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Biomedical subjects

Chris H Miller

Publications and source records attributed to Chris H Miller.

7 recordsLinked to original sources
PubMed2005

Effects of delayed microbial analysis of dental unit water line specimens.

PURPOSE: Monitoring microbial concentrations in water emitted from dental unit water lines (DUWL) is an important safety procedure. Improper handling of test water specimens could give incorrect results. Thus, the objective of this study was to measure the effects delayed culturing might have on DUWL specimens. METHODS: First, 100 mL water specimens were obtained from 10 different handpiece service lines within the School. All units had independent water systems, used DI (deionized water) water and were routinely cleaned using an alkaline peroxide based product. Two specimens of 10 mL were removed from the bottles and placed into individual sterile conical tubes. One set of tubes was processed immediately. 0.05 mL of sterile 1.0% (w/v) sodium thiosulfate solution was added to undiluted and diluted (1:10 and 1:100 with sterile DI water) specimens. After mixing, specimens were spiral plated onto duplicate R2A plates and incubated at 21degrees C for 7 days. Colonies were then counted and the cfu/mL of each original specimen determined. Another set of tubes was placed into a shipping envelope and mailed out to the School. Upon receipt, the tubes were processed as described above. The remaining 80 mL of water in the collection bottles were divided equally into new sterile tubes. One tube was left at 21 degrees C, while the other was placed into a 37 degrees C incubator. Aliquots were processed immediately and then after 1, 3 and 7 days. Next, 30 mL water specimens were obtained from 15 handpiece service lines in three outside clinics. All units had independent water systems, used DI water and were routinely cleaned with an alkaline peroxide-based product. Specimens were then divided equally into three sterile conical tubes. One of the tubes was transported (at 4 degrees C) to the laboratory and immediately processed as described. At the collection site, the second tube was placed into a padded envelope and mailed back to the School. The third tube was returned by overnight delivery using a Cool Pack type container. Upon receipt, all the tubes were processed as described previously. RESULTS: The 10 handpiece waterline specimens processed immediately ranged from 0 to 1000 cfu/mL. Holding specimens at 21 degrees C produced radically higher bacterial counts (1540-866,000 cfu/mL) in water from 90% of the handpieces. Holding at 37 degrees C produced unacceptably high bacterial counts in only 50% of the handpiece specimens. Mailed specimens were cultured 5 days after collection and water of unacceptable quality water was noted in 70% of the specimens. In another experimental set, mailed specimens arrived after 72 hours and were an average of 20 degrees C. Express sent specimens came the next morning at an average temperature of 4.5 degrees C. Only one waterline specimen processed immediately contained more than 500 cfu/mL. In contrast, 80% of specimens returned by post at ambient temperature had unacceptably high bacterial counts (780-376,000 cfu/mL). Express sent specimens produced the same results as those processed immediately.

Bacteria, Aerobic↗
PubMed2004

An investigation of the microbial contamination of dental unit air and water lines.

AIM: The objective of this study was to measure the microbial contamination released from dental unit air lines (DUAL) and dental unit water lines (DUWL). MATERIALS AND METHODS: Emissions from DUAL and DUWL from five dental units supplied by a central water source (tap) and a centralised air supply were sampled three times over a five- week period. Air was forced through sterile water and then plated onto selective agar using apparatus designed to spread the sample solution evenly, and then incubated at room temperature for seven days. Colonies were then counted and the concentration of bacteria present was determined and expressed as colony forming units per millilitre (cfu/ml) per minute. The same procedure was used to evaluate five other dental units, which had attached independent water reservoir (bottle) systems (IWR). Only deionised water was added to the bottles and unit waterlines were cleaned weekly with alkaline peroxide based solution. Values were expressed as cfu/ml. RESULTS: Air and water specimens obtained from dental units supplied with tap water had microbial counts significantly (t-test, p < 0.05) greater than IWR dental units. CONCLUSIONS: Results indicate that IWR can reduce the numbers of micro-organisms released from DUWL. However, the effectiveness of such systems should be routinely monitored. Emissions from DUAL seems to reflect the levels of microbial contamination present in DUWL.

Air Microbiology↗
PubMed2004

Sterilization update 2003.

Instrument processing is a key part of the office infection control program. Each step in the process must be performed correctly to help ensure patient safety. The instrument processing area must be organized so that contaminated items are not confused with sterilized items, and so that sterilized items do not accidentally become recontaminated. Instruments need to be cleaned completely of visible debris using an ultrasonic cleaner or instrument washer. The cleaned instruments are packaged before sterilization to protect them from recontamination until they are opened for use for the next patient. Processing the packaged instruments through a heat sterilizer (steam, dry heat, or unsaturated chemical vapor) kills any microbes that remain on the instruments. The sterile packages are handled and stored in a manner that preserves the integrity of the packaging material. The use and functioning of the sterilizer is monitored by mechanical, chemical, and biological means, and records are kept to document these evaluations. Sterilization failures are addressed carefully so that patient safety can be maintained.

Dental Instruments↗
PubMed2003

The effect of distillation and line cleaning on the quality of water emitted from dental units.

PURPOSE: To monitor water emitted from dental units connected to centralized water distillation units fitted with reservoirs for dispensing chemicals designed to control biofilms. METHODS: Three private practice dental offices participated in the study. None of the office operatories had independent water reservoir (bottle) systems or any other type of water treatment equipment. Initially, 5.0 mL water specimens were obtained from the handpiece and three-way syringe service lines as well as from the sink faucets in three operatories in each office. Specimens were collected at the end of the workweek. Specimens were neutralized for residual chlorine, diluted and spiral plated onto R2A agar. Aerobic incubation was allowed for 7 days at 21 degrees C. Numbers of colonies were then determined and expressed as CFU/mL. If water specimens containing more than 200 CFU/mL were detected, the offices were equipped with water distillers with attached cleaning solution dispensers. The units allowed distilled water to move under normal pressure to all connected dental units. When cleaning, the distillers were inactivated, which allowed cleaning fluid to move under pressure from the dispensers through all unit waterlines. The waterline-cleaning scheme followed the manufacturer recommendations. The presence of no more than 200 CFU/mL in emitted water was then established and a regimen of weekly cleanings applied for 3 weeks. Water specimens were always collected on the last workday of the week. Then, cleaning was suspended and weekly monitoring performed. Cleaning was restored immediately after detection of more than 200 CFU/mL. RESULTS: Levels of microbial contamination prior to the initiation of cleaning indicated marked variability (720-332,000 CFU/mL) and that water containing less than 200 CFU/mL was not being emitted from any operatory water source. However, sought-after water was consistently obtained over a period of 3 weeks from all unit sources after line-cleaning processes were completed. Water containing less than 200 CFU/mL was obtained from all unit sources in the three offices after skipping of one weekly cleaning. In one office, cleaning was suspended for 3 weeks without affecting water quality. Resumption of weekly cleanings produced desirable water from all sources in the three offices within 2 weeks. Results indicate that dental units attached to centralized combined water distillation-cleaning solution distribution systems can produce water with less than 200 CFU/mL and that the missing of one weekly cleaning did not negatively affect water quality.

Biofilms↗