The PK/PD Integration and Resistance of Tilmicosin against Mycoplasma hyopneumoniae

Abstract

Mycoplasma hyopneumoniae is the major pathogen causing enzootic pneumonia in pigs. M. hyopneumoniae infection can lead to considerable economic losses in the pig-breeding industry. Here, this study established a first-order absorption, one-compartment model to study the relationship between the pharmacokinetics/pharmacodynamics (PK/PD) index of tilmicosin against M. hyopneumoniae in vitro. We simulated different drug concentrations of timicosin in the fluid lining the lung epithelia of pigs. The minimum inhibitory concentration (MIC) of tilmicosin against M. hyopneumoniae with an inoculum of 106 CFU/mL was 1.6 μg/mL using the microdilution method. Static time–kill curves showed that if the drug concentration >1 MIC, the antibacterial effect showed different degrees of inhibition. At 32 MIC, the amount of bacteria decreased by 3.16 log10 CFU/mL, thereby achieving a mycoplasmacidal effect. The M. hyopneumoniae count was reduced from 3.61 to 5.11 log10 CFU/mL upon incubation for 96 h in a dynamic model with a dose of 40–200 mg, thereby achieving mycoplasmacidal activity. The area under the concentration-time curve over 96 h divided by the MIC (AUC0–96 h/MIC) was the best-fit PK/PD parameters for predicting the antibacterial activity of tilmicosin against M. hyopneumoniae (R2 = 0.99), suggesting that tilmicosin had concentration-dependent activity. The estimated value for AUC0–96 h/MIC for 2log10 (CFU/mL) reduction and 3log10 (CFU/mL) reduction from baseline was 70.55 h and 96.72 h. Four M. hyopneumoniae strains (M1–M4) with reduced sensitivity to tilmicosin were isolated from the four dose groups. The susceptibility of these strains to tylosin, erythromycin and lincomycin was also reduced significantly. For sequencing analyses of 23S rRNA, an acquired A2058G transition in region V was found only in resistant M. hyopneumoniae strains (M3, M4). In conclusion, in an in vitro model, the effect of tilmicosin against M. hyopneumoniae was concentration-dependent and had a therapeutic effect. These results will help to design the optimal dosing regimen for tilmicosin in M. hyopneumoniae infection, and minimize the emergence of resistant bacteria.

Emergence and Mechanism of Resistance of Tulathromycin Against Mycoplasma hyopneumoniae in a PK/PD Model and the Fitness Costs of 23S rRNA Mutants

“…Interestingly we did not find mutations in L4 and L22 similar to the results of previous studies (20). The tilmicosin-resistant strain MTIL3 and tulathromycinresistant strain MTUL2 were the result of A2058G mutations and are common in macrolide resistance in M. genitalium (57), Mycoplasma bovis (58), Mycoplasma capricolum (59), M. gallisepticum (60), M. hyopneumoniae (19) and M. hominis (10). In the dynamic model, most of the drug-resistant bacteria isolated were A2058G mutants and only one strain possessed A2058T (MTUL1).…”

“…The M. hyopneumoniae standard strain ATCC 25934 was acquired from the Chinese Veterinary Microorganism Culture Collection Center (Beijing, China). Strains MTIL1∼3 MTIA1∼2 were isolated in previous study from in vitro selection using a dynamic model and were ATCC 25934 siblings (19,20). MTUL1∼2 were isolated in this study.…”

“…The MIC values of antibiotics against M. hyopneumoniae was determined using both the standard micro-dilution and agardilution methods as described previously (19,28). The standard method used M. hyopneumoniae cultures in the exponential growth phase period at 10 6 CFU/mL that was added at 100 µL per well in 96-well cell culture plates containing a series of equal volumes of test drug, growth control (medium only), end point control (blank medium) and sterile control (blank broth).…”

“…The primary mutations associated with the acquisition of resistance are A2058G and A2058C for M. hyopneumoniae and C2057A, C2610U and A2059G mutations for Mycoplasma hominis (10,19,20). Although tulathromycin, tilmicosin and tylosin are macrolides, their structures are different.…”

Chemotherapeutic Strategies with Valnemulin, Tilmicosin, and Tulathromycin to Control Mycoplasma hyopneumoniae Infection in Pigs

“…Among the drugs that do not belong to the Group III (Quinolones, Cephalosporins, Polymyxins, and Phosphonic Acids), a category of drugs classified by the World Health Organization (WHO) as a last resort for use in animals [ 6 ], valnemulin, tilmicosin and tulathromycin are the molecules that have been proven effective against respiratory pathogens in general and possibly in controlling EP [ 7 , 8 , 9 , 10 ]. Finally, given the search for alternatives in the control of M. hyopneumoniae that can be supported with vaccination and are in line with the rational use of antimicrobials, the objective of this study was to evaluate the effects of different drug protocols in the control of Enzootic Pneumonia in commercial pig production and to provide data on a metaphylactic drug treatment strategy with the antimicrobials tilmicosin, valnemulin, and tulathromycin against M. hyopneumoniae infection in pigs.…”