Multistate outbreak of Salmonella Typhimurium linked to pet hedgehogs, United States, 2018-2019

Zoonotic Gastroenteric Diseases of Exotic Animals

Exotic pet ownership has steadily increased over the last decade, and with increased numbers of these species in close contact with humans, the risk of gastrointestinal zoonoses has also increased. Non-typhoidal serovars of Salmonella enterica are one of the most prevalent and important zoonoses of exotic pets, and reptile and backyard poultry are common asymptomatic carriers of these bacteria. Outbreaks of reptile-associated salmonellosis have occurred yearly in the United States since 2019 but contact with backyard poultry has actually been associated with more Salmonella outbreaks in the United States than any other animal species to date.

Emergence and Characterization of the High-Level Tigecycline Resistance Gene tet(X4) in Salmonella enterica Serovar Rissen from Food in China

The plasmid-mediated tet(X4) gene has exhibited a high-level resistance to tigecycline (TGC), which has raised concerns globally regarding antibiotic resistance. Although the widespread tet(X4) has been found widely in Escherichia coli, it is scarcely found in other Enterobacteriaceae. This study aimed to characterize a ST469 Salmonella enterica serovar Rissen (S. Rissen) isolate harboring tet(X4) from pork, which was identified and characterized via antimicrobial susceptibility testing, conjugation assays, plasmid curing testing, whole-genome sequencing, and bioinformatic analysis. Ten ST469 S. Rissen isolates of 223 Salmonella spp. isolates were isolated from food samples in China during 2021-2023. One of 10 S. Rissen isolates, SM2301, carrying tet(X4) conferred high-level resistance to TGC (minimum inhibitory concentration > 8 µg/mL). The tet(X4) could be conjugated into different recipients, including E. coli, S. enteritidis, and K. pneumoniae isolates. Plasmid curing confirmed that tet(X4) was plasmid-mediated. Genetic analysis revealed that the tet(X4) in the SM2301 isolate was located in the IncFIA(HI1)-IncHI1A-IncHI1B(R27) hybrid plasmid, and the structure of tet(X4) was abh-tet(X4)-ISCR2. To the best of our knowledge, this is the first report of a tet(X4)-positive food-derived S. Rissen isolate. The extending bacterial species of tet(X4)-bearing plasmids suggested the increasing transmission risk of the mobile TGC resistance gene tet(X4) beyond E. coli. This study highlights the emerging and evolution risk of novel resistance genes across various bacterial species. Therefore, further surveillance is warranted to monitor the prevalence of tet(X4) in Salmonella spp. and other bacterial species.

Foodborne pathogenic bacteria in wild European hedgehogs (Erinaceus europaeus)

BACKGROUND

European hedgehogs (Erinaceus europaeus) are widely distributed across Europe. They may play an important role by spreading zoonotic bacteria in the environment and to humans and animals. The aim of our work was to study the prevalence and characteristics of the most important foodborne bacterial pathogens in wild hedgehogs.

RESULTS

Faecal samples from 148 hospitalised wild hedgehogs originating from the Helsinki region in southern Finland were studied. Foodborne pathogens were detected in 60% of the hedgehogs by PCR. Listeria (26%) and STEC (26%) were the most common foodborne pathogens. Salmonella, Yersinia, and Campylobacter were detected in 18%, 16%, and 7% of hedgehogs, respectively. Salmonella and Yersinia were highly susceptible to the tested antimicrobials. Salmonella Enteritidis and Listeria monocytogenes 2a were the most common types found in hedgehogs. All S. Enteritidis belonged to one sequence type (ST11), forming four clusters of closely related isolates. L. monocytogenes was genetically more diverse than Salmonella, belonging to 11 STs. C. jejuni ST45 and ST677, Y. pseudotuberculosis O:1 of ST9 and ST42, and Y. enterocolitica O:9 of ST139 were also found.

CONCLUSIONS

Our study shows that wild European hedgehogs should be considered an important source of foodborne pathogens, and appropriate hygiene measures after any contact with hedgehogs and strict biosecurity around farms are therefore important.

Antimicrobial resistance in multistate outbreaks of nontyphoidal Salmonella infections linked to animal contact-United States, 2015-2018

Animal contact is an established risk factor for nontyphoidal Salmonella infections and outbreaks. During 2015-2018, the U.S. Centers for Disease Control and Prevention (CDC) and other U.S. public health laboratories began implementing whole-genome sequencing (WGS) of Salmonella isolates. WGS was used to supplement the traditional methods of pulsed-field gel electrophoresis for isolate subtyping, outbreak detection, and antimicrobial susceptibility testing (AST) for the detection of resistance. We characterized the epidemiology and antimicrobial resistance (AMR) of multistate salmonellosis outbreaks linked to animal contact during this time period. An isolate was considered resistant if AST yielded a resistant (or intermediate, for ciprofloxacin) interpretation to any antimicrobial tested by the CDC or if WGS showed a resistance determinant in its genome for one of these agents. We identified 31 outbreaks linked to contact with poultry (n = 23), reptiles (n = 6), dairy calves (n = 1), and guinea pigs (n = 1). Of the 26 outbreaks with resistance data available, we identified antimicrobial resistance in at least one isolate from 20 outbreaks (77%). Of 1,309 isolates with resistance information, 247 (19%) were resistant to ≥1 antimicrobial, and 134 (10%) were multidrug-resistant to antimicrobials from ≥3 antimicrobial classes. The use of resistance data predicted from WGS increased the number of isolates with resistance information available fivefold compared with AST, and 28 of 43 total resistance patterns were identified exclusively by WGS; concordance was high (>99%) for resistance determined by AST and WGS. The use of predicted resistance from WGS enhanced the characterization of the resistance profiles of outbreaks linked to animal contact by providing resistance information for more isolates.

Spatiotemporal Distribution of Salmonella enterica in European Hedgehogs in Northern Italy

Growing attention is being given to the European hedgehog (Erinaceus europaeus) because of its synanthropic behaviour and its potential role in harbouring parasites, viruses, fungi and bacteria and disseminating them to several animals and humans. Salmonella are the most frequently detected zoonotic bacteria that hedgehogs could transmit through contaminating water and food sources with faeces. This study aimed to determine the prevalence and distribution of Salmonella spp. in wild hedgehogs in the Emilia-Romagna region (northern Italy). From 2019 to 2022, 212 European hedgehogs that died naturally were tested for Salmonella spp. through culture isolation. Positive samples were subjected to serological typing. A total of 82 samples tested positive for Salmonella spp., with the overall Bayesian posterior estimated prevalence ranging from 35% (95% CI: 23-47%) to a maximum of 45% (95% CI: 31-59%) during the years considered and with an overall prevalence calculated at 39% (95% CI: 33-45%). Salmonella enterica Enteritidis and Veneziana were the most prevalent detected serovars in 65% and 17% of the positive samples, respectively. Since 2021, S. Typhimurium, S. Typhimurium Monofasica, S. Zaiman, S. Hessarek, S. Muenster, S. Isangi serovars, S. enterica subsp. Diarizonae and S. enterica subsp. Houtenae have been detected. These findings show a high prevalence of Salmonella spp. in tested hedgehogs, suggesting an important role of this animal species in the epidemiology of potentially zoonotic serovars circulating in the Emilia-Romagna region.

Through the Looking Glass: Genome, Phenome, and Interactome of Salmonella enterica

This review revisits previous concepts on biological phenomenon contributing to the success of the Salmonella enterica subspecies I as a pathogen and expands upon them to include progress in epidemiology based on whole genome sequencing (WGS). Discussion goes beyond epidemiological uses of WGS to consider how phenotype, which is the biological character of an organism, can be correlated with its genotype to develop a knowledge of the interactome. Deciphering genome interactions with proteins, the impact of metabolic flux, epigenetic modifications, and other complex biochemical processes will lead to new therapeutics, control measures, environmental remediations, and improved design of vaccines.