12b repeat differing in two bases from repeats selleck inhibitor 20. 41c repeat differing in one base from repeat 17. 31d repeat differing in two bases from repeat 16. 16e repeat differing in one base from repeat 17. 34f repeat differing in two bases from repeats 12 and 20. 05g repeat differing in one base from repeat 29. Any clusters of related spa-types with a higher prevalence of rearrangements affecting spa-typing (delE, delG-insB or insC2) would be likely to be underrepresented,

or even missing, in the majority of studies based on routine spa-typing protocols. To test this hypothesis, we compared the proportion of individuals with and without rearrangements affecting spa-typing in the four groups of spa-types and the singleton that we found had one or more rearrangements affecting spa-typing (5 × 2 exact test, Table 5). In group 1 35% of learn more strains were affected by these rearrangements, a significantly higher proportion compared with the 1-4% in other groups or the singleton t530 (p < 0.0001). Therefore, spa-type t571 and its closely related variants such as t3085 may well be underrepresented in most S. aureus studies based on spa-typing, as they could not be typed with the standard set of primers when common deletions are present. Interestingly, spa-type t571 belongs to clonal lineage

ST398 that contains MRSA and MSSA strains common among livestock. Spa-type t571 is closely related to type t011 and t034, all most commonly associated with pigs [36–40]. These spa-types have been found less commonly in dogs, cats and horses, and occasionally in cattle and poultry click here [41, 42]. Large-scale screening of pigs [36] showed that 60% of them carried t034, 14% t1255 and 1.5% t571. Although ST398-associated spa-types have been rarely found among the general human population, they have been found more commonly in farmers working with pigs [36, 37]. Veterinary personnel and pet owners are also more likely to carry these

animal-related types [43]. Recent studies have also reported the emergence of livestock-associated Rucaparib research buy MRSA clones of S. aureus ST398 causing bacteraemias in humans, supporting animal-independent transmission of such strains between humans [44, 45]. It is unclear why ST398 S. aureus strains commonly found in livestock frequently develop deletions in the IgG-binding part of protein A gene after transmission to humans. One possible explanation is that this might be a part of S. aureus strain adaptation to a different immune background where protein A plays a major role [7, 8, 12]. Another explanation might be that the livestock associated strains have more rearrangements in the spa-gene prior the transmission to humans due to high level of antibiotic exposure in food-animal production [46–48]. Nevertheless, our findings highlight the potential for these strains to have been substantially under-represented in epidemiological studies to date, and for strains formerly not-typeable using standard methods to be a source of bias.