Mezlocillin is known to be stable against hydrolysis by a variety of beta-lactamases, including penicillinases and cephalosporinases, and is used to treat infections caused by susceptible strains of H. influenzae, Klebsiella species, Pseudomonas species, Proteus mirabilis, E. coli, Enterobacter species, Streptococcus faecelis, Peptococcus species, and Peptostreptococcus species [50]. The gene discussed is LACTB; the disease is infection.