Prevalence of type III secretion genes in clinical and environmental isolates of Pseudomonas aeruginosa.
The type III secretion system of Pseudomonas aeruginosa transports four known effector proteins: ExoS, ExoT, ExoU and ExoY. However, the prevalence of the type III secretion system genes or the effector-encoding genes in clinical and environmental isolates of P. aeruginosa has not been well studied. Southern hybridization analyses and PCR were performed on over 100 P. aeruginosa isolates to determine the distribution of these genes. Clinical isolates were obtained from urine, endotracheal, blood and wound specimens, from the sputum of cystic fibrosis (CF) patients, and from non-hospital environmental sites. The popB gene was used as a marker for the presence of the large chromosomal locus encoding the type III secretion machinery proteins. Each isolate contained the popB gene, indicating that at least a portion of this large chromosomal locus was present in all isolates. Likewise, each isolate contained exoT-like sequences. In contrast, the exoS, exoU and exoY genes were variable traits. Overall, 72% of examined isolates contained the exoS gene, 28% contained the exoU gene, and 89% contained the exoY gene. Interestingly, an inverse correlation was noted between the presence of the exoS and exoU genes in that all isolates except two contained either exoS or exoU but not both. No significant difference in exoS, exoU or exoY prevalence was observed between clinical and environmental isolates or between isolates cultured from different disease sites except for CF respiratory isolates. CF isolates harboured the exoU gene less frequently and the exoS gene more frequently than did isolates from some of the other sites of infection, including the respiratory tract of patients without CF. These results suggest that the P. aeruginosa type III secretion system is present in nearly all clinical and environmental isolates but that individual isolates and populations of isolates from distinct disease sites differ in their effector genotypes. The ubiquity of type III secretion genes in clinical isolates is consistent with an important role for this system in human disease.
Feltman
Heather
H
Departments of Microbiology/Immunology1, Medicine2 and Pathology3, Northwestern University, Chicago, IL 60611, USA.
Schulert
Grant
G
Departments of Microbiology/Immunology1, Medicine2 and Pathology3, Northwestern University, Chicago, IL 60611, USA.
Khan
Salman
S
Departments of Microbiology/Immunology1, Medicine2 and Pathology3, Northwestern University, Chicago, IL 60611, USA.
Jain
Manu
M
Departments of Microbiology/Immunology1, Medicine2 and Pathology3, Northwestern University, Chicago, IL 60611, USA.
Peterson
Lance
L
Departments of Microbiology/Immunology1, Medicine2 and Pathology3, Northwestern University, Chicago, IL 60611, USA.
Hauser
Alan R
AR
Departments of Microbiology/Immunology1, Medicine2 and Pathology3, Northwestern University, Chicago, IL 60611, USA.
D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D003550:Cystic Fibrosis / Q000453:epidemiology* / Q000382:microbiology; D004783:Environmental Microbiology; D005798:Genes, Bacterial; D005964:Glucosyltransferases / Q000235:genetics / Q000378:metabolism; D000071677:Histidine Kinase; D006801:Humans; D052899:Pore Forming Cytotoxic Proteins; D015995:Prevalence; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D011552:Pseudomonas Infections / Q000453:epidemiology / Q000382:microbiology; D011550:Pseudomonas aeruginosa / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism
D001426:Bacterial Proteins; C412007:PopB protein, Ralstonia solanacearum; D052899:Pore Forming Cytotoxic Proteins; C111749:pseudomonas exoprotein A protein, Pseudomonas aeruginosa; C111504:ExoY protein, bacteria; D005964:Glucosyltransferases; D011494:Protein Kinases; D000071677:Histidine Kinase