Abstract Description

Until as recently as 2018, antibiotic and disinfectant resistance development were viewed as separate occurrences. However, rising deaths due to antimicrobial resistance and the growing threat of hospital-acquired infections (HAIs) since the SARS-CoV-2 pandemic, begs the question of potential links between the two. This study (2022–2023) examined whether exposure to disinfectants, particularly since the recent pandemic, contributes to co-resistance development in nosocomial pathogens. Minimum Inhibitory Concentration (MIC) tests were performed in triplicate on clinical multidrug-resistant (MDR) Serratia strains and Serratia marcescens ATCC 13880 wild type, assessing susceptibility to Ampicillin and Quaternary Ammonium Compound (QAC)-based disinfectants. Resistance to QACs was then experimentally induced in both strains in triplicate, through 10 days of sub-lethal exposure to QAC.This was done to determine QAC resistance development rate in sub-MIC environments. Post-induction Ampicillin MICs were determined, to extrapolate if QAC resistance induction had effects on Ampicillin susceptibility. Clinical strains already showed reduced QAC susceptibility compared to wild type, suggesting in-hospital resistance acquisition due to prior sub-MIC exposure. After induction, the wild type and clinical strains exhibited 31.5-fold and 12.2-fold reductions in QAC susceptibility, respectively. Notably, without any antibiotic exposure, both strains showed increased resistance to Ampicillin—1.6-fold in wild type and 2.7-fold in the clinical isolates. These results confirm that even brief exposure to sub-lethal QAC levels can drive significant disinfectant resistance and simultaneously reduce antibiotic susceptibility. This demonstrates co-resistance development between disinfectants and antibiotics, emphasizing the risk that patients may acquire MDR nosocomial infections from environmental bacteria that developed resistance following exposure to sub-MIC levels of disinfectants within hospital settings.