Impact of Metabolic Diversity on Pseudomonas aeruginosa T3SS Phenotype

Abstract

Purpose : Pseudomonas aeruginosa cause necrotizing keratitis in patients with a dysbiotic ocular surface due to contact lens wear, ocular surface disease and chronic use of topical medications.. Metabolism plays an important role in the disease pathology and expression of potent toxins and proteases at the ocular surface. We hypothesize that differences in metabolic diversity impacts T3SS exoenzymes phenotype expression.

Methods : One hundred Pseudomonas aeruginosa isolates recovered from patients presenting with keratitis during a 24-month period (2021-2022 were recovered and the type 3 secretion system profile documented using a multiplex PCR assay. Growth rates and biochemical fingerprint profiles were determined using the Vitek 2 system. Pigment production was determined using a combination of nutrient, P and F agars.

Results : ExoU and ExoS cellular toxins constituted 96% of the type 3 effectors and were distributed equally (48% each) among this group of keratitis isolates. The remaining 4% included ExoTU 2, 2% and one each of ExoYS and ExoTS. Pigment production was evaluated for 57 isolates. 98.2% of isolates produced pyocyanin, 96.5% produced pyoverdine and 94% secreted both. Pigment production was highest in isolates with the cytotoxic- ExoU phenotype 62.2% (30/48) vs invasive phenotype ExoS-52.2% (25/48). Metabolic diversity index 59.1% vs 57.4% and growth rate-time to identification (5.71 hours vs 4.82 hours) were unique for ExoU vs ExoS respectively. No significant difference (100% each) in citrate or succinate utilization. Amino acids: histidine and tyrosine utilization for ExoU vs ExoS phenotypes were 52.3%/89.7% vs 38.2%/85.3% respectively.

Conclusions : Pseudomonas aeruginosa Type 3 secretion effectors are associated with distinct metabolic profiles and virulence factors. Our data is supportive of our hypothesis and has important implications for understanding and managing these recalcitrant infections.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.