Hospitals and community and rural health clinics that serve low-income patients say drug manufacturers have threatened their financial stability by dramatically cutting back their participation in a federal drug discount program that saves those health providers millions of dollars a year. Without the drug discounts, the hospitals and clinics say, they are getting close to laying off health care workers, reducing hours or scaling back or scrapping mobile health vans, free cancer screenings, behavioral health treatment and a host of other services that help patients with low incomes who lack in…