Comparison of virulence factors genes between exoU and exoS Pseudomonas aeruginosa in microbial keratitis
Tanzina Akter1,2, Fiona Stapleton3, Jake Ireland4
1School of Optometry and Vision Science, Faculty of Medicine and Health, University of New South Wales (UNSW), Sydney, NSW, 2052, Australia. t.akter@unsw.edu.au.
Purpose:
This study aimed to investigate differences in virulence factors between exoU and exoS lineages of Pseudomonas aeruginosa from microbial keratitis (MK).
Method:
Initially, the whole genome sequence (WGS) data of 20 exoU and 19 exoS P. aeruginosa keratitis isolates from India and Australia retrieved from NCBI genome database was assessed for the presence of different virulence genes using the Virulence Factors Database (VFDB). To confirm the VFDB results, a separate set of keratitis isolates consisting of 148 P. aeruginosa (36 from India and 112 from Australia) were screened by PCR for the presence of exoU, exoS, and the virulence genes found to be significantly different in the VFDB analysis. Flagellar length was measured by transmission electron microscopy (TEM) and phospholipase D (PLD) activity was determined by Amplex Red Phospholipase D Assay Kit.
Results:
From 327 virulence-associated genes, the VFDB analysis identified significant differences in four virulence factor genes pilA, pldA, algP, and flaG between the exoU and exoS groups (all p < 0.05).When combining PCR and VFDB data from 187 keratitis isolates, pldA (83.6% vs. 31.8%, p < 0.01) and flaG (80% vs. 55.3%, p < 0.01) showed significantly higher prevalence in the exoU than the exoS. Similar trends were observed among Australian isolates while within the Indian isolates, only pldA (77.3% vs. 35.3%, p < 0.01) differed significantly. No association was found between flagellar length and flaG, but PLD activity correlated with the presence of the pldA.
Conclusion:
The pldA and flaG genes might be relevant virulence factors for the exoU group, potentially associated with the severity of MK.
