Epidemiological investigation of an outbreak of salmonellosis in Gyeongju, Korea

Prevalence of Salmonella spp. and Escherichia coli in the feces of free-roaming wildlife throughout South Korea

Wildlife can carry pathogenic organisms, including viruses, bacteria, parasites, and fungi, which can spread to humans and cause mild to serious illnesses and even death. Spreading through animal feces, these pathogens significantly contributes to the global burden of human diseases. Therefore, the present study investigated the prevalence of zoonotic bacterial pathogens, such as Salmonella spp., Escherichia coli, and Shiga toxin-producing E. coli (STEC), in animal feces. Between September 2015 and August 2017, 699 wildlife fecal samples were collected from various agricultural production regions and mountainous areas in South Korea. Fecal samples were collected from wild mammals (85.26%, 596/699) and birds (14.73%, 103/699). Salmonella spp. and E. coli were present in 3% (21/699) and 45.63% (319/699) of the samples, respectively. Moreover, virulence genes stx1 and both stx1 and stx2 were detected in 13.30% (93/699) and 0.72% (5/699) of the samples, respectively. The 21 Salmonella spp. were detected in badgers (n = 5), leopard cats (n = 7), wild boars (n = 2), and magpies (n = 7); STEC was detected in roe deer, water deer, mice, and wild boars. Through phylogenetic and gene-network analyses, the Salmonella spp. isolates (n = 21 laboratory isolates, at least one isolate from each Salmonella-positive animal fecal sample, and n = 6 widely prevalent reference Salmonella serovars) were grouped into two major lineages: S. enterica subsp. enterica and S. enterica subsp. diarizonae. Similarly, 93 E. coli isolates belonged to stx1, including three major lineages (groups 1-3), and stx1 and stx2 detected groups. To the best of our knowledge, this is the first report of a wild leopard cat serving as a reservoir for Salmonella spp. in South Korea. The research findings can help manage the potential risk of wildlife contamination and improve precautionary measures to protect public health.

Salmonella in eggs: From shopping to consumption-A review providing an evidence-based analysis of risk factors

Nontyphoidal salmonellae are among the most prevalent foodborne pathogens causing gastrointestinal infections worldwide. A high number of cases and outbreaks of salmonellosis are associated with the consumption of eggs and egg products, and several of these occur at the household level. The aim of the current study is to critically evaluate the current status of knowledge on Salmonella in eggs from a consumer's perspective, analyzing the hazard occurrence and the good practices that should be applied to reduce salmonellosis risk. Following a HACCP (Hazard Analysis and Critical Control Point) based approach, some steps along the food journey were identified as Critical Consumer Handling (CCH)-steps in which consumers, through their behavior or choice, can significantly reduce the level of Salmonella in eggs and egg products. From shopping/collecting to consumption, each of these steps is discussed in this review to provide an evidence-based overview of risk factors of human salmonellosis related to egg consumption. The main message to consumers is to choose Salmonella-free eggs (those that some official entity or producer guarantees that does not contain Salmonella), when available, especially for dishes that are not fully heat treated. Second, as guaranteed Salmonella-free eggs are only available in a few countries, refrigerated storage from the point of collection and proper cooking will significantly reduce the risk of salmonellosis. This will require a revision of the actual recommendations/regulations, as not all ensure that eggs are maintained at temperatures that prevent growth of Salmonella from collection until the time of purchasing.

Nationwide surveillance on serotype distribution and antimicrobial resistance profiles of non-typhoidal Salmonella serovars isolated from food-producing animals in South Korea

Food-producing animals are considered a leading source of human Salmonella infections in Korea. However, there is a lack of comprehensive and up-to-date data regarding the diversity and resistance profiles of Salmonella serotypes in these animals. Therefore, this study aimed to determine the distribution and antimicrobial resistance profiles of Salmonella serotypes isolated from cattle, pigs, and chickens in Korea between 2010 and 2018. A total of 3018 Salmonella isolates were obtained from 16 laboratories/centers participating in the Korean Veterinary Antimicrobial Resistance Monitoring System. Salmonella serotypes were identified from the following isolates: 179 cattle (17 serotypes), 959 pig (45 serotypes), and 1880 chicken (64 serotypes). The most frequent serotypes in cattle (Typhimurium, Salmonella 4,[5],12:i:-, and Schwarzengrund), pigs (Typhimurium, Rissen, and S. 4,[5],12:i:-), and chickens (Enteritidis, Albany, Virchow, and Montevideo) accounted for more than 50% of the total serotypes in the respective animal species. To the best of our knowledge, Salmonella 4,[5],12:i:- has not been identified in cattle in Korea to date. More than 80% of the isolates demonstrated resistance to at least one antimicrobial agent. Multidrug-resistance was found in almost half of the serotypes; the highest proportion in cattle (59.2%), followed by pigs (53.4%), and chickens (45.7%). Significant proportions of the serotypes were resistant to ampicillin, streptomycin, and tetracycline. Ceftiofur and ciprofloxacin resistance rates were the highest in Salmonella isolated from chickens (17.1% and 4.1%, respectively) and cattle (10.1% and 3.9%, respectively) compared to that in pigs. Among the frequent serotypes, Albany demonstrated the highest resistance rate (>90%) to five different antimicrobials. Alarmingly, some Salmonella serotypes that are frequently associated with human infections demonstrated a trend of increasing resistance to critically important antibiotics, including 3rd generation cephalosporins and quinolones. Collectively, the presence of antibiotic-resistant Salmonella in food-producing animals poses a potential risk to public health.

Salmonella food-poisoning outbreak linked to the National School Nutrition Programme, North West province, South Africa

Background

Salmonella enterica, with more than 2500 diverse typhoidal and non-typhoidal serotypes (NTS), are foodborne bacterial pathogens of global public health concern. NTS are the most commonly reported causes of foodborne acute gastroenteritis (AGE). Contaminated food products (meat, poultry, eggs and dairy) have been reported to be a source of more than 95% NTS infections. An outbreak of food poisoning occurred among schoolchildren exposed to food provided by the government-sponsored National School Nutrition Programme (NSNP) at a local public primary day school in North West province, South Africa. An epidemiological, environmental and microbiological investigation was conducted to establish the existence and extent of the outbreak, identify the source(s) and causative agent(s) and institute appropriate control and preventive measures.

Methods

An epidemiological investigation was conducted, including a review of the clinical records of the persons exposed, laboratory testing of the pathological specimens collected, environmental testing of the food samples and food preparation areas.

Results

A total of 164 children developed clinical symptoms of AGE following ingestion of processed maize meal, beans and vegetables. Salmonella enterica serovar Heidelberg (S. Heidelberg) was the causative agent for this AGE outbreak in 92.0% of the cases. The median duration of illness was 2 days with a case fatality rate (CFR) of 0.6%. The main food product that was contaminated was samp (processed maize meal) that had been poorly stored and prepared (53.4%).

Conclusion

A timeously-initiated epidemiological, environmental and microbiological an investigation led to the conclusion that the etiologic agent of this outbreak was S. Heidelberg, and the most probable food vehicle of transmission was cooked samp served to learners within the NSNP.

Molecular characterization of antimicrobial resistant non-typhoidal Salmonella from poultry industries in Korea

Background

Antimicrobial resistant Salmonella strains are a direct threat to human health when this resistance interferes with treatment and an indirect threat when resistance can be transferred to other human pathogens. The objective of the present study was to characterize antimicrobial resistant non-typhoidal Salmonella (NTS) isolates recovered from poultry industries, including a description of genetic diversity and virulence profiles.

Results

In total of 93 Salmonella isolates shown antimicrobial resistance to one or more drugs, all isolates exhibited common resistance to streptomycin, nalidixic acid and cephalothin but no ciprofloxacin resistance. Among 26 virulence gene profiling, 12 virulence genes, invA, orgA, prgH, sopB, tolC, sipB, gatC, msgA, pagC, spiA, sifA, and sitC were found in all antimicrobial-resistant NTS isolates. In comparing the data from ERIC-PCR clusters, virulence profiles and resistance profiles, some Salmonella isolates grouped into the same cluster were found to exhibit similar virulence and resistance patterns.

Conclusions

Virulence profiling combined with ERIC-PCR offered a rapid approach to characterize antimicrobial-resistant NTS.