Role of PatAB Transporter in Efflux of Levofloxacin in Streptococcus pneumoniae

Abstract

PatAB is an ABC bacterial transporter that facilitates the export of antibiotics and dyes. The overexpression of patAB genes conferring efflux-mediated fluoroquinolone resistance has been observed in several laboratory strains and clinical isolates of Streptococcus pneumoniae. Using transformation and whole-genome sequencing, we characterized the fluoroquinolone-resistance mechanism of one S. pneumoniae clinical isolate without mutations in the DNA topoisomerase genes. We identified the PatAB fluoroquinolone efflux-pump as the mechanism conferring a low-level resistance to ciprofloxacin (8 µg/mL) and levofloxacin (4 µg/mL). Genetic transformation experiments with different amplimers revealed that the entire patA plus the 5’-terminus of patB are required for levofloxacin–efflux. By contrast, only the upstream region of the patAB operon, plus the region coding the N-terminus of PatA containing the G39D, T43A, V48A and D100N amino acid changes, are sufficient to confer a ciprofloxacin–efflux phenotype, thus suggesting differences between fluoroquinolones in their binding and/or translocation pathways. In addition, we identified a novel single mutation responsible for the constitutive and ciprofloxacin-inducible upregulation of patAB. This mutation is predicted to destabilize the putative rho-independent transcriptional terminator located upstream of patA, increasing transcription of downstream genes. This is the first report demonstrating the role of the PatAB transporter in levofloxacin–efflux in a pneumoccocal clinical isolate.

StaR Is a Positive Regulator of Topoisomerase I Activity Involved in Supercoiling Maintenance in Streptococcus pneumoniae

“…Although resistance in this bacterium to beta-lactams and macrolides antibiotics, which are directed against cell-wall and protein synthesis, respectively, has spread globally [ 23 ], no worrisome levels of resistance to antibiotics directed to DNA topology maintenance (fluoroquinolones) [ 24 ], which target the type II DNA topoisomerases, have been detected. However, an increase in resistance may occur in tandem with the increased use of fluoroquinolones either due to alterations in their target topoisomerases genes or to the action of active efflux ([ 25 , 26 , 27 , 28 , 29 , 30 ]. Therefore, knowledge of the molecular basis of Sc control in this important pathogen is essential for finding new antibiotic targets and adequate antibiotic therapies.…”

Physiologic and Transcriptomic Effects Triggered by Overexpression of Wild Type and Mutant DNA Topoisomerase I in Streptococcus pneumoniae

“…These enzymes, which cleave both strands of the DNA transiently, are topoisomerase IV (TopoIV) and gyrase. Although no worrying levels of resistance to fluoroquinolones have yet detected, they could increase in tandem with an increase in their use, either due to alterations in their targets [4][5][6] or to the action of active efflux [7,8]. In this situation, finding new drug targets against S. pneumoniae, and other pathogenic bacteria, is an urgent clinical need.…”

C-Terminal Lysine Residue of Pneumococcal Triosephosphate Isomerase Contributes to Its Binding to Host Plasminogen

“…Pneumococcal infections continue to be a global epidemic, posing a significant threat to children and the elderly with high incidence and mortality rates [ 1 , 2 , 3 ]. Streptococcus pneumoniae , the primary causative agent of pneumonia, is a gram-positive diplococcus that inhabits the human nasopharynx and commonly causes community-acquired pneumonia, otitis media, and sinusitis.…”