Table 1.

Knowledge gaps in understanding the role of NAS on udder health.

Section	Knowledge gaps
Species distribution and diversity	• Interactions between individual NAS (e.g., synergistic) in the udder • Interactions between individual NAS and the udder • Acquired genes giving the ability to colonize and persist in udders and on teat apices
Dominant NAS species	• Factors that underlie success of certain NAS as colonizers and the most prevalent species such as S. chromogenes
Impact of NAS on inflammation	• Potential strain differences and factors of NAS species that provoke inflammation
Virulence and host association	• Association between virulence genes and disease severity • The role of capsular genes in NAS virulence • Correlation between capsular genotype/phenotype and biofilm formation • Biofilm production and its association with pathogenicity of S. chromogenes and other NAS species • Elucidating the role of specific virulence factors (e.g., β-hemolysins) for S. chromogenes and other NAS species • Tracking evolutionary history of NAS species in the context of virulence genes
Antimicrobial resistance	• Clarifying if NAS species represent a reservoir of AMR genes for major mastitis pathogens • Possibility of new resistance mechanisms in NAS species • Characterization of intrinsic AMR mechanisms • Correlation between co-resistance profiles of NAS species and its effect on udder health
Niche adaptation and host association	• Classification of NAS species as commensal microbiota or opportunistic or obligate pathogens
Interactions within the udder microbiome	• Causes of NAS being disruptors of the udder microbiome • Role of bacteriocins produced by NAS species in modulating the udder microbiome • Clarifying if NAS species IMI increase susceptibility to major pathogens or, on the contrary, prevent them from infecting the udder • Characterizing the host genetic component and its relationship to NAS colonization
Understanding how mastitis control measures influence NAS incidence and prevalence	• Further evaluation of the associations among mastitis control measures and incidence and prevalence of mastitis caused by different NAS species