Salmonella

The study aimed to evaluate the prevalence of Salmonella in retail and wholesale foods in Fukuoka Prefecture, Japan. A total of 2,021 samples collected between 1999 and 2010 were tested using a culture method. Samples consisted of liquid eggs (n=30), meat (beef and pork) (n=781), offal (n=69), processed meats (n=2), seafood (n=232), processed seafood (dried fish) (n=76), vegetables (n=481), processed vegetables (n=87), fruits (n=167), and herbs (n=96) from 574 outlets and wholesale agents in 15 areas (five samples were undocumented regarding outlets). Overall, liquid egg showed significantly (P<0.001) higher frequencies of Salmonella contamination (13.3%) than beef (1/423, 0.2%) and pork (3/235, 1.3%). Salmonella enterica subsp. enterica serovar Enteritidis, the most common serovar as a human pathogen, were isolated from two liquid egg samples. No Salmonella were isolated from seafood and vegetable-related samples including seed sprouts (n=261). In conclusion, liquid egg is a significant Salmonella vehicle, showing a need to continue the vaccination of chickens to prevent S. Enteritidis contamination in Japanese eggs. Moreover, further study is needed to evaluate Salmonella contamination in seed sprouts with more sampling from retailers there

Multi-locus sequence typing of Salmonella enterica subsp. enterica serovar Enteritidis strains in Japan between 1973 and 2004

Salmonella enterica subsp. enterica serovar Enteritidis (S. Enteritidis) was responsible for a worldwide pandemic during the 1980s and 1990s; however, changes in the dominant lineage before and after this event remain unknown. This study determined S. Enteritidis lineages before and after this pandemic event in Japan using multilocus sequence typing (MLST). Thirty S. Enteritidis strains were collected in Japan between 1973 and 2004, consisting of 27 human strains from individual episodes, a bovine strain, a liquid egg strain and an eggshell strain. Strains showed nine phage types and 17 pulsed-field profiles with pulsed-field gel electrophoresis. All strains had homologous type 11 sequences without any nucleotide differences in seven housekeeping genes. These MLST results suggest that S. Enteritidis with the diversities revealed by phage typing and pulsed-field profiling has a highly clonal population. Although type 11 S. Enteritidis may exhibit both pleiotropic surface structure and pulsed-field type variation, it is likely to be a stable lineage derived from an ancestor before the 1980s and/or 1990s pandemic in Japan

Pulsed-field profile diversities of Salmonella Enteritidis, S. Infantis, and S. Corvallis in Japan

The diversity of pulsed-field profiles (PFPs) within non-typhoidal Salmonella subtypes influences epidemiological analyses of Salmonella outbreaks. Therefore, determining the PFP diversity of each Salmonella serovar is important when evaluating current circulating strains. This study examined the PFP diversity of three important public health Salmonella enterica subspecies enterica serovars, S. Enteritidis (n=177), S. Infantis (n=205), and S. Corvallis (n=90), using pulsed-field gel electrophoresis. Isolates were collected from several sources, primarily from chicken-derived samples, in the Kyushu-Okinawa region of Japan between 1989 and 2005. S. Enteritidis isolates displayed 51 distinct PFPs (E-PFPs), with 92 (52.0%) and 32 (18.1%) isolates displaying types EPFP1 and E-PFP10, respectively. The 205 S. Infantis isolates showed 54 distinct PFPs (I-PFPs), with 87 (42.4%) and 36 (17.6%) isolates being I-PFP4 and I-PFP2, respectively. I-PFP18 was the dominant I-PFP of layer chicken isolates across a 5-year period. Fourteen distinct S. Corvallis PFPs were detected. Simpson’s index results for the genetic diversities of S. Enteritidis, S. Infantis, and S. Corvallis isolates were 0.70, 0.79, and 0.78, respectively. None of the EPFPs or I-PFPs of layer chicken isolates overlapped with those of broiler chicken isolates, and the dominant clonal lines existed for &gt;10 years. In conclusion, limited PFP diversities were detected amongst S. Enteritidis, S. Infantis, and S. Corvallis isolates of primarily chicken-derived origins in the Kyushu-Okinawa region of Japan. Therefore, it is important to take into account these limitations in PFP diversities in epidemiological analyses of Salmonella outbreaks

Simultaneous oral administration of Salmonella Infantis and S. Typhimurium in chicks

Abstract Background To confirm the hypothesis that Salmonella enterica subspecies enterica serovar (S.) Infantis has higher basic reproductive rates in chicks compared with other Salmonella serovars, 1-day-old specific-pathogen-free chicks (n = 8) were challenged simultaneously with S. Infantis and S. Typhimurium per os. Challenged chicks (Group A) were then housed with non-infected chicks (Group B, n = 4) for 6 days (from 2 to 8 days of age). Group B birds were then housed with other non-infected birds (Group C, n = 4), which were then transferred to cages containing a further group of untreated chicks (Group D, n = 2). A control group consisting of four non-infected chicks was used for comparison. All chickens were humanely sacrificed at 18 days of age, and Salmonella from bowel and liver samples were enumerated. Results Both serovars were isolated from all groups except the control group. S. Typhimurium was isolated at a greater frequency than S. Infantis from the bowel samples of chicks from Groups B, C and D, while no differences in colonisation rates were observed between the two serovars in liver samples from Groups B, C and D. S. Typhimurium, but not S. Infantis, was immunohistochemically detected in the lamina propria of the cecum and rectum in five birds of Group A. Despite the competitive administration, neither of the two serovars completely excluded the other, and no differences were observed in basic reproductive rates between the two serovars. Conclusions These findings, together with data from previous studies, suggest that the initial quantitative domination of S. Infantis in chicken flocks may explain why this serovar is predominant in broiler chickens

Increase in resistance to extended-spectrum cephalosporins in Salmonella isolated from retail chicken products in Japan.

Extended-spectrum β-lactamase (ESBL)-producing Salmonella are one of the most important public health problems in developed countries. ESBL-producing Salmonella strains have been isolated from humans in Asian countries neighboring Japan, along with strains harboring the plasmid-mediated extended-spectrum cephalosporin (ESC)-resistance gene, ampC (pAmpC). However, only a few studies have investigated the prevalence of ESC-resistant Salmonella in chicken products in Japan, which are the main vehicle of Salmonella transmission. The aim of this study was to investigate the prevalence of ESBL-producing, pAmpC-harboring, or carbapenem-resistant Salmonella in chicken products in Japan. In total, 355 out of 779 (45.6%) chicken product samples collected from 1996-2010 contained Salmonella, resulting in 378 distinct isolates. Of these isolates, 373 were tested for resistance to ESCs, cephamycins, or carbapenems. Isolates that showed resistance to one or more of these antimicrobials were then examined by PCR and DNA sequence analysis for the presence of the bla(CMY), bla(CTX-M), bla(TEM), and bla(SHV) resistance genes. Thirty-five resistant isolates were detected, including 26 isolates that contained pAmpC (bla(CMY-2)), and nine ESBL-producing isolates harboring bla(CTX-M) (n = 4, consisting of two bla(CTX-M-2) and two bla(CTX-M-15 genes)), bla(TEM) (n = 4, consisting of one bla(TEM-20) and three bla(TEM-52) genes), and bla(SHV) (n = 1, bla(SHV-12)). All pAmpC-harboring and ESBL-producing Salmonella isolates were obtained from samples collected after 2005, and the percentage of resistant isolates increased significantly from 0% in 2004 to 27.9% in 2010 (P for trend = 0.006). This increase was caused in part by an increase in the number of Salmonella enterica subsp. enterica serovar Infantis strains harboring an approximately 280-kb plasmid containing bla(CMY-2) in proximity to ISEcp1. The dissemination of ESC-resistant Salmonella containing plasmid-mediated bla(CMY-2) in chicken products indicates the need for the development of continuous monitoring strategies in the interests of public health

Location of <i>bla</i>_CMY-2 in <i>Salmonella enterica</i> subsp. <i>enterica</i> serovar (<i>S</i>.) Manhattan.

<p>(A) Pulsed-field gel electrophoresis (PFGE) separation of S1 nuclease- or <i>Bln</i>I-digested genomic DNA from <i>S.</i> Manhattan isolates, followed by Southern hybridization with a <i>bla</i>_CMY-2 probe. Lane 1, Lambda ladder marker; lanes 2 and 4, isolate 2179, which harbors <i>bla</i>_CMY-2; lanes 3 and 5, isolate 2129, which does not harbor <i>bla</i>_CMY-2. Lanes 2 and 3, S1 nuclease-digested genomic DNA; lanes 4 and 5, <i>Bln</i>I-digested genomic DNA. (B) Densitometric curves of PFGE separation with S1 nuclease- and <i>Bln</i>I-digested genomic DNA from <i>S.</i> Manhattan isolate 2179. The arrows show hybridization signals and corresponding positions of densitometric curves. Lambda ladder marker consisted of concatemers starting at 48.5 kb.</p

Large plasmid profiles of 70 <i>Salmonella</i> isolates.

<p>These isolates consisted of 25 isolates harboring <i>bla</i>_CMY-2 (23 <i>Salmonella enterica</i> subsp. <i>enterica</i> serovar Infantis, one <i>S</i>. Manhattan, and one O-untypeable:r:1,5), nine isolates harboring other <i>bla</i> genes (three <i>S</i>. Infantis and six <i>S.</i> Manhattan), and 36 isolates susceptible to 11 antibiotics (18 <i>S</i>. Infantis and 18 <i>S.</i> Manhattan). The 70 isolates generated eight large plasmid profiles (LPPs). The <i>S.</i> Infantis isolates generated LPPs 1 (n = 41), 2 (n = 1), 3 (n = 1), and 4 (n = 1). All <i>S.</i> Infantis isolates harboring <i>bla</i> genes showed LPP 1, except for one <i>S</i>. Infantis isolate carrying <i>bla</i>_CTX-M-2 that was classified as LPP 2. All 18 susceptible <i>S.</i> Infantis isolates showed LPP 1, except for two isolates that were collected in 2009 and 2008 showing LPP 3 and LPP 4, respectively. One O-untypeable:r:1,5 isolate was classified as LPP 1. <i>S.</i> Manhattan isolates generated four different LPPs (LPP 5-LPP 8). LPPs 5, 6, 7, and 8 were found in one, 21, one, and two <i>S.</i> Manhattan isolate(s), respectively. <i>S.</i> Infantis, O-untypeable:r:1,5, and <i>S.</i> Manhattan are expressed as <i>S.</i> I, OUT, and <i>S.</i> M in the figure, respectively.</p

Pulsed-field gel electrophoresis profiles (PFPs) of 70 <i>Salmonella</i> isolates harboring <i>bla</i> and non-<i>bla</i> genes.

<p>The isolates consisted of 25 isolates harboring <i>bla</i>_CMY-2 (23 <i>Salmonella enterica</i> subsp. <i>enterica</i> serovar Infantis, one <i>S</i>. Manhattan, and one O-untypeable:r:1,5), nine isolates harboring other <i>bla</i> genes (three <i>S</i>. Infantis and six <i>S.</i> Manhattan), and 36 isolates susceptible to 11 antibiotics (18 <i>S</i>. Infantis and 18 <i>S.</i> Manhattan). One <i>S</i>. Infantis isolate that harbored <i>bla</i>_CMY-2 could not be analyzed by PFGE because of damage that occurred during storage. The letters, names, and figures in parentheses on the right of the dendrogram are PFPs, resistance genes, and sampling year of isolates, respectively. The 44 <i>S</i>. Infantis isolates were subtyped as: PFP A (n = 1), PFP B (n = 3), PFP C (n = 12), PFP D (n = 1), PFP E (n = 1), PFP F (n = 1), PFP G (n = 1), PFP H (n = 6), PFP I (n = 3), PFP J (n = 1), PFP K (n = 1), PFP L (n = 6), PFP M (n = 1), PFP N (n = 3), PFP P (n = 2), and Q (n = 1). The 25 <i>S.</i> Manhattan isolates belonged to subtypes PFP R (n = 24) and PFP S (n = 1). One O-untypeable:r:1,5 isolate was PFP E. The scale indicates the percent similarity, as determined by the Dice coefficients.</p