Five-year trends in bacterial contamination of dialysis equipment

Bedside dialysis monitoring equipment for hemodialysis are located in the bioburden section upstream of the endotoxin-retentive filter for dialysis fluid sterilization. We observed 26 equipment at our institution for bacterial contamination at least once every 4 weeks for 5 years with another ultrafiltration membrane upstream to prevent bacterial contamination. Bacterial contamination levels were highest and most diverse at the time of the first flush. During subsequent initial cleanng, the contamination level decreased, and bacterial species converged almost exclusively to one genus, namely Methylobacterium spp. During clinical use, the equipment were cleaned and disinfected daily after dialysis, and daily operations and maintenance were performed using aseptic techniques. Although the frequency of bacterial detection decreased annually, the same bacterial genotypes observed at the first flush were isolated even after long time periods and were thought to persist in the equipment possibly by forming biofilm. Pseudomonas aeruginosa was newly detected after the replacement of parts during breakdown maintenance, indicating the need to sterilize replacement parts. Thus, the bioburden should be assessed regularly as part of the management of in-house-produced dialysis fluid.

Sodium Hypochlorite is Effective against Biofilms in Dialysis Equipment

To test the efficacy of chemical disinfectants against bacterial biofilms in hemodialysis equipment, a Center for Disease Control and Prevention (CDC)-Biofilm Reactor was used to create biofilms. Methylobacterium radiotolerance was isolated from the hemodialysis fluid and used as the test organism. We examined the efficacy of sodium hypochlorite (NaOCl) in elimination of planktonic cells compared to that in the case of biofilms. Planktonic bacteria were completely eliminated at 50 parts per million (ppm) of NaOCl, which is the lowest concentration for clinical use. The viable cell count in the biofilm reached its minimum value around a logarithmic reduction value (LRV) of 6, when the concentration was raised to 1000 ppm and the reaction time was extended by 1 hour or more. Furthermore, at 200 ppm, the LRV was elevated depending on the time. And the LRV while maintaining static conditions for 6 hours at 200 ppm was similar to that of short time at 1000 ppm. These results suggest that NaOCl has sufficient bactericidal activity even for biofilms at a practical concentration and reaction time, and that the CDC-Biofilm Reactor is an effective tool for finding useful disinfection conditions.

Accurate MRSA identification through dual-functional aptamer and CRISPR-Cas12a assisted rolling circle amplification

Infectious diseases have become one of the most threatening global challenge with high morbidity and mortality, bringing great difficulties to clinical diagnosis and treatment. New strategy for high-specific and sensitive bacteria detection are urgently needed in facing the crisis of worldwide antibiotic resistance. Herein, a novel method through the integration of dual aptamer technology and CRISPR-Cas12a assisted rolling circle amplification (RCA) was present to obtain both accurate identification and high-sensitive detection of Methicillin-Resistant Staphylococcus Aureus (MRSA). The specificity inherited from the dual functionalized aptamers initiated bioconjugation to specifically recognize the protein targets on the surface of bacteria. Besides the target activity, the functionalized aptamer could also convert the protein recognition to nucleic acids signals. Through the integration of attached RCA and CRISPR-Cas12a assisted trans-cleavage, dual amplification of the nucleic acid signal was obtained. Based on this, we have extended the application of CRISPR-Cas12a from the nucleic acid detection to bacteria detection. As a result, the proposed method was demonstrated to be with significantly improved sensitivity towards MRSA detection. We believe that the novel integrated strategy would diversify the existing pool of bacterial detection and inspire the development of promising drug candidates in the future.