This Research Communication presents a cross-sectional study to compare the prevalence of contagious, environmental, opportunistic and other intramammary infection pathogens in mountain dairy herds. In the Italian Apennine mountains, areas where dairy farming is thriving are interspersed among areas where only a few dairy herds remain. The disappearance of some dairy farms relates to the reduction of agricultural and veterinary services in a process that can jeopardize dairy herd profitability. Sixteen herds were screened for intramammary infection (IMI) pathogens. Antimicrobial susceptibility testing of mastitis pathogens was performed, and data on antimicrobial use was collected from the herd treatment registry. The prevalence of contagious IMI pathogens was significantly higher in areas where dairy farming is reducing, whereas environmental and opportunistic infections were more abundant in herds in thriving areas where farmers had a more consistent relationship with veterinarians. Antimicrobial resistance levels were low throughout all areas and did not relate to antimicrobial use, although it was significantly higher in areas where dairy herds were thriving.