Differences between Staphylococcus aureus lineages isolated from ovine and caprine mastitis but not between isolates from clinical or subclinical mastitis

Abstract

Staphylococcus aureus is an important mastitis pathogen, causing both clinical mastitis (CM) and subclinical mastitis (SCM) in small ruminants. In general, CM has a low incidence in sheep and goats but can be very severe and costly. In contrast, subclinical mastitis (SCM) is common but is associated with less cost. For both sheep and goats, S. aureus is the main cause of CM and is associated with SCM cases with a high SCC. Recently, specific lineages of S. aureus have been identified that are associated with CM rather than SCM in dairy cows. It is unknown whether specific S. aureus lineages are associated with CM in goats and sheep. The aim of this study was to compare the clonal complex (CC), staphylococcal protein A (spa) type, leukocidin lukM-lukF' presence, and potential to produce LukMF' in vitro between CM and SCM S. aureus mastitis isolates obtained from sheep and goats. Differences between isolates from different host species were also compared. Ovine (CM, n = 12; SCM, n = 29) and caprine (CM, n = 14; SCM, n = 30) isolates were obtained from 8 sheep flocks and 8 goat herds in the Netherlands. Overall, the isolates belonged to CC133 (85%), CC398 (7%), CC425 (5%), and CC45 (2%). Seventeen spa types were found, including 6 novel types; the predominant types were t2678 (34%), t544 (18%), and t3583 (18%). Although CC133 was dominant among both sheep and goat isolates, spa type CC133/t2678 was associated with ovine isolates, whereas CC133/t544 and CC133/t3583 were found mostly in goats. The presence of lukM-lukF' among the S. aureus isolates was high (87%), especially in CC133 (96%) and CC425 (100%), but the genes were absent in CC45 and CC398. In vitro-cultured lukM-lukF'-positive isolates produced LukM (71 out of 74 positive isolates tested) in the range of 0.4 to 5.0 µg/ mL. Interestingly, the goat-associated lineages CC133/ t544 and CC133/t3583 produced more LukM in vitro than the sheep-associated CC133/t2678. We found no difference in LukMF' production potential between CM and SCM isolates. In sheep as well as in goats, no association was found between genotype and CM or SCM, demonstrating that the same lineages of S. aureus are responsible for both CM and SCM. These results suggest that subclinically infected animals in a herd or flock likely act as the reservoir of S. aureus causing CM. This highlights the importance of early identification and control of SCM and suggests that controlling SCM within a herd is an effective intervention to prevent CM in small ruminants.

Staphylococcus aureus From Goats Are Genetically Heterogeneous and Distinct to Bovine Ones

“…Typing of spa showed a remarkable heterogeneity among S. aureus isolates. The most prevalent spa types were t1773, t5428, and t2678, corresponding to CC130, CC522, and CC133, respectively, as already reported (16,17,30). Comparing RS-PCR genotypes to spa types, frequently Staph.…”

“…Nevertheless, different S. aureus spa types are reported to be associated with the two species. For example, among CC133 S. aureus, spa types t544, t3583, and t7304 were predominantly associated with caprine mastitis, whereas t2678 and t9088 with ovine mastitis (16,18,30). However, these spa types are not exclusively associated with one host species (30).…”

“…Several studies consider S. aureus from goats and sheep to be part of the same population based on CC, since they show pronounced adaptation to small ruminants, but not especially to sheep or goats (17,30). Nevertheless, different S. aureus spa types are reported to be associated with the two species.…”

Activation of a Bovine Mammary Epithelial Cell Line by Ruminant-Associated Staphylococcus aureus is Lineage Dependent

“…A panel of S. aureus isolates (n = 35) obtained from cases of ruminant mastitis in the Netherlands was used. Isolates were randomly selected from an in-house S. aureus collection, previously described by Hoekstra et al [20,21], to represent the bovine-associated CCs 151 (n = 7), 479 (n = 9) and small ruminant-associated CCs 133 (n = 15) and 425 (n = 4). In addition, a set of genetically modified and corresponding wildtype (wt) S. aureus strains ( Table 1) were selected to validate the PS cell system.…”

“…Strains belonging to CC151 induce a lower release of proinflammatory cytokines from bMEC than CC97, CC71 and sequence type (ST) 136 S. aureus [17,18]. Whereas most CCs used in these in vitro studies were bovine-associated, little is known about CCs of S. aureus associated with mastitis in small ruminants, such as CC133, CC130 and CC425 [19,20]. It is known that S. aureus can jump species barriers, and cause disease in a new host species [21].…”