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Nosocomial Infection and Pseudoinfection from Contaminated Endoscopes and Bronchoscopes -- Wisconsin and Missouri

Flexible fiber-optic endoscopes are widely used in the United States for diagnostic and therapeutic procedures. Between uses, endoscopes should be cleaned and disinfected either manually or by using automated machines. However, outbreaks have occurred among patients exposed to contaminated endoscopes or to inadequately disinfected bronchoscopes (1-4). This report summarizes one outbreak of nosocomially acquired infection (Wisconsin) and one of pseudoinfection (Missouri) linked to endoscopes contaminated during cleaning and disinfection by automated reprocessing machines. Wisconsin

From October 1986 through June 1988, at a hospital in Wisconsin, Pseudomonas aeruginosa colonization or infection of the biliary tract, respiratory tract, or bloodstream occurred in 16 (6.7%) of 240 patients undergoing endoscopic retrograde cholangiopancreatography (ERCP) and in 99 (8.9%) of 1109 patients undergoing other upper gastrointestinal (UGI) endoscopic procedures. The endoscopes were routinely reprocessed using an Olympus EW-10* automated reprocessing machine that flushed with a detergent solution, disinfected with one of two liquid chemical germicides (2% glutaraldehyde; 2% glutaraldehyde/7.05% phenol/1.2% sodium phenate diluted 1:16 in tap water), and rinsed with tap water.

An investigation performed by the hospital in June 1988 indicated that a thick biofilm of P. aeruginosa had formed in the detergent holding tank, inlet water hose, and air vents of the automated machine. Attempts to disinfect the machine by the manufacturer's instructions using commercial preparations of glutaraldehyde were unsuccessful.

P. aeruginosa serotype 10 was the predominant serotype recovered from the automated machine, from available isolates from patients with postendoscopy colonization or infection, and from endoscopes that had been sampled after disinfection in the machine. Molecular subtyping (by immunoblot of whole-cell lysates and by pulsed-field electrophoresis of DraI endonuclease-digested DNA) confirmed that the P. aeruginosa serotype 10 isolates recovered from the reprocessing machine and from infected patients were identical.

In July 1988, hospital personnel began manually rinsing machine-washed endoscope channels and external surfaces with 70% isopropyl alcohol and drying the channels and surfaces with forced air for 10-20 minutes. When compared with rates of post-UGI endoscopy P. aeruginosa colonization or infection for October 1986-June 1988, rates for July 1988-December 1989 were lower (one (0.6%) of 175 patients undergoing ERCP (p less than 0.01) and 27 (3.3%) of 821 patients undergoing other UGI endoscopies (p less than 0.01)), although the automated machine remained colonized with P. aeruginosa. No additional cases have occurred. Missouri

In August 1990, infection-control personnel in a hospital in Missouri noted an increase in the number of Mycobacterium chelonae isolates (20 isolates during January-August 1990, compared with a median of six isolates per year during 1984-1989).

Microbiology and patient records from January 1, 1984, through September 25, 1990, were reviewed. From January 1, 1984, through December 4, 1989 (defined as the baseline period), 5200 patients underwent bronchoscopy or endoscopy on one surgical service; five (0.1%) of these patients had respiratory or biliary cultures positive for M. chelonae. In comparison, from December 5, 1989 (when the first case in a cluster of cases with a unique strain of M. chelonae was identified), through September 25, 1990, 1270 patients on the same service underwent bronchoscopy or endoscopy; 14 (1.1%) of these patients had respiratory or biliary cultures positive for M. chelonae. However, none of the 14 patients had evidence of invasive M. chelonae infection, and none had additional cultures positive for M. chelonae when bronchoscopy was repeated, suggesting the occurrence of pseudoinfection.

A phenotypically unique strain of M. chelonae subsp. abscessus, highly resistant to cefoxitin (minimum inhibitory concentration (MIC) greater than 256 ug/mL), was recovered from all 14 patients with bronchoscopic- or endoscopic-related pseudoinfections and from the rinse water from the automated reprocessing machine. This strain differed from 13 control isolates of M. chelonae obtained from patients elsewhere in the hospital (5).

Beginning in May 1988, bronchoscopes and endoscopes from the surgical service had been reprocessed after each use with a Keymed Auto Disinfector 2 (manufactured by Olympus Corporation), which washed the endoscopes with a detergent solution, disinfected with 2.0% glutaraldehyde, and rinsed with tap water. In addition, the bronchoscopes were reprocessed each night with a standard ethylene oxide gas sterilization cycle. In September 1990, following recognition of the increased rate of pseudoinfection, the endoscope reprocessing procedure was modified: sterile water was substituted for tap water in the machine rinse cycle, the disinfection cycle was increased from 10 to 20 minutes, rinsing was done manually with 70% alcohol, and forced air was used for drying. No further pseudoinfections occurred until December 1990, when a different strain of M. chelonae was isolated from bronchial washings of two patients undergoing bronchoscopy on the same service; however, the organism was not isolated from the reprocessing machine. Since use of the automated reprocessing machine was discontinued in February 1991, M. chelonae has not been isolated from patients on this service. Reported by: CJ Alvarado, MS, SM Stolz, MS, DG Maki, MD, Univ of Wisconsin Hospital and Clinics, Madison, Wisconsin. V Fraser, MD, M Jones, S O'Rourke, Barnes Hospital, Saint Louis, Missouri. RJ Wallace, Jr, MD, Univ of Texas Health Science Center, Tyler, Texas. Center for Devices and Radiologic Health, Food and Drug Administration. Hospital Infections Program, National Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: In the United States, use of automated endoscope reprocessing machines has increased--in part because of the complex and time-consuming process of manually cleaning and disinfecting endoscopes. CDC has previously recommended that diagnostic and therapeutic devices that contact mucous membranes during use (e.g., endoscopes and bronchoscopes) should be either sterilized or subjected to high-level disinfection (6). However, the findings in this report emphasize the potential for some automated endoscope reprocessing machines to become colonized with heterotrophic organisms such as P. aeruginosa and M. chelonae. Such colonization may then result in nosocomial infections or pseudoinfections in patients undergoing endoscopic procedures. Contaminated endoscopes, particularly when used to perform invasive procedures such as mucosal biopsies or ERCP, have been associated with a variety of problems, including potentially life-threatening infections such as septicemia or cholangitis (7-11).

In both hospitals described in this report, the automated reprocessing machines were identified as the source of contamination. This contamination was present in multiple sites, including the detergent and water holding tanks, water hoses, and air vents. At least three factors contributed to the problem: 1) the design of the machines hampered their disassembly, cleaning, and decontamination; 2) the detergent, disinfectant, and tap water were reused several times in the Auto Disinfector 2; and 3) reservoirs and tubing of both the EW-10 and Auto Disinfector 2 remained moist or filled with fluid for extended periods, providing several potential sources for contamination before disinfection or for recontamination during rinsing. Repeated attempts to eliminate the microbial contamination from internal tubing and reservoirs of the reprocessing machines were unsuccessful.

In April 1990, at the request of the Food and Drug Administration (FDA), Olympus Corporation mailed a medical device safety alert to all consignees of EW-10 and of a similar, but more recent, model machine (EW-20). The alert recommended that all endoscope channels be rinsed with 70% isopropyl alcohol and suctioned with forced air after machine reprocessing. Although terminal alcohol rinsing of endoscopes followed by forced-air drying was initiated at both hospitals, this procedure has not been rigorously evaluated and does not ensure elimination of microbial contamination originating from the reprocessing machine. In addition, in May 1990, FDA classified Olympus' action as a Class II recall of the EW-10 and EW-20 machines (i.e., Olympus has agreed that no models of this category of machine will be sold until the contamination problem has been resolved and FDA has granted approval).

To assist CDC and FDA in determining the extent of contamination for flexible fiber-optic endoscopes, physicians are asked to report episodes of endoscopy-related colonization/infection or pseudoinfection in patients undergoing gastrointestinal endoscopy or bronchoscopy through state health departments to the Epidemiology Branch, Hospital Infections Program, National Center for Infectious Diseases, Mailstop A-07, CDC, 1600 Clifton Road, NE, Atlanta, GA 30333; telephone (404) 639-1550.


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  3. Wheeler PW, Lancaster D, Kaiser AB. Bronchopulmonary cross-colonization and infection related to mycobacterial contamination of suction valves of bronchoscopes. J Infect Dis 1989;159:954-8.

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  5. Fraser V, Jones M, Murray P, Medoff G, Zhang X, Wallace RJ Jr. Nosocomial respiratory outbreak of M. chelonae linked to an automated disinfection machine (Abstract). In: Program and abstracts of the 91st annual meeting of the American Society for Microbiology. Washington, DC: American Society for Microbiology, 1991:425.

  6. Garner JS, Favero MS. Guideline for handwashing and hospital environmental control, 1985. Atlanta: US Department of Health and Human Services, Public Health Service, CDC, 1985; HHS publication no. 99-1117.

  7. Elson CO, Hattori K, Blackstone MO. Polymicrobial sepsis following endoscopic retrograde cholangiopancreatography. Gastroenterology 1975;69:507-10.

  8. Parker HW, Geenan JE, Bjork JT, Stewart ET. A prospective analysis of fever and bacteremia following ERCP. Gastrointest Endosc 1979;25:102-3.

  9. Classen DC, Jacobson JA, Burke JP, Jacobson JT, Evans RS. Serious pseudomonas infections associated with endoscopic retrograde cholangiopancreatography. Am J Med 1988;84:590-6.

  10. Favero MS. Strategies for disinfection and sterilization of endoscopes: the gap between basic principles and actual practice. Infect Control Hosp Epidemiol 1991;12:279-81.

  11. Axon ATR, Cowen AE, Bond WW, Tandon RK, Fleisher DE, Bottrill PM. Disinfection and endoscopy: working party report to the World Congresses of Gastroenterology, Sydney 1990. Journal of Gastroenterology and Hepatology 1991;6:23-47.

*Use of trade names is for identification only and does not imply endorsement by the Public Health Service or the U.S. Department of Health and Human Services.

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