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Genetic characteristics:  Studies have found that isolates from biovar Pullorum were can be multidrug-resistant. Cui et al. analyzed a total of 114 Pullorum isolates from China and revealed that almost all Pullorum isolates (94.74%, n = 108) showed resistance to at least one class of antimicrobial, with 35.96% of the isolates being classified as multidrug-resistant. Another Chinese study examined 652 Pullorum isolates and found that The ampicillin–tetracycline–nalidixic acid (13.6%) was the most common multidrug-resistant pattern observed was ampicillin–tetracycline–nalidixic acid (13.6%). After 2008, . They also concluded that strains resistant to six different classes of antibiotics began emerging and have remained prevalent after 2008. In 2014, a strain an isolate resistant to seven antibiotics (ampicillin–cefazolin–streptomycin–tetracycline–sulphonamides–nalidixic acid–nitrofurantoin) was isolated. The highest level of antimicrobial resistance was found for nalidixic acid (71.9%), while the lowest resistance found. Sun et al. stated that 71.9% of isolates exhibited resistance to nalidixic acid, while no resistance (0%) was observed for cefotaxime, meropenem, amikacin, gentamicin, fosfomycin, and polymyxin (0%) meropenem, and polymyxin.

Animal reservoir: Biovar Pullorum can be found in almost all species of birds. However, clinical signs have been only observed in chickens, turkeys, guinea fowl, quail, and pheasant. 

Geographical distribution: Biovar Pullorum has been reported worldwide.

Animal outbreaks: There have been multiple outbreaks in chickens associated with biovar Pullorum. Examples are shown below:

¹ The flock size is 12,000, and 1,920 birds died.

² The flock size is 1,500, and 1,000 birds died.

Border rejections: There have been no recent border rejections linked to this biovar.

Recalls: There have been no recent recalls linked to this biovar.

Relevant links: 

1. https://pmc.ncbi.nlm.nih.gov/articles/PMC10812584/#:~:text=Salmonella%20enterica%20subsp.,disease%20(PD)%2C%20respectively
2. https://www.woah.org/en/disease/pullorum-disease/#:~:text=Pullorum%20disease%20of%20chickens%20is,septicaemic%20disease%20of%20young%20chickens.
3. https://www.merckvetmanual.com/poultry/salmonelloses-in-poultry/pullorum-disease-in-poultry#Epidemiology_v3342829
4. https://www.sciencedirect.com/science/article/pii/S0378113513005476
5. https://www.poultryimprovement.org/
6. https://pubmed.ncbi.nlm.nih.gov/34412452/
7. https://bmcmicrobiol.biomedcentral.com/articles/10.1186/s12866-024-03296-3
8. https://pmc.ncbi.nlm.nih.gov/articles/PMC7936142/
9. https://www.sciencedirect.com/science/article/pii/S0032579120309457
10. https://www.sciencedirect.com/science/article/pii/B9780444525123001832
11. https://www.nature.com/articles/s41597-022-01605-x
12. https://pmc.ncbi.nlm.nih.gov/articles/PMC7823777/#:~:text=An%20outbreak%20of%20pullorum%20disease,quail%20farm%20in%20western%20France.
13. https://www.jstor.org/stable/1592212?seq=3