Dolosigranulum pigrum keratitis: a three-case series

Abstract

BackgroundDolosigranulum pigrum is a commensal inhabitant of the upper respiratory tract suspected to be responsible for ocular infections but no well-described case of D. pigrum corneal infection has been reported. Herein culture and PCR-sequencing-based investigations of corneal scraping specimens confirmed D. pigrum keratitis in three patients.Case presentationThree elderly patients presented with unilateral keratitis. None was a corneal-contact lens wearer, one had previous cataract surgery and another suffered rheumatoid arthritis sicca syndrome. Culturing the corneal scraping specimen was positive for two cases and PCR-sequencing of bacterial 16S rDNA in the presence of negative controls identified D. pigrum in three cases. The two D. pigrum isolates were in-vitro susceptible to penicillin G, amoxicillin, doxycycline, rifampicin and gentamicin. In all cases, surgical treatment of corneal thinning was necessary, but corneal perforation occurred in two cases despite intensive antimicrobial treatment with ticarcillin, gentamicin and vancomycin or levofloxacin eye drops leading to enucleation in one case.ConclusionsD. pigrum is the likely cause of corneal infection in three patients, with effective antibiotic treatment in two patients.

Dolosigranulum pigrum: Predicting Severity of Infection

“…Our specimen was sensitive to beta-lactams, cephalosporin, fluoroquinolones, and vancomycin. However, it was intermediately resistant to erythromycin, which largely matched the CDC data [4,[6][7][8][9]. The CDC data showed that 52% of their isolates were resistant to erythromycin, with most of those resistant samples appearing in corneal collections [6].…”

“…In comparison to prior reports, our patient followed patterns that predicted a favorable outcome [2][3][4][5][6][7][8][9][11][12][13][14][15]. He was a 61-year-old male with no chronic immunosuppressive conditions or medications apart from the end-stage renal disease on dialysis due to type II diabetes.…”

“…Many of these patients were either less than 2 years of age or older than 65 years of age. In a seventh report, a 71-year-old female, an 85-year-old male, and a 78-year-old female all had keratitis with corneal specimens positive for D. pigrum [4]. This further suggests that D. pigrum is an emerging pathogen that particularly targets the immunocompromised and the elderly.…”

“…While this increased incidence could be due to increased usage of RNA gene sequencing in clinical laboratories, it also could mark the emergence of an opportunistic infection particularly in immunocompromised patients [2]. Otherwise, it has been suggested that D. pigrum remains a commensal organism [2][3][4][5].…”

Phlyctenular Keratoconjunctivitis Associated withDolosigranulum pigrum

“…The organism has emerged as a potential pathogen in humans and has been identified in a broad spectrum of diseases, including nosocomial pneumonia and 9 and cystic fibrosis pneumonia. 10 Ocular involvement of D. pigrum has been reported in cases of a neurotrophic cornea, 11 blepharitis, 12 keratitis, 13 and bacterial conjunctivitis.…”