Check the AC evaporator coils as the condensation on it allows the bacteria to remain damp, which can cause smells.By cleaning the coil and AC filter ,it may remove the bad smell.
But this problem is recurring one. After sometime again it will resurface.
All you have to do is run the blower with A/C switched off for 5 mins before you turn off your engine. THis will eliminate the moisture in blower system and will not smell so. I follow this in my cars, if dont i too get some foul smell.
This is all due if we are in humid climate near to coast