Proteus mirabilisとColletotrichum fructicolaの混合感染による角膜炎の1例

A case of keratitis by mixed infection of Proteus mirabilis and Colletotrichum fructicola

要約　目的：細菌と真菌の混合感染による角膜炎は決して珍しくないが，両者が分離同定され確定診断されることは稀である。今回筆者らは，Proteus mirabilisとColletotrichum fructicolaを同定することができた混合感染による角膜炎を経験したので報告する。

症例：70歳，男性。2019年10月下旬，米の荷受けをしていた際に，右眼にゴミが入ったような感じがあった。2〜3日後より眼痛を生じたが，手持ちの点眼で様子をみていた。11月上旬，視力低下を伴ってきたため，近医を受診した。右眼に角膜潰瘍と前房蓄膿を認めたため，当科に紹介となった。細菌性角膜炎としてレボフロキサシン点眼，セフメノキシム点眼，セファゾリン点滴にて加療を開始し，前房蓄膿が減少した。しかし，塗抹検鏡にて，グラム陰性桿菌とともに糸状菌も認めたため，ピマリシン点眼を追加して加療した。後日，培養にて細菌と真菌が分離され，細菌はProteus mirabilis，真菌は帝京大学に送付し，PCRダイレクトシークエンスによる分子生物学的解析を行うことで，Colletotrichum fructicolaと同定された。ピマリシン点眼で効果を認め，約1か月半で瘢痕化を得ることができた。

結論：植物や作物による外傷が原因の感染性角膜炎の場合，細菌と真菌の混合感染を考慮する必要がある。今回のように，特に真菌は培養検査で検出されるまでに時間がかかるため，塗抹検鏡を行うことで，その合併をより早く知ることができる。なお，筆者らの知る限り，Colletotrichum fructicolaによる真菌性角膜炎の報告は初めてのものである。

Abstract　Purpose：Keratitis caused by combined infection of bacteria and fungus is common, however, it is difficult to identify both of them. We report a case of keratitis by mixed infection of Proteus mirabilis and Colletotrichum fructicola.

Case：The patient was a 70-year-old man, who felt the entrance of a foreign body in the right eye in the course of cargo handling of rice in late October 2019. After 2-3 days, he felt eye pain in the right eye；however, he used steroid and anti-glaucoma eye drops at home without hospital visit. In early November 2019, he visited a local ophthalmic clinic because of decreased vision, was referred to Tottori University Hospital, and diagnosed withm hypopyon ulcer in the right eye. At the first examination, corneal scrapings were provided to microscopic examination of smear, laboratory culture, and real-time PCR（bacteria, fungi）, and antibiotics was started. Although hypopyon had been reduced after the start of antibiotic therapy, pimaricin eye drops was added at 4 days after hospitalization because of fungal elements observed in smear. Afterward, the right eye had been gradually improved and scarred after one and half months. The results of laboratory culture were Proteus mirabilis and fungus, which was identified as Colletotrichum fructicola by PCR direct sequence methods.

Conclusions：We should consider both bacteria and fungi as causative agents, in case of injury by plants or crops. Microscopic examination of smear is important to recognize the existence of mixed infection earlier than culture. To our best knowledge, this is the first report on keratitis caused by Colletotrichum fructicola.