Physiological adaptations of clinical vs. indoor environmental strains of Pseudomonas aeruginosa in a hospital setting

Pseudomonas aeruginosa is a remarkably adaptive bacterium frequently implicated in severe, sometimes fatal infections within healthcare institutions. The origins of clinical strains have generated considerable debate, suggesting that infectious variants emerge through selection from a broader environmental bacterial population. Our investigation explored the physiological differences between environmental (indoor) and clinical strains of P. aeruginosa isolated from a hospital over a year. We assessed various parameters, including survival patterns, antibiotic resistance, vulnerability to ciliate predation, bacterial antagonism, and motility. Despite the minimal incidence of patient infections during our observation, environmental P. aeruginosa was prevalent throughout the hospital during our study. Clinical strains exhibited diminished resistance to certain antibiotics, increased resistance against ciliate predators, and enhanced swarming and swimming motility compared to their environmental counterparts. Clinical strains maintained higher cell densities under starvation conditions but were outcompeted by environmental strains in a nutrient medium. In conclusion, our study suggests that P. aeruginosa clinical isolates possess unique physiological adaptations that may favor host colonization.