Identification of ABC transporters from Sarcoptes scabiei and their potential association with emerging ivermectin resistance

Ivermectin is currently used in the treatment of hyper-infested (crusted) scabies and has been identified as a potentially effective acaricide for mass treatment programs in scabies endemic communities. We have recently observed clinical and in vitro ivermectin resistance in two crusted scabies patients, raising serious concerns for the sustainability of such programs. It has been proposed that ivermectin resistance may be mediated by ABC transporters such as P-glycoprotein. We have now identified and further sequenced ABC transporters of relevance from an EST database of Sarcoptes scabiei var. hominis. Analysis confirmed that most of the known ABC-subfamilies were represented in the S. scabiei database including several members of the multi-drug resistance protein subfamily (ABC-C). Although P-glycoprotein (ABC-B) sequences were not found in the EST database, partial P-glycoproteins were subsequently obtained from the library using a degenerate PCR strategy. This work forms an important foundation for further studies to elucidate the potential role of ABC-transporters in ivermectin resistance of S. scabiei