March 12, 2012 — Clostridium difficile is an important healthcare-acquired pathogen that is responsible for a number of diseases of the intestines, including Clostridium difficile-associated disease (CDAD). Contact Precautions, diligent hand washing (with soap and water), and cleaning of environmental surfaces are typically required to control and prevent its transmission.
An opportunistic, spore-forming, gram-positive, anaerobic bacillus, C. difficile is transmitted from one patient to another through direct or indirect contact—namely, through the oral ingestion of its vegetative cells or endospores (i.e., the fecal-oral route). Its primary reservoirs are infected (and colonized) patients in hospitals and long-term care facilities.
The hands of healthcare workers, which may become transiently colonized with C. difficile, are the primary sources of this spore-former, although to a less and more controversial extent environmental surfaces, on which endospores of C. difficile can survive for weeks or months, also appear to play a role in the healthcare-acquired transmission of C. difficile.
Capitalizing on concerns in the gastrointestinal (GI) community about the potential for patient-to-patient transmission of C. difficile during GI endoscopy, some reports (erroneously) suggest that:
- high-level disinfection is an unrealized risk factor for disease transmission;
- some marketed high-level disinfectants are inferior to others and may be responsible for the formation of biofilms and an increased risk of transmission of different types of infectious agents including C. difficile during GI endoscopy; and/or
- “sterilization” of GI endoscopes or the use of a non-aldehyde high-level disinfectant is necessary to prevent the transmission of C. difficile.
While it is true that some high-level disinfectants may require a longer exposure time than others to destroy B. subtilis and C. sporogenes, neither of these two spore-forming bacteria are pathogenic. Further, not all types of spore-forming bacteria are alike or require either prolonged immersion in a high-level disinfectant or sterilization for their destruction.
Not only does high-level disinfection completely destroy vegetative cells and endospores of C. difficile, but 2% (alkaline) glutaraldehyde has been documented to destroy C. difficile in less than 10 minutes (at 20 o C).
These are significant findings, because not only are almost all GI endoscopes high-level disinfected between uses, but more than ten million GI endoscopic procedures are performed each year in the U.S.
Although outbreaks of C. difficile have been reported in hospitals and long-term care facilities, none has been reported in the GI endoscopic setting. There are no reports of a GI endoscope transmitting C. difficile or another type of pathogenic spore-forming bacterium. Nor have any published studies demonstrated that one type of high-level disinfectant is associated with a higher risk of disease transmission than another.
Biofilms have been linked to healthcare-associated infections following flexible endoscopy, but these biofilms were produced by non-spore-forming bacteria, such as Pseudomonas aeruginosa—not by C. difficile or another spore-forming bacterium.
And, the causes of these biofilms and infections were atypical and due to, for example, a manufacturing defect of a recalled bronchoscope model, the flawed design of an automated endoscope reprocessor (AER), or the damaged channel of an endoscope.
High-level disinfection of GI endoscopes—whether achieved using an aldehyde-based or other type of germicide—prevents transmission of all types of pathogenic microorganisms encountered in the GI endoscopic setting, including C. difficile.
Moreover, patients on whom colonoscopy is performed and who are “positive” for C. difficile may have been infected or contaminated (e.g., colonized) with this bacterium while previously receiving care at a hospital or a long-term care facility, or they acquired it from the community (i.e., community-acquired infection), not during GI endoscopy from a contaminated instrument. Risk factors for infection include Crohn’s disease and the administration of antibiotics.
Article by: Lawrence F Muscarella PhD
References:
1. Muscarella LF. C. difficile, Biofilms: Has this spore-former been transmitted during GI endoscopy? The Q-Net Monthly 2007 Nov;13(11);21-22.
2. Ananthakrishnan AN. Clostridium difficile infection: epidemiology, risk factors and management. Nature Reviews Gastroenterology and Hepatology 8, 17-26 (January 2011).
What is the ratio of Cdiff spores to vegetative cells in the colon? It seems to me there is little reason for spore formation in the colon. In fact this is anaerobe heaven. You have thousands times more anaerobes than facultative bacteria. No stressful conditions that would induce spore formation. Once placques of Cdiff have established on the surface vary little will harm the vegetative cells. Stressed cells changing into spores would not be finished in their transformation until after exiting the host in the stool. So what is the ratio of spores to vegetative cells in formed stool and in stool from a patient during symptomatic CDI?
Mr. Deneau, Thank you for your comments and question; they are well-taken. I do not know the ratio of Clostridium difficile spores to vegetative cells, but in the colon, recently formed stool or from the stool of a patient with Cl. difficile infection, each rife with nutrients, this ratio would be expected to be quite low. Further, if a GI endoscope were to be contaminated with Cl. difficile during colonoscopy, this organism would be primarily, if not solely, in its vegetative state, which, notably, is readily destroyed by high-level disinfection (if not intermediate-level disinfection). Briefly, sporulation (the formation of spores from the vegetative cells of a spore-forming bacterium such as Cl. difficile) is expected over time when the environmental conditions become adverse or extreme – or, to use your apt word: “stressed,” – thereby challenging the organism’s survival. No instances of patient-to-patient transmission of Cfl. difficile have been reported during lower GI endoscopy.