Johnson and Johnson is laying off about 300 of the 400 employees at its McNeil Consumer Healthcare Fort Washington Plant, which will probably stay closed until at least the middle of next year. Production there was halted in April. The company said earlier this month it is conducting a quality assessment, and it will take corrective actions before manufacturing resumes. The company voluntarily closed the plant, where it made Children’s Tylenol and other products, after the Food and Drug Administration found bacteria and other contaminants in raw ingredients used to make them. The company recalled more than 40 versions of Tylenol, Motrin, Benadryl and Zyrtec. Employees will continue receiving their salaries and benefits until at least mid-September, and then the ones who are laid off will get severance packages. The company says it will consider them for re-hiring when the plant re-opens with a smaller staff.