News Scan for Aug 21, 2014

Controlling MRSA
;
Marburg virus drug trial
;
Vaccine-linked polio in Texas
;
A new animal model for MERS

Doubts raised about screening and isolation to control MRSA

It's time to reassess strategies for controlling methicillin-resistant Staphylococcus aureus (MRSA) in hospitals, mainly because of poor evidence for the efficacy of screening and isolation, which have been regarded as the gold-standard approach, say three German and Swiss experts writing in The Lancet.

There is little evidence from well-designed controlled studies to support the clinical efficacy of screening and isolation, especially in intensive-care units, but much more evidence for the efficacy of hand hygiene and universal decolonization, write Gerd Fatkenheuer, MD, Bernard Hirschel, MD, and Stephan Harbarth, MD.

They also observe that isolation reduces interactions between patients and caregivers, and say there is some evidence that this leads to increased adverse events and more depression and anxiety. Further, they note that MRSA rates have declined in recent years and that hospitals are battling several multidrug-resistant pathogens, raising questions about resource allocation.

"In view of the uncertainties about the efficacy of screening and the negative effects of contact isolation, the strategy of screening and isolation cannot be regarded as a gold standard to prevent the spread of MRSA in all health-care settings," the authors assert.

"In the haste to do something against the rising tide of MRSA infection, measures were adopted that seemed plausible but were not properly assessed, bundling the effective and harmless with the ineffective and harmful. No way has yet been identified to separate the grain from the chaff."

In a Lancet press release, co-author Harbarth of Geneva University Hospitals commented, "The lack of effectiveness of active detection and isolation should prompt hospitals to discontinue the practice for controlling the spread of MRSA in favour of evidence-based measures adapted to local conditions and settings. . . . What is more, recommendations and guidelines should clearly state the uncertainties in this field, and legal mandates that dictate the use of specific control measures for MRSA should be abandoned."
Aug 21 Lancet commentary (introduction)
Aug 20 Lancetpress release

 

Marburg virus drug shows promise in animal trial

A drug designed to treat Marburg virus infection, a cause of hemorrhagic fever in Africa, has been shown to protect nonhuman primates even when treatment is delayed until clinical illness sets in, researchers reported yesterday in Science Translational Medicine.

Outbreaks of filovirus illness, including Ebola virus disease (EVD), are becoming more frequent in Africa, and two Marburg infections were recently exported to Europe and the United States, according to an Aug 20 UTMB press release.

The study, which involved a lipid-encapsulated small interfering RNA treatment, was done by a group from the University of Texas Medical Branch (UTMB) at Galveston and collaborators at Tekmira Pharmaceuticals. Earlier studies on the drug looked at the drug's performance when given before the animals showed any sign of illness.

Twenty-one rhesus monkeys were challenged with a lethal dose of Marburg virus, of which 16 received the drug at four intervals after infection, ranging from 30 minutes to 3 days. All monkeys that got the drug survived, while the animals that were untreated or got a mock treatment died between 7 and 9 days after infection.

Ian MacLachlan, PhD, vice president and chief technical officer of Tekmira, said in the press release, "The significance of delaying treatment until 3 days after infection, which is the earliest time at which diagnosis by viral RNA can be detected and those infected show the first clinical signs of disease, is a critical step in triggering clinical interventions."
Aug 20 Science Trans Med study
Aug 20 UTMB press release

 

Report details Texas case of vaccine-linked polio in immigrant baby

Texas health officials and collaborators at the US Centers for Disease Control and Prevention (CDC) today described the 2013 detection of vaccine-associated paralytic polio (VAPP) and disseminated bacille Calmette-Guerin (BCG) infection in a 7-month old baby boy who had recently immigrated from India.

Health providers referred the baby to a hospital in San Antonio, where physical examination revealed symptoms that included fever and an enlarging skin lesion. The patient wasn't able to bear weight on the left leg and had progressing paralysis of that leg. Blood studies detected severe combined immunodeficiency syndrome (SCIDS), a rare congenital condition.

The child's history of oral polio virus (OPV) and BCG vaccination in India led to the diagnosis of VAPP and BCG-osis, which were confirmed by microbiologic testing. Both vaccines contain live attenuated organisms and are commonly used in developing countries, but not in the United States.

The authors noted that international travel poses a small risk of importing live attenuated vaccine organisms into the United States. They said the case shows the importance of recognizing the possibility in foreign children arriving from other countries and that vigilance for detecting vaccine-associated diseases can prevent the spread of the disease and ensure early treatment for patients.
Aug 21 MMWR report

 

Marmosets proposed as better animal model for studying MERS

Rhesus macaques have already been established as an animal model for MERS-CoV infection, but US researchers reported today that marmosets make a better model because they experience a severe illness resembling the disease often seen in humans.

Writing in PLoS Pathogens, scientists with the National Institute of Allergy and Infectious Diseases (NIAID) said that though macaques can be infected with the Middle East respiratory syndrome coronavirus (MERS-CoV), they show only mild or moderate symptoms, unlike many human MERS patients.

In their effort to find a better animal model, the researchers set out to find a species whose receptor protein on cells is similar to that in humans. They found that the receptor protein DPP4 (dipeptidyl peptidase 4) in marmosets—small monkeys found in South and Central America—closely matches its human counterpart.

When the researchers inoculated nine marmosets with MERS-CoV by multiple routes, the animals developed severe pneumonia, prompting euthanization of two of them under predetermined guidelines, the report says. All the marmosets had extensive lesions, inflammation, and high viral loads in their lungs, and some had virus in their blood as well.

"This is the first description of a severe, partially lethal, disease model of MERS-CoV, and as such will have a major impact on the ability to assess the efficacy of vaccines and treatment strategies as well as allowing more detailed pathogenesis studies," the report states.
Aug 21 PLoS Pathogens report
Aug 21 NIAID statement

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