All lumens and channels of endoscopic instruments must contact the disinfectant. Air pockets interfere with the disinfection process, and items that float on the disinfectant will not be disinfected.
The disinfectant must be introduced reliably into the internal channels of the device. The exact times for disinfecting medical items are somewhat elusive because of the effect of the aforementioned factors on disinfection efficacy. Certain contact times have proved reliable Table 1 , but, in general, longer contact times are more effective than shorter contact times.
Microorganisms may be protected from disinfectants by production of thick masses of cells and extracellular materials, or biofilms Biofilms are microbial communities that are tightly attached to surfaces and cannot be easly removed. Once these masses form, microbes within them can be resistant to disinfectants by multiple mechanisms, including physical characteristics of older biofilms, genotypic variation of the bacteria, microbial production of neutralizing enzymes, and physiologic gradients within the biofilm e.
Bacteria within biofilms are up to 1, times more resistant to antimicrobials than are the same bacteria in suspension Although new decontamination methods are being investigated for removing biofilms, chlorine and monochloramines can effectively inactivate biofilm bacteria Investigators have hypothesized that the glycocalyx-like cellular masses on the interior walls of polyvinyl chloride pipe would protect embedded organisms from some disinfectants and be a reservoir for continuous contamination , , Biofilms have been found in whirlpools , dental unit waterlines , and numerous medical devices e.
Their presence can have serious implications for immunocompromised patients and patients who have indwelling medical devices. Some enzymes , , and detergents can degrade biofilms or reduce numbers of viable bacteria within a biofilm, but no products are EPA-registered or FDA-cleared for this purpose. Skip directly to site content Skip directly to page options Skip directly to A-Z link.
Infection Control. Section Navigation. Facebook Twitter LinkedIn Syndicate. On This Page. Number and Location of Microorganisms. Innate Resistance of Microorganisms. Concentration and Potency of Disinfectants. Physical and Chemical Factors. Organic and Inorganic Matter. Duration of Exposure. The mechanisms involved in biocide resistance to biocides are becoming better understood.
Intrinsic resistance intrinsic insusceptibility is found with bacterial spores, mycobacteria and Gram-negative bacteria. This resistance might, in some instances, be associated with constitutive degradative enzymes but in reality is more closely linked to cellular impermeability. The coats s and, to some extent, the cortex in spores, the arabinogalactan and possibly other components of the mycobacterial cell wall and the outer membrane of Gram-negative bacteria limit the concentration of active biocide that can reach the target site s in these bacterial cells.
A special situation is found with bacteria present in biofilms, which can be considered as being an intrinsic resistance mechanism resulting from physiological phenotypic adaptation of cells. Acquired resistance to biocides may arise by cellular mutation or by the acquisition of genetic elements. They looked at the effect of exposure on the bacteria and found that mutants that make more efflux pumps than normal were produced.
Because the efflux pumps can also rid the cell of some antibiotics, pathogenic bacteria with more pumps are a threat to patients as they could be more resistant to treatment. If bacteria that live in protected environments are exposed to biocides repeatedly, for example during cleaning, they can build up resistance to disinfectants and antibiotics.
Such bacteria have been shown to contribute to hospital-acquired infections. Effective inhibitors would reduce the likelihood of additional resistance mechanisms emerging in bacteria," said Dr Kaatz.
Materials provided by Society for General Microbiology. Note: Content may be edited for style and length. Science News. ScienceDaily, 6 October
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