Bacteria's ability to develop resistance to antibiotics puts fear in all of our hearts. However, we have always assumed that if an antibiotic is not used for a long period of time the bacteria will discard their antibiotic resistance genes when they are no longer needed.
The theory is that the antibiotic resistant bacteria are less fit to survive in the real world. Bacteria not resistant to an antibiotic don't have to carry around this extra DNA or put up with a mutation in their DNA to grow. Therefore, if you put an antibiotic-resistant bacterium in the same tube as an antibiotic-sensitive bacterium the antibiotic-sensitive bacterium should grow faster and win in a competition for nutrients. To my surprise, an article in Science recently stated antibiotic-resistant bacteria may be with us for a long long long time.
Studies conducted by Bruce Levin from Emory University looked at the persistance of streptomycin-resistance Escherichia coli (a bacteria) taken from children at day-care centers. Streptomycin has been rarely if ever used during the last 30 years. However, the researchers were still able to get streptomycin resistant Escherichia coli isolates from these children.
Richard Lenski at Michigan State University in East Lansing also found Escherichia coli grown in media free of streptomycin, remain resistant to streptomycin. These particular bacteria kept their resistance to streptomycin for 10 years (20,000 generations). Only one nucleotide in the bacteria's DNA needs to be mutated to develop resistance to streptomycin. The streptomycin-resistant bacteria do not initially grow very well when this mutation occurs. However, if these streptomycin resistant bacteria are allowed to grow for a number of generations another mutation can occur. This second mutation helps the streptomycin-resistant Escherichia coli to grow as well as streptomycin-sensitive Escherichia coli.
Now don't get alarmed. Not all antibiotic-resistant bacteria will remain resistant forever. The theory mentioned above does work in many cases of antibiotic resistance. However, avoiding the use of an antibiotic for a while in hopes that the bacteria will lose their antibiotic-resistance genes will not always work. Bacteria can remain resistant to a particular antibiotic for a long time. Tenacious little guys, aren't they?
How do we stop this ever increasing resistance of bacteria to antibiotic? We need to be very careful not to take antibiotics we do not need. Taking antibiotics when not necessary has caused a large number of disease-causing bacteria to be resistant to many commonly used antibiotics. The common cold is caused by viruses. Antibiotics do not kill viruses. Going to the doctor and demanding an antibiotic is not going to cure your cold and it may produce another antibiotic-resistant bacterial strain.
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