Antibiotic Resistance: Origins, Evolution, Selection and Spread

Antibiotic resistance thwarts the treatment of infectious diseases worldwide. Although a number of factors can be identified which contribute to the problem, clearly the antibiotic as a selective agent and the resistance gene as the vehicle of resistance are the two most important, making up a 'drug resistance equation'. Both are needed in order for a clinical problem to arise. Given sufficient time and quantity of antibiotic, drug resistance will eventually appear. But a public health problem is not inevitable if the two components of the drug resistance equation are kept in check. Enhancing the emergence of resistance is the ease by which resistance determinants and resistant bacteria can spread locally and globally, selected by widespread use of the same antibiotics in people, animal husbandry and agriculture. Antibiotics are societal drugs. Each individual use contributes to the sum total of society's antibiotic exposure. In a broader sense, the resistance problem is ecological. In the framework of natural competition bet ween susceptible and resistant bacteria, antibiotic use has encouraged growth of the resistant strains, leading to an imbalance in prior relationships between susceptible and resistant bacteria. To restore efficacy to earlier antibiotics and to maintain the success of new antibiotics that are introduced, we need to use antibiotics in a way which assures an ecological balance that favours the predominance of susceptible bacterial flora. 1997 Antibiotic resistance: origins, evolution, selection and spread. Wiley, Chichester (Ciba Foundation Symposium 207) p 1-14 In large part, bacteria live in harmony with other inhabitants of the earth. Although some infections are caused by bacteria for which humans are a specific host, in most instances the infections follow entry of bacteria into the body by chance. Over the past 50 years, the classic treatment of bacterial infectious diseases has been antibiotics, the discovery of which vastly changed the relationship between bacteria and people. Today we are witnessing another change, that is, among the bacteria themselves. While diversity characterizes the microbial flora, antibiotic use has led to a further subgrouping into those bacteria that are susceptible and those that are resistant to antibiotics. Prior to antibiotic introduction, the large majority of commensal and