Diversity of virulence phenotypes among type III secretion negative Pseudomonas aeruginosa clinical isolates.
Pseudomonas aeruginosa is a frequent cause of acute infections. The primary virulence factor that has been linked to clinical disease is the type III secretion system, a molecular syringe that delivers effector proteins directly into host cells. Despite the importance of type III secretion in dictating clinical outcomes and promoting disease in animal models of infections, clinical isolates often do not express the type III secretion system in vitro. Here we screened 81 clinical P. aeruginosa isolates for secretion of type III secretion system substrates by western blot. Non-expressing strains were also subjected to a functional test assaying the ability to intoxicate epithelial cells in vitro, and to survive and cause disease in a murine model of corneal infection. 26 of 81 clinical isolates were found to be type III secretion negative by western blot. 17 of these 26 non-expressing strains were tested for their ability to cause epithelial cell rounding. Of these, three isolates caused epithelial cell rounding in a type III secretion system dependent manner, and one strain was cytotoxic in a T3SS-independent manner. Five T3SS-negative isolates were also tested for their ability to cause disease in a murine model of corneal infection. Of these isolates, two strains caused severe corneal disease in a T3SS-independent manner. Interestingly, one of these strains caused significant disease (inflammation) despite being cleared. Our data therefore show that P. aeruginosa clinical isolates can cause disease in a T3SS-independent manner, demonstrating the existence of novel modifiers of clinical disease.
Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, Ohio, United States of America.
Jonida
J
Toska
Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio, United States of America.
Yan
Y
Sun
Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, Ohio, United States of America.
Dalina Alvarez
DA
Carbonell
Department of Pathology, Case Western Reserve University and University Hospitals Case Medical Center, Cleveland, Ohio, United States of America.
Altreisha N-S
AN
Foster
Department of Pathology, Case Western Reserve University and University Hospitals Case Medical Center, Cleveland, Ohio, United States of America.
Michael R
MR
Jacobs
Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio, United States of America.
Eric
E
Pearlman
Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, Ohio, United States of America.
Arne
A
Rietsch
D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D001426:Bacterial Proteins / Q000378:metabolism*; D058947:Bacterial Secretion Systems / Q000502:physiology*; D015153:Blotting, Western; D003316:Corneal Diseases / Q000276:immunology / Q000382:microbiology* / Q000473:pathology; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000276:immunology / Q000382:microbiology; D051379:Mice; D008810:Mice, Inbred C57BL; D010641:Phenotype; D011014:Pneumonia / Q000276:immunology / Q000382:microbiology* / Q000473:pathology; D011552:Pseudomonas Infections / Q000276:immunology / Q000382:microbiology* / Q000473:pathology; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000302:isolation & purification* / Q000472:pathogenicity*; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured; D014774:Virulence; D037521:Virulence Factors / Q000235:genetics
D000907:Antibodies, Bacterial; D001426:Bacterial Proteins; D058947:Bacterial Secretion Systems; D012333:RNA, Messenger; D037521:Virulence Factors