BONUS SPRING SUMMER 2025

over the counter (OTC). Antibiotics are often prescribed for viral infections like the flu, where it has no impact – they only work on bacterial infections. A study led by researchers at the Oxford University Clinical Research Unit in Vietnam investigated antibiotic access and OTC use in six countries. The study found that: • Vietnam: 55,2% of antibiotics were obtained without a prescription. • Bangladesh: 45,7% • Ghana: 36,1% • Mozambique: 8% • Thailand: 3,9% • South Africa: 1,2% This brings us to the last driver, which is international travel and trade. Although SA has relatively low access to OTC (1,2%), international travel and trade can spread ABR bacteria throughout the world. Where do we use antibiotics in animal production, and how important is the contribution of those usages to ABR? There are a few antibiotics that are generally used in animal production to maintain health and increase production. • They can be classified as prophylactic antibiotics (feed additives such as ionophores). • Antibiotic therapy refers to the use of antibiotics to treat infections caused by bacteria. • If the treatment is started before the exact bacteria are identified, it’s called empiric antibiotic therapy. • Once the specific bacteria are known and the antibiotic is chosen accordingly, it’s called targeted (or definitive) antibiotic therapy. • The most common problem is that much of the antibiotic therapy is applied in a blanket approach, and not really in a targeted approach. What are ionophores? • Ionophores are antibiotics used exclusively for animals and not in human medicine. • They help control infections such as coccidiosis in poultry and ruminants and improve feed efficiency. We saw in the previous article that cattle numbers reduced, but meat yield increased, due to the increased production related to the use of ionophores. • Examples: Monensin, Lasalocid, and Salinomycin. Do ionophores contribute to antibiotic resistance in humans? Direct contribution is unlikely: • Since ionophores are not used in human medicine, there is no direct selection pressure for resistance to human-use antibiotics (not MIA). • Ionophore resistance genes are not known to be shared with clinically relevant antibiotics (as of current research). Indirect effects are possible: • Ionophores can still alter the gut microbiota in animals, which might: • Increase horizontal gene transfer (HGT) among bacteria. • Select for multidrug resistance plasmids if they’re co-located with ionophore resistance genes (though this is rare). • Use of any antimicrobial may contribute to a general resistance-promoting environment in animal gut flora or manure that can reach the environment or food chain. This is where the classification of antibiotics becomes important. Two bodies have classified antibiotics in terms of MIA (Medically Important Antibiotics). They are the WHO (World Health Organisation) and EMA (European Medicines Agency). The EMA categorisation classifies antibiotics into four categories (A–D): Ionophores used in animal feed fall in the D-category. Spring/Summer 2025 BONUS www.agribonus.co.za 86