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Shiga toxin-producing Escherichia coli (STEC) are zoonotic enteric pathogens linked to human gastroenteritis worldwide. To aid the development of pathogen control efforts, the present study characterized the genotypic diversity and pathogenic potential of STEC recovered from sources near agricultural fields in Northwest Mexico. Samples were collected from irrigation river water and domestic animal feces in farms proximal to agricultural fields and were subjected to enrichment followed by immunomagnetic separation and plating on selective media for the recovery of the STEC isolates. Comparative genomic analyses indicated that the recovered STEC with the clinically relevant serotypes O157:H7, O8:H19, and O113:H21 had virulence genes repertoires associated with host cell adherence, iron uptake and effector protein secretion. Subsequent phenotypic characterization revealed multidrug resistance against aminoglycoside, carbapenem, cephalosporin, fluoroquinolone, penicillin, phenicol, and tetracycline, highlighting the need for improved surveillance on the use of antimicrobials. The present study indicated for the first time that river water in the agricultural Culiacan Valley in Mexico is a relevant key route of transmission for STEC O157 and non-O157 with a virulence potential. In addition, feces from domestic farm animals near surface waterways can act as potential point sources of contamination and transport of diverse STEC with clinically relevant genotypes.

Background Antimicrobial resistance in Shiga toxin-producing Escherichia coli (STEC) O157 and non-O157 is a matter of increasing concern. The aim of the present study was to investigate the antimicrobial resistance profiles of STEC O157 and non-O157 recovered from feces of domestic farm animals in the agricultural Culiacan Valley in Northwestern Mexico. Findings All of the examined STEC strains showed susceptibility to five antimicrobials, ceftazidime, ceftriaxone, ciprofloxacin, nalidixic acid, and trimethoprim-sulfamethoxazole. However, resistance to the four antimicrobials, ampicillin, cephalothin, chloramphenicol, and kanamycin was commonly observed. Interestingly, non-susceptibility to cephalothin was predominant among the examined STEC strains, corresponding to 85 % (22/26) of the O157:H7 from cattle, sheep and chicken and 73 % (24/33) of the non-O157 strains from cattle and sheep. Statistical analyses revealed that resistance to ampicillin was significantly correlated to 38 % (10/26) of STEC O157:H7 strains from multiple animal sources. Another significant correlation was found between serotype, source, and antimicrobial resistance; all of the O20:H4 strains, recovered from sheep, were highly resistant to tetracycline. Multidrug resistance profiles were identified in 42 % (22/53) of the non-susceptible STEC strains with clinically-relevant serotypes O8:H9, O75:H8, O146:H21, and O157:H7. Conclusions STEC O157 and non-O157 strains, recovered from domestic farm animals in the Culiacan Valley, exhibited resistance to classes of antimicrobials commonly used in Mexico, such as aminoglycosides, tetracyclines, cephalosporins and penicillin but were susceptible to fluoroquinolones, quinolones, and sulfonamides. These findings provide fundamental information that would aid in the surveillance of antimicrobial resistance in an important agricultural region in Northwestern Mexico.

Foodborne bacteria, with a high degree of antibiotic resistance, play an important role in the morbidity and mortality of gastrointestinal diseases worldwide. Among 250 disease-causing bacteria, Staphylococcus aureus is one of the major causes of food poisoning, and its resistance to multiple antimicrobials remains of crucial concern. Cheese is often contaminated when proper sanitary procedures are not followed during its production and marketing. This work aimed to evaluate the microbiological quality of pasteurized white cheese commercialized in Panama City. Cheese from five different brands sold in local supermarkets were selected to determine the presence of S. aureus as well as its antibiotic resistance profile. The results showed significant contamination of S. aureus with a geometric median sample of 104–107 CFU/g. Four out of five (4/5) cheese brands analyzed presented risk of food poisoning by exceeding the allowed range of consumption with a geometric median sample of 1,8 × 106–1,4 × 107 CFU/g. Fourteen different resistance phenotypes were found. Fifty-five percent (55%) of the analyzed strains were resistant to erythromycin. The data confirm a relatively high prevalence and high levels of S. aureus, most likely originated during handling in Panama City retail markets. Further studies are needed to reduce bacterial contamination and to decrease the risk of food poisoning in the consumption of pasteurized cheese.

Ozonized oils are antimicrobial agents obtained from the combination of ozone and unsaturated fatty acids of vegetables oils. The aim of the present study was to evaluate the antimicrobial effectiveness of ozonized olive oil (OOO) and ozonized venadillo oil (OVO) against Escherichia coli and Staphylococcus aureus. The antibacterial activity was conducted by the agar dilution method to determine the minimum inhibitory concentration (MIC) and the bacterial Log10 reduction. The lowest MIC (4.5 mg/mL) against E. coli was obtained when OOO and OVO were ozonized during 12 and 6 hours, with 2.5 Log10 of bacterial reduction, respectively; while, the lowest MIC against S. aureus (1.5 mg/mL) was obtained when OVO was ozonized during 6 hours, with 3.4 Log10 of bacterial reduction. The OOO reached peroxide values of 642.53 and 703.7 mmol-equiv/kg after 6 and 12 hours, respectively, while an 892.12 mmol-equiv/kg was obtained after 6 hours for OVO. Data reported here suggest that both ozonized oils are promising effective treatment for bacterial infections.

A rise in foodborne outbreaks in the United States associated with fresh produce has resulted in increased concerns with the importation of fruits and vegetables. Mexico is a major exporter of produce to the United States, particularly tomatoes and bell peppers. A quantitative microbial risk assessment (QMRA) was conducted to evaluate the public health impact of protozoan-laden water irrigating produce in Culiacan, Sinaloa, Mexico. Specifically, a QMRA was conducted to address the human health impact associated with consumption of tomatoes, bell peppers, cucumbers, and lettuce irrigated with water contaminated with Cryptosporidium and Giardia. Yearly infection risks were estimated and assumed a 120-day exposure in a given year. Annual risks range from 9 × 10(−6) for Cryptosporidium at the lowest concentration associated with bell peppers to almost 2 × 10(−1) for exposure to Giardia on lettuce at the highest detected concentration. With the relatively high number of illnesses resulting from produce-related outbreaks, addressing pre- and postharvest points of contamination for fruits and vegetables consumed raw should be a food industry priority. This research shows how QMRA can be used to interpret microbial contamination data for public health significance and subsequently provide the foundation for guideline development.

Untreated sewage has adversely affected the quality of marine recreational waters worldwide. Exposure to marine recreational water with poor microbial quality may pose a threat to bathers. The objectives of this study were to assess the effect of physicochemical parameters on Cryptosporidium and Giardia presence in marine recreational water of Sinaloa, Mexico, by Logistic Regression Analyses. Thirty-two 10-litre water samples were collected from two tourist beaches, Altata and Mazatlan, between November 2006 and May 2007. Water samples were processed by the EPA 1623 method and pH, temperature, salinity and turbidity were also determined. Cryptosporidium and Giardia were present in 71 and 57% of the samples collected from Altata, respectively. In Mazatlan, Cryptosporidium and Giardia were found in 83 and 72% of the samples, respectively. The overall concentration of Cryptosporidium ranged from 150 to 2,050 oocysts/10 L with an average of 581 oocysts/10 L and Giardia ranged from 10 to 300 cysts/10 L with an average of 73 cysts/10 L. The occurrence of both parasites increased in water with decreasing temperatures and increasing turbidity of the water.

Water quality, and therefore human health, may be significantly affected by the presence of pathogenic enteric microorganisms derived for improper disposal of wastewater to aquatic environments. Detection of waterborne viruses is complex due to the difficulties in concentrating the sample and then in detecting the virus by cell culture or molecular techniques. Methods used to concentrate enteric viruses from water have remained largely unchanged for nearly 30 years. The U.S. Environmental Protection Agency requires the use of 1MDS electropositive filters for concentrating enteric viruses from water; however, these filters are expensive for routine viral monitoring. The NanoCeram® filter, an electropositive cartridge filter, has been proposed as a new alternative for large volumes of water. The objective of the study was: to evaluate the effectiveness of NanoCeram® filters for the concentration of poliovirus-1 from wastewater samples and compare to 1MDS cartridge filters. This study suggested that NanoCeram® filters are a viable alternative to the use of 1MDS filters for viral monitoring in surface waters and wastewaters. L. monocytogenes outbreaks with Latin-style soft cheese have been well-documented; however, more information to characterize the human health risk associated with the consumption of queso fresco (QF) using unpasteurized milk is needed. The objectives of the study were: (i) to evaluate the prevalence of Listeria, Escherichia coli, Salmonella and fecal coliforms in QF obtained from markets in the northwestern state of Sinaloa, Mexico, and (ii) to address the human health impact associated with the consumption of QF contaminated with L. monocytogenes using quantitative microbial risk assessment (QMRA). The study suggested that QF produced in Culiacan, Sinaloa, Mexico have microbial loads above the maximum values recommended by the Official Mexican Regulations; and QMRA can be used to interpret microbial contamination data for impacts on public health.