Prevalence of Type III Secretion Protein Exoenzymes and Antimicrobial Susceptibility Patterns from Bloodstream Isolates of Patients with Pseudomonas aeruginosa Bacteremia

The purpose of this study was to determine the prevalence of two type III secretion effector proteins, exoU and exoS from bloodstream isolates of hospitalized patients with Pseudomonas aeruginosa (PSA) bacteremia, to characterize antimicrobial susceptibility patterns, and to compare mortality rates. PSA bloodstream isolates and antibiotic susceptibility profiles were collected from a university-affiliated hospital. ExoS and exoU genes were detected by polymerase chain reaction. Hospital mortality was assessed by medical chart review. 119 of 122 (97.5%) PSA bloodstream isolates contained either the exoS or exoU genes. ExoS was the most prevalent (n=86; 70.5%) followed by exoU (n=31; 25.4%), both genes (n=2; 1.6%) or neither gene (n=3; 2.5%). Isolates containing the exoU gene were significantly more likely to be resistant to cefepime, ceftazidime, piperacillin-tazobactam, carbapenems, fluoroquinolones, and gentamicin (p<0.05 for all). Mortality was high in patients with PSA bacteremia and did not differ among patients infected with the exoS isolates (n=3 7; 43%) or exoU isolates (n=11; 35%). One of two type III secretion effector proteins were almost universally present in PSA bloodstream isolates. Isolates containing the exoU gene were more likely to be resistant to multiple antibiotics..