Detection and Antimicrobial Susceptibility of Mycoplasma gallisepticum and Mycoplasma synoviae among Chicken Flocks in Khyber Pakhtunkhwa, Pakistan

Abstract

Mycoplasma gallisepticum (MG) and Mycoplasma synoviae (MS) are important respiratory pathogens of poultry that adversely affect flock health, productivity, and antimicrobial-use practices. Reliable information on their occurrence and antimicrobial susceptibility in commercial poultry systems of Khyber Pakhtunkhwa (KP), Pakistan, remains limited. This study aimed to determine the occurrence of MG and MS among commercial chicken flocks in KP and evaluate associated epidemiological risk factors and antimicrobial susceptibility patterns. A cross-sectional study was conducted from January to December 2025 involving 600 clinically affected chickens from 120 commercial farms across ten KP districts. Clinical specimens were examined by culture using Frey's media, followed by biochemical identification. Antimicrobial susceptibility was assessed by broth microdilution, and MIC₅₀ and MIC₉₀ values were determined for seven antimicrobials. Epidemiological associations were analyzed using chi-square/Fisher's exact tests and multivariable logistic regression. Mycoplasma was recovered from 214/600 (35.7%) chickens. MG was detected in 132 (22.0%) and MS in 96 (16.0%), including 14 (2.3%) mixed infections. MG positivity was highest in Swabi (26.7%), whereas MS positivity was highest in Dera Ismail Khan (18.2%). Previous antimicrobial use (AOR=2.6), poor biosecurity (AOR=3.1), flock age >6 weeks (AOR=2.3), and broiler production (AOR=1.8) were significantly associated with detection. Tiamulin and tylvalosin showed the lowest MIC₅₀/MIC₉₀ values. MG and Mycoplasma synoviae were prevalent among clinically affected commercial chickens, with management-related factors contributing to detection. Strengthened biosecurity, prudent antimicrobial use, appropriate surveillance, and improved flock-level prevention strategies are recommended.