How do bacteria become resistant to antibiotics?

Antibiotic resistance occurs when bacteria change in some way that reduces or eliminates the effectiveness of drugs, chemicals or other agents designed to cure or prevent infections. The bacteria survive and continue to multiply causing more harm.

Bacteria can do this through several mechanisms. Some bacteria develop the ability to neutralize the antibiotic before it can do harm, others can rapidly pump the antibiotic out, and still others can change the antibiotic attack site so it cannot affect the function of the bacteria.

Antibiotics kill or inhibit the growth of susceptible bacteria. Sometimes one of the bacteria survives because it has the ability to neutralize or escape the effect of the antibiotic; that one bacterium can then multiply and replace all the bacteria that were killed off. Exposure to antibiotics therefore provides selective pressure, which makes the surviving bacteria more likely to be resistant.

In addition, bacteria that were at one time susceptible to an antibiotic can acquire resistance through mutation of their genetic material or by acquiring pieces of DNA that code for the resistance properties from other bacteria. The DNA that codes for resistance can be grouped in a single easily transferable package. This means that bacteria can become resistant to many antimicrobial agents because of the transfer of one piece of DNA.

Dr. Mehmet Oz, MD
Cardiologist (Heart Specialist)

Since bacteria have been repeatedly bombarded with the same antibiotics for the last few decades, they have evolved a way to protect themselves. These Darwinian-style, survival-of-the-fittest adaptations benefit the survival of all organisms. So if a bacteria cell has evolved a feature that somehow pumps out or deactivates the antibiotic, or changes the characteristics of the attack site that prevents the antibiotic from getting in at all, it can endure. Bacteria can also pass along antibiotic resistance to an "unprotected" cell by transferring their beneficial antibiotic-resistant genes to nonresistant cells.

Since antibiotics are only able to kill sensitive bacteria, resistant bacteria will flourish until a new antibiotic is designed to attack the resistant cells in a different way.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.