Bacterial antibiotic resistance: mechanism explained (Introduction)

by David Turell @, Monday, February 11, 2019, 17:03 (191 days ago) @ David Turell

Studies have shown that when antibiotics fail, it is due to a one percent resistant strain in the bacteria. I've explained it before, In nature antibiotics are present and part of wars between bacteria and bacteria and bacteria and fungi. We use naturally produced antibiotics so some bacteria are prepared to recognize them and resist:

"When a bacterial infection is suspected, samples are taken for analysis to assess whether the bacterium can be treated with (i.e. is susceptible to) antibiotics or not (i.e. is resistant), and what kind of antibiotic works. Heteroresistance means that while the majority of bacteria in the sample are susceptible to antibiotics, there is also a minor (less than 1 percent) antibiotic-resistant subpopulation that can grow despite treatment with antibiotics.

"No research to date has explained the underlying mechanisms of heteroresistance. As previous studies on humans and animals alike have shown, heteroresistance can make antibiotic treatment ineffective because the resistant subpopulation grows instead of being destroyed.


"They surveyed the scale on which it was present in four bacteria species that cause infections in humans by exposing them to 28 different kinds of antibiotic. Surprisingly, the results showed that more than a quarter of the combinations of bacteria and antibiotics exhibited heteroresistance.

"This indicates that the frequency of heteroresistance in clinically important bacteria has been greatly underestimated before," says Dr. Hervé Nicoloff, researcher at the Department of Medical Biochemistry and Microbiology, Uppsala University and lead author of the study.

"A range of genetic investigations also enabled the researchers to show that the underlying mechanism of heteroresistance was often spontaneous occurrence of gene amplifications of various antibiotic resistance genes. The bacteria cells containing only one copy of these genes were susceptible to antibiotics, while the cells containing multiple gene copies were resistant.

"These gene amplifications are unstable, and as a result, antibiotic-resistant bacteria can rapidly revert to susceptibility again. This instability makes heteroresistance difficult to detect and study, which is a problem for hospital laboratories that need to determine whether a bacterium is susceptible or resistant to a particular antibiotic. Accordingly, bacteria can be classified as susceptible although they are actually resistant, and this may lead to use of the wrong antibiotic and failure of the treatment."

Comment: As I've previously noted, many bacterial populations have a variety of resistant and non-resistant individuals, so that group will survive on their own without gene transfer, which is another mechanism.

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