The cif Virulence Factor Gene Is Present in Isolates From Patients With Pseudomonas aeruginosa Keratitis
Christopher D Bahl1, Jessica D St Laurent, R Siva Ganesa Karthikeyan
1*Department of Biochemistry & Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH. Dr Bahl is now with the Department of Biochemistry, University of Washington, Seattle, WA, and Dr St. Laurent is now with the Department of Obstetrics and Gynecology, Brigham, and Women's Hospital, Boston, MA; †Department of Ocular Microbiology, Dr G. Venkatasamy Eye Research Institute, Aravind Medical Research Foundation, Madurai, India; ‡Department of Surgery (Ophthalmology), Geisel School of Medicine at Dartmouth, Hanover, NH; and §Department of Microbiology & Immunology, Geisel School of Medicine at Dartmouth, Hanover, NH.
Purpose:
To determine whether the cif gene is present in pathogenic Pseudomonas aeruginosa isolates from patients with bacterial keratitis at Aravind Eye Hospital, a referral eye care center in southern India, and from corresponding environmental isolates.
Methods:
Polymerase chain reaction amplification was performed on strains of P. aeruginosa isolated from ocular infections and environmental soil samples were collected from the area surrounding Aravind Eye Hospital. DNA sequencing of 16S ribosomal DNA amplicons was performed to verify strain identity.
Results:
We determined that 45 of 48 patient isolates carry a genomic copy of cif. Analysis of a catalog of environmental strains previously isolated from the surrounding area revealed that only 4 of 10 P. aeruginosa strains and 1 of 14 strains of related species carry the cif gene.
Conclusions:
This is the first study to show that P. aeruginosa strains with ocular pathogenicity carry the cif gene and that the presence of this gene may be enriched over its prevalence in the environment. Taken together, these results suggest a potential role for Cif in acute bacterial keratitis.
Insights
The Pseudomonas aeruginosa cif gene is frequently found in patient eye infection isolates but rarely in environmental samples. This suggests a potential role for the cif gene in bacterial keratitis.
Area of Science:
- Ophthalmology
- Microbiology
- Genetics
Background:
- Pseudomonas aeruginosa is a common cause of bacterial keratitis.
- The role of specific genes, such as cif, in P. aeruginosa pathogenicity is not fully understood.
Purpose of the Study:
- To investigate the presence of the cif gene in pathogenic P. aeruginosa isolates from bacterial keratitis patients.
- To compare the prevalence of the cif gene in patient isolates versus environmental isolates.
Main Methods:
- Polymerase chain reaction (PCR) was used to detect the cif gene in P. aeruginosa strains.
- Isolates were obtained from bacterial keratitis patients and surrounding environmental soil samples.
- DNA sequencing of 16S ribosomal DNA confirmed strain identity.
Main Results:
- The cif gene was detected in 45 out of 48 (93.75%) patient isolates.
- Only 4 out of 10 (40%) environmental P. aeruginosa strains carried the cif gene.
- One out of 14 (7.14%) related species environmental strains contained the cif gene.
Conclusions:
- This study is the first to demonstrate the presence of the cif gene in P. aeruginosa strains causing ocular infections.
- The cif gene appears to be significantly enriched in pathogenic ocular isolates compared to environmental strains.
- These findings suggest a potential role for the cif gene in the pathogenesis of acute bacterial keratitis.
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