Antibiotic resistance
Antibiotic resistance is a form of drug resistance whereby some (or, less commonly, all) sub-populations of a microorganism, usually a bacterial species, are able to survive exposure to one or more antibiotics. Accordingly, pathogenic species which have become resistant cause infections which can not be treated with the usual, formerly efficacious antibiotic drugs and/or their usual, formerly efficacious, dosages and concentrations. Resistance may be instrinsic or acquired. Some clinically relevant pathogens have developed resistance to multiple antibiotics and are dubbed multidrug resistant (MDR pathogens). More recently, the colloquial term superbug has become widespread in both popular and technical accounts of the phenomenon with which it is synonymous.
Antibiotic resistance is a serious and growing phenomenon in contemporary medicine and has emerged as one of the eminent public health concerns of the 21st century, particularly as it pertains to pathogenic organisms (the term is not especially relevant to organisms which don't cause disease in humans). In the simplest cases, drug-resistant organisms may have acquired resistance to first-line antibiotics, thereby necessitating the use of second-line agents. Typically, the first-line agent is selected on the basis of several advantages including safety, availability and cost; comparatively, the second-line agent is usually broader in spectrum, possesses a less favourable risk-benefit profile and may be more expensive or, in more dire circumstances, locally unavailable. In the case of some MDR pathogens, resistance to second and even third-line antibiotics is sequentially acquired, a case quintessentially illustrated by Staphylococcus aureus in some nosocomial settings. Some pathogens, such as Pseudomonas aeruginosa, additionally possess a high level of intrinsic resistance.
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