Longitudinal Surveillance and Combination Antimicrobial Susceptibility Testing of Multidrug-Resistant Achromobacter Species from Cystic Fibrosis Patients

Ijeoma Okoliegbe* (Corresponding Author), Karolin Hijazi, Kim Cooper, Corinne Ironside, Ian M Gould

*Corresponding author for this work

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Achromobacter spp. are recognized as emerging pathogens in patients with cystic fibrosis (CF). Though recent works have established species-level identification using nrdA sequencing, there is a dearth in knowledge relating to species-level antimicrobial susceptibility patterns and antimicrobial combinations, which hampers the use of optimal antimicrobial combinations for the treatment of chronic infections. The aims of this study were to (i) identify at species-level referred Achromobacter isolates, (ii) describe species-level antimicrobial susceptibility profiles, and (iii) determine the most promising antimicrobial combination for chronic Achromobacter infections. A total of 112 multidrug-resistant (MDR) Achromobacter species isolates from 39 patients were identified using nrdA sequencing. Antimicrobial susceptibility and combination testing were carried out using the Etest method. We detected six species of Achromobacter and found that Achromobacter xylosoxidans was the most prevalent species. Interestingly, sequence analysis showed it was responsible for persistent infection (18/28 patients), followed by Achromobacter ruhlandii (2/3 patients). Piperacillin-tazobactam (70.27%) and co-trimoxazole (69.72%) were the most active antimicrobials. Differences were observed in species-level susceptibility to ceftazidime, carbapenems, ticarcillin-clavulanate, and tetracycline. Antimicrobial combinations with co-trimoxazole or tobramycin demonstrate the best synergy, while co-trimoxazole gave the best susceptibility breakpoint index values. This study enriches the understanding of MDR Achromobacter spp. epidemiology and confirms prevalence and chronic colonization of A. xylosoxidans in CF lungs. It presents in vitro data to support the efficacy of new combinations for use in the treatment of chronic Achromobacter infections.

Original languageEnglish
Article numbere01467-20
Number of pages10
JournalAntimicrobial Agents and Chemotherapy
Issue number11
Early online date20 Oct 2020
Publication statusPublished - Oct 2020

Bibliographical note

The authors would like to thank the laboratories and clinicians who use the Cystic Fibrosis Antibiotics Susceptibility testing service (CFASS) for their support in sending samples. CFASS is an adult patient testing facility funded by the National Services Division of the Common Services Agency of the Scottish Executive. Achromobacter spp. identification was supported by grants from the University of Aberdeen and the NHS Grampian Clinical Microbiology Fund (NHS Grampian Endowment Funds Registered Charity Number SC017296). IMG serves as a consultant to and/ speaker to Pfizer and MSD. All other authors declare no competing interest


  • Achromobacter spp
  • A. xylosoxidans
  • Cystic Fibrosis
  • Antimicrobial susceptibility testing
  • Synergy testing
  • Etest


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