Pseudomonas aeruginosa with lasI quorum-sensing deficiency during corneal infection.
OBJECTIVE
To understand the importance of Pseudomonas aeruginosa quorum-sensing systems in the development of corneal infection, the genotypic characteristics and pathogenesis of seven ocular isolates with low-protease and acyl homoserine lactone (AHL) activity and quorum-sensing mutants of PAO1 deficient in lasI, lasR, or rhlR were investigated in the study.


METHODS
The possession of the quorum-sensing genes lasI, lasR, rhlI, rhlR, and the quorum-sensing controlled genes lasB, aprA, and rhlAB in the clinical isolates were determined by polymerase chain reaction and Southern blot hybridization. Elastinolytic activity, controlled by the las system, was assayed using elastin Congo red and rhamnolipid production controlled by the rhl system was assessed using agar plates containing methylene blue/cetyltrimethyl ammonium bromide. Induction of keratitis was examined in a scarified inbred BALB/c mouse model.


RESULTS
The clinical isolates Paer1 and -3 were lasI and lasR negative, and the isolates Paer2 and -4 were rhlR and rhlAB negative. The isolates Paer17, Paer26, 6294 and 6206 possessed all the genes examined. There was no rhamnolipid production in clinical isolates Paer2 and -4. The isolates Paer1 and -3 were virtually avirulent in the scarified mouse corneas. Using isogenic PAO1 mutants, strain lasI showed a markedly reduced virulence in the corneal infection model. The remainder of the clinical isolates and the lasR or rhlR mutant strains caused severe keratitis.


CONCLUSIONS
These results indicate that quorum-sensing deficiency may occur naturally in clinical isolates, and the possession of lasI and hence a functional Las quorum-sensing system may be important in development of corneal infection.
Zhu
Hua
H
Cooperative Research Centre for Eye Research and Technology, University of New South Wales, Sydney, Australia.
Bandara
Rani
R
Conibear
Tim C R
TC
Thuruthyil
Sophy J
SJ
Rice
Scott A
SA
Kjelleberg
Staffan
S
Givskov
Michael
M
Willcox
Mark D P
MD
D000818:Animals; D001426:Bacterial Proteins / Q000502:physiology*; D015373:Bacterial Typing Techniques; D015139:Blotting, Southern; D003315:Cornea / Q000382:microbiology; D003320:Corneal Ulcer / Q000382:microbiology*; D004268:DNA-Binding Proteins / Q000502:physiology; D015818:Eye Infections, Bacterial / Q000382:microbiology*; D005260:Female; D051379:Mice; D008807:Mice, Inbred BALB C; D010641:Phenotype; D016133:Polymerase Chain Reaction; D011552:Pseudomonas Infections / Q000382:microbiology*; D011550:Pseudomonas aeruginosa / Q000145:classification / Q000235:genetics / Q000472:pathogenicity*; D015534:Trans-Activators / Q000502:physiology; D014774:Virulence
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C081237:LasI protein, Pseudomonas aeruginosa; C080365:LasR protein, Pseudomonas aeruginosa; D015534:Trans-Activators