Salmonella enterica serovar Kentucky recovered from human clinical cases in Maryland,USA (2011–2015)

Salmonella Kentucky is among the most frequently isolated S. enterica serovars from food animals in the United States. Recent research on isolates recovered from these animals suggests there may be geographic and host specificity signatures associated with S. Kentucky strains. However, the sources and genomic features of human clinical S. Kentucky isolated in the United States remain poorly described. To investigate the characteristics of clinical S. Kentucky and the possible sources of these infections, the genomes of all S. Kentucky isolates recovered from human clinical cases in the State of Maryland between 2011 and 2015 (n = 12) were sequenced and compared to a database of 525 previously sequenced S. Kentucky genomes representing 12 sequence types (ST) collected from multiple sources on several continents. Of the 12 human clinical S. Kentucky isolates from Maryland, nine were ST198, two were ST152, and one was ST314. Forty‐one per cent of isolates were recovered from patients reporting recent international travel and 58% of isolates encoded genomic characteristics similar to those originating outside of the United States. Of the five isolates not associated with international travel, three encoded antibiotic resistance genes conferring resistance to tetracycline or aminoglycosides, while two others only encoded the cryptic aac(6′)‐Iaa gene. Five isolates recovered from individuals with international travel histories (ST198) and two for which travel was not recorded (ST198) encoded genes conferring resistance to between 4 and 7 classes of antibiotics. Seven ST198 genomes encoded the Salmonella Genomic Island 1 and substitutions in the gyrA and parC genes known to confer resistance to ciprofloxacin. Case report data on food consumption and travel were, for the most part, consistent with the inferred S. Kentucky phylogeny. Results of this study indicate that the majority of S. Kentucky infections in Maryland are caused by ST198 which may originate outside of North America.     

Antimicrobial susceptibility and multi-drug resistance of Salmonella enterica subspecies enterica serovars in Sudan

This study was undertaken to determine the antimicrobial resistance patterns of Salmonella enterica subspecies enterica recovered from human, food, water, and animal samples collected in Khartoum State, Sudan. A total of 64 Salmonella isolates belonging to 28 different serovars were tested for their susceptibility to 13 antimicrobial agents. The majority of isolates (98.4 %) were resistant to at least one antimicrobial agent. Isolates were frequently resistant to ampicillin (90.6 %), cephalexin (50.0 %), nalidixic acid (25.0 %), streptomycin (21.9 %), kanamycin (18.8 %), gentamicin (17.2 %), and co-trimoxazole and trimethoprim (12.5 %). The most common pattern of multiple drug resistance included resistance to ampicillin and cephalexin. Most isolates were sensitive to chloramphenicol (98.4 %), ciprofloxacin (93.8 %), and norfloxacin (90.6 %). Two chicken- and the two human-origin S. Kentucky isolates were resistant to both ciprofloxacin and norfloxacin. All S. Kentucky isolates and the one S. Rissen isolate demonstrated multi-drug resistance. The results indicate the significance of multi-drug-resistant Salmonella serovars isolated from chickens and other animals and foods as sources for multi-drug-resistant Salmonella in humans in Sudan.     

Poultry as a possible source of non-typhoidal Salmonella enterica serovars in humans in Bangladesh

We investigated Salmonella enterica isolates from human clinical cases of gastroenteritis to determine the distribution of non-typhoidal Salmonella serovars in the human population, and compared them to isolates originating from poultry by serotyping, phage typing, plasmid profiling, pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST) to evaluate the potential role of poultry in human non-typhoidal salmonellosis in Bangladesh. Nine different serovars were identified among the human isolates of which Salmonella Paratyphi B var Java (S. Java), S. Kentucky, S. Enteritidis, S. Virchow and S. Weltevreden also were commonly isolated from poultry. The poultry isolates belonging to S. Java, S. Kentucky and S. Enteritidis were indistinguishable from human isolates or genetically closely related, based on PFGE profiles and MLST. S. Kentucky clone ST198 and S. Java clone ST43 both well-known cause of human infections were also isolated from poultry.     

Detection and Molecular Characterization of Salmonella enterica Serovar Eppendorf Circulating in Chicken Farms in Tunisia

Salmonella enterica subsp. enterica serovar Eppendorf, with antigenic formula 1,4,12,[27]:d:1,5, is an infrequent serovar. However, 14% (20 of 142) of the isolates recovered during June–July 2012 in chicken farms in Tunisia belonged to S. Eppendorf. These isolates were analysed for resistance and virulence profiles. None of them were susceptible to all antimicrobials tested, while 70%, 60%, 50%, 50%, 20% and 5% were resistant to sulphonamides (sul1, sul2 and sul3), streptomycin (aadA1‐like), trimethoprim (dfrA1‐like), nalidixic acid (GyrA Asp₈₇→Asn and not identified), gentamicin (not identified) and ampicillin (bla_TEM‐1‐like). About 30% of the isolates showed decreased susceptibility to ciprofloxacin and carried the qnrB gene; 65% of the isolates were multidrug resistant and contained class 1 integrons with sul1 or sul3 in the 3′ conserved segment. The orgA, ssaQ, mgtC, siiD and sopB virulence genes located on SPI1 to SPI5 and the fimbrial bcfC gene were present in all isolates; the sopE1 and sodC1 carried by prophages were variably detected; however, the prophage gipA gene and the spvC gene of serovar‐specific virulence plasmids were absent. Altogether, ten resistance and three virulence profiles were identified. Typing of the isolates with XbaI‐ and BlnI‐PFGE supports a close relationship, although they appear to be evolving under selective pressure probably caused by antimicrobial use in chicken husbandry. As far as we know, this is the first study investigating the molecular bases of antimicrobial drug resistance, the virulence gene content and the PFGE profiles of S. Eppendorf. The epidemiological surveillance of this serovar would be necessary to evaluate its possible impact on human health, particularly in Tunisia and other African countries where it was already reported.     

Highly ciprofloxacin resistant Salmonella enterica serovar Kentucky isolates in turkey meat and a human patient

In recent years in France, England, Wales, Denmark and the USA about 500 human infections occurred, which were caused by multidrug-resistant Salmonella enterica Serovar (S.) Kentucky isolates displaying high-level resistance to fluoroquinolones (ciprofloxacin, MIC > or = 4 mg/l). The responsible clone was referred to as ST198-X1.To determine whether this clone is also present in German S. Kentucky isolates, the National Reference Laboratory for Salmonella (NRL-Salm) at the BfR analyzed the trend of S. Kentucky isolates received over the past years. Since 2010 the first entries of highly ciprofloxacin resistant S. Kentucky isolates, especially from turkey meat products, were recorded. 15 isolates originating from animal or food as well as one human isolate displayed MIC values of > or = 8 mg/l to ciprofloxacin. Molecular biological typing methods showed the in Germany isolated S. Kentucky isolates to be identical to the clone described by Le Hello et al. (2011) and to carry a multidrug resistance conferring region (SGI1). Since fluoroquinolones are considered by the WHO in human and veterinary medicine as drugs of critical importance, this trend demands attention. The implementation of mitigation strategies for this highly resistant clone seems to be required.     

Detection of mutations in the gyrA gene and class I integron from quinolone-resistant Salmonella enterica serovar Choleraesuis isolates in Taiwan

The quinolone resistance-determining regions (QRDRs) of the gyrA gene of quinolone-resistant Salmonella enterica serovar Choleraesuis isolates were sequenced. Four types of point mutation, Ser-83-to-Phe (TCC→TTC), Ser-83-to-Tyr (TCC→TAC), Asp-87-to-Gly (GAC→GGC), and Asp-87-to-Asn (GAC→AAC), were found. PCR-RFLP and MAS-touch down PCR were performed on fifty swine clinical isolates of S. enterica serovar Choleraesuis (Nal^R) collected during 1997–2002. The analysis indicated seven isolates with point mutations in codon 83, 13 with point mutations in codon 87, and 30 with double mutations in both codons 83 and 87. The MICs of enrofloxacin of the isolates with a single mutation in codon 83 or 87 were <2 μg/ml, while the MICs of the isolates with double mutations in both codon 83 and 87 ranged from 2 to 64 μg/ml. A class I integron comprised of dhfr, orfF and aad2 was also identified in both human and swine S. enterica serovar Choleraesuis isolates. These results indicate that PCR-RFLP and MAS-touchdown PCR assays can be used for surveillance of gyrA gene mutations, which are important for fluoroquinolone resistance in Salmonella. Isolates with double mutations in gyrA codons 83 and 87 are the major type of quinolone-resistant Salmonella isolated from swine in Taiwan. A surveillance system may be applied to the swine industry to monitor the emergence of fluoroquinolone and/or multi-drug-resistant S. enterica serovar Choleraesuis in Taiwan.     

Changes in the prevalence of Salmonella serovars associated swine production and correlations of avian,bovine and swine‐associated serovars with human‐associated serovars in the United States (1997–2015)

As Salmonella enterica is an important pathogen of food animals, surveillance programmes for S. enterica serovars have existed for many years in the United States. Surveillance programmes serve many purposes, one of which is to evaluate alterations in the prevalence of serovars that may signal changes in the ecology of the target organism. The primary aim of this study was to evaluate changes in the proportion of S. enterica serovars isolated from swine over a near 20‐year observation period (1997–2015) using four longitudinal data sets from different food animal species. The secondary aim was to evaluate correlations between changes in S. enterica serovars frequently recovered from food animals and changes in S. enterica serovars associated with disease in humans. We found decreasing proportions of S. enterica serovar Typhimurium, serovar Derby and serovar Heidelberg and increasing proportions of S. enterica serovar 4,[5],12:i:‐, serovar Infantis and serovar Johannesburg in swine over time. We also found positive correlations for the yearly changes in S. enterica serovar 4,[5],12:i:‐, serovar Anatum and serovar Johannesburg between swine and human data; in S. enterica Worthington between avian and human data; and in S. enterica serovar 4,[5],12:i:‐ between bovine and human data. We found negative correlations for the yearly changes in S. enterica serovar 4,[5],12:i:‐ and serovar Johannesburg between avian and human data.     

Comparative Phenotypic and Genotypic Analyses of Salmonella Rissen that Originated from Food Animals in Thailand and United States

Salmonella enterica serovar Rissen has been recognized as one of the most common serovar among humans and pork production systems in different parts of the world, especially Asia. In the United States, this serovar caused outbreaks but its epidemiologic significance remains unknown. The objectives of this study were to compare the phenotypic (antimicrobial susceptibility) and genotypic attributes of Salmonella Rissen isolated in Thailand (Thai) and the United States (US). All the Thai isolates (n = 30) were recovered from swine faecal samples. The US isolates (n = 35) were recovered from swine faecal samples (n = 29), cattle (n = 2), chicken (n = 2), dog (n = 1) and a ready‐to‐eat product (n = 1). The antimicrobial susceptibility of isolates was determined using the Kirby‐Bauer disk diffusion method with a panel of 12 antimicrobials. Pulse‐field gel electrophoresis (PFGE) was used to determine the genotypic diversity of isolates. All Thai isolates showed multidrug resistance (MDR) with the most frequent antibiotic resistance shown against ampicillin (100%), sulfisoxazole (96.7%), tetracycline (93.3%), streptomycin (90%) and chloramphenicol (30%). About half of the isolates of USA origin were pan‐susceptible and roughly 30% were resistant to only tetracycline (R‐type: Te). Salmonella Rissen isolated from Thailand and the USA in this study were found to be clonally unrelated. Genotypic analyses indicated that isolates were clustered primarily based on the geographic origin implying the limited clonality among the strains. Clonal relatedness among different host species within the same geography (USA) was found. We found genotypic similarity in Thai and US isolates in few instances but with no epidemiological link. Further studies to assess propensity for increased inter‐regional transmission and dissemination is warranted.     

Phenotypic and Genotypic Characterization of Salmonella enterica in Captive Wildlife and Exotic Animal Species in Ohio,USA

The purpose of this study was to investigate the occurrence, antimicrobial resistance patterns, phenotypic and genotypic relatedness of Salmonella enterica recovered from captive wildlife host species and in the environment in Ohio, USA. A total of 319 samples including faecal (n = 225), feed (n = 38) and environmental (n = 56) were collected from 32 different wild and exotic animal species in captivity and their environment in Ohio. Salmonellae were isolated using conventional culture methods and tested for antimicrobial susceptibility with the Kirby–Bauer disc diffusion method. Salmonella isolates were serotyped, and genotyping was performed using the pulsed‐field gel electrophoresis (PFGE). Salmonella was detected in 56 of 225 (24.9%) faecal samples; six of 56 (10.7%) environmental samples and six of 38 (15.8%) feed samples. Salmonella was more commonly isolated in faecal samples from giraffes (78.2%; 36/46), cranes (75%; 3/4) and raccoons (75%; 3/4). Salmonella enterica serotypes of known public health significance including S. Typhimurium (64.3%), S. Newport (32.1%) and S. Heidelberg (5.3%) were identified. While the majority of the Salmonella isolates were pan‐susceptible (88.2%; 60 of 68), multidrug‐resistant strains including penta‐resistant type, AmStTeKmGm (8.8%; six of 68) were detected. Genotypic diversity was found among S. Typhimurium isolates. The identification of clonally related Salmonella isolates from environment and faeces suggests that indirect transmission of Salmonella among hosts via environmental contamination is an important concern to workers, visitors and other wildlife. Results of this study show the diversity of Salmonella serovars and public health implications of human exposure from wildlife reservoirs.     

Prevalence of Salmonella spp. in Cane Toads (Bufo marinus) from Grenada,West Indies,and their Antimicrobial Susceptibility

Cloacal swabs and caecal contents sampled from 58 cane toads (Bufo marinus) in St George’s parish, Grenada, during a 7‐month period in 2011 were examined by an enrichment and selective culture method for presence of Salmonella spp. Twenty‐four (41%) toads were positive for Salmonella spp. of which eight were Salmonella enterica serovar Javiana, and eight were S. enterica serovar Rubislaw. The other serovars were as follows: Montevideo, 6; Arechavaleta, 1; and serovar: IV:43:‐:‐, 1. The high frequency of isolation of serovar Javiana, an emerging human pathogen associated with several outbreaks in the recent years in the eastern United States, suggests a possible role for cane toads in transmission of this serovar. Although S. Rubislaw has been isolated from lizards, bats and cases of some human infections, there is no report of its carriage by cane toads, and in such high frequency. The rate of carriage of S. Montevideo, a cause for human foodborne outbreaks around the world was also over 10% in the 58 toads sampled in this study. The antimicrobial drug susceptibility tests against amoxicillin‐clavulanic acid, ampicillin, cefotaxime, ceftazidime, ciprofloxacin, enrofloxacin, gentamicin, imipenem, nalidixic acid, streptomycin, tetracycline and trimethoprim‐sulfamethoxazole showed that drug resistance is minimal and is of little concern. Antimicrobial resistance was limited to ampicillin and amoxicillin‐clavulanic acid in one isolate of S. Javiana and one isolate of S. Rubislaw. This is the first report of isolation and antimicrobial susceptibilities of various Salmonella serovars not identified previously in cane toads in Grenada, West Indies.     

Resistance phenotypes and genotypes among multiple-antimicrobial-resistant Salmonella enterica subspecies enterica serovar Choleraesuis strains isolated between 2008 and 2012 from slaughter pigs in Okinawa Prefecture,Japan

A total of 349 Salmonella enterica subspecies enterica serovar Choleraesuis (S. Choleraesuis) strains, which were isolated between 2008 and 2012 from 349 pigs at two slaughterhouses in Okinawa Prefecture, Japan, were investigated for antimicrobial susceptibility and the presence of antimicrobial resistance genes. All isolates were resistant to at least four antimicrobial agents. The antimicrobial agents for which isolates showed a high incidence of resistance were as follows: ampicillin (100%) and streptomycin (100%), followed by gentamicin (99.7%), oxytetracycline (99.7%), sulfamethoxazole/trimethoprim (99.4%), nalidixic acid (40.1%) and oxolinic acid (40.1%). All isolates were sensitive to cefuroxime, ceftiofur, colistin, fosfomycin, enrofloxacin, orbifloxacin and danofloxacin. The predominant resistance phenotypes and genotypes were: resistance to ampicillin, streptomycin, gentamicin, oxytetracycline and sulfamethoxazole/trimethoprim (58.5%, 204/349) and blaTEM-strA-strB-aadA1-aadA2-aacC2-tet (B)-sul1-sul2-dhfrXII-dhfrXIII (36.1%, 126/349). The quinolone resistance-determining regions (QRDRs) of gyrA, gyrB, parC and parE of the quinolone-resistant isolates (n=12) showed amino acid substitutions of Ser-83→Phe or Asp-87→Tyr in GyrA and Ser-107→Ala in ParC. To our knowledge, this is the first report on the molecular characterization of antimicrobial resistance among S. Choleraesuis strains in Japan.     

Multidrug‐Resistant Outbreak‐Associated Salmonella Strains in Irrigation Water from the Metropolitan Region,Chile

Salmonella enterica (S. enterica) is the main cause of foodborne diseases in the Chilean population. With the aim of characterizing the presence of S. enterica in bodies of water, samples from 40 sources were obtained, including rivers and irrigation canals used by agricultural farms in the most populated regions of Chile. As result, 35 S. enterica isolates belonging to several serotypes were detected, with the highest frequency represented by Typhimurium and Enteritidis. All strains showed phenotypic antimicrobial resistance, and most of them were multiresistant to critically important antimicrobials. In addition, the pulse‐field gel electrophoresis analysis using XbaI and BlnI endonucleases showed that seven Salmonella isolates belonging to serotypes Typhimurium, Enteritidis and Infantis had identical pulsotypes to outbreak‐associated clinical isolates detected in the Chilean population, suggesting a public health risk of water pollution in this region. Among sampling sites, the higher detection rates were observed in rural than urban and peri‐urban areas, suggesting that the animal husbandry might contribute for environmental dispersion of this pathogen. Future efforts should address the characterization of cause‐and‐effect relationship between water contamination and foodborne disease, including the implementation of surveillance programmes to tackle potential risks for both human and animal populations.     

Evaluation of Salmonella enterica serovar Typhimurium and Choleraesuis slyA mutant strains for use in live attenuated oral vaccines

SlyA protein plays a key role in virulence in Salmonella enterica. In this study, we evaluated the ability of the slyA mutant strain of S. enterica serovar Choleraesuis (S. choleraesuis) to protect against swine salmonellosis. Using a murine model infected with S. enterica serovar Typhimurium (S. typhimurium), we showed that the Salmonella strain with a deletion of slyA could be used as a highly immunogenic, effective and safe vaccine in mice. Based on these data, a slyA mutant of S. enterica serovar Choleraesuis strain RF-1 was constructed, and the ability of this mutant to protect immunized pigs from S. choleraesuis infection was examined. As with the S. typhimurium slyA mutant, immunization of pigs with the S. choleraesuis slyA mutant strain provided significant protection against subsequent challenge by the wild-type RF-1. These results demonstrate that SlyA is a potential target in the development of a novel live attenuated vaccine against S. enterica.     

Multiple clones and low antimicrobial resistance rates for Salmonella enterica serovar Infantis populations in Greece

All the Salmonella enterica ser. Infantis strains isolated under official control programs in Greece during a four year period were studied, 23 of human origin, 16 from food animals and one from food. Molecular analyses (PFGE) in combination with antimicrobial susceptibility testing were used to study whether the occurrence S. Infantis in Greece resulted from different biotypes or a successful spread of one clone. Low rates of antimicrobial resistance were observed, except for streptomycin among human isolates (48%), indicating that selective pressure due to consumption of antimicrobials has not resulted the spread of dominant clones. Pulsed Field Gel Electrophoresis revealed 31 XbaI distinct pulsotypes among the 40 strains with 60% overall similarity reflecting diversity. Four main clusters were constructed, using an 85% cut off value, clusters A, B, C and D consisting of 14, 6, 8 and 8 isolates respectively. Point source of transmission was not hypothesized as multiple reservoirs of the serovar seem to be present in Greece during the study period.     

Phenotypic and genetic characterization of Salmonella enterica subsp. enterica serovar Typhimurium isolated from pigs in Rio Grande do Sul,Brazil

This study aimed to investigate the relatedness of porcine Salmonella enterica subsp. enterica (S.) serovar Typhimurium strains isolated in Southern Brazil. Sixty-six isolates from pigs belonging to three commercial companies were submitted to phage typing, XbaI-macrorestriction (PFGE), IS200 hybridization, rep-PCR, antimicrobial susceptibility testing, and PCR assay targeting the spvR region. All strains presented a unique rep-PCR pattern and 63 strains had a common IS200 profile. One pulse-type (XA) was the most prevalent (39/66 strains) and included strains of phage types DT177, DT192, DT194 and RDNC. The spvR region was detected in three strains, which harboured plasmids of 90 kb. High rates of tetracycline, sulfonamide and streptomycin resistance were found. Isolates from farms located in different geographic regions but associated to the same commercial companies clustered together and presented a common resistance profile. Results suggested that clonal groups of S. Typhimurium are present in pig commercial companies in Southern Brazil.     

Multilocus Sequence Types of Environmental Campylobacter jejuni Isolates and their Similarities to those of Human,Poultry and Bovine C. jejuni Isolates

In this study, we investigated the multilocus sequence type (MLST) diversity and population genetics of Campylobacter jejuni isolates collected from the natural waters (n = 57), wild birds (n = 37) and zoo animals (n = 19) in southern Finland, the Helsinki area and the Helsinki Zoo, respectively. On average, we found C. jejuni in 20%, 10.4% or 11.5% of the samples collected from natural waters, wild birds and zoo animals, respectively. High ST diversity was detected in all three sources and 41.2% of the STs were novel, but the multi‐host adapted ST‐45 was the most common ST detected. The MLST data, supplemented with C. jejuni isolates from domestically acquired human infections (n = 454), poultry (n = 208) and bovines (n = 120), were utilized in a population structure study. The results indicate four groups of strains with varying ecological associations, demonstrating presence of genetically distinct lineages within each of the studied sources. We discovered that the greatest ST overlap occurs between human isolates and isolates from natural waters and poultry, which suggests that the latter two are the most important sources of C. jejuni among domestically acquired infections in Finland.     

Prevalence,Serovars and Antimicrobial Susceptibility of Salmonella spp. from Wild and Domestic Green Iguanas (Iguana iguana) in Grenada,West Indies

Cloacal swabs from 62 green iguanas (Iguana iguana), including 47 wild and 15 domestic ones from five parishes of Grenada, were sampled during a 4‐month period of January to April 2013 and examined by enrichment and selective culture for the presence of Salmonella spp. Fifty‐five per cent of the animals were positive, and eight serovars of Salmonella were isolated. The most common serovar was Rubislaw (58.8%), a serovar found recently in many cane toads in Grenada, followed by Oranienburg (14.7%), a serovar that has been causing serious human disease outbreaks in Japan. Serovar IV:48:g,z₅₁:‐ (formerly, S. Marina) highly invasive and known for serious infections in children in the United States, constituted 11.8% of the isolates, all of them being from domestic green iguanas. Salmonella Newport, a serovar recently found in a blue land crab in Grenada, comprised 11.8% of the isolates from the green iguanas. The remaining four less frequent serovars included S. Javiana and S. Glostrup. Antimicrobial susceptibility tests conducted by a disc diffusion method against amoxicillin–clavulanic acid, ampicillin, cefotaxime, ceftazidime, ciprofloxacin, enrofloxacin, gentamicin, nalidixic acid, streptomycin, tetracycline and trimethoprim–sulfamethoxazole showed that drug resistance is minimal, with intermediate susceptibility, mainly to streptomycin, tetracycline and cefotaxime. This is the first report of isolation and antimicrobial susceptibilities of various Salmonella serovars from wild and domestic green iguanas in Grenada, West Indies.     

Characterization of Salmonella enterica serovar Typhimurium and Salmonella enterica serovar 4,[5],12:i:- isolates from pigs presenting with diarrhea in Korea

Between 2011 and 2012, a total of 896 pig fecal samples were collected from nine provinces in Korea, and 50 salmonella enterica susp. enterica serovar Typhimurium (S. Typhimurium) was isolated. The characteristics of the 50 strains were analyzed, and 4 strains were identified as Salmonella enterica subsp. enterica serovar 4,[5],12:i:-. Salmonella 4,[5],12:i:- could not be distinguished from S. Typhimurium through phage typing, antimicrobial resistance testing or multiple-locus variable-number tandem repeat analysis (MLVA). However, among the four Salmonella 4,[5],12:i:- strains, one (KVCC-BA1400078) was identified as a Salmonella 4,[5],12:i:- clone isolated from humans in the United States, and another (KVCC-BA1400080) was identified as DT193, which has been primarily isolated from humans and animals in European countries. The presence of Salmonella 4,[5],12:i:- in Korea poses a significant threat of horizontal transfer between pigs and humans.     

Prevalence and characterization of multidrug resistance and variant Salmonella genomic island 1 in Salmonella isolates from cattle,poultry and humans in Iran

Salmonella enterica is a common food‐borne pathogen with occasional multidrug resistance (MDR). Salmonella genomic island (SGI1) is a horizontally transmissible genomic island, containing an MDR gene cluster. All Salmonella serotypes are public health concern, although there is an additional concern associated with those that harbour SGI1. In Iran, there are no data on the presence of SGI1 variants in Salmonella isolates. The present study was conducted to identify MDR‐ and SGI1‐carrying Salmonella strains isolated from various sources and to compare their genetic relatedness between human and animal sources. In total, 242 Salmonella isolates collected from chicken, cattle, and humans from 2008 through 2014 were studied. The isolates were tested for resistance to 14 antimicrobials via the disc diffusion method. They were also tested for the presence of SGI1 variants via PCR, and genetic relatedness was evaluated based on pulsed‐field gel electrophoresis (PFGE). Resistance to at least one antimicrobial agent was observed in 132 (54%) Salmonella isolates (n = 242), while more than 40% of the isolates showed MDR. Based on PCR analysis, eight variants of SGI1, including SGI1, SGI1‐B, SGI1‐C, SGI1‐D, SGI1‐F, SGI1‐I, SGI1‐J and SGI1‐O, were found in both human and animal isolates. Statistical analysis revealed no significant difference in the prevalence of SGI1 variants between human and animal isolates (p > 0.05). Macrorestriction PFGE analysis of the isolates with the same SGI1 variant and resistance patterns revealed genetic relatedness ranging from 70% to 100% among human and animal isolates. According to our review, this is the first documentation of SGI1 in Salmonella isolates in Iran. The presence of similar SGI1 variants in both humans and animals, along with their related PFGE patterns, suggests that food‐producing animals may be a source of MDR Salmonella isolates in Iran.