Every railroad company operating a railroad in whole or part within this state is liable for all damages sustained by any of its employees by reason of personal injury or death of such employee:

(A) When such injury or death is caused by a defect in any locomotive, engine, car, handcar, rail, track, machinery, or appliance required by such company to be used by its employees in and about the business of their employment, if such defect could have been discovered by reasonable and proper care, tests, or inspection. Proof of such defect shall be presumptive evidence of knowledge of it on the part of such company. An employee of such railroad company who is injured or killed as a result of such a defect shall not be deemed to have assumed the risk occasioned thereby, although continuing in the employment of the company after knowledge of the defect, nor shall continuance in employment after such knowledge by an employee be deemed an act of contributory negligence.

(B) While such employee is engaged in operating, running, riding upon, or switching passenger, freight, or other trains, engines, or cars, and in the performance of his duties, and when such injury was caused by the carelessness or negligence of any other employee, officer, or agent of such company, in the discharge of or for failure to discharge his duties as such.