A patient was sent to me once for a recommendation on whether or not she needed to continue taking antibiotics “permanently” to prevent pneumonia. She had a chronic lung disease which resulted in scarring of her lungs. Because she had several episodes of pneumonia in the past, another doctor had put her on antibiotics for almost 2 years.
The patient’s antibiotic regimen consisted of daily azithromycin for 3 months, then daily doxycycline for the next 3 months, and she would alternate them back and forth. She did not seem to be having any obvious side effects from the antibiotics.
Over the past year, she was admitted to hospital about 2-3 times with cough, shortness of breath, and fever. Each time, she was diagnosed with pneumonia, and her sputum (the mucous she coughed out of her lungs) cultures were positive for the same bacteria (Pseudomonas).
After I examined her and reviewed her records, we discussed my impression of her situation. Essentially, I did not think that she needed to continue antibiotics indefinitely to prevent pneumonia. Especially since the antibiotics she was taking were not even effective against the Pseudomonas that was showing up every time she got admitted to hospital.
The patient left the office rather displeased that she did not get her antibiotics refilled.
The next month, I got a call to see her in the hospital because she was “in again” with pneumonia.
When I went to see her, you can imagine the accusatory look she gave me. I gave her a cheerful greeting, and she said “well, I am back in the hospital with pneumonia! This is because you stopped my antibiotics.”
After I reviewed everything, to be honest, I was not convinced that she had pneumonia. Yes, she had cough and a bit of mucous production, however there was no fever, she did not look particularly ill, and her chest X-ray was unimpressive.
Because she was hospitalized, she was given intravenous antibiotics while we awaited the results of her cultures. Well, those cultures came back, and guess what? They were negative! Negative for the first time in years, probably.
So for the years she was on 2 cycling antibiotics, her sputum kept growing Pseudomonas. But one month after stopping the antibiotics, the Pseudomonas is no where to be found.
So…why were the patient’s sputum cultures positive while she was taking antibiotics, and negative when she came off antibiotics?
The likely answer is colonization resistance. Colonization refers to the process whereby bacteria and other microorganisms (germs) live in balance on and within our bodies, without causing disease. Different germs colonize different parts of the body. For example, there is staph on the skin, strep and some types of yeast in the mouth, E. coli and millions of other bacteria in the stool.
Because the native flora are in balance, they serve as a barrier to more dangerous pathogens (germs) causing infection. That is, they ‘crowd out’ the bad germs. So colonization with good germs, causes resistance to infection with bad germs.
When someone takes antibiotics for a prolonged period, a lot of the good bacteria are killed off, and so the bad bacteria are able to survive, multiply, invade and eventually cause disease.
For the patient described above, the cycle of antibiotics killed a lot of her good bacteria. Therefore, Pseudomonas was able to overgrow, invade, and cause her repeated lung infections.
Once she stopped taking the antibiotics, her normal bacterial flora recovered, and overpowered, or “crowded-out” the Pseudomonas, so that it was no longer able to survive and cause problems for her.
The patient was surprised in the end, to find out that not only was Pseudomonas not cultured during this hospitalization, but her sputum culture was completely negative.
Her symptoms were probably just an exacerbation of inflammation, related to her chronic lung diseases.
Don’t get me wrong…people with chronic lung disease are more prone to pneumonia because of the scarring and abnormal anatomy of their lungs, with pockets, or ‘holes’ here bacteria can multiply quietly and cause disease.
There are some cases cases of chronic lung disease, for example cystic fibrosis, that do require antibiotic suppression for prevention of pneumonia.
However, in most cases, the patient is best kept off antibiotics, thus allowing their normal bacteria to survive, which will in turn enable them to resist infection from bad germs. Additionally, the patient is spared the potential side effects from antibiotics.
Sometimes, we tamper too much with Mother Nature.