A wide variety of other bacteria, viruses, fungi and protozoa could potentially be transmitted by endoscopy. Relatively little investigation has been undertaken in this area although candidal infection of immunocompromised patients has been reported. An epidemic of pseudoinfection with the yeast Rhodotorula rubra has been reported in bronchoscopy patients.
The sensitivity of many unusual organisms to chemical disinfectants is largely unknown. However some agents such as the oocysts of Cryptosporidia are highly resistant to a variety of chemical disinfectants including 2% glutaraldehyde. It is unlikely that such organisms pose a significant threat to patients with normal immune systems but they could be responsible for serious and even fatal infections in the immunocompromised.
Meticulous mechanical cleaning has been shown to remove approximately 104 organisms of Cryptosporidium parvum and this combined with the fact that C. parvum viability is reduced by 103 within 30 minutes on dry surfaces indicates that a properly processed endoscope does not pose a risk of transmitting this organism.
This is a proteinaceous infectious agent or prion protein, which accumulates in neural cells. No prion-specific nucleic acid is known to b required for transmission of disease.
Transmissible spongiform encephalopathies (TSEs), also known as prion diseases are fatal degenerative brain diseases that occur in humans and certain animal species. These diseases are characterised by the accumulation of a modified prion protein in the grey matter of the brain.
Human TSEs occur in sporadic, familial, iatrogenic and variant forms and they include:
Sporadic disease accounts for 90% of known cases and the mode of acquisition and/or transmission is not known. Less than 10% of cases are familial. The "variant" CJD disease (vCJD) has been connected to beef contaminated with the bovine spongiform encephalopathy (BSE) agent. There have been no reports of vCJD in Australia.
Iatrogenic CJD has been described in humans in 3 circumstances:
The risk of CJD transmission is a function of the infectivity of the particular tissue, which relates to the concentration of the abnormal prion protein in that tissue.
Standard Precautions should apply to the routine management of patients. Additional precautions may be required for reprocessing some surgical instruments used for high risk patients. These are discussed in detail in section 31 of the CDNA Infection Control Guidelines.
TSE agents exhibit an unusual resistance to conventional chemical and physical decontamination methods. In addition, the catastrophic nature of the disease has engendered such an emotional response that many recommended risk containment strategies have been grossly excessive. It again needs to be stressed that no iatrogenic or occupationally acquired CJD has occured from exposure to low or no risk tissues.
Accordingly to the tissues listed in the categories above endoscopes would be contaminated only with material from the "no detectable infectivity" category. This would indicate that standard cleaning and high-level disinfection protocols would be adequate for reprocessing. Although there is an assumption there is no risk, generally a cautious approach is taken in this situation.
The recommendations that are consistent with the CDNA guidelines are:
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© The State of Queensland (Queensland Health) 2008.