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Rosemary
United Kingdom
2028 Posts |
 Posted - 04/16/2008 : 10:44:07
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http://www.pharmiweb.com/pressreleases/pressrel.asp?ROW_ID=3612
New Staph vaccines: risk-based or population-based approach?
VacZine Analytics
Posted on: 12 Apr 08
New research conducted by VacZine Analytics focused on methicillin- resistant
Staphylococcus aureus (MRSA) highlights continued expert concerns regarding
the transmission of the pathogen in the community (CA-MRSA) as well as
hospital settings (1). For vaccine manufacturers the research raises the
question of whether new vaccines should cover antigens specific to CA-MRSA
and whether they should be positioned as part of a wider population-based
approach beyond “at risk” groups.
Staphylococcus aureus or “Staph” is a ubiquitous gram-positive bacterium
which colonizes around 20-30% of normal healthy humans. It resides on the
skin and mucosal surfaces such as the nose and perineum. Ordinarily the
bacterium is harmless but in certain cases when it enters the body it can
cause serious disease. Staph is a major cause of skin and soft tissue
infections (SSTIs), bone infections, endocarditis and bacteremia (blood
poisoning, sepsis) all of which can have fatal outcomes.
Many in the “lay” population have heard of the drug resistant form of Staph
known as MRSA which stands for methicillin- resistant Staphylococcus aureus.
MRSA was first identified in the early 1960s and has presented great
challenges to physicians especially in intensive care units (ICUs) of
hospitals. In ICUs patients are critically ill often recovering from trauma
(burns) and deeply invasive procedures, for example, after cardiothoraic
surgery, orthopaedic surgery and transplant procedures. Because ICU patients
are commonly elderly and/or immunocompromised they are susceptible to
post-operative wound/surgical site infections, bacteremia and pneumonia. In
some cases these infections are initiated by a self-colonizing strain of
Staph. If the resultant infection is caused by MRSA (around 50% of cases),
it is associated with greater length of hospital stay, higher mortality and
greater costs. In 2005, the US Centers for Disease Control and Prevention
(CDC) estimated that around 94,000 people had an invasive MRSA infection of
which 18,650 died in a hospital setting (2).
Although there are a number of drugs such as vancomycin, linezolid and
daptomycin approved for the treatment of serious hospital-acquired MRSA
infections, many experts agree that evolving bacterial resistance will
remain a continuous threat. Experts therefore strongly advocate the use of
complimentary risk-avoidance strategies. For example, it is documented that
one of the main sources of cross-transmission of Staph is via the hands of
healthcare workers, a source that can be prevented by strict hygiene
measures. Other evolving strategies involve the “swabbing” of patients due
to be hospitalized to check for MRSA colonization so as to guide downstream
management. In some countries such as Holland and those in the Nordic region
these techniques of patient isolation along with strict antibiotic
prescribing policies have resulted in very low rates of MRSA when compared
to countries such as the US and UK.
In recent years the threat of MRSA has also become apparent outside of the
hospital setting with the recently described phenomenon of
community-acquired MRSA (CA-MRSA). For example, in the US, outbreaks of
CA-MRSA have occurred in diverse populations such as American Indian,
Alaskan Natives, sportsmen, prisoners and healthy children. A 2007 study
published in JAMA estimated that of 8967 observed cases of invasive MRSA,
around 13-14% were community-associate d (3). CA-MRSA mostly causes treatable
skin and soft tissue infections but in some cases can be responsible for
severe necrotizing disease e.g. Pneumonia which follows a rapid, often fatal
course.
CA-MRSA isolates are epidemiologically distinct from strains transmitted in
the hospital (HA-MRSA). Although they tend to be resistant to fewer classes
of antibiotics they are “fitter” and more virulent producing more toxins
including the notable Panton Valentine Leukocidin (PVL) necrotic cytotoxin
(PVL) observed in the epidemic strain USA300. When interviewed, experts were
most concerned that PVL+ CA-MRSA could cause rapid disease in individuals
with no discernible risk factors and no recent contact with healthcare
facilities. More importantly, they felt incidence was rising and that more
could be done to equip primary care physicians to recognize and treat
CA-MRSA skin infections which are often confused with “spider bites”.
Because of these concerns and urgency to update wider understanding of
CA-MRSA, healthcare policy makers are now focusing on educating primary care
physicians. A good example is in the UK where a new set of treatment
guidelines for dealing with CA-MRSA infections are soon to be published (4).
As well as drug treatments and risk-avoidance strategies, interviewed
experts believed that the development of a Staph preventative vaccine was
also worthwhile pursuit. Such a vaccine could prevent the incidence of Staph
bacteremias, wound infections or in the ideal scenario, nasal carriage
possibly after decolonization with the antibiotic murpirocin. Despite the
high profile of US-based NABI’s Type 5/8 polysaccharide conjugated vaccine
in 2005 (Phase III), it is clear that the field is again resurgent with
Merck & Co currently testing a single antigen vaccine (Phase II) in
end-stage renal disease (ESRD) and cardiothoraic patients scheduled for
surgery. Merck & Co appropriated the vaccine antigen from Vienna based
Intercell AG in an exclusive arrangement prior to its strategic alliance
with Novartis Vaccines. Presently it is the most advanced program with
expected filing in 2012-14.
Aside from the effort at Merck & Co many believe that in order for a Staph
vaccine to be effective it should contain a mixture of antigens, some
specific to CA-MRSA isolates. NABI are seemingly capitalizing on this latter
concept by relaunching a pentavalent StaphVAX effort which contains
additional antigens such as PVL, Type 336 and alpha toxin. In addition, a
recent analysis of vaccine preclinical intellectual property (5) indicates
that other major companies such as GSK Biologicals and Novartis Vaccines are
also pursuing Staph vaccine technologies.
According to the experts one key challenge for future Staph vaccines will be
choosing the “right” antigens. Staph causes a wide spectrum of diseases and
expresses many antigens during different growth conditions with numerous
factors involved in pathogenesis, adherence and biofilm formation. While
newer antigens such as Poly-N-acetyl glucosamine (PNAG), Fibronectin Binding
Protein (FBP) and Staph heteropolymer have yielded some promising
preclinical data many antigens are simply biological “red herrings” (1).
A wider challenge beyond the technical aspects of Staph vaccine development
will be choosing the appropriate future vaccination strategy. Presently it
does seem logical to protect defined groups at high risk from Staph
bacteremias; however, many experts believe that in terms of overall societal
burden, preventing Staph SSTIs and reducing carriage should also be high
priorities. Lessening these would involve some form of population-based
vaccination with one US expert venturing that a Staph vaccine should be on
the pediatric schedule. Opponents to this ambitious concept are likely to
raise the issue of cost and the fear of “over vaccination” but at least in
immunological terms potential vaccinees could be protected for life having
sufficient time to develop protective immunity. The present evolving
strategy of vaccinating patients to be hospitalized needs a rapid acting
vaccine. Based on this research VacZine Analytics believes it should be
considered the starting point of something bigger.
References:
1) Community-acquired CA-MRSA. OpportunitySCAN (CAT: VAOPS002). Published
April 2008.
2) US Centers for Disease Control and Prevention. Invasive MRSA. Fact Sheet.
Available at http://www.cdc.gov/ncidod/dhqp/ar_mrsa_Invasive_ FS.html.
Accessed April 2008.
3) Klevens RM., et al. Invasive methicillin- resistant Staphylococcus aureus
in the United States. JAMA 2007; 298 (15): 1763-1771.
4) UK Opinion Leader. Personal communication to VacZine Analytics
5) Vaccine Preclinical IP Review. VacZine Analytics (CAT: VAVS007). To be
published May 2008. |
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Rosemary
United Kingdom
2028 Posts |
Posted - 04/20/2008 : 13:48:52
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http://www.naturalnews.com/023051.html
U.S. hospitals plagued by surprisingly high level of MRSA superbug infections
Friday, April 18, 2008 by: David Gutierrez | Key concepts: MRSA, hospitals and superbug
(NaturalNews) Nearly 5 percent of patients in U.S. hospitals may have acquired a particular antibiotic resistant staph infection, according to a nationwide survey conducted by the Association for Professionals in Infection Control and Epidemiology (APIC).
Researchers surveyed a total of 1,200 hospitals and other health care facilities from all 50 states, and found 8,000 patients infected or colonized with methicillin-resistant Staphylococcus aureus (MRSA) -- or 46 out of every 1,000. This suggests that up to 1.2 million hospital patients across the country may be infected every year.
Colonized patients are those who were found to be carrying the bacteria in or on their bodies, but who had not showed any symptoms of disease.
"This rate is between eight and 11 times greater than previous MRSA estimates," APIC wrote.
The majority of the infections had originated within the medical facility; 67 percent arose in patients being treated for general medical conditions (such as diabetes or pulmonary or cardiovascular problems) and not in intensive care patients.
APIC recommended simple measures, such as hand washing, to prevent the spread of MRSA within medical institutions. A number of studies have shown that many health care workers are not appropriately vigilant about washing their hands consistently.
"Hand hygiene is the most important means of preventing the spread of infection," said APIC President Denise Murphy.
MRSA is resistant to all forms of penicillin, which has earned it the moniker of "superbug." Due to its drug resistance, it is twice as fatal as other staph infections.
In 1974, the Centers for Disease Control and Prevention estimated that 2 percent of the staph infections occurring in medical facilities were cases of MRSA; in 2004, the estimate had risen almost to 63 percent.
Worldwide, approximately 2.7 percent of S. aureus carriers are estimated to be infected or colonized with MRSA |
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New Staph Vaccines
