Pseudomonas aeruginosa in a hydropathic facility: diversity, susceptibility and imipenem resistance mutation

To detect Pseudomonas aeruginosa in water and treatment equipment biofilms of a thermae hydropathic facility and to study antibiotic susceptibility and genetic diversity.

One hundred and fifty-four planktonic isolates were obtained from 2220 water samples during 4 years. Seventy-two biofilm isolates were obtained from 23 samples of inner parts of three inhalation equipments. Antibiotic susceptibility was determined by disc diffusion. All isolates were susceptible to tested antimicrobials, except two biofilm isolates and one planktonic isolate. Twenty-one resistant mutants were observed (nine from biofilms), mostly with imipenem (IP) resistance (81%), by diminished expression of OprD porin, as it was observed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Random amplification polymorphic DNA showed a genetically heterogeneous population that is spread through the entire system and persistent in time. IP resistance mutation ability was spread through the population.

The permanent assessment of Ps. aeruginosa is necessary not only in water, as expressed in official programmes, but also in equipments where biofilms are evident. Ps. aeruginosa was more prevalent in biofilm populations and presented higher ability to adapt to antibiotic pressure.

Twenty-one million people use thermae in Europe. Official microbiological quality control programmes only consider water surveillance. Present study proves the need of a review on current official programmes.