Navigation Links
Bacterial toxins cause deadly heart disease

University of Iowa researchers have discovered what causes the lethal effects of staphylococcal infective endocarditis - a serious bacterial infection of heart valves that kills approximately 20,000 Americans each year.

According to the UI study, the culprits are superantigens -- toxins produced in large quantities by Staphylococcus aureus (staph) bacteria - which disrupt the immune system, turning it from friend to foe.

"The function of a superantigen is to 'mess' with the immune system," says Patrick Schlievert, Ph.D., UI professor and chair of microbiology at the UI Carver College of Medicine. "Our study shows that in endocarditis, a superantigen is over-activating the immune system, and the excessive immune response is actually contributing very significantly to the destructive aspects of the disease, including capillary leakage, low blood pressure, shock, fever, destruction of the heart valves, and strokes that may occur in half of patients."

Other superantigens include toxic shock syndrome toxin-1, which Schlievert identified in 1981 as the cause of toxic shock syndrome.

Staph bacteria is the most significant cause of serious infectious diseases in the United States, according to the Centers for Disease Control and Prevention (CDC), and infective endocarditis is the most serious complication of staph bloodstream infection. This dangerous condition affects approximately 40,000 people annually and has a death rate of about 50 percent. Among patients who survive the infection, approximately half will have a stroke due to the damage from the aggressive infection of the heart valves.

Despite the serious nature of this disease, little progress has been made over the past several decades in treating the deadly condition.

The new study, led Schlievert, and published Aug. 20 in the online open-access journal mBio, suggests that blocking the action of superantigens might provide a new approach for treating infective endocarditis.

"We have high affinity molecules that neutralize superantigens and we have previously shown in experimental animals that we can actually prevent strokes associated with endocarditis in animal models. Likewise, we have shown that we can vaccinate against the superantigens and prevent serious disease in animals," Schlievert says.

"The idea is that either therapeutics or vaccination might be a strategy to block the harmful effects of the superantigens, which gives us the chance to do something about the most serious complications of staph infections."

The UI scientists used a strain of methicillin resistant staph aureus (MRSA), which is a common cause of endocarditis in humans, in the study. They also tested versions of the bacteria that are unable to produce superantigens. By comparing the outcomes in the animal model of infection with these various bacteria, the team proved that the lethal effects of endocarditis and sepsis are caused by the large quantities of the superantigen staphylococcal enterotoxin C (SEC) produced by the staph bacteria.

The study found that SEC contributes to disease both through disruption of the immune system, causing excessive immune response to the infection and low blood pressure, and direct toxicity to the cells lining the heart.

Low blood flow at the infection site appears to be one of the consequences of the superantigen's action. Increasing blood pressure by replacing fluids reduced the formation of so-called vegetations plaque-like meshwork made up of cellular factors from the body and bacterial cells -- on the heart valves and significantly protected the infected animals from endocarditis. The researchers speculate that increased blood flow may act to wash away the superantigen molecules or to prevent the bacteria from settling and accumulating on the heart valves.


Contact: Jennifer Brown
University of Iowa Health Care

Related biology news :

1. UC Davis researchers discover molecular target for the bacterial infection brucellosis
2. Newly discovered bacterial partnership changes ocean chemistry
3. Bacterial blockade
4. Study finds depletion of alveolar macrophages linked to bacterial super-infections
5. New methods to visualize bacterial cell-to-cell communication
6. UT study: Chemical in antibacterial soaps may harm nursing babies
7. Spinning up antibacterial silver on glass
8. Bacterial DNA may integrate into human genome more readily in tumor tissue
9. HIV-derived antibacterial shows promise against drug-resistant bacteria
10. Metabolic model of E. coli reveals how bacterial growth responds to temperature change
11. Bacterial security agents go rogue
Post Your Comments:
(Date:5/23/2017)... 2017  Hunova, the first robotic gym for the rehabilitation and functional ... in Genoa, Italy . The first 30 robots will ... USA . The technology was developed and patented at ... IIT spin-off Movendo Technology thanks to a 10 million euro investment from ... click: ...
(Date:4/19/2017)... 2017 The global military biometrics ... marked by the presence of several large global players. ... five major players - 3M Cogent, NEC Corporation, M2SYS ... nearly 61% of the global military biometric market in ... global military biometrics market boast global presence, which has ...
(Date:4/11/2017)... PALM BEACH GARDENS, Fla. , April 11, ... biometric identity management and secure authentication solutions, today ... million contract by Intelligence Advanced Research Projects Activity ... technologies for IARPA,s Thor program. "Innovation ... the onset and IARPA,s Thor program will allow ...
Breaking Biology News(10 mins):
(Date:10/11/2017)... , ... October 11, 2017 , ... ... announced today it will be hosting a Webinar titled, “Pathology is going digital. ... Associates , on digital pathology adoption best practices and how Proscia improves lab ...
(Date:10/11/2017)... Florida (PRWEB) , ... October 11, 2017 , ... ... Drug Administration (FDA) has granted orphan drug designation to SBT-100, its novel anti-STAT3 ... for the treatment of osteosarcoma. SBT-100 is able to cross the cell membrane ...
(Date:10/10/2017)... research firm Parks Associates announced today that Tom Kerber ... Annual Meeting , October 11 in Scottsdale, Arizona . ... how smart safety and security products impact the competitive landscape. ... Parks Associates: Smart Home Devices: Main Purchase Driver ... "The residential security market has experienced continued growth, and the ...
(Date:10/9/2017)... ... October 09, 2017 , ... The award-winning American Farmer television series will feature ... Farmer airs Tuesdays at 8:30aET on RFD-TV. , With global population estimates nearing ... how to continue to feed a growing nation. At the same time, many of ...
Breaking Biology Technology: