Antimicrobial susceptibility of Trueperella pyogenes isolated from cattle and pigs with septicemia in southern Kyushu, Japan.

We investigated the antimicrobial susceptibility of Trueperella pyogenes isolates from cattle and pigs diagnosed with septicemia at slaughter. The strains investigated in this study were found to be susceptible to ampicillin, cefazolin, gentamicin, and levofloxacin. However, 53.3% of the strains were resistant to tetracycline, 49.7% to streptomycin, 13.8% to erythromycin, 13.2% to clindamycin, and 1.2% to oxacillin and kanamycin. We also found that the resistance of pig-derived strains of T. pyogenes to tetracycline, streptomycin, erythromycin, and clindamycin was higher than that of cattle-derived strains, and these strains were resistant to up to four antimicrobial agents used simultaneously. The present results provide new data on the range of the minimum inhibitory concentration (MIC) values of various antimicrobial agents for T. pyogenes isolated from livestock with septicemia. The breakpoint values used in this study are generally considered applicable.

Decreasing trend of ß-lactam resistance in Salmonella isolates from broiler chickens due to the cessation of ceftiofur in ovo administration.

Ceftiofur, a third-generation cephalosporin antimicrobial, was used in Japanese hatcheries for many years before 2012. We continue to study Salmonella in broilers and their antimicrobial resistance. The current study aimed to express how the cessation of ceftiofur affects the antimicrobial resistance of Salmonella isolated from broiler chickens in Kagoshima Prefecture, Japan in 2017 and 2018. A total of 274 Salmonella isolates were recovered from 1535 cecal content samples obtained from 96 broiler flocks over years 2017 and 2018. Among the S. enterica isolates, the predominant serovars were S. Manhattan (128/274, 46.7%), S. Schwarzengrund (120/274, 43.8%), and S. Infantis (26/274, 9.5%). The isolates showed a high proportion of antimicrobial resistance for oxytetracycline, sulfamethoxazole, and streptomycin. However, the ß-lactam resistance rates were significantly decreased (p < 0.01) in 2017, while no ß-lactam resistant isolates detected in 2018. The highlight of this study was the complete disappearance of ß-lactam resistance in Salmonella isolates from broiler chicken in Kagoshima, Japan.

The incidence of Campylobacter contamination levels through Chicken-Sashimi Processing steps in A Small-scale Poultry processing plant applying the External stripping method.

This study aimed to analyze the incidence of Campylobacter in a small-scale chicken meat processing plant producing "chicken-sashimi", and determine the effectiveness of surface burning as a treatment during processing. The most probable number (MPN) method was used to analyze the load of Campylobacter in 48 samples from four different processing steps (de-feathering, chilling, surface burning, and final-products; 12 samples each). We found the highest load of isolated bacteria in chicken skin after de-feathering. Campylobacter was not detected after the surface burning step despite a large load of bacteria present in the cecum content. Campylobacter was absent in the final products. Adequate surface burning can avoid Campylobacter contamination of chicken sashimi in the processing plant by applying the external stripping method.

Surveillance of Shiga toxin-producing Escherichia coli and Campylobacter spp. in wild Japanese deer (Cervus nippon) and boar (Sus scrofa).

Increasing game meat consumption in Japan requires the dissemination of safety information regarding the presence of human pathogens in game animals. Health information regarding the suitability of these animals as a meat source is not widely available. In this study, we aimed to evaluate the safety of game meat and detect potential human pathogens in wild deer (Cervus nippon) and boar (Sus scrofa) in Japan. Fecal samples from 305 wild deer and 248 boars of Yamaguchi, Kagoshima, and Tochigi prefectures collected monthly for 2 years were examined for the prevalence of Shiga toxin-producing Escherichia coli (STEC) and Campylobacter spp. STEC was isolated from 51 deer consistently throughout the year and from three boars; O-antigen genotype O146, the expression of stx2b, and eaeA absence (n=33) were the major characteristics of our STEC isolates. Other serotypes included the medically important O157, stx2b or stx2c, and eaeA-positive (n=4) and O26, stx1a, and eaeA-positive strains (n=1). Campylobacter spp. were isolated from 17 deer and 31 boars. Campylobacter hyointestinalis was the most common species isolated from 17 deer and 25 boars, whereas Campylobacter lanienae and Campylobacter coli were isolated from three and two boars, respectively. Seasonal trends for the isolation of these bacteria were not significant. This study demonstrates that wild game animals carry human pathogens; therefore, detailed knowledge of the safe handling of game meat is needed to prevent foodborne infections.

16S rRNA Gene Amplicon Sequence Data from Feces of Wild Deer (Cervus nippon) in Japan.

We report 16S rRNA amplicon sequence data from feces of 109 wild deer in Japan. The dominant bacterial taxa in fecal microbiota of wild deer hunted between village and mountainous areas and those living on Miyajima Island and in Nara Park were similar but differed in abundance.

16S rRNA Gene Amplicon Sequence Data from Feces of Five Species of Wild Animals in Japan.

We report 16S rRNA amplicon sequence data from feces from 58 wild boars, 60 feral raccoons, 9 wild Japanese badgers, 21 wild masked palm civets, and 8 wild raccoon dogs in Japan. The predominant bacterial taxa in the fecal microbiota were similar in part but varied among the animal species.

α-Sens: The improved ARE-Nrf2-based sensitization screening assay using normalized transcriptional activity.

Two non-animal test methods, KeratinoSens™ and LuSens, have been approved by the Organization of Economic Cooperation and Development (OECD) test guidelines for evaluating the sensitization potential of chemicals, and been positioned as a method for appraising key event (KE)-2, namely, the keratinocyte response component of the Adverse Outcome Pathway (AOP) in sensitization process. However, these two methods require separate cytotoxicity tests to determine the concentrations to be tested in the main test. Therefore, we developed a simple and highly accurate KE-2 test method named α-Sens that uses the dual luciferase assay system and attempted a further application of luciferase-based determination of cell viability to calculate the normalized Antioxidant response element (ARE)-mediated transcriptional activity, named normalized ARE Activity (nAA), to evaluate the sensitizing potential of chemicals. A cell line carrying the ARE-inducible Firefly luciferase reporter gene and Thymidine kinase (TK) promoter-driven Renilla luciferase gene was established and used for the α-Sens. A total of 28 chemicals, consisting of 19 skin sensitizers and nine non-skin sensitizers were tested by this assay system. The α-Sens yielded an accuracy (%), sensitivity (%), and specificity (%) against corresponding values for local lymph node assay of 96.4 %, 95.0 %, and 100 %, respectively, and for human data of 100 % for all. The α-Sens gave clear positive results for phenyl benzoate and eugenol, chemicals for which KeratinoSens™ or LuSens yielded false-negative results, using a new parameter. Our results suggest that better prediction capacity could be achieved by using nAA as a classifier compared to other existing KE-2 test methods. In conclusion, the α-Sens is promising as a simple and highly accurate in vitro skin sensitization test method for evaluation of KE-2.

Differences in phenotypic and genetic characteristics of Trueperella pyogenes detected in slaughtered cattle and pigs with septicemia.

We investigated the hemolytic properties, biochemical properties, and possession of virulence factor genes of Trueperella pyogenes isolated from cattle and pigs with septicemia. The porcine strains showed significantly stronger hemolyticity than the bovine strains. In addition, T. pyogenes from cattle and pigs also differed in biochemical properties. Virulence factor genes (nanP, cbpA, fimC, and fimE) were more prevalent in bovine strains, whereas other virulence factor genes (nanH and fimG) were more prevalent in porcine strains. T. pyogenes isolated from pig and cattle with septis cases in Japanese meat inspection showed variability in biochemical and genetic properties. Differences were observed between porcine and bovine strain in term of the hemolytic strength and possession of genes for factors promoting adhesions which are considered pathogenic.

Increased Salmonella Schwarzengrund prevalence and antimicrobial susceptibility of Salmonella enterica isolated from broiler chickens in Kagoshima Prefecture in Japan between 2013 and 2016.

This study aimed to analyze the Salmonella serovars, measure the minimum inhibitory concentration of antimicrobials, and examine the antimicrobial resistance genes of Salmonella isolated from 192 broiler flocks in Kagoshima Prefecture in Japan, from 2013 to 2016. We found that all Salmonella isolates belonged to three serovars: Salmonella Manhattan, S. Infantis, and S. Schwarzengrund. Among them, S. Schwarzengrund prevalence has recently increased annually making the main serovar. Most recovered isolates were highly resistant to streptomycin, sulfamethoxazole, and oxytetracycline. We saw the reduction of third-generation cephalosporin resistance and identified the reason of increased kanamycin resistance to be the increased number of S. Schwazengrund isolates. Among the kanamycin-resistant Salmonella isolates, aphA1 constituted the main resistance gene detected.

Surveillance of antibiotic resistance in Escherichia coli isolated from wild cranes on the Izumi plain in Kagoshima prefecture, Japan.

The prevalence of antibiotic resistance in 376 Escherichia coli (E. coli) isolates from fecal samples of Hooded and White-naped cranes was investigated on the Izumi plain in Kagoshima prefecture, Japan, during winter 2016 and 2017. Resistance to oxytetracycline, ampicillin, and nalidixic acid were observed in 10.9%, 3.1-4.4%, and 2.1-7.7% of isolates, respectively. Since the previous surveillance in 2007, isolation rates of antibiotic-resistant E. coli recovered from wild cranes have remained at significantly low levels compared with those in Japanese livestock. Our results indicate that surveillance of antibiotic-resistant E. coli from wild cranes wintering in the Izumi plain could be a useful strategy to indicate natural environmental pollution by antibiotic-resistant bacteria in the environment.

Prevalence of Salmonella in broiler chickens in Kagoshima, Japan in 2009 to 2012 and the relationship between serovars changing and antimicrobial resistance.

BACKGROUND: This study aimed to examine the prevalence, serovars, and antimicrobial resistance of Salmonella isolates from broiler chickens in Kagoshima, Japan. A total of 192 flocks and 3071 samples were collected from broiler chickens at local farms in Kagoshima, Japan from 2009 to 2012. RESULT: Among the tested farms, 49.0% of flocks were positive for Salmonella, and 243 isolates were obtained from 3071 cecal samples (7.9%). All the Salmonella isolates were one of three serovars: S. Infantis (57.6%); (140/243), S. Manhattan (40.3%; 98/243 and S. Schwarzengrund (2.1%; 5/243). The proportion of S. Infantis isolates decreased from 66.0% in 2009 to 50.0% in 2011 but increased to 57.6% in 2012, while the proportion of S. Manhattan isolates significantly increased from 26.4 to 50% from 2009 to 2011, and decreased moderately to 40.9% in 2012. Most of the recovered Salmonella isolates were resistant to three antimicrobials, i.e., streptomycin (95.1%), sulfamethoxazole (91.0%) and oxytetracycline (91.4%). In contrast, all Salmonella strains were susceptible to chloramphenicol. Comparison of this study to previous studies of the antimicrobial susceptibility of Salmonella isolates showed that: the percentage of antibiotic-resistance isolates increased dramatically for two antibiotics, ampicillin (from 22.4 to 55.1%) and cefotaxime (from 9.1 to 52.7%). In contrast, the percentage of ofloxacin-resistant isolates decreased across the three survey periods, from 20.8% in 2004-2006 to 1.6% in the present study period (2009-2012). In addition, S. Infantis exhibited a variety of resistance to antimicrobials examined from sensitive to resistance to eight antimicrobials. Multidrug resistance to more than 6 six antimicrobials was detected in 113 (46.5%) of the isolates, and most of them were S. Manhattan. CONCLUSIONS: There was a marked change in the serovars and antimicrobial resistance profiles of the Salmonella isolates in this study compared to those in previous studies. The percentage of S. Manhattan isolates increased as did the percentages of ampicillin- and cefotaxime-resistant isolates.

Chronological Change of Resistance to ß-Lactams in Salmonella enterica serovar Infantis Isolated from Broilers in Japan.

Epidemiologic surveillance study was conducted in southern Japan to determine the antimicrobial resistance phenotypes and characterize the ß-lactamase genes and the plasmids harboring these genes in Salmonella enterica serovar Infantis (S. Infantis) isolates from broilers. Between January, 2007 and December, 2008, a total of 1,472 fecal samples were collected and examined at the Laboratory of Veterinary Public Health, Kagoshima University, Japan. In 93 (6.3%) isolates recovered, 33 (35.5%) isolates showed resistance to cefotaxime, an extended-spectrum cephalosporin (ESC), conferred by TEM-20, TEM-52 and CTX-M-25 extended-spectrum ß-lactamases (ESBLs). In addition to ESC-resistance, eight (8.6%) isolates exhibited resistance to cefoxitin mediated by CMY-2 AmpC ß-lactamase. Plasmid analysis and polymerase chain reaction replicon typing revealed the bla TEM-20 and bla CMY-2 genes were associated with IncP plasmids, bla TEM-52 was linked with a non-typable plasmid and bla CTX-M-25 was carried by an IncA/C plasmid. Non-ß-lactam resistance to streptomycin, sulfamethoxazole, and oxytetracycline encoded by the aadA1, sul1, and tet(A) genes, respectively, was found in 86 (92.5%) isolates. Resistance to kanamycin and ofloxacin was exhibited in 12 (12.9%) and 11 (11.8%) isolates, respectively, the former was mediated by aphA1-Iab. These data indicate that S. Infantis isolates producing ESBLs and AmpC ß-lactamase have spread among broiler farms in Japan. These data demonstrated that the incidence of ESC-resistant S. Infantis carrying bla TEM-52 remarkably increased and S. Infantis strains harboring bla CMY-2, bla TEM-20, or bla CTX-M-25 genes emerged from broilers in Japan for the first time in 2007 and 2008.

Prevalence and epidemiological relationship of CMY-2 AmpC ß-lactamase and CTX-M extended-spectrum ß-lactamase-producing Escherichia coli isolates from broiler farms in Japan.

To evaluate the prevalence of extended-spectrum cephalosporin (ESC)-resistant Enterobacteriaceae in broiler chickens, 41 rectal samples taken from 4 commercial farms were examined. Desoxycholate hydrogen sulfide lactose agars, supplemented with either 4 µg/ml cefotaxime or 16 µg/ml ceftazidime, were used to screen ESC-resistant bacteria. ESC-resistant bacteria were isolated from all samples. Of the 164 ESC-resistant bacteria (included 4 isolates per a sample), 163 were Escherichia coli, while 1 isolate was identified as Enterobacter cloacae. Extended-spectrum ß-lactamase (ESBL) genes and plasmid-mediated AmpC ß-lactamase genes in the isolates were determined by PCR and sequencing. One AmpC ß-lactamase gene, bla(CMY-2) (66%), and 4 ESBL genes, bla(CTX-M-1) (26%), bla(CTX-M-55) (10%), bla(SHV-5) (4%) and bla(CTX-M-2) (3%), were detected in the E. coli isolates. The epidemiological relationship of the CMY-2 and CTX-M ß-lactamase-producing isolates among the farms was analyzed by pulsed-field gel electrophoresis using the XbaI restriction enzyme. Forty-one (Y1-Y41) and 14 (X1-X14) clusters were found in the CMY-2 and CTX-M-carrying E. coli isolates, respectively. Some clusters included isolates derived from more than 1 farm, indicating some cross-contamination of clonal strains and spread of CMY-2 AmpC ß-lactamase or CTX-M ESBL among the farms.

Emergence of Salmonella enterica serovar infantis harboring IncI1 plasmid with bla(CTX-M-14) in a broiler farm in Japan.

Cefotaxime (CTX)-resistant and -susceptible Salmonella enterica serovar Infantis isolates obtained from broilers raised on a farm in January 2010 in Japan were characterized to establish their resistance determinants. The CTX-resistant isolates produced CTX-M-14 extended-spectrum ß-lactamase and harbored 2 distinct plasmid of approximately 140- and 95-kb, whereas the CTX-susceptible isolates harbored one 140-kb plasmid. The 95-kb plasmids were replicon typed as IncI1 carrying the bla(CTX-M-14) gene, while the 140-kb plasmids were IncP and harbored the aphA1, aadA1, tetA, and sul1 genes. Genetic fingerprinting by pulsed-field gel electrophoresis revealed similar macrorestriction profiles amongst CTX-resistant and susceptible isolates, suggesting a clonal relationship. The presence of CTX-resistant S. Infantis on a broiler farm has occurred through the acquisition of IncI1 resistance plasmid.

Effect of cooled and chlorinated chiller water on Campylobacter and coliform counts on broiler carcasses during chilling at a middle-size poultry processing plant.

To evaluate the effect of cooled and chlorinated chill water for Campylobacter and coliforms at a middle-size processing plant which was considered to be difficult for eliminate pathogenic bacteria on carcasses, following three conditions were examined; keeping temperature at < 20, < 10 and < 10°C, and chlorine concentration at < 50, < 50 and 50 to 70 ppm during processing in experiment 1, 2 and 3 respectively. Fifteen prechill and 15 postchill carcasses were examined in each experiment. In lower temperature of experiment 2, decreasing rate (%) of coliforms was significantly higher (P<0.01) than that in experiment 1. In higher chlorination of experiment 3, no Campylobacter was detected from all postchill carcasses.

Re-emergence of multi-drug resistant Salmonella enterica serovar Stanley from cattle.

During 2009, Salmonella enterica subspecies enterica serovar Stanley isolates were recovered from cattle diagnostic specimens in southern Japan, and the isolates were examined to characterize the genetic determinants involved in this new pathogenicity that associated with mortality in cattle. All the isolates were multi-drug resistance exhibited resistance to ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, oxytetracycline, and kanamycin (ACSSuT-Km) encoded by blaTEM, catA, aadA1, sul1, tet(A), and aphA1 genes, respectively. Class 1 integrons of 1.5-kb size were detected in all MDR isolates. The isolates harboured easily transferable plasmids of ca. 210-kb with the potential of transmitting resistance phenotype and genotype detected in the donor isolates. XbaI-digested PFGE patterns generated two related clusters implicated in the dissemination of multi-drug resistance amongst Salmonella Stanley isolates. An emergence of multi-drug resistant Salmonella Stanley amongst food-producing animals, including cattle is a threat to human health, as resistant isolates may be transmitted to humans through the food chain.

Characterization of antibiotic resistance and the emergence of AmpC-producing Salmonella Infantis from pigs.

During the period of 2007-2008, a total of 270 pig fecal samples were collected from a meat processing plant located in southern Japan and examined for Salmonella species. A total of 44 Salmonella isolates were recovered, and antimicrobial resistance was detected in serotypes Typhimurium (n=9), Infantis and Choleraesuis (n=2), and Derby, Miyazaki and Schwarzengrund (n=1). Multidrug resistance was seen in serotypes Typhimurium (n=8) and Infantis (n=2). The most commonly observed resistance phenotypes were against streptomycin, oxytetracycline and sulfamethoxazole (100%), ampicillin (90%), chloramphenicol (50%), cephalothin (30%) and cefoxitin, ceftazidime and kanamycin (each 20%). Extended-spectrum cephalosporin-resistant Salmonella Infantis isolates producing plasmid-mediated, bla(CMY-2) gene were detected. These AmpC-producing isolates showed resistance to ampicillin and cephems (cephalothin, cefoxitin and ceftazidime). Resistance transfer experiments showed that transconjugants and transformants coexpressed resistance phenotypes similar to the donor isolates. To the best of our knowledge, this is the first report worldwide describing serovar Infantis from pigs capable of producing AmpC ß-lactamase. Then, we detected the pentadrug-resistance phenotype in Salmonella Typhimurium isolates, which yielded class 1 integron amplicons of 1.0 and 1.2 kb. Genetic fingerprinting analysis by pulsed-field gel electrophoresis and an assay by polymerase chain reaction confirmed the isolates to be Salmonella Typhimurium DT104. In conclusion, the findings of this survey call for the systematic and comprehensive domestic and international surveillance programs to determine the true rates of occurrence of AmpC-producing Salmonella both in the livestock and public health sectors.

Genetic analysis of multidrug-resistant Salmonella enterica serovars Stanley and Typhimurium from cattle.

During 2005-2008, a longitudinal study was conducted in southern Japan to detect and characterize multidrug-resistant Salmonella enterica serovars recovered from cattle diagnostic specimens. Determination of antimicrobial resistance phenotypes and genotypes, identification of Salmonella genomic island 1 (SGI1), detection of virulence genes, plasmid analysis, conjugal transfer experiments, and sequencing of class 1 integrons were conducted. Multidrug-resistant Salmonella detected were serovars Stanley, Typhimurium, and O4:d. Salmonella Stanley isolates exhibited resistance to ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, oxytetracycline, trimethoprim, and kanamycin (ACSSuT+) encoded by bla(TEM), catA, aadA2, tetA, sul1, dfrA12, and aphA1 genes, respectively. Sequencing analysis revealed that aadA2 and dfrA12 were integrated as gene cassettes within the class 1 integrons of 1.5kb size. Importantly, the isolates harboured easily transferable plasmids of ca. 210kb with the potential of transmitting resistance phenotype and genotype detected in the donor isolates. Moreover, Salmonella Typhimurium DT104 isolates with typical SGI1 were detected and presented ACSSuT+ resistance phenotype encoded by bla(PSE-1) and bla(TEM); floR; aadA1; sul1; and tetA and tetG, respectively. Salmonella Typhimurium isolates carried plasmids of variable sizes ranging from 3.5 to 100 kb with DT104 isolates harbouring plasmids of ca. 90 kb. Salmonella serovar O4:d had ACSSuT+ resistance phenotype mediated by bla(TEM), catA, aadA1, sul1, tetA, and aphA1 genes. A virulence gene invA was found in all multidrug-resistant Salmonella Typhimurium, Stanley and O4:d clinical isolates. In conclusion, this is the first report describing the occurrence of multidrug-resistant Salmonella Stanley from bovine species. The emergence of Salmonella Stanley isolates exhibiting plasmid-encoded high-level multidrug resistance is an important health concern because this new pathogenecity was associated with mortality in cattle.

Antimicrobial susceptibility of Erysipelothrix rhusiopathiae isolated from pigs in Southern Japan with a modified agar dilution method.

The determination of antimicrobial minimum inhibitory concentration (MIC) in Erysipelothrix rhusiopathiae by using the agar dilution method has not been covered by the Clinical and Laboratory Institute (CLSI). Only the broth microdilution method has been outlined. This report describes a modification of the agar dilution procedure for E. rhusiopathiae using Trypto-soy agar supplemented with 0.1% Tween 80 and incubation in ambient air at 37 degrees C for 24 hr. The MICs of the assay were in agreement with those of the broth microdilution method recommended by the CLSI. Antimicrobial susceptibility test was performed using this method for 149 E. rhusiopathiae isolates from 2 meat processing plants in Kagoshima Prefecture during the period of April 2004 to March 2005. The number of strains resistant to oxytetracycline, erythromycin, lincomycin, ofloxacin and enrofloxacin were 56 (37.6%), 4 (2.7%), 18 (12.1%), 21 (14.1%) and 19 (12.8%), respectively. All strains were susceptible to ampicillin.

Genetic analysis of multi-drug resistance and the clonal dissemination of beta-lactam resistance in Salmonella Infantis isolated from broilers.

An epidemiologic study was conducted to investigate the incidence and characterize the antimicrobial resistance determinants, analyzing plasmid profiles, and establishing the genetic relationship among beta-lactam-resistant isolates of Salmonella Infantis from broilers in Southern Japan. A total of 120 isolates were recovered from 56 flocks belonging to 44 holdings during 2004-2006. The percentages of resistance were as follows: ampicillin (24%), cephalothin (23%), cefoxitin (0%), ceftazidime (11%), cefotaxime (11%), chloramphenicol (0%), kanamycin (7.5%), ofloxacin (20%), oxytetracycline, streptomycin and sulfamethoxazole (100%) and trimethoprim (75%). The incidence of bla(TEM)-encoded beta-lactam resistance in 2004-2006 was significantly higher than in 1998-2003 (P<0.001). BlnI-digested PFGE patterns generated two related clusters implicated in the dissemination of beta-lactam resistance. Two types of plasmid profiles were observed and two plasmids of ca. 50 and 180-kb size were carried by beta-lactam-resistant isolates. Streptomycin resistance was conferred by aadA1 (n=116), aadA1-aadA2 (n=1), and aadA1-strA-strB (n=3). Resistances to kanamycin, oxytetracycline, sulfamethoxazole and trimethoprim were conferred by aphA1 (n=9, 100%), tetA (n=120, 100%) sul1 (n=120, 100%) and dfrA5 (n=90, 100%), respectively. Two types of class 1 integrons were detected: 1.0 kb (n=120) and, 1.0/1.5 kb (n=3). Integrons of 1.0/1.5 kb were found in isolates with the aadA1-strA-strB gene combination. For the first time, all S. Infantis isolates showed resistance to at least three classes of antimicrobial agents; and the intestinal tract of healthy poultry was a reservoir of the extended-spectrum cephalosporin-resistant isolates of serovar Infantis.