Antimicrobial resistance, plasmid, virulence, multilocus sequence typing and pulsed-field gel electrophoresis profiles of Salmonella enterica serovar Typhimurium clinical and environmental isolates from India

Multi-locus sequence typing, antimicrobials resistance and virulence profiles of Salmonella enterica isolated from bovine carcasses in Minas Gerais state, Brazil

The aim of this study was to identify virulence and antimicrobial resistance profiles and determine the sequence type (ST) by multilocus sequence typing (MLST) of Salmonella enterica isolates from bovine carcasses from slaughterhouse located in Minas Gerais state, Brazil, and its relationship with bovine isolates obtained on the American continent based on sequence type profile. The MLST results were compared with all Salmonella STs associated with cattle on American continent, and a multi-locus sequence tree (MS tree) was built. Among the 17 S. enterica isolates, five ST profiles identified, and ST10 were the most frequent, grouping seven (41.2%) isolates. The isolates presented 11 different profiles of virulence genes, and six different antibiotics resistance profiles. The survey on Enterobase platform showed 333 Salmonella STs from American continent, grouped into four different clusters. Most of the isolates in the present study (13/17), were concentrated in a single cluster (L4) composed by 74 STs. As a conclusion, five different STs were identified, with ST10 being the most common. The isolates showed great diversity of virulence genes and antibiotics resistance profiles. Most of the isolates of this study were grouped into a single cluster composed by 74 STs formed by bovine isolates obtained on the American continent.

Comparative virulence of the worldwide ST19 and emergent ST213 genotypes of Salmonella enterica serotype Typhimurium strains isolated from food

Salmonella enterica Typhimurium represents one of the most frequent causal agents of food contamination associated to gastroenteritis. The sequence type ST19 is the founder and worldwide prevalent genotype within this serotype, but its replacement by emerging genotypes has been recently reported. Particularly, the ST213 genotype has replaced it as the most prevalent in clinical and contaminated food samples in Mexico and has been recently reported in several countries. In this study, the in vitro and in vivo virulence of ST213 and ST19 strains isolated from food samples in Mexico was evaluated. Three out of the five analyzed ST213 strains, showed a greater internalization capacity and increased secretion of interleukins IL-8 and IL-6 of Caco-2 cells than the ST19 strains. Microbiological counts in feces and tissues showed the ability of all strains tested to establish infection in the rat model. The ST213 strains also caused histopathological damage, characteristic of gastroenteritis in Wistar rats. In contrast to the in vitro result, one of the ST19 strains showed marked damage in the test animals. The ST213 genotype strains showed in vitro and in vivo virulence variability, but significantly higher than the observed in the ST19 genotype strains, thus such emergent genotype represents a public health concern.

Comparative Genomic Analysis Discloses Differential Distribution of Antibiotic Resistance Determinants between Worldwide Strains of the Emergent ST213 Genotype of Salmonella Typhimurium

Salmonella enterica constitutes a global public health concern as one of the main etiological agents of human gastroenteritis. The Typhimurium serotype is frequently isolated from human, animal, food, and environmental samples, with its sequence type 19 (ST19) being the most widely distributed around the world as well as the founder genotype. The replacement of the ST19 genotype with the ST213 genotype that has multiple antibiotic resistance (MAR) in human and food samples was first observed in Mexico. The number of available genomes of ST213 strains in public databases indicates its fast worldwide dispersion, but its public health relevance is unknown. A comparative genomic analysis conducted as part of this research identified the presence of 44 genes, 34 plasmids, and five point mutations associated with antibiotic resistance, distributed across 220 genomes of ST213 strains, indicating the MAR phenotype. In general, the grouping pattern in correspondence to the presence/absence of genes/plasmids that confer antibiotic resistance cluster the genomes according to the geographical origin where the strain was isolated. Genetic determinants of antibiotic resistance group the genomes of North America (Canada, Mexico, USA) strains, and suggest a dispersion route to reach the United Kingdom and, from there, the rest of Europe, then Asia and Oceania. The results obtained here highlight the worldwide public health relevance of the ST213 genotype, which contains a great diversity of genetic elements associated with MAR.

Genomic Characterization of Cronobacter spp. and Salmonella spp. Strains Isolated From Powdered Infant Formula in Chile

This study characterized five Cronobacter spp. and six Salmonella spp. strains that had been isolated from 155 samples of powdered infant formula (PIF) sold in Chile and manufactured in Chile and Mexico in 2018–2020. Two strains of Cronobacter sakazakii sequence type (ST) ST1 and ST31 (serotypes O:1 and O:2) and one strain of Cronobacter malonaticus ST60 (O:1) were identified. All Salmonella strains were identified as Salmonella Typhimurium ST19 (serotype O:4) by average nucleotide identity, ribosomal multilocus sequence typing (rMLST), and core genome MLST (cgMLST). The C. sakazakii and C. malonaticus isolates were resistant to cephalothin, whereas the Salmonella isolates were resistant to oxacillin and ampicillin. Nineteen antibiotic resistance genes were detected in the C. sakazakii and C. malonaticus isolates; the most prevalent were mcr-9.1, bla_CSA, and bla_CMA. In Salmonella, 30 genes encoding for aminoglycoside and cephalosporin resistance were identified, including aac(6′)-Iaa, β-lactamases ampH, ampC1, and marA. In the Cronobacter isolates, 32 virulence-associated genes were detected by WGS and clustered as flagellar proteins, outer membrane proteins, chemotaxis, hemolysins, invasion, plasminogen activator, colonization, transcriptional regulator, survival in macrophages, use of sialic acid, and toxin-antitoxin genes. In the Salmonella strains, 120 virulence associated genes were detected, adherence, magnesium uptake, resistance to antimicrobial peptides, secretion system, stress protein, toxin, resistance to complement killing, and eight pathogenicity islands. The C. sakazakii and C. malonaticus strains harbored I-E and I-F CRISPR-Cas systems and carried Col(pHHAD28) and IncFIB(pCTU1) plasmids, respectively. The Salmonella strains harbored type I-E CRISPR-Cas systems and carried IncFII(S) plasmids. The presence of C. sakazakii and Salmonella in PIF is a health risk for infants aged less than 6 months. For this reason, sanitary practices should be reinforced for its production and retail surveillance.

Antimicrobial resistance and virulence genes in Salmonella enterica serovars isolated from droppings of layer chicken in two farms in Nigeria

AIM

This study aimed to investigate the isolation rate, antibiotic resistance, and virulence genes of Salmonella enterica serovar from two commercial farms in Nigeria.

METHODS AND RESULTS

Salmonella isolation was performed according to the United States Food and Drug Agency (USFDA) method. Serotyping, antimicrobial susceptibility testing, detection of resistance and virulence genes were done using the Kauffman-White Scheme, disc diffusion, minimum inhibitory concentration, and real-time polymerase chain reaction techniques. Salmonella serovars were isolated from only farm A at 22/50 (44.0%) while none were isolated from farm B. Salmonella Typhi, 9 (40.9%); Salmonella Typhimurium, 2 (9.1%), Salmonella Enteritidis, 2 (9.1%), Salmonella Pullorum, 1 (4.5%), Salmonella Kentucky, 4 (18.2%) were identified while 4 (18.2%) were untypable. Sixteen isolates (72.7%) showed multiple drug resistance and 17 different resistance profile types with AMP-CHL-TRM-SXT as the most prevalent pattern. Resistance genes (blaTEM, 12/22 (54.5%) and virulence genes (InvA, sopB, mgtC, and spi4D, 22/22 (100.0%), ssaQ, 16/22 (72.7%), and spvC, 13/22 (59.1%) were found, while blaSHV, blaCTX-M, floR, tetA, tetB, tetG, and LJSGI-1 genes were absent.

CONCLUSION

Pathogenic Salmonella were isolated from the chicken droppings in this study. Most of these strains were resistant to antibiotics and possessed characteristics of virulence.

SIGNIFICANCE AND IMPACT OF THE STUDY

Chicken droppings from this study area contained pathogenic strains of Salmonella and a rare occurrence of Salmonella Typhi. The study revealed that the environment and the food chain could be at risk of contamination of highly virulent and antimicrobial-resistant strains of Salmonella. These could affect the profitability of the poultry industry and food consumption. There is a need for caution in indiscriminate disposal of poultry waste and the use of uncomposted chicken droppings in soil amendment.

Virulence Gene Profile, Antimicrobial Resistance and Multilocus Sequence Typing of Salmonella enterica Subsp. enterica Serovar Enteritidis from Chickens and Chicken Products

This study was undertaken to determine the virulence, antimicrobial resistance and molecular subtypes of Salmonella in the Central Region of Peninsular Malaysia. A total of 45 Salmonella Enteritidis were detected from live chicken (cloacal swab), and chicken products (fresh and ready-to-eat meat) samples upon cultural isolation and serotyping. Similarly, an antimicrobial susceptibility test based on the Kirby Bauer disk diffusion method as well as antimicrobial resistance AMR genes, virulence determinants and multilocus sequence typing (MLST) typing were conducted after the Whole Genome Sequencing and analysis of the isolates. The results indicate that sequence types ST1925 (63.7%), and ST11 (26.5%) were the predominant out of the seven sequence types identified (ST292, ST329, ST365, ST423 and ST2132). The phenotypic antimicrobial profile corresponds to the genotypic characterization in that the majority of the isolates that exhibited tetracycline, gentamycin and aminoglycoside resistance; they also possessed the tetC and blaTEM β-Lactam resistance genes. However, isolates from cloacal swabs showed the highest number of resistance genes compared to the chicken products (fresh and ready-to-eat meat) samples. Furthermore, most of the virulence genes were found to cluster in the Salmonella pathogenicity island (SPI). In this study, all the isolates were found to possess SPI-1, which codes for the type III secretion system, which functions as actin-binding proteins (SptP and SopE). The virulence plasmid (VP) genes (spvB, spvC) were present in all genotypes except ST365. The findings of this study, particularly with regard to the molecular subtypes and AMR profiles of the Salmonella Enteritidis serotype shows multidrug-resistance features as well as genetic characteristics indicative of high pathogenicity.

Genomic Characterization of Antimicrobial Resistance in Food Chain and Livestock-Associated Salmonella Species

Simple Summary

In the era of the COVID-19 global pandemic, antimicrobial resistance is looming as an imminent threat and challenge to human public health. Antimicrobial resistance is a major global threat of increasing concern to human and animal health. It also has implications for both food safety and food security and the economic well-being of millions of humans. Among other zoonotic infectious diseases, antimicrobial resistance in food chain and livestock-associated pathogens such as Salmonella is of great concern. In the present study, the genomic characterization of antimicrobial resistance in food chain and livestock-associated Salmonella was summarized. Several antimicrobial resistance determinants were reported in Salmonella isolated from food chain animals and livestock. Monitoring of antimicrobial resistance in Salmonella in livestock and food chain animals through genomic characterization is significant to control and protect humans from the threat of antimicrobial resistance. Salmonella, a foodborne zoonotic enterobacterium species can transmit antimicrobial resistance from the microbiome of animals to humans. This study summarizes the genomic characterization of antimicrobial resistance in Salmonella species with special focus on resistance against carbapenems and colistin which are the last resort antibiotics used against infections caused by multidrug resistant bacteria. The present review aims to draw attention to prudent use of antibiotics, a good example of the One Health concept.

Abstract

The rising trend of antimicrobial resistance (AMR) by foodborne bacteria is a public health concern as these pathogens are easily transmitted to humans through the food chain. Non-typhoid Salmonella spp. is one of the leading foodborne pathogens which infect humans worldwide and is associated with food and livestock. Due to the lack of discovery of new antibiotics and the pressure exerted by antimicrobial resistance in the pharmaceutical industry, this review aimed to address the issue of antibiotic use in livestock which leads to AMR in Salmonella. Much attention was given to resistance to carbapenems and colistin which are the last-line antibiotics used in cases of multi drug resistant bacterial infections. In the present review, we highlighted data published on antimicrobial resistant Salmonella species and serovars associated with livestock and food chain animals. The importance of genomic characterization of carbapenem and colistin resistant Salmonella in determining the relationship between human clinical isolates and food animal isolates was also discussed in this review. Plasmids, transposons, and insertion sequence elements mediate dissemination of not only AMR genes but also genes for resistance to heavy metals and disinfectants, thus limiting the therapeutic options for treatment and control of Salmonella. Genes for resistance to colistin (mcr-1 to mcr-9) and carbapenem (blaVIM-1, blaDNM-1, and blaNDM-5) have been detected from poultry, pig, and human Salmonella isolates, indicating food animal-associated AMR which is a threat to human public health. Genotyping, plasmid characterization, and phylogenetic analysis is important in understanding the epidemiology of livestock-related Salmonella so that measures of preventing foodborne threats to humans can be improved.

Chlorogenic Acid Promotes Autophagy and Alleviates Salmonella Typhimurium Infection Through the lncRNAGAS5/miR-23a/PTEN Axis and the p38 MAPK Pathway

Background

Salmonella typhimurium (ST) causes several intestinal diseases. Polyphenols including chlorogenic acid (CGA) inhibit pathogenesis.

Objective

This study aimed to investigate the mechanisms of CGA in ST infection.

Methods

The intestinal pathological changes and survival rate of ST-infected mice were measured to verify the protection of CGA on ST infection. The antibacterial effects of CGA in vitro on the invasion to intestinal epithelial cells and autophagy was evaluated. The relationships among GAS5, miR-23a, and PTEN were verified. Expression of inflammation- and autophagy-related proteins was detected.

Results

CGA treatment alleviated pathological damage, improved the secretion disturbance of intestinal cytokines caused by ST infection, and reduced the mortality of mice. Intestinal GAS5 was upregulated after CGA treatment. LncRNA GAS5 competitively bound to miR-23a to upregulate PTEN and inhibit the p38 MAPK pathway. CGA regulated the p38 MAPK pathway through lncRNA GAS5/miR-23a/PTEN axis to promote autophagy in ST infection. The functional rescue experiments of miR-23a and PTEN further identified these effects.

Conclusion

CGA promotes autophagy and inhibits ST infection through the GAS5/miR-23a/PTEN axis and the p38 MAPK pathway.

Class 1 integron-borne cassettes harboring blaCARB-2 gene in multidrug-resistant and virulent Salmonella Typhimurium ST19 strains recovered from clinical human stool samples, United States

International lineages, such as Salmonella Typhimurium sequence type (ST) 19, are most often associated with foodborne diseases and deaths in humans. In this study, we compared the whole-genome sequences of five S. Typhimurium strains belonging to ST19 recovered from clinical human stool samples in North Carolina, United States. Overall, S. Typhimurium strains displayed multidrug-resistant profile, being resistance to critically and highly important antimicrobials including ampicillin, ticarcillin/clavulanic acid, streptomycin and sulfisoxazole, chloramphenicol, tetracycline, respectively. Interestingly, all S. Typhimurium strains carried class 1 integron (intl1) and we were able to describe two genomic regions surrounding bla_CARB-2 gene, size 4,062 bp and 4,422 bp for S. Typhimurium strains (HS5344, HS5437, and HS5478) and (HS5302 and HS5368), respectively. Genomic analysis for antimicrobial resistome confirmed the presence of clinically important genes, including bla_CARB-2, aac(6’)-Iaa, aadA2b, sul1, tetG, floR, and biocide resistance genes (qacEΔ1). S. Typhimurium strains harbored IncFIB plasmid containing spvRABCD operon, as well as rck and pef virulence genes, which constitute an important apparatus for spreading the virulence plasmid. In addition, we identified several virulence genes, chromosomally located, while the phylogenetic analysis revealed clonal relatedness among these strains with S. enterica isolated from human and non-human sources obtained in European and Asian countries. Our results provide new insights into this unusual class 1 integron in virulent S. Typhimurium strains that harbors a pool of genes acting as potential hotspots for horizontal gene transfer providing readily adaptation to new surrounds, as well as being crucially required for virulence in vivo. Therefore, continuous genomic surveillance is an important tool for safeguarding human health.

Pathogenicity of clinical Salmonella enterica serovar Typhimurium isolates from Thailand in a mouse colitis model

Salmonella enterica serovar Typhimurium (S. Typhimurium [STM]) is a leading cause of nontyphoidal salmonellosis (NTS) worldwide. The pathogenesis of NTS has been studied extensively using a streptomycin-pretreated mouse colitis model with the limited numbers of laboratory STM strains. However, the pathogenicity of the clinically isolated STM (STMC) strains endemic in Thailand in mice has not been explored. The aim of this study was to compare the pathogenicity of STMC strains collected from Northern Thailand with the laboratory STM (IR715) in mice. Five STMC isolates were obtained from the stool cultures of patients with acute NTS admitted to Maharaj Nakorn Chiang Mai Hospital in 2016 and 2017. Detection of virulence genes and sequence type (ST) of the strains was performed. Female C57BL/6 mice were pretreated with streptomycin sulfate 1 day prior to oral infection with STM. On Day 4 postinfection, mice were euthanized, and tissues were collected to analyze the bacterial numbers, tissue inflammation, and cecal histopathological score. We found that all five STMC strains are ST34 and conferred the same or reduced pathogenicity compared with that of IR715 in mice. A strain-specific effect of ST34 on mouse gut colonization was also observed. Thailand STM ST34 exhibited a significant attenuated systemic infection in mice possibly due to the lack of spvABC-containing virulence plasmid.

Quinolone resistance among Salmonella Kentucky and Typhimurium isolates in Tunisia: first report of Salmonella Typhimurium ST34 in Africa and qnrB19 in Tunisia

AIMS

Characterization of quinolone-resistant Salmonella Kentucky and Typhimurium isolates in Tunisia from various sources, detection of some plasmid-mediated quinolone resistance genes and the genetic relatedness.

METHODS

A total of 1404 isolates of S. Kentucky (n = 1059)/S. Typhimurium (n = 345) from various sources from all over Tunisia were tested for quinolone resistance by disk diffusion method. Minimum inhibitory concentrations of nalidixic acid, ciprofloxacin and ofloxacin were determined. Quinolone-resistant isolates were screened for plasmid-mediated quinolone-resistance genes (qnrA,qnrB,qnrS, aac(6')-Ib-cr and qepA) by polymerase chain reaction (PCR). Mutations in the quinolone-resistance-determining regions of the gyrA and parC genes were detected by PCR and DNA sequencing. Pulsed-field gel electrophoresis and multilocus sequence typing were accomplished for isolates harbouring plasmid-mediated quinolone-resistance genes.

RESULTS

According to our selection criteria (NAL = resistance phenotype; CIP = resistant with diameter 0, or intermediate), only 63 S. Kentucky/41 S. Typhimurium isolates were investigated: 49% (5/104) were multidrug resistant. Two S. Typhimurium isolates harboured qnrB19 with different PFGE profiles. A mutation was detected in the gyrA gene for each of these two isolates. MLST revealed the presence of ST313 and ST34, an endemic sequence type.

CONCLUSION

Our study highlights the presence of quinolone multidrug-resistant Salmonella in humans and animals in Tunisia. This is the first report of S. Typhimurium ST34 in Africa and qnrB19 in Tunisia.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first report that describes not only the current epidemiological situation of the quinolone resistance in S. Kentucky and Typhimurium isolated from various sources and regions in Tunisia, but also, the genetic resistance determinants associated with phenotypic antibiotic resistance and the molecular mechanisms of their quinolone-resistance. Also, we provide the first report of S. Typhimurium ST34 in Africa, and the first report of qnrB19 in Salmonella in Tunisia.

Emergence of NDM-5-Producing Escherichia coli in a Teaching Hospital in Chongqing, China: IncF-Type Plasmids May Contribute to the Prevalence of bla NDM- 5

The newly emerging NDM-5 confers increased antibiotic resistance and attracts extensive global attention, but the prevalence, dissemination mechanism, and clinical significance of NDM-5 among clinical Escherichia coli (E. coli) infections have not been thoroughly characterized to date. In the present study, 109 unique carbapenem-resistant E. coli (CR-EC) isolates were collected in Southwest China, from 2013 to 2017, among which 41 (37.61%) CR-EC isolates were identified as NDM-5-producers, with most isolates carrying the IncF-type plasmids. Molecular epidemiological studies revealed ST167 being the most common sequence type (ST). Moreover, we described the first report of a clinical CR-EC isolate co-harboring bla_KPC–2 and bla_NDM–5, which showed a higher level of resistance to carbapenems. In addition, bla_NDM–5 plasmid transformation and conjugation indicated that bla_NDM–5 itself did confer resistance to carbapenems. Complete sequencing of the bla_NDM–5-harboring IncF plasmid revealed highly conserved regions (ble_MBL-trpF-tat) and some transposons around bla_NDM–5. Our findings revealed a new potential threat of NDM-5-postive CR-EC in mainland China and emphasized an urgent need to control their further spread.

Characterization of non-typhoidal Salmonella isolates from children with acute gastroenteritis, Kolkata, India, during 2000-2016

Non-typhoidal Salmonella (NTS) is an important cause of acute gastroenteritis in children. The study was undertaken to determine the isolation rate, serovar prevalence, antimicrobial resistance (AMR) profiles, and molecular subtypes of NTS from a hospital-based diarrheal disease surveillance in Kolkata, India. Rectal swabs were collected from children (< 5 years of age) with acute gastroenteritis from 2000 to 2016. Samples were processed following standard procedures for identification of NTS. The isolates were tested for antimicrobial susceptibility, AMR genes, plasmid profiles, multilocus sequence typing (MLST), and pulsed-field gel electrophoresis (PFGE) subtypes. A total of 99 (1.0%) Salmonella isolates were recovered from 9957 samples processed. Of the 17 Salmonella serovars identified, S. Worthington (33%) was predominant followed by S. Enteritidis (13%), S. Typhimurium (12%), and others. The isolates showed high resistance towards nalidixic acid (43%), ampicillin (34%), third-generation cephalosporins (32%), and azithromycin (25%), while low resistance was observed for fluoroquinolones (2%). Extended-spectrum beta-lactamase production (bla_CTX-M-15 and bla_SHV-12 genes) and azithromycin resistance (mphA gene) were common in S. Worthington, while fluoroquinolone resistance (gyrA and parC mutations) was found in S. Kentucky. Diverse plasmid profiles were observed among the isolates. PFGE analysis identified genetically related strains of each serovar in circulation. MLST also revealed phylogenetically clonal isolates of which S. Worthington ST592 and ciprofloxacin-resistant S. Kentucky ST198 were not reported earlier from India. NTS resistant to current drugs of choice poses a potential public health problem. Continuous monitoring of AMR profiles and molecular subtypes of NTS serovars is recommended for controlling the spread of resistant organisms.

Antimicrobial Resistance Genes, Cassettes, and Plasmids Present in Salmonella enterica Associated With United States Food Animals

The ability of antimicrobial resistance (AR) to transfer, on mobile genetic elements (MGEs) between bacteria, can cause the rapid establishment of multidrug resistance (MDR) in bacteria from animals, thus creating a foodborne risk to human health. To investigate MDR and its association with plasmids in Salmonella enterica, whole genome sequence (WGS) analysis was performed on 193 S. enterica isolated from sources associated with United States food animals between 1998 and 2011; 119 were resistant to at least one antibiotic tested. Isolates represented 86 serotypes and variants, as well as diverse phenotypic resistance profiles. A total of 923 AR genes and 212 plasmids were identified among the 193 strains. Every isolate contained at least one AR gene. At least one plasmid was detected in 157 isolates. Genes were identified for resistance to aminoglycosides (n = 472), β-lactams (n = 84), tetracyclines (n = 171), sulfonamides (n = 91), phenicols (n = 42), trimethoprim (n = 8), macrolides (n = 5), fosfomycin (n = 48), and rifampicin (n = 2). Plasmid replicon types detected in the isolates were A/C (n = 32), ColE (n = 76), F (n = 43), HI1 (n = 4), HI2 (n = 20), I1 (n = 62), N (n = 4), Q (n = 7), and X (n = 35). Phenotypic resistance correlated with the AR genes identified in 95.4% of cases. Most AR genes were located on plasmids, with many plasmids harboring multiple AR genes. Six antibiotic resistance cassette structures (ARCs) and one pseudo-cassette were identified. ARCs contained between one and five resistance genes (ARC1: sul2, strAB, tetAR; ARC2: aac3-iid; ARC3: aph, sph; ARC4: cmy-2; ARC5: floR; ARC6: tetB; pseudo-ARC: aadA, aac3-VIa, sul1). These ARCs were present in multiple isolates and on plasmids of multiple replicon types. To determine the current distribution and frequency of these ARCs, the public NCBI database was analyzed, including WGS data on isolates collected by the USDA Food Safety and Inspection Service (FSIS) from 2014 to 2018. ARC1, ARC4, and ARC5 were significantly associated with cattle isolates, while ARC6 was significantly associated with chicken isolates. This study revealed that a diverse group of plasmids, carrying AR genes, are responsible for the phenotypic resistance seen in Salmonella isolated from United States food animals. It was also determined that many plasmids carry similar ARCs.