Comparison of two endoscope channel cleaning approaches to remove cyclic build-up biofilm.

INTRODUCTION: Biofilm contributes significantly to bacterial persistence in endoscope channels. Enhanced cleaning methods capable of removing biofilm from all endoscope channels are required to decrease infection risk to patients. This head-to-head study compared cyclic build-up biofilm removal of an automated endoscope channel cleaner (AECC) with standard manual cleaning according to instructions for use (IFU) in polytetrafluorethylene channels. METHODS: Cyclic build-up biofilm was grown in 1.4-mm (representing air/water and auxiliary channels) and 3.7-mm (representing suction/ biopsy channels) inner diameter polytetrafluorethylene channels. All channels were tested for residual total organic carbon, protein, and viable bacteria. Internationally recognized ISO 15883-5:2021 alert levels were used as cleaning benchmarks for protein (3 µg/cm2) and total organic carbon (6 µg/cm2). RESULTS: The automated cleaner significantly outperformed manual cleaning for all markers assessed (protein, total organic carbon, viable bacteria) in 1.4-mm and 3.7-mm channels representing air/water/auxiliary and suction/biopsy channels, respectively. Manual cleaning failed to remove biofilm from the air/water and auxiliary channels. According to the IFU, these channels are not brushed, suggesting a potential root cause for a portion of the numerous endoscopy-associated infections reported in the literature. CONCLUSION: AECC shows potential to deliver enhanced cleaning over current practice to all endoscope channels and may thereby address infection risk.

Endoscope sampling and culturing methods.

BACKGROUND: Contamination rates reported in the literature for patient-ready flexible endoscopes vary from 0.4% to 49%. Unfortunately, the comparison and interpretation of these results is almost impossible since several factors including sampling and culturing methods, target levels for contamination, or definition of indicator micro-organisms vary widely from one study to the other. AIM: To compare the efficacy of six duodenoscope sampling and culturing methods by means of extraction efficacy comparison, while at the same time identifying key parameters that provide optimal microbial recovery. METHODS: The duodenoscope sample extraction efficacy of each method was assessed using the repetitive recovery method described in ISO 11737-1: 2018. FINDINGS: Mean overall bioburden extraction efficacy varied from 1% for the Australian method to 39% for the French one. The lowest endoscope sample extraction efficacy was associated with the absence of any neutralizer, friction, or tensioactive agent, and when only a small portion of the sampling solution collected was inoculated on to culture media. The efficacy of the sampling and culturing methods also varied according to the nature of micro-organisms present in the endoscope, and the time between sampling and culturing. CONCLUSION: This study supports the need for a harmonized and standardized sampling and culturing method for flexible endoscopes.

Physical and composition characteristics of clinical secretions compared with test soils used for validation of flexible endoscope cleaning.

AIM: To determine which simulated-use test soils met the worst-case organic levels and viscosity of clinical secretions, and had the best adhesive characteristics. METHODS: Levels of protein, carbohydrate and haemoglobin, and vibrational viscosity of clinical endoscope secretions were compared with test soils including ATS, ATS2015, Edinburgh, Edinburgh-M (modified), Miles, 10% serum and coagulated whole blood. ASTM D3359 was used for adhesion testing. Cleaning of a single-channel flexible intubation endoscope was tested after simulated use. RESULTS: The worst-case levels of protein, carbohydrate and haemoglobin, and viscosity of clinical material were 219,828µg/mL, 9296µg/mL, 9562µg/mL and 6cP, respectively. Whole blood, ATS2015 and Edinburgh-M were pipettable with viscosities of 3.4cP, 9.0cP and 11.9cP, respectively. ATS2015 and Edinburgh-M best matched the worst-case clinical parameters, but ATS had the best adhesion with 7% removal (36.7% for Edinburgh-M). Edinburgh-M and ATS2015 showed similar soiling and removal characteristics from the surface and lumen of a flexible intubation endoscope. CONCLUSIONS: Of the test soils evaluated, ATS2015 and Edinburgh-M were found to be good choices for the simulated use of endoscopes, as their composition and viscosity most closely matched worst-case clinical material.

Adenosine tri-phosphate (ATP)-based cleaning monitoring in health care: how rapidly does environmental ATP deteriorate?

BACKGROUND: Ensuring cleaning compliance of housekeeping staff is critical to ensure adequate application of surface disinfectants. Adenosine triphosphate (ATP) testing has been recommended as a way to monitor cleaning compliance; however, little is known about the stability of ATP on environmental surfaces. AIM: To assess the stability of ATP from various sources to determine if it is stable for sufficient time to be an effective means of assessing environmental cleaning and disinfection in health care. METHODS: Purified ATP, ATP derived from ATS-T (blood-based test soil) and ATP derived from 10(7) colony-forming units/site of micro-organisms (Pseudomonas aeruginosa, Enterococcus faecalis, Candida albicans) were evaluated in liquid suspension and dried on to surfaces to assess stability over 29 days. Cleaners and disinfectants were sprayed on to surface-dried material with no wiping to determine their effect on microbial viability and ATP stability. FINDINGS: Surface-dried P. aeruginosa, E. faecalis and C. albicans retained 65-96% of their original ATP level on Day 29, despite reduced or no viability. Surface-dried ATS-T had 100% and 3% of its original ATP on Days 4 and 29, respectively. Deterioration of the ATP signal was most pronounced for suspensions. Purified ATP was stable over 29 days in suspension or dried on to a surface. CONCLUSIONS: ATP residuals from organic material and micro-organisms (dead or alive) are stable when dried on to surfaces. In the absence of cleaning and disinfection, the relative light unit signal will not deteriorate rapidly, making ATP a good marker to monitor cleaning.

Fertilizer and sanitary quality of digestate biofertilizer from the co-digestion of food waste and human excreta.

This research was aimed at assessing the fertilizer quality and public health implications of using digestate biofertilizer from the anaerobic digestion of food wastes and human excreta. Twelve (12) kg of food wastes and 3kg of human excreta were mixed with water in a 1:1 w/v to make 30-l slurry that was fed into the anaerobic digester to ferment for 60days at mesophilic temperature (22-31°C). Though BOD, COD, organic carbon and ash content in the feedstock were reduced after anaerobic digestion by 50.0%, 10.6%, 74.3% and 1.5% respectively, nitrogen, pH and total solids however increased by 12.1%, 42.5% and 12.4% respectively. The C/N ratios of the feedstock and compost are 135:1 and 15.8:1. The residual total coliforms of 2.10×10(8)CFU/100ml in the digestate was above tolerable limits for direct application on farmlands. Microbial analysis of the digestate biofertilizer revealed the presence of Pseudomonas, Klebsiella, Clostridium, Bacillus, Bacteroides, Penicillum, Salmollena, and Aspergillus. Klebsiella, Bacillus, Pseudomonas, Penicillum and Aspergillus can boost the efficiency of the biofertilizer through nitrogen fixation and nutrient solubility in soils but Klebsiella again and Salmollena are potential health risks to end users. Further treatment of the digestate for more efficient destruction of pathogens is advised.

Intermediate-level disinfection with accelerated hydrogen peroxide prevents accumulation of bacteria in Versajet™ tubing during repeated daily debridement using simulated-use testing with an inoculated pork hock.

OBJECTIVE: This study assesses the feasibility of using the Versajet™ system (VJS) on an inoculated pork hock (PH) skin surface sequentially for 8 days with daily cleaning and intermediate-level disinfection (ILD). METHODS: Daily, PHs were inoculated with bacteria suspended in artificial test soil (ATS). An ILD protocol with accelerated hydrogen peroxide (AHP, OxivirTB(®)) was employed to clean and disinfect the VJS between debridements. RESULTS: PH skin contains 6.1-6.8×10(6)cfu/cm(2) bacteria. Bacterial counts in the handpiece and discharge hoses immediately after debridement of the PHs, and before cleaning, increased throughout the study period (5.19-6.43log10cfu/mL). Cleaning with the ILD protocol was reduced bacterial counts on the VJS by 6-log. Protein, a surrogate marker of organic contamination, was also reduced post-cleaning and ILD. Compared to a maximum post-debridement level of protein (57.9 µg/mL) obtained before ILD, VJS protein levels dropped to 9.8 (handpiece) and 13.8 µg/mL (discharge hose). CONCLUSIONS: Disinfection of the handpiece and discharge hose after debridement with AHP resulted in a 6-log reduction in bacterial count and 4.2 fold reduction in protein. An ILD protocol with an AHP may be a feasible method for serial skin surface debridements with the VJS for up to eight days.

Continuing performance feedback and use of the ultraviolet visible marker to assess cleaning compliance in the healthcare environment.

BACKGROUND: Environmental surfaces have long been suspected to be a reservoir that could contribute to the presence of micro-organisms in healthcare facilities. The objective of this study was to evaluate the effect of providing weekly feedback to the housekeeping staff in improving and sustaining cleaning compliance when using ultraviolet visible marker (UVM) as an audit tool. METHODS: The housekeeping staff selected 90% as the cleaning compliance target. The UVM was applied to the toilet seat, sink, soap dispenser and door knob surfaces within the patient's washrooms on consecutive weekdays. The study included three arms: staff in arm 1 received cleaning compliance feedback throughout the 24-week study period, arm 2 and arm 3 staff received feedback for weeks 13-24 and weeks 1-12, respectively. Feedback was also provided to housekeeping staff by posting graphs on the wards and in the housekeeping office. FINDINGS: A pre-study audit showed 66.9%, 66.5% and 66.4% cleaning compliance for arms 1, 2 and 3 respectively. While receiving weekly feedback, all three arms demonstrated significantly improved cleaning compliance (86.7%, 80.4% and 73.7% for arms 1, 2 and 3, respectively). The use of casual staff may have contributed to difficulty in achieving better cleaning compliance as arms 1, 2 and 3 had 16.1%, 26% and 40.3% of shifts filled by casual staff, respectively. CONCLUSIONS: The use of UVM as an audit tool combined with weekly feedback of results to housekeeping staff resulted in significant, sustained improvement in the overall level of cleaning compliance of housekeeping staff.

Evaluation of an algorithmic approach in comparison with the Illumigene assay for laboratory diagnosis of Clostridium difficile infection.

The following three diagnostic algorithms were evaluated in comparison with the Illumigene assay as a stand-alone test for Clostridium difficile detection: glutamate dehydrogenase antigen screen (GDH) followed by toxin A/B antigen testing (Tox A/B) with the cell cytotoxicity assay for discordant specimens (algorithm 1), GDH followed by the Illumigene (algorithm 2), and GDH followed by Tox A/B with the Illumigene for discordant specimens (algorithm 3). A total of 428 stool specimens submitted to three clinical microbiology laboratories in Manitoba, Canada, for C. difficile detection between June 2011 and April 2012 were included in the study. The prevalence of C. difficile in the stool specimens was 14.7% (63/428) based on toxigenic culture (microbiologic reference standard). The sensitivity and specificity of the Illumigene for C. difficile detection were 73.0% and 99.7%, respectively. The corresponding sensitivities and specificities were 65.1% and 100.0% for algorithm 1, 68.3% and 100.0% for algorithm 2, and 69.8% and 100.0% for algorithm 3. Using algorithm 1, a cell cytotoxicity assay was required for toxin detection in 37% of positive tests, prolonging turnaround time. However, the predictive value of a positive test based on a clinical reference standard (all tests positive or cytotoxigenic culture positive and clinical disease on chart review) was slightly higher with algorithm 1 than with the Illumigene assay as a stand-alone test or as part of an algorithm (algorithms 2 and 3). Based on a reduction in turnaround time, simplicity, and acceptable sensitivity and specificity, we recommend algorithm 2 (screening with the GDH antigen test and confirmatory testing with the Illumigene).

Re-evaluation of rejection criteria for endotracheal tube (ETT) specimens from adult patients.

The purpose of this study was to determine optimal criteria for microbiology laboratory screening of endotracheal tube (ETT) specimens submitted for bacterial culture from adult patients. ETT specimens from adult patients that were received by two microbiology laboratories were prospectively evaluated and subdivided into one of three study arms with the following criteria: <10 squamous epithelial cells (SECs) per low-power field with bacteria seen on Gram staining (arm 1), >10 SECs per low-power field with bacteria seen on Gram staining (arm 2) and <10 SECs per low-power field with no bacteria seen on Gram staining (arm 3). A fourth study arm (>10 SECs per low-power field with no bacteria seen on Gram staining) was planned but this arm was terminated due to the paucity of specimens meeting these criteria. Isolate evaluation was performed using standard microbiology protocols. A limited chart review was undertaken at one of the institutions, only reviewing patients from which a potential pathogen was recovered on culture. In total, 141 ETT specimens were evaluated. A potential respiratory pathogen was recovered from 54, 37 and 10 % of specimens in study arms 1, 2, and 3, respectively (P<0.0001, comparing between arm 1 and arm 3). For the 23 patients included in the chart review from whom a potential pathogen was recovered on culture, respiratory infection was considered to be present in 50 % (6/12) of patients in arm 1, 66.6 % (6/9) of patients in arm 2 and 100 % (2/2) of patients in arm 3. Therapy was rarely altered based on culture results. In this study, the ETT specimens submitted for bacterial culture were of limited benefit to clinicians. The data presented here support the use of an absence of bacteria on Gram staining as a rejection criterion for ETT specimens. The criterion of >10 SECs per low-power field should be further evaluated in a prospective study of patients with an unequivocal clinical diagnosis of pneumonia.

Change in antimicrobial susceptibility of Escherichia coli urinary tract isolates at a single institution over a period of 10 years.

Urinary tract infections are common. Few published studies have demonstrated the change in Escherichia coli urinary isolate antimicrobial susceptibility over time within a given area and (or) population. The purpose of this study was to evaluate the change in susceptibility of E. coli clinical isolates obtained from urine specimens at a single institution over a period of 10 years. The microbiology laboratory information system at St. Boniface Hospital (Winnipeg, Manitoba, Canada) was searched retrospectively from 1 January 2000 to 31 December 2009, for all E. coli isolates from either a midstream or catheter urine source that had susceptibility testing performed. Only one isolate per patient was included during the entire study period. Antimicrobial susceptibility testing was carried out with either a Microscan instrument (pre-April 2004) or a Vitek instrument (May 2004 onwards). In total, 7353 E. coli urinary isolates were included for evaluation. Ciprofloxacin susceptibility declined significantly, from 99% in 2000 to 85% in 2009 (p < 0.0001). A small but statistically significant decline in susceptibility was also observed for ampicillin, cefazolin, trimethoprim-sulfamethoxazole, gentamicin, and nitrofurantoin. These data suggest that certain antimicrobials recommended for the treatment of urinary tract infections (ciprofloxacin, trimethoprim-sulfamethoxazole) may no longer be optimal.

Cleaning efficacy of medical device washers in North American healthcare facilities.

The objective of this study was to determine the worst case levels of organic soil on surgical instruments and whether the commercially available TOSI((R)) provided a clinically relevant organic challenge to an instrument washer. Our data showed that protein and haemoglobin levels (374 and 111microg/cm(2), respectively) from the instruments evaluated correlated with those on a TOSI that had a visual score of 2-3 (267 and 60microg/cm(2), respectively). However, the regular TOSI (without the plastic cover) and the TOSI Lum-Chek do not present difficult cleaning challenges; therefore, a visual TOSI score of 1-5 after processing in an automated washer represents a serious cleaning problem. Our results showed that surgical instruments may have high post-cleaning levels of carbohydrate (up to 352microg/cm(2)) and endotoxin (up to 25 373EU/cm(2)), suggesting unrecognised issues with the quality of water used for the final rinse. The average carbohydrate and endotoxin levels post procedure and before cleaning were 138.9microg/cm(2) and 18.14EU/cm(2), respectively. The average protein and haemoglobin levels both showed >99% reduction in levels post cleaning. Our data support the need to monitor the water quality used in instrument washers. In addition, there is an urgent need for establishment of standardised criteria for rapid cleaning indicators for instrument washers to ensure that they provide a clinically relevant method for monitoring washers used in healthcare facilities.

Healthcare-associated infections: think globally, act locally.

Healthcare-associated infections (HAIs) have been a hot topic for several decades. An understanding of HAIs should be based on an understanding of the organisms that cause infection and determine prevention. Although some improvements in control in hospitals have been recorded, the community setting is now implicated, and the role of microbiology in diagnosis, detection of carriers and strain typing of organisms is evident. As healthcare systems vary widely, prevention strategies must be designed accordingly. Hand hygiene, however, remains applicable in all settings, and the WHO is strongly promoting alcohol-based hand rubs to interrupt transmission. Some countries are only beginning to develop standards, whereas compliance is obligatory in others. Economics and cost factors are common to all countries, and litigation is increasingly a factor in some.

Survival of enveloped and non-enveloped viruses on surfaces compared with other micro-organisms and impact of suboptimal disinfectant exposure.

Survival of enveloped and non-enveloped viruses was compared with that of bacteria, yeasts and mycobacteria when dried on the surface of polyvinyl chloride test carriers in the presence or absence of an organic matrix. The efficacy of glutaraldehyde and accelerated hydrogen peroxide (AHP) disinfectants was evaluated. Reovirus, a non-enveloped virus, persisted and had a RF of 2 after 30 days whereas Enterococcus faecalis had an RF of 4 over the same time period. The other test organisms (Sindbis virus, Pseudomonas aeruginosa, Mycobacterium chelonae and Candida albicans) had variable survivals but none survived as long as 30 days. Both glutaraldehyde and AHP were effective at manufactures' recommended dilutions for high-level disinfection. However, only 7% AHP eliminated a glutaraldehyde-resistant strain of M. chelonae. Breakthrough survival was detected at 0.1% glutaraldehyde and 0.05% AHP for all organisms tested. Our data emphasise the need for effective cleaning and disinfection in nosocomial settings to prevent pathogen transmission.

Manual methods are suboptimal compared with automated methods for cleaning of single-use biopsy forceps.

OBJECTIVE: Most reusable biopsy forceps and all of the currently available single-use biopsy forceps do not have a port that allows fluid flow down the inner tubular shaft of the device. Reusable biopsy forceps are widely used and reprocessed in healthcare facilities, and single-use biopsy forceps are reprocessed either in-house (eg, in Canada and Japan) or by third-party reprocessors (eg, in the United States). The objective of this study was to determine the cleaning efficacy of automated narrow-lumen sonic irrigation cleaning, sonication-only cleaning, and manual cleaning for biopsy forceps. DESIGN: A simulated-use study was performed by inoculating the inner channel of single-use biopsy forceps with artificial test soil containing both Enterococcus faecalis and Geobacillus stearothermophilus at concentrations of 10(6) colony-forming units per milliliter. The cleaning methods evaluated were manual cleaning, sonication-only cleaning, and "retroflush" cleaning by an automated narrow-lumen irrigator. Bioburden and organic soil reduction after washing was evaluated. Forceps used in biopsies of patients were also tested to determine the worst-case soiling levels. RESULTS: Only retroflush irrigation cleaning could effectively remove material from within the shaft portion of the biopsy forceps: it achieved an average reduction of more than 95% in levels of protein, hemoglobin, carbohydrate, and endotoxin. However, even this method of cleaning was not totally effective, as only a 2 log10 reduction in bioburden could be achieved, and there were low residual levels of hemoglobin and carbohydrate. CONCLUSION: The data from this evaluation indicate that manual and sonication-only cleaning methods for biopsy forceps were totally ineffective in removing material from within the biopsy forceps. Even the use of retroflush cleaning was not totally effective. These findings suggest that in-hospital reprocessing of biopsy forceps with currently available equipment and cleaning methods is suboptimal.

Manual versus automated methods for cleaning reusable accessory devices used for minimally invasive surgical procedures.

We undertook a simulated-use study using quantitative methods to evaluate the cleaning efficacy of ported and non-ported accessory devices used in minimally invasive surgery. We chose laparoscopic scissors and forceps to represent worst-case devices which were inoculated with artificial test soil containing 10(6) cfu/mL Enterococcus faecalis and Geobacillus stearothermophilus and allowed to dry for 1 h. Cleaning was performed manually, as well as by the automated SI-Auto Narrow lumen cleaner. Manual cleaning left two- to 50-fold more soil residuals (protein, haemoglobin and carbohydrate) inside the lumen of non-ported versus ported laparoscopic accessory devices. The SI-Auto Narrow lumen cleaner was more efficient than manual cleaning and achieved >99% reduction in soil parameters in both non-ported (using retro-flushing) and ported laparoscopic devices. Only the automated cleaning of ported devices achieved 10(3)-10(4)-fold reduction in bacterial numbers. Sonication alone (no flushing of inner channel) did not effectively remove soil or organisms from the inner channel. Our findings indicate that non-ported accessory devices cannot be as reliably cleaned as ported devices regardless of the cleaning method used. If non-ported accessory devices are reprocessed, they should be cleaned using retro-flushing in an automated narrow lumen cleaner.

Multilaboratory comparison of proficiencies in susceptibility testing of Helicobacter pylori and correlation between agar dilution and E test methods.

Susceptibility testing was performed at seven Canadian microbiology laboratories and the Helicobacter Reference Laboratory, Halifax, Nova Scotia, Canada, to assess susceptibility testing proficiency and the reproducibility of the results for clarithromycin and metronidazole and to compare the Epsilometer test (E test) method to the agar dilution reference method. Control strain Helicobacter pylori ATCC 43504 (American Type Culture Collection) and 13 clinical isolates (plus duplicates of four of these strains including ATCC 43504) were tested blindly. The National Committee for Clinical Laboratory Standards (NCCLS) guidelines for agar dilution testing were followed, and the same suspension of organisms was used for agar dilution and E test. Antimicrobials and E test strips were provided to the investigators. Methods were provided on a website (www.Helicobactercanada.org). Each center reported MICs within the stated range for strain ATCC 43504. Compared to the average MICs, interlaboratory agreements within 2 log(2) dilutions were 90% (range, 69 to 100%) for clarithromycin by agar dilution, with seven very major errors [VMEs], and 85% (range, 65 to 100%) by E test, with three VMEs. Interlaboratory agreements within 2 log(2) dilutions were 83% (range, 50 to 100%) for metronidazole by agar dilution, with six VMEs and eight major errors (MEs), and 75% (range, 50 to 94%) by E test, with four VMEs and four MEs. At lower and higher concentrations of antibiotic, E test MICs were slightly different from agar dilution MICs, but these differences did not result in errors. When a standardized protocol based on NCCLS guidelines was used, most participants in this study correctly identified clarithromycin- and metronidazole-susceptible and -resistant strains of H. pylori 93% of the time by either the agar dilution or E test method, and the numbers of errors were relatively equivalent by both methods.

The diagnosis of Clostridium difficile-associated diarrhea: comparison of Triage C. difficile panel, EIA for Tox A/B and cytotoxin assays.

This study prospectively compared; Triage(R) C. difficile test (TCT), TechLab C. difficile toxin A-B enzyme immuno-assay (EIA), and cell-culture cytotoxin test (CT). Of the 400 stools tested, 99 were positive by any test with 92, 41 and 58 detected by TCT, EIA and CT, respectively. Culture of discordant samples indicated that 52 contained C. difficile (42 toxigenic, 10 non-toxigenic), 10 contained Clostridium species and 2 had no detectable clostridium isolates. There were 21/42 toxigenic C. difficile isolates from 17 patients whose stools were negative when originally tested by CT. Review of available patient charts indicated that 12/14 did not previously or currently have C. difficile associated diarrhea, whereas 2 patients developed disease within a few days. Compared to CT as the gold standard, the sensitivity and specificity were; 93%, 89% and 66%, 99% for TCT and EIA respectively. The 8 stool samples with Toxin A(-) Toxin B(+) isolates were detected in 8, 4, and 6 samples by TCT, EIA and CT, respectively. In summary, TCT as a screening test allowed reliable reporting for 85% of stools on the day of receipt. For the 15% of stools requiring further testing we recommend the use of CT.

Development of a Canadian standardized protocol for subtyping methicillin-resistant Staphylococcus aureus using pulsed-field gel electrophoresis.

A panel of 24 methicillin-resistant Staphylococcus aureus strains was distributed to 15 laboratories in Canada to evaluate their in-house pulsed-field gel electrophoresis (PFGE) protocols and interpretation criteria. Attempts to compare fingerprint images using computer-aided analysis were not successful due to variability in individual laboratory PFGE protocols. In addition, individual site interpretation of the fingerprint patterns was inadequate, as 7 of 13 sites (54%) made at least one error in interpreting the fingerprints from the panel. A 2-day standardized PFGE protocol (culture to gel image) was developed and distributed to all of the sites. Each site was requested to use the standardized protocol on five strains from the original panel. Thirteen sites submitted gel images for comparisons. The protocol demonstrated excellent reproducibility and allowed interlaboratory comparisons with Molecular Analyst DST software (Bio-Rad) and 1.5% band tolerance.

Multiplex PCR for the detection of tetracycline resistant genes.

Specific primer pairs were selected for the PCR amplification of 14 tetracycline resistant genes commonly found in Gram positive and Gram negative organisms. Combinations of primer pairs were used in multiplex PCR reactions to detect specific groups of tet genes as follows; Group I tet (B), tet (C), tet (D); Group II tet (A), tet (E), tet (G); Group III tet (K), tet (L), tet (M), tet (O), tet (S); Group IV tetA (P), tet (Q), tet (X). To test the multiplex PCR, Groups I and II were used on 25 clinical isolates of Salmonella enterica serovar Typhimurium DT104. Group III primers were used to investigate 19 clinical isolates of methicillin-resistant Staphylococcus aureus. Multiplex PCR should result in significant savings in terms of labour and cost in analysis of a large number of strains when compared with using an individual PCR for targeting each gene. It may also be a useful method to differentiate the types of tetracycline resistance when used as an additional marker for the purpose of outbreak investigation and surveillance.

A new hydrogen peroxide--based medical-device detergent with germicidal properties: comparison with enzymatic cleaners.

BACKGROUND: The objective of this study was to evaluate the efficacy of the cleaning and bacterial killing ability of a new non-enzyme-based formulation (killing detergent solution [KDS]) compared with commercially available enzymatic detergents that included Metrizyme (Metrex Research Division of Sybron Canada Ltd. Morrisburg, Ontario) and Gzyme (Germiphene Corp, Brantford, Ontario). KDS is a hydrogen peroxide-based detergent formulation that combines cleaning efficacy with the ability to kill microorganisms. The KDS formulation helps ensure the protection of the health care worker from infectious risk during the soaking and cleaning stages of medical device reprocessing and reduces the bioburden on devices before sterilization/disinfection. METHODS: Test organisms that included Enterococcus faecalis, Salmonella choleraesuis, Staphylococcus aureus, and Pseudomonas aeruginosa were suspended in artificial test soil (ATS-B; patent submitted), inoculated at 10(6) colonyforming units per carrier and dried overnight before detergent exposure. The ATS-B mimics the blood, protein, carbohydrate, and endotoxin levels of patient-used medical devices. Plastic lumen carriers and a flexible colonoscope were used for surface and simulated-use testing, respectively. RESULTS: The results for the microbial challenge dried onto polyvinyl chloride (PVC) carriers demonstrated that the ability of KDS to remove protein, blood, carbohydrate, and endotoxin from surface test carriers was as effective as the enzyme detergents that were evaluated. Furthermore, KDS was able to effect approximately a 5-Log(10) reduction in microbial loads with a 3-minute exposure at room temperature, whereas none of the other detergents were as effective. In simulated-use testing of a soiled colonoscope, KDS was significantly better at ensuring microbial killing compared with Gzyme and Metrizyme and was equivalent to the enzymatic detergents in cleaning ability. CONCLUSIONS: In summary the KDS has excellent microbial-killing ability in 3-minute exposures at room temperature and cleans as well as the existing enzymatic detergent formulations that were tested.