Does commercial sour cream still contain live bacteria?
It's hard to get a straight answer online, unfortunately, as most sour cream manufacturers don't mention either way.  Daisy brand, for example (one of the mass-market brands that is relatively unprocessed) doesn't mention it on their website, nor do they on their containers, though some people have said they do contain live active cultures - but nothing reliable that I see indicates that.  Breakstone's mentions that their cottage cheese has prebiotics, but nothing about sour cream, leading me to think they probably don't.

A few brands pasteurize and then add back in the L. Acidophilus and Bifidus Regularis (or similar) cultures afterwards, presumably to improve taste as they continue to break down the lactose (similar to how some mass-market yogurts do so); for example, Organic Valley mentions on their website:


  Our sour cream is a cultured blend of nutrient-packed organic cream and skim milk. When the sour cream is pasteurized and homogenized, active cultures acidophilus and bifidus are added to boost the tangy flavor and create a consistently dense cream. The active cultures also serve as probiotics to improve the microbial balance of your digestive tract. 


If you're looking for a brand that specifically does contain live active cultures, you should look for a mention on the label.  Any brand that does not mention it on the label may or may not contain them.  The indication of live and active cultures is not mandatory, as far as I can tell; the National Yogurt Association has a voluntary compliance process involving a seal that indicates live and active cultures, for example, but it is strictly voluntary.

However, searching for a brand that does not contain live active cultures, your best bet would be to contact the manufacturers directly.  I don't think there's a reliable way to prove they don't contain them.  Fat-free sour cream is also unlikely to contain live and active cultures (as it's not really sour cream, it's a flavored gelatin product more or less).  Alternatively, you can cook the sour cream yourself (or only use it in cooked applications) to ensure the bacteria are not live, though in this case you should talk to your doctor to find out in what applications this may be safe.