Comparative profiling of agr locus, virulence, and biofilm‑production genes of human and ovine non‑aureus staphylococci

Background: In a collaboration between animal and human health care professionals, we assessed the genetic characteristics
shared by non-aureus staphylococci (NAS) infecting humans and dairy ewes to investigate their relatedness
in a region concentrating half of the total National sheep stock. We examined by PCR 125 ovine and 70 human NAS
for biofilm production, pyrogenic toxins, adhesins, autolysins genes, and accessory gene regulator (agr) locus. The
microtiter plate assay (MPA) was used for the phenotypic screening of biofilm production. Ovine NAS included S. epidermidis,
S. chromogenes, S. haemolyticus, S. simulans, S. caprae, S. warneri, S. saprophyticus, S. intermedius, and S. muscae.
Human NAS included S. haemolyticus, S. epidermidis, S. hominis, S. lugdunensis, S. capitis, S. warneri, S. xylosus, S. pasteuri,
and S. saprophyticus subsp. bovis.
Results: Phenotypically, 41 (32.8%) ovine and 24 (34.3%) human isolates were characterized as biofilm producers.
Of the ovine isolates, 12 were classified as biofilm-producing while the remaining 29 as weak biofilm-producing. All
24 human isolates were considered weak biofilm-producing. Few S. epidermidis isolates harbored the icaA/D genes
coding for the polysaccharide intercellular adhesin (PIA), while the bhp, aap, and embp genes coding biofilm accumulation
proteins were present in both non-producing and biofilm-producing isolates. Fifty-nine sheep NAS (all S. epidermidis,
1 S. chromogenes, and 1 S. haemolyticus) and 27 human NAS (all S. epidermidis and 1 S. warneri) were positive for
the agr locus: agr-3se (57.8%) followed by agr-1se (36.8%) predominated in sheep, while agr-1se (65.4%), followed by
agr-2se (34.6%) predominated in humans.
Concerning virulence genes, 40, 39.2, 47.2%, 52.8, 80 and 43.2% of the sheep isolates carried atlE, aae, sdrF, sdrG, eno
and epbS respectively, against 37.1, 42.8, 32.8, 60, 100 and 100% of human isolates. Enterotoxins and tsst were not
detected.
Conclusions: Considerable variation in biofilm formation ability was observed among NAS isolates from ovine and
human samples. S. epidermidis was the best biofilm producer with the highest prevalence of adhesin-encoding genes.