Abstract
The aim of this study was to explore the prudent use of tylosin for the treatment of chronic respiratory infectious diseases in chickens caused by Mycoplasma gallisepticum (MG) based on its clinical breakpoint (CBP) and its effect on lung microbiota. The CBP was established based on the wild-type/epidemiological cutoff value (COWT/ECV), pharmacokinetics-pharmacodynamics (PK-PD) cutoff value (COPD), and clinical cutoff value (COCL) of tylosin against MG. The minimum inhibitory concentration (MIC) of tylosin against 111 MG isolates was analyzed and the COWT was 2 μg/ml. M17 with MIC of 2 μg/ml was selected as a representative strain for the PK-PD study. The COPD of tylosin against MG was 1 μg/ml. The dosage regimen formulated by the PK-PD study was 3 days administration of tylosin at a dose of 45.88 mg/kg b.w. with a 24-h interval. Five different MIC MGs were selected for clinical trial, and the COCL of tylosin against MG was 0.5 μg/ml. According to the CLSI decision tree, the CBP of tylosin against MG was set up as 2 μg/ml. The effect of tylosin on lung microbiota of MG-infected chickens was analyzed by 16S rRNA gene sequencing. Significant change of the lung microbiota was observed in the infection group and treatment group based on the principal coordinate analysis and the Venn diagrams of the core and unique OTU. The phyla Firmicutes and Proteobacteria showed difference after MG infection and treatment. This study established the CBP of tylosin against MG. It also provided scientific data for the prudent use of tylosin based on the evaluation of MG infection and tylosin treatment on the lung microbiota.
Highlights
IntroductionMycoplasma gallisepticum (MG) mainly infects turkeys and chickens, but it has been reported in other birds (Sawicka et al, 2020); it can be transmitted horizontally through direct or indirect contact or vertically through eggs (Kleven, 2008)
The MIC distribution of tylosin against Mycoplasma gallisepticum (MG) was substituted into raw count by ECOFFinder software
The growth characteristics of bacteria determine the choice of detection methods, because MG has a long growth cycle and small colony formation, which is not suitable for paper dilution method and agar dilution method, so the main test method is micro broth dilution method (Kohner et al, 1997)
Summary
MG mainly infects turkeys and chickens, but it has been reported in other birds (Sawicka et al, 2020); it can be transmitted horizontally through direct or indirect contact or vertically through eggs (Kleven, 2008). Macrolides, quinolones, tetracyclines, and Pleurotus truncatus have good antibacterial effects on MG (An et al, 2019). Tylosin has a good therapeutic effect on the respiratory diseases of livestock and poultry (Jordan et al, 1999). The effect of tylosin on the lung microbiota of chickens infected with MG is unknown and needs to be evaluated
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