Antibiotic Resistance

antibiotic resistance, loss of susceptibility of bacteria to the killing (bacteriocidal) or growth-inhibiting (bacteriostatic) properties of an antibiotic agent. When a resistant strain of bacteria is the dominant strain in an infection, the infection may be untreatable and life-threatening. Examples of bacteria that are resistant to antibiotics include methicillin-resistant Staphylococcus aureus (MRSA), penicillin-resistant Enterococcus, and multidrug-resistant Mycobacterium tuberculosis (MDR-TB), which is resistant to two tuberculosis drugs, isoniazid and rifampicin. MDR-TB is particularly dangerous because it can give rise to extensively drug-resistant M. tuberculosis (XDR-TB), which requires aggressive treatment using a combination of five different drugs.

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The potential for antibiotic resistance was recognized in the early 1940s, almost immediately after the first large-scale clinical applications of penicillin, the first antibiotic. Mass production of penicillin was part of the greater war effort of World War II, when the drug was used widely by military populations and by some small civilian populations. Along with penicillin’s effectiveness in the treatment of the wounded, the drug was lauded for lowering the rate of venereal disease among military personnel, since it was particularly potent against the bacterial organisms notorious for causing syphilis and gonorrhea. However, even before the war had ended, resistance to penicillin was already reported—first in 1940 by British biochemists Sir Ernst Boris Chain and Sir Edward Penley Abraham, who published a report about an enzyme capable of destroying penicillin, and again in 1944 by several scientists working independently, who reported a penicillin-inactivating enzyme that was secreted by certain bacteria. In the following decades, overuse and repeated exposure to antibiotic agents favoured the selection and replication of numerous strains of antibiotic-resistant bacteria.