Microbial keratitis is a severe and often blindness-inducing pathology which represents today the first reason for long-term hospitalization (more than 5 days) in ophthalmology. Its diagnosis is clinical and leads to an immediate hospitalization in the presence of serious criteria (Mackie classification). The entire process of microbiological diagnosis requires several days before etiological confirmation and therefore delays the initiation of targeted therapy.

Recently, new PCR systems allowing the detection of 18 to 27 pathogens in 75 minutes have been developed. Their use could thus be transposed to ophthalmology by adapting the microbiological diagnostic technique to samples currently taken by swabbing the cornea.

The investigators will compare their diagnosis performance versus conventional methods on patients who suffered for a microbial keratitis with severity criteria.

46 patients enrolled for severe infectious keratitis will be recruited in the department of Ophthalmology, Robert Debré Hospital, Reims, France. The study will be composed by 2 groups. The first, also called "before group" will contain 23 patients who were anteriorly hospitalized for a severe infectious keratitis in our hospital unit. They received standard microbiological diagnosis methods: Direct microscopic examination with Gram stain, bacterial and fungal cultures, viral and amoebic polymerase chain reaction [PCR]).

The second, also called "after group" will enroll patients who suffer for a severe infectious keratitis (prospective group). Each patient will benefit a complete ophthalmologic examination, corneal scrapping and swabbing for standard microbiological diagnosis methods along with another corneal swabbing sample for the use of two different FilmArray® PCR systems identified as "ME" for Meningitis-Encephalitis and "BCID" for Blood Culture Identification.

The investigators hypothesize that the use of rapid multiplex PCR tests for the microbiological diagnosis of severe corneal infections could in the future prove to be more efficient than the current diagnostic strategy, on the one hand, by shortening the time to identify the pathogen and therefore to implement a targeted treatment, and on the other hand, by systematically searching for a large number of pathogens well beyond those targeted today. In addition, the benefits of this technique applied to ophthalmology could improve the long-term visual prognosis, reduce the length of hospitalization and therefore the diagnostic and management costs of these patients.

Inclusion criteria:

• Over 18 years old
• With social security affiliation
• Willing to participate this study
• Hospitalized in our department for severe infectious keratitis

Non-inclusion criteria:

• Any prior (48 hours) or concomitant treatment with local or systemic antibiotherapy at time of corneal scrapping and swabbing
• Patient not covered by the French Health Insurance
• Unable to give informed consent

Adult patients treated for a severe corneal abscess according to the Mackie classification (requiring hospitalization) at the Reims University Hospital between 05/01/2022 and 04/30/2023 ("before" phase) and between 01/ 05/2023 and 04/30/2024 ("after" phase).