Broad-Spectrum Adaptive Antibiotic Resistance Associated with Pseudomonas aeruginosa Mucin-Dependent Surfing Motility

Surfing motility is a novel form of surface adaptation exhibited by the nosocomial pathogen Pseudomonas aeruginosa in the presence of the glycoprotein mucin, which is found in high abundance at mucosal surfaces, especially those of the lungs of cystic fibrosis and bronchiectasis patients. Here, we investigated the adaptive antibiotic resistance of P. aeruginosa under conditions in which surfing occurs compared that in to cells undergoing swimming. P. aeruginosa surfing cells were significantly more resistant to several classes of antibiotics, including aminoglycosides, carbapenems, polymyxins, and fluoroquinolones. This was confirmed by incorporation of antibiotics into growth medium, which revealed a concentration-dependent inhibition of surfing motility that occurred at concentrations much higher than those needed to inhibit swimming. To investigate the basis of resistance, transcriptome sequencing (RNA-Seq) was performed and revealed that surfing influenced the expression of numerous genes. Included among genes dysregulated under surfing conditions were multiple genes from the Pseudomonas resistome; these genes are known to affect antibiotic resistance when mutated. Screening transposon mutants in these surfing-dysregulated resistome genes revealed that several of these mutants exhibited changes in susceptibility to one or more antibiotics under surfing conditions, consistent with a contribution to the observed adaptive resistance. In particular, several mutants in resistome genes, including armR, recG, atpB, clpS, nuoB, and certain hypothetical genes, such as PA5130, PA3576, and PA4292, showed contributions to broad-spectrum resistance under surfing conditions and could be complemented by their respective cloned genes. Therefore, we propose that surfing adaption led to extensive multidrug adaptive resistance as a result of the collective dysregulation of diverse genes.