2022 Volume 71 Issue 3 Pages 554-559
Moraxella nonliquefaciens is a commensal organism in the human upper respiratory tract. It is the causative organism of pediatric bronchitis and pediatric sinusitis, and it is rarely detected in corneal swabs. Here, we report a case of corneal ulcer caused by M. nonliquefaciens. A man in his seventies presented with left eye pain and was diagnosed as having an infectious corneal ulcer, anterior chamber abscess, and endophthalmitis with thinning of the left corneal ring. Gram staining of the corneal swab revealed large gram-negative bacilli arranged in pairs with square ends. Although small, smooth, white, nonhemolytic colonies developed on TSA II 5% sheep blood agar in 24 h, no growth was observed on BTB lactose-containing agar. The organism tested positive for catalase and oxidase. However, the organism was not correctly identified on the basis of a differential diagnosis of species by conventional biochemical analysis. The organism was subsequently identified to be M. nonliquefaciens using VITEK MS mass spectrometry (99%), and 16S rRNA gene analysis showed 99.71% compatibility with M. nonliquefaciens. Drug susceptibility test results of the organism revealed resistance to macrolide antimicrobials. The patient’s corneal ulcer improved with the administration of quinolone antimicrobials, cefcapene-pivoxil, and other antimicrobials. Although mass spectrometry is a useful method for identifying M. nonliquefaciens, it is important to speculate the possibility of M. nonliquefaciens on the basis of the results of conventional methods such as morphologic characteristics, results of culture tests and catalase and oxidase tests of laboratory materials, and reports of doctors-in-charge.
