Infections are very rare, and when they *do* occur, they usually take many months to develop. In a 'hostile' environment - under pressure, acidic, alcoholic and hoppy - I find it extremely plausible that it was contamination that caused an infection and blew up the bottle. The entire batch may well have been infected, and you just drank them all before any noticeable off flavours developed. Or, maybe the single bottle was contaminated by some crud of some sort.
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