Work

Description of Two Resistance-Nodulation-Cell Division Efflux Systems Involved in Acquired Antibiotic Resistance: AxySUV in Achromobacter xylosoxidans and AinCDJ in Achromobacter insuavis

Year: 2025

Type: article

Abstract: Background/Objectives: Achromobacter xylosoxidans and Achromobacter insuavis are emerging opportunistic pathogens. Several Resistance-Nodulation-cell Division (RND) efflux systems are involved in intrinsic or acquired antibiotic resistance (AxyABM, AxyXY-OprZ, and AxyEF-OprN). The aim of this study was to explore the resistance mechanisms in one-step mutants in which the efflux systems described to date are not involved: one mutant of A. insuavis AXX-A (AXX-A-Do1) and two mutants of A. xylosoxidans CIP102236 (CIP102236-El9 and CIP102236-Eo4) selected on fluoroquinolones. Methods: In vitro mutants were compared to parental isolates by WGS. RT–qPCR and gene inactivation were used to explore the role of the new efflux systems detected. Results: In the A. insuavis AXX-A mutant (AXX-A-Do1), WGS showed a substitution in the putative regulator of the new RND efflux system AinCDJ. The transporter gene ainD was 79-fold overexpressed in AXX-A-Do1, compared to its parental strain. The inactivation of ainD in AXX-A-Do1 led to a decrease in MICs of ciprofloxacin (8-fold), levofloxacin (8-fold), cefepime (≥8-fold), meropenem (4-fold), doripenem (4-fold), doxycycline (4-fold), minocycline (4-fold), tigecycline (4-fold) and chloramphenicol (≥8-fold). The MICs values obtained were similar to those of the parental strain AXX-A. The same approach allowed the detection of the new efflux system AxySUV in A. xylosoxidans CIP102236 mutants, in which substitutions in the putative AxySUV regulator were associated with the overexpression of the transporter gene axyU. axyU inactivation in the mutants led to a decrease in MICs of ciprofloxacin (8- to 16-fold), levofloxacin (4- to 8-fold), doripenem (4-fold), doxycycline (4-fold), minocycline (4-fold), and chloramphenicol (≥4-fold). Interestingly, axySUV is present in only about 50% of available A. xylosoxidans genomes, whereas ainCDJ is detected in all A. insuavis genomes. Conclusions: This study demonstrated that AinCDJ overproduction is involved in the acquired resistance of A. insuavis to cefepime, meropenem, doripenem, fluoroquinolones, minocycline, doxycycline, tigecycline, and chloramphenicol and that AxySUV overproduction is involved in the acquired resistance of A. xylosoxidans to meropenem, fluoroquinolones, minocycline, doxycycline, and chloramphenicol.

Source: Antibiotics

DOI: 10.3390/antibiotics14060536