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/ )

Automated summary

The study identified the genetic determinants contributing to multidrug resistance in Stenotrophomonas maltophilia strain MER1 isolated from hospital wastewater in Shandong Province, China. The strain showed resistance to multiple antibiotics and harbored genes encoding efflux pumps and drug-inactivating agents. The findings highlight the risk of spread of multidrug resistance genes in S. maltophilia to various ecological niches or medically high-risk pathogens.