Definitely infected imo. Would do like arover said and do a full sanitize/replace on equipment. Take all of your bottling stuff (lines, wand, etc) and soak in sanitizer for a good 30-40 minutes, and also check your bottling bucket for scratches where bacteria might call home (if you use the standard plastic bucket). Also revisit your bottling process and see if there's anywhere to improve on sanitization. The idea I go with is anything that will come into contact with the beer needs to be sanitized for at least 4 minutes (7-8 to be anally safe for equipment, 10 for bottles, and caps soak until they're used).
Any bottles like that one need to be gotten rid of, and keep an eye on the rest for possible bombs. Store them in a safe spot away from kids/pets, and keep them over a sink when you open them in case they decide to go kablooey.