Comparison of clinical characteristics and antibiotic susceptibility between Pseudomonas aeruginosa and P. putida keratitis at a tertiary referral center: a retrospective study

Background: To compare clinical characteristics and antibiotic susceptibilities in patients with Pseudomonas aeruginosa (PA) and P. putida (PP) keratitis at a tertiary referral center in South Korea. Methods: Forty-nine cases of inpatients with culture-proven PA and PP keratitis were reviewed retrospectively between January 1998 and December 2017. We excluded cases of polymicrobial infection. Epidemiology, predisposing factors, clinical characteristics, antibiotic susceptibilities, and treatment outcomes were compared between the PA and PP groups. The risk factors for poor clinical outcome were evaluated on the basis of the total cohort and analyzed using multivariate logistic regression. Results: A total of 33 eyes with PA keratitis and 16 eyes with PP keratitis were included. The mean age was 47.0 years in the PA group and 593 years in the PP group (p = 0.060). Differences were observed between the PA and PP groups in hypopyon (45.5% vs 63%, p = 0.006) and symptom duration (43 vs 9.5 days, p = 0.022). The most common predisposing factor for PA was wearing contact lenses (36.4%) and that for PP was corneal trauma (62.5%). No significant differences were observed in sex, previous topical steroid use, systemic disease, or duration of hospitalization between the two groups. The PA and PP groups both demonstrated good efficacy of colistin (both 100%), tobramycin (93.3%, 100%), ceftazidime (93.9%, 87.5%), and ciprofloxacin (96.6%, 87.5%). Imipenem (100% vs 813%, p = 0.030), piperacillin (96.6% vs 75%, p = 0.047), and ticarcillin (85% vs 0%, p < 0.001) showed significantly lower efficacy in the PP group than in the PA group. A poor clinical outcome was observed in 312% of the PA group and 37.5% of the PP group (p = 0.665). The risk factors for poor clinical outcome were previous ocular surface disease (odds ratio 10.79, p= 0.012) and hypopyon (odds ratio 9.02, p = 0.024). Conclusions: The PA group was more closely associated with younger age, wearing contact lenses, shorter symptom duration, and hypopyon, whereas the PP group was more closely associated with elderly age, corneal trauma, and decreased efficacy of the beta-lactams. Clinical outcomes were not significantly different between the two groups. Previous ocular surface disease and hypopyon were the risk factors for poor clinical outcome.