Rizvi M, Fatima N, Rashid M, Shukla I, Malik A, Usman A, Siddiqui S (2009) Extended spectrum AmpC and metallo-beta-lactamases in Serratia and Citrobacter spp. in a disc approximation assay. J Infect Dev Ctries 3:285–294. doi: 10.3855/jidc.126