Abstract
Purpose :
To investigate antibiotic susceptibility and genotypic profiles of Pseudomonas aeruginosa implicated in endophthalmitis, using both conventional microbiologic techniques and whole genome sequencing. Additionally, to report delafloxacin sensitivities of P. aeruginosa isolates from eyes with endophthalmitis.
Methods :
P. aeruginosa isolates of vitreous fluid culture-confirmed endophthalmitis were analyzed from nine eyes of nine patients seen at the Bascom Palmer Eye Institute. All antibiotic susceptibility profiles were identified using standard microbiologic protocols. Whole genome sequencing was performed on all isolates to determine the presence of virulence genes.
Results :
A relatively homogenous pattern of antibiotic susceptibility was identified amongst isolates. Each isolate was sensitive to ceftazidime, levofloxacin, ciprofloxacin, moxifloxacin, imipenem, gentamicin, amikacin, and tobramycin as determined by either an E test or VITEK 2 automated system. Of antibiotic sensitivities assessed with the E test, ciprofloxacin showed the lowest mean minimum inhibitory concentration across isolates (0.16 μg/ml), followed by ceftazidime (0.94 μg/ml), moxifloxacin (1.03 μg/ml), levofloxacin (1.03 μg/ml), and imipenem (1.49 μg/ml). Additionally, all isolates were susceptible to delafloxacin as determined by disk diffusion testing with an average area of inhibition of 23.6 mm (range 20-28 mm). Whole genome sequencing identified 181 unique virulence genes in this cohort. Isolates had an average of 136 virulence genes each (range 130-142). Adherence genes were the most common amongst isolates (69 total unique genes), followed by those implicated in the secretion system (49), and anti-phagocytosis (21). Seven of nine isolates harbored exoS, a gene known to yield a more invasive phenotype.
Conclusions :
In this in vitro study, P. aeruginosa showed the highest susceptibility to ciprofloxacin and ceftazidine, and demonstrated a similar genotypic profile across isolates. These data also suggest that delafloxacin may potentially be of clinical use for endophthalmitis due to P. aeruginosa.
This is a 2020 ARVO Annual Meeting abstract.