Penicilin Resistant Staphylococcus

Another prime example of selection is resistance to penicillin. When it was introduced in the early 1940s, penicillin was a miracle drug, especially effective at curing infections caused by the bacteria Staphylococcus aureus (“staph”). In 1941, the drug could wipe out every strain of staph in the world. Now, seventy years later, more than 95 percent of staph strains are resistant to penicillin. What happened was that mutations occurred in individual bacteria that gave them the ability to ...

 Antibiotics Evolve Bacteria in the Gut

New antibiotics have been coming out at frequent intervals since then, and bacteria have evolved resistance to just about every one of them. Nowadays, the most ominous example is MRSA (methycillin-resistant Staphylococcus aureus), which has succeeded in making many hospitals positively dangerous places to visit. Another menace is ' C. diff.' ( Clostridium difficile). Here again, we have natural selection favouring strains that are resistant to antibiotics; but the effect is overlain by anothe...