Mutant prevention concentration (MPC) of ciprofloxacin against Salmonella enterica of epidemic and poultry origin.

Salmonella isolates resistant or with reduced susceptibility to quinolones increased in recent years. The mutant prevention concentration (MPC) is a new alternative that can prevent the selection and multiplication of resistant Salmonella spp. strains. The MPC of ciprofloxacin (CipMPC) was evaluated for 312 Salmonella enterica strains of epidemic and poultry origin susceptible and resistant to nalidixic acid (NAL). The CipMPC for NAL-susceptible strains were in the range from 0.002 to 4 μg/ml and for NAL-resistant strains, it ranged from 0.004 to 16 μg/ml. The average MPC/MIC ratio for NAL-resistant strains was higher than NAL susceptible. S. Enteritidis showed the highest CipMPC and the highest MPC/MIC ratio also for NAL-resistant strains and with mutations in gyrA. Serovar Corvallis, a NAL-resistant strain without mutations, and of poultry origin showed the highest CipMPC value. The lowest value was observed for epidemic NAL-susceptible strains serovars Typhimurium and London. The average MPC/MIC ratio for strains with mutations in Aspartate 87 was higher than that mutated in Serine 83. The results show the importance of MPC in determining the correct dosage of Cip for treatment of Salmonella spp.