The trojan horse: Serratia marcescens. Importance in the dissemination, uptake and maintenance of genes associated with antimicrobial resistance in the hospital environment

A. S. GAMBINO; A. C. LEGUINA; C. A. KNECHT; L. C. CARRERA PÁEZ

Congreso; International Union of Microbiological Societies (IUMS); 2022

Serratia marcescens SCH909 is a multidrug resistant strain isolated in 1988 harboring three class 1 integrons. We wondered ifthese integrons were retained over time and if there were other antimicrobial resistant determinants contributing to itsmultidrug resistant profile. Genomic analysis showed a fourth multidrug resistance integron, a Tn7 transposon withdfrA1-sat2-ybeA-ybfA-ybfB-ybgA gene cassettes in the variable region. Insertion sequences were involved in the genesis ofnovel composite transposons in the L4 subtype plasmid pSCH909, such as Tn6824 carrying an arsenic regulon and two headto head class 1 integrons surrounded by two complete IS1. Remarkably, a novel chromosomal genomic island, SmaR, wasidentified, closely related to Multiple Antimicrobial Resistance Regions (MARR), usually found in AbaR0-type and AbGRI2-0from global clones of Acinetobacter baumannii, and in M-type plasmids circulating in Enterobacteriaceae. Maintenance studiesshowed that the three class 1 integrons were maintained over 1 month without antimicrobial pressure. Since S. marcescensis considered a relevant nosocomial pathogen that can have a wide range of niches – human, plant, animal, soil andinanimate surfaces, our findings support the ability of this species to capture, maintain and spread a broad variety ofantimicrobial resistance elements.