TonB‐dependent uptake of β‐lactam antibiotics in the opportunistic human pathogen Stenotrophomonas maltophilia

Abstract

The β‐lactam antibiotic ceftazidime is one of the handful of drugs with proven clinical efficacy against the important opportunistic human pathogen Stenotrophomonas maltophilia. Here, we show that mutations in the energy transducer TonB, encoded by smlt0009 in S. maltophilia, confer ceftazidime resistance and smlt0009 mutants have reduced uptake of ceftazidime. This breaks the dogma that β‐lactams enter Gram‐negative bacteria only by passive diffusion through outer membrane porins. We also show that ceftazidime‐resistant TonB mutants are cross‐resistant to fluoroquinolone antimicrobials and a siderophore‐conjugated lactivicin antibiotic designed to target TonB‐dependent uptake. This implies that attempts to improve the penetration of antimicrobials into S. maltophilia by conjugating them with TonB substrates will suffer from the fact that β‐lactams and fluoroquinolones coselect resistance to these novel and otherwise promising antimicrobials. Finally, we show that smlt0009 mutants already exist among S. maltophilia clinical isolates and have reduced susceptibility to siderophore‐conjugated lactivicin, despite the in vitro growth impairment seen in smlt0009 mutants selected in the laboratory.

Antimicrobial Peptide Exposure Selects for Resistant and Fit Stenotrophomonas maltophilia Mutants That Show Cross-Resistance to Antibiotics

“…Since these clones had only one mutation in the mraW gene, this change is responsible for the phenotype. Although DA61758 also harbored a mutation in mraW, it also contained a deletion in the TonB-coding gene, which has been reported to be involved in beta-lactam resistance in S. maltophilia (23). The increase in the MICs of aminoglyco-sides for the PR-39-evolved populations was only observed in some of the isolates.…”

Pharma‐molecule Transport across Bacterial Membranes: Detection and Quantification Approaches by Electrochemistry and Bioanalytical Methods

“…[7, 10-12, 23, 28, 40, 49-52] These methods are based on signal collection at as olid-liquid interface,a nd hence transport is intrinsic to its signals.Awide range of chemical analytical methods can be applied in accumulative transport measurements,i ncluding but not limited to optical and chromatographic methods.T he majority of the papers surveyed reported well-established and conventional methods of quantification in bacterial transport research. These methods include the BLM method, [9,11,[13][14][15][20][21][22][23][24] spectrofluorimetry, [6,7,10,24,25,71,74] and MS. [7,8,16,21] In contrast, some researchers employed innovative transport assays or mathematical parameters.Among these are the sensor for hydrophobic amino acids constructed by Fitzgerald et al [32] the BacPK SPE-MSbased assay devised by Widya et al, [77] the optofluidic permeability assay developed by Cama et al, [13] the permeability scoring function created by Acosta-GutiØrrez et al, [9] and the SECM technique utilized by Hannesschlaeger et al [17] Each method can be characterized by its underlying principle, generated signal, advantages and disadvantages,t ypes of quantitative data collected, and the relevance of this quantitative data to antibiotic resistance.…”

“…Finally,i ti sp ossible to relate quantitative transport to drug resistance quantifiers,s uch as minimum inhibitory concentration (MIC), as demonstrated by CalvopiÇa et al [25] on the example of ceftazidime,a nd Prochnow et al [26] when investigating the AcrAB-TolC efflux pump.A tt hese examples,i tb ecomes clear why diverse methods for transmem-brane drug transport quantification are of such broad importance.…”

Pharma‐molecule Transport across Bacterial Membranes: Detection and Quantification Approaches by Electrochemistry and Bioanalytical Methods

“…[7, 10-12, 23, 28, 40, 49-52] These methods are based on signal collection at as olid-liquid interface,a nd hence transport is intrinsic to its signals.Awide range of chemical analytical methods can be applied in accumulative transport measurements,i ncluding but not limited to optical and chromatographic methods.T he majority of the papers surveyed reported well-established and conventional methods of quantification in bacterial transport research. These methods include the BLM method, [9,11,[13][14][15][20][21][22][23][24] spectrofluorimetry, [6,7,10,24,25,71,74] and MS. [7,8,16,21] In contrast, some researchers employed innovative transport assays or mathematical parameters.Among these are the sensor for hydrophobic amino acids constructed by Fitzgerald et al [32] the BacPK SPE-MSbased assay devised by Widya et al, [77] the optofluidic permeability assay developed by Cama et al, [13] the permeability scoring function created by Acosta-GutiØrrez et al, [9] and the SECM technique utilized by Hannesschlaeger et al [17] Each method can be characterized by its underlying principle, generated signal, advantages and disadvantages,t ypes of quantitative data collected, and the relevance of this quantitative data to antibiotic resistance.…”

“…Finally, it is possible to relate quantitative transport to drug resistance quantifiers, such as minimum inhibitory concentration (MIC), as demonstrated by Calvopiña et al [25] on the example of ceftazidime, and Prochnow et al [26] when investigating the AcrAB‐TolC efflux pump. At these examples, it becomes clear why diverse methods for transmembrane drug transport quantification are of such broad importance.…”