What’s in your water? Waterborne bugs can cause fatal infections
Expect poison from standing water
June 1, 2015
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The water of life can sometimes mean death. Fatal infections can result if immune compromised patients are exposed to pathogenic bacteria that thrive in H2O, outbreak investigators recently reported at the Centers for Disease Control and Prevention’s annual EIS conference in Atlanta.
Epidemic Intelligence Service (EIS) officers are the CDC’s famous frontline medical detectives, an image they reinforce by having a shoe sole logo complete with a smashed wad of gum. They are typically the first on the scene of an outbreak, and in this case we feature three EIS officers who traced distinctly different clusters of infected patients to a common source: water.
The waterborne etiologic agents involved are well-known repeat offenders: Legionella pneumophila, Pseudomonas aeruginosa, Burkholderia cepacia and Stenotrophomonas maltophilia. These pathogens and other water bugs have minimal nutritional requirements and can tolerate a variety of physical conditions. “These attributes are critical to the success of these organisms as health care associated pathogens,” the CDC notes.1 “Waterborne pathogens spread in a variety of ways, including direct contact with water, aerosols, aspiration of water and inhalation of water aerosols, and indirect transfer from moist environmental surfaces via hands of healthcare workers.”
Measures to prevent the spread of waterborne bugs include hand hygiene, glove use, barrier precautions, and eliminating potentially contaminated environmental reservoirs, the CDC recommends. As a general rule, the CDC warns against using tap water for medical care (e.g., in direct patient care, for diluting solutions, as a water source for medical equipment and instruments, and for disinfection of instruments) due to the risk of exposing patients to waterborne pathogens.
The following EIS investigations underscore that an essential element of life we take for granted can become a reservoir for deadly water-borne pathogens in hospitals and other settings. Infection preventionists should be aware of the risks that water poses to patients, particularly those with compromised immune systems.
Three NICU deaths
In 2013 a neonatal intensive care unit (NICU) in California experienced a Pseudomonas aeruginosa outbreak that led to two deaths. Infection control interventions, water remediation, and intermittent use of point-of-use water filters were implemented in the unit. However, in September 2014, the CDC was notified of additional cases and another death, launching an investigation to identify risk factors and prevent further cases. In total, there were 31 cases and three deaths, with 15 cases and two deaths in 2013 and 16 cases and one death the following year, says Cara Kinsey, MD, CDC EIS officer and lead investigator.
Kinsey and co-investigators defined a case as the first positive Pseudomonas aeruginosa culture from an NICU patient during June 2013–September 2014. They reviewed medical records from the study period, and matched 1:1 by birth weight NICU case-patients to control-patients. In September 2014, they observed infection control procedures, obtained environmental cultures, and typed isolates by using pulsed-field gel electrophoresis (PFGE).2
The 31 case patients were more likely to have had a peripherally inserted central catheter, invasive ventilation or exposure to water without point-of-use filters less than one week before cultures were taken, EIS investigators found. Of 45 environmental samples, 31 (69%) produced Pseudomonas aeruginosa, with 94% of those water-related.
“The water-related samples included hospital tap water, faucet swabs, drain swabs, and sink basin swabs,” Kinsey says. “In November of 2013, the water used for infant baths was changed from tap water to sterile water. Prior to that, the infants were bathed in tap water. During our on-site investigation, we did not observe the tap water being used directly on the patients at any time. We speculate that the principal route of exposure was transfer of the bacteria from water, faucets, or sinks to the babies indirectly through contaminated hands.”
Isolates from the two most recent case-patients were indistinguishable by PFGE from water-related samples obtained from the case-patients’ rooms.
“The PFGE matches were between one patient isolate and a faucet swab and a swab of a shelf adjacent to the sink in the patient’s room,” she tells Hospital Infection Control & Prevention. “For another patient isolate, the PFGE pattern matched the sink surface in the patient’s room. It is important to keep in mind that we found many different PFGE patterns, indicating that the P. aeruginosa in the environment was genetically diverse, so the fact that we didn’t see more matches was not surprising.”
Again, the P. aeruginosa outbreak was attributed to contaminated water in the hospital system, with inadequate hand hygiene increasing the risk of transmission to neonates with invasive devices.
“During our hand hygiene observations in this NICU, we found that some staff were using hand washing [with water] as the primary means of hand hygiene,” Kinsey says. “One of our early recommendations to the hospital was to develop a comprehensive hand hygiene campaign emphasizing the preferential use of alcohol-based hand rub according to CDC guidelines.”
In addition to improving hand hygiene, the CDC recommended additional water-system remediation and continuous use of point-of-use water filters.
“We recommended the hospital continue to work with experts on water treatment remediation strategies to eliminate P. aeruginosa,” Kinsey says. “The hospital engaged with a consultant who installed point-of-use filters and a disinfection system. [We] provided guidance on monitoring to validate the efficacy of water remediation measures.”
Aersolization in showers
A hospital unit for immune-compromised cancer patients experienced an outbreak of legionellosis last year that was ultimately linked to the hospital’s water system. Although Legionnaires disease (LD) is a respiratory infection, infection prevention centers on the quality of water—the principal reservoir for Legionella species.
“Of the nine patients and one visitor [infected] we had two deaths,” says Louise Watkins, MD, the CDC EIS officer who led the investigation. “But I would caution that although we reported the deaths we did not attribute them to LD necessarily. These patients were very sick at baseline. Both patients who died refused autopsy so there was no official cause of death.”
Healthcare-associated LD has a mortality rate in the 14% to 40% range, with immunocompromised patients particularly susceptible. The visitor survived, but it was not definitively established how she become infected.
“She had risk factors for LD -- the primary one being she was 85 years old,” Watkins says. “There is a strong correlation between age and risk for LD. She also had COPD [chronic obstructive pulmonary disease], another risk factor for LD.”
The 10 cases include six definite and four probable healthcare-associated infections, all occurring over a 12-week period.
The Alabama Department of Public Health detected the outbreak in May of 2014, as LD is a reportable disease in all U.S. states. The fact that the hematology-oncology unit at the hospital had undergone recent construction may have contributed to the outbreak, as infections began to appear right after the unit opened, says Watkins.
“There was also stagnant water that sat in the distal piping for the two months before those fixtures were installed and the unit was opened,” she says.
During the investigation, an LD case was defined as radiographically-confirmed pneumonia in a person with a positive urinary antigen test and/or respiratory culture for legionella and exposure to the hematology-oncology unit. Cases were classified as definitely or probably healthcare-associated based on extent of exposure during the incubation period (2–10 days). Medical charts were reviewed and investigators conducted an environmental assessment and collected representative water samples for culture. Clinical and environmental isolates were compared by monoclonal antibody testing and sequence-based typing.
Environmental sampling revealed Legionella pneumophila serogroup 1 in the potable water at 50% (17/34) of hematology-oncology unit sites, including all patient rooms tested. Three clinical isolates were identical to environmental isolates from the unit. “We confirmed that there was legionella circulating through the hospitals hot water systems through environmental sampling. Furthermore the strain that was isolated from the water on the unit at nine different sites was identical to the strain in the clinical samples from the three case patients.”
The exact exposure sources could not be determined, but the individual showers in each patient’s room were the likely source of at least some of the infections. Many LD outbreaks have been traced back to showers and contaminated shower heads, which can create aerosols from which legionella can be inhaled.
“We could not interview individual patients about water exposures, but all patients had single rooms with sinks and showers with removable shower heads [attached with a hose]. We took around three dozen samples from 10 different sites, and in nine of those sites [including shower heads] legionella growth was found.”
No new cases occurred after implementation of water restrictions and point-of-use filters. Other remediation activities included superheating and flushing the water system and boosting chlorine levels with an injecting system.
“Water restrictions were made immediately,” Franklin says. “Based on the epidemic curve that we were seeing, we suspected from the beginning -- even before we had done any sampling that the potable water may have been a risk. So we recommended water restrictions to protect other patients. That included no patient contact with the water in the unit. We had the sinks blocked off, hand sanitizer brought to patients, bottled water for drinking, shaving, brushing of teeth – all hygiene measures.”
Blood and water
Approximately 24% of the more than 6,000 hemodialysis centers nationwide reuse dialyzers, reprocessing (cleaning and disinfecting) them between treatments. During August 2014, CDC became aware of gram-negative bloodstream infections (BSIs) among outpatients at multiple “Company A” hemodialysis facilities. An EIS team investigated to identify additional BSIs, assess risk factors, and recommend control measures.
An outbreak case was defined as a blood culture positive for Burkholderia cepacia or Stenotrophomonas maltophilia in a patient ≤1 week after hemodialysis at any Company A facility, during September 2013–September 2014.
In addition to dialysis equipment, B. cepacia and S. maltophlia have caused infections via distilled water, contaminated solutions and disinfectants, nebulizers, potable water and water baths, and ventilator temperature probes.1
To determine the cause of the BSIs in this case, the EIS team did a case control study and visited six facilities to observe practices and collect environmental samples, which were then compared with patient isolates with PFGE. They identified 16 patients at five facilities. Eight case-patients were hospitalized and none died.
More case-patients participated in dialyzer reuse compared with control subjects (94% versus 76%), but the difference was not statistically significant.
“We think this was because our study size was small, with only [16 patients],” says Jacklyn Wong, MD, CDC EIS officer and lead investigator. “[Also], most of the patients at these facilities were on reused [dialyzers], making it difficult to compare them against non-reuse patients. Despite these limitations, however, the overall evidence from our investigation suggests that dialyzer reuse does result in increased risk of infections.”
Compared with control subjects, case-patients more often had a high (>6) number of reuses. “When we examined the number of dialyzer reuses on a continuous scale, we found that each additional reuse increased the odds of infection by 7%, which indicates a cumulative effect,” she tells HIC.
Investigators observed sub-standardized cleaning of dialyzer headers and caps, opening opportunities for contamination during reprocessing. For example, technicians at some facilities used a high pressure water sprayer to clean off blood clots from the header cap, O-ring, and the exposed top of the dialyzer. Alternatively, technicians at some other facilities used disinfectant wipes on the header cap, O-ring, and the rim of the exposed dialyzer top, she says.
“Both of these practices were concerning to us because they could damage the dialyzer parts, particularly the delicate fiber bundle, and create surfaces amenable for bacterial growth.” Wong says. “As part of the company’s protocol, header caps and O-rings were supposed to be soaked in disinfectant solution before the dialyzer was reassembled. We noticed on some occasions that the parts were left floating on top of the solution rather than fully submerged, which could lead to incomplete disinfection.”
The EIS officers isolated B. cepacia and S. maltophilia from reprocessing equipment or purified water at 3 facilities. Within one facility, a B.cepacia environmental isolate was indistinguishable from a patient isolate. The company voluntarily stopped reuse in one facility.
“Bacteria, which came from the water supply, contaminated both the equipment and the dialyzers, but we can’t necessarily say that it was transferred from the equipment to the dialyzers,” Wong says. “Water serves as the reservoir for the bacteria and when reprocessed, the dialyzers create an opportunity for those bacteria to be spread to the patient.”
BSIs were associated with frequent dialyzer reuse, so less frequent reuse or nonreuse might improve patient safety, the EIS concluded. In any case, facilities practicing reuse should standardize reprocessing procedures to avoid contamination.
“We observed a lot of variation in dialyzer reprocessing practices during our facility visits,” she says. “For example, we observed that some facilities were still reprocessing dialyzers entirely by hand, whereas other facilities relied on automated machines for most of the steps.”
Based on the CDC findings, the company in question instituted several changes in their reprocessing practices, she adds.
“They eliminated some of the equipment that was found to be contaminated,” Wong tells HIC. “In addition, they have discontinued use of high pressure sprayers and wipes on dialyzer parts, and have started using procedures to ensure that parts are fully submerged in disinfectant. To increase the margin of safety for all patients, the company has decided to phase out dialyzer reuse in all of their clinics by the end of 2015.”
References
- Centers for Disease Control and Prevention Healthcare Infection Control Practices Advisory Committee (HICPAC) Guidelines for Environmental Infection Control in Health-Care Facilities 2003. Available at http://www.cdc.gov/hicpac/pubs.html
- Kinsey C, Koirala S, Solomon, B, et al. Pseudomonas aeruginosa in a Neonatal Intensive Care Unit — California, 2013–2014. 64th Annual EIS Conference. Atlanta: April 20–23, 2015.
- Watkins FL, Harris AM, Toews, K, et al. Healthcare-Associated Outbreak of Legionnaires’ Disease on an Inpatient Hematology-Oncology Unit — Alabama, 2014. CDC 64th Annual EIS Conference. Atlanta: April 20 – 23, 2015.
- Wong J, Edens W, Lyman M, et al. Gram-Negative Bloodstream Infections Among Hemodialysis Outpatients — California, 2013–2014. CDC 64th Annual EIS Conference. Atlanta: April 20 – 23, 2015
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