Antibiotic improve treatment outcome as the combined effect of both antibiotics is better than their individual effect. Methicillin-resistant Staphylococcus aureus infections may be treated with a combination therapy of fusidic acid and rifampicin. Antibiotics used in combination may also be antagonistic and the combined effects of the two antibiotics may be less than if the individual antibiotic was given as part of a monotherapy. For example, chloramphenicol and tetracyclines are antagonists to penicillins and aminoglycosides. However, this can vary depending on the species of bacteria. In general, combinations of a bacteriostatic antibiotic and bactericidal antibiotic are antagonistic. Antibiotics are commonly classified
Antibiotic use in livestock in its inaugural 2013 report on antibiotic resistance threats in the United States, the CDC identified resistant non-typhoidal "Salmonella" and "Campylobacter" as "serious threats" and called for improved surveillance and intervention in food production moving forward. There are other bacteria as well, where research is evolving and revealing that bacterial resistance acquired through use in livestock may be contributing to disease in humans. Examples of these include Enterococcus (including "E. coli" 0157) and "Staphylococcus aureus". For foodborne illness from "E. coli", which is still not typically treated with antibiotics because of associated risk of renal failure, increasing rates of antibiotic-resistant