Legionellosis (Legionnaires’ Disease) Task Force Recommendations
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Purpose of the Texas Legionellosis Task Force
In November 1996 a major hospital in San Antonio, TX, notified the Texas Department of State Health Services (DSHS) in Austin about an apparent increase in the number of nosocomial Legionellosis cases in that facility. Staff from the Infectious Disease Epidemiology and Surveillance Branch were asked to assist the hospital in evaluating this potential cluster. During the evaluation of hospital records and practices, other recent nosocomial Legionellosis patients were identified in several other San Antonio area hospitals. The discovery of these cases led to a joint investigation involving the San Antonio Metropolitan Health District, the Texas Department of State Health Services, and the Centers for Disease Control and Prevention in Atlanta, Georgia (CDC). In that investigation it became apparent that the risk of nosocomial Legionellosis in Texas is highly variable and that the method of water treatment in a given community may influence the risk of Legionella bacterial contamination in the hospital setting. A description of the investigation was published .
In December 1999 Reyn Archer, MD, then Commissioner of the Texas Department of State Health Services, asked Dennis Perrotta, PhD, the State Epidemiologist, and IDCU staff to convene a task force of Texas physicians, nurses, and public health professionals to develop a Legionellosis control plan for the state of Texas. Task force members are identified in Appendix A. The recommendations contained in this plan are intended to help local health officials respond to reports of legionellosis in hospitals, long-term care facilities (LTCFs), and the community. They are also intended to guide hospitals and LTCFs in the establishment of their Legionellosis control plan.
In June 2000 the State of Maryland Department of Health and Mental Hygiene published a comprehensive report of their Scientific Working Group to Study Legionella in Water Systems in Healthcare Institutions . The Maryland plan was the most comprehensive document published by any state health department on Legionnaires’ disease control issues to date, and recognizing the value of that document and the work it represents, DSHS staff asked for and received permission from the Maryland Department of Health and Mental Hygiene to incorporate elements of their document into the Texas plan. While the DSHS acknowledges the substantial amount of information in the Maryland plan that is included herein, the Texas plan differs significantly from the Maryland document in specific recommendations.
Overview of Legionellosis
Legionella bacteria were first recognized in association with an outbreak of pneumonia in 1976 that occurred among attendees of an American Legion convention in Philadelphia . Since then, more than 39 species and 61 serogroups of Legionella bacteria have been identified . While more than half of these species/serogroups have been associated with human disease [5,6], L. pneumophila, the first Legionella species identified, accounts for approximately 90% of infections, with illness most frequently associated with serogroups 1, 4, and 6 .
Legionella can cause Pontiac Fever, an often undiagnosed and generally mild and self-limiting "flu-like" illness . They also cause Legionellosis, a potentially severe bacterial pneumonia that is accompanied by cough, fever, and fatigue . Legionellosis is used to describe both diseases. The incubation period for Legionellosis is usually 2-10 days. Based on studies in several parts of the country, Legionellosis may account for 5-15% of all community-acquired pneumonias . Without appropriate antibiotic therapy, infection can cause serious
complications and even death. Patients with Legionellosis have signs and symptoms that resemble other bacterial pneumonias, and the diagnosis generally cannot be made by a physician in the absence of specialized laboratory testing .
Certain populations are clearly at greater risk than others for developing severe Legionella infections [12-15]. The most important host risk factors for developing illness include 1) immunosuppressive therapy (anti-rejection therapy to prevent graft rejection in bone marrow and solid organ transplant patients), 2) chemotherapy for neoplastic disease, current steroid therapy (>20 mg/day for more than 14 days;), and 3) chronic underlying illnesses such as hematologic malignancies or end-stage renal disease. There is a moderately increased risk of illness among the elderly (age > 65 years), smokers, and people with chronic lung disease, diabetes, or congestive heart failure. The disease is extremely rare in children.
Legionellosis is characterized by fever, myalgias, cough, and pneumonia. It cannot be distinguished clinically or radiographically from pneumonia caused by other agents, and evidence of infection with other respiratory pathogens does not rule out the possibility of concomitant Legionella infection.
Laboratory tests used to diagnose Legionella infection are summarized in Table 1. The definitive method for diagnosis is culture of the organism. Culture requires use of a specialized panel of differential and selective media. Respiratory specimens are plated onto these media (buffered charcoal yeast extract agar [BCYE], BCYE/PVA [contains polymixin B, vancomycin, and anisomycin], and BCYE/PAC [contains polymixin B, anisomycin, and cefamandole]) and incubated at 35-37oC (95-98.6oF) for up to 14 days . The ideal specimens for culture are bronchial washings, bronchial lavages, or bronchial brushings. If a sputum is the only specimen that can be obtained, results are improved if the sample is pretreated with 0.2 M KCl/HCl solution (pH=2.2) for 4 minutes to decrease numbers of endogenous bacteria that can grow on the BCYE agar . In experienced hands, culture results can usually be obtained in 3 to 5 days.
The advent of urine antigen testing in the mid 1990s provided for the first time a simple, rapid means of identifying infected patients. There are currently two FDA-approved rapid antigen detection assays designed to detect Legionella-specific antigens in urine specimens [18-20]. The first is an enzyme-linked immunoassay (EIA) that requires special laboratory instrumentation and takes approximately three hours to perform. The second, which has just recently been introduced, is a rapid antigen card test (a paper chromatography based assay) that requires less than 30 minutes to perform and no instrumentation. Both tests have comparable sensitivity and specificity, but are only capable of detecting L. pneumophila serogroup 1, which accounts for 70-80% of disease.
Direct fluorescent antibody (DFA) staining is another rapid diagnostic test for Legionella species. This technique is much less sensitive than either culture or the urine antigen tests because large numbers of organisms must be present. Colonies grown in culture or respiratory secretions can be used for DFA. Genus-specific antibodies are used to confirm the isolation of Legionella.
Antibody testing of serum, while available, also has significant drawbacks. Chief among these is the need for two serum samples, one drawn shortly after illness onset and a second 3 to 6 weeks later. Diagnosis is confirmed by a fourfold increase in the antibody titer to 1:128 or more. Positive results are not useful for case management. From a practical standpoint, it is also difficult to arrange for collection of a second blood sample from a patient weeks after he or she has recovered from an illness and been discharged from an acute care facility.
Requires specially trained laboratory technicians
Urinary antigen test
Only detects L. pneumophila serogroup 1
Direct fluorescent antibody
Sensitivity is low, requires specially trained laboratory technicians
Antibody Testing (serology)
Sensitivity is low, requires collection of second blood sample 3-6 weeks after acute specimen collected
The CDC estimates that between 8,000 and 18,000 cases of Legionellosis occur each year in the United States; from 1995 through 2000, 400 to 600 of these were reported to public health authorities. Nosocomial cases have a higher mortality rate than community-acquired cases (40% compared to 20%). Nosocomial outbreaks often continue for years before being recognized [18,21]. In a national survey of 192 randomly selected hospitals, 29% reported having at least a single case of nosocomial Legionellosis and 16% reported greater than five cases. Of these surveyed hospitals, 60% had on-site testing capabilities, but only 21% had established routine Legionella testing .
Legionellosis became a reportable condition in Texas in July 1984: Both physicians and laboratories are required by law to report confirmed cases of legionellosis to their local health departments. The following CDC case definition is used for reporting purposes :
From 1990-1999 inclusive, there were 227 laboratory-confirmed cases of legionellosis reported to the Texas Department of State Health Services, for an average of 23 cases per year (range 13-32). The most significant obstacle to confirming suspected legionellosis is the difficulty of obtaining convalescent sera. From 1990-1999, the health department received approximately four times as many single-titer results as confirmed results (yearly average of 83 compared to 23). Clearly, physicians suspect legionellosis far more often than they confirm it. A single Legionella antibody titer result is not sufficient to confirm a suspected case of legionellosis.
The Texas Department of State Health Services has investigated three legionellosis outbreaks since 1989, involving from 3 to 20 patients each. However, state and local health departments have been asked to address numerous “pseudo-outbreaks” each year around suspected or feared but unconfirmed cases. Most of these were based on a single elevated Legionella antibody titer.
Legionella is widely distributed in aquatic environments. The bacteria thrive in indoor water systems, even in the presence of usual free (unbound) chlorine residual levels; this is particularly true if water is in a temperature range of 25-42oC (77-108oF), sediment and scaling are present, and the water is relatively stagnant. Growth may be facilitated by the presence of other microorganisms capable of supporting intracellular growth of the organism. Legionella organisms die rapidly at temperatures above 50oC (122oF). A one log reduction (eg, from 1000 to 100) in the number of Legionella organisms is accomplished in 1.4-10.6 minutes at 60oC (140oF), in 1.1-2.6 minutes at 70oC (158oF), and in 0.4-0.7 minutes at 80oC (176oF) . In hospitals and other institutions, Legionella are found primarily in two locations, 1) potable hot water systems (defined as all building plumbing systems that distribute water for direct human contact), and 2) water in cooling towers. In hot water systems, concentrations of the bacterium are highest in biofilms within the system and at openings of water outlets. While data are limited, ingestion/aspiration and aerosolization of potable water from hot water systems are thought to represent the major routes by which the organism is transmitted to patients in nosocomial Legionella cases [26-29]. Exposure to aerosols from cooling towers containing the organism has most often been associated with community outbreaks [30-33], although this route should also be considered for nosocomial cases.
Many, but not all, hospital hot water systems are colonized with Legionella (Table 2). It is hypothesized that the organism is introduced into institutional water distribution systems from public/municipal water systems. Municipal water systems do not routinely screen water for the presence of Legionella. As Legionella is moderately chlorine tolerant, it will survive many standard municipal water treatment protocols. Once present in a hospital hot water system, Legionella organisms are able to survive and multiply, particularly at hot water temperatures kept relatively low to minimize the scald risk for patients . Factors which determine whether a specific hospital water system will be colonized with Legionella are not well understood, but probably include the type of disinfection used, age and condition of the pipes, the degree of scaling and sediment, and the potential for biofilm formation within the system. Methods for obtaining cultures from water systems are not well standardized, and it is clear that results vary widely depending on the methodology used.
Temporary elimination or reduction of Legionella colonization in a hot water "ecosystem" is possible, although difficult. Success depends on the design and condition of the system, as well as the remediation methodology used. If a system is old, cleaning and descaling may be an important component of a Legionella control program. As Legionella is killed by temperatures over 50oC (122oF), superheating of water (raising of water temperature above the normal set point for the system) may be efficacious . CDC recommendations call for flushing of the hot water system for a minimum of 30 minutes with the hot water superheated above 60oC (140oF) . While superheating may result in a reduction in system colonization, Legionella is usually not eradicated, and often recolonizes the system within a matter of weeks, necessitating recurrent superheating cycles. As an alternative to superheating, CDC recommends "shock" hyperchlorination (flushing all outlets for at least 5 minutes with greater than 10 mg/liter of chlorine in water)[43,44]. Again, this method may only suppress Legionella, permitting subsequent recolonization. Continuous hyperchlorination has been attempted by several institutions, but has generally been discontinued because of its corrosive effect on plumbing . For example, three years after implementation of hyperchlorination at a University of Iowa hospital, the incidence of pipe leaks was 30 times the rate before chlorination.
Success with long-term disinfection has been obtained with continuous copper-silver ionization techniques, though there are reports of such a system losing efficacy over time [46-52]. UV light systems may be useful for localized disinfection, but there are no distal, residual effects [53,54]. A new hospital at the University of Virginia built in 1989 had a UV light disinfection system installed on the municipal water intake upon completion. Despite having had substantial problems with Legionella in its old hospital building, the potable hot water in this new building has remained consistently culture-negative for Legionella (with no nosocomial Legionella cases), suggesting that it is possible to prevent initial colonization of newly constructed hot water systems . There are also now intriguing data suggesting that use of monochloramine as a disinfectant in municipal and hospital systems (rather than the more traditional free chlorine) is effective in eradicating Legionella [56,57]. In a recent study in Texas , all 11 hospitals on municipal water systems using free chlorine for disinfection had Legionella in their water systems; in contrast, the 4 hospitals on municipal water systems using monochloramine for disinfection had water systems that were culture-negative for Legionella (and had no cases of nosocomial Legionella infection).
A Maryland hospital recently reported installation of a monochloramine system in an administration building of a hospital that had ongoing problems with Legionella in patient care areas; placement of the system resulted in a significant decrease in the Legionella counts in the building’s potable hot water system . Further details regarding methods for minimizing the risk of Legionella in building water systems (including cooling towers and other water sources) can be obtained from the recent guidelines published by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE).
While it is well recognized that Legionella can colonize a hospital hot water system, the link between specific levels of colonization and risk of nosocomial Legionella infection remains uncertain. In a longitudinal study at the Pittsburgh Veterans Affairs hospital published in 1983, cases of nosocomial Legionella infection were most likely to occur when more than 30% of 10 selected distal sites in the hospital water system were culture-positive for Legionella . Based on these findings, the Allegheny County, Pennsylvania, health department established guidelines (, www.legionella.org/ACHD_guideline.htm) under which hospitals are advised to routinely culture their water systems for Legionella, and initiate control efforts for Legionella in the water system when >30% of distal sites are culture-positive for the organism. Since these guidelines were put in place in 1992, the percent of total reported Legionella infections in Allegheny County, PA, that are hospital-acquired has dropped from 50% (23 of 46 cases) to 13% (4 of 30 cases). This 30% of distal sites "action level," while demonstrating utility in controlling nosocomial Legionella infections in the Pittsburgh area, has not been tested in studies in other geographic areas. In the recent Texas study, there was a suggestion that risk of nosocomial illness correlated with the proportion of samples from which Legionella was recovered at each institution .
Further, there do not appear to be sufficient data to substantiate use of quantitative Legionella counts (i.e., actual counting of Legionella bacterial colonies on a plate, rather than simply reporting a culture as positive or negative) to predict risk of illness. It is also clear that quantitative values can vary dramatically depending on sampling and culture techniques.
Existing Guidelines for Prevention
In 1994 the CDC proposed guidelines to prevent and control nosocomial pneumonia (including Legionellosis); these guidelines were updated in 1997 [14;www.cdc.gov/ncidod/diseases/hip/pneumonia/2_legion.htm]. The guidelines advocate active surveillance and good casefinding strategies in hospitals, including establishment of appropriate diagnostic capabilities for Legionella. CDC guidelines/recommendations do not advocate routine culturing of water systems for Legionella, noting the overall high rate of colonization of hospital water systems with the bacterium, and citing the lack of data to substantiate any one "action level" for positive cultures. CDC investigators have also expressed concern that negative culture results will give physicians a "false sense of security" that Legionella cases will not occur in their facility. Instead, CDC recommends that environmental sampling be conducted when nosocomial Legionella cases are identified in hospitals with high risk patients (see Hospital Infection Control Practices Advisory Committee [HICPAC] recommendations ). Decontamination is recommended if infections are traced to a specific source (such as the water system), with the effectiveness of decontamination monitored by sampling every 2 weeks for 3 months and, if negative, sampling monthly for another 3 months. As CDC investigators do not feel that a "safe" level of Legionella in a water system can be determined, monitoring and decontamination efforts should be continued until cultures are negative. CDC guidelines also note the need for routinely maintaining cooling towers (also see ASHRAE guidelines ); and using only sterile water for the filling and terminal rinsing of nebulization devices. More recently CDC has published draft guidelines, Prevention of Opportunistic Infections Among Bone Marrow Transplant Recipients, that recommend periodic routine culturing for Legionella from a unit’s potable water supply as part of an overall strategy to prevent Legionnaires’ disease in transplant patients. These guidelines further recommend that the goal of environmental surveillance for Legionella in transplant units should be to maintain water systems with NO detectable organisms.
The guidelines developed for control of Legionellosis by the State of Maryland resemble those of the CDC in that they recommend hospital personnel conduct active surveillance and casefinding, have ready access to appropriate tests for diagnosis, and investigate all nosocomial cases [2;www.dhmh.state.md.us/html/legionella.htm]. The Maryland guidelines differ from those of CDC, however, in that they recommend routine culturing of water distribution systems within hospitals. The frequency of culturing is to be determined by an assessment of risk factors for Legionnaires’ disease, including water system design and condition, patient population susceptibility, and past history of Legionella in patients or the water system. In the Maryland guidelines, remediation is triggered by the identification of a nosocomial case of Legionnaires’ disease; however, the goal of complete elimination of Legionella is generally not recommended.
Like the State of Maryland recommendations and in contrast to the approach taken by CDC for all hospitals, Allegheny County, PA, has implemented a control strategy for nosocomial Legionella infection that incorporates regular environmental sampling (, www.legionella.org/ACHD_guideline.htm). The Allegheny County document recommends that all hospitals perform yearly environmental surveys that include water sample cultures. The specific recommendations are as follows:
The Allegheny County, PA, guidelines also emphasize the need for good surveillance for nosocomial legionellosis, and the associated need for optimal diagnostic capabilities for Legionella in hospitals. Regardless of environmental findings, remediation efforts are triggered by identification of a nosocomial case. These guidelines recognize that total elimination of Legionella from a water system may not be possible, or necessary; the goal is to reduce Legionella levels to a point (<30% of distal sites positive) where risk of nosocomial Legionella infection is felt to be minimized.
In hospitals in which nosocomial cases are identified, there may be some benefit to limiting exposure of immunocompromised patients to potential sources of infection, pending reduction or elimination of Legionella colonization of the water system. It has been suggested that this be accomplished by prohibiting patient showers and using only sterile water for oral consumption .
Texas Recommendations for Acute Care Hospitals
In preparing recommendations, the Texas Legionellosis Task Force carefully considered the work of the Maryland Scientific Working Group, the published guidelines of the CDC, and the opinions of other prominent researchers in the field. The recommendations presented below reflect the expert opinion of the Texas Task Force, drawing on available published data and the expertise and experience of Task Force members. Many of the recommendations are intended for physicians and hospitals, because the people at greatest risk of acquiring legionellosis are immunocompromised and/or chronically and seriously ill patients who are hospitalized or are outpatients under the care of a physician. The Task Force also made recommendations for nursing homes and other LTCFs that serve as permanent residences for medically fragile individuals. Finally, the Task Force developed some guidelines to assist health departments and physicians address sporadic, community-acquired cases.
The Task Force recognizes that no single template can serve the needs of all types of facilities, and strongly supports an approach that allows institutions to individualize their legionellosis control plans based on the history of their institution; the matrix of environmental factors, engineering issues, and patient populations served by the institution; and the resources the institution has available to address these concerns. The Task Force does intend for each institution to consider the factors that may contribute to legionellosis transmission and diagnosis in their context and to develop a control plan or plan of action that increases physician awareness of the disease, increases the diagnostic capability of that institution, and enhances the institution’s ability to prevent disease.
Each hospital should form a team of representatives from various departments such as infection control, engineering and maintenance, risk management, employee health, administration, and housekeeping to prevent and control legionellosis. The team should develop and write a legionellosis control plan. The team shall be led by a hospital epidemiologist or an infection control professional. This operational plan should encompass several components including: 1) surveillance strategies, 2) whether environmental culturing is recommended, 3) remediation strategies (if and when necessary), and 4) reporting procedures.
I. Differential: Clinicians should consider Legionella species in their differential diagnosis for both nosocomial and community-acquired pneumonia. Appropriate diagnostic specimens should be obtained before initiating treatment.
II. Urine Antigen: All acute-care hospitals should either provide Legionella urinary antigen testing in-house, or contract with another laboratory that can report test results within 48 hours.
III.Cultures: All hospitals that routinely perform and care for patients with solid organ and/or bone marrow transplants should have the ability to perform Legionella culture on site. All others should have a mechanism in place that allows them to submit primary specimens for Legionella cultures to a microbiology laboratory within 24 hours of specimen collection.
IV. DSHS as Reference: The DSHS laboratory serves as a secondary reference laboratory for Legionella, with the capability to serotype, speciate, and characterize isolates on a molecular basis. Specimens from possible and definite nosocomial cases should be forwarded to the DSHS.
I. Passive Case Detection
II. Active Case Detection
When a hospital has a possible or definite nosocomial case, active surveillance must be implemented.
Environmental testing, in the context of legionellosis, is the sampling of water and plumbing structures of a facility's water distribution system. The Texas Task Force discussed the role of environmental testing as a surveillance measure and investigational tool at great length. There are currently two different views in the United States on the role of environmental testing. One group holds that environmental testing should only proceed once an outbreak or definite transmission has been identified. Another group proposes that all hospitals routinely culture for environmental Legionella. Adoption of the first position, as done by the CDC, could place certain patient populations at increased risk for acquiring Legionellosis; the potential risk to such patients can only be ascertained by environmental testing. Recent research in Texas has shown that there are wide disparities between facilities’ water systems in Legionella colonization . Adoption of the second position, as done by the Allegheny County Health Department and the State of Maryland, commits large numbers of facilities to regular investments of resources that may be disproportionate to the risk involved and in fact may damage the infection control capacity of a given facility by diverting staff time and resources away from other, potentially more pressing, infection control concerns. Drawing on elements from both the CDC position and the position outlined in the report produced by the Scientific Working Group in the State of Maryland, the Texas Legionellosis Task Force developed the following recommendations for healthcare facilities.
I. Assessment of Legionellosis Risk and Criteria for Environmental (Water Distribution System) Testing
All healthcare facilities should, in implementing their legionellosis control plan, assess their risk of legionellosis transmission. Each facility should evaluate environmental, engineering, and patient population factors to determine whether there is a reasonable potential for nosocomial transmission. Baseline water distribution system cultures should be performed if the results of the assessment indicate the facility has a significant risk of legionellosis transmission.
Factors that affectthe risk of nosocomial transmissionin a given facility are as follows:
A. Environmental factors
B. Engineering factors: The following water system characteristics have been associated with the growth of Legionella:
C. Patient mix: The following patient populations are all at increased risk for legionellosis, and any facility that treats these patients is at increased risk for disease to occur. Immunocompromised employees may also be at increased risk.
D. Prior history: A prior history of either of the following may increase the risk of transmission:
The Task Force recommends that each facility consider these factors in determining whether there is an increased risk of nosocomial transmission. An example of how such a determination may be made is as follows: any facility located in a community where free chlorine is used as a residual disinfectant, that is a multistory facility with multiple water distribution systems, where hot water is stored at 51oC (124°F) and delivered to patient care areas at no greater than 43oC (110°F), with patients receiving bone marrow or solid organ transplants or cancer patients undergoing chemotherapy present, would be considered a facility that is at increased risk for nosocomial transmission. Such a facility should conduct a baseline environmental assessment, including Legionella tests of water samples from water distribution endpoints, and maintain these data on file in the infection control program office and the facility engineer’s office. If, however, the facility is a one story rehabilitation hospital with a limited number of beds and a simple plumbing design, with no dead legs in the system, in a community where monochloramine is used as a residual chemical disinfectant, and no immunosuppressed patients are present, the factors increasing the facility’s risk for transmission would not be present and there would be no recommendation for an environmental assessment at this time.
II. Procedures for Environmental (Water Distribution System) Testing
A. Water distribution system culturing should only be done after one of the following criteria are met:
B. Water distribution system testing should be conducted according to a standard protocol.
C. Legionella cultures should be qualitative and not quantitative.
D. Serotyping and species identification should be included in the results; hospitals unable to speciate or serotype should send samples to a reference laboratory.
E. When cultures of the water distribution system yield Legionella, the hospital's physicians should be informed to heighten awareness of Legionella as a potential cause of nosocomial pneumonia.
In keeping with the spirit of the State of Maryland Report of the Scientific Working Group and the Allegheny County, PA, recommendations, the intent of the Texas Task Force is not to insist that hospitals must have culture-negative water systems; it is recognized that persistence of Legionella in many instances will be inevitable, and may be of minimal significance from a public health standpoint. All hospitals are expected to maintain good surveillance for nosocomial Legionella cases; identification of a nosocomial case should be a clear indication that further efforts must be made to reduce Legionella colonization of the water supply. Hospitals that do not have the infection control expertise to interpret data should work with the local health department, and may need to retain the services of an expert in this field. However, except in special circumstances (such as an outbreak), water distribution system culture results should not be routinely reported to the health department.
Prevention strategies for Legionella pneumonia should be developed and implemented by all acute-care hospitals in Texas as part of each facility’s legionellosis control plan.
I. Primary Prevention
II. Secondary Prevention: Prevention of Legionellosis in Hospitals with Identified Cases
Identification of one definite or two possible nosocomial Legionella cases within a 6 month period should initiate the preventive measures described in IB above (Prevention of legionellosis in hospitals with no identified cases but with positive baseline water distribution system testing [>30% distal sites culture positive for Legionella]).
Table: Comparison of Legionnaires' Disease Control Plans - See Appendix D
Texas Recommendations for Long-Term Care Facilities
Nursing homes, other LTCFs, and other medical assisted living facilities pose a unique set of challenges from both the infection control and public health perspectives. Such facilities are not acute care hospitals, and the residents of these facilities are in some ways more similar to community residents than to patients requiring acute care in the hospital setting. At the same time, residents of LTCFs are typically medically fragile, though stable, individuals who may have chronic health conditions that do increase their risk for acquiring Legionnaires' disease if exposed. As such, residents of LTCFs represent a population whose public health needs merit consideration.
For nosocomial legionellosis, the following CDC case definitions are used :
Confirmed nosocomial case: laboratory-confirmed legionellosis that occurs in a patient who has been hospitalized [or otherwise institutionalized] continuously for > 10 days before the onset of illness.
Possible nosocomial case: laboratory-confirmed legionellosis that occurs in a patient 2-9 days after hospital [or other institutional] admission.
[Note: The incubation for Pontiac fever is shorter than for Legionnaires' disease; it is 1-3 days.]
For the purposes of this document, nosocomial infections shall include those acquired in hospitals, LTCFs, or other medical assisted living facilities.
Each LTCF should have a legionellosis control plan. This operational plan should address surveillance and reporting strategies, and when environmental (water distribution system) testing and remediation are necessary. Facility staff should be aware of the water treatment procedures used in the community. Water sources that do not use any residual chemical disinfection or use free chlorine as a residual disinfectant may be at increased risk when compared with water sources that use monochloramine as the chemical residual disinfectant [1,57,58].
I. Differential: Clinicians should consider Legionella species in their differential diagnosis for nosocomial pneumonia.
II. Urine Antigen: All LTCFs should provide Legionella urinary antigen testing either in-house, or contract with another laboratory that can report test results within 48 hours.
III.Cultures: All LTCFs should have a mechanism in place that allows them to submit primary specimens for Legionella cultures to a microbiology laboratory within 48 hours of specimen collection.
IV. DSHS as Reference Laboratory: The DSHS laboratory serves as a secondary reference laboratory for Legionella, with the capability to serotype, speciate, and characterize isolates on a molecular basis. Specimens from possible and definite nosocomial cases should be forwarded to the DSHS.
I. Passive Case Detection
If a resident of the LTCF is diagnosed with legionellosis, either while residing in the facility or within 9 days of transfer to an acute care hospital for pneumonia, the case should be investigated in a manner similar to the way cases are investigated in the hospital setting. Any resident confirmed to have Legionella pneumonia who has resided in the LTCF for > 10 days prior to their onset of pneumonia should be considered a nosocomial case for that LTCF. Any resident in a LTCF who develops confirmed Legionella pneumonia from 2 through 9 days after admission should be considered potentially nosocomial to that LTCF. Any patient transferred to the LTCF who develops confirmed Legionella pneumonia from 2 through 9 days after admission should be considered potentially nosocomial to both the receiving and transferring facilities. The transferring facility should be notified of such cases.
Confirmed cases of legionellosis should be reported to the local health department (800-705-8868) as “definitely nosocomial,” or "possibly nosocomial,” or “not nosocomial” cases within one week of confirmed diagnosis. The report should be submitted on DSHS IDCU Form 5, 02/02; [Form ( PDF File: 31.9KB)] to the local health department. The local health department should also report to DSHS within one week of confirmed diagnosis. For confirmed cases, the local health department should conduct a site assessment to identify potentially high risk environmental factors.
Outbreaks (defined as two or more institutionally linked cases or possible cases within the same 6-month period) must be reported immediately to the local health department at 1-800-705-8868.
II. Active Case Detection
Once a possible nosocomial case is identified in a LTCF, increased surveillance should be implemented. At a minimum, this should include increased surveillance for pneumonia cases and the collection of clinical specimens (i.e. urine for antigen testing) to determine the etiology of all cases of pneumonia in any resident. Enhanced surveillance should continue for at least 6 months.
Environmental testing, in the context of legionellosis, is the sampling of water and plumbing structures of a facility's water distribution system. The Texas Task Force does not recommend baseline environmental testing for LTCFs.
Environmental testing should be conducted whenever there are one or more definite nosocomial cases or two or more possible nosocomial cases. Patients who are confirmed as cases are definitely nosocomial if they have not left the facility within the previous 10 days.
Procedures for Environmental (Water Distribution System) Testing
I. Environmental Testing Should Be Conducted According to a Standard Protocol.
II. Legionella Cultures Should Be Qualitative and Not Quantitative.
III.Serotyping and Species Identification Should Be Included in the Results; Hospitals Unable to Speciate Should Send Samples to a Reference Laboratory.
IV. The Results of Any Environmental Cultures Obtained Should Be Provided to Hospital Physicians in Order to Heighten Awareness of the Possibility of Legionella as a Cause for Nosocomial Pneumonia.
Prevention strategies for Legionella pneumonia should be developed and implemented by all LTCFs in Texas as part of their legionellosis control plan.
I. Primary Prevention: Prevention of Legionellosis in LTCFs with No Identified Cases
II. Secondary Prevention: Prevention of Legionellosis in LTCFs with Identified Cases
The following preventive measures should be initiated immediately whenever one definite or two possible nosocomial Legionella cases occurring within a 6 month period are identified:
Texas Recommendations for Sporadic Community-Acquired Cases
Only 15-20% of legionellosis cases reported to the CDC have occurred in outbreaks . Most (80-85%) cases of Legionnaires' disease occur as sporadic, community-acquired pneumonias. Sporadic legionellosis is extremely difficult to study and determining the correct public health response to a single case is difficult. People are exposed to hundreds of potential water aerosols each week, and studies have suggested that, at least in a hospital situation, aspiration of potable drinking water may be an important route of transmission . Most patients with Legionella infection have multiple potential exposures (workplace, hotel, or other public space) during their 10-day incubation period; it is almost always impossible to conduct a meaningful investigation around a single sporadic case.
A cluster of legionellosis cases with a common exposure can involve both Legionnaires' disease and Pontiac fever . The Task Force therefore recommends that investigating health departments be alert to this possibility. Questions regarding ill contacts of Legionnaires' diseases case patients should not be limited to persons with symptoms of pneumonia.
The Task Force recommends the following guidelines to assist health department staff in responding appropriately to such events and to educate physicians on the importance of correctly confirming the diagnosis before informing a patient that they have Legionellosis. The health department should disseminate information regarding Legionellosis to physicians [eg, 66].
When a sporadic case of Legionellosis is diagnosed, the first priority is to confirm the diagnosis. First, ensure that the patient has a compatible clinical syndrome. A patient must have x-ray confirmed pneumonia. Second, the case must be laboratory-confirmed. A positive culture or positive urine antigen test is necessary for a confirmed diagnosis of the disease. Single total antibody titers are not diagnostic and should never be used to confirm Legionellosis.
I. Passive Case Detection and Follow-up
Cases of confirmed Legionellosis reported by physicians or laboratories should be investigated by the local health department. (Confirmed cases should be reported to the local health department; 800-705-8868.) The patient or patient’s contacts should be interviewed to ascertain all potential exposures to water or water aerosols at home, at work, and to obtain a travel history for the patient during the 10 days prior to onset with pneumonia symptoms. DSHS IDCU Form 5, 02/02; [Form ( PDF File: 31.9KB)], including the exposure information, should be sent to the Public Health Region office and the Texas Department of State Health Services promptly.
Family members, coworkers, and other contacts of the patient should be educated about Legionellosis. Particularly emphasize that healthy children and adults have a low risk of acquiring the disease and the disease is not transmitted person-to-person. Remind contacts of the disease symptoms (nonproductive cough, high fever, anorexia, malaise, headache, myalgias, abdominal pain and diarrhea). Remind contacts that people who are immunosuppressed, organ transplant or bone marrow transplant recipients, cancer patients undergoing chemotherapy, or patients with chronic obstructive pulmonary disease are at increased risk. Anyone experiencing symptoms should be evaluated by a physician. A fact sheet, entitled “Legionellosis: Legionnaires’ disease and Pontiac fever,” is attached as Appendix E. Local clinicians should be reminded to report patients who fit the case definitions.
II. Active Surveillance and Epidemiologic Investigation
If the local health department determines that two or more confirmed cases share a common reported exposure during any 6 month period, an epidemiologic investigation should be initiated. The investigation should include:
Environmental testing, in the context of legionellosis, is the sampling of water and plumbing structures of a facility's water distribution system.
I. Single Cases:
The findings of the local health department investigation should determine whether or not any environmental testing is indicated. Most individuals have too many potential exposures during a typical incubation period to make such testing meaningful. (If the patient was diagnosed using the urine antigen test and no culture is available to speciate and serotype, environmental assessments have extremely limited value.) However, in some instances the investigation may uncover residential or occupational exposures known to be associated with Legionellosis cases. Environmental testing may be indicated in such cases.
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Membership of the Texas Legionnaires’ Disease Task Force
(listed in alphabetical order)
Anthony E. Bennett, RS
David Bergmire-Sweat, MPH
Nancy B. Bjerke, RN, MPH, CIC
Homer C. Emery, PhD
Linda K. Gaul, PhD, MPH
Kate Hendricks, MD, MPH&TM
Jessica Hilburn, BSMT (ASCP), CIC
Gary Holmes, MD
Bobby Jones, DVM
Robert Kimbrough, MD
C. Glen Mayhall, MD
Ellen Musgrave, RN, CIC
Neil Pascoe, BSN, RN, CIC
Dennis Perrotta, PhD, CIC
Chip Riggins, MD, MPH
Maria C. Rodriguez, MD
Paul Southern, MD
APPENDIX B: DSHS Legionellosis reporting Form 5, 02/02; [Form ( PDF File: 31.9KB)]
APPENDIX C: Procedures for environmental testing for Legionella species
Specimen site selection protocol
1. Sample from all hot water tanks.
2. Sample from distal sites as follows:
a. If there are fewer than 500 hospital beds, sample from a minimum of 10 distal sites.
b. If there are more than 500 hospital beds, sample from 2 distal sites for every 100 beds.
Distal sites should be chosen from areas of the water system most likely to harbor Legionella (eg, areas where the bacteria have previously been found, dead ends), or other areas considered appropriate for the particular facility (eg, engineering factors associated with the growth of Legionella).
3. Sample first from faucets. If the faucets are culture-negative, sample again from showerheads.
Specimen collection protocol
a. Moisten the outlet by allowing 4-5 droplets of water to trickle through the opening.
b. Insert a sterile cotton or Dacron swab into the faucet and rotate it 4 times around the inner circumference, beginning at the opening and moving up the faucet as far as the swab will reach.
c. Place the swab into the designated container.
d. If the swab system does not contain a transport medium, then allow 0.5 mL of water to flow from the faucet into the container to keep the swab moist.
a. Moisten the showerhead by allowing 4-5 droplets of water to trickle through the opening.
b. Rotate a sterile cotton or Dacron swab over the entire surface of the showerhead 4 times.
c. Place the swab into the designated container.
d. If the swab system does not contain a transport medium, then allow 0.5 mL of water to flow from the showerhead into the container to keep the swab moist.
3. Hot water tanks
a. Open the drain valve at the base of the tank.
b. Immediately collect 10-50 mL into a sterile specimen container.
c. Let water drain out of the pipe for 15-30 seconds to flush out residual water within the drainpipe.
d. Collect another 10-50 mL into a second specimen container.
This procedure ensures that both residual water in the drainpipe and water from the tank are sampled.
4. Refrigerate samples at 2-8oC.
1. Treat each swab or water sample with acid buffer (0.2 M HCl-KCl, pH 2.2) for 3 minutes. This maximizes the recovery of Legionella species and minimizes the growth of competing microorganisms.
2. Treat specimens.
a. Swabs: Immerse swab in 2.5 mL of acid buffer and shake vigorously.
b. Water samples:
i. Concentrate specimens by centrifugation at 1,000 X g for 10 minutes.
ii. Remove all but 1 mL of the supernatant and vortex the remaining specimen.
3. Inoculate samples.
a. Inoculate all samples onto both BCYE (nonselective medium) and DGVP (selective medium).
i. BCYE: buffered charcoal yeast extract
ii. DGVP: BCYE with glycine, vancomycin, polymyxin B, alpha-ketoglutarate, bromothymol blue and bromocresol purple dyes
i. Inoculate down the center of a plate by turning the swab to expose the entire surface.
7 ii. Use a sterile inoculating loop to streak the plate perpendicularly.
b. Water samples:
i. Plate 0.1 mL onto the media.
ii. Distribute the samples by using the spread plate technique.
4. Incubate plates at 35-37oC for 5-7 days.
5. Identification of isolates is based on colonial morphology, color, and inability to grow on blood agar. Serogrouping of Legionellaceae is done by slide agglutination and/or direct fluorescent antibody testing.
References: 42, 61, 67
APPENDIX D - Comparison table of Legionnaires' disease prevention and control guidelines
Texas Department of State Health Services - Infectious Disease Control Unit
1100 West 49th Street, Suite T801, Mail Code: 1960 PO BOX 149347 - Austin, TX 78714-9347
(512) 776-7676 - Fax: (512) 776-7616 - E-Mail