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.
The aim was to isolate Campylobacter jejuni-specific lytic phages from meats on the market in Japan. These phages were effectively isolated from 13 of 15 86.7% retail chicken meat samples skin and liver by the enrichment method using Preston Campylobacter Selective Enrichment Broth and 10 host Campylobacter strains. Among the 26 phage isolates, 14 were extracted by means of C. jejuni L26 as a host strain. Phage PHC10 showed the broadest lytic spectrum: active against 67.4% of the 46 C. jejuni strains tested. The other phage isolates showed different lytic spectra. Because phages PHC5, PHC10, PHC19, PHC22, and PHC25 possess an icosahedral head and a contracted tail, they seem to be members of the Myoviridae family. Effects of 19 phage isolates on viability of C. jejuni were investigated. These phages reduced viable counts of C. jejuni by 1-3 log after 6-12 h of incubation at 42 as compared to the initial counts. The C. jejuni L26 was found to be suitable as a host because of the wide hosting range. The phages isolated in this study seem to be promising biocontrol agents against C. jejuni in food.
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