Abstract

The pathogenic potential of Pseudomonas aeruginosa comes from the expression of many secreted and cell surface virulence factors, and its biofilm formation. This study aimed to investigate and compare the virulence profiles of 123 clinical and environmental P. aeruginosa isolated in Meknes (Morocco). Using suitable culture media, phenotypic screening evaluated the production of β-haemolysin, caseinase, lipase, lecithinase, pyocyanin and pyoverdin, as well as the ability to swim, swarm and twitch. Biofilm formation kinetics was assessed using microtiter test plates. Data analysis was performed using Statistic Package of the Social Science software (version 21.0). High percentages of strains expressed caseinase (99.2%), β-heamolysin (95.1%), lipase (100%) and lecithinase (100%). 95.9% of isolates produced either pigment. All strains were able to swim, warm and twitch, at different levels. All strains were biofilm producers, and the evolution of adherent biomass over time varies greatly from strain to strain. Significant positive correlations were observed between proteolytic and hemolytic activities; biofilm formation and twitching; as well as swimming, swarming and twitching motilities. Twitching and swimming were significantly higher in environmental strains, which were also quickly adhered and formed denser biofilms. Clinical strains showing significantly higher proteolytic activity were isolated from cardiology ward, and those with higher twitching and denser biofilm were from the thoracic service. Inpatient strains were significantly earlier producer of denser biofilm than outpatient ones. P. aeruginosa strains tested have a collection of virulence markers required to cause disease in different tissues. Such bacteria present a serious therapeutic challenge for treatment of both community-acquired and nosocomial infections.

Key words: Biofilm, clinical, environmental, Pseudomonas aeruginosa, virulence factors.