Urban rats as carriers of invasive Salmonella Typhimurium sequence type 313, Kisangani, Democratic Republic of Congo

Food and Water Safety Risks From Salmonella enterica and Escherichia coli Contamination in Bukavu City, Democratic Republic of the Congo

Introduction Bukavu city is facing sanitation challenges, with many reported cases of epidemics such as cholera, salmonellosis, and other infectious diseases. Food and water sold under poor sanitation conditions are exposed to potential contamination by pathogenic bacteria. Consumers are therefore at risk of contracting bacterial infections, which could increase the burden of infectious diseases. Solid waste and wastewater management is unsatisfactory in Bukavu city. Few scientific investigations have been conducted to assess the influence of environmental conditions on food and water contamination. For these reasons, this study aimed to investigate the quality of food sold in restaurants and on the streets, as well as the types of water and milk produced and consumed, since food safety and environmental sanitation remain major public health challenges in Bukavu city. Objective The broad objective of this study was to assess the safety risks associated with food and water contamination by Salmonella enterica and Escherichia coli in Bukavu city, DR Congo. Methods A field observation was conducted to identify restaurant locations, and a probabilistic model was applied to determine the number of restaurants to be surveyed. A simple random method was then applied to survey 206 food handlers in restaurants across all three municipalities of Bukavu city. A total of 415 food samples from restaurants, 34 milk samples from dairy farms, and 104 water samples from taps, tanks, and wells were collected. Salmonella enterica and Escherichia coli were isolated from these samples, characterized, and identified through cultural methods and biochemical tests. Results The presence of Salmonella enterica was observed in 38.2% of pork, sausage, and ugali samples (n = 34 for each food), 35.5% of bread, 32.4% of beef and potatoes (n = 34 for each food), and 24.4% of beans (n = 41) tested positive for S. enterica. While Escherichia coli was not isolated from beans, beef, potato, sausage, or vegetable samples, the bacterium was most prevalent in fish (11.8%, n = 34). More than half (57.1%, n = 28) of the water samples from wells were contaminated by S. enterica, and 35.7% (n = 28) by E. coli. The high rate of well contamination could be explained by the location of wells near public waste disposal sites, sewage systems, and pathways frequently used by humans and animals. The presence of S. enterica and E. coli was not significantly different in food (p = 0.15) and water (p = 0.58), suggesting that the environmental conditions of Bukavu city are favorable for the growth of both bacterial species in food and water. However, food contamination by S. enterica and E. coli was significantly (p < 0.05) dependent on food handling practices such as "frequency of cooking food" and "heating food before serving customers" in both formal and informal restaurants (street-vended food). Conclusion Hygiene practices in Bukavu restaurants were not sufficient to guarantee safe food for human consumption, particularly during the serving stages. There is a need for public health and environmental decision-makers to develop or update guidelines in line with national and international standards to enhance public health countermeasures in and around wells, restaurants, and street-vended food and to improve water treatment and infrastructure in Bukavu city.

Emergence and Comparative Genome Analysis of Salmonella Ohio Strains from Brown Rats, Poultry, and Swine in Hungary

Rats are particularly important from an epidemiological point of view, because they are regarded as reservoirs for diverse zoonotic pathogens including enteric bacteria. This study is the first to report the emergence of Salmonella serovar Ohio in brown rats (Rattus norvegicus) and food-producing animals in Hungary. We first reveal the genomic diversity of the strains and their phylogenomic relationships in the context of the international collection of S. Ohio genomes. This pathogen was detected in 4.3% (4/92) of rats, captured from multiple sites in Hungary. A whole-genome-based genotype comparison of S. Ohio, Infantis, Enteritidis, and Typhimurium strains showed that 76.4% (117/153) of the virulence and antimicrobial resistance genes were conserved among these serovars, and none of the genes were specific to S. Ohio. All S. Ohio strains lacked virulence and resistance plasmids. The cgMLST phylogenomic comparison highlighted a close genetic relationship between rat and poultry strains of S. Ohio from Hungary. These strains clustered together with the international S. Ohio genomes from aquatic environments. Overall, this study contributes to our understanding of the epidemiology of Salmonella spp. in brown rats and highlights the importance of monitoring to minimize the public health risk of rodent populations. However, further research is needed to understand the route of infection and evolution of this serovar.

Detection of Yersinia enterocolitica, Shigella spp. and Salmonella spp. in Rattus norvegicus captured from Tehran, Iran

Background: The present study aims to determine the presence of Yersinia spp., Yersinia pestis, Yersinia enterocolitica pathogen, Listeria monocytogenes, Salmonella spp., Shigella spp., Francisella tularensis and Borrelia spp. in brown rats of Tehran, Iran. Methods: PCR was used to detect various bacteria in 100 brown rats, Also, ELISA was used to detect antibodies against the F. tularensis and Borrelia spp. Results: A total of 16% and 13% of fecal samples were positive for Yersinia spp. and Y. enterocolitica pathogen. ELISA results were negative for F. tularensis and Borrelia. No specific antibodies (IgG) were against these bacteria. Conclusion: According to the results of our analysis, rats are significant transmitters and carriers of a variety of illnesses that can spread to both people and other animals.

Intestinal carriage of invasive non-typhoidal Salmonella among household members of children with Salmonella bloodstream infection, Kisangani, DR Congo

Introduction

Invasive non-typhoidal Salmonella (iNTS), mainly Salmonella Typhimurium and Salmonella Enteritidis, causes a severe burden in sub-Saharan Africa; however, its reservoir (animal or environmental) is unclear. The present study assessed healthy household members of index patients for intestinal carriage of Salmonella.

Methods

Index patients were admitted to the University Hospital of Kisangani (DR Congo), and Salmonella was grown from blood cultures. Household members were asked to provide three stool samples for culture for Salmonella. Salmonella Typhimurium and S. Enteritidis isolates from index patients, and household members were assessed for genetic relatedness using the multiple-locus variable number of tandem repeat analysis (MLVA), and the multilocus sequence type (ST) was determined by whole genome sequencing.

Results

Between May 2016 and January 2020, 22 households were visited. The index patient serotypes were Typhimurium, Enteritidis, Typhi, and Paratyphi C; II:42:r:-; and I:7:y:- (n = 8, 7, 5, and each 1, respectively). The median (range) delay between the index patient and household sampling was 25 days (2 days to 7.3 months); 203 household members provided at least one stool sample. In all, 15 (7.3%) Salmonella carriers were found in nine of 22 households. For one index patient, the household comprised S. Typhimurium in four household members, including the index patient, sampled 27 days after bloodstream infection; the MLVA types of these five isolates were similar. They belonged to ST313 lineage 2 and were closely related [0-1 allelic distance (AD) among the stool isolates and eight AD with the blood culture isolate]. In another household, the stool culture of the index patient (obtained 67 days after bloodstream infection) grew S. Enteritidis of the same MLVA type; both isolates belonged to the ST11 Central/Eastern African clade and were closely related (three AD).

Discussion

The present study provides evidence of household clustering of S. Typhimurium ST313 and intestinal carriage of iNTS several weeks after bloodstream infection.

Semi-Quantitative Biosecurity Assessment Framework Targeting Prevention of the Introduction and Establishment of Salmonella Dublin in Dairy Cattle Herds

An increasing average herd size and complexity in farm structures call for a higher level of biosecurity. It can reduce the risk of introducing and establishing pathogens with multiple-pathway and indirect spread mechanisms, such as Salmonella Dublin, a pathogen with an increasing occurrence in dairy cattle farms across different countries and continents. Therefore, this study aimed to use existing knowledge to develop a framework with a supporting tool allowing for a time-efficient, yet comprehensive, assessment of biosecurity measures that can help prevent the introduction and establishment of S. Dublin in dairy herds. Based on the literature review, a seven-step biosecurity assessment framework was developed and evaluated in collaboration with biosecurity experts. The resulting framework includes a weighted semi-quantitative assessment method with a scoring guide in an electronic supporting tool for 12 biosecurity sections assessed through on-farm observations and farmer interviews. The framework and tool provide a novel approach to comprehensively assess the overall (mainly external) on-farm biosecurity level by a trained biosecurity assessor. They can be used for systematic data collection in epidemiological studies on risk factors for the introduction and establishment of S. Dublin in dairy farms. Preliminary interrater reliability testing indicated moderate reliability between assessors with varying biosecurity skills.

What is the Source of Infections Causing Invasive Nontyphoidal Salmonella Disease?

Invasive nontyphoidal Salmonella (iNTS) disease is a clinical condition distinct from Salmonella gastroenteritis. With an overall case-fatality rate of 14.5%, iNTS remains a major cause of morbidity and mortality, particularly in sub-Saharan Africa. However, the sources of infections that lead to cases of iNTS remain unclear. Broadly, there are 2 hypotheses as to the source of infections: (i) transmission from a zoonotic reservoir, similar to other nontyphoidal salmonelloses; or (ii) person-to-person transmission. Here we review several recent studies that have asked, "What is the source of infections causing invasive nontyphoidal Salmonella disease?" Two studies reported isolates in the stool of household members of iNTS cases that were very closely related (<3 single-nucleotide polymorphisms) to the iNTS case isolates; this is consistent with the hypothesis of person-to-person transmission, but infection from a common source (eg, a foodstuff) cannot be excluded. On the other hand, thorough investigations of the domestic environment of iNTS cases and the food pathway found only a single iNTS-associated Salmonella Enteritidis isolate. Therefore, we recommend that future studies test the hypothesis that iNTS is transmitted between people within the domestic environment. Further studies of food and water pathways are also warranted.