The Contribution of Efflux Systems to Levofloxacin Resistance in Stenotrophomonas maltophilia Clinical Strains Isolated in Warsaw, Poland

Abstract

Levofloxacin is considered an alternative treatment option of Stenotrophomonas maltophilia infections to trimethoprim/sulfamethoxazole. The fluoroquinolone resistance in S. maltophilia is usually caused by an overproduction of efflux pumps. In this study, the contribution of efflux systems to levofloxacin resistance in S. maltophilia clinical isolates was demonstrated using phenotypic (minimal inhibitory concentrations, MICs, of antibiotics determination ± efflux pump inhibitors, EPIs) and molecular (real-time polymerase-chain-reaction and sequencing) methods. Previously, the occurrence of genes encoding ten efflux pumps was shown in 94 studied isolates. Additionally, 44/94 isolates demonstrated reduction in susceptibility to levofloxacin. Only 5 of 13 isolates (with ≥4-fold reduction in levofloxacin MIC) in the presence of EPIs showed an increased susceptibility to levofloxacin and other antibiotics. The overexpression of smeD and smeV genes (in five and one isolate, respectively) of 5 tested efflux pump operons was demonstrated. Sequencing analysis revealed 20-35 nucleotide mutations in local regulatory genes such as smeT and smeRv. However, mutations leading to an amino acid change were shown only in smeT (Arg123Lys, Asp182Glu, Asp204Glu) for one isolate and in smeRv (Gly266Ser) for the other isolate. Our data indicate that the overproduction of the SmeVWX efflux system, unlike SmeDEF, plays a significant role in the levofloxacin resistance.

Exploiting thiol-functionalized benzosiloxaboroles for achieving diverse substitution patterns – synthesis, characterization and biological evaluation of promising antibacterial agents

“…, phenylalanine-arginine-β-naphthylamide (PAβN). 57–59 It turned out that the activity of agents 12 and 13 against Enterobacterales is affected by the efflux phenomenon, as their MICs are reduced at least 4-fold in the presence of PAβN. Compounds 4 , 20 , and 21 are also actively extruded from bacterial cells, whereas for other compounds the efflux assay confirmed the lack of any activity.…”

“…Furthermore, only agents 12 and 13 displayed weak activity against Gram-negative rods with MICs ranging from 25 to >400 μg mL −1 (ESI,† Table S1). However, considering that Gram-negative bacilli resistance is frequently associated with efflux pumps' activity, 55–57 we also determined the MICs in the presence of their inhibitor, i.e. , phenylalanine-arginine-β-naphthylamide (PAβN).…”

“…Furthermore, only agents 12 and 13 displayed weak activity against Gram-negative rods with MICs ranging from 25 to >400 μg mL −1 (ESI, † Table S1). However, considering that Gram-negative bacilli resistance is frequently associated with efflux pumps' activity, [55][56][57] we also determined the MICs in the presence of their inhibitor, i.e., phenylalaninearginine-β-naphthylamide (PAβN). [57][58][59] It turned out that the activity of agents 12 and 13 against Enterobacterales is affected by the efflux phenomenon, as their MICs are reduced at least 4-fold in the presence of PAβN.…”

“…However, considering that Gram-negative bacilli resistance is frequently associated with efflux pumps' activity, [55][56][57] we also determined the MICs in the presence of their inhibitor, i.e., phenylalaninearginine-β-naphthylamide (PAβN). [57][58][59] It turned out that the activity of agents 12 and 13 against Enterobacterales is affected by the efflux phenomenon, as their MICs are reduced at least 4-fold in the presence of PAβN. Compounds 4, 20, and 21 are also actively extruded from bacterial cells, whereas for other compounds the efflux assay confirmed the lack of any activity.…”

Aromatic Diboronic Acids as Effective KPC/AmpC Inhibitors

“…The weak activity (MICs 50-400 mg/L) against Gram-negative rods (except P. aeruginosa) was found for some para-(1b-1f, 1i, and 1j) and meta-phenylenediboronic acids (2b-2e), as well as for 3a, 7a, and 7b (Table S2). Assuming that multidrug-resistant (MDR) efflux pumps may contribute to Gram-negative rod resistance, the activity of tested agents in the presence of the efflux pumps inhibitor phenylalanine-arginine-β-naphthylamide (PAβN) was also examined [60][61][62]. Interestingly, only MICs of compounds 2e, 3e, and 7b were significantly reduced in the presence of PAβN (by 4-16-fold).…”