Genomic data on multidrug (MDR) airborne bacteria from nonclinical settings in Tunisia, particularly childcare facilities, remain scarce. We aimed to characterize the genome of an MDR Serratia marcescens (S. marcescens) isolate recovered from indoor air and assess its relevance for public health surveillance.
Phenotypic characterization included antibiotic susceptibility testing (disc diffusion and broth microdilution) and quantification of biofilm formation. The underlying genetic basis was investigated via whole-genome sequencing (WGS), followed by bioinformatic analysis to characterize the resistome, virulome, and plasmid content. The S. marcescens strain EA1 exhibited an MDR phenotype, with resistance to 10 of the 23 tested antibiotics, including amoxicillin-clavulanic acid. Phenotypically, it displayed a strong biofilm-forming capacity and α-hemolytic activity. In silico resistome analysis supported the phenotypic profile by revealing antibiotic resistance determinants such as the AmpC β-lactamase gene (blaSRT-2) and efflux systems belonging to all four major families (ABC, MFS, RND, and SMR). The detection of genes associated with disinfectant tolerance (e.g., qacG) indicates the presence of genetic determinants that, if expressed, could contribute to persistence under hygiene‑related pressures; however, functional studies are needed to confirm this phenotype. Additionally, genomic islands characterized by insertion sequences and transposons were detected, suggesting a high potential for horizontal gene transfer. These elements were also present on the single pSM22 plasmid, highlighting a highly mobile and adaptable genome.
In this study, we report the first characterization of an MDR airborne S. marcescens strain (EA1) within the framework of environmental surveillance of indoor air quality in a childcare facility in Tunisia. These findings highlight the presence of genetic determinants associated with antimicrobial resistance, virulence, and disinfectant tolerance. Based on a single sentinel isolate, larger-scale sampling is required to assess generalizability.
Citation: Meher Cheberli, Sana Dhaouadi, Marwa Jabberi, Habib Chouchane, Ameur Cherif, Ramzi Boubaker Elandoulsi, Hadda-Imene Ouzari, Haitham Sghaier. Multidrug-resistant Serratia marcescens isolated from indoor air in a childcare facility: genomic insights into antibiotic resistance, virulence, and biofilm formation[J]. AIMS Environmental Science, 2026, 13(2): 395-414. doi: 10.3934/environsci.2026016
Genomic data on multidrug (MDR) airborne bacteria from nonclinical settings in Tunisia, particularly childcare facilities, remain scarce. We aimed to characterize the genome of an MDR Serratia marcescens (S. marcescens) isolate recovered from indoor air and assess its relevance for public health surveillance.
Phenotypic characterization included antibiotic susceptibility testing (disc diffusion and broth microdilution) and quantification of biofilm formation. The underlying genetic basis was investigated via whole-genome sequencing (WGS), followed by bioinformatic analysis to characterize the resistome, virulome, and plasmid content. The S. marcescens strain EA1 exhibited an MDR phenotype, with resistance to 10 of the 23 tested antibiotics, including amoxicillin-clavulanic acid. Phenotypically, it displayed a strong biofilm-forming capacity and α-hemolytic activity. In silico resistome analysis supported the phenotypic profile by revealing antibiotic resistance determinants such as the AmpC β-lactamase gene (blaSRT-2) and efflux systems belonging to all four major families (ABC, MFS, RND, and SMR). The detection of genes associated with disinfectant tolerance (e.g., qacG) indicates the presence of genetic determinants that, if expressed, could contribute to persistence under hygiene‑related pressures; however, functional studies are needed to confirm this phenotype. Additionally, genomic islands characterized by insertion sequences and transposons were detected, suggesting a high potential for horizontal gene transfer. These elements were also present on the single pSM22 plasmid, highlighting a highly mobile and adaptable genome.
In this study, we report the first characterization of an MDR airborne S. marcescens strain (EA1) within the framework of environmental surveillance of indoor air quality in a childcare facility in Tunisia. These findings highlight the presence of genetic determinants associated with antimicrobial resistance, virulence, and disinfectant tolerance. Based on a single sentinel isolate, larger-scale sampling is required to assess generalizability.
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Figures(5) / Tables(2)
Meher Cheberli, Sana Dhaouadi, Marwa Jabberi, Habib Chouchane, Ameur Cherif, Ramzi Boubaker Elandoulsi, Hadda-Imene Ouzari, Haitham Sghaier. Multidrug-resistant Serratia marcescens isolated from indoor air in a childcare facility: genomic insights into antibiotic resistance, virulence, and biofilm formation[J]. AIMS Environmental Science, 2026, 13(2): 395-414. doi: 10.3934/environsci.2026016
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