Emergence of Salmonella enterica serovar Potsdam as a major serovar in waterfowl hatcheries and chicken eggs

Genomic and virulent characterization of a duck-associated Salmonella serovar Potsdam from China

Salmonella, a common zoonotic pathogen, is a significant concern for public health, particularly when it contaminates animal-borne products. The potential for Salmonella to infect duck embryos and disrupt their normal development not only causes substantial economic losses for the industry but also poses a severe threat to public health. However, there is a lack of understanding about the prevalence of Salmonella in duck embryos and their potential public health implications. Our study aims to fill this gap by providing genomic features of the antimicrobial resistance and virulence potential of Salmonella isolates from dead duck embryos using whole-genome sequencing and in silico toolkits. We also sought to assess the virulent characterization of the major serovar isolates by experimental infection of chicken and duck embryos. Our investigation of 195 duck embryo eggs led to the isolation of 40 (20.51%) Salmonella strains, with Salmonella serovar Potsdam being the most prevalent serovar. Most isolates were resistant to streptomycin (57.3%) and nalidixic acid (50%). Notably, our findings demonstrated that S. Potsdam exhibited a preference for ducks over chickens, suggesting potential host specificity. Additionally, global phylogenomic analysis, incorporating 180 global genomes, revealed a predominant association of S. Potsdam with ducks, supporting an adaptive process specific to the waterfowl. This study determined Salmonella serovars and antimicrobial resistance profiles in dead duck embryos, revealing a rare Salmonella serovar Potsdam with a potential for duck adaption.

The Expanded Role of Roof-Rats (Rattus rattus) in Salmonella spp. Contamination of a Commercial Layer Farm in East Japan

Rodents serve as amplifiers of Salmonella infections in poultry flocks and can serve as a source of Salmonella contamination in the environment even after thorough cleaning and disinfection. This study aims to determine the dynamics of Salmonella occurrence in rodents and its relation to Salmonella contamination in the layer farm environment, including air dusts and eggs. From 2008 to 2017, roof rats (Rattus rattus), environmental swabs, air dusts, and eggs were collected from an intensive commercial layer farm in East Japan and were tested for Salmonella spp. using standard procedures. In roof rat samples, the Salmonella isolation rate was reached at 10% (95% confidence interval [CI] 8.1-21.9) in which Salmonella Corvallis, Salmonella Infantis, Salmonella Potsdam, and Salmonella Mbandaka were the frequent isolates from the cecal portion of the intestines. On the other hand, the prevalence rate of Salmonella in environmental swabs was at 5.1% (95% CI 2.2-7.4) while air dusts were at 0.9% (95% CI 0.2-1.8). It was observed that the prevalence of predominant Salmonella serotypes shifted over time; in roof rats, it was noted that Salmonella Potsdam gradually replaced Salmonella Infantis. In environmental swabs and eggs, Salmonella Corvallis and Salmonella Potsdam increased significantly while Salmonella Infantis became less frequent. In air dusts, Salmonella Corvallis was observed to decrease and Salmonella Potsdam became more common. Based on our findings, the role of roof rats in the epidemiology of Salmonella in layer farms was expanded from being a reservoir and an amplifier host into a shifting vessel of the most predominant serotypes.

Analyses of prevalence and molecular typing of Salmonella in the goose production chain

This study investigated the prevalence of Salmonella and the molecular typing of all isolates in a goose production chain including hatchery, farm, slaughterhouse, and market. A total of 350 Salmonella isolates was detected from 1,030 samples, and 13 serotypes were recovered. The highest Salmonella contamination frequency was observed at the hatchery, which 51.8% (188/363) of samples were Salmonella positive. S. Potsdam and S. Typhimurium were the 2 most common serotypes. S. Potsdam was most frequently found in the hatchery, while S. Typhimurium was widely distributed in the goose production chain. In general, the antibiotic resistance of Salmonella isolates is low, which isolates from the market is comparatively higher than from other production links indicating a possibility of Salmonella cross-contamination in the market. By the multilocus sequence typing (MLST) analysis, 7 different ST types were identified. ST2039 was the most common ST type, which was mostly found from S. Potsdam isolates in hatchery indicating that S. Potsdam might have been long existed in hatchery. The pulsed-field gel electrophoresis (PFGE) analysis of S. Potsdam indicated that S. Potsdam could be transmitted along the production chain. The PFGE analysis of S. Typhimurium showed that PFGE pattern 29 (PF29) was distributed in hatchery, and also in farm and from humans indicating the risk of S. Typhimurium transmitting to humans by the food supply chain. Our study provided the evidence of Salmonella cross-contamination in the slaughterhouse and the retail market of goose production chain, and specific serotypes existed for a long time at a particular production link. The spread of Salmonella along the production chain, might cause harm to humans through cross-contamination. Further studies would be needed to control the Salmonella contamination in hatchery and prevent the transmission of the pathogen during the goose production.

Evaluation of 3-week-old layer chicks intratracheally challenged with Salmonella isolates from serogroup c1 (O:6,7) and Salmonella Enteritidis

With the exception to Salmonella enterica serotype Typhimurium and S. Enteritidis (serogroups B [O:4] and D [O:9], respectively), there have been very few studies conducted on the respiratory tract as route of infection in chickens with salmonellas from serogroup C1 (O:6,7). Therefore, the purpose of this present study was to determine the potential organ invasion by Salmonella enterica serotype Potsdam (SP), S. Mbandaka (SM), and S. Infantis (SI) from serogroup C1 (O:6,7) and compare their characteristics with those of S. Enteritidis (SE) on intratracheally (IT) challenged 3-week-old layer chicks. A total of 360 one-day-old White Leghorn layer chicks were acquired from a commercial hatchery and randomly assigned into four treatment groups (SP, SM, SI, and SE, respectively), consisting of three independent trials. Chicks were grown up to 21 days (3 weeks) and IT-challenged thereafter with 10⁶ CFU of respective salmonella organisms per group (n = 30). Chicks (n = 5) were humanely sacrificed every 24 h for 6 days post-IT infection and organs such as lung, heart, liver, spleen, kidney and caecal content were cultured for salmonella. All treatment groups exhibited colonization of lungs and caecal contents at 1 d (P = 0.475) and 4 d (P = 0.696) post-IT infection, respectively. There was no isolation of SP, SM, and SI in heart, liver, spleen, and kidney. In contrast, SE was obtained from heart, liver, and spleen of IT-infected chicks. The findings of this study contribute to a better understanding of the importance of the respiratory route in salmonella infection in poultry.

Phenotypic and genotypic characterization of locally isolated Salmonella strains used in preparation of Salmonella antigens in Egypt

Aim:

This work was conducted to study the phenotypic and genotypic characterization of locally isolated Salmonella strains (Salmonella Pullorum, Salmonella Enteritidis, and Salmonella Typhimurium) from poultry used in the preparation of Salmonella antigens in Egypt.

Materials and Methods:

The phenotypic characterization of Salmonella strains was done using standard microbiological, biochemical, and serological techniques. Molecular identification was done using different sets of primers on different genes using different polymerase chain reaction (PCR) techniques.

Results:

The phenotypic characterization of Salmonella strains was confirmed. Molecular identification revealed detection of 284 bp fragment of InvA gene in all studied Salmonella strains. Furthermore, multiplex PCR was used for more confirmation of being Salmonella spp., generally at 429 bp as well as genotyping of Salmonella Typhimurium and Salmonella Enteritidis at 559 and 312 bp, respectively, in one reaction.

Conclusion:

The locally isolated field Salmonella strains were confirmed phenotypically and genotypically to be Salmonella Enteritidis, and Salmonella Typhimurium and could be used for the preparation of Salmonella antigens.

An association of genotypes and antimicrobial resistance patterns among Salmonella isolates from pigs and humans in Taiwan

We collected 110 Salmonella enterica isolates from sick pigs and determined their serotypes, genotypes using pulsed-field gel electrophoresis (PFGE), and antimicrobial susceptibility to 12 antimicrobials and compared the data with a collection of 18,280 isolates obtained from humans. The pig isolates fell into 12 common serovars for human salmonellosis in Taiwan; S. Typhimurium, S. Choleraesuis, S. Derby, S. Livingstone, and S. Schwarzengrund were the 5 most common serovars and accounted for a total of 84% of the collection. Of the 110 isolates, 106 (96%) were multidrug resistant (MDR) and 48 (44%) had PFGE patterns found in human isolates. S. Typhimurium, S. Choleraesuis, and S. Schwarzengrund were among the most highly resistant serovars. The majority of the 3 serovars were resistant to 8–11 of the tested antimicrobials. The isolates from pigs and humans sharing a common PFGE pattern displayed identical or very similar resistance patterns and Salmonella strains that caused severe infection in pigs were also capable of causing infections in humans. The results indicate that pigs are one of the major reservoirs to human salmonellosis in Taiwan. Almost all of the pig isolates were MDR, which highlights the necessity of strictly regulating the use of antimicrobials in the agriculture sector in Taiwan.

Molecular techniques for detecting and typing of bacteria, advantages and application to foodborne pathogens isolated from ducks

In recent times, several foodborne pathogens have become important and a threat to public health. Surveillance studies have provided data and a better understanding into the existence and spread of foodborne pathogens. The application of molecular techniques for detecting and typing of foodborne pathogens in surveillance studies provide reliable epidemiological data for tracing the source of human infections. A wide range of molecular techniques (including pulsed field gel electrophoresis, multilocus sequence typing, random amplified polymorphism deoxyribonucleic acid, repetitive extragenic palindromic, deoxyribonucleic acid sequencing, multiplex polymerase chain reaction and many more) have been used for detecting, speciating, typing, classifying and/or characterizing foodborne pathogens of great significance to humans. Farm animals including chickens, cattle, sheep, goats and pigs, and others (such as domestic and wild animals) have been reported to be primary reservoirs for foodborne pathogens. The consumption of contaminated poultry meats or products has been considered to be the leading source of human foodborne infections. Ducks like other farm animals are important source of foodborne pathogens and have been implicated in some human foodborne illnesses and deaths. Nonetheless, few studies have been conducted to explore the potential of ducks in causing foodborne outbreaks, diseases and its consequences. This review highlights some common molecular techniques, their advantages and those that have been applied to pathogens isolated from ducks and their related sources.

Prevalence of Salmonella serotypes in male mule ducks in Belgium

Salmonella species infections of male mule ducks were studied for 32 months in 100 flocks on nine duck farms in Belgium. The prevalence of Salmonella species infections changed significantly over time (P<0.001) with infection rates of 50, 13.4, 6.7, 2.6 and 2.9 per cent, respectively, at the time of arrival on the farm, at three, six and nine weeks of age, and when the ducks left the breeding unit to enter the force-feeding rooms (at 11 or 12 weeks of age). During the study period, 95 strains of Salmonella were isolated, belonging to 11 serotypes. S Indiana (42.1 per cent) and S Regent (36.8 per cent) were the two most common serotypes, whereas S Typhimurium and S Enteritidis were found only once (1.1 per cent). All isolated strains were resistant to at least two antimicrobials, but resistance to more than five antimicrobials was observed in 21.6 per cent of the strains.