Resistance to Sulfonamides and Dissemination ofsulGenes AmongSalmonellaspp. Isolated from Food in Poland

Detection of Salmonella Pathogenicity Islands and Antimicrobial-Resistant Genes in Salmonella enterica Serovars Enteritidis and Typhimurium Isolated from Broiler Chickens

Rapid growth in commercial poultry production is one of the major sources of Salmonella infections that leads to human salmonellosis. The two main Salmonella enterica serovars associated with human salmonellosis are enteritidis and typhimurium. The aim of this study was to determine the prevalence of S. enterica serovars Enteritidis and S. Typhimurium as well as their Salmonella pathogenicity islands (SPI) and antibiotic resistance profiles in broiler chicken feces from slaughterhouses. A total of 480 fecal samples from broiler chickens that were grouped into 96 pooled samples were identified to have Salmonella spp. using the invA gene, whilst the Spy and sdfI genes were used to screen for the presence of S. Enteritidis and S. Typhimurium serovars, respectively, by polymerase chain reaction (PCR) assays. The isolates were also screened for the presence of Salmonella pathogenicity islands (SPIs) using PCR. The disc diffusion assay was performed to determine the antibiotic resistance profiles of the isolates. A total of 36 isolates were confirmed as Salmonella spp. through amplification of the invA gene. Out of 36 confirmed Salmonella spp. a total of 22 isolates were classified as S. Enteritidis (n = 8) and were S. Typhimurium (n = 14) serovars. All (n = 22) S. Enteritidis and S. Typhimurium isolates possessed the hilA (SPI-1), ssrB (SPI-2) and pagC (SPI-11) pathogenicity islands genes. Amongst these serovars, 50% of the isolates (n = 11/22) were resistant to tetracycline and nalidixic acid. Only 22% of the isolates, S. Typhimurium (13.6%) and S. Enteritidis (9.1%) demonstrated resistance against three or more antibiotic classes. The most detected antibiotic resistance genes were tet(K), mcr-1, sulI and strA with 13 (59.1%), 9 (40.9%), 9 (40.9%) and 7 (31.8%), respectively. The findings of this study revealed that S. Typhimurium is the most prevalent serotype detected in chicken feces. To reduce the risk to human health posed by salmonellosis, a stringent public health and food safety policy is required.

Antibiotic resistance genes and heavy metals in landfill: A review

Landfill is reservoir containing antibiotic resistance genes (ARGs) that pose a threat to human life and health. Heavy metals impose lasting effects on ARGs. This review investigated and analyzed the distribution, composition, and abundance of heavy metals and ARGs in landfill. The abundance ranges of ARGs detected in refuse and leachate were similar. The composition of ARG varied with sampling depth in refuse. ARG in leachate varies with the distribution of ARG in the refuse. The ARG of sulI was associated with 11 metals (Co, Pb, Mn, Zn, Cu, Cr, Ni, Sb, As, Cd, and Al). The effects of the total metal concentration on ARG abundance were masked by many factors. Low heavy metal concentrations showed positive effects on ARG diffusion; conversely, high heavy metal concentrations showed negative effects. Organic matter had a selective pressure effect on microorganisms and could provide energy for the diffusion of ARGs. Complexes of heavy metals and organic matter were common in landfill. Therefore, the hypothesis was proposed that organic matter and heavy metals have combined effects on the horizontal gene transfer (HGT) of ARGs during landfill stabilization. This work provides a new basis to better understand the HGT of ARGs in landfill.

Genetic- and Fiber-Diet-Mediated Changes in Antibiotic Resistance Genes in Pig Colon Contents and Feces and Their Driving Factors

Comprehensive studies on the effects of genetics and fiber diets on antibiotic resistance genes (ARGs) remain scarce. In this study, we analyzed the profiles of ARGs in colonic contents and fecal samples of Taoyuan, Duroc, and Xiangcun pigs (n = 10) fed at different fiber levels. Through macrogenomic analysis, we identified a total of 850 unique types of ARGs and classified them into 111 drug resistance classes. The abundance of partially drug-resistant ARGs was higher in the colonic contents of local pig breeds under a large-scale farming model. ARGs were found to be widely distributed among a variety of bacteria, predominantly in the phyla Firmicutes, Proteobacteria, and Bacteroidetes. Fiber diets reduce the abundance of ARGs in colonic contents and feces, and mobile genetic elements (MGEs) and short-chain fatty acids (SCFAs) are important drivers in mediating the effect of fiber diets on the abundance of ARGs. In vitro fermentation experiments confirmed that butyric acid significantly reduced the abundance of ARGs. In summary, the results of this study enhanced our understanding of the distribution and composition of ARGs in the colon of different breeds of pigs and revealed that a fiber diet can reduce ARGs in feces through its Butyric acid, providing reference data for environmental safety.

Prevalence and Antimicrobial Resistance of Salmonella spp. Isolated From Chilled Chicken Meat Commercialized at Retail in Federal District, Brazil

Salmonella represents one of the most common foodborne pathogens, frequently associated with the contamination of poultry products, constituting a prominent worldwide public health concern. This study determined the prevalence and antimicrobial resistance of Salmonella spp. in chilled chicken meat (115 samples) commercialized at retail in the Federal District, Brazil. Microbiological tests were performed to screen for Salmonella spp. in the chicken meat samples, and the isolated strains were confirmed by the invA gene presence (PCR technique). The strains were evaluated for antimicrobial susceptibility by the disk diffusion technique (Kirby-Bauer method) and tested for the presence of the sul2, blaCTX, and tetB antimicrobial resistance genes. The Salmonella spp. prevalence in chilled chicken meat sold at retail in the Federal District, Brazil, was 46.1% (53 of 115 chicken meat samples analyzed had invA gene-positive strains). Seventy-eight strains of Salmonella spp. isolated from the 53 contaminated samples showed higher resistance to amoxicillin/clavulanic acid (83.3%), followed by sulfonamide (64.1%) and tetracycline (46.2%); 53.8% of the isolates were multidrug-resistant (MDR). The sul2 gene that confers resistance to sulfonamide was found in 53 strains (68.0%), the blaCTX gene that confers resistance to beta-lactams was identified in 39 strains (50.0%), and the tetB gene that confers resistance to tetracycline was identified in 29 strains (37.2%). The high percentage of Salmonella contamination in chicken meat can pose a risk to consumers' health due to the possibility of causing salmonellosis. In addition, many isolates were MDR and carried antimicrobial resistance genes. Public agencies can use these results to develop effective public health policies and strategies to ensure the safety of these food products.

Antibiotic profiling of multidrug resistant pathogens in one-day-old chicks imported from Belgium to benin

BACKGROUND

Little data exist on the presence of resistant pathogens in day-old chicks imported into Benin. The occurrence of pathogenic bacteria was assessed in 180 one-day-old chicks imported from Belgium and received at the Cardinal Bernardin Gantin International Airport in Cotonou (Benin). The samples included swabbing the blisters of 180 chicks, followed by 18 pools of 10 swabs for bacterial isolation. Classic bacteriological methods based on Gram staining, culture on specific media and biochemical characterization were used. Antibacterial susceptibility screening to antibiotics was conducted using the Kirby-Bauer disc diffusion method, and the results were interpreted according to guidelines from the European Committee on Antimicrobial Susceptibility Testing (EUCAST). DNA extraction was performed by the heat treatment method. Resistance genes were screened by real-time PCR.

RESULTS

We isolated 32 bacteria, including Escherichia coli (50%), Enterococcus spp. (28%), and coagulase-negative staphylococci (10%). The isolates were investigated for antibiotic resistance against antibiotics using the disk diffusion method and showed that in the Escherichia coli strains isolated, the highest rate of resistance was obtained against ciprofloxacin (81%), followed by trimethoprim + sulfamethoxazole (62%). Enterobacter cloacae was sensitive to all the antibiotics tested. Pseudomonas spp. resistant to amoxicillin and trimethoprim + sulfamethoxazole was noted. The SulII gene was found in all cloacal samples, while the SulI and bla_TEM genes were present at 44.44% and 16.67%, respectively.

CONCLUSION

This study confirms that imported day-old chicks can be a potential source of dissemination of resistant bacteria in poultry production. A system for immediate detection of resistant bacteria in chicks upon arrival in the country is thus needed.

Evolution of trimethoprim/sulfamethoxazole resistance in Shewanella algae from the perspective of comparative genomics and global phylogenic analysis

OBJECTIVE

Shewanella algae is a zoonotic marine bacterium that causes a variety of infections in immunocompromised patients or those who have been exposed to seawater. The development of trimethoprim/sulfamethoxazole (TMP/SMX) resistance in S. algae are found in human and environment isolates during the past ten years, and thus the treatment options are decreasing.

METHODOLOGY

In the study, we conduct a comparative genomic study to identify the resistant mechanism of TMP/SMX-resistance in S. algae.

RESULTS

We found the resistance of TMP/SMX in S. algae is associated with the existence of sul1 and dfrA12 within the class 1 integron. The gene cassette dfra12-aadA2-qacEΔ1/sul1 within the class 1 integron is highly conserved. In addition, the class 1 integron and encapsulated sul1 are significantly enriched in Enterobacteriaceae in NCBI and UniProt databases.

CONCLUSION

Our study suggests that the horizontal transfer of TMP/SMX resistance via class 1 integron is most frequently occurred within Enterobacteriaceae and has spread to a wide range of sources including soil, poultry, and marine water.

Molecular Characterization and the Antimicrobial Resistance Profile of Salmonella spp. Isolated from Ready-to-Eat Foods in Ouagadougou, Burkina Faso

The emergence of antimicrobial-resistantfood-borne bacteria is a great challenge to public health. This study was conducted to characterize and determine the resistance profile of Salmonella strains isolated from foods including sesames, ready-to-eat (RTE) salads, mango juices, and lettuce in Burkina Faso. One hundred and forty-eight biochemically identified Salmonella isolates were characterized by molecular amplification of Salmonella marker invA and spiC, misL, orfL, and pipD virulence genes. After that, all confirmed strains were examined for susceptibility to sixteen antimicrobials, and PCR amplifications were used to identify the following resistance genes: bla_TEM, temA, temB, StrA, aadA, sul1, sul2, tet(A), and tet(B). One hundred and eight isolates were genetically confirmed as Salmonella spp. Virulence genes were observed in 57.4%, 55.6%, 49.1%, and 38% isolates for pipD, SpiC, misL, and orfL, respectively. Isolates have shown moderate resistance to gentamycin (26.8%), ampicillin (22.2%), cefoxitin (19.4%), and nalidixic acid (18.5%). All isolates were sensitive to six antibiotics, including cefotaxime, ceftazidime, aztreonam, imipenem, meropenem, and ciprofloxacin. Among the 66 isolates resistant to at least one antibiotic, 11 (16.7%) were multidrug resistant. The Multiple Antimicrobial Resistance (MAR) index of Salmonella serovars ranged from 0.06 to 0.53. PCR detected 7 resistance genes (tet(A), tet(B), bla_TEM, temB, sul1, sul2, and aadA) in drug-resistant isolates. These findings raise serious concerns because ready-to-eat food in Burkina Faso could serve as a reservoir for spreading antimicrobial resistance genes worldwide.

Genomic and Evolutionary Analysis of Salmonella enterica Serovar Kentucky Sequence Type 198 Isolated From Livestock In East Africa

Since its emergence in the beginning of the 90’s, multidrug-resistant (MDR) Salmonella enterica subsp. enterica serovar Kentucky has become a significant public health problem, especially in East Africa. This study aimed to investigate the antimicrobial resistance profile and the genotypic relatedness of Salmonella Kentucky isolated from animal sources in Ethiopia and Kenya (n=19). We also investigated population evolutionary dynamics through phylogenetic and pangenome analyses with additional publicly available Salmonella Kentucky ST198 genomes (n=229). All the 19 sequenced Salmonella Kentucky isolates were identified as ST198. Among these isolates, the predominant genotypic antimicrobial resistance profile observed in ten (59.7%) isolates included the aac(3)-Id, aadA7, strA-strB, bla_TEM-1B, sul1, and tet(A) genes, which mediated resistance to gentamicin, streptomycin/spectinomycin, streptomycin, ampicillin, sulfamethoxazole and tetracycline, respectively; and gyrA and parC mutations associated to ciprofloxacin resistance. Four isolates harbored plasmid types Incl1 and/or Col8282; two of them carried both plasmids. Salmonella Pathogenicity islands (SPI-1 to SPI-5) were highly conserved in the 19 sequenced Salmonella Kentucky isolates. Moreover, at least one Pathogenicity Island (SPI 1–4, SPI 9 or C63PI) was identified among the 229 public Salmonella Kentucky genomes. The phylogenetic analysis revealed that almost all Salmonella Kentucky ST198 isolates (17/19) stemmed from a single strain that has accumulated ciprofloxacin resistance-mediating mutations. A total of 8,104 different genes were identified in a heterogenic and still open Salmonella Kentucky ST198 pangenome. Considering the virulence factors and antimicrobial resistance genes detected in Salmonella Kentucky, the implications of this pathogen to public health and the epidemiological drivers for its dissemination must be investigated.

Identification of Novel Type Three Secretion System (T3SS) Inhibitors by Computational Methods and Anti-Salmonella Evaluations

Three type III secretion system (T3SS) inhibitors (compounds 5, 19, and 32) were identified by virtual screening and biological evaluation. These three compounds were evaluated against a panel of Salmonella species strains including S. enteritidis, S. typhi, S. typhimurium, S. paratyphi, and S. abortus equi, and their minimum inhibitory concentrations ranged from 1 to 53 μg/ml. Especially, these compounds showed comparable activity as the of the positive control gatifloxacin towards S. abortus equi. The present results suggest that these new T3SS inhibitors could be used as a potential lead molecule for drug development of anti-Salmonella.

Prevalence of Antibiotic Resistance in Salmonella Serotypes Concurrently Isolated from the Environment, Animals, and Humans in South Africa: A Systematic Review and Meta-Analysis

One of the main global concerns is the usage and spread of antibiotic resistant Salmonella serovars. The animals, humans, and environmental components interact and contribute to the rapid emergence and spread of antimicrobial resistance, directly or indirectly. Therefore, this study aimed to determine antibiotic resistance (AR) profiles of Salmonella serotypes isolated from the environment, animals, and humans in South Africa by a systematic review and meta-analysis. The preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines were followed to search four databases for studies published from 1980 to 2021, that reported the antibiotic resistance profiles of Salmonella serotypes isolated in South Africa. The AR was screened from 2930 Salmonella serotypes which were isolated from 6842 samples. The Western Cape province had high pooled prevalence estimates (PPE) of Salmonella isolates with AR profiles followed by North West, Gauteng, and Eastern Cape with 94.3%, 75.4%, 59.4%, and 46.2%, respectively. The high PPE and heterogeneity were observed from environmental samples [69.6 (95% CI: 41.7−88.3), Q = 303.643, I² = 98.353, Q-P = 0.045], animals [41.9 (95% CI: 18.5–69.5), Q = 637.355, I² = 98.745, Q-P = 0.577], as well as animals/environment [95.9 (95% CI: 5.4−100), Q = 55.253, I² = 96.380, Q-P = 0.300]. The majority of the salmonella isolates were resistant to sulphonamides (92.0%), enrofloxacin and erythromycin (89.3%), oxytetracycline (77.4%), imipenem (72.6%), tetracycline (67.4%), as well as trimethoprim (52.2%), among the environment, animals, and humans. The level of multidrug-resistance recorded for Salmonella isolates was 28.5% in this review. This study has highlighted the occurrence of AR by Salmonella isolates from animals, humans, and environmental samples in South Africa and this calls for a consolidated “One Health” approach for antimicrobial resistance epidemiological research, as well as the formulation of necessary intervention measures to prevent further spread.

Presence of Tetracycline and Sulfonamide Resistance Genes in Salmonella spp.: Literature Review

Tetracyclines and sulfonamides are broad-spectrum antibacterial agents which have been used to treat bacterial infections for over half a century. The widespread use of tetracyclines and sulfonamides led to the emergence of resistance in a diverse group of bacteria. This resistance can be studied by searching for resistance genes present in the bacteria responsible for different resistance mechanisms. Salmonella is one of the leading bacteria causing foodborne diseases worldwide, and its resistance to tetracyclines and sulfonamides has been widely reported. The literature review searched the Virtual Health Library for articles with specific data in the studied samples: the resistance genes found, the primers used in PCR, and the thermocycler conditions. The results revealed that Salmonella presented high rates of resistance to tetracycline and sulfonamide, and the most frequent samples used to isolate Salmonella were poultry and pork. The tetracycline resistance genes most frequently detected from Salmonella spp. were tetA followed by tetB. The gene sul1 followed by sul2 were the most frequently sulfonamide resistance genes present in Salmonella. These genes are associated with plasmids, transposons, or both, and are often conjugative, highlighting the transference potential of these genes to other bacteria, environments, animals, and humans.

Antimicrobial Resistance of Non-Typhoid Salmonella in Meat and Meat Products

Salmonella enterica serovars are associated with numerous annual deaths worldwide and are responsible for a large number of foodborne diseases. Within this frame of reference, knowledge of antimicrobial susceptibility represents the fundamental approach of most Salmonella treatments. Therefore, scientific publications of antimicrobial susceptibilities and resistance must be precise, with interpretations adjusted to a particular standard. Hence, the three objectives in this study were: (i) to describe the frequency of antimicrobial-resistant isolates of Non-Typhoidal Salmonella (NTS) isolated from beef, pork, chicken meat, and other meat products; (ii) to describe the distribution of serovars and their multi-resistance to antibiotics for clinical use (veterinary and human) between 1996 and 2019; and (iii) to propose additional considerations that could improve the use and usefulness of the published results. Our results determined that the predominant isolates came from poultry. Enteritidis and Typhimurium were the most reported serovars by MIC (with both having the highest resistance to TET) while the lowest resistance was to CIP and CRO for Enteritidis and Typhimurium, respectively. The multi-resistance pattern AMP AMC CEP GEN KAN STR TET was the most frequently observed pattern by MIC in Montevideo and Seftenberg, while, for disc diffusion, the pattern AMP STR TET was the most frequent in the Bredeney serotype. In conclusion, researchers should carry out homogeneous sampling procedures, identify the types of the samples, use standard identification methods, and employ appropriate standards for antimicrobial susceptibility interpretation. Additionally, there is also a need for all WHO members to comply with the WHA 73.5 resolution. Our final recommendation is for all producers to reduce antibiotic prophylactic use.

Prevalence and Antimicrobial Resistance of Salmonella spp. in Aquacultured Nile Tilapia (Oreochromis niloticus) Commercialized in Federal District, Brazil

This study aimed to assess Salmonella spp. prevalence in aquaculture Nile tilapia commercialized in the Federal District, Brazil, and determine the antimicrobial resistance profile of the isolates. Fifty-seven Salmonella spp. strains were isolated from 101 samples of fresh tilapia fillets collected in the Federal District, Brazil. These isolates were subjected to antimicrobial susceptibility testing by the Kirby-Bauer disk diffusion method and analyzed for the presence of blaCTX, tetB, sul2, and floR resistance genes. The Salmonella spp. prevalence in fresh tilapia fillets was 45.5%; that is, 46 of 101 samples were positive for the InvA gene. The antimicrobial resistance profile showed high resistance rates for amoxicillin/clavulanic acid (87.7%), tetracycline (82.5%), sulfonamide (57.9%), and chloramphenicol (26.3%). Additionally, 56.1% of Salmonella spp. isolates were multidrug-resistant (MDR) isolates. The beta-lactam-resistant gene blaCTX was identified in 66.7% of isolates, the tetracycline resistance gene tetA in 54.4%, and the chloramphenicol resistance gene floR in 50.9%, while the sulfonamide resistance gene sul2 was present in 49.1%. The results revealed that tilapia fillets were highly contaminated with MDR Salmonella. These Salmonella spp. strains carried multiple antimicrobial resistance genes, which might facilitate their dissemination to consumers along the production chain. Hence, there is an evident need to control Salmonella in fish production systems to ensure public health.

Characterization of Salmonella spp. Isolates from Swine: Virulence and Antimicrobial Resistance

Simple Summary

Salmonella is a pathogenic bacterium able to infect both humans and animals. It is diffused worldwide and, generally, animals are a source of infection for humans. Among domestic animals, swine represents an important reservoir and a frequent source of human infection, especially in some countries like Italy. To acquire information on Salmonella, in particular about epidemiology, but also virulence, pathogenesis and antimicrobial resistance, is the basis for a cohesive control program. This manuscript describes an investigation conducted on Salmonella isolates from swine, where two important characteristics were evaluated: the pathogenicity and the antimicrobial resistance. A great variability was observed among investigated strains. Salmonella serovar Typhimurium was confirmed as one of the most virulent serovars; indeed, most isolates belonging to this serovar presented many of the searched virulence factors. A high level of antimicrobial resistance was observed for some compounds (sulfonamide, tetracycline, streptomycin and ampicillin), but not for the so-called “last line antibiotics”, such as, for example, ciprofloxacin. The constant monitoring on circulating strains in reservoir animals is important to acquire information and set up adequate prophylaxis measures.

Abstract

Salmonella is one of the most important zoonotic pathogens worldwide. Swine represent typical reservoirs of this bacterium and a frequent source of human infection. Some intrinsic traits make some serovars or strains more virulent than others. Twenty-nine Salmonella spp. isolated from pigs belonging to 16 different serovars were analyzed for gastric acid environment resistance, presence of virulence genes (mgtC, rhuM, pipB, sopB, spvRBC, gipA, sodCI, sopE), antimicrobial resistance and presence of antimicrobial resistance genes (bla_TEM, bla_PSE-1, aadA1, aadA2, aphA1-lab, strA-strB, tetA, tetB, tetC, tetG, sul1, sul2, sul3). A percentage of 44.83% of strains showed constitutive and inducible gastric acid resistance, whereas 37.93% of strains became resistant only after induction. The genes sopB, pipB and mgtC were the most often detected, with 79.31%, 48.28% and 37.93% of positive strains, respectively. Salmonella virulence plasmid genes were detected in a S. enterica sup. houtenae ser. 40:z₄,z₂₃:-strain. Fifteen different virulence profiles were identified: one isolate (ser. Typhimurium) was positive for 6 genes, and 6 isolates (3 ser. Typhimurium, 2 ser. Typhimurium monophasic variant and 1 ser. Choleraesuis) scored positive for 5 genes. None of the isolates resulted resistant to cefotaxime and ciprofloxacin, while all isolates were susceptible to ceftazidime, colistin and gentamycin. Many strains were resistant to sulfonamide (75.86%), tetracycline (51.72%), streptomycin (48.28%) and ampicillin (31.03%). Twenty different resisto-types were identified. Six strains (4 ser. Typhimurium, 1 ser. Derby and 1 ser. Typhimurium monophasic variant) showed the ASSuT profile. Most detected resistance genes sul2 (34.48%), tetA (27.58%) and strA-strB (27.58%). Great variability was observed in analyzed strains. S. ser. Typhimurium was confirmed as one of the most virulent serovars. This study underlines that swine could be a reservoir and source of pathogenic Salmonella strains.

Molecular characterization of antimicrobial resistance and enterobacterial repetitive intergenic consensus-PCR as a molecular typing tool for Salmonella spp. isolated from poultry and humans

Background and Aim:

Salmonella spp. are one of the most important food-borne pathogens in the world, emerging as a major public health concern. Moreover, multidrug-resistant (MDR) strains have been isolated from salmonellosis outbreaks, which compromise its treatment success. This study was conducted to characterize the phenotypic and genotypic antibiotic resistance profile of Salmonella strains isolated from broilers and humans from the regions of Tolima and Santander (Colombia).

Materials and Methods:

Salmonella spp. strains (n=49) were confirmed through molecular detection by amplification of the invA gene. Phenotypic antibiotic resistance was determined by the automated method and the agar diffusion method, and the presence of resistance genes was evaluated by PCR. Genotypic characterization was conducted using the enterobacterial repetitive intergenic consensus (ERIC)-PCR method, from which a dendrogram was generated and the possible phylogenetic relationships were established.

Results:

Salmonella isolates were classified as MDR strains exhibiting resistance to four antibiotic classes, penicillins, aminoglycosides, sulfonamides, and cephalosporins, and the human strains were resistant to gentamicin. At the genotypic level, the isolates contained the genes bla_CMY2, bla_CTX-M, bla_PSE-1, bla_TEM, aadA1, srtB, dfrA1, sul2, and floR. The genotyping results obtained by ERIC-PCR allowed the grouping of strains according to the source of isolation.

Conclusion:

The Salmonella spp. strains exhibited resistance to multiple antibiotics, as well as multiple genes associated with them, and the ERIC-PCR method was a technique that was helpful in generating clusters with biological significance.

Development and evaluation of a Luminex xTAG assay for sulfonamide resistance genes in Escherichia coli and Salmonella isolates

Clinically occurring sulfonamide resistance in gram-negative bacteria is codified by several sul genes, mostly associated with the mobilized genetic elements named integrons, and integrons are frequently found in plasmids. There are four sul genes (sul1, sul2, sul3 and sul4) that encode resistance to sulfonamides. The aim of the present study was to develop a bead-based xTAG assay for the simultaneous detection of all four sul genes and related Class 1 integrons (int1) in Escherichia coli and Salmonella isolates. The limits of detection ranged from 10 to 1000 copies/μL of input purified plasmid DNA. Forty-one bacterial isolates from clinical samples were examined using the newly developed xTAG assay and also by conventional PCR to determine the relative performance of each. The results obtained by xTAG assay showed higher detection rates and accuracy for sul genes than conventional PCR. It indicated that the xTAG-multiplex PCR is a convenient method for rapid identification of sul genes.

Horizontal Gene Transfer and Acquired Antibiotic Resistance in Salmonella enterica Serovar Heidelberg following In Vitro Incubation in Broiler Ceca

The chicken gastrointestinal tract harbors microorganisms that play a role in the health and disease status of the host. The cecum is the part of the gut that carries the highest microbial densities, has the longest residence time of digesta, and is a vital site for urea recycling and water regulation. Therefore, the cecum provides a rich environment for bacteria to horizontally transfer genes between one another via mobile genetic elements such as plasmids and bacteriophages. In this study, we used broiler chicken cecum as a model to investigate antibiotic resistance genes that can be transferred in vitro from cecal flora to Salmonella enterica serovar Heidelberg. We used whole-genome sequencing and resistome enrichment to decipher the interactions between S Heidelberg, the gut microbiome, and acquired antibiotic resistance. After 48 h of incubation of ceca under microaerophilic conditions, we recovered one S Heidelberg isolate with an acquired IncK2 plasmid (88 kb) carrying an extended-spectrum-β-lactamase gene (bla _CMY-2). In vitro, this plasmid was transferable between Escherichia coli and S Heidelberg strains but transfer was unsuccessful between S Heidelberg strains. An in-depth genetic characterization of transferred plasmids suggests that they share significant homology with P1-like phages. This study contributes to our understanding of horizontal gene transfer between an important foodborne pathogen and the chicken gut microbiome.IMPORTANCE S. Heidelberg is a clinically important serovar, linked to foodborne illness and among the top 5 serovars isolated from poultry in the United States and Canada. Acquisition of new genetic material from the microbial flora in the gastrointestinal tract of food animals, including broilers, may contribute to increased fitness of pathogens like S. Heidelberg and may increase their level of antibiotic tolerance. Therefore, it is critical to gain a better understanding of the interactions that occur between important pathogens and the commensals present in the animal gut and other agroecosystems. In this report, we show that the native flora in broiler ceca were capable of transferring mobile genetic elements carrying the AmpC β-lactamase (bla _CMY-2) gene to an important foodborne pathogen, S Heidelberg. The potential role for bacteriophage transduction is also discussed.

Diverse Mobile Genetic Elements and Conjugal Transferability of Sulfonamide Resistance Genes (sul1, sul2, and sul3) in Escherichia coli Isolates From Penaeus vannamei and Pork From Large Markets in Zhejiang, China

High prevalence rates of sulfonamide resistance genes sul1, sul2, and sul3 have been observed in Gram-negative bacteria isolated from humans, domestic animals, and aquaculture species worldwide. We investigated the distribution characteristics, location, conjugative transferability, and genetic environments of sul genes from Escherichia coli isolates collected from Penaeus vannamei and pork samples from three large markets in Zhejiang, China. The prevalence rates of sul genes in sulfonamide-resistant E. coli isolates from P. vannamei and pork samples were 90.0 and 88.6%, respectively, and the prevalence of sul1 and sul2 was significantly higher than that of sul3 (p < 0.05). Twenty-four representative sul-positive E. coli isolates were analyzed in detail. Southern blot hybridization confirmed that sul genes of E. coli isolates were located on plasmids and/or chromosomes. Transfer of resistance through conjugation was observed in all 18 E. coli isolates harboring sul genes on plasmids. Replicon typing identified seven different incompatibility groups and IncF was the dominant replicon type among sul gene-containing plasmids from both sources. PCR walking analysis indicated that 87.5% (35/40) of sul gene-related fragments carried insertion sequences (ISs) belonging to a variety of families in diverse sites, with IS26 occurring most frequently. In addition, the sul1 gene was detected mainly in fragments carrying class 1 integrons. Co-location on the same fragment with resistance genes that may contribute to the persistence and dissemination of sul1 and/or sul2 genes. The diversity of mobile genetic elements and resistance genes adjacent to sul3 was much lower than those adjacent to sul1 and sul2, especially those located in chromosomes, which reduced the transmission potential of the sul3 gene. In conclusion, combined with the results of clonal relatedness analysis by PFGE and MLST of 24 representative E. coli isolates from P. vannamei and pork samples, it showed that a small number of sul genes were vertically transmitted among E. coli from P. vannamei and that horizontal gene transfer was likely the main transmission mechanism of sul genes from both sources. Our results provide important information to better understand the risk of transmission of sul genes from seafood and meat to humans.

An IncX1 plasmid isolated from Salmonella enterica subsp. enterica serovar Pullorum carrying blaTEM-1B, sul2, arsenic resistant operons

We have identified an IncX1 plasmid named pQJDSal1 from Salmonella enterica subsp. enterica serovar Pullorum (S. Pullorum). The plasmid is 67,685 bp in size and has 72 putative genes. pQJDSal1 harbors a conserved IncX1-type backbone with predicted regions for conjugation, replication and partitioning, as well as a toxin/antitoxin plasmid addiction system. Two regions (A and B) that have not been previously reported in IncX1 plasmids are inserted into the backbone. Region A (10.7 kb), inserted between parA and taxD, consists of a new Tn6168-like transposon containing an arsenic resistant operon arsB2CHR and sulfonamide resistance gene sul2. Region B contains another arsenic resistant operon arsADHR, resistance gene bla_TEM-1B and three transposable elements. Conjugation experiments showed that pQJDSal1 could transfer from S. Pullorum to Escherichia coli (E. coli) J53. Statistical analysis of 70 sequenced IncX1 plasmids revealed that IncX1 plasmids harbored various antibiotic resistance genes. The results highlight the importance of IncX1 plasmids in disseminating antibiotic resistance genes.

Establishment of a Multiplex Loop-Mediated Isothermal Amplification Method for Rapid Detection of Sulfonamide Resistance Genes (sul1, sul2, sul3) in Clinical Enterobacteriaceae Isolates from Poultry

Antimicrobial resistance genes play an important role in mediating resistance to sulfonamide in Gram-negative bacteria. While PCR is the current method to detect sulfonamide resistance genes (sul1, sul2, sul3), it is time-consuming and costly and there is an urgent need to develop a more convenient, simpler and rapid test for the sul. In this study, we describe a multiplex loop-mediated isothermal amplification (m-LAMP) assay we developed for the rapid and simultaneous detection of three sul. This m-LAMP assay successfully detected seven reference strains with different sul genotypes, but was negative for nine sul-negative reference strains. The m-LAMP products were verified by HinfI restriction enzyme digestion and the detection limit of the test was 0.5 pg genomic DNA per reaction. Testing 307 sulfonamide-resistant Enterobacteriaceae clinical isolates with the m-LAMP revealed all were positive for the sul with sul2 (79.5%) and sul1 (64.5%) being most prevalent, and sul3 the least (12.1%). Of the Enterobacteriaceae isolates tested, the Salmonella Indiana, a newly emerging serovar resistant to numerous antimicrobials, were most commonly positive with 33% having sul3.