Mexican unpasteurised fresh cheeses are contaminated with Salmonella spp., non-O157 Shiga toxin producing Escherichia coli and potential uropathogenic E. coli strains: A public health risk

Foodborne bacteria in milk and milk products along the water buffalo milk chain in Bangladesh

Controlling foodborne pathogens in buffalo milk is crucial for ensuring food safety. This study estimated the prevalence of nine target genes representing seven critical foodborne bacteria in milk and milk products, and identified factors associated with their presence in buffalo milk chain nodes in Bangladesh. One hundred and forty-three milk samples from bulk tank milk (n = 34), middlemen (n = 37), milk collection centers (n = 37), and milk product shops (n = 35) were collected and analyzed using RT-PCR. Escherichia (E.) coli, represented through yccT genes, was the most prevalent throughout the milk chain (81-97%). Chi-squared tests were performed to identify the potential risk factors associated with the presence of foodborne bacteria encoded for different genes. At the middleman level, the prevalence of E. coli was associated with the Mymensingh, Noakhali, and Bhola districts (P = 0.01). The prevalence of Listeria monocytogenes, represented through inlA genes, and Yersinia (Y.) enterocolitica, represented through yst genes, were the highest at the farm level (65-79%). The prevalence of both bacteria in bulk milk was associated with the Noakhali and Bhola districts (P < 0.05). The prevalence of Y. enterocolitica in bulk milk was also associated with late autumn and spring (P = 0.01) and was higher in buffalo-cow mixed milk than in pure buffalo milk at the milk collection center level (P < 0.01). The gene stx2 encoding for Shiga toxin-producing (STEC) E. coli was detected in 74% of the milk products. At the middleman level, the prevalence of STEC E. coli was associated with the use of cloths or tissues when drying milk containers (P = 0.01). Salmonella enterica, represented through the presence of invA gene, was most commonly detected (14%) at the milk collection center. The use of plastic milk containers was associated with a higher prevalence of Staphylococcus aureus, represented through htrA genes, at milk product shops (P < 0.05). These results suggest that raw milk consumers in Bangladesh are at risk if they purchase and consume unpasteurized milk.

Raw milk cheeses from Beira Baixa, Portugal-A contributive study for the microbiological hygiene and safety assessment

Due to specific bacterial microbiota, raw milk cheeses have appreciated sensory properties. However, they may pose a threat to consumer safety due to potential pathogens presence. This study evaluated the microbiological contamination of 98 raw milk cheeses from Beira Baixa, Portugal. Presence and enumeration of Coagulase Positive Staphylococci (CPS), Listeria monocytogenes, Salmonella spp., pathogenic Escherichia coli, and indicator microorganisms (non-pathogenic E. coli and Listeria spp.) was attained. E. coli antimicrobial resistance (AMR) was also evaluated. PCR and/or Whole genome sequencing (WGS) was used to characterize E. coli, Salmonella spp. and L. monocytogenes isolates. Sixteen cheeses (16.3%) were classified as Satisfactory, 59 (60.2%) as Borderline and 23 (23.5%) as Unsatisfactory/Potential Injurious to Health. L. monocytogenes, CPS > 104 cfu g-1, Extraintestinal pathogenic E. coli (ExPEC) and Salmonella spp. were detected in 4.1%, 6.1%, 3.1% and 1.0% of the samples, respectively. Listeria innocua (4.1%) and E. coli > 104 cfu g-1 (16.3%) were also detected. AMR E. coli was detected in 23/98 (23.5%) of the cheese samples, of which two were multidrug resistant. WGS identified genotypes already associated to human disease and Listeria spp. cluster analysis indicated that cheese contamination might be related with noncompliance with Good Hygiene Practices during cheese production.

Distribution and virulence of Escherichia coli harboring cyclomodulins and supplementary virulence genes isolates from clinical and environmental samples

This study aimed to determine the prevalence of cyclomodulins (cdt, cnf, pks and cif) in Escherichia coli (E. coli) isolated from clinical and environmental samples, the presence of supplementary virulence genes (SVG), antibiotic resistance, and in vitro cytotoxicity. 413 E. coli were isolated from clinical (stool from obese subjects, normal weight subjects, children with diarrhea, and children without diarrhea; and urine from pregnant and non-pregnant women with urinary tract infections) and environmental (water and different foods) samples. PCR was performed to identify E. coli pathotypes, the four cyclomodulins, and 18 SVG; virulence score, cytotoxic assay, and antibiotic resistance assay were performed. Fifteen percent of E. coli were positive for cyclomodulins and were found in all isolation sources; however, in children with diarrhea, they were more frequent. The most frequent cyclomodulin was cdt. More DEC strains harbor cyclomodulins than non-DEC, and cyclomodulins were most frequent among aEPEC pathotype. SVG ehaC was associated with cyclomodulin-positive strains. Cyclomodulin-positive E. coli had a higher virulence score but no significant cytotoxic activity. They were slightly more resistant to antibiotics. In conclusion, cyclomodulins-positive E. coli was widely distributed in humans, food, and the environment, and they were associated with SVG ehaC, suggesting that these genes may play a role in the pathogenesis of the cyclomodulins. However, more research is needed.

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.

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.

Isolation of Staphylococcus aureus, Uropathogenic Escherichia coli, and Nontuberculous Mycobacteria Strains from Pasteurized Cheeses and Unpasteurized Cream Sold at Traditional Open Markets in Mexico City

ABSTRACT

Fresh cheeses and cream are important garnishes of traditional Mexican food, often purchased at street or itinerant open markets or tianguis. However, there is scarce information regarding the microbiological quality of cheeses and cream sold in tianguis. For 2 years, three dairy stalls from three tianguis in Mexico City were visited once each season, trading practices were registered, and 96 dairy products were purchased. In total 72 fresh pasteurized cheeses that were hand-cut to order (24 Panela, 24 Canasto, and 24 Doble Crema) and 24 unpasteurized Crema de Rancho samples were collected. All dairy products remained without refrigeration for 8 h. Based on the National Guidelines limits, 87.5% of cheeses and 8% of Crema de Rancho samples were of low microbiological quality, and 1 sample of each type of cheese and 3 samples of Crema de Rancho exceeded the guidelines limits for Staphylococcus aureus. All dairy products were negative for Salmonella, Listeria monocytogenes, and all diarrheagenic Escherichia coli pathotypes, including Shiga toxin-producing E. coli. Among the 96 dairy samples, the prevalence of uropathogenic E. coli (UPEC) and of mycobacteria strains were determined because food items contaminated with these strains have been associated with urinary tract infections and mycobacteriosis, respectively. UPEC strains were isolated from 43% of cut-to-order cheeses and 29% of Crema de Rancho samples. Nontuberculous mycobacteria (NTM) strains were identified in 12.5% of Doble Crema cheese samples and 21% of Crema de Rancho samples. From the eight NTM-positive samples, 10 strains were identified (3 strains of Mycolicibacterium fortuitum, 2 of Mycobacteroides abscessus, 2 of Mycobacteroides chelonae, 2 of Mycolicibacterium porcinum, and 1 of Mycolicibacterium rhodesiae). All produced biofilms, and 70% had sliding motility (both virulence traits). Trading practices of cut-to-order pasteurized cheeses and unpasteurized Crema de Rancho in tianguis increase the risk of microbiological contamination of these products, including with human pathogens, and their consumption may cause human illness.

HIGHLIGHTS

Urinary tract virulence genes in extended-spectrum beta-lactamase E. coli from dairy cows, beef cattle, and small ruminants

Extended-spectrum β-lactamase Escherichia coli is an important cause of urinary tract infections in humans. ESBL producers E. coli were reported in food-producing animals, but no previous study reported the virulence potential of these isolates. Thus, this study determined the virulence potential of ESBL producers E. coli isolates from 518 beef feces, 610 dairy cow feces, 305 dairy cow milk, 503 sheep milk and 445 goat milk samples. A total of 278 isolates; specifically, 130 from beef feces, 39 from the cow's feces, 42 from cow's milk, 44 from sheep milk and 23 from goats' milk were isolated and then tested for 14 virulence genes by polymerase chain reaction. After that, the correlation of virulence genes presence among the isolates was determined statistically. Overall, 97% of the isolates carried fimH, 39% carried iroN _{E. coli} and 32% carried papC. The kpsMT K1, cnf1, papAH, papG allele II & III, papG allele II, and kpsMT II were carried by 6 to 23% of the isolates, while less than 6% of the isolates carried papG allele III, papG allele I, Univcnf, iutA and hlyA. About 68.2% of the isolates carried two or more virulence genes and 41.8% carried three or more. Moreover, the isolates had 71 different profiles of virulence genes, where the most common profiles were fimH alone (86 isolate), fimH + iroN _{E. coli} (35 isolate), fimH + papC (20 isolate), and fimH + papC + iroN _{E. coli} (13 isolate). The adhesion, capsule synthesis and toxins secretion genes were significantly associated (p ˂ 0.01) with each other. These results call for awareness about the risk of food animals as reservoirs of ESBL uropathogenic E. coli that would threaten public health and limits the treatment options for urinary tract infections.

Loads of Coliforms and Fecal Coliforms and Characterization of Thermotolerant Escherichia coli in Fresh Raw Milk Cheese

The aim of this study was to assess the hygienic status of raw milk cheese and determine the trends of virulence and antimicrobial resistance in thermotolerant Escherichia coli. Two hundred samples of karish, a popular Egyptian fresh raw milk cheese, were analyzed for coliforms and fecal coliforms using a standard most probable number (MPN) technique. Overall, 85% of samples were unsuitable for consumption, as they exceeded Egyptian standards for coliforms (10 MPN/g), and 65% of samples exhibited coliforms at 44.5 °C. Of 150 recovered thermotolerant strains, 140 (93.3%) were identified as E. coli. Importantly, one Shiga toxin-producing E. coli (STEC) strain carrying a striking virulence pattern, stx1−, stx2+, eae−, was detected. Eleven strains (7.8%, 11/140) showed resistance to third-generation cephalosporins. Antibiotic resistance genes included bla_SHV, bla_CTX-M, qnrS, tet(A), and tet(B), which were present in 4.3%, 2.8%, 0.71%, 2.1%, and 0.71% of isolates, respectively. In conclusion, this study indicated that hygienic-sanitary failures occurred throughout the production process of most retail karish cheese. Furthermore, our findings emphasize the need for adopting third-generation cephalosporin-resistant E. coli as an indicator for monitoring antimicrobial resistance in raw milk cheese to identify the potential public health burden associated with its consumption.

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.

Microbiological Characteristics and Behavior of Staphylococcus aureus, Salmonella spp., Listeria monocytogenes and Staphylococcal Toxin during Making and Maturing Cotija Cheese

Cotija cheese is an artisanal matured Mexican cheese from unpasteurized milk. This work determined the microbiological characteristics and behavior of Staphylococcus aureus, Salmonella spp., Listeria monocytogenes and staphylococcal toxin during cheese elaboration and ripening. Sixteen 20-kg cheeses were used, eight inoculated with 6 log CFU/mL of each pathogen, and eight uninoculated, and samples were taken at each stage of the process. In the uninoculated samples, the survival of S. aureus and L. monocytogenes decreased after 30 days of ripening. The average counts of S. aureus in milk, curd, and serum were 7 log MPN /mL, and 8.7 log MPN /g in cheese, decreasing from day 15. Salmonella spp. counts (initial inoculum: 7.2 log MPN /mL) decreased after 24 h, and L. monocytogenes counts (8.7 log MPN/g at 24 h) decreased from day 15 in the cheese. Salmonella spp. and L. monocytogenes were not detected in any sample after 60 days of ripening, unlike S. aureus, which was detected at the end of the study. Lactic acid bacteria counts were 9 log CFU/mL in milk and whey and 7.2 log CFU/g in cheese. Pathogens behavior during the ripening process reduces the health risks by consuming products made with unpasteurized milk when subjected to ripening.

Escherichia coli Specific Virulence-Gene Markers Analysis for Quality Control of Ovine Cheese in Slovakia

Shiga toxin-producing and extra-intestinal pathogenic Escherichia coli (E. coli) have the potential to spread through faecal waste, resulting in contamination of food and causing foodborne disease outbreaks. With the aim of characterizing unpasteurized ovine cheese in Slovakia, a total of 92 E. coli strains were examined for eleven representative virulence genes typical for (extra-)intestinal pathogenic E. coli and phylogenetic grouping. Phylogenetic groups B1 (36%) and A (32%) were the most dominant, followed by groups C (14%) and D (13%), while the lowest incidence was recorded for F (4%), and E (1%), and 43 (47%) samples carried at least one virulent gene, i.e., potential pathogens. Isolates present in groups E, F and D showed higher presence of virulence genes (100%, 75%, and 67%), versus 55%, 39%, and 28% in commensal B1, C, and A, respectively. Occurrence of papC and fyuA (both 24%) was highest, followed by tsh, iss, stx2, cnf1, kpsII, cvaC, stx1, iutA and eaeA. Nine E. coli strains (almost 10% of all tested and around 21% of our virulence-gene-associated isolates) harboured stx1, stx2 or eae. Ovine cheeses in Slovakia are highly contaminated with E. coli including potentially pathogenic strains capable of causing intestinal and/or extra-intestinal diseases, and thus may pose a threat to public health while unpasteurized.

New Insights Into DAEC and EAEC Pathogenesis and Phylogeny

Diarrheagenic E. coli can be separated into six distinct pathotypes, with enteroaggregative (EAEC) and diffusely-adherent E. coli (DAEC) among the least characterized. To gain additional insights into these two pathotypes we performed whole genome sequencing of ten DAEC, nine EAEC strains, isolated from Mexican children with diarrhea, and one EAEC plus one commensal E. coli strains isolated from an adult with diarrhea and a healthy child, respectively. These genome sequences were compared to 85 E. coli genomes available in public databases. The EAEC and DAEC strains segregated into multiple different clades; however, six clades were heavily or exclusively comprised of EAEC and DAEC strains, suggesting a phylogenetic relationship between these two pathotypes. EAEC strains harbored the typical virulence factors under control of the activator AggR, but also several toxins, bacteriocins, and other virulence factors. DAEC strains harbored several iron-scavenging systems, toxins, adhesins, and complement resistance or Immune system evasion factors that suggest a pathogenic paradigm for this poorly understood pathotype. Several virulence factors for both EAEC and DAEC were associated with clinical presentations, not only suggesting the importance of these factors, but also potentially indicating opportunities for intervention. Our studies provide new insights into two distinct but related diarrheagenic organisms.

Genetic diversity and antibiotic susceptibility of uropathogenic Escherichia coli isolates from kidney transplant recipients

Purpose

Uropathogenic Escherichia coli (UPEC) strains are a common cause of transplant rejection, morbidity, and mortality among kidney transplant recipients. The virulence of UPEC strains differs based on their pathogenicity islands (PAIs) and susceptibility to antibiotics. The present study evaluates the clonal relationship and antibiotic susceptibility of UPEC PAI-genotypes among Escherichia coli (E. coli) isolates from kidney transplant patients.

Patients and methods

A total of 115 Escherichia coli (E. coli) isolates were collected from kidney transplant recipients with acute urinary tract infections (UTIs). Isolates were typed based on the presence of PAI-markers, and random amplified polymorphic DNA (RAPD). The disk diffusion method was performed for the antibiotic susceptibility pattern of isolates.

Results

According to the PAI-specific virulence markers, 69 (60%), 21 (18.3%), and 25 (21.7%) isolates were identified as genotypes related to UPEC 536, UPEC J96, and UPEC CFT073 strains, respectively. PAI III536 genotypes were the most prevalent genotype in this study. The findings showed a high-sensitivity to imipenem (93.9%) and nitrofurantoin (91.3%) and a low-sensitivity to trimethoprim/sulfamethoxazole (36.5%). Clonal association and similar antibiotic susceptibility pattern were seen in the PAI-related genotypes.

Conclusion

Due to a similar pattern of antibiotic susceptibility of these clonal groups and increased resistance to some important antibiotics such as trimethoprim/sulfamethoxazole in the treatment of urinary tract infections, especially in kidney transplant patients, the spread of these clones should be considered as a serious concern.

Virulence factors, prevalence and potential transmission of extraintestinal pathogenic Escherichia coli isolated from different sources: recent reports

Extraintestinal pathogenic E. coli (ExPEC) are facultative pathogens that are part of the normal human intestinal flora. The ExPEC group includes uropathogenic E. coli (UPEC), neonatal meningitis E. coli (NMEC), sepsis-associated E. coli (SEPEC), and avian pathogenic E. coli (APEC). Virulence factors (VF) related to the pathogenicity of ExPEC are numerous and have a wide range of activities, from those related to bacteria colonization to those related to virulence, including adhesins, toxins, iron acquisition factors, lipopolysaccharides, polysaccharide capsules, and invasins, which are usually encoded on pathogenicity islands (PAIs), plasmids and other mobile genetic elements. Mechanisms underlying the dynamics of ExPEC transmission and the selection of virulent clones are still poorly understood and require further research. The time shift between colonization of ExPEC and the development of infection remains problematic in the context of establishing the relation between consumption of contaminated food and the appearance of first disease symptoms. What appears to be most difficult is to prove that ExPEC strains cause disease symptoms and to examine the mechanism of transition from the asymptomatic colonization of the intestines to the spreading of the bacteria outside the digestive system. A significant problem for researchers who are trying to ascribe ExPEC transmission to food, people or the environment is to draw the distinction between colonization of ExPEC and infection. Food safety is an important challenge for public health both at the production stage and in the course of its processing and distribution. Examination of the genetic similarity of ExPEC strains will allow to determine their origin from different sources. Many levels of genotyping have been proposed in which the typing of strains, plasmids and genes is compared in order to obtain a more complete picture of this complex problem. The aim of our study was to characterize E. coli strains isolated from humans, animals and food for the presence of bacterial genes encoding virulence factors such as toxins, and iron acquisition systems (siderophores) in the context of an increasing spread of ExPEC infections.

Salmonella Prevalence and Antimicrobial Drug Resistance in Dual-Purpose Cattle Operations in the Eastern Region of Zulia State, Venezuela

To evaluate the Salmonella prevalence and its antimicrobial susceptibility in dual-purpose cattle farms, fecal (n = 3964; from cows and calves) and environmental samples (n = 334; personnel, feed, and water sources) were collected over a 1-year period at six farms in the eastern region of Zulia State, Venezuela. Salmonella detection was carried out using standard microbiological culture methods. From 453 isolated Salmonella, antimicrobial susceptibility was tested using a panel of 10 antibiotics by the disk diffusion test method. Overall, the prevalence of Salmonella at the farm was 10.4% (n = 410/3964), being positive for Salmonella in at least in one sample. Salmonella was found in 11% (222/2009) of cows and 9.7% (188/1937) of calves. The prevalence of environmental samples was 10.78% (36/334), where water sources and milkers' hands showed higher occurrence (p < 0.01). Among the Salmonella isolates recovered, 10.2% displayed resistance to tetracyclines, aminoglycosides, cephalosporins, penicillins, sulfonamides, quinolones and fluoroquinolones. Overall, multidrug resistance was 9.1%, and the most common combination was cephalothin-gentamicin-tetracycline, followed by gentamicin-norfloxacin-tetracycline. Over the course of this study, it was found that 100% of the evaluated farms had cattle shedding Salmonella and that the surrounding farm environments were contaminated, which contributed to the cycling of the pathogen at the farms and further contamination of the milk. However, only a low percentage of isolates exhibited significant antimicrobial resistance.

Presence of Multidrug-Resistant Shiga Toxin-Producing Escherichia coli, Enteropathogenic Escherichia coli, and Enterotoxigenic Escherichia coli on Fresh Cheeses from Local Retail Markets in Mexico

Cheesemaking is one of the most important industries in Mexico. Among all the Mexican cheeses, fresh cheeses are the most popular and most consumed cheese in Mexico and Latin America. However, in Mexico fresh cheese is frequently made with unpasteurized milk and sold in public markets. This may increase the risk for contamination of dairy products with pathogenic bacteria. The presence of multidrug-resistant pathogenic bacteria in food is an important public health concern. Diarrheagenic Escherichia coli pathotypes (DEPs) are foodborne bacteria. This study investigated the presence of indicator bacteria and multidrug-resistant DEPs in fresh cheeses. A total of 120 fresh cheese samples were collected from public markets in the city of Pachuca, Mexico. The samples were analyzed for presence of fecal coliforms (FC), E. coli, and antibiotic resistant DEPs. FC and E. coli were analyzed using the most-probable-number technique. DEPs were identified using two multiplex PCR methods. Susceptibility to 16 antibiotics was tested for the isolated DEPs strains by the standard assay. The frequency of FC, E. coli, and DEPs in the cheese samples was 50, 40, and 19%, respectively. The identified DEPs included Shiga toxin-producing E. coli (STEC; 8%), enteropathogenic E. coli (EPEC; 6%), and enterotoxigenic E. coli (ETEC; 5%). All isolated strains exhibited resistance to at least five antibiotics. One, one, two, and three STEC strains were resistant to 14, 12, 11, and 10 antibiotics, respectively. One strain of EPEC was resistant to 11 antibiotics, three EPEC strains to 9, and one strain to 7. One, one, and two strains of ETEC were resistant to 10, 8, and 7 antibiotics, respectively. The results of the present study indicate that fresh cheeses made with unpasteurized milk could be a risk for consumers, both for native people and visitors to Mexico.

Multi-Year Persistence of Verotoxigenic Escherichia coli (VTEC) in a Closed Canadian Beef Herd: A Cohort Study

In this study, fecal samples were collected from a closed beef herd in Alberta, Canada from 2012 to 2015. To limit serotype bias, which was observed in enrichment broth cultures, Verotoxigenic Escherichia coli (VTEC) were isolated directly from samples using a hydrophobic grid-membrane filter verotoxin immunoblot assay. Overall VTEC isolation rates were similar for three different cohorts of yearling heifers on both an annual (68.5 to 71.8%) and seasonal basis (67.3 to 76.0%). Across all three cohorts, O139:H19 (37.1% of VTEC-positive samples), O22:H8 (15.8%) and O?(O108):H8 (15.4%) were among the most prevalent serotypes. However, isolation rates for serotypes O139:H19, O130:H38, O6:H34, O91:H21, and O113:H21 differed significantly between cohort-years, as did isolation rates for some serotypes within a single heifer cohort. There was a high level of VTEC serotype diversity with an average of 4.3 serotypes isolated per heifer and 65.8% of the heifers classified as "persistent shedders" of VTEC based on the criteria of >50% of samples positive and ≥4 consecutive samples positive. Only 26.8% (90/336) of the VTEC isolates from yearling heifers belonged to the human disease-associated seropathotypes A (O157:H7), B (O26:H11, O111:NM), and C (O22:H8, O91:H21, O113:H21, O137:H41, O2:H6). Conversely, seropathotypes B (O26:NM, O111:NM) and C (O91:H21, O2:H29) strains were dominant (76.0%, 19/25) among VTEC isolates from month-old calves from this herd. Among VTEC from heifers, carriage rates of vt1, vt2, vt1+vt2, eae, and hlyA were 10.7, 20.8, 68.5, 3.9, and 88.7%, respectively. The adhesin gene saa was present in 82.7% of heifer strains but absent from all of 13 eae+ve strains (from serotypes/intimin types O157:H7/γ1, O26:H11/β1, O111:NM/θ, O84:H2/ζ, and O182:H25/ζ). Phylogenetic relationships inferred from wgMLST and pan genome-derived core SNP analysis showed that strains clustered by phylotype and serotype. Further, VTEC strains of the same serotype usually shared the same suite of antibiotic resistance and virulence genes, suggesting the circulation of dominant clones within this distinct herd. This study provides insight into the diverse and dynamic nature of VTEC populations within groups of cattle and points to a broad spectrum of human health risks associated with these E. coli strains.

Milk Fat Globules Hamper Adhesion of Enterohemorrhagic Escherichia coli to Enterocytes: In Vitro and in Vivo Evidence

Enterohemorrhagic Escherichia coli (EHEC; E. coli) are food-borne agents associated with gastroenteritis, enterocolitis, bloody diarrhea and the hemolytic-uremic syndrome (HUS). Bovine milk glycans have been shown to contain oligosaccharides which are similar to host epithelial cell receptors and can therefore prevent bacterial adhesion. This study aimed to describe interactions between EHEC O157:H7 EDL933 and O26:H11 21765 and milk fat globules (MFGs) in raw milk and raw milk cheese, and the impact of MFGs on EHEC strains adhesion to the intestinal tract in vitro and in vivo. Both EHEC serotypes clearly associated with native bovine MFGs and significantly limited their adhesion to a co-culture of intestinal cells. The presence of MFGs in raw milk cheese had two effects on the adhesion of both EHEC serotypes to the intestinal tracts of streptomycin-treated mice. First, it delayed and reduced EHEC excretion in mouse feces for both strains. Second, the prime implantation site for both EHEC strains was 6 cm more proximal in the intestinal tracts of mice fed with contaminated cheese containing less than 5% of fat than in those fed with contaminated cheese containing 40% of fat. Feeding mice with 40% fat cheese reduced the intestinal surface contaminated with EHEC and may therefore decrease severity of illness.

Molecular characterization of diarrheagenic Escherichia coli pathotypes: Association of virulent genes, serogroups, and antibiotic resistance among moderate-to-severe diarrhea patients

BACKGROUND

Diarrheagenic Escherichia coli (DEC) signifies as an important etiological agent of moderate-to-severe diarrhea. This study was primarily focused on molecular identification of DEC pathotypes; their association with serogroups and estimates of resistance profiles against different antibiotics regime.

METHODS

Five hundred seventy-two stool specimens from diarrhea patients were investigated for DEC pathotypes. Molecular pathotypes were identified by amplification of virulence genes associated with distinct pathotypes followed by sequencing. Diarrhea is a self-limiting disease, however, severity and persistence of infection suggest antibiotic use. Therefore, AST and MIC were determined against common antibiotic regimen. Correlations between molecular pathotypes and serogroups were analyzed by somatic "O" antigen serotyping.

RESULTS

The present findings reveal incidence of DEC as an etiological agent up to a level of 21% among all diarrheal age groups. DEC infection rate was higher in children. Enteropathogenic E. coliEPEC, a molecular pathotype of DEC, was found as a predominant pathotype with highest frequency of 13.7%. Two other molecular pathotypes enterotoxigenic E. coli (ETEC) and enteroaggregative E. coli (EAEC) accounted for 5.7% and 1.3%, respectively for all diarrhea incidences. Serological analysis deciphered somatic antigens O26, O2, and O3 as major serogroups identified among EPEC, ETEC, and EAEC pathotypes, respectively. All DEC pathotypes exhibited high levels of antibiotic resistance except for cotrimoxazole and norfloxacin.

CONCLUSION

Comprehensive molecular characterization of DEC pathotypes, their incidence estimates, and antibiogram patterns will help in ascertaining better diagnostic and therapeutic measures in management of diarrheal diseases.

Microbiological criteria and ecology of commercially available processed cheeses according to the product specification and physicochemical characteristics

Although global cheese manufacturers release a variety of products onto the market, research on the microbiological quality and safety of cheese has focused mainly on conventional cheeses made from milk. Here, this study aimed to investigate commercially processed cheese products produced by mixing conventional cheeses after melting. Two approaches were used: a summary and comparison of legal definitions and standards/regulations regarding the microbiological criteria used by major cheese traders in the global market (Australia/New Zealand, China, European Union, Japan, Mexico, Republic of Korea, and the United States) and a comprehensive microbiological analysis of commercial products (n = 800), along with an assessment of salinity, pH, water activity, and heating conditions. The results of the literature search showed that major importing countries (China, Japan, Mexico, and the Republic of Korea) have stricter microbiological criteria for commercially available cheese products than major exporters (Australia/New Zealand, EU, and the USA). The former set limits with respect to the number of total coliforms in the product. Microbiological analyses were designed according to global standards and recommendations. No test sample contained detectable levels of Clostridium perfringens, enterohemorrhagic Escherichia coli, Listeria monocytogenes, Salmonella, or Staphylococcus aureus. In addition, no coliform bacteria (including E. coli) were detected. Overall, 79.9% of the samples contained detectable aerobic plate counts (1.0-7.8 log CFU/g); these levels varied significantly according to product type (grated cheese > chunks; cream cheese > portions or sliced) (p < .05). There was no significant association between microbe levels and salinity, water activity, pH, and heating conditions. The results can be used to develop a comprehensive database about commercially processed cheese products available in the global market and, as such, may be helpful for both national authorities and cheese manufacturers when considering novel strategic management plans for microbiological quality and safety.

Virulence Genes and Antimicrobial Resistance in Escherichia coli from Cheese Made from Unpasteurized Milk in Brazil

Cow raw milk cheese is widely eaten in Brazil. These products may be contaminated with pathogenic bacteria. In this work, we investigated the presence of Escherichia coli in raw milk cheese from different States in Brazil. From 147 "Minas" cheese samples, 28 cheeses were positive for E. coli. Among 39 E. coli isolates of the cheeses, one was positive for eae and negative for bpfA and efa1/lifA using PCR, and so was classified as atypical Enteropathogenic E. coli (aEPEC). Two other isolates were positive for extraintestinal pathogenic E. coli (ExPEC) genes. The aEPEC isolate belongs to serogroup O127 and was classified in A phylogenetic group, and ExPEC isolates were found in O73:H12 (EC-2 strain) and O64474:H8 (EC-9 strain) serotype. This ExPEC belongs to A and C phylogenetic group, respectively. Most of E. coli strains belonged to Clermont phylogenetic groups A (28.2%), C, and E (23.1%). Six strains (15.4%) of E. coli were positive for group B1 and two (5.1%) for B2. E. coli isolates presented an aggregative (46.0%) and diffuse (12.6%) adherence pattern to HeLa cells, and the other isolates did not show adhesion (41.4%). Four E. coli isolates (10.3%) were shown to produce moderate biofilm. The antimicrobial resistance rate was tetracycline (25.6%), followed by ampicillin (17.9%), cefoxitin (7.7%), nalidixic acid (5.1%), and amoxicillin-clavulanic acid (2.6%). One strain was resistant to three antimicrobials (tetracycline, ampicillin, and nalidixic acid). The presence of these microorganisms, the O127 strain, and a new serogroup in Brazil is a potential risk for public health.

Recent Advances on Magnetic Relaxation Switching Assay-Based Nanosensors

Magnetic relaxation switching assay (MRSw)-based nanosensors respond to the changes of transverse relaxation time (T₂) of water molecules resulted from the analyte-induced aggregation and disaggregation of magnetic nanoparticles (MNPs). This strategy has been widely applied to the detections of various substrates from heavy metal ions to organic pollutants, proteins, nucleic acids, bacteria and viruses, and specific cells. Compared with other nanosensors, MRSw-based nanosensors not only are free from the background interferences, signal bleaching, and quenching but also overcome light scattering from samples without pretreatments. Therefore, MRSw-based nanosensors have been developed as real-time and on-site detection platforms for environmental protection, food safety, and risk assessment. This review summarizes the latest developments of the principles, the applicable magnetic nanoparticles, and the exploited environmental and biological applications of MRSw-based nanosensors.