Eravacycline susceptibility was impacted by genetic mutation of 30S ribosome subunits, and branched-chain amino acid transport system II carrier protein, Na/Pi cotransporter family protein in Staphylococcus aureus

Abstract

Background: Our previous research indicated the excellent in vitro antibacterial activity of Eravacycline (Erava) and its heteroresistance frequency against clinical Staphylococcus aureus isolates. In this study, we further aimed to investigate the mechanisms of Erava resistance and heteroresistance in S. aureus. Eight parental S. aureus isolates were induced under Erava pressure in vitro and the Erava-resistant isolates were selected and identified. Then, the genetic mutations of 30S ribosomal subunits were analyzed by PCR and sequence alignment. RT-qPCR analysis were performed to compare the relative expression of eight candidate genes impacting the susceptibility of tetracycline (Tet) between the resistant or heteroresistant and parental isolates. Furthermore, the in vitro overexpression vectors of three selected candidate genes were constructed to test their impact on the heteroresistance and resistance of Erava in S. aureus. Results: The MICs elevation in Erava-induced resistant S. aureus isolates were identified and the increasing MICs values of another two Tet class antibiotics, including both omadacycline (Omada) and tigecycline (Tige) were also tested. Genetic mutations in 30S ribosomal protein S10 were found frequently in Erava-derived resistant isolates. RT-qPCR analysis and the in vitro overexpression experiments indicated that USA300HOU_RS00550 (an Na/Pi cotransporter family protein) and USA300HOU_RS01625 (a branched-chain amino acid transport system II carrier protein) contributed to Erava heteroresistance in S. aureus.

In vitro antimicrobial activity and resistance mechanisms of the new generation tetracycline agents, eravacycline, omadacycline, and tigecycline against clinical Staphylococcus aureus isolates

“…K57M was found in both tetracyclines-resistant and-susceptible strains, suggesting that it was not associated with tetracyclines resistance (Fang et al, 2020). Consistent with the findings of Wang et al (Wang et al, 2020), no mutations were detected in the 30S ribosome protein S3, illustrating that S3 was not the predominant factor contributing to tetracyclines resistance in S. aureus.…”

“…Consistent with the findings of Wang et al . ( Wang et al, 2020 ), no mutations were detected in the 30S ribosome protein S3, illustrating that S3 was not the predominant factor contributing to tetracyclines resistance in S. aureus .…”

“…The analysis of 41 tetracyclines-resistant isolates showed that the accumulation of several resistance mechanisms resulted in tetracyclines resistance. Accumulating evidence showed that amino acid substitutions at S10 might be associated with reduced tetracyclines susceptibility ( Beabout et al, 2015 ; Bai et al, 2019 ; Wang et al, 2020 ). We also detected different mutation sites (such as M1L and Y58D) in S10 in the tetracyclines-resistant isolates.…”

“…Mutations or overexpression of the MepRAB efflux pump contributes to the decreased susceptibility to tigecycline ( McAleese et al, 2005 ; Fang et al, 2020 ). Recent studies have revealed that a branched-chain amino acid transport system II carrier protein affects eravacycline and omadacycline susceptibility in S. aureus ( Bai et al, 2019 ; Wang et al, 2020 ). Moreover, a recent study revealed a novel tet (L) efflux pump that confers resistance to eravacycline and tigecycline resistance in Staphylococcus ( Wang et al, 2021 ).…”

Amidochelocardin Overcomes Resistance Mechanisms Exerted on Tetracyclines and Natural Chelocardin

“…The semisynthetic minocycline derivative tigecycline is the first FDA-approved member of the family of glycylcyclines [59], which was initially developed to overcome resistance against classical tetracyclines [60,61]. However, cases of tigecycline-resistant bacteria have been reported for several years, which are augmented by recent studies showing that ribosome mutations and the spread of tetracycline-inactivating enzymes affect the efficacy of further third generation tetracyclines including omadacycline and eravacycline [23,62,63]. Remarkably, an important resistance mechanism for tigecycline relies on mutations of ramR and, consequently, RamA-mediated upregulation of the AcrAB-TolC efflux pump [38,64,65].…”