Salmonella entericain Mexico 2000–2017: Epidemiology, Antimicrobial Resistance, and Prevalence in Food

Effects of intrinsic characteristics of Salmonella enterica strains isolated from foods and humans, and their interaction with food matrices during simulated gastric conditions

The stomach's acidic pH is a crucial barrier against foodborne pathogens such as Salmonella enterica. This study investigated the survival of S. enterica under simulated oral and gastric conditions (SGC; pH 2 for 120 min) as a function of intrinsic pathogen characteristics and food matrix. Fifty-seven S. enterica strains isolated from food and human infections (previously characterized by serotype, virulotype, multi-drug resistance, isolation source, and isolation season) were subjected to SGC using water as a vehicle. Population reduction among the 57 isolates ranged from 2.7 to 4.7 log CFU, revealing that human isolates were inactivated less than food isolates (p = 0.0008). Among food strains, strains isolated during the cold season (food sampled from December to February) displayed the highest reduction (p = 0.00002). Six representatives of the 57 S. enterica strains were selected according to their virulotype and antimicrobial profile. They were further used to evaluate their survival under SGC in four food matrices (water, mango, tomato, and chicken), measuring S. enterica at 30 min intervals. The strains in chicken showed the lowest reduction and inactivation rate (1.42 ± 0.35 log CFU; 0.03 ± 0.005 min-1), followed by tomato (3.75 ± 0.57 log CFU; 0.15 ± 0.02 min-1), water (4.23 ± 0.27 log CFU; 0.17 ± 0.02 min-1), and mango (4.49 ± 0.39 log CFU; 0.17 ± 0.03 min-1). These data suggest that not all S. enterica strains have the same ability to survive under SGC, influencing the probability of arriving into the small intestine.

Polyphenols and CRISPR as Quorum Quenching Agents in Antibiotic-Resistant Foodborne Human Pathogens (Salmonella Typhimurium, Campylobacter jejuni and Escherichia coli 0157:H7)

Antibiotic resistance in foodborne pathogens is an increasing threat to global human health. Among the most prevalent antibiotic-resistant bacteria are Salmonella enterica serovar Typhimurium, Campylobacter jejuni and E. coli 0157:H7. Control of these and other pathogens requires innovative approaches, i.e., discovering new molecules that will inactivate them, or render them less virulent without inducing resistance. Recently, several polyphenol molecules have been shown to possess such characteristics. Also, the use of CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) approaches has recently been proposed for such purpose. This review summarizes the main findings regarding the application of both approaches to control the above-mentioned foodborne pathogens by relying on Quorum Sensing interference (Quorum Quenching) mechanisms and highlights the avenues needed for further research.

Polyphenols and CRISPR as Quorum Quenching Agents in Antibiotic-Resistant Foodborne Human Pathogens (Salmonella Typhimurium, Campylobacter jejuni and Escherichia coli 0157:H7)

Antibiotic resistance in foodborne pathogens is an increasing threat to global human health. Among the most prevalent antibiotic-resistant bacteria are Salmonella enterica serovar Typhimurium, Campylobacter jejuni and E. coli 0157:H7. Control of these and other pathogens requires innovative approaches, i.e., discovering new molecules that will inactivate them, or render them less virulent without inducing resistance. Recently, several polyphenol molecules have been shown to possess such characteristics. Also, the use of CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) approaches has recently been proposed for such purpose. This review summarizes the main findings regarding the application of both approaches to control the above-mentioned foodborne pathogens by relying on Quorum Sensing interference (Quorum Quenching) mechanisms and highlights the avenues needed for further research.

Genomic diversity of Salmonella enterica isolated from raw chicken at retail establishments in Mexico

The genomic diversity of circulating non-typhoidal Salmonella in raw chicken was investigated in three states of central Mexico. A total of 192 S. enterica strains from chicken meat samples collected at supermarkets, fresh markets, and butcher shops were analyzed by whole-genome sequencing. The serovar distribution, occurrence of genes encoding for antimicrobial resistance, metal resistance, biocide resistance, plasmids and virulence factors, and clonal relatedness based on single nucleotide polymorphism (SNP) analysis were investigated. Serovars Infantis, Schwarzengrund and Enteritidis predominated among twenty identified. The distribution of serovars and proportion of AMR genes was different according to the state, year, season, and retail establishment (p < 0.001). Genes encoding metals resistance were identified in all the strains. A total of 145 virulence genes were identified and strains were classified into 32 virulotypes; serovars Infantis, Typhimurium, and Enteritidis showed the highest number of virulence genes. The strains matched 34 SNP clusters in the NCBI Pathogen Detection server and 59 %, which corresponded to Infantis, Schwarzengrund, Saintpaul, and Enteritidis, were associated with five major clusters and matched with chicken, environmental and clinical isolates from at least three countries. These results provide useful information to understand the epidemiology of Salmonella, conduct microbial risk assessment, and design risk-based control measures.

Genomic analysis of the MLST population structure and antimicrobial resistance genes associated with Salmonella enterica in Mexico

Salmonella enterica is one of the most commonly reported foodborne pathogens by public health agencies worldwide. In this study, the multilocus sequence typing (MLST) population structure and frequency of antimicrobial resistance (AMR) genes were evaluated in S. enterica strains from Mexico (n = 2561). The most common sources of isolation were food (44.28%), environment (27.41%), animal-related (24.83%), and human (3.48%). The most prevalent serovars were Newport (8.51%), Oranienburg (7.03%), Anatum (5.78%), Typhimurium (5.12%), and Infantis (4.57%). As determined by the 7-gene MLST scheme, the most frequent sequence types were ST23, ST64, and ST32. The core genome MLST scheme identified 132 HC2000 and 195 HC900 hierarchical clusters, with the HC2000_2 cluster being the most prevalent in Mexico (n = 256). A total of 78 different AMR genes belonging to 13 antimicrobial classes were detected in 638 genomic assemblies of S. enterica. The most frequent class was aminoglycosides (31.76%), followed by tetracyclines (12.53%) and sulfonamides (11.91%). These results can help public health agencies in Mexico prioritize their efforts and resources to increase the genomic sequencing of circulating Salmonella strains. Additionally, they provide valuable information for local and global public health efforts to reduce the impact of foodborne diseases and AMR.

Prevention and Control of Human Salmonella enterica Infections: An Implication in Food Safety

Salmonella is a foodborne zoonotic pathogen causing diarrhoeal disease to humans after consuming contaminated water, animal, and plant products. The bacterium is the third leading cause of human death among diarrhoeal diseases worldwide. Therefore, human salmonellosis is of public health concern demanding integrated interventions against the causative agent, Salmonella enterica. The prevention of salmonellosis in humans is intricate due to several factors, including an immune-stable individual infected with S. enterica continuing to shed live bacteria without showing any clinical signs. Similarly, the asymptomatic Salmonella animals are the source of salmonellosis in humans after consuming contaminated food products. Furthermore, the contaminated products of plant and animal origin are a menace in food industries due to Salmonella biofilms, which enhance colonization, persistence, and survival of bacteria on equipment. The contaminated food products resulting from bacteria on equipment offset the economic competition of food industries and partner institutions in international business. The most worldwide prevalent broad-range Salmonella serovars affecting humans are Salmonella Typhimurium and Salmonella Enteritidis, and poultry products, among others, are the primary source of infection. The broader range of Salmonella serovars creates concern over multiple strategies for preventing and controlling Salmonella contamination in foods to enhance food safety for humans. Among the strategies for preventing and controlling Salmonella spread in animal and plant products include biosecurity measures, isolation and quarantine, epidemiological surveillance, farming systems, herbs and spices, and vaccination. Other measures are the application of phages, probiotics, prebiotics, and nanoparticles reduced and capped with antimicrobial agents. Therefore, Salmonella-free products, such as beef, pork, poultry meat, eggs, milk, and plant foods, such as vegetables and fruits, will prevent humans from Salmonella infection. This review explains Salmonella infection in humans caused by consuming contaminated foods and the interventions against Salmonella contamination in foods to enhance food safety and quality for humans.

Antimicrobial Resistance of Lactic Acid Bacteria from Nono, a Naturally Fermented Milk Product

BACKGROUND

Antimicrobial resistance (AMR) is one of the biggest threats to public health. The food chain has been recognised as a vehicle for transmitting AMR bacteria. However, information about resistant strains isolated from African traditional fermented foods remains limited. Nono is a traditional, naturally fermented milk product consumed by many pastoral communities across West Africa. The main aim of this study was to investigate and determine the AMR patterns of lactic acid bacteria (LAB) involved in the traditional fermentation of milk for Nono production, and the presence of transferable AMR determinants.

METHODS

One hundred (100) LAB isolates from Nono identified in a previous study as Limosilactobacillus fermentum, Lactobacillus delbrueckii, Streptococcus thermophilus, Streptococcus infantarius, Lentilactobacillus senioris, Leuconostoc pseudomesenteriodes, and Enterococcus thailandicus were investigated. The minimum inhibitory concentration (MIC) was determined for 18 antimicrobials using the micro-broth dilution method. In addition, LAB isolates were screened for 28 antimicrobial resistance genes using PCR. The ability of LAB isolates to transfer tetracycline and streptomycin resistance genes to Enterococcus faecalis was also investigated.

RESULTS

The experiments revealed variable antimicrobial susceptibility according to the LAB isolate and the antimicrobial tested. The tetracycline resistance genes tet(S) and tet(M) were detected in isolates Ent. thailandicus 52 and S. infantarius 10. Additionally, aad(E) encoding resistance to streptomycin was detected in Ent. thailandicus 52. The conjugation experiments suggested that the tet(S) and aad(E) genes were transferable in vitro from isolate Ent. thailandicus 52 to Ent. faecalis JH2-2.

SIGNIFICANCE AND IMPACT

Traditional fermented foods play a significant role in the diet of millions of people in Africa, yet their contribution to the burden of AMR is largely unknown. This study highlights that LAB involved in traditionally fermented foods could be potential reservoirs of AMR. It also underscores the relevant safety issues of Ent. thailandicus 52 and S. infantarius 10 for use as starter cultures as they carry transferable AMR genes. Starter cultures are an essential aspect of improving the safety and quality attributes of African fermented foods. However, AMR monitoring is an important safety aspect in the selection of starter cultures for improving traditional fermentation technologies.

Virulence and antimicrobial resistance profiles of Salmonella enterica isolated from foods, humans, and the environment in Mexico

Salmonella enterica genotypic and phenotypic characteristics play an important role in its pathogenesis, which could be influenced by its origin. This study evaluated the association among the antimicrobial resistance, virulence, and origin of circulating S. enterica strains in Mexico, isolated from foods, humans, and the environment. The antimicrobial susceptibility to fourteen antibiotics by the Kirby-Bauer method (n = 117), and the presence of thirteen virulence genes by multiplex PCR (n = 153) and by sequence alignments (n = 2963) were evaluated. In addition, a set of S. enterica isolates from Mexico (n = 344) previously characterized according to their genotypic and phenotypic print was included to increase the coverage of the association analysis. Strains with the presence of sopE and strains with the absence of sspH1 were significantly associated with multidrug-resistant (MDR) phenotypes (p < 0.05). The origin of the strains had significant associations with the antimicrobial profiles and some virulence genes (hilA, orgA, sifA, ssaQ, sseL, sspH1, pefA, and spvC) (p < 0.05). Animal-origin food isolates showed the highest frequency of MDR (57.2 %), followed by human isolates (30.0 %). Also, sspH1, pefA, and spvC were found in major frequency in human (32.4 %, 31.0 %, 31.7 %) and animal-origin foods (41.6 %, 10.6 %, 10.6 %) isolates. The findings highlighted that antimicrobial profiles and specific virulence genes of S. enterica strains are related to their origin. Similar genotypic and phenotypic characteristics between human and animal-origin foods isolates were found, suggesting that animal-origin foods isolates are the most responsible for human cases. The revealed associations can be used to improve risk estimation assessments in national food safety surveillance programs.

Risk ranking of food categories associated with Salmonella enterica contamination in the central region of Mexico

To prevent and control foodborne diseases, there is a fundamental need to identify the foods that are most likely to cause illness. The goal of this study was to rank 25 commonly consumed food products associated with Salmonella enterica contamination in the Central Region of Mexico. A multicriteria decision analysis (MCDA) framework was developed to obtain an S. enterica risk score for each food product based on four criteria: probability of exposure to S. enterica through domestic food consumption (Se); S. enterica growth potential during home storage (Sg); per capita consumption (Pcc); and food attribution of S. enterica outbreak (So). Risk scores were calculated by the equation Se*W₁ +Sg*W₂ +Pcc*W₃ +So*W₄ , where each criterion was assigned a normalized value (1-5) and the relative weights (W) were defined by 22 experts' opinion. Se had the largest effect on the risk score being the criterion with the highest weight (35%; IC95% 20%-60%), followed by So (24%; 5%-50%), Sg (23%; 10%-40%), and Pcc (18%; 10%-35%). The results identified chicken (4.4 ± 0.6), pork (4.2 ± 0.6), and beef (4.2 ± 0.5) as the highest risk foods, followed by seed fruits (3.6 ± 0.5), tropical fruits (3.4 ± 0.4), and dried fruits and nuts (3.4 ± 0.5), while the food products with the lowest risk were yogurt (2.1 ± 0.3), chorizo (2.1 ± 0.4), and cream (2.0 ± 0.3). Approaches with expert-based weighting and equal weighting showed good correlation (R²  = 0.96) and did not show significant differences among the ranking order in the top 20 tier. This study can help risk managers select interventions and develop targeted surveillance programs against S. enterica in high-risk food products.

Hand hygiene practices in Caribbean and Latin American countries: An integrative review

AIM AND OBJECTIVE

To explore what is known about knowledge, attitudes and beliefs that influence hand hygiene practices in in low- and middle-income Caribbean and Latin American countries.

BACKGROUND

With the emergence of infectious diseases such as the recent COVID-19 pandemic, handwashing is key to preventing communicable diseases as they disproportionately affect populations in low-income countries. While hand hygiene is known to be the single most effective method for avoiding the transmission of infection, little is known about the beliefs and practices of individuals in these regions.

METHODS

Following PRISMA 2020 Checklist, an integrative review of studies published from 2008-2020 was conducted (Preferred Reporting Items for Systematic Reviews and Meta-analyses). Whittemore and Knafl's method was used to review the literature. Six databases were searched, and the Johns Hopkins Evidence Based Rating Scale was used for study appraisal.

RESULTS

The review yielded 18 studies conducted across Latin America. Poor handwashing practices are influenced by various factors including inadequate education and training, cultural beliefs, lack of resources and substandard government regulations. Communicable diseases and other diarrheal illnesses were highly prevalent, especially after a major disease outbreak.

CONCLUSION

Future post-disaster campaigns aimed at improving hand hygiene and handwashing practices should focus on beliefs and attitudes to affect behaviour change since there was a higher disease susceptibility during those times. Barriers to proper hand hygiene include false attitudes such as, washing hands only after touching bodily fluids/patient contact or not washing hands at all after open defecation.

RELEVANCE TO CLINICAL PRACTICE

Researchers working with populations in Latin America and the Caribbean should partner with local community health workers to improve compliance to recommended hand hygiene practices.

Characterization of novel antimicrobial peptides designed on the basis of amino acid sequence of peptides from egg white hydrolysate

Salmonella enterica subsp. enterica serotype Typhimurium (S. Typhimurium) is one of the most prevalent foodborne pathogens responsible for food poisoning and is spread through the consumption of contaminated poultry products. In this study, four antimicrobial peptides (AMPs) with varying hydrophobicity and helical structure-forming tendencies were designed and synthesized based on the amino acid sequences of peptides from egg white hydrolysate. Two of these AMPs, P1R3 (KSWKKHVVSGFFLR) and P1C (KSWKKHVVSGFFLRLWVHKK), exhibited inhibitory activity against S. Typhimurium and compromised its biofilm-forming ability. Investigation of their modes of action revealed that P1R3 and P1C interact with and permeabilize the cytoplasmic membrane of bacteria, leading to membrane potential dissipation, damage to membrane integrity, and consequent bacterial death. P1R3 also bound to S. Typhimurium DNA, resulting in DNA aggregation or precipitation. Moreover, both peptides showed negligible cytotoxicity to Vero cells, and P1C displayed significant antimicrobial activity in chicken meat. Peptides P1R3 and P1C, therefore, have the potential to be developed as promising food preservatives, especially against pathogenic S. Typhimurium.

Prevalence and Genomic Diversity of Salmonella enterica Recovered from River Water in a Major Agricultural Region in Northwestern Mexico

Salmonella enterica is a leading cause of human gastrointestinal disease worldwide. Given that Salmonella is persistent in aquatic environments, this study examined the prevalence, levels and genotypic diversity of Salmonella isolates recovered from major rivers in an important agricultural region in northwestern Mexico. During a 13-month period, a total of 143 river water samples were collected and subjected to size-exclusion ultrafiltration, followed by enrichment, and selective media for Salmonella isolation and quantitation. The recovered Salmonella isolates were examined by next-generation sequencing for genome characterization. Salmonella prevalence in river water was lower in the winter months (0.65 MPN/100 mL) and significantly higher in the summer months (13.98 MPN/100 mL), and a Poisson regression model indicated a negative effect of pH and salinity and a positive effect of river water temperature (p = 0.00) on Salmonella levels. Molecular subtyping revealed Oranienburg, Anatum and Saintpaul were the most predominant Salmonella serovars. Single nucleotide polymorphism (SNP)-based phylogeny revealed that the detected 27 distinct serovars from river water clustered in two major clades. Multiple nonsynonymous SNPs were detected in stiA, sivH, and ratA, genes required for Salmonella fitness and survival, and these findings identified relevant markers to potentially develop improved methods for characterizing this pathogen.

Genomic epidemiology of Salmonella enterica circulating in surface waters used in agriculture and aquaculture in central Mexico

Salmonella enterica can survive in surface waters (SuWa), and the role of nonhost environments in its transmission has acquired increasing relevance. In this study, we conducted comparative genomic analyses of 172 S. enterica isolates collected from SuWa across 3 months in six states of central Mexico during 2019. S. enterica transmission dynamics were assessed using 87 experimental and 112 public isolates from Mexico collected during 2002 through 2019. We also studied genetic relatedness between SuWa isolates and human clinical strains collected in North America during 2005 through 2020. Among experimental isolates, we identified 41 S. enterica serovars and 56 multilocus sequence types (STs). Predominant serovars were Senftenberg (n = 13), Meleagridis, Agona, and Newport (n = 12 each), Give (n = 10), Anatum (n = 8), Adelaide (n = 7), and Infantis, Mbandaka, Ohio, and Typhimurium (n = 6 each). We observed a high genetic diversity in the sample under study, as well as clonal dissemination of strains across distant regions. Some of these strains are epidemiologically important (ST14, ST45, ST118, ST132, ST198, and ST213) and were genotypically close to those involved in clinical cases in North America. Transmission network analysis suggests that SuWa are a relevant source of S. enterica (0.7 source/hub ratio) and contribute to its dissemination as isolates from varied sources and clinical cases have SuWa isolates as common ancestors. Overall, the study shows that SuWa act as reservoirs of various S. enterica serovars of public health significance. Further research is needed to better understand the mechanisms involved in SuWa contamination by S. enterica, as well as to develop interventions to contain its dissemination in food production settings.

IMPORTANCE Surface waters are heavily used in food production worldwide. Several human pathogens can survive in these waters for long periods and disseminate to food production environments, contaminating our food supply. One of these pathogens is Salmonella enterica, a leading cause of foodborne infections, hospitalizations, and deaths in many countries. This research demonstrates the role of surface waters as a vehicle for the transmission of Salmonella along food production chains. It also shows that some strains circulating in surface waters are very similar to those implicated in human infections and harbor genes that confer resistance to multiple antibiotics, posing a risk to public health. This study contributes to expand our current knowledge on the ecology and epidemiology of Salmonella in surface waters.

Detection, quantification, and characterization of Salmonella enterica in mango, tomato, and raw chicken purchased in the central region of Mexico

To estimate human exposure to Salmonella enterica, it is essential to understand the pathogen distribution and characteristics. Prevalence and concentration of S. enterica were determined in mango, tomato, and raw chicken samples purchased in three states (Aguascalientes, Querétaro, and Guadalajara) located in the central region of Mexico during two seasons. In addition, S. enterica isolates were characterized by absence/presence of 13 virulence genes (chromosomal, prophage, and plasmid) and resistance to 14 antibiotics. A total of 300 samples of mango, 272 of tomato, and 354 of raw chicken were analyzed. The mean of the prevalence (24.9%) and concentration (-0.61 Log MPN/g) of S. enterica in chicken was higher than in mango (1.3%, -1.7 Log MPN/g) and tomato (1.1%, -1.7 Log MPN). Among S. enterica isolates (284), there were 7 different virulotypes, belonging 68.7% of isolates to V2; there was high variability in the presence of mobile genetic elements. The occurrence of specific mobile elements ranged from 81.4% to 11.3% among isolates. Among the isolates, 91.5% were resistant to at least one antibiotic with ampicillin being the most frequent; 54.9% of isolates were multidrug resistant. Data from this study can be used for quantitative microbial risk assessment of S. enterica related to mango, tomato, and raw chicken consumption in the central region of Mexico. PRACTICAL APPLICATION: Data on the prevalence and concentration of Salmonella enterica obtained in this study can be used to estimate the exposure assessment for the consumption of mango, tomato, and chicken in the central region of Mexico. In addition, the characteristics of the S. enterica isolates could be used to select representative strains for future studies to evaluate the intraspecies variability.

Systematic Review: Nontyphoidal Salmonella in Food from Latin America

In Latin America, nontyphoidal Salmonella (NTS) is one of the most important etiological agents of foodborne infections; it can survive in soil, water, and food even after processing. Here, we aimed to perform a systematic review by collecting data on the prevalence, serotypes, and antimicrobial resistance (AMR) of NTS isolated from different food products in Latin America, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Out of 1766 studies screened, 244 reports from 13 Latin American countries were eligible. Among these, 182 reported NTS prevalence, 87 reported NTS serotypes, and 83 reported serotypes with AMR patterns. The NTS prevalence ranged from 0.005% to 93.3%, regardless of country and food. Meat showed the highest NTS prevalence. Enteritidis, Typhimurium, and Derby were the most frequently observed serotypes in different food products. The serotypes Enteritidis, Typhimurium, and Infantis, isolated from animal products, showed the highest AMR rate. The presence of NTS in fruits and vegetables, which are generally consumed raw or as ready-to-eat food, indicates a high risk of salmonellosis from consuming these foods. Thus, the reduction of this pathogen in the food chain requires a One Health approach, involving good agricultural and manufacturing practices, low antimicrobial use, and proper waste management.

Edaphoclimatic seasonal trends and variations of the Salmonella spp. infection in Northwestern Mexico

Currently, Salmonella spp. is the bacterium causing the highest number of food-borne diseases (FADs) in the world. It is primarily associated with contaminated water used to that irrigates crops from intensive livestock farming. However, literature emphasizes that the reservoirs for Salmonella spp. remain in wildlife and there are unconventional sources or secondary reservoirs, such as soil. Human soil-borne diseases have not been modeled in spatial scenarios, and therefore it is necessary to consider soil and other climatic factors to anticipate the emergence of new strains or serotypes with potential threat to public and animal health. The objective of this research was to investigate whether edaphic and climatic factors are associated with the occurrence and prevalence of Salmonella spp. in Northwestern Mexico. We estimated the potential distribution of Salmonella spp. with an interpolation method of unsampled kriging areas for 15 environmental variables, considering that these factors have a seasonal dynamic of change during the year and modifications in longer periods. Subsequently, a database was generated with human salmonellosis cases reported in the epidemiological bulletins of the National System of Epidemiological Surveillance (SIVE). For the Northwest region, there were 30,595 human cases of paratyphoid and other salmonellosis reported have been reported in Baja California state, 71,462 in Chihuahua, and 16,247 in Sonora from 2002 to 2019. The highest prevalence was identified in areas with higher temperatures between 35 and 37 °C, and precipitation greater than 1000 mm. The edaphic variables limited the prevalence and geographical distribution of Salmonella spp., because the region is characterized by presenting a low percentage of organic matter (≤4.3), and most of the territory is classified as aridic and xeric, which implies that the humidity comprises ≤ 180 days a year. Finally, the seasonal time series indicated that in the states of Baja California and Chihuahua the rainy quarter of the year is 18.7% and 17.01% above a typical quarter respectively, while for Sonora the warmest quarter is 23.3%. It is necessary to deepen the relationship between different soil characteristics and climate elements such as temperature and precipitation, which influence the distribution of different soil-transmitted diseases.

Genomic surveillance of antimicrobial resistance shows cattle and poultry are a moderate source of multi-drug resistant non-typhoidal Salmonella in Mexico

Multi-drug resistant (MDR) non-typhoidal Salmonella (NTS) is a public health concern globally. This study reports the phenotypic and genotypic antimicrobial resistance (AMR) profiles of NTS isolates from bovine lymph nodes (n = 48) and ground beef (n = 29). Furthermore, we compared genotypic AMR data of our isolates with those of publicly available NTS genomes from Mexico (n = 2400). The probability of finding MDR isolates was higher in ground beef than in lymph nodes:χ2 = 12.0, P = 0.0005. The most common resistant phenotypes involved tetracycline (40.3%), carbenicillin (26.0%), amoxicillin-clavulanic acid (20.8%), chloramphenicol (19.5%) and trimethoprim-sulfamethoxazole (16.9%), while more than 55% of the isolates showed decreased susceptibility to ciprofloxacin and 26% were MDR. Conversely, resistance to cephalosporins and carbapenems was infrequent (0-9%). MDR phenotypes were strongly associated with NTS serovar (χ2 = 24.5, P<0.0001), with Typhimurium accounting for 40% of MDR strains. Most of these (9/10), carried Salmonella genomic island 1, which harbors a class-1 integron with multiple AMR genes (aadA2, blaCARB-2, floR, sul1, tetG) that confer a penta-resistant phenotype. MDR phenotypes were also associated with mutations in the ramR gene (χ2 = 17.7, P<0.0001). Among public NTS isolates from Mexico, those from cattle and poultry had the highest proportion of MDR genotypes. Our results suggest that attaining significant improvements in AMR meat safety requires the identification and removal (or treatment) of product harboring MDR NTS, instead of screening for Salmonella spp. or for isolates showing resistance to individual antibiotics. In that sense, massive integration of whole genome sequencing (WGS) technologies in AMR surveillance provides the shortest path to accomplish these goals.

Multidrug-Resistant Salmonella enterica Isolated in Paca (Cuniculus paca) Carcasses from the Belen Market, Iquitos, Perú

The consumption of wildlife meat is traditionally accepted in the Peruvian Amazon; however, little is known about the pathogens present in this type of food. One of the most frequently consumed species is a rodent, the paca (Cuniculus paca) or "majaz" in the Peruvian language. The objective of this study was to determine the presence of Salmonella enterica and its antimicrobial resistance profile in paca carcasses sold in the Belen Market of Iquitos-Peru. An observational, descriptive, cross-sectional study was carried out. Fresh and smoked paca carcasses (72 samples) were evaluated during the low-rain period (July 2019) in the traditional market of Iquitos, in the Amazonian Region. Meat samples were swabbed, and International Standards Organization (ISO) 6579-1: 2017 protocol was followed to Salmonella isolation. Antimicrobial susceptibility analysis was performed by the disk diffusion method. In addition, serotyping was performed by using the Kauffmann-White scheme. A total of 25 strains of S. enterica were isolated in the paca carcasses, mainly in fresh carcasses (48.6%). The serovars isolated were Agona (45.8%), Infantis (41.7%), Wangata (8.3%), and Javiana (4.2%). A considerable number of the isolated strains were multidrug resistant (40%). The highest prevalence of resistance corresponded to trimethoprim-sulfamethoxazole (64%) followed by nitrofurantoin (44%), chloramphenicol (40%), cefotaxime (40%), and nalidixic acid (40%). Ten strains isolated (40%) were identified as producers of extended spectrum beta lactamases, all in S. enterica serovar Infantis. This study describes the presence of Salmonella Infantis with multidrug resistance profiles in wildlife meat carcasses, making the consumption of this type of products a risk factor for the development of foodborne diseases in the Amazon region. Institutional Review Board: Approval Resolution of Thesis Project: N° 024-DACMVZ-DAFCVB-U.CIENTÍFICA-2019.

Phenotypic and genotypic characterization of Salmonella Typhimurium isolates from humans and foods in Brazil

Salmonella enterica subsp. enterica serovar Typhimurium (S. Typhimurium) causes gastroenteritis in many countries. However, in Brazil there are few studies that have conducted a virulence characterization of this serovar. The aim of this study was to evaluate the virulence potential of S. Typhimurium strains isolated in Brazil. Forty S. Typhimurium strains isolated from humans (n = 20) and food (n = 20) from Brazil were studied regarding their invasion and survival in human epithelial cells (Caco-2) and macrophages (U937). Their virulence potential was determined using the Galleria mellonella larvae model combined with the analysis of virulence genes by whole genome sequencing (WGS). A total of 67.5% of the S. Typhimurium studied (32.5% isolated from humans and 35% isolated from food) invaded Caco-2 epithelial cells at levels similar to or greater than the S. Typhimurium SL1344 prototype strain. In addition, 37.5% of the studied strains (25% isolated from humans and 12.5% isolated from food) survived in U937 human macrophages at levels similar to or greater than SL1344. S. Typhimurium strains isolated from humans (40%) and food (25%) showed high or intermediate virulence in G. mellonella larvae after seven days exposure. Approximately, 153 virulence genes of chromosomal and plasmidial origin were detected in the strains studied. In conclusion, the ability of the S. Typhimurium to invade Caco-2 epithelial cells was strain dependent and was not related to the source or the year of isolation. However, S. Typhimurium strains isolated from humans showed greater survival rates in U937 human macrophages, and presented higher proportion of isolates with a virulent profile in G. mellonella in comparison to strains isolated from food suggesting that this difference may be related to the higher frequency of human isolates which contained plasmid genes, such as spvABCDR operon, pefABCD operon, rck and mig-5.