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.

Simulated-use evaluation of rapid ChannelCheck™ cleaning test for optimal detection of organic residues in flexible endoscope channels.

BACKGROUND: The need to monitor manual cleaning of high-risk endoscopes is recommended or more so required by the current endoscope reprocessing guidelines. The objective of this study was to establish the optimal extraction volume for colonoscopes and bronchoscopes and demonstrate the extraction efficacy for the ChannelCheck™ rapid test. METHODS: The test soil utilized as a positive control was ATS2015 containing 20% defibrinated bovine blood. The extraction from the instrument channel of a colonoscope and bronchoscope was evaluated to establish the optimal extraction volume and the extraction efficacy for protein, carbohydrate and haemoglobin. RESULTS: Of the extraction volumes tested, 10 mL was optimal for both colonoscopes and bronchoscopes. The extraction efficacy was 91% for carbohydrate, 83.7% for haemoglobin and 82.4% for protein. CONCLUSIONS: The limit of detection for these analytes by the ChannelCheck rapid test meet or exceed the established levels that correlate with adequate manual cleaning of flexible endoscopes.

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.

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).

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.

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.

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.

Analysis of microbiological trends in peritoneal dialysis-related peritonitis from 1991 to 1998.

The microbial cause of peritoneal dialysis-related peritonitis is an important determinant of clinical outcome and the basis of widely used treatment guidelines. Five hundred forty-six cases of peritonitis in 374 patients from 1991 to 1998 were analyzed. The rate of peritonitis declined significantly from 1.37 episodes/patient-year in 1991 to 0.55 episode/patient-year in 1998 (P = 0.02). The rate of Gram-positive peritonitis decreased significantly from 0.75 to 0.28 episode/patient-year during the same period (P = 0.02). Conversely, the occurrence of Gram-negative peritonitis remained constant at approximately 0.16 episode/patient-year (P = 0.28). Staphylococcus epidermidis and Staphylococcus aureus were the most common causes of peritonitis, isolated in 27.8% and 19.3% of the culture-positive cases, respectively. A distinct decrease in peritonitis caused by S epidermidis was observed, with 0.40 episode/patient-year in 1991 compared with 0.11 to 0.20 episode/patient-year during subsequent years. The rate of infections caused by S aureus decreased significantly over time from a high of 0.21 episode/patient-year in 1992 to a low of 0.04 episode/patient-year in 1998 (P = 0.01). Pseudomonas aeruginosa, Escherichia coli, and KLEBSIELLA: species were the most common causes of Gram-negative peritonitis, identified in 7.1%, 6.8%, and 5.2% of culture-positive cases, respectively. The most dramatic increase in antibiotic resistance was seen among S epidermidis. From 1991 and 1992 to 1997 and 1998, resistance to ciprofloxacin increased from 5.4% to 47.8% (P = 0.003), and resistance to methicillin increased from 18.9% to 73.9% (P = 0.03). Our study showed significant trends in the causative pathogens of peritoneal dialysis-related peritonitis and dramatic increases in antibiotic resistance. These data support further study and warrant reevaluation of current treatment practices.

A morphological study of penile chancroid lesions in human immunodeficiency virus (HIV)-positive and -negative African men with a hypothesis concerning the role of chancroid in HIV transmission.

Chancroid, the most common cause of genital ulceration in Africa, is known to be associated epidemiologically with heterosexual transmission of human immunodeficiency virus (HIV). The pathophysiological mechanisms by which chancroid might facilitate the spread of HIV are obscure. To investigate the role of chancroid in HIV transmission, the authors studied the histological features of biopsies from 11 men with penile chancroid lesions including five who were serologically positive for HIV. The histomorphologic and immunophenotypic nature of the inflammatory infiltrates suggests that there is a significant role for cell-mediated immunity in the host response to Hemophilus ducreyi infection. This response may be critical to the role of chancroid in HIV transmission.

Transmission of Ureaplasma urealyticum from mothers to full and preterm infants.

This study assessed maternal genital colonization and subsequent neonatal transmission rate of Ureaplasma urealyticum in pregnant women in an average socioeconomic population. In addition very low birth weight infants were assessed to determine whether the presence of U. urealyticum correlated with increased risk of developing respiratory problems. The study group consisted of 108 sequential full term mothers and 104 preterm mothers delivering in a tertiary care hospital in central Canada. The genital carriage rates (assessed using placental sampling) of ureaplasmas in term and preterm mothers were 25.9 and 19.2%, respectively (P = 0.3185). Acquisition of ureaplasmas in the neonatal respiratory tract of neonates occurred significantly (P = 0.0182) more often in preterm neonates (11 of 130; 8.5%) than in term neonates (2 of 110; 0.9%). Very low birth weight (VLBW) infants (< or = 1500 g) were at greater risk (P = 0.042) of acquiring ureaplasmas in their respiratory tracts (5 of 26; 19%) than larger preterm neonates (6 of 104; 5.8%). All VLBW infants with respiratory colonization by ureaplasmas (5 of 5) developed bronchopulmonary dysplasia compared with 33% (7 of 21) of VLBW neonates without ureaplasmas (P = 0.028). This difference in bronchopulmonary dysplasia development among VLBW infants was independent of further stratification by birth weight. These VLBW neonates with ureaplasmas also stayed significantly (P = 0.037) longer in the neonatal intensive care unit (43.6 +/- 10.4 days) than did other preterm neonates (22.1 +/- 20.8 days). Our results demonstrate that VLBW preterm neonates have increased risk of acquiring U. urealyticum.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacterial killing ability of 10% ethylene oxide plus 90% hydrochlorofluorocarbon sterilizing gas.

OBJECTIVES: To use a serum and salt challenge in narrow-lumen carriers to evaluate a 10% ethylene oxide plus 90% hydrochlorofluorocarbon (EO-HCFC) sterilant mixture in a retrofitted 12/88 sterilizer as an alternative to the banned chlorofluorocarbon-ethylene oxide (EO) sterilant mixture. DESIGN: An EO-HCFC sterilizing gas mixture in a retrofitted 12/88 sterilizer was compared to 100% ethylene oxide (100% EO) sterilizing gas to determine its relative ability to kill seven different bacteria (Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis, Bacillus subtilis spores, Bacillus stearothermophilus spores, Bacillus circulans spores, and Mycobacterium chelonei) in the presence or absence of a combined 10% serum and 0.65% salt challenge using both penicylinders (PC) and long narrow-lumen (LU) carriers. RESULTS: The EO-HCFC sterilant mixture (96% sterile carriers) was equivalent to the 100% EO sterilant (98% sterile carriers) for killing vegetative organisms, as well as spore suspensions, on the 27 PC and 27 LU carriers in the absence of serum and salt. In the presence of serum and salt, the EO-HCFC sterilant mixture was markedly better than the 100% EO sterilant at reducing the bacterial load on the 63 PC carriers (95% vs 62% sterile PC carriers, respectively), whereas both sterilizers were equivalent for the 63 LU carriers (49% vs 40% sterile LU carriers, respectively). Of the seven test organisms, E faecalis, B subtilis, B stearothermophilus, and B circulans were the most difficult to kill for both PC and LU carriers when serum and salt were present. CONCLUSIONS: The data presented in this report indicate that the EO-HCFC sterilant mixture is an effective alternative for gas sterilization. Indeed, the efficiency of bacterial killing for the EO-HCFC sterilant mixture was similar to that achieved by the 12/88 EO-CFC sterilant mixture.

Comparison of ion plasma, vaporized hydrogen peroxide, and 100% ethylene oxide sterilizers to the 12/88 ethylene oxide gas sterilizer.

OBJECTIVE: The performance of a standard gas sterilizer, which uses a mixture of 12% ethylene oxide (EtO) and 88% chlorofluorocarbon as the sterilizing gas (12/88), was compared to selected gas, ion plasma, and vaporized hydrogen peroxide (H2O2) sterilizers that do not use chlorofluorocarbons. The effect of serum and salt on sterilizer performance was evaluated. DESIGN: Test carriers (porcelain and stainless steel penicylinders, or 125-cm lengths of plastic tubing [internal diameter of 3.2 mm]) were inoculated with Escherichia coli, Enterococcus faecalis, Pseudomonas aeruginosa, Mycobacterium chelonei, Bacillus stearothermophilus spores, Bacillus subtilis spores, and Bacillus circulans spores and then subjected to sterilization using 12/88, 100% EtO, ion plasma, or vaporized H2O2. The bacterial inoculum was prepared with and without 10% serum and 0.65% salt, and the residual bacterial load after sterilization as determined using viable counts. RESULTS: All of the sterilizers tested effected a six-log10 reduction of the bacterial inoculum on penicylinders, unless 10% serum and 0.65% salt were present, in which case the 100% EtO, vaporized H2O2, and ion plasma sterilizers were not as effective as the 12/88 sterilizer. None of the sterilizers could eradicate 10(6) CFU of all of the bacteria in 10% serum and 0.65% salt when inoculated inside a narrow lumen. CONCLUSIONS: The margin of safety for the 100% EtO, vaporized H2O2, and ion plasma sterilizers is less than that of the 12/88 sterilizer. The inability of all sterilizers, including the 12/88, to kill organisms in narrow lumens reliably when serum and salt were present raises concern about the current practice of gas sterilization of flexible endoscopes.

Methicillin-resistant Staphylococcus aureus in tertiary care institutions on the Canadian prairies 1990-1992.

OBJECTIVE: To review experience with methicillin-resistant Staphylococcus aureus (MRSA) in tertiary acute-care teaching hospitals on the Canadian prairies. DESIGN: Retrospective review for a 36-month period, 1990 through 1992. SETTING: Five tertiary acute-care teaching hospitals in three Canadian prairie provinces. METHODS: MRSA isolates and susceptibility were identified through the clinical microbiology laboratory at each institution. For each patient, data collected included duration of institutional residence prior to isolation, patient ethnic background, age, sex, and antimicrobial susceptibility. Epidemiologic typing of strains used restriction fragment length polymorphism analysis by pulsed-field gel electrophoresis. RESULTS: Two hundred fifty-nine MRSA isolates were identified in 135 patients during the 36 months, with substantial institutional variation in number of isolates. No consistent increase in yearly numbers of isolates was apparent. Patients usually had MRSA identified at admission (62%); only one of five centers had the majority of isolates acquired nosocomially. Patients with MRSA present at admission were more frequently of aboriginal (First Nations) ethnicity (62% compared with 14% of nosocomial; P < 0.001). Pulsed-field gel electrophoresis of 167 isolates from 135 patients revealed 46 different strains with little interprovincial or interinstitutional identity of strains. CONCLUSIONS: MRSA isolated in patients in tertiary care institutions in these three Canadian provinces usually is acquired prior to admission. A disproportionate number of isolates are identified in aboriginal Canadians. Epidemiologic typing was consistent with a polyclonal origin of MRSA in this geographic area.

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.

Worst-case soiling levels for patient-used flexible endoscopes before and after cleaning.

BACKGROUND: The soiling levels of patient-used narrow-lumened flexible endoscopes were assessed for bronchoscopes, duodenoscopes, and colonoscopes. The effect of cleaning on the soil composition and concentration was evaluated. DESIGN: Suction channels from 10 each of bronchoscopes, duodenoscopes used for endoscopic retrograde cholangiopancreatography, and colonoscopes were assessed immediately after patient use for the levels of bilirubin, hemoglobin, protein, sodium ion, carbohydrate, endotoxin, and viable bacteria. Another 10 suction channels of each type of endoscope were evaluated for the same components after routine cleaning but before processing by high-level disinfection or sterilization for subsequent clinical use. RESULTS: Recognizing that only soluble components could be quantified, the worst-case soil levels in the suction channels (the average surface area of these channels was 45.6 cm(2), 149.8 cm,(2) and 192.0 cm(2) for bronchoscopes, duodenoscopes, and colonoscopes, respectively) were protein 115 microg/cm(2), sodium ion 7.4 micromol/cm(2), hemoglobin 85 microg/cm(2), bilirubin 299 nmol/cm(2), carbohydrate 29.1 microg/cm(2), endotoxin 9852 endotoxin units/cm(2), and bacteria 7.1 (log(10)) colony-forming units (CFU)/cm(2). Colonoscopes had 4 to 5 times greater soiling on average compared with the other endoscope types. Routine cleaning reduced the levels of bilirubin to below the limits of detection for all endoscopes evaluated (limits of detection were <1 nmol/mL). After cleaning, residual hemoglobin was detectable in bronchoscopes only. After cleaning, the levels of protein, endotoxin, and sodium ion all were reduced fivefold to tenfold for all types of endoscopes. Carbohydrate was reduced to lower than the limit of detection for all endoscopes after cleaning, except the duodenoscopes. The average load of viable bacteria was reduced from 3 log(10) to 5 log(10) CFU/cm(2) (which represents 5.9-9.5 log(10) CFU/endoscope channel) after patient use to approximately 2 log(10) CFU/cm(2) (which represents 3.2-5.3 log(10) CFU/endoscope channel) after cleaning. CONCLUSIONS: These data demonstrated that cleaning effectively reduced or eliminated many components of soil, but a substantial amount of viable bacteria and protein remained. Hemoglobin levels in before samples indicated that blood was not present in high concentrations in the suction channels of the majority of flexible endoscope samples. Soil that mimics the worst-case composition from patient-used endoscopes would be ideal for simulated-use studies for such medical devices.

Comparison of liquid chemical sterilization with peracetic acid and ethylene oxide sterilization for long narrow lumens.

The aim of this study was to determine how well peracetic acid liquid chemical sterilization (LCPAS) killed test organisms in the presence of 10% fetal bovine serum and 0.65% salt challenge (RPMI-S) compared with a 100% ethylene oxide (ETO) sterilizer and an ETO hydrochlorofluorocarbon (ETO-HCFC) sterilization method with long (125 cm), narrow (3-mm internal diameter) flexible lumens as the test carrier. The inoculated lumens were dried overnight before processing. The test organisms included Mycobacterium chelonei, Enterococcus faecalis, and Bacillus subtilis. For all 3 organisms tested, the LCPAS process resulted in a 6 log10 reduction in bacterial load compared with a 2.5 log10 to 6 log10 reduction for the 100% ETO and ETO-HCFC sterilizers. Sterilization was achieved for 100%, 61%, and 67% of the lumen test carriers for the LCPAS, 100% ETO, and ETO-HCFC sterilizers, respectively. The data indicate that of the sterilization methods evaluated, LCPAS was the most effective for sterilizing narrow flexible lumens in the presence of residual inorganic and organic soil. This effectiveness was achieved through a combination of organism wash-off and peracetic acid sterilant killing of organisms. Salt was the major compounding factor for effective ETO gas sterilization, because carriers inoculated with organisms in 10% fetal bovine serum alone all were sterilized by both 100% ETO and ETO-HCFC sterilization methods. Our data support the critical need to ensure adequate precleaning of narrow flexible lumen endoscopes before any sterilization method.

A transport method for swab specimens submitted for aerobic and anaerobic bacteriology.

The need for separate swab transport methods for aerobes and anaerobes may result in inadequate transport of specimens for anaerobic bacteriology. Most microbiology laboratories in Australia rely on Stuart's transport medium to protect anaerobic bacteria. This paper presents a new, simple transport medium (Transport Deep) suitable for sue with aerobes and anaerobes. Comparative evaluations demonstrate that Transport Deep is as good as Stuart's medium for the maintenance of fastidious bacteria and is far superior for the protection of even extremely oxygen-sensitive anaerobes. This medium has been used successfully in a large Sydney hospital for more than a year. It is proposed that Transport Deep be used on a routine basis for all swab specimens.

Methicillin-resistant Staphylococcus aureus. Optimization of the agar screen plate method.

Swab inoculation of oxacillin agar screen plates was compared with drop inoculation for detection of methicillin-resistant Staphylococcus aureus. The poor sensitivity of the swab method (59%) was related to heteroresistance of the S. aureus isolates. We recommend the drop method (100% sensitivity) because interpretation of results was significantly easier, making it more reliable.