Quorum Sensing - Dependent Virulence Factors and Biofilm Formation of Pseudomonas Aeruginosa Isolates from Retrieved Orthopedic Implants

Abstract

Background: Quorum sensing (QS) plays a crucial role in medical device-related infections. However, epidemiological analysis of QS- dependent virulence factors among Pseudomonas aeruginosa (P. aeruginosa) isolates from orthopedic implants-related infections has rarely been reported. Objective: to assess some QS-dependent virulence factors (as pyocyanin, elastase, protease, rhamnolipid, and biofilm production) in P. aeruginosa isolates from retrieved different orthopedic implants. Methodology: Twenty-four P. aeruginosa isolates obtained from 300 retrieved orthopedic implants with proven diagnosis of osteoarticular infection directly related to orthopedic implants were investigated for production of QS-dependent virulence factors. The pyocyanin production was assayed using King A media, rhamnolipid production was checked utilizing cetyltrimethylammonium bromide (CTAB) agar test. Elastin lytic activity was assayed using elastin Congo red, total protease was estimated using the modified skimmed milk assay technique, and the biofilm forming ability was assayed by microtiter plate assay. N-acyl homoserine lactones (3-oxo-C 12 -HSL, C 4 -HSL) were detected by Cross-feeding bioassay. Polymerase chain reaction (PCR) was used to assess the presence of the QS genes lasI, lasR, rhlI, and rhlR in P. aeruginosa isolates. Results: Seventeen isolates (70.8%) displayed the QS-dependent phenotypes and seven isolates were found to be lacking all tested virulence factors. The lack of production of pyocyanin, Rhamnolipid, las B elastase, total protease, and biofilm formation by the seven isolates proposed that they might have a defective QS system. Among the Seven isolates exhibiting impaired QS-dependent phenotypes, AHLs autoinducers were present in three isolates, though the residual four isolates were lacking both autoinducers and therefore are considered QS-deficient. PCR analysis declared that two isolates contained lasI, lasR, rhlI and rhlR genes while one isolate lacked lasR gene, and one isolate was lacking the four tested genes. Conclusion: Although QS seems to be a crucial regulator of virulence factors and biofilm formation in P. aeruginosa, it is equipped to produce implant infection in humans despite an impaired QS system. These results do not challenge the concept that QS plays a foremost role in P. aeruginosa pathogenicity, but highlight that along with known virulence factors, perhaps there are other virulence factors, that may not be strictly under QS control.