It is a daily occurrence. A patient goes to the hospital for, say, a broken bone, and then becomes infected with bacteria that spread easily in a hospital.
On one in 31 hospital patients have at least one infection that they contracted in a health care facility on a given day, according to the United States Centers for Disease Control and Prevention. And many of these pathogens are resistant to antibiotic treatment, which means the infection can progress to cause serious problems like pneumonia or sepsis.
So how can doctors treat patients infected with these bacteria?
It’s a question that gnawed at Edward geisinger when he was doing infectious disease rotations while in medical school. He saw many patients in intensive care units who had been infected with a bacteria called Acinetobacter baumannii, which is very resistant to antibiotics.
“I knew this was becoming a problem, but it was a poorly studied microbe at the time,” says Geisinger, now an assistant professor of biology at Northeastern. So, after completing his medical and doctoral courses, he began to study the bacteria in depth.
“Clinically, it causes pneumonia associated with people on ventilators and infections of the blood that can progress to sepsis,” he says. “Usually it infects the sickest people in the hospital. They’re really sick, so their whole immune system is sort of in trouble. And they are also connected to various devices, so the bodies have entry doors. “
Little was known about A. baumannii, beyond the havoc it could cause to patients, Geisinger’s research therefore initially focused on simply understanding how the bacteria could cause disease in a patient. The idea was to identify how the bacteria could escape detection by the immune system so that it could find a way to reveal it and prevent its sneak attacks.
It turns out that the bacteria can create a sort of concealment device, which Geisinger calls a “capsule” or “envelope.” This capsule is a kind of protective layer that allows the microbe to avoid being killed by the immune system.
Additionally, Geisinger’s research found that when the bacteria is exposed to antibiotics, it increases the production of this capsule layer to strengthen the protective shell. He also found that the wrong antibiotics can also cause the bacteria to go from being quite tame to quite aggressive in their ability to cause disease in a mouse, as well as becoming even more resistant to antibiotic treatment.
So what doesn’t kill A. baumannii indeed makes it stronger.
Geisinger found that two proteins work together to regulate the bacteria’s ability to strengthen the protective envelope against the immune system, resist antibiotic treatments, and increase its ability to cause disease. These two proteins are now where Geisinger has turned his attention, supported by a research grant his lab just received from the National Institutes of Health.
“The body is really dependent on these two proteins,” he says. “This is how the body protects itself. “
Geisinger’s goal is to find a way to inhibit the protein pair’s role in either developing new drugs or figuring out how to make current antibiotics more potent against A. baumannii.
“If we could target one of the proteins, we could kill the whole system and make the body more vulnerable,” he says. “If we can remove that layer of defense, we could hopefully expand the arsenal of treatments for this bug.”
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