Salmonella Infantis

Background: Salmonella enterica subsp. enterica serovar Infantis (antigenic formula 6,7,14:r:1,5) is a serovar of the O:7 (C₁) serogroup. 

In the U.S. and Europe, it ranks among the top ten serovars. S. Infantis has been reported in North America (U.S. and Canada), South America (Argentina, Brazil), Oceania (Australia and New Zealand), Europe (The Netherlands, Finland, Hungary, and Russia), and Asia (Japan).

NCBI PD link for serovar Infantis: https://www.ncbi.nlm.nih.gov/pathogens/isolates/#(taxgroup_name:%22Salmonella%20enterica%22)%20AND%20computed_types:(%22serotype=Infantis%22)

Genetic characteristics: In European countries, a multidrug-resistant (MDR) strain of serovar Infantis was disseminated; this strain emerged from broilers in Hungary (Hungarian clone of serovar Infantis). Resistant pattern of this Hungarian clone included resistance to: nalidixic acid, streptomycin, sulphonamide, and tetracycline. In Italy, an MDR strain of serovar Infantis that showed resistance to ampicillin, chloramphenicol, streptomycin, sulphonamide, tetracycline, kanamycin and trimethoprim/sulfamethoxazole emerged in 2005-06.

The CDC has identified REPJFX01 as a persistent, MDR strain of Salmonella Infantis (hereafter referred to as REP Strain) that has led to illnesses and outbreaks both in the US and worldwide. This strain was first documented in PulseNet in 2012. It has spread to individuals in the United States through contaminated chicken and has also been linked to exposures during international travel. The REP strain show resistance to multiple antimicrobials, including key first-line and alternative treatments such as ampicillin, ceftriaxone, ciprofloxacin, and trimethoprim-sulfamethoxazole. Meanwhile, this strain exhibits relatively high genetic diversity, with isolates differing by up to 82 alleles from one another, as determined by cgMLST (core genome multilocus sequence typing). Chen et al. revealed that Infantis-A-1-3, a chicken-associated clade estimated to have emerged in 1933, includes a clonal sub-clade which emerged in 1990 and represents 32% of the isolates, with an increase in the proportion of isolates collected from chicken or chicken-related sources. 

Animal reservoir: The main animal reservoir of serovar Infantis is poultry; however, at least one of Infantis clade is associated with swine. 

Geographical distribution: Serovar Infantis is distributed globally and is a common serovar in a number of countries. 

Outbreaks: Numerous outbreaks linked to poultry have been reported mainly in the US and Canada. Here are some examples.

¹ Multiple serovars, including Salmonella Altona, Cerro, Enteritidis, Indiana, Infantis, Johannesburg, Mbandaka, and Typhimurium, were linked to this outbreak. The case number represents the total number of cases associated with the outbreak and does not specifically indicate the number of people infected by Salmonella Infantis.

² This outbreak involved both Salmonella Newport (3 cases) and Infantis (1 case).

³ Salmonella Infantis, Lille, Newport, and Mbandaka were reported from 30 states.

⁴ Salmonella Infantis, Newport, and Lille were reported from 27 states.

Border rejections: Multiple border rejections linked to serovar Infantis have been reported. Majority of them are associated with poultry. Here are some examples.

¹ Salmonella Enteritidis and Infantis were both found. 

² Salmonella Infantis and Panama were both found. 

Recalls: Multiple recalls linked to serovar Infantis have been reported. Majority of them are associated with poultry. Here are some examples.

Relevant links:

1. https://pubmed.ncbi.nlm.nih.gov/22564450/
2. https://pubmed.ncbi.nlm.nih.gov/21821397/
3. https://www.cdc.gov/salmonella/php/data-research/repjfx01.html
4. https://journals.asm.org/doi/10.1128/mbio.01913-24
5. https://www.sciencedirect.com/science/article/pii/S0168160523002131
6. https://www.cdc.gov/salmonella/outbreaks/backyardpoultry-05-24/investigation.html
7. https://archive.cdc.gov/#/details?url=https://www.cdc.gov/salmonella/infantis-10-18/index.html
8. http://medbox.iiab.me/modules/en-cdc/www.cdc.gov/salmonella/newport-09-17/index.html
9. https://pmc.ncbi.nlm.nih.gov/articles/PMC9150579/
10. https://pmc.ncbi.nlm.nih.gov/articles/PMC5779341/
11. https://archive.cdc.gov/www_cdc_gov/salmonella/dog-food-05-12/index.html
12. https://www.cdc.gov/mmwr/preview/mmwrhtml/mm6211a5.htm#:~:text=Initial%20investigations%20indicated%20many%20of%20the%20ill,live%20poultry%20(e.g.%2C%20chicks%20and%20ducklings)%20from
13. https://www.accessdata.fda.gov/cms_ia/importalert_218.html
14. https://webgate.ec.europa.eu/rasff-window/screen/notification/731338
15. https://webgate.ec.europa.eu/rasff-window/screen/notification/641450
16. https://webgate.ec.europa.eu/rasff-window/screen/notification/446128
17. https://webgate.ec.europa.eu/rasff-window/screen/notification/429768
18. https://webgate.ec.europa.eu/rasff-window/screen/notification/646586
19. https://www.foodsafetynews.com/2023/10/czech-officials-find-salmonella-in-chicken-from-brazil-11-tons-recalled/
20. https://www.fsis.usda.gov/recalls-alerts/fratelli-beretta-usa-inc.-recalls-ready-eat-uncured-antipasto-meat-products-due
21. https://webgate.ec.europa.eu/rasff-window/screen/notification/483014