Study reveals how superbugs trick immune system

Reuters   11-12-7

WASHINGTON - Drug-resistant bacteria called methicillin-resistant Staphylococcus aureus, or MRSA, may be able to first lure and then destroy immune system cells when they are the most vulnerable, researchers said on Sunday.

The study may help explain why MRSA spread outside of hospitals are harder to fight and seem to be spreading more easily.

But the findings may also lead to new and better antibiotics to fight the bacteria, the researchers reported in the journal Nature Medicine.

 

Magnified image of a cluster of drug-resistant staphylococcus aureus bacteria.

"This elegant work helps reveal the complex strategy that S. aureus has developed to evade our normal immune defenses," Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said in a statement.

 

 

"Understanding what makes the infections caused by these new strains so severe and developing new drugs to treat them are urgent public health priorities."

 

The NIAID's Michael Otto and colleagues found that some strains on MRSA secrete a compound called phenol-soluble modulin or PSM. It attracts immune system cells called neutrophils, the researchers found, and then blows them up in a process called lysis.

 

S. aureus is common and usually only causes pimples or boils, although infections can spread to surrounding tissue.

MRSA is treatable only with a few antibiotics. It is common in hospitals, where it can killed weakened patients.

"Recently there has been an alarming epidemic caused by community-associated (CA)-MRSA strains, which can cause severe infections that can result in necrotizing fasciitis or even death in otherwise healthy adults outside of healthcare settings," Otto's team wrote in their report.

 

Necrotizing fasciitis is the so-called flesh-eating disease that can destroy healthy tissue and even kill patients.

"In the United States, CA-MRSA is now the cause of the majority of infections that result in trips to the emergency room. It is unclear what makes CA-MRSA strains more successful in causing human disease compared with their hospital-associated counterparts," they added.

 

"Here we describe a class of secreted staphylococcal peptides that have a remarkable ability to recruit, activate and subsequently lyse human neutrophils, thus eliminating the main cellular defense against S. aureus infection."

Neutrophils are key immune cells involved in clearing bacterial infections, so destroying them would allow the bacteria to thrive almost unmolested.

 

"We're not saying the PSM-alpha gene cluster is the only element contributing to the virulence and survival of CA-MRSA, but it is a major factor," Otto said in a statement.

 

In October researchers reported that MRSA was far more common than had been known, with 94,000 hospitalizations and almost 19,000 deaths in 2005 in the United States.

Same Hong Kong hospital where SARS originated has highest rate of “Superbug"-infected infants 

 By Judi McLeod    CanadaFreePress.com   11-13-2007

Kwong Wah Hospital in Hong Kong already had 33 “superbug"-infected infants by the time Issue No. 921 of Next Magazine reported that six babies had contracted the “superbug” in its November 1 issue.

Like the scenes out of horror movie Outbreak coming true, Staphylococcus aureus ("Golden Grapes bacteria") is on the loose in some world hospitals and is making the trek to community schools.  But Kwong Wah, with the highest rate of infant infection among all the hospitals in Hong Kong, remains off the world radar screen. Next Magazine cites the cause as Kwong Wah Hospital’s location.  It happens to be located in a district much easier for Mainland Chinese pregnant female “tourists” to be admitted under “emergency” to deliver “born-in-Hong Kong” babies.  Having babies there helps qualify them for future residence in Hong Kong, the magazine reports.

Keeping records rates up there with hygiene in making efforts to control Golden Grapes bacteria, but pregnant women admitted to Kwong Wah Hospital never went there for prenatal medical examinations and supply no medical reports.

Even as the global medical community is on high alert in the superbug scare, a Hong Kong hospital remains in the dark about its own patient admissions.

This is the second time that Kwong Wah Hospital, which was also the origin of the 2003 SARS outbreak, has been catapulted into headlines.

Although the story was originally downplayed, 64-four-year-old Professor Liu Jian Lun, world renowned microbiologist working to find a cure for H5N1, was rushed to Kwong Wah Hospital early in the morning of March 4, 2003, where he died of SARS.

In a September 28, 2007 story in Ming Pao Daily News, six babies at Kwong Wah Hospital were reported to be showing symptoms of infection-resistant Staphylococcus aureus (MRSA).  All six babies were reported to have recovered.

Seen through the microscope, staphylococcus aureus has round cells that look like an inviting cluster of golden grapes, from which the deadly bacteria takes its name.

Antibiotics increasingly do not work against superbugs, which roam hospitals freely, spreading by contact on the hands of a doctor or nurse, on a stethoscope or bed railing.  The more resilient they become, the greater the threat.

Strict hygiene is the best antidote, but strict hygiene is often at high risk to human error in busy environments, where emergency is a factor.

While medical facilities fight to keep the “Go-to-hospital-and-die” panic under control, Kwong Wah Hospital should be forced under the public microscope.

According to CNNMoney.com, “Hospitals typically veil deaths from such infections in generalities.  When an obituary reports the cause of death as “complications from surgery”, it most likely means multi-drug-resistant S. aureus.” (Sept. 30, 2002).  The Centers for Disease Control and Prevention reckons that of ten million Americans entering hospitals each year, 40,000 will die as a result of bacterial infections contracted during their stay--as many as die in car wrecks and twice the number who die of AIDS.  S. aureus accounts for the bulk of those hospital deaths.”

The frightening story about deadly microbes is that superbugs are proving resistant not only to every drug in the penicillin family--by now, penicillin-resistant infections in hospitals have become routine--but also to all variants of methicillin, a drug once touted as the replacement for penicillin.

Ironically, the future could be taking us back to the pre-penicillin past when unstoppable infections killed the majority of seriously ill hospital patients.  In that dark chapter of hospital history some 60 years ago, S. aureus was the main bug claiming human life.

Authorities in cities the world over are telling people there is no need to panic; that the old and infirm are most at risk.  While it is true that many superbug victims are old, suffering from chronic conditions that weaken their immune systems, trauma patients--victims of car crashes or bad burns--are also especially vulnerable, as are cancer patients in for radiation or chemotherapy--and newborns.

When 78-year-old grandmother, Kwan Sui-Chu returned to Toronto from Hong Kong in February 2003, no one had heard of the deadly SARS with which she was infected.  In Hong Kong she and her husband had stayed on the ninth floor of the Metropole Hotel at the same time as a Chinese professor of respiratory medicine, Liu Jian Lun, now known as the case that triggered the coming global epidemic.

Meanwhile, Golden Grapes Bacteria has jumped from hospitals and schools to the farm.

“A new study published in Veterinary Microbiology found methicillin-resistant Staphylococcus aureus (MRSA) is widely common in Canadian pig farms and pig farmers, signaling to some that animal agriculture is a source of the deadly bacteria.” , Nov. 6, 2007).  “The Veterinary Microbiology study (Khanna et al 2007) is the first to show that North American pig farms and farmers commonly carry MRSA.