The “ Evolution ” of Antibiotic Resistance

An increase in the frequency of antibiotic resistance in bacteria since the 1950s has been observed for all major classes of antibiotics used to treat a wide variety of respiratory illnesses, skin disorders, and sexually transmitted diseases. Is this resistance the result of bacteria evolving new genes in response to the presence of antibiotics, or are antibiotic-resistant bacteria selected for in the environment by possessing antibiotic resistance genes beforehand? To answer these questions a discussion of several factors involved in antibiotic resistance will show that resistance is a designed feature of pre-existing genes enabling bacteria to compete with the antibiotic producers in their environment. A brief look at an example of penicillin resistance reveals the increase in the frequency of antibiotic-resistant organisms since the time when antibiotic use became common. Penicillin is an antibiotic produced by the common bread mold Penicillium that was discovered accidentally in 1929 by the British microbiologist, Alexander Fleming. By the 1940s, penicillin was available for medical use and was successfully used to treat infections in soldiers during World War II. Since then, penicillin has been commonly used to treat a wide range of infections. In 1967 the first penicillin-resistant Streptococcus pneumoniae was observed in Australia, and seven years later in the U.S. another case of penicillin-resistant S. pneumoniae was observed in a patient with pneumococcal meningitis. In 1980 it was estimated that 3–5% of S. pneumoniae were penicillin-resistant and by 1998, 34% of the S. pneumoniae sampled were resistant to penicillin. Antibiotic resistance by other organisms reflects the same trend observed between S. pneumoniae and penicillin. Tetracycline resistance by normal human intestinal flora has exploded from 2% in the 1950s to 80% in the 1990s. Kanamycin, an antibiotic used in the 1950s, has become clinically useless as a result of the THE “EVOLUTION” OF ANTIBIOTIC RESISTANCE