Molecular Differentiation of Mycoplasma gallisepticum Outbreaks: A Last Decade Study on Italian Farms Using GTS and MLST.

Andrea Matucci,Salvatore Catania,Gelinda De Grandi,Ilenia Rossi,Elisabetta Stefani,Michele Gastaldelli,Miklós Gyuranecz

doi:10.3390/vaccines8040665

Abstract

Mycoplasma gallisepticum (MG) infects many avian species and leads to significant economic losses in the poultry industry. Transmission of this pathogen occurs both horizontally and vertically, and strategies to avoid the spread of MG rely on vaccination and the application of biosecurity measures to maintain breeder groups as pathogen-free. Two live attenuated MG vaccine strains are licensed in Italy: 6/85 and ts-11. After their introduction, the implementation of adequate genotyping tools became necessary to distinguish between field and vaccine strains and to guarantee proper infection monitoring activity. In this study, 40 Italian MG isolates collected between 2010–2019 from both vaccinated and unvaccinated farms were genotyped using gene-targeted sequencing (GTS) of the cythadesin gene mgc2 and multilocus sequence typing (MLST) based on six housekeeping genes. The discriminatory power of GTS typing ensures 6/85-like strain identification, but the technique does not allow the identification ts-11 strains; conversely, MLST differentiates both vaccine strains, describing more detailed interrelation structures. Our study describes MG genetic scenario within a mixed farming context. In conclusion, the use of adequate typing methods is essential to understand the evolutionary dynamics of MG strains in a particular area and to conduct epidemiological investigations in the avian population.

Highlights

Mycoplasma gallisepticum (MG) is one of the four main avian pathogenic Mycoplasma species [1].MG can cause reproductive and/or respiratory disorders, airsacculitis and other chronic respiratory diseases (CRD) [2]
The biomolecular characterization of MG outbreaks is essential to identify circulating strains and differentiate vaccine isolates from field ones
On a total of 40 Italian samples isolated mainly from chickens and turkeys over the last decade, we found that Pink type was the most prevalent when using mgc2-gene-targeted sequencing (GTS), while the CC1 was the most prevalent when using multilocus sequence typing (MLST)

Summary

Introduction

Mycoplasma gallisepticum (MG) is one of the four main avian pathogenic Mycoplasma species [1].MG can cause reproductive and/or respiratory disorders, airsacculitis and other chronic respiratory diseases (CRD) [2]. MG mainly affects turkeys and chickens, but the infection of other avian species, such as quails, geese, guinea fowls, house finches, etc., is reported [3]. This pathogen causes significant economic losses in the poultry industry due to higher carcass condemnation rates, growth retard, embryonal mortality, and reduced meat and egg production. The maintenance of MG-free breeder flocks is the most adequate method to contain the infection and prevent pathogen spread. One such approach relies on strict biosecurity measures and prompt detection of MG infections

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Discussion

Conclusion