Serological Classification and Comparison of Cell Surface Hydrophobicity and Biofilm and Proteases Formation between the Clinical and Environmental Isolates of Pseudomonas Aeruoginosa

Background & Aims: Pseudomonas aeruoginosa is an opportunistic pathogen and an important cause of nosocomial infections. Different factors are involved in the pathogenicity of this bacterium. This study was performed to compare some factors associated with the virulence of clinical and environmental isolates of P. aeruoginosa. Methods: The present study was performed on 25 environmental isolates (soil, water) and 100 clinical isolates (blood, urine, wound, burn wound, and body fluids). Serotyping was performed with monovalent and polyvalent antisera. Cell surface hydrophobicity (CSH) was tested through bacterial attachment to hydrocarbons, and biofilm formation was detected through crystal violet staining method. LasA protease and LasB elastase were determined using Gongo red or boiled Staphylococcus aureus suspension as the substrates, respectively. LasR gene was detected using polymerase chain reaction (PCR) method. Results: The most common serotype among the isolates was serotype B (23.52% in clinical and 12% in environmental isolates). Serotype B was more prevalent in clinical isolates, and serotype J was found with a higher frequency in environmental samples. This serotype was not found in clinical samples. Mean production of CSH, biofilm formation, and LasA protease and LasB elastase was higher in the clinical isolates than environmental isolates. The difference between clinical and environmental isolates was significant in the case of LasA protease (P = 0.010). The LasR genes was detected in all clinical and environmental isolates Conclusion: Differences in serotype prevalence and the higher prevalence of LasA in the clinical isolates is an important issue. Owing to the lack of significant differences between clinical and environmental samples in respect to other virulence factors, it seems that the expression of virulence factors could be effected by environmental conditions. Further studies with higher number of isolates and evaluation of virulence gene expression is needed to confirm these results