Screening for community-acquired strains of methicillinresistant Staphylococcus aureus susceptible to extracts of Centaurea nigrescens

Abstract

The rates of infection by community-acquired multi-drug resistant Staphylococcus aureus have risen dramatically over fifteen years in the United States. Community-acquired multi-drug resistant Staphylococcus aureus is responsible for rapidly progressive diseases, including necrotizing pneumonia, severe sepsis, and necrotizing fasciitis. Consequently, novel antibacterial strategies are needed to combat the rising antibiotic resistance seen in community-acquired multi-drug resistant strains. We have screened the Nebraska Transposon Mutant Library for MRSA strains that are either susceptible or resistant to methanol extracts of Centaurea nigrescens leaves and flowers. 10 strains containing mutations affecting transporter proteins were identified as having either significant resistance or susceptibility to Centaurea extract. Insertions in two different drug efflux transporter families have been identified. The EmrB/QacA drug resistance transporter subfamily is a multi-drug efflux pump responsible for the export of toxic molecules from bacteria and yeast. The ABC transporters are involved in drug import and export. These results confirm the effectiveness of the screen as a means for identifying drug-resistance genes affected by the C. nigrescens methanolic extract and suggest a role for drug efflux proteins in the resistance of S. aureus community-acquired multi-drug resistant Staphylococcus aureus to antibacterial plant metabolites.