In just three weeks, the bacterium developed resistance to an antibiotic used when none of the others worked. Unexpectedly, this made it possible to find the weak point of a dangerous microorganism.
Antibiotics of the last reserve are the means used when the pathogenic microorganism has not been defeated by other, more routine means. Since microbes evolve rapidly, developing resistance to drugs, the drugs of the last reserve tend to be used as little as possible, so as not to lose this weapon in the fight against the disease.
A report published in Antimicrobial Agents and Chemotherapy describes how one strain of Pseudomonas aeruginosa was able to defeat the combined antibiotic ceftolosan-tazobactam. It is considered a last resort for severe gram-negative nosocomial infections, including those with multidrug-resistant P. aeruginosa.
The most unpleasant thing about this story is that the case was not recorded in the laboratory, but in vivo - during the treatment of the patient. Doctors at a French hospital treated a child who had twice undergone liver surgery. For more than two years he suffered from a recurrent infection with Pseudomonas aeruginosa.
Pseudomonas aeruginosa is a gram-negative microorganism that usually lives in soil and water. It is the most common causative agent of nosocomial infections affecting debilitated patients, and one of the most difficult microorganisms to treat. P. aeruginosa evolve very quickly and, one might say, are at the forefront of antibiotic resistance. They have a kind of analogue of social behavior, "quorum sense" - the ability to communicate and coordinate behavior using signaling molecules. P. aeruginosa forms biofilms that harbor colonies and protect against drugs.
The patient from the article underwent surgery, but after that the infection recurred threateningly. The doctors prescribed ceftolosan-tazobactam. Earlier laboratory data showed that in life there is very little chance of getting a stick resistant to this agent, and at first the treatment looked successful. However, 22 days after the start of therapy, doctors discovered a new strain of Pseudomonas aeruginosa in the child's body, which showed resistance to antibiotics. As a result, the doctors managed to defeat the disease, but it took more than two years.
However, there is some good news. During the fight against a dangerous infection, scientists sequenced the genome of dozens of samples of mutated rods. It turned out that during the months of battling the drug, the bacteria independently of each other created strains resistant to ceftolosan-tazobactam three times. However, becoming immune to it, the bacterium lost its immunity to other agents. As the authors note, this gives hope that even in very difficult cases, it can be overcome with the help of older drugs. This discovery may help in the future to find a way to prevent the emergence of such resistance.