Hmm... I think that eating lettuce, and vegetables in general, is healthy. The title is just sensationalist, and the article scares people with the possibility that bacteria lives on the plants. If we would take the article seriously, living in cities or using our keyboard also make us sick: the air in cities is full of dog poo dust and the associated bacteria, and keyboards are also full of bacteria:
http://www.medicalnewstoday.com/articles/233104.php ,
http://news.bbc.co.uk/2/hi/7377002.stm .