Bacterial Resistance
Bacterial resistance may be innate (natural) or acquired. Some bacteria have an innate resistance to the specific target (bacterial multiplication, cell wall, or
metabolism) of a particular type of antimicrobial. This resistance is part of the bacteria’s normal physical characteristics. Since bacteria multiply very rapidly, they go through many generations in a short period of time. There is always the potential for antimicrobial resistance to arise through a genetic change (mutation). If this change gives the bacteria a survival advantage, it may be passed on to subsequent generations.
An acquired resistance may develop through a selection process. When a patient is treated with an antimicrobial, the most susceptible bacteria are the ones that are killed first. If treatment is stopped before all of the pathogenic bacteria are killed, the survivors may develop a resistance to that particular antimicrobial. The next time they are exposed to the same drug, it may be ineffective as the bacteria and their progeny are likely to retain resistance to that antimicrobial.
Resistance can also develop when bacteria that are resistant share their genetic material with susceptible bacteria. This may occur more frequently in a health care setting, where many patients are treated with antimicrobials and many have compromised immune systems. For instance, resistant strains of bacteria, such as MRSA (methicillin resistant Staphylococcus aureus), have been a problem in hospitals for decades and are now becoming common in the community.
When a resistance trait arises in bacteria, for whatever reason, the resistant organism may spread to other people, throughout a community, and potentially across the world. Once a strain of bacteria has become resistant to one or more drugs, the only recourse is to try to inhibit its spread and to try to find another drug that will kill it. The second or third choice drugs that are available are often more expensive and toxic (associated with more side effects). This challenge is compounded by the fact that bacteria are becoming resistant faster than new antimicrobials are being developed.
