There are no formal requirements from regulatory authorities on the microbiological studies that need to be conducted in advance of a phase 1 trial. However, a range of studies will need to be carried out to demonstrate that a candidate drug has activity against target pathogens.
Such studies are likely to include:
- In vitro studies confirming activity against target pathogens, including determination of minimum inhibitory concentrations (MICs) against relevant clinical isolates (usually 50–100 clinical isolates). The conditions under which susceptibility was assessed must be carefully defined.
- Studies to explore the mechanism of action of the drug.
- Experiments to assess loss of susceptibility to the investigational drug and the frequency at which resistance develops
- Time kill studies to monitor the effect of different drug concentrations on bacterial growth over time, which will show whether a drug is bacteriostatic or bactericidal.
Because the investigational drug is being given to healthy participants, microbiology studies are not conducted on study subjects during the trial.