Official guidance documents we use in New Zealand to cover the handling and transportation of microbiology samples from provincial hospitals to centralized testing laboratories.
I expect that official guidance would cover aspects such as reported by Miller et al. [1] including transport media, temperature and time from specimen extraction from patient until the analysis is completed at the centralized laboratory. [1] Miller et al., A guide to utilization of the microbiology laboratory for diagnosis of infectious diseases 2018: Updated by the Infectious Diseases Society of America and the American Society of Microbiology. Current Infectious Diseases 2018, 67(6), e1-e94. doi: 10.1093/cid/ciy381.