Comparative insights into multiple drug resistance determinants in Stenotrophomonas maltophilia MER1

Objectives: Multidrug-resistant (MDR) Stenotrophomonas maltophilia strain MER1 was isolated from hos-pital wastewater in Shandong Province, China. This study aimed to determine the genetic determinants related to its striking MDR phenotype. Methods: Antimicrobial susceptibility testing of strain MER1 was performed by disk diffusion on Mueller- Hinton agar plates, and MICs were interpreted according to Clinical and Laboratory Standards Institute breakpoints. The genome of MER1 was sequenced and assembled using PacBio RS II and BGISEQ-500 platforms. Antimicrobial resistance determinants together with other transferability or adaptability deter-minants were identified by comparative genomics. Phylogenetic and contextual assays for these elements were conducted to assess the risk of spread of MER1. Results: Antimicrobial susceptibility testing revealed that strain MER1 is resistant to nine different antibi-otics, including ampicillin, meropenem, amikacin, erythromycin, vancomycin, tetracycline, tigecycline, col-istin and ceftazidime. Several genes were identified encoding efflux pumps and drug-inactivating agents, accounting for resistance to the above antibiotics, including meropenem, tigecycline and colistin regarded as last-line therapies for infections caused by MDR Gram-negative bacteria. MER1 co-harbours two non-mobile mcr homologues. A novel genomic region of variability was demonstrated to confer bacterial ro-bustness and adaptability upon strain MER1. Conclusion: Collective effort s revealed the MDR properties and potential genetic determinants of S. mal-tophilia MER1 isolated from hospital wastewater. Comparative genomic analysis of S. maltophilia MER1 may provide insights into the prevention and treatment of antimicrobial-resistant infections. Our find-ings raise concern that the MDR genes in the reservoir of S. maltophilia may further spread into various ecological niches or medically high-risk pathogens. (c) 2021 The Author(s). Published by Elsevier Ltd on behalf of International Society for Antimicrobial Chemotherapy. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ )