Table 3.

Summary of virulence factors and their related genes that were detected in several NAS species, as well as the relationship between these genes and pathogenesis in the context of NAS IMI.

Virulence factors (related genes)	Associations of virulence factors with pathogenesis of NAS	Reference(s)
Methicillin-resistance and biofilm-related genes (mecA, eno)	• Isolates from clinical mastitis cases had a significantly higher presence of methicillin-resistant (mecA) genes (21 out of 43 isolates) • All 43 isolates tested positive for the presence of the biofilm-related gene, eno	(16)
Intracellular adhesin (icaA/B/C)	• In human-associated NAS, it is a genetic determinant for biofilm formation • Presence of icaA was associated with greater biofilm formation in bovine NAS species. Almost half the isolates tested positive for this gene	(7, 79, 80)
Iron-regulated surface determinant (isdA/B/C/I)	• IsdI the most frequently distributed gene among NAS species in a Canadian study • Every NAS isolate contained at least one gene related to iron uptake and metabolism • Staphylococci require iron to replicate and persist in infections	(7)
Hemolysin (hla/b/d)	• Hemolysins lysed erythrocytes of cattle, sheep, and goats • β-hemolysin (hlb) was the most frequent gene in NAS isolates in a Canadian study • In Iran, bovine NAS isolates primarily produced δ-hemolysin (hld)	(7, 81)
Phenol-soluble modulins (PSMβ1/2/3/4)	• Lysis of red and white blood cells, linked to biofilm formation and stimulation of inflammatory responses • β-type PSMs were associated with bovine NAS isolates in a Canadian study	(7)