Preventing Bacterial Infections from Medical Devices – Research Study Results

Preventing Bacterial Infections from Medical Devices – Research Study Results

This scanning electron micrograph shows a clump of Staphylococcus epidermidis bacteria (green) in the extracellular matrix, which connects cells and tissue. Image courtesy of NIAID/Rocky Mountain Laboratories.

From the US National Institutes of Health (NIH) Research Matters news release

New research has identified a protein that helps bacteria break away from medical devices like catheters and spread throughout the body. The finding gives insight into how bacterial communities called biofilms cause disease and provides a potential target for future treatments.

Biofilms are complex, multi-layered microbial communities. They can form on biological surfaces like teeth, or on medical devices that are placed inside a patient, like catheters. Bacteria in biofilms are resistant to antimicrobial agents and difficult to treat. Biofilms made up of Staphylococcus epidermidis bacteria are a major cause of infection in hospitals, and can lead to sepsis.

A research team led by Dr. Michael Otto of NIH’s National Institute of Allergy and Infectious Diseases (NIAID) set out to determine how bacteria from biofilms detach and disperse. They looked at a protein released by S. epidermidis called phenol-soluble modulin beta, or PSMβ. They chose PSMβ because of its structure, which hinted that it might act like a type of molecule, called a surfactant, that can help bacteria spread.The scientists first confirmed that S. epidermidis in biofilms make PSMβ protein. Then, to test whether the protein promotes biofilm formation, they cultured mutant bacteria that can’t make their own PSMβ. They found that adding medium levels of PSMβ to the cultures led to more biofilm formation, but high levels led to less. This suggested that PSMβ may play a dual role, helping biofilms form while also helping bacteria detach from them.

To look at detachment more directly, the researchers genetically engineered bacteria to turn green upon making PSMβ. When examined under a microscope, the bacteria making PSMβ were seen mostly at the outer layers of the biofilm, or detached and floating in fluid. Moreover, a strong green signal usually appeared just before bacteria disappeared from that area. This suggested that bacteria made PSMβ immediately before leaving the biofilm.

To see if PSMβ could help bacteria spread in a living organism, the team put 2 catheters in mice. One catheter had normal S. epidermidis on it. The other had a mutant lacking PSMβ. Within a few days, the normal bacteria spread to the organs and body fluids, but the PSMβ-lacking bacteria barely migrated at all.

In an attempt to stop the bacteria from spreading, the team treated mice with antibodies against PSMβ. The antibodies prevented bacteria from spreading to all the organs except for the lymph nodes, where numbers were significantly reduced.

PSM proteins have also been found in other Staphylococcus species. Although this research is still in its early stages, it opens up new avenues for curbing biofilm-related infections. “This is very important particularly because it links this mechanism of biofilm detachment to spread of infection in vivo,” Otto says.

—by Allison Bierly, Ph.D.

 

New superbug genes sure to spread, U.S. expert says

New superbug genes sure to spread, U.S. expert says

From a December 15 Reuters Health News item by Maggie Fox

WASHINGTON (Reuters) – A little loop of genes that give bacteria the power to resist virtually all known antibiotics is spreading quickly and likely to cause doctors headaches for years to come, an expert predicted on Wednesday.

They come on the equivalent of a genetic memory stick — a string of genes called a transmissible genetic element. Bacteria, unlike higher forms of life, can swap these gene strings with other species and often do so with wild abandon.

This one is called New Delhi metallobeta-lactamase 1 or NDM-1 for short and Dr. Robert Moellering of Harvard Medical School and Beth Israel Deaconess Medical Center in Boston predicts it will cause more trouble in the coming years.

“What makes this enzyme so frightening is not only its intrinsic ability to destroy most known beta-lactam antibiotics but also the company it keeps,’ Moellering wrote in a commentary in the New England Journal of Medicine.….

….

Antibiotic-resistant bacteria are nothing new — virtually all strains of the common Staphylococcus bacteria are now resistant to penicillin. Almost as soon as penicillin was introduced in the 1940s, bacteria began to develop resistance to its effects, prompting researchers to develop many new generations of antibiotics.

But their overuse and misuse have helped fuel the rise of drug-resistant “superbugs.” The U.S. Centers for Disease Control and Prevention says most infections that people get while in the hospital resist at least one antibiotic.

[Click here for the CDC Web page on Antibiotic Resistance
It contains detailed information under topics as About Antimicrobial Resistance and Diseases/Pathogens Associated with Antimicrobial Resistance.
References and Resources includes information on campaigns and surveillance systems as well as links to related podcasts, e-cards, and videos.  There are also links to government and organizational Web sites.

KILLER MRSA

For example, half of all Staphylococcus aureus infections in the United States are resistant to penicillin, methicillin, tetracycline and erythromycin. Methicillin-resistant staph aureus or MRSA killed an estimated 19,000 people in the United States alone in 2005.

NDM-1 resists many different types of antibiotic. In at least one case, the only drug that affected it was colistin, a toxic older antibiotic.

“Thus far, the majority of isolates in countries throughout the world can be traced to subjects who have traveled to India to visit family or have received medical care there,” Moellering wrote.

“However, the ability of this genetic element to spread rapidly among Enterobacteriaceae means that there will almost certainly be numerous secondary cases throughout the world that are unrelated to travel to the Indian subcontinent.”

Experts have been warning for years that poor hospital practices and the overuse of antibiotics spread dangerous bacteria, but practices are changing only slowly.

“The fact that there is widespread nonprescription use of antibiotics in India, a country in which some areas have less than ideal sanitation and a high prevalence of diarrheal disease and crowding, sets the ideal stage for the development of such resistance,” Moellering wrote….