Shiga toxin-producing Escherichia coli isolated from pasteurized dairy products from Bahia, Brazil

The presence of pathogenic Shiga toxin-producing Escherichia coli (STEC) in dairy products represents a public health concern because of its ability to produce the toxins Stx1 and Stx2, which cause intestinal diseases. Monitoring the stages of milk production and checking dairy products for contamination are crucial steps to ensure dairy safety. This study aimed to report the occurrence of thermotolerant coliforms, E. coli, and STEC strains in pasteurized dairy products and to evaluate the antibiotic resistance profiles, serotypes, and characterizations of the STEC isolates by pulsed-field gel electrophoresis. We obtained a total of 138 pasteurized dairy products from 15 processing plants in Bahia, Brazil, to examine coliforms, E. coli, and STEC strains. We found that 43% of samples (59/138) contained thermotolerant coliforms, and 30% (42/138) did not comply with Brazilian regulations. Overall, 6% (9/138) were positive for E. coli and 4% (5/138) were positive for STEC. We recovered 9 STEC isolates from pasteurized cream (2/9), Minas Padrão cheese (2/9), Minas Frescal cheese (4/9), and ricotta (1/9). All isolates were stx2-positive, and 2 were eae-positive. All isolates were negative for the "big 6" STEC serogroups, belonging instead to serotypes ONT:HNT, ONT:H12, O148:H-, OR:H40, OR:HNT, and O148:HNT. Pulsed-field gel electrophoresis revealed 100% genetic similarity among 3 isolates from 2 different samples produced in the same production facility, which may suggest cross-contamination. As well, we found isolates that were 98% similar but in samples produced in different production facilities, suggesting a mutual source of contamination or a circulating strain. Two STEC strains exhibited resistance to streptomycin. Although the isolates presented a low resistance profile and no strain belonged to the "big 6" pathogenic group, the circulation of stx2-positive STEC strains in ready-to-eat products highlights the importance of epidemiological surveillance inside the Brazilian dairy chain.

Worldwide Epidemiology of Salmonella Serovars in Animal-Based Foods: a Meta-analysis

Salmonella spp. are among the most important foodborne pathogens and the third leading cause of human death among diarrheal diseases worldwide. Animals are the primary source of this pathogen, and animal-based foods are the main transmission route to humans. Thus, understanding the global epidemiology of Salmonella serovars is key to controlling and monitoring this bacterium. In this context, this study aimed to evaluate the prevalence and diversity of Salmonella enterica serovars in animal-based foods (beef, pork, poultry, and seafood) throughout the five continents (Africa, the Americas [North and Latin America], Asia, Europe, and Oceania). The meta-analysis consisted of a chemometric assessment (hierarchical cluster analysis and principal component analysis) to identify the main epidemiological findings, including the prevalence and diversity of the Salmonella serovars in each matrix. Regarding the serovar distribution, S Typhimurium presented a cosmopolitan distribution, reported in all four assessed matrices and continents; poultry continues to play a central role in the dissemination of the Enteritidis serovar to humans, and Anatum and Weltevreden were the most frequently found in beef and seafood, respectively. Additionally, we recommended careful monitoring of certain serovars, such as Derby, Agona, Infantis, and Kentucky. Finally, given the scientific data regarding the most frequently reported serovars and which matrices constitute the main vehicles for the transmission of this pathogen, control programs may be improved, and specific interventions may be implemented in an attempt to reduce the risk of this pathogen reaching humans.IMPORTANCE Salmonellosis is caused by Salmonella spp. and is the third leading cause of death among food-transmitted diseases. This pathogen is commonly disseminated in domestic and wild animals, and the infection's symptoms are characterized by acute fever, nausea, abdominal pain, and diarrhea. The animals are the primary source of salmonellae, and animal-based foods are the main transmission route to humans. Therefore, data collected from these sources could contribute to future global interventions for effective control and surveillance of Salmonella along the food chain. In light of this, the importance of our research is in identifying the prevalence of Salmonella serovars in four animal-based food matrices (pork, poultry, beef, and seafood) and to evaluate the importance that each matrix has as the primary source of this pathogen to humans.

The urban and rural capybaras (Hydrochoerus hydrochaeris) as reservoir of Salmonella in the western Amazon, Brazil

ABSTRACT: The capybara (Hydrochoerus hydrochaeris) is the largest rodent in the world. In the state of Acre, Brazil, populations of capybaras have been increasing significantly. The role of capybaras in the transmission of certain bacterial zoonotic infections is not well understood, including bacteria of the genus Salmonella. Salmonella spp. generally cause enteritis or septicemia in mammals, however many mammalian species can carry the bacteria asymptomatically and shed it in their feces. To better understand the possible role of capybaras as reservoirs of Salmonella spp., we conducted a study of Salmonella within fecal samples from capybara in Acre. In a convenience sample, 54 capybaras from two urban and two rural areas of Acre were captured and kept for three to four days for sampling. None of the animals were symptomatic of any intestinal illness. Three separate fecal samples were collected from each animal, during their stays in captivity. Each sample was cultured for the presence of Salmonella spp. at the bacteriology laboratory of the Veterinary College of the Federal University of Acre. Samples were seeded in tetrationate pre-enrichment broth and in pre-enrichment broth peptone. After a 24 hour of incubation all samples were streaked on MacConkey Agar (MC) and Salmonella-Shigella Agar (SS). Suggestive colonies were submitted to biochemical analysis. Salmonella compatible colonies according to biochemical profile were submitted to serotyping (Sorokit for Salmonella - Probac do Brasil). In addition, the first sample from each of the 54 capybara was tested for Salmonella spp. using PCR targeting gene hilA. Eight (5%) of the 162 samples examined by bacterial culture were positive for Salmonella spp., while four (7%) of the 54 examined by PCR were positive. From the eight positive animals on culture, five were from urban area and three from rural area. On PCR, only one positive animal was from urban area and four were from rural area. Overall, by either test, one of the 54 animals was positive. All samples were collected in free - living animals with no apparent clinical signs of salmonellosis, indicating the potential of capybara as reservoir on this ecosystem.