Characteristics of Serratia rubidaea Clinical Strain Revealed Multiple Resistance to Antibiotics and Disinfectants

A clinical strain of the opportunistic pathogen Serratia rubidaea, a known contaminant of healthcare environments and an emerging cause of invasive infections, is described. The studied isolate, recovered from a nurse’s hand skin swab during routine screening, exhibits a broad profile of antibiotic resistance combined with reduced susceptibility to several disinfectants. Phenotypic susceptibility testing using a tablet-based microdilution and disk diffusion method was employed to determine the minimum inhibitory concentrations (MICs) of antimicrobial agents from different classes, while broth microdilution assays with disinfectants revealed high-level tolerance to widely used agents, including 70% C2H5OH, 3% H2O2, 0.05% polyhexamethylene guanidine (PHMG) and others. Whole-genome sequencing identified multiple resistance-associated determinants, such as chromosome-encoded class C β-lactamase (ampC), several efflux systems (sdeXY, macAB, and emrAB) combined with multicopy tolC, and specific transferases (fos and arnT). Shotgun bottom-up HPLC-MS/MS proteomics confirmed baseline expression of these and other stress-tolerance-related proteins under non-inducing conditions. Taken together, these data underscore the importance of surveillance for Serratia spp. in healthcare facilities to detect strains that combine intrinsic or acquired multidrug resistance with robust survival traits such as disinfectant tolerance and biofilm formation. The present study provides a reference-level phenotypic, genomic, and proteomic characterization of a S. rubidaea clinical isolate, contributing to the understanding of the adaptive potential of this resilient opportunistic pathogen in clinical environments.