Screening of inhibitors of the activation of the bla and vraSRT systems of Staphylococcus aureus using compounds secreted by Streptomyces strains

FABBRI, C.; RODRÍGEZ, E.J.; ANTINORI, M.A.; GRAMAJO, H.; BERCOVICH, B.A.; LLARRULL, L.I.

Rosario

Jornada; Jornada Científica del Instituto de Biología Molecular y Celular de Rosario; 2019

Instituto de Biología Molecular y Celular de Rosario

Staphylococcus aureus is the leading cause of nosocomial and community-acquired infections. The main mechanism of resistance to β-lactam antibiotics in S. aureus is due to inducible expression of the serin β-lactamase PC1 and of a transpeptidase, PBP2a, with reduced affinity for these antibiotics. These resistance determinants are regulated by the bla operon. The vraSRT system acts as a sentinel that can rapidly sense damage of the peptidoglycan and coordinate a response that leads to resistance to β-lactam and glycopeptide antibiotics. Using a S. aureus reporter strain, which has a shuttle vector that allows expression of GFP under the control of the vraSRT or bla systems, we screened supernatants of cultures of various Streptomyces strains grown in different culture media. Activation of the system by β-lactams and/or glycopeptide antibiotics lead to expression of GFP and hence to an increase in the intensity of the emitted fluorescence. We searched for supernatants that prevented the activation of the systems by β-lactams and/or glycopeptide antibiotics. We identified several Streptomyces extracts that prevented activation of the systems, but that allowed growth of the S. aureus reporter strain. Then, we corroborated that some of these extracts were able to restore the effectiveness of the antibiotics treatment against resistant clinical VISA and hVISA strains.In conclusion, we have identified Streptomyces strains that secrete compounds that reestablish the effectiveness of β-lactams and/or glycopeptide antibiotics against some resistant S. aureus strains. Work is underway to identify the active compounds and to corroborate that they specifically inhibit the vraSRT or bla systems. Acknowledgments:? CONICET for PhD fellowship to MA and for Grant PIP 22920160100039CO (Grant for Research Units 2016).? ANPCyT for PhD fellowship to CF and grant PICT-2015-2521.