Supporting information for "Whole-genome sequencing analysis unveiled the genomic signatures of virulence and resistance in clinical Serratia marcescens isolates from India"

Serratia marcescens is an opportunistic pathogen that is widely known to cause healthcare-associated infections with significant morbidity and mortality, particularly in high-risk settings. In this study, the genomic characteristics of S. marcescens isolates from an Indian tertiary care hospital outbreak of septicemia were investigated to better understand the genetic elements associated with pathogenicity and antibiotic resistance. The approximate genome size of the studied genomes was 5.05 Mb with a G+C content of 59.39%, similar to the reference strain ATCC13880. An Average Nucleotide Identity (ANI) of 95.6% and digital DNA-DNA Hybridization (dDDH) estimate of 79.58% taxonomically validated the query genome. Several mobile genetic elements, such as prophage sequences, genomic islands, and plasmid sequences, IncFIB(K), were present in the genome encoding various virulence and fitness traits, including FlhDC-ShlBA, Type Six Secretion System, pgaABCD operon, mannose-resistant (MR), and mannose-sensitive (MS) pilus. Phenotypic resistance to aminoglycoside group of antibiotics (gentamicin) was observed in 43% of the isolates analyzed, encoding aminoglycoside modifying enzymes, eight isolates that showed resistance to cefepime and aztreonam carried CTX-M-15, OXA-1, TEM-1 beta-lactamase resistance genes. Seven co-trimoxazole-resistant isolates harbored drfA14 and sul2 which confer resistance to trimethoprim and sulphonamide, respectively. None of the 16 S. marcescens isolates showed complete resistance to the fluoroquinolones tested in this study. The observations from this study highlight the severity and pathogenic versatility of the S. marcescens isolates.