Changes

Bacteriologists soon found that E. coli grown in media containing streptomycin not only produced strains capable of resisting streptomycin, they actually in some cases developed strains that thrived on it and ''required'' it for growth.

Bacteriologists soon found that E. coli grown in media containing streptomycin not only produced strains capable of resisting streptomycin, they actually in some cases developed strains that thrived on it and ''required'' it for growth.

In the last half of the twentieth century, a situation developed which was often described as an "arms race" between doctors and bacteria. Bacteria kept developing resistance to drugs, but researchers and drug companies kept ahead of them by developing new drugs. Drug company representatives combed the world collecting soil samples and biological specimens, looking for useful antibiotics in nature, while chemists tried to synthesize new antibiotics in the laboratory. The 1960s saw the emergence of a number of synthetic penicillin-like drugs, such as ampicillin, amoxicillin, and cloxacillin.  

In the last half of the twentieth century, a situation developed which was often described as an "arms race" between doctors and bacteria. Bacteria kept developing resistance to drugs, but researchers and drug companies kept ahead of them by developing new drugs. Drug company representatives combed the world collecting soil samples and biological specimens, looking for useful antibiotics in nature, while chemists tried to synthesize new antibiotics in the laboratory. The 1960s saw the emergence of a number of synthetic penicillin-like drugs, such as ampicillin, amoxicillin, and cloxacillin. But by the 1990s the development and discovery of entirely new classes of antibiotics appeared to have reached an end; scientists only managed to make improvements within existing classes of drugs.<ref>[http://news.bbc.co.uk/1/hi/health/background_briefings/antibiotics/163997.stm A brief history of antibiotics], BBC news</ref> There is widespread concern that the bugs are catching up. The generation now approaching retirement may be the only human generation in history to live its entire life free from the mortal dread of bacterial infection.

 

 

==Notes and references==

==Notes and references==

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