Nowadays, bacterial resistance to the different antibiotics is a major public health problem [1-4]. Recent outbreaks, like the one found in Germany for E. coli O104 [5,6] as well as the emergence of multidrug resistant organisms, such as gram-negative Enterobacteriaceae associated to the New Delhi metallo β-lactamase [7-9] evidence this problem [4,10-12], that not only has public health implications, but also at an economic and social level, threatening global safety [13,14]. The latest studies reported also the significant financial burden on health care-associated infections (HAIs) in the USA[15,16]. In the UK, approximately 9% of hospitalized patients acquire an infection after post-admission to hospital which increases the budget in the health care system [15,17].