Glutaraldehyde‐resistant Mycobacterium chelonae from endoscope washer disinfectors

Abstract

Glutaraldehyde is used to disinfect flexible and other heat‐sensitive endoscopes often with the aid of automated systems. Mycobacterium chelonae is being isolated with increasing frequency from these washer disinfectors and processed endoscopes. This has, on occasions, led to misdiagnosis and iatrogenic infections. Recent reports suggest that disinfecting machines, on a sessional or regular basis, with 2% glutaraldehyde may have selected and therefore encouraged the growth of strains of Myco. chelonae, possibly in biofilm, with decreasing susceptibility to glutaraldehyde. In view of this, the resistance of three strains of Myco. chelonae var. chelonae (the type strain NCTC 946 and two machine isolates) was tested against 2% glutaraldehyde and a wide range of alternative disinfectants. Disinfectants tested were a chlorine releasing agent, sodium dichloroisocyanurate at 1000 ppm and 10 000 ppm av Cl, 0·35% peracetic acid (NuCidex, Johnson & Johnson), 70% industrial methylated spirit (IMS), 1% peroxygen compound (‘Virkon’, Antec International) and 10% succine dialdehyde (‘Gigasept’, Sanofi Winthrop). Suspension and carrier tests were carried out in the presence and absence of an organic load. Results showed the type strain, which had not been exposed to the selective pressure of disinfectant usage, to be very sensitive to most disinfectants with the exception of 1% Virkon. The washer disinfector isolates, on the other hand, were extremely resistant to 2% glutaraldehyde and showed greater resistance to 1% Virkon and 1000 ppm NaDCC. Purchasing machines in which the entire fluid pathways, including those for delivering rinse water, are disinfected with an appropriate agent during each cycle are preferred. If this is not possible then sessional cleaning and disinfection at the start of each day and regular maintenance should prevent biofilm formation and contamination with disinfectant‐resistant strains of mycobacteria. In addition to machine disinfection, the use of sterile or bacteria‐free (filtered <0·45μm) water is essential for bronchoscopes and all invasive endoscopes. If there is doubt over the effectiveness of the machine disinfection procedure or water quality, the channels and surfaces of endoscopes may be rinsed with 70% IMS after automated processing.

Resistance of Acanthamoeba Cysts to Disinfection Treatments Used in Health Care Settings

“…Viability staining of cysts treated with glutaraldehyde might be useful to understand these effects. Resistance of Acanthamoeba trophozoites to glutaraldehyde raises important questions about the potential association of glutaraldehyde-resistant Acanthamoeba with nontuberculous mycobacteria (NTM) that can also resist glutaraldehyde and grow within amoebae (18,23,58). It has been demonstrated that the resistance of NTM to glutaraldehyde is at least partially due to mutations in cell wall porins and that these mutations also increase the resistance of NTM to antibiotics commonly used to treat these infections (53).…”

Disinfectant-resistant bacteria in Buenos Aires city hospital wastewater

“…Increasing attention has been directed recently to the responses of bacteria to biocides. Griffiths et al (5) have observed that Micobacterium chelonae isolated from endoscope washer disinfector may be significantly less sensitive to glutaraldehyde in comparison with the type strain. Studies with glutaraldehyde-resistant M. chelonae strains suggest that the arabinogalactan/arabinomannan component of the cell wall is associated with resistance (13).…”

Role of Porins in the Susceptibility of Mycobacterium smegmatis and Mycobacterium chelonae to Aldehyde-Based Disinfectants and Drugs

“…1). Recent reports suggest, however, that RGM are being isolated with increasing frequency from washer disinfectors and GTA-processed endoscopes, with recent Mycobacterium chelonae and Mycobacterium massiliense outbreaks being associated with the development of resistance to GTA (4,8,10,17,30).…”

“…1). Recent reports suggest, however, that RGM are being isolated with increasing frequency from washer disinfectors and GTA-processed endoscopes, with recent Mycobacterium chelonae and Mycobacterium massiliense outbreaks being associated with the development of resistance to GTA (4,8,10,17,30).GTA is thought to be predominantly a surface-reactive biocide which forms bridges or cross-links with amino groups of proteins exposed at the surface of bacterial cells (17). Although the mechanisms of resistance of mycobacteria to the disinfectant are not known, it is thus reasonable to assume that changes in the cell surface resulting in decreased binding and/or penetration of GTA may be mechanisms through which RGM develop resistance.…”