Division 3.1.2 Microbial studies

Studies shall be provided to determine the ability of the additive to induce cross-resistance to antibiotics used in human or veterinary medicine, to select resistant bacterial strains under field conditions in target species, to give rise to effects on opportunistic pathogens present in the digestive tract, to cause shedding or to excrete zoonotic micro-organisms.

If the active substance(s) possesses antimicrobial activity at the feed concentration level, the minimum inhibitory concentration (MIC) for relevant bacterial species shall be determined, according to standardised procedures. Where relevant antimicrobial activity is demonstrated, the ability of the additive to select resistant bacterial strains in vitro and in the target species, and to induce cross-resistance to relevant antibiotics shall be established^f1.

Tests at the recommended use level shall be provided for all microbial additives, and for those other additives in which an effect on the gut micro-flora can be anticipated. These studies shall demonstrate that use of the additive does not create conditions conducive to an overgrowth and shedding of potentially pathogenic micro-organisms.

The choice of micro-organisms to be monitored will depend on the target species, but shall include relevant zoonotic species, regardless of whether or not they produce symptoms in target animals.