) was performed using PulseNet standardized protocol with few modifi cations (9). We considered any difference between 2 profi les to be suffi cient to distinguish 2 different PFGE profi les.…”

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

“…Three prophage regions are mainly responsible for the difference, and include a 38 kb ST64B region, an 18 kb Fels-2 region and a few genes belonging to prophages ST27 and ST35 . Salmonella phage typing has become the recognized method by which epidemiologists attribute Salmonella outbreaks or epidemics to a specific strain type (Boccia et al, 2004;Lukinmaa et al, 2006;Usera et al, 1994). Within the last decade, S. Enteritidis PT4 and PT6 have been the most prevalent in Europe (Echeita et al, 2005;Gillespie et al, 2005), whereas in the USA and Canada, PT8 and PT13a are the most common types (Brown et al, 1999;White et al, 2007).…”