All persons who come in contact with guaranteed raw milk shall exercise scrupulous cleanliness and shall not be afflicted with any communicable disease or in a condition to disseminate the germs of any communicable disease which is liable to be conveyed by milk. The absence of such germs in all such persons shall be determined by bacteriological and physical examination by a health department which maintains an approved milk inspection service, or other person or laboratory which is approved in writing by the department, conducted at the time of employment and every six months thereafter in a manner which is approved by the director.