the colonies growing on blood agar, illustrated in the top image, are small, convex, entire, smooth, and light-yellow pigmented. gram stain revealed short gram-positive bacilli arranged in loose clusters. the key to the identification is the positive lecithinase activity on egg yolk agar (lower image). catalase and oxidase reactions were found to be positive and acid was produced from most carbohydrates. this is a soil organism occasionally causing nosocomial infections related to exposure to contaminated water. from these observations, select the presumptive identification of this isolate.