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.
Highlights
Dolosigranulum 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
Additional microbiological analyses including fungal culture and the molecular detection of amoeba, bacteria, mycobacteria and herpes simplex virus were negative. In these cases, D. pigrum was firmly identified by PCRsequencing of the bacterial 16S rDNA since negative controls remained negative and no other D. pigrum strain was isolated or PCR-amplified in the laboratory during the previous weeks while it is well established that the universal 16S rRNA gene-based detection of bacteria may lack sensitivity compared to culture for antibiotic-free specimens, as illustrated in two cases [9]
D. pigrum has been shown to be in-vitro susceptible to antibiotics used in these patients, including beta-lactams, fluoroquinolones and vancomycin [8]
Summary
Dolosigranulum 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. Case 1 A 78-year-old female patient presented to our ophthalmology department in September 2007 for a painful right eye. As herpetic keratitis was suspected, the patient was treated with 3 g/day oral valacyclovir but the corneal ulcer progressively increased in depth.
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