Poultry MG and microbiome research is moving from isolated inhibition findings toward integrated analysis of respiratory communities, metabolites and host barriers. Controlled studies report that selected lactobacilli or Bacillus interventions can accompany lower MG-related molecular signals, less tissue injury or improvements in some production outcomes. Responses still differ by strain and endpoint. This review examines direct chicken studies involving Mycoplasma gallisepticum (MG), distinguishes live organisms from cell-free supernatants and functional mechanism experiments, and does not turn these findings into disease-control promises for all probiotics or commercial products.