Data Sheet 1_Paving the way or sharing goods?—Interactions between pairs of Staphylococcus aureus and Pseudomonas aeruginosa sequentially isolated from respiratory samples of patients on mechanical ventilation.pdf

IntroductionBacterial colonization of medical devices is promoting hospital-acquired infections leading to worsening patient outcomes and high costs for society. Sequential bacterial colonization of surfaces may provide altered conditions that benefit pathogens.
MethodsIn this study we have investigated the interactions between two pairs of clinical isolates collected from patients that were on mechanical ventilation. Two patients were first colonized by Staphylococcus aureus and thereafter Pseudomonas aeruginosa settled. The two P. aeruginosa isolates were weak colonizers in monoculture. We investigated two hypotheses: (1) S. aureus preconditions material surfaces, facilitating adhesion of later colonizers. (2) S. aureus provides an altered nutrient environment promoting the growth and settlement of other bacteria.
ResultsSurface preconditioning did not seem to enhance colonization of P. aeruginosa. However, bacterial growth, biofilm formation, ratio of colony forming units, and metabolic profiles were influenced by co-cultivation. The effects varied depending on nutrient content in the medium.
DiscussionIn general, co-cultures appeared to benefit clinical isolates to a higher degree, compared to reference strains. The results indicate that differences in airway microenvironment between patients may have a large effect on the infection process and which pathogens that persist.