FLUORESCENT GRAM STAIN IN THE MICROBIOLOGIC DIAGNOSIS OF INFECTIOUS KERATITIS AND ENDOPHTHALMITIS

Purpose. To verify the sensitivity of a recently described technique o f fluorescent Gram stain (FGS) and evaluate its role in direct microsc opic examination of clinical ocular samples. Methods. In the first par t of the study, culture suspensions of 10 bacterial isolates were stai ned, using FGS and conventional Gram stain (CGS), and were assessed fo r morphology and Gram sign. In the second part, 39 corneal scrapings a nd 18 vitreous biopsy materials were stained and observed by both meth ods. Results. Gram reaction and morphology of the bacteria, using CGS and FGS, were compared against culture. In both parts of the study, th e sensitivity of CGS was significantly higher than FGS in the detectio n of Gram positive reaction (p = 0.01, 0.02). The specificities and pr edictive values of CGS and FGS were comparable in the evaluation of cl inical samples. The bacterial morphology was demonstrated better (p = 0.01) with CGS. Significant quenching of fluorescence and change in Gr am reaction with time were noted in FGS. Conclusions. The low sensitiv ity, quenching of fluorescence and change in Gram reaction presently p reclude the usage of FGS as a diagnostic tool in ocular infections.