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Clostridium difficile Infection Prevention (Part 2)

Barry Michaels
December 19, 2012
Clostridium difficille Associated Infections

A couple weeks ago the Deb Hand Hygiene blog focused on typical environmental targets necessary for the control of Clostridium difficile (C diff) within healthcare settings.  With this blog posting various aspects of what some would consider the most important key strategy component, hand hygiene will be discussed.  Currently C. difficile is believed to infect up to 30% of individuals admitted to US hospitals resulting in what the CDC estimates to be some 14,000 deaths annually. Worldwide concern has been expressed with regard to the emergence of hyper-virulent strains, responsible a disease having increased severity and alarmingly greater resistance to antibiotics. Last week the BBC ran an excellent article in it's online news detailing what we are up against.

 

Environmental cleaning and disinfection is, as pointed out previously, important in reducing the risk of Clostridium difficile Infection but even more basic is adherence to strict hand hygiene (handwashing & sanitizer) including glove use protocols when conditions dictate.  C. difficile is a normal commensal bacterium of the human gut with 2-5% of adults and up to 50% of healthy neonates as carriers. This microorganism has adapted for transmission from person to person via the classic fecal-oral route. Human hosts become particularly susceptible after disruption of normal gut flora by antibiotic or antineoplastic therapy.

 

Hospitals or long term care facilities serve as reservoirs with current model being (a) otherwise C diff free individual being hospitalized, (b) given antibiotic or antineoplastic therapy (c) being exposed to and acquiring C. difficile (d) becoming colonized with C. difficile asymptomatically or (e) coming down with C. difficile Associated Disease/Diarrhea (CDAD) as toxins build up within patient generated by vegetative cells. C diff carriers while not at a risk to themselves, are responsible for distribution of spores, with each individually capable of surviving in the environment for periods of up to and beyond 70 days.

 

It is not uncommon to find the hands of healthcare workers with rates of colonization as high as 60%, following sometimes only limited patient contact. Direct and indirect evidence shows that person-to-person spread of C. difficile occurs by hand contact either through patient-to-patient contact or via healthcare providers often times involving cross-contamination via contaminated environmental surfaces.  A simple hand shaking has been shown to transfer a mean of 30% of spores or vegetative cells when hands are contaminated.

 

No single infection control practice has proven effective at control of CDAD, but rather multifaceted approaches to infection control involving both hand and surface hygiene have been shown successful. These consist of (a) glove use when sanitizing heavily contaminated surfaces and handling bodily fluids (b) handwashing between patients (c) isolation precautions & cohorting (d) environmental cleaning (e) restricted use of antibiotics etc.

 

Infection control measures, such as wearing gloves along with hand hygiene before and after glove change when caring for patients with CDAD, has been proven to be effective at prevention of infection transmission. Hand hygiene in healthcare settings according to existing international guidelines calls for washing of hands when visibly soiled, after contact with body fluids and use of alcoholic hand sanitizer after patient contact when not soiled.  Much has been made of the fact that alcohol sanitizers are not effective against C diff spores while at the same time effective at inactivating a wide range of microbial agents responsible for countless infections types.  But the picture is a little more complicated than that.   The message should not be “…alcohol doesn’t work so don’t use it” but rather, “1) C diff is not the only star in the universe, and 2) in the microbial world, it is ultimately always a numbers game and we should be happy for any help we can get”. 

 

C. difficile exhibits its pathology (CDAD) through strains that produce enterotoxins and these are only produced through multiplication of vegetative cells. Data is not readily available concerning counts of C. difficile vegetative cells and spores in infected adult fecal material but data available on infants find 5 Log10 to 7 Log10 cells per wet gram. These counts fit within what is known for microbial counts of other enteric pathogens and non-pathogens in stool.  In sampling of stool from healthy adults those showing C. difficile spores alone or vegetative cells alone appear to be only around 10% with the majority having mixtures of spores and vegetative cells.

 

Spore counts of infected patients having detectable enterotoxin levels show C. difficile spore numbers of <5 Log10/g of feces. Since there is an inverse correlation between toxin level and spore count likewise when spore counts are  <5 Log10/g, vegetative cell numbers are in the realm of 7 Log10/g.  Toxin production and sporulation represent opposite alternative survival strategies.  So based on this data, we need to wear gloves to minimize hand contamination. 

 

Gloves should also be worn while sanitizing target environmental surfaces.  This brings contaminated hand counts into a magnitude where standard hand hygiene (with or without antimicrobial ingredients) can have a chance of success.  Removal of C. difficile from hands (with approximately 50% spores) or gloved hands has shown to be somewhat equally effective (from about 1.6 to 2.5 Log10) by simple soap or CHG solution (4% CHG & 4% alcohol). The mechanical action of hand washing and chemical activity of soap by way of surfactant action are effective at removal of spores and vegetative cells. The standard protocol alcohol sanitizer can then eliminates any remaining vegetative cells.

 

In addition to use of sanitizing solutions, both bleach wipes containing 0.55 percent sodium hypochlorite and wipes containing Accelerated Hydrogen Peroxide (AHP) have been shown to kill the spores and prevent transmission between patients.  Control strategies have increasingly relied on use of products incorporating AHP due to reduced concerns for human and environmental toxicity.  Surface sanitizers are required to have kill rates of at least 5 Log10 for the contact times indicated on labels.  Looking at the possible combined kill levels of surface sanitization and glove use along with something in the neighborhood of 2 Log10 for hand hygiene followed by alcohol hand sanitizer, it can be seen that we are within the striking distance of the 7 Log10 spores or vegetative cells per gram and thus the chain of infection is or can be broken. These are the numbers showing proof of concept and help explain proven clinical success. Fighting C diff mano a mano (hand to hand) is possible but hand washing and glove use takes on greater significance because you cannot lean on the incredible effectiveness of a good hand sanitizer to prevent transmission.

 

I, similar to the World Health Organization take the position that whether alcohol sanitizers are active against C diff spores or not, the real issue is compliance to existing guidelines. We should not divert our attention from a well constructed hand hygiene safety program (gloves, hand washing and alcohol sanitizer) potentially discouraging some healthcare professionals from using a proven intervention strategy, effective against a wide range of infective agents.   Even here when going against the difficult C diff foe, we sometimes get lucky with sanitizers and kill more than a few vegetative cells at a time bringing us ever closer to our goal.  Now this is something to shake hands about.

 

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