This follows an e. coli outbreak in bagged pre-cut lettuce not too long ago. Long story short, don't eat vegetables that aren't out loose and fresh. And really anybody only ought to eat produce grown in a first world country--preferably locally. I don't want to disparge other countries, but the US and the EU and UK all have high standards of cleanliness for their agriculture and produce (like it's illegal to use human waste as a fertilizer--which, I believe, is the source of e.coli on vegetables).
Anybody who eats bagged lettuces and spinaches frequently or in the recent past might ought to get checked for e.coli and/or parasites; that may be the cause of your IBS.