To investigate the contribution of microbial analysis in the diagnosis and management of severe microbial keratitis.This is a monocentric retrospective study at the University Hospital of Reims from January 2012 to December 2014. Corneal scrapings with infectious keratitis were subjected to routine bacterial and fungal culture. PCR was also performed to detect various viral DNA (VZV, CMV, EBV, HSV 12, adenovirus) and Acanthamoeba sp. DNA. All contact lens cases were analyzed if available.One hundred and six patients were hospitalized, including 30 contact lens wearers (28.3%). Sixty-four bacterial cultures were positive (68%). Twenty-five different bacterial species were identified with a majority of gram-positive bacteria (67.92%). Among contact lens wearers, the initial VA was better than non-wearers (P=0.0004) and 37% of bacteria identified (a plurality) were gram positive. Of 11 contact lens case analyzed, in only one case (3.3%) did the result correlate with the corneal culture. Only 9 samples from the 323 viral DNA extractions and real time PCR were positive (2.8%); 7 were HSV1. No prior antiviral therapy had been started. Fungal culture was positive in 2 of the 97 corneal samples taken and 63.6% of the contact lens cases (7/11 cases). Only one of the 40 Acanthamoeba sp. PCR's was positive.The systematic performance of microbiological investigations is a good diagnostic approach given the polymorphism of clinical presentations of corneal ulcers, which can sometimes be extremely misleading. Culture of contact lens cases appears ineffective for the detection and determination of the causative microorganism. The high incidence of Staphylococcus in bacterial keratitis and the prevalence of infections with gram-positive bacteria in contact lens wearers were noted.
