Pressure- and temperature-dependent adhesion of Pseudomonas aeruginosa to HEp-2 cells

Pseudomonas aeruginosa bacteria adhere to human epitheloid (HEp-2) cells in culture. Under normal atmospheric conditions (1 ATA), this adhesion increased significantly when the temperature rose from 22 to 37 degrees C. Under hyperbaric atmosphere (= air, 7 ATA) conditions, a similar, significant enhancement of bacterial adhesion to the cells was noted when the temperature rose. If the temperature was kept stable at 22 or 37 degrees C and the pressure was increased from 1 to 7 ATA, a pressure-induced enhancement was observed. This was statistically significant, at both temperature levels. Temperature-induced or -stimulated adhesion may help to explain some outbreaks of P. aeruginosa infections, for instance in whirlpools. The enhancement of this phenomenon under hyperbaric atmosphere conditions could have some relevance to recurrent P. aeruginosa otitis externa, a most common nuisance among professional divers.