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Multidrug-resistant Stenotrophomonas maltophilia in residential aged care facilities: An emerging threat
Sylvia A Sapula1, Bradley J Hart1, Naomi L Siderius1
1Health and Biomedical Innovation, UniSA Clinical and Health Sciences, University of South Australia, Adelaide, South Australia, Australia.
Abstract:
Stenotrophomonas maltophilia is a multidrug-resistant (MDR), Gram-negative bacterium intrinsically resistant to beta-lactams, including last-resort carbapenems. As an opportunistic pathogen, it can cause serious healthcare-related infections. This study assesses the prevalence, resistance profiles, and genetic diversity of S. maltophilia isolated from residential aged care facilities (RACFs). RACFs are known for their overuse and often inappropriate use of antibiotics, creating a strong selective environment that favors the development of bacterial resistance. The study was conducted on 73 S. maltophilia isolates recovered from wastewater and facility swab samples obtained from three RACFs and a retirement village. Phenotypic and genotypic assessments of the isolates revealed high carbapenem resistance, exemplifying their intrinsic beta-lactam resistance. Alarmingly, 49.3% (36/73) of the isolates were non-wild type for colistin, with minimum inhibitory concentration values of > 4 mg/L, and 11.0% (8/73) were resistant to trimethoprim-sulfamethoxazole. No resistance mechanisms were detected for either antimicrobial. Genotypic assessment of known lineages revealed isolates clustering with Sm17 and Sm18, lineages not previously reported in Australia, suggesting the potential ongoing spread of MDR S. maltophilia. Lastly, although only a few isolates were biocide tolerant (2.7%, 2/73), their ability to grow in high concentrations (64 mg/L) of triclosan is concerning, as it may be selecting for their survival and continued dissemination.
Insights
Multidrug-resistant Stenotrophomonas maltophilia is prevalent in aged care facilities, showing high carbapenem resistance and concerning colistin resistance. New lineages suggest ongoing spread of this opportunistic pathogen.
Area of Science:
- Medical Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Stenotrophomonas maltophilia is a multidrug-resistant (MDR), Gram-negative bacterium causing healthcare-associated infections.
- Residential aged care facilities (RACFs) present a selective environment for antibiotic resistance due to antibiotic overuse.
- Understanding S. maltophilia prevalence and resistance in RACFs is crucial for infection control.
Purpose of the Study:
- To assess the prevalence, resistance profiles, and genetic diversity of S. maltophilia in Australian RACFs.
- To investigate carbapenem, colistin, and trimethoprim-sulfamethoxazole resistance.
- To identify genetic lineages and potential biocide tolerance.
Main Methods:
- Isolation and identification of 73 S. maltophilia strains from wastewater and swabs in RACFs.
- Phenotypic testing for antimicrobial susceptibility (MICs) and biocide tolerance.
- Genotypic analysis to determine S. maltophilia lineages.
Main Results:
- High carbapenem resistance was observed, consistent with intrinsic beta-lactam resistance.
- 49.3% of isolates showed non-wild type colistin resistance (> 4 mg/L); 11.0% were resistant to trimethoprim-sulfamethoxazole.
- New lineages (Sm17, Sm18) were identified in Australia, and some isolates exhibited triclosan tolerance.
Conclusions:
- S. maltophilia is a significant MDR pathogen in RACFs, exhibiting concerning resistance patterns.
- The presence of novel lineages suggests potential for ongoing dissemination.
- Biocide tolerance, particularly to triclosan, may contribute to pathogen survival and spread in these environments.
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