Another genetic mechanism of antibiotic resistance is the acquisition and accumulation of resistance genes from neighboring bacteria through a process known as transformation. A good example of this is the pneumococcus bacterium, which is a common cause of pneumonia, bacterial sinusitis, middle ear infections and even meningitis. When penicillin first became available for clinical use in the 1940s, the pneumococcus bacterium was 100 percent susceptible to penicillin. After decades of use, a portion of pneumococcal bacteria have accumulated small pieces of genetic material that they have scavenged from other bacteria, rendering them resistant to the effects of penicillin. Finally, a fourth genetic mechanism by which bacteria can develop antibiotic resistance is through mutations in their DNA. Every time a bacterium multiplies and grows, it may develop a mutation in its DNA. If the mutation occurs in a part of the DNA that codes for a protein or substance that is the target of an antibiotic, the bacteria may become resistant to that drug.
There is nothing stopping a bacterium from becoming resistant to more than one antibiotic. In fact, for some bacteria and antibiotics, cross resistance is common, which creates a new problem. The more drugs a bacterium is resistant to, the more difficult it becomes to treat an infection. Although many alternative antibiotics are currently available for use and new ones continue to be developed, there is a concern that doctors may run out of options for treating some highly resistant bacterial infections. Newer antibiotics may also be more costly than older ones and could come with side effects that make them more difficult to take. Ultimately the biggest concern with antibiotic resistance is that a patient will be treated for a potentially life threatening infection such as meningitis with an antibiotic to which the underlying bacteria is resistant. By the time the resistance is recognized through laboratory testing the patient may have suffered severe consequences.
The hope is that with more appropriate use of antibiotics and thus a reduction in antibiotic selection pressure, we can stem the tide of resistance and maintain a useful armamentarium of antibiotics for treating all types of bacterial infections. Patients should thus avoid taking antibiotics for things such as the common cold (which is caused by viruses and not bacteria), complete their courses of antibiotics as prescribed and not share their antibiotics with others.