Water, water everywhere nor any a sterile drop to rinse your endoscope

Evaluation of two detergent-disinfectants and a detergent on a Klebsiella pneumoniae biofilm formed within Tygon tubes

BACKGROUND

Transmission of infections via contaminated endoscopes is a common problem. Manual cleaning, using at least a detergent, is an important step in endoscope processing and should be performed as soon as possible to avoid drying of organic residues that might interfere with high-level disinfection and promote biofilm formation.

AIM

To assess the efficacy of two detergent-disinfectants, enzymatic and non-enzymatic, and of an enzymatic detergent used during the manual cleaning against a Klebsiella pneumoniae biofilm.

METHODS

A 24 h biofilm statically formed in a Tygon tube was exposed to detergent-disinfectants at 20 °C and 35 °C for 10 mn, and to enzymatic detergent at 45 °C for 60 mn. The logarithmic reduction in bacteria in the Tygon tube and the number of bacteria in the product supernatant were calculated.

FINDINGS

Biofilm formation was reproducible between assays. After exposure to detergent-disinfectants, the logarithmic reduction was between 6.32 and 6.71 log10 cfu/cm2 in the Tygon tubes. No bacteria were found in their supernatants. Results in the detergent-disinfectant group were not affected by the exposure temperature or the addition of enzymes. No decrease in the bacterial load was observed in the Tygon tubes after exposure to the enzymatic detergent. Bacteria were found in its supernatant.

CONCLUSION

These results show the importance of the choice of products used during the manual cleaning phase. They also show the potential benefit of combining detergent and disinfectant activity to decrease the bacterial load during the manual cleaning step of endoscope processing.

Aldehyde-resistant mycobacteria bacteria associated with the use of endoscope reprocessing systems

Bacteria can develop resistance to antibiotics, but little is known about their ability to increase resistance to chemical disinfectants. This study randomly sampled 3 automated endoscope reprocessors in the United States using aldehydes for endoscope disinfection. Bacterial contamination was found after disinfection in all automated endoscope reprocessors, and some mycobacteria isolates demonstrated significant resistance to glutaraldehyde and ortho-phthaldehyde disinfectants. Bacteria can survive aldehyde-based disinfection and may pose a cross-contamination risk to patients.

A study of the efficacy of bacterial biofilm cleanout for gastrointestinal endoscopes

AIM: To compare the influence and clearance effect of enzymatic and non-enzymatic detergents against Escherichia coli (E. coli) biofilm on the inner surface of gastroscopes.

METHODS: Teflon tubes were incubated in a mixture of different detergents and E. coli culture (10⁶ CFU/mL) for 72 h at 15°C, and biofilms on the inner surface of the teflon tubes were analyzed by bacterial count and scanning electron microscopy. To evaluate the clearance effect of detergents, after biofilms were formed on the inner surface of Teflon tubes by 72 h lavage with E. coli culture, tubes were lavaged by enzymatic and non-enzymatic detergents at a speed of 250 mL/min, then biofilms on the inner surface were analyzed by bacterial count and scanning electron microscopy.

RESULTS: Non-enzymatic detergent had a better inhibition function on biofilm formation than enzymatic detergent as it reduced bacterial burden by 2.4 log compared with the control samples (P = 0.00). Inhibition function of enzymatic detergent was not significantly different to that of control samples and reduced bacterial burden by 0.2 log on average (P > 0.05). After lavaging at 250 mL/min for 3 min, no living bacteria were left in the tubes. Scanning electron microscopy observation showed biofilms became very loose by the high shear force effect.

CONCLUSION: Non-enzymatic detergent has a better inhibition effect on biofilm formation at room temperature. High speed pre-lavage and detergents are very important in temporal formed biofilm elimination.

Shewanella spp. infection following treatment for upper gastrointestinal bleeding

Shewanella spp. are an uncommon cause of human infection, with exposure to water being the commonest source. We report a patient with a malignancy and upper gastrointestinal bleeding who underwent a gastric lavage followed by an endoscopy as part of her investigations. She subsequently developed Shewanella spp. bacteraemia without any clinical source of infection.

Modeling microbial survival in buildup biofilm for complex medical devices

Background

Flexible endoscopes undergo repeated rounds of patient-use and reprocessing. Some evidence indicates that there is an accumulation or build-up of organic material that occurs over time in endoscope channels. This "buildup biofilm" (BBF) develops as a result of cyclical exposure to wet and dry phases during usage and reprocessing. This study investigated whether the BBF matrix represents a greater challenge to disinfectant efficacy and microbial eradication than traditional biofilm (TBF), which forms when a surface is constantly bathed in fluid.

Methods

Using the MBEC (Minimum Biofilm Eradication Concentration) system, a unique modelling approach was developed to evaluate microbial survival in BBF formed by repetitive cycles of drying, disinfectant exposure and re-exposure to the test organism. This model mimics the cumulative effect of the reprocessing protocol on flexible endoscopes. Glutaraldehyde (GLUT) and accelerated hydrogen peroxide (AHP) were evaluated to assess the killing of microbes in TBF and BBF.

Results

The data showed that the combination of an organic matrix and aldehyde disinfection quickly produced a protective BBF that facilitated high levels of organism survival. In cross-linked BBF formed under high nutrient conditions the maximum colony forming units (CFU) reached ~6 Log₁₀ CFU/peg. However, if an oxidizing agent was used for disinfection and if organic levels were kept low, organism survival did not occur. A key finding was that once established, the microbial load of BBF formed by GLUT exposure had a faster rate of accumulation than in TBF. The rate of biofilm survival post high-level disinfection (HLD) determined by the maximum Log₁₀CFU/initial Log₁₀CFU for E. faecalis and P. aeruginosa in BBF was 10 and 8.6 respectively; significantly different compared to a survival rate in TBF of ~2 for each organism. Data from indirect outgrowth testing demonstrated for the first time that there is organism survival in the matrix. Both TBF and BBF had surviving organisms when GLUT was used. For AHP survival was seen less frequently in BBF than in TBF.

Conclusion

This BBF model demonstrated for the first time that survival of a wide range of microorganisms does occur in BBF, with significantly more rapid outgrowth compared to TBF. This is most pronounced when GLUT is used compared to AHP. The data supports the need for meticulous cleaning of reprocessed endoscopes since the presence of organic material and microorganisms prevents effective disinfection when GLUT and AHP are used. However, cross-linking agents like GLUT are not as effective when there is BBF. The data from the MBEC model of BBF suggest that for flexible endoscopes that are repeatedly used and reprocessed, the assurance of effective high-level disinfection may decrease if BBF develops within the channels.

Bacterial biofilms within the clinical setting: what healthcare professionals should know

Bacterial biofilm formation is the prevailing microbial lifestyle in natural and manmade environments and occurs on all surface types. Biofilm formation develops in several phases and is influenced by various parameters, both environmental and inherent to the attaching cell. Biofilms also serve as protective niches for particular pathogens when outside a host. Although it is accepted that biofilms are ubiquitous in nature, the significance of biofilms in clinical settings, especially with regard to their role in medical-related infections, is often underestimated. It has been found that several aspects of human pathogenesis within a clinical context are directly related to biofilm development. Various types of surfaces in clinical settings are prone to biofilm development and an increased risk of disease may be a direct consequence of their formation. This review describes the process of biofilm formation, highlights the importance of bacterial associations with surfaces in clinical settings and describes various methods for biofilm visualization and control.

Using an efficient biofilm detaching agent: an essential step for the improvement of endoscope reprocessing protocols

Biofilms develop inside endoscope channels even when valid endoscope reprocessing protocols are applied. The use of an efficient biocide is not sufficient if the channels are not cleaned thoroughly prior to disinfection. This study compared new anti-biofilm combinations of detachment promoting agents with a cleaning product in current use. Tests were performed using Teflon tubing and a contamination device that reproduces conditions that are prevalent during endoscopy. Products were subjected to static+brushing or dynamic treatments, and their ability to remove a preformed biofilm was assessed. The residual biofilm after treatment was assessed and compared with untreated controls. The percentage of surface covered by biofilm was measured after staining with crystal violet. Culturable bacteria levels were determined by plating the bacteria scraped from the tubing surface and counting the colony-forming units (CFU). Further tests were performed on actual endoscopes that had been contaminated artificially. Biofilm removal was confirmed by scanning electron microscopy. This study showed that the new anti-biofilm products prevented the build-up of biofilm and removed a mature biofilm (approximately 10(8)CFU/cm(2)), whereas protocols based on detergent-disinfectants containing quaternary ammonium compounds showed low efficacy as these protocols and products fixed the biofilm on the endoscope surfaces. The new procedure and agents represent a new approach to biofilm control that may improve the efficacy of endoscope reprocessing, and reduce the risk of transmitting infections.

Surface decontamination of surgical instruments: an ongoing dilemma

The issues of cross-infection and the survival of variant Creutzfeldt Jakob disease (vCJD) on surgical instruments have highlighted the importance of cleanliness of multiple-use surgical instruments. The aim of this study was to assess the levels of total protein contamination on a wide range of surgical instruments as an indication of the effectiveness of routine cleaning and disinfection in hospitals. Anonymized trays of wrapped and autoclaved instruments were supplied to two laboratories for analysis at the stage where they would normally be returned to operating theatres. Instruments were assessed for residual protein and total organic matter. Laboratory A showed that 17% (35/206) of instruments were above a threshold that equated to 200 microg. The worst examples, a McIvor gag, a Draffin rod (child) and a Yankaur sucker, had 1.028, 1.286 and 2.228 mg of extractable protein, respectively. The median (25th, 75th percentiles) amount of protein from instruments from different hospitals assessed in Laboratory B ranged from 8 (3, 30)mug (Hospital C) to 91 (35, 213) mug (Hospital D) (P=0.044). The residual matter washed from instruments varied from 0.62 (0.32, 0.81) mg (Hospital E) to 3.5 (3.5, 4.0) mg (Hospital A) (P=0.0001). In one case, 45 mg of residual organic matter was washed from an instrument (split stem). In conclusion, this study demonstrated that a proportion of instruments at the point of use show levels of protein that could pose a direct cross-infection risk via prion agents and other organic contamination that may reduce the effectiveness of cleaning/disinfection strategies targeted against either prions or traditional infectious agents.

German guidelines for reprocessing endoscopes and endoscopic accessories: guideline compliance in Frankfurt/Main, Germany

Guidelines for reprocessing flexible endoscopes have been published in many countries. The present survey investigated compliance with German guidelines in all hospitals and private practices in Frankfurt/Main, Germany. In 2003, all endoscopic units in Frankfurt/Main [15 hospitals and 23 private practices (10 large practices performing >1,000 endoscopies/year and 13 small practices performing <1,000 endoscopies/year)] were visited by members of the Public Health Service and assessed using a checklist based on the recommendations of the German guidelines. In 2004, a re-evaluation took place, either by analysing the written reports of the institutions or by visiting them again. Meanwhile, one hospital had closed and three small practices had ceased performing endoscopy, so the re-evaluation encompassed 14 hospitals and 20 private practices. In 2003, hospital compliance with the guidelines was satisfactory but many problems were identified in private practices. Between 2003 and 2004, great improvements were made. By the end of 2004, 90% of private practices had adequate storage facilities for reprocessed endoscopes, and were performing reprocessing of bottles and tubes for air-/water-channel flushing correctly (2003: adequate storage 52%; correct reprocessing 74%). Sterilization of endoscopic accessories was satisfactory, and routine testing of endoscopes after reprocessing was performed in all private practices at the end of 2004 (2003: sterilization of accessories 57%; microbiological control tests 56%). In 2003, although hospital compliance with the guidelines was satisfactory, mandatory improvements were required in private practices, notably in smaller units. Infection control advice and the control of public health regulations resulted in the correction of most processing faults between 2003 and 2004.

Mycobacteria in drinking water distribution systems: ecology and significance for human health

In contrast to the notorious pathogens Mycobacterium tuberculosis and M. leprae, the majority of the mycobacterial species described to date are generally not considered as obligate human pathogens. The natural reservoirs of these non-primary pathogenic mycobacteria include aquatic and terrestrial environments. Under certain circumstances, e.g., skin lesions, pulmonary or immune dysfunctions and chronic diseases, these environmental mycobacteria (EM) may cause disease. EM such as M. avium, M. kansasii, and M. xenopi have frequently been isolated from drinking water and hospital water distribution systems. Biofilm formation, amoeba-associated lifestyle, and resistance to chlorine have been recognized as important factors that contribute to the survival, colonization and persistence of EM in water distribution systems. Although the presence of EM in tap water has been linked to nosocomial infections and pseudo-infections, it remains unclear if these EM provide a health risk for immunocompromised people, in particular AIDS patients. In this regard, control strategies based on maintenance of an effective disinfectant residual and low concentration of nutrients have been proposed to keep EM numbers to a minimum in water distribution systems.

The genetics of nontuberculous mycobacterial infection

The molecular aetiology of familial susceptibility to disseminated mycobacterial disease, usually involving weakly pathogenic strains of mycobacteria, has now been elucidated in more than 30 families. Mutations have been identified in five genes in the interleukin-12-dependent interferon-gamma pathway, highlighting the importance of this pathway in human mycobacterial immunity. Knowledge derived from the study of these rare patients contributes to our understanding of the immune response to common mycobacterial pathogens such as Mycobacterium tuberculosis and Mycobacterium leprae, which remain major public health problems globally. This knowledge can be applied to the rational development of novel therapies and vaccines for these important mycobacterial diseases.