A case oriented study: Whole genome sequencing (WGS) on a wild urease negative Proteus mirabilis isolated from deep surgical site infection (SSI) at El Hussein University Hospital, Al Azhar University Cairo, Egypt

Abstract

Background: Proteus mirabilias  ( P. mirabilis) strains are motile Gram negativerods that colonize the humangastrointestinal tract and could be a source of nosocomial infections especially in immune compromised cancer patients. Proteus mirabilis is identified by its urease production as a major bacterial virulence especially in urinary tract infections. Aim: This study aimed to characterize a case of a urease negative P. mirabilis isolated from a cancer patient suffering from deep surgical site infection.  Methods: Conventional biochemical tests performed on swarming bacterial growth cultures were characteristic of P. mirabilis except for urease production. Identification was confirmed by Vitek-2 compact system and Vitek- MS. Dienes test proved the isolate is antigenically different from other urease positive P. mirabilis. Whole genome sequencing (WGS) identified this P. mirabilis strain with the seven encoding urease genes ureABCDEFG as well as their positive regulator gene UreR. Results: Mutations were found within amino acid sequences of UreB, UreE, UreF and UreG and UreR. Antibiotic sensitivity as well as WGS identified resistance genes to multiple classes of antibiotics.  Conclusion: This is the first report of a wildly existed urease negative P. mirabilis due to mutations in the urease gene cluster (UreABC) as well as the regulator UreR. Questions are raised towards the urease enzyme as a key virulence factor to P. mirabilis. Other virulence factors that allow this species to cause other severe infections should be considered. The rate of isolation of urease negative P. mirabilis should be monitored and assessed in the future.