Relevance of phenotype and resistotype of Pseudomonas aeruginosa infections in conjunctivitis-otitis syndrome

Abstract

Purpose : The conjunctivitis-otitis syndrome has been associated with Haemophilus influenzae and other common microorganisms of the conjunctiva and ear microbiota. Acute and chronic Pseudomonas aeruginosa are common in both, yet their relationship and possible contribution to this syndrome has not been investigated. We expect that the Type 3 secretion system (T3SS) exotoxin (Exo) profiles, metabolic diversity, and antibiotic susceptibilities will be the same in both ear and conjunctiva isolates.

Methods : Retrospective microbiology chart review was used to select P. aeruginosa isolates recovered from the ear and the conjunctiva of patients presenting with a diagnosis of conjunctivitis and or otitis media at our institution between 2015 and 2023. We compared age, sex, antibiotic resistant profiles, biochemical fingerprints, and Exo U and S profiles. Isolate identification, biochemical fingerprints, and susceptibility profiles were obtained using the Vitek II system. A multiplex PCR reaction was used to document the T3SS profile.

Results : Forty-six P. aeruginosa isolates were obtained from the ear and 64 from the conjunctiva during the 8-year period. The mean age of those with ear and conjunctival isolates was 35.3 ± 27.0 and 76.0 ± 19.6, respectively. Twenty-five (54.4%) ear and 29 (55.0%) conjunctival isolates were from males, while 21 (45.6%) ear and 29 (45.0%) conjunctival isolates were from females. Nonsusceptibility to ciprofloxacin, gentamicin, and levofloxacin was more common in ear (n = 11, 23.9%; n = 5, 10.9%; n = 10, 21.7%; respectively) than in conjunctival (n = 1, 1.59%; n = 1, 1.56 %, n = 2, .13 %; respectively) isolates (Figure 1). The invasive Exo S+ phenotype was more common in the ear (n = 21, 95.5%) than conjunctiva (n= 12, 60.0%), while the cytotoxic Exo U+ was less common for ear (n = 1, 4.5 %) than the conjunctiva (n = 8, 40.0%). More biochemical fingerprints were observed in the ear (n = 29) compared to the conjunctival (n = 18) isolates.

Conclusions : P. aeruginosa isolates from the ear and conjunctiva are distinct as seen by their antibiotic resistance, T3SS phenotype, metabolic signatures, and contrary to what we hypothesized. However, we were able to highlight the differences in these two niches.

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

 

Figure 1. Antibiotic susceptibility of ear and conjunctival Pseudomonas aeruginosa infections (2015 – 2023)