S. Newport¶

At a Glance


Antigenic Formula	`6,8,20:e,h:1,2`
Serogroup	O:8 (C2-C3)
NCBI Pathogen Detection	View isolates

Background Information¶

Salmonella enterica subsp. enterica serovar Newport (antigenic formula 6,8,20:e,h:1,2) is a serovar of the O:8 (C₂-C₃) serogroup. According to the National Veterinary Services Laboratories (NVSL), serovar Newport became one of the top 10 most frequently identified Salmonella serotypes from US cattle from July 1998 through June 1999. Ranked as one of the top three Salmonella serotypes causing US foodborne outbreaks, serovar Newport has seen a substantial increase in human clinical cases since 1995, with an estimated 100,000 annual infections. In recent years, multidrug resistant Salmonella Newport has emerged as an epidemic, rapidly spreading through animal and human populations in US. In 2019, serovar Newport ranked as the fifth most prevalent Salmonella serotype in the EU/EEA, representing 1.1% of reported human salmonellosis cases.

Genetic Characteristics¶

Serovar Newport has been found to be polyphyletic with four lineages identified. Similarly, Sangal et al. analyzed 384 serovar Newport isolates from various sources and revealed that these serovar Newport isolates grouped into three distinct lineages—Newport-I, Newport-II, and Newport-III—each comprising multiple sequence types (STs). Newport-I included relatively few STs, suggesting a more recent emergence, and was more commonly found in humans in Europe than in North America. In contrast, Newport-II was mainly linked to animal sources. Notably, two STs within Newport-II contained all multidrug-resistant AmpC (MDR-AmpC) isolates, indicating a recent global expansion following acquisition of the bla_CMY-2 gene. Most Newport-III isolates were from humans in North America and were generally susceptible to antibiotics. Overall, serovar Newport showed an intermediate population structure compared to other serovars, ranging from a single lineage in Salmonella Enteritidis and Typhimurium to four separate lineages in Salmonella Paratyphi B. They found that both mutation and homologous recombination contributed to the genetic diversity within these lineages, though their relative impact varied by lineage. Cao et al. found that Asian strains differed genetically from those found in the Americas. To distinguish between different lineages of serovar Newport, they focused on regions near the mutS gene, including segments between the invH and mutS genes at the 3′ end of SPI-1, the ste fimbrial operon, and CRISPR-associated (cas) proteins. Outgroup genomes showed high similarity to either serovar Newport Lineage II or III at these loci. Their analysis revealed that lineages II and III have distinct evolutionary backgrounds in this region, with evidence of genetic exchange and homologous recombination near mutS. These results indicate that serovar Newport Lineages II and III diverged early in the serotype’s evolution and have since followed largely separate evolutionary paths.

Commichaux et al. studied serovar Newport strains associated with 2020 onion outbreak and found that the clinical clade harbored at least 20 plasmid types (e.g., IncFII(S) and IncI1-I(Gamma)), exceeding previously documented diversity for Salmonella Newport. Notably, 14 plasmids from 13 clinical isolates and 17 from 8 farm isolates exhibited >95% sequence similarity, suggesting possible horizontal transfer among these strains. In 2015, CDC detected MDR Salmonella Newport strain related to multiple illnesses and outbreaks, which has since been designated as a persistent strain (REPJJP01) under ongoing surveillance. Most REPJJP01 isolates are resistant to sulfisoxazole, tetracycline, trimethoprim-sulfamethoxazole, azithromycin, chloramphenicol, ciprofloxacin, streptomycin, and ampicillin but susceptible to ceftriaxone. Zhao et al. also found the bla_CMY gene was identify in every Newport MDR-AmpC isolate analyzed. Additionally, this plasmid-borne gene could be transferred through conjugation to an Escherichia coli strain, and the resulting transconjugant exhibited the same MDR-AmpC resistance pattern. Among the isolates, 35 (40%) carried class 1 integrons. Sequencing revealed that these integrons harbored either aadA (conferring streptomycin resistance) or both aadA and dhfr (providing resistance to trimethoprim-sulfamethoxazole). Notably, one integron from a swine-derived isolate included sat-1, which confers resistance to streptothricin—an antibiotic never approved for use in the US.

Animal Reservoir¶

Cattle is the main reservoir for serovar Newport. This serovar was also isolated from other animals, such as pigs, poultry, horses, dogs, and pigeons.

Geographical Distribution¶

Serovar Newport has been reported worldwide but is primarily found in North and Latin America and Europe.

Human/Animal Outbreaks¶

Multiple human outbreaks linked to serovar Newport have been reported with the majority occurring in the US. Below are examples.

Year	Location	Associated source	Number of cases
2022	US: multistate	Beef (suspected)¹	22
2021	US: multistate	Infant formula²	4
2021	US: multistate	Beef (suspected)³	75
2020	US: multistate & Canada	Red onions⁴	1,642
2020	France	Raw or rare horse meat	20
2019	US: multistate	Frozen, ground tuna	15
2019	US: multistate	Pig ear treats for dogs⁵	154
2019	Sweden	Frozen crayfish from China	33
2018-2019	US: multistate	Ground beef	403
2018	US: KS	Tomatoes	10 (confirmed) and 55 (probable)
2018	US: multistate	Frozen shredded coconut⁶	27
2018	France & Scotland	Raw goats' milk cheese⁷	153
2017	US: multistate	Maradol papayas⁸	4
2016-2017	US: multistate	Ground beef	106
2014	US: multistate	Cucumber	275
2012	US: multistate	Cantaloupe⁹	261
2006	US: NY	Watermelon	20
2005-2006	US: multistate	Raw tomatoes¹⁰	459
2004	US	Lettuce	368
2002	US: multistate	Tomatoes	510
2002	US: multistate	Raw or undercooked ground beef	47
1999	US	Mango	78
1995-1996	US, Canada, other international	Alfalfa sprouts	202

¹ A REP strain (REPJJP01) was identified as the outbreak strain.

² A total of four cases were reported [Cronobacter sakazakii (3) and Salmonella Newport (1)].

³ A REP strain (REPJJP01) was identified as the outbreak strain.

⁴ US reported 1,127 cases, while Canada reported 515 cases.

⁵ Salmonella I 4,[5],12:i:-, Cerro, Derby, Infantis, London, Newport, and Rissen were involved in this outbreak. The case number (i.e., 154) is not specific to Salmonella Newport infections.

⁶ The infections included Salmonella I 4,[5],12:b:- (26 cases) and Salmonella Newport (1 case).

⁷ France reported 147 cases, while Scotland reported 6 cases.

⁸ The infections included Salmonella Newport (3 cases) and Salmonella Infantis (1 case).

⁹ The infections included Salmonella Typhimurium (228 cases) and Salmonella Newport (33 cases).

¹⁰ The infections included Salmonella Newport (197 cases), Typhimurium (190 cases), and Braenderup (72 cases).

Border Rejections¶

Multiple border rejections linked to this serovar have been reported and they are mainly associated with poultry or poultry products. Below are some examples:

Year	Exporting country	Importing country	Associated source	Product category
2025	Poland	Italy	Frozen duck¹	Poultry meat and poultry meat products
2025	Poland	Italy	Chicken and turkey kebab	Poultry meat and poultry meat products
2021	Brazil	Germany	Black pepper²	Herbs and spices
2020	Poland	Italy	Frozen marinated chicken inner fillets	Poultry meat and poultry meat products
2020	India	Germany	Dog chews (dried tripes)³	Feed materials

¹ Salmonella Enteritidis and Newport were found.

² Salmonella Javiana, Newport, Poona and Abaetetuba were found.

³ Salmonella Typhimurium and Newport were found.

Recalls¶

Multiple recalls linked to this serovar have been reported and they are associated with a variety of food commodities. Below are some examples:

Year	Location	Recalled food	Type
2023	Poland, Italy	Pekin duck fillet from Poland¹	Poultry meat and poultry meat products
2023	Germany	Spice mixtures (onion powder)	Herbs and spices
2022	Poland	Dried chicken feet	Pet food
2020	US: multistate	Onions²	Fruits and vegetables
2018	US: multistate	Raw beef products³	Meat and meat products (other than poultry)
2012	US: multistate	Cantaloupe⁴	Fruits and vegetables

¹ Salmonella Enteritidis and Newport were found.

² This recall was caused by a multistate outbreak described above. Thomson International, Inc. and other companies voluntarily issued recalls of their red, yellow, white, and sweet yellow onions.

³ This recall was caused by a multistate outbreak described above. JBS Tolleson, Inc., a Tolleson, Ariz. establishment, issued a recall of approximately 12,093,271 pounds of non-intact raw beef products.

⁴ This recall was caused by a multistate outbreak involving Salmonella Typhimurium and Newport as described above. Chamberlain Farms Produce, Inc. of Owensville, Indiana voluntarily issued a recall of cantaloupe grown on its farm.