Assessment of Keratitis Severity Using Quantitative Image Analysis in an In Vivo Murine Model of Staphylococcus aureus Bacterial Keratitis.

Bacterial keratitis (BK) severity in murine models has traditionally been measured by subjective clinical grading or quantification of ocular bacterial burden. This investigation explores an objective and repeatable quantification of slit lamp photography (SLP) images to measure BK severity. BALB/c strain mice underwent three parallel scratches of the right cornea with subsequent inoculation of 107 Staphylococcus aureus cells. SLP imaging and clinical severity grading were performed at 48 hours post-infection. Stromal infiltrate (SI) area on SLP images were quantified. Bacterial burden was determined after enucleation and homogenization. Spearman rank correlations (rs) were used to estimate associations between SI area, clinical severity grades, and bacterial burden. BALB/c strain mice (n = 14) were evaluated with an average SI area of 0.92 mm2 (standard deviation, SD = 0.65) and average bacterial burden of 3.16 × 105 colony forming units per milliliter (CFU/mL) (SD = 8.3 × 105). Clinical severity grade positively correlated with SI area (rs = 0.59, p = 0.0276) and bacterial burden (rs = 0.66, p = 0.0106). There was a trend towards positive association between SI area and bacterial burden (rs = 0.51, p = 0.0543). SLP annotation of SI area is correlated with clinical severity and may provide an objective, quantitative, and repeatable assessment of BK disease severity. SLP annotation of SI area is a novel quantitative method to evaluate bacterial keratitis severity longitudinally in mouse models which may be a powerful tool to better understand BK pathogenesis and response to treatments.

在小鼠模型中，细菌性角膜炎（BK）的严重程度传统上是通过主观临床分级或眼部细菌负荷的量化来衡量的。本研究探索了一种对裂隙灯摄影（SLP）图像进行客观且可重复的量化方法来衡量BK的严重程度。 BALB/c品系小鼠的右眼角膜进行三次平行划痕，随后接种10⁷个金黄色葡萄球菌细胞。在感染后48小时进行SLP成像和临床严重程度分级。对SLP图像上的基质浸润（SI）面积进行量化。摘除眼球并匀浆后确定细菌负荷。采用斯皮尔曼等级相关（rs）来评估SI面积、临床严重程度分级和细菌负荷之间的关联。 对14只BALB/c品系小鼠进行评估，平均SI面积为0.92平方毫米（标准差，SD = 0.65），平均细菌负荷为每毫升3.16×10⁵个菌落形成单位（CFU/mL）（SD = 8.3×10⁵）。临床严重程度分级与SI面积呈正相关（rs = 0.59，p = 0.0276），与细菌负荷也呈正相关（rs = 0.66，p = 0.0106）。SI面积和细菌负荷之间呈正相关趋势（rs = 0.51，p = 0.0543）。 SI面积的SLP标注与临床严重程度相关，可能为BK疾病严重程度提供一种客观、定量且可重复的评估。 SI面积的SLP标注是一种在小鼠模型中纵向评估细菌性角膜炎严重程度的新型定量方法，它可能是更好地理解BK发病机制和治疗反应的有力工具。