Not long ago an elderly relative contacted me about a prophylactic antibiotic prescription that she received before a dental procedure. Knowing that I work in the area of antibiotic resistance, she wanted to know if she was wrong to be taking antibiotics when she wasn’t sick. It is not surprising that this question comes up given that the media is swamped with messages about antibiotic resistance and “misuse” of antibiotics. She was probably surprised when I blurted out that she should ‘take the antibiotics’ without a moment of hesitation. At the time, my relative was in her mid-70s and had a pacemaker.

Dentists prescribe antibiotics for procedures when there is risk that bacteria will get into your blood. For most people, this isn’t a significant concern because their immune systems will destroy troublesome microbes. In contrast, the American Heart Association recommends dental prophylaxis when you have prosthetic material in your heart, a heart transplant, or congenital heart defects. Amoxicillin is commonly prescribed for this purpose, and it is probably the most commonly prescribed antibiotic in the world (and it still works for many things).

Not taking an appropriate course of prophylactic antibiotic, however, can lead to serious complications. For example, back in September my father (going on 83) had a minor dental surgery for which he was prescribed two days of prophylactic antibiotic (amoxicillin). At the time he was being treated with a blood thinner for an atrial fibrillation that had emerged a month earlier. Unfortunately, the word about the blood thinner either did not get to the dentist or the information was ignored. A week after the surgery my father experienced unexplained spontaneous bleeding from the surgical site, but it eventually cleared up. Despite this improvement, he seemed to get increasingly tired and discouraged over the next couple weeks.

In early December my father awoke in the middle of the night and realized he was in serious trouble. It turns out that he was experiencing acute heart failure and was probably on the verge of full-scale septic shock. He could have easily perished if he had not woken. Fortunately, not only did he wake up, but he was lucid enough to understand his peril and to call for help.

The ambulance took him to a hospital where they quickly established that my father had endocarditis. They were able to recover an oddball bacterium, Streptococcus salvarius, from his blood. Such an organism is consistent with complications from a dental procedure, and we were lucky because it was sensitive to most first-line antibiotics. Imaging showed a “vegetative structure” from the bacteria growing on the mitrel valve in his heart. Not long after this he was airlifted to a referral hospital in Seattle.

By this time, my father had received several antibiotics that we consider “high-powered” including vancomycin, penicillin-gentamicin, and ceftriaxone. He was eventually prepped for surgery to replace the afflicted heart valve, but a final check with endoscopy showed that the vegetative structure was gone. He was spared a chest-cracking surgery.

Within a day the material from vegetative structure lodged in his leg where it caused a deep-vein thrombosis. While there are far worse places for a clot to form, this is going to take a long time to clear and its presence makes recovery very challenging. As we move forward, he is receiving daily intravenous doses of a potent cephalosporin antibiotic.

My reason for sharing these details is to highlight an important lesson. Given widespread concerns about antibiotic resistance, there are pressures to limit antibiotic use for the “greater good.” Nevertheless, if people like my father are given a more appropriate prophylactic prescription, it is likely that they will avoid life-threatening and life-altering experiences. Instead, having only two days of prophylaxis probably contributed to my father eventual needing large quantities of very powerful antibiotics for extended periods of time … which is a perfect scenario to selectively favor antibiotic-resistant bacteria.

Not only should antibiotic prescriptions be followed closely, but people need to remember that there are times when taking an antibiotic helps limit selection for antibiotic-resistance far more than withholding the drugs and dealing with a complex aftermath.

Douglas Call is a microbiologist. He and his family have lived on the Palouse for more than 20 years.

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