Two cases of Enterococcus faecalis bacteremia associated with a hemodialysis machine

Outbreaks of healthcare-associated infections linked to water-containing hospital equipment: a literature review

BACKGROUND

Healthcare-associated infections (HAIs) are a significant cause of morbidity and mortality in hospitalized patients. Water in the environment can be a source of infection linked to outbreaks and environmental transmission in hospitals. Water safety in hospitals remains a challenge. This article has summarized available scientific literature to obtain an overview of outbreaks linked to water-containing hospital equipment and strategies to prevent such outbreaks.

METHODS

We made a list of water-containing hospital equipment and devices in which water is being used in a semi-closed circuit. A literature search was performed in PubMed with a search strategy containing the names of these medical devices and one or more of the following words: outbreak, environmental contamination, transmission, infection. For each medical device, we summarized the following information: the function of the medical device, causes of contamination, the described outbreaks and possible prevention strategies.

RESULTS

The following water-containing medical equipment  or devices were identified: heater-cooler units, hemodialysis equipment, neonatal incubators, dental unit waterlines, fluid warmers, nebulizers, water traps, water baths, blanketrol, scalp cooling, and thermic stimulators. Of the latter three, no literature could be found. Of all other devices, one or more outbreaks associated with these devices were reported in the literature.

CONCLUSIONS

The water reservoirs in water-containing medical devices can be a source of microbial growth and transmissions to patients, despite the semi-closed water circuit. Proper handling and proper cleaning and disinfection can help to reduce the microbial burden and, consequently, transmission to patients. However, these devices are often difficult to clean and disinfect because they cannot be adequately opened or disassembled, and the manufacturer's cleaning guidelines are often not feasible to execute. The development of equipment without water or fluid containers should be stimulated. Precise cleaning and disinfection guidelines and instructions are essential for instructing healthcare workers and hospital cleaning staff to prevent potential transmission to patients.

Evaluation of one-way valves used in medical devices for prevention of cross-contamination

BACKGROUND

One-way valves used in day use devices (used on multiple patients throughout a day without reprocessing between patients) are intended to reduce the potential for cross-contamination between patients resulting from the backflow of patient fluids. One-way valves are typically designed to withstand high levels of back pressure before failure; however, they may not be explicitly designed as a means of infection control as used in medical device applications.

METHODS

Five different medical grade one-way valves were placed in low pressure configurations. After flushing in the intended direction of flow, bacteriophage, bacteria, or dye was placed patient side for 24 hours. The upstream device side of the valve was then evaluated for microbial growth or presence of visible dye.

RESULTS

Leakage (ie, backflow) of the microorganisms occurred with a variety of one-way valve designs across a range of fluid properties tested.

CONCLUSIONS

This study describes testing of the one-way valves (component-level testing) for the potential of cross-contamination. Although day use medical device systems may use numerous other factors to prevent patient cross-contamination, this work demonstrates that one-way valves themselves may not prevent leakage of contaminated fluid if the fluid is able to reach the upstream side of the one-way valve.

Contaminated Product Water as the Source ofPhialemonium curvatumBloodstream Infection among Patients Undergoing Hemodialysis

Objective.

We investigated a cluster of cases of bloodstream infection (BSI) due to the moldPhialemoniumat a hemodialysis center in Illinois and conducted a cohort study to identify risk factors.

Design.

Environmental assessment and cohort study.

Setting.

A hemodialysis center in a tertiary care hospital.

Methods.

A case patient was defined as a person who underwent dialysis at the center and had a blood sample that tested positive forPhialemonium curvatumon culture. We reviewed microbiology and medical records and tested water, surface, and dialysate samples by culture. Molds isolated from environmental and clinical specimens were identified by their morphological features and confirmed by sequencing DNA.

Results.

We identified 2 case patients with BSI due toP. curvatum. Both became febrile and hypotensive while undergoing dialysis on the same machine at the same treatment station, although on different days. Dialysis machines were equipped with waste handling option ports that are used to discard dialyzer priming fluid. We isolatedP. curvatumfrom the product water (ie, water used for dialysis purposes) at 2 of 19 treatment stations, one of which was the implicated station.

Conclusion.

The source ofP. curvatumwas likely the water distribution system. To our knowledge, this is the first report of patients acquiring a mold BSI from contaminated product water. The route of exposure in these cases of BSI due toP. curvatummay be related to the malfunction and improper maintenance of the waste handling option ports. Waste handling option ports have been previously implicated as the source of bacterial BSI due to the backflow of waste fluid into a patient's blood line. No additional cases of infection were noted after remediation of the water distribution system and after discontinuing use of waste handling option ports at the facility.

Halomonas, a newly recognized human pathogen causing infections and contamination in a dialysis center: three new species

Our Renal Care Center (RCC) is a separate building, performing almost 2500 outpatient dialysis runs per month. In May 2007, 2 patients developed, days apart, bacteremia with an apparently identical nonfermentative Gram-negative rod. Because of difficulty identifying the organism, testing in the Biolog system identified them as a Halomonas species. Sequencing of approximately 1500 bases of the 16S rRNA gene in both organisms in 3 reference laboratories confirmed, searching against 3 databases, that the organisms were identical and were Halomonas species. There were 54 recognized species of this genus, associated with marine or saline sites. Initial attempts at environmental isolation as primary cultures, including a 4% salt agar plate, or initial incubation in 6.5% salt broth enrichment culture with subculture to agar, to exploit the halophilicity of Halomonas, were successful in demonstrating the colonies seen in the blood cultures, only from sites not contaminated with other organisms, because of competing growth. A more selective method was developed for use on samples suspected to be heavily contaminated with other organisms, using the strategy of increased salt concentration in a broth enrichment culture to further exploit Halomonas halotolerance, and thereby inhibit other organisms. A 16.5% salt concentration in brain-heart infusion broth, incubated at 35 degrees C for 48-72 hours, then subcultured to agar plates incubated in room air at 35 degrees C, proved optimal for selection and secondary isolation. With a combination of these techniques, 14/15 cultures of dialysates and 10/38 from the outflow pathways of the machines were Halomonas positive, compared to 0/31 cultures from the inflow side of the machines (including water supplies and storing, mixing, and preparation tanks). The exception was sites associated with or downstream of bicarbonate influx, 12/54 of which were positive. Two other local hospitals' dialysis centers, and our own inpatient dialysis facility, were cultured at sites that yielded Halomonas from our RCC, and Halomonas was not isolated. Further study by 16S rRNA gene sequencing and DNA-DNA hybridization revealed the cultures represented 3 novel species: 1 (H. stevensii sp. nov.) in the patients and environment and 2 (H. hamiltonii sp. nov., H. johnsoniae sp. nov.) in the environment, most closely related to H. magadiensis. Of 35 speciated isolates, 22 were H. stevensii, 10 H. johnsoniae, and 3 H. hamiltonii. We hypothesize that the RCC became contaminated with these halophilic organisms from bicarbonate used to prepare dialysis fluid, and they persist despite cleaning and flushing procedures because of biofilm in machines and bicarbonate fluid inflow sites. Our experience, together with the review of the literature presented here, indicates the genus Halomonas has pathogenic potential.

Infection with antimicrobial-resistant microorganisms in dialysis patients

The prevalence of antimicrobial-resistant microorganisms in various health care settings, including outpatient dialysis facilities, has increased dramatically in the last decade. Antimicrobial use and patient-to-patient transmission of resistant strains are the two main factors that have contributed to this rapid increase. Methicillin-resistant Staphylococcus aureus (MRSA) and coagulase-negative staphylococci are commonly isolated as a cause of hemodialysis (HD) catheter-related bacteremia and peritoneal dialysis (PD)-related catheter infection and peritonitis. The widespread use of vancomycin in dialysis patients is of concern because of an increase in the prevalence of vancomycin-resistant enterococci (VRE) in dialysis patients. Staphylococci with reduced sensitivity to vancomycin have also appeared in dialysis patients. A more recent problem is the appearance of S. aureus isolates with a high degree of resistance to the topical antimicrobial agent mupirocin. This has been seen in PD patients who have received prophylactic application of mupirocin at the peritoneal catheter exit site. Appropriate antimicrobial use will help protect the efficacy of currently used antibiotics, such as vancomycin. Published guidelines for use of vancomycin should be followed. New antimicrobials such as linezolid and quinupristin/dalfopristin have activity against VRE and MRSA, but resistance to these agents has already occurred. Preventing transmission of antimicrobial-resistant microorganisms in health care settings, including outpatient dialysis facilities, is important in limiting the spread of these resistant organisms.

An outbreak of gram-negative bacteremia in hemodialysis patients traced to hemodialysis machine waste drain ports

OBJECTIVE

To investigate an outbreak of gram-negative bacteremias at a hemodialysis center (December 1, 1996-January 31, 1997).

DESIGN

Retrospective cohort study. Reviewed infection control practices and maintenance and disinfection procedures for the water system and dialysis machines. Performed cultures of the water and dialysis machines, including the waste-handling option (WHO), a drain port designed to dispose of saline used to flush the dialyzer before patient use. Compared isolates by pulsed-field gel electrophoresis.

SETTING

A hemodialysis center in Maryland.

RESULTS

94 patients received dialysis on 27 machines; 10 (11%) of the patients had gram-negative bacteremias. Pathogens causing these infections were Enterobacter cloacae (n = 6), Pseudomonas aeruginosa (n = 4), and Escherichia coli (n = 2); two patients had polymicrobial bacteremia. Factors associated with development of gram-negative bacteremias were receiving dialysis via a central venous catheter (CVC) rather than via an arterio-venous shunt (all 10 infected patients had CVCs compared to 31 of 84 uninfected patients, relative risk [RR] undefined; P<.001) or dialysis on any of three particular dialysis machines (7 of 10 infected patients were exposed to the three machines compared to 20 of 84 uninfected patients, RR = 5.8; P = .005). E cloacae, P aeruginosa, or both organisms were grown from cultures obtained from several dialysis machines. WHO valves, which prevent backflow from the drain to dialysis bloodlines, were faulty in 8 (31%) of 26 machines, including 2 of 3 machines epidemiologically linked to case-patients. Pulsed-field gel electrophoresis patterns of available dialysis machine and patient E cloacae isolates were identical.

CONCLUSIONS

Our study suggests that WHO ports with incompetent valves and resultant backflow were a source of cross-contamination of dialysis bloodlines and patients' CVCs. Replacement of faulty WHO valves and enhanced disinfection of dialysis machines terminated the outbreak.