Comparing the minimum inhibitory and mutant prevention concentrations of selected antibiotics against animal isolates of Pasteurella multocida and Salmonella typhimurium

Abstract

Historically, the use of antibiotics was not well regulated in veterinary medicine. The emergence of antibiotic resistance (ABR) in pathogenic bacteria in human and veterinary medicine has driven the need for greater antibiotic stewardship. The preservation of certain antibiotic classes for use exclusively in humans, especially in cases of multidrug resistance, has highlighted the need for veterinarians to reduce its use and redefine dosage regimens of antibiotics to ensure efficacy and guard against the development of ABR pathogens. The minimum inhibitory concentration (MIC), the lowest concentration of an antibiotic drug that will prevent the growth of a bacterium, is recognised as a method to assist in antibiotic dosage determination. Minimum inhibitory concentrations sometimes fail to deal with first-step mutants in bacterial populations; therefore dosing regimens based solely on MIC can lead to the development of ABR. The mutant prevention concentration (MPC) is the minimum inhibitory antibiotic concentration of the most resistant first-step mutant. Mutant prevention concentration determination as a complementary and sometimes preferable alternative to MIC determination for veterinarians when managing bacterial pathogens. The results of this study focused on livestock pathogens and antibiotics used to treat them, which had a MIC value of 0.25 µg/mL for enrofloxacin against all 27 isolates of Salmonella typhimurium. The MPC values were 0.50 µg/mL, with the exception of five isolates that had MPC values of 4.00 µg/mL. The MPC test yielded 65.52% (18 isolates) Salmonella isolates with florfenicol MICs in the sensitive range, while 11 isolates were in the resistant range. Seventeen isolates (58.62%) of Pasteurella multocida had MIC values in the susceptible range and 41.38% (12 isolates) had an intermediate MIC value. Mutant prevention concentration determinations as done in this study is effective for the antibiotic treatment of bacterial infections and minimising the development of resistance. The MPC method can be used to better control to prevent the development of antibiotic drug resistance used in animals.

Comparative pharmacokinetics of florfenicol in heifers after intramuscular and subcutaneous administration

“…A number of studies of bacterial isolates from cattle have demonstrated that many types of bacteria are sensitive to florfenicol, in particular, prevalent bacteria that cause respiratory disease in cattle (BRD), namely Mannheimia haemolytica, Pasteurella multocida, Histophilus somni (de Jong et al, 2014;EMA, 2017;Kehrenberg et al, 2004;Plumb, 2004;The United States Pharmacopeial Convention, 2007;Wentzel, 2012), as well as other pathogens such as Bacteroides melaninogenicus and Fusobacterium necrophorum (The United States Pharmacopeial Convention, 2007).…”

Mutant Prevention Concentration, Frequency of Spontaneous Mutant Selection, and Mutant Selection Window—a New Approach to the In Vitro Determination of the Antimicrobial Potency of Compounds

“…Currently, required inocula are prepared via a one-step concentration of the liquid culture. However, they rarely exceed a density of 10 11 CFU/mL ( 9 , 36 , 43 ), usually reaching 10 10 CFU/mL ( 29 , 39 , 44 to 48 ) or 10 9 CFU/mL ( 49 , 50 ). The lower the inoculum density, the more plates are needed.…”

Enrofloxacin—The Ruthless Killer of Eukaryotic Cells or the Last Hope in the Fight against Bacterial Infections?

“…Escherichia coli strains isolated from the bovine uterus showed MIC values ≤ 0.25 µg/mL, which was analogous to the results obtained by Liu et al for E. coli strains causing thigh infections in mice [ 58 , 59 ]. For Salmonella strains, the MIC value varied between 0.06 and 0.25 µg/mL [ 60 , 61 ]. Significantly higher MIC values were obtained for Pseudomonas aeruginosa strains, ranging between 1 and 4 mg/mL [ 60 , 62 ].…”