Nosocomial Legionnaires' disease caused by Legionella pneumophila serogroup 5: laboratory and epidemiologic implications

Molecular Typing of Legionella pneumophila Isolates in the Province of Quebec from 2005 to 2015

Legionella is found in natural and man-made aquatic environments, such as cooling towers and hot water plumbing infrastructures. Legionella pneumophila serogroup 1 (Lp1) is the most common etiological agent causing waterborne disease in the United States and Canada. This study reports the molecular characterization of Lp strains during a 10 year period. We conducted sequence-based typing (SBT) analysis on a large set of Lp isolates (n = 284) to investigate the province of Quebec sequence types (STs) distribution in order to identify dominant clusters. From 2005 to 2015, 181 clinical Lp isolates were typed by SBT (141 sporadic cases and 40 outbreak related cases). From the same period of time, 103 environmental isolates were also typed. Amongst the 108 sporadic cases of Lp1 typed, ST-62 was the most frequent (16.6%), followed by ST-213 (10.2%), ST-1 (8.3%) and ST-37 (8.3%). Amongst other serogroups (SG), ST-1327 (SG5) (27.3%) and ST-378 (SG10) (12.2%) were the most frequent. From the environmental isolates, ST-1 represent the more frequent SBT type (26.5%). Unweighted pair group method with arithmetic mean (UPGMA) dendrogram from the 108 sporadic cases of SG1 contains 4 major clusters (A to D) of related STs. Cluster B contains the majority of the strains (n = 61) and the three most frequent STs in our database (ST-62, ST-213 and ST-1). During the study period, we observed an important increase in the incidence rate in Quebec. All the community associated outbreaks, potentially or confirmed to be associated with a cooling tower were caused by Lp1 strains, by opposition to hospital associated outbreaks that were caused by serogroups of Lp other than SG1. The recent major Quebec City outbreak caused by ST-62, and the fact that this genotype is the most common in the province supports whole genome sequencing characterization of this particular sequence type in order to understand its evolution and associated virulence factors.

Nosocomial pneumonia : rationalizing the approach to empirical therapy

Nosocomial pneumonia or hospital-acquired pneumonia (HAP) causes considerable morbidity and mortality. It is the second most common nosocomial infection and the leading cause of death from hospital-acquired infections. In 1996 the American Thoracic Society (ATS) published guidelines for empirical therapy of HAP. This review focuses on the literature that has appeared since the ATS statement. Early diagnosis of HAP and its etiology is crucial in guiding empirical therapy. Since 1996, it has become clear that differentiating mere colonization from etiologic pathogens infecting the lower respiratory tract is best achieved by employing bronchoalveolar lavage (BAL) or protected specimen brush (PSB) in combination with quantitative culture and detection of intracellular microorganisms. Endotracheal aspirate and non-bronchoscopic BAL/PSB in combination with quantitative culture provide a good alternative in patients suspected of ventilator-associated pneumonia. Since culture results take 2–3 days, initial therapy of HAP is by definition empirical. Epidemiologic studies have identified the most frequently involved pathogens: Enterobacteriaceae, Haemophilus influenzae, Streptococcus pneumoniae and Staphylococcus aureus (‘core pathogens’). Empirical therapy covering only the ‘core pathogens’ will suffice in patients without risk factors for resistant microorganisms. Studies that have appeared since the ATS statement issued in 1996, demonstrate several new risk factors for HAP with multiresistant pathogens. In patients with risk factors, empirical therapy should consist of antibacterials with a broader spectrum. The most important risk factors for resistant microorganisms are late onset of HAP (≥5 days after admission), recent use of antibacterial therapy, and mechanical ventilation. Multiresistant bacteria of specific interest are methicillin-resistant S. aureus (MRSA), Pseudomonas aeruginosa, Acinetobacter calcoaceticus- baumannii, Stenotrophomonas maltophilia and extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae. Each of these organisms has its specific susceptibility pattern, demanding appropriate antibacterial treatment. To further improve outcomes, specific therapeutic options for multiresistant pathogens and pharmacological factors are discussed. Antibacterials developed since 1996 or antibacterials with renewed interest (linezolid, quinupristin/dalfopristin, teicoplanin, meropenem, new fluoroquinolones, and fourth-generation cephalosporins) are discussed in the light of developing resistance.

Since the ATS statement, many reports have shown increasing incidences of resistant microorganisms. Therefore, one of the most important conclusions from this review is that empirical therapy for HAP should not be based on general guidelines alone, but that local epidemiology should be taken into account and used in the formulation of local guidelines.

Role of Environmental Surveillance in Determining the Risk of Hospital-Acquired Legionellosis: A National Surveillance Study With Clinical Correlations

Objective.

Hospital-acquired Legionella pneumonia has a fatality rate of 28%, and the source is the water distribution system. Two prevention strategies have been advocated. One approach to prevention is clinical surveillance for disease without routine environmental monitoring. Another approach recommends environmental monitoring even in the absence of known cases of Legionella pneumonia. We determined the Legionella colonization status of water systems in hospitals to establish whether the results of environmental surveillance correlated with discovery of disease. None of these hospitals had previously experienced endemic hospital-acquired Legionella pneumonia.

Design.

Cohort study.

Setting.

Twenty US hospitals in 13 states.

Interventions.

Hospitals performed clinical and environmental surveillance for Legionella from 2000 through 2002. All specimens were shipped to the Special Pathogens Laboratory at the Veterans Affairs Pittsburgh Medical Center.

Results.

Legionella pneumophila and Legionella anisa were isolated from 14 (70%) of 20 hospital water systems. Of 676 environmental samples, 198 (29%) were positive for Legionella species. High-level colonization of the water system (30% or more of the distal outlets were positive for L. pneumophila) was demonstrated for 6 (43%) of the 14 hospitals with positive findings. L. pneumophila serogroup 1 was detected in 5 of these 6 hospitals, whereas 1 hospital was colonized with L. pneumophila serogroup 5. A total of 633 patients were evaluated for Legionella pneumonia from 12 (60%) of the 20 hospitals: 377 by urinary antigen testing and 577 by sputum culture. Hospital-acquired Legionella pneumonia was identified in 4 hospitals, all of which were hospitals with L. pneumophila serogroup 1 found in 30% or more of the distal outlets. No cases of disease due to other serogroups or species (L. anisa) were identified.

Conclusion.

Environmental monitoring followed by clinical surveillance was successful in uncovering previously unrecognized cases of hospital-acquired Legionella pneumonia.

Presence and Chromosomal Subtyping ofLegionellaSpecies in Potable Water Systems in 20 Hospitals of Catalonia, Spain

Objective:

To investigate the presence and clonal distribution ofLegionellaspecies in the water supply of 20 hospitals in Catalonia, Spain.

Setting:

20 hospitals in Catalonia, an area of 32,000 km2, located in northeast Spain.

Methods:

Environmental cultures of 186 points of potable water supply and 10 cooling towers were performed for the presence ofLegionellaspecies. Following filtration and acid treatment, the samples were seeded in selective MWY (modified Wadowsky Yee)-buffered charcoal yeast extract-a agar. All isolates obtained were characterized microbiologically and genotyped bySfilpulsed-field gel electrophoresis (PFGE).

Results:

73 of 196 water samples, representing 17 of the 20 hospitals included in the study, were positive forLegionella pneumophila(serogroups 1, 2-14, or both). The degree of contamination ranged from 200 to 74,250 colony-forming units/L. Twenty-five chromosomal DNA subtypes were detected by PFGE. A single DNA subtype was identified in 10 hospitals, 2 DNA subtypes were observed in 6 hospitals, and 1 hospital exhibited 3 different DNA subtypes. Each hospital had its ownLegionellaDNA subtype, which was not shared with any other hospitals.

Conclusions:

Legionellawas present in the water of most of the hospitals studied; each such hospital had a unique, dominant chromosomal DNA subtype. The verification of several genomic DNA restriction profiles in such a small geographic area demonstrates the great genetic diversity ofLegionellain the aquatic environment.

Current and emerging Legionella diagnostics for laboratory and outbreak investigations

Legionnaires' disease (LD) is an often severe and potentially fatal form of bacterial pneumonia caused by an extensive list of Legionella species. These ubiquitous freshwater and soil inhabitants cause human respiratory disease when amplified in man-made water or cooling systems and their aerosols expose a susceptible population. Treatment of sporadic cases and rapid control of LD outbreaks benefit from swift diagnosis in concert with discriminatory bacterial typing for immediate epidemiological responses. Traditional culture and serology were instrumental in describing disease incidence early in its history; currently, diagnosis of LD relies almost solely on the urinary antigen test, which captures only the dominant species and serogroup, Legionella pneumophila serogroup 1 (Lp1). This has created a diagnostic "blind spot" for LD caused by non-Lp1 strains. This review focuses on historic, current, and emerging technologies that hold promise for increasing LD diagnostic efficiency and detection rates as part of a coherent testing regimen. The importance of cooperation between epidemiologists and laboratorians for a rapid outbreak response is also illustrated in field investigations conducted by the CDC with state and local authorities. Finally, challenges facing health care professionals, building managers, and the public health community in combating LD are highlighted, and potential solutions are discussed.

Aetiology, source and prevention of waterborne healthcare-associated infections: a review

The purpose of this review is to discuss the scientific literature on waterborne healthcare-associated infections (HCAIs) published from 1990 to 2012. The review focuses on aquatic bacteria and describes both outbreaks and single cases in relation to patient characteristics, the settings and contaminated sources. An overview of diagnostic methods and environmental investigations is summarized in order to provide guidance for future case investigations. Lastly, on the basis of the prevention and control measures adopted, information and recommendations are given. A total of 125 reports were included, 41 describing hospitalized children. All cases were sustained by opportunistic pathogens, mainly Legionellaceae, Pseudomonadaceae and Burkholderiaceae. Hot-water distribution systems were the primary source of legionnaires’ disease, bottled water was mainly colonized by Pseudomonaceae, and Burkholderiaceae were the leading cause of distilled and sterile water contamination. The intensive care unit was the most frequently involved setting, but patient characteristics were the main risk factor, independent of the ward. As it is difficult to avoid water contamination by microbes and disinfection treatments may be insufficient to control the risk of infection, a proactive preventive plan should be put in place. Nursing staff should pay special attention to children and immunosuppressed patients in terms of tap-water exposure and also their personal hygiene, and should regularly use sterile water for rinsing/cleaning devices.

Persistence of Legionella in hospital water supplies and nosocomial Legionnaires' disease

The molecular epidemiology of clinical and environmental Legionella species isolates was studied in seven hospitals from 1989 to 2006. The number of environmental pulsed field gel electrophoresis (PFGE) patterns ranged from one to nine according to the hospital. Genomic PFGE pattern persistence was observed in 71% of the hospitals, even after 17 years in some hospitals, and the relationship between environmental and clinical isolates was established. The isolates associated with hospital-acquired Legionnaires' disease corresponded to the persistent environmental PFGE patterns of Legionella pneumophila in potable water supplies.

Outbreak of Legionnaires' disease on a cruise ship linked to spa-bath filter stones contaminated with Legionella pneumophila serogroup 5

In January 2003, two cases of Legionnaires' disease associated with a ship's cruise were registered in the database of National Epidemiological Surveillance of Infectious Diseases. A 70-year-old male heavy smoker with mild emphysema contracted the disease during a cruise. Legionella pneumophila serogroup (sg) 5 was isolated from the patient's sputum and the ship's indoor spa. The isolate from the spa matched the patient's isolate by genotyping performed by pulsed-field gel electrophoresis (PFGE). The second case was in a 73-year-old female. During epidemiological investigation, a third case of Legionnaire's disease in a 71-year-old male was subsequently diagnosed among passengers on the same ship on the following cruise. Environmental investigation revealed that porous natural stones (Maifanshi) in the filters of the spas had harboured L. pneumophila, a phenomenon which has not been reported except in Japan. This is the first documented evidence of L. pneumophila sg 5 infection on a ship and of porous stones as a source of Legionella infection.

Legionnaire's disease: a nosocomial outbreak in Turkey

Six nosocomial cases of Legionella pneumophila occurred over a two-week period, with one further case being diagnosed retrospectively after 30 days. Strains isolated from the hospital water system were clonally related to a single sputum isolate. A sero-epidemiological investigation into legionella exposure amongst staff and inpatients was undertaken at the eight-year-old Inonu University Medical Centre in Turkey, which has 600 beds and central air conditioning. There is no disinfection programme for the hospital water system. A total of 500 serum samples (400 hospital staff and 100 inpatients) were screened for antibody to L. pneumophila by enzyme-linked immunosorbent assay (ELISA). Seroreactive cases were confirmed by a four-fold antibody rise in ELISA, a high indirect immunofluorescent assay (IFA) antibody titre or a positive urinary antigen test. ELISA showed that 24 (6%) of the 400 hospital staff and seven (7%) of the 100 inpatients had antibody titres higher than the cut-off value. ELISA-seroreactive cases were followed for two to four weeks. Of these subjects, seven (three patients and four staff) showed a four-fold rise in antibody titre by ELISA, six (three patients and three staff) had a high IFA titre, three patients with pneumonia had a positive urinary antigen test, and one of these patients also had a positive sputum culture. In addition, 22 water distribution systems were screened for the presence of L. pneumophila by culture. L. pneumophila was isolated from 15 sites. Pulsed-field gel electrophoresis typing indicated that all strains isolated from water systems were identical and clonally related to the strain isolated from sputum. Superheating and flushing of water systems were undertaken with legionella being re-isolated from four sites. Repeated superheating and flushing eliminated legionella completely. This study demonstrated that rapid detection of L. pneumophila and adequate superheating and flushing of water systems are effective for elimination and reduction of spread of this organism.

Legionella pneumonia due to exposure to 24-hour bath water contaminated by Legionella pneumophila serogroup-5

A 79-year-old man was admitted to hospital from his nursing home for treatment of pneumonia, but died 7 days after admission. Legionella pneumonia was diagnosed after isolation of Legionella pneumophila serogroup-5 from sputum culture. The environment of the nursing home was investigated; only water specimens from the 24-hour bath were positive by culture for Legionella pneumophila serogroup-5. Subsequent analysis by pulsed-field gel electrophoresis revealed an identical pattern in isolates from both sputum culture and 24 hour bath water culture. Among 123 inpatients and staff of the nursing home, 17 were found to be seropositive for Legionella pneumophila serogroup-5.

Presence and persistence of Legionella spp. in groundwater

Groundwater samples (111) from six different boreholes located in two geographical areas were examined for the presence of legionellae over a 7-year period. The number of Legionella isolates detected was generally low. The colonization of the aquifers was not uniform, and the persistence of Legionella was independent of the hydraulic pumps and the plumbing system present in the borehole. A total of 374 isolates identified by fatty acid methyl ester analysis belonged to Legionella pneumophila, L. oakridgensis, L. sainthelensi, and L. londiniensis. In area 1, L. oakridgensis constituted the major population detected, exhibiting only one random amplified polymorphic DNA (RAPD)-PCR profile. L. sainthelensi strains were less frequently isolated and also displayed a single RAPD profile, while L. pneumophila was only sporadically detected. In contrast, L. pneumophila comprised the vast majority of the isolates in area 2 and exhibited six distinct RAPD patterns, indicating the presence of different genetic groups; three L. londiniensis RAPD types were also detected. Two of the L. pneumophila and one of the L. londiniensis RAPD types were persistent in this environment for at least 12 years. The genetic structure of L. pneumophila groundwater populations, inferred from rpoB and dotA gene sequences, was peculiar, since the majority of the isolates were allied in a discrete group different from the lineages containing most of the type and reference strains of the three subspecies of L. pneumophila. Furthermore, gene exchange events related to the dotA allele could be envisioned.

Persistent Legionella pneumophila colonization of a hospital water supply: efficacy of control methods and a molecular epidemiological analysis

After a nosocomial outbreak caused by Legionella pneumophila serogroup 5, the hospital water distribution system, which was found to be colonized by L. pneumophila serogroups 5 and 6, was decontaminated by the superheat and flush method and by installing an additional heat-shock unit in one of the hot water circuits. This unit exposed the recirculated water to a temperature of 80 degrees C. The efficacy of the decontamination measures was evaluated by monitoring the temperatures and legionella concentrations at different parts of the hot water distribution system. The genetic diversity of the colonizing legionella flora was examined using two genotyping methods: amplified fragment length polymorphism analysis (AFLP) and random amplified polymorphic DNA (RAPD) analysis. Selected serogroup 6 strains were also analyzed by sequence-based typing (SBT). The results indicated that long-term eradication of serogroup 5 strains was never achieved. Only one serogroup 6 strain was never isolated after the superheat and flush. In all, according to genetic fingerprints, the diversity of Legionella strains in a hospital water system remains stable over the years regardless of the use of recommended disinfection procedures.

Ultraviolet light disinfection of hospital water for preventing nosocomial Legionella infection: a 13-year follow-up

BACKGROUND AND OBJECTIVE

CDC has estimated that 23% of Legionella infections are nosocomial. When a new hospital was being constructed and a substantial increase in transplantation was anticipated, an ultraviolet light apparatus was installed in the water main of the new building because 27% of water samples from taps in the old hospital contained Legionella. This study reports the rate of nosocomial Legionella infection and water contamination since opening the new hospital.

METHODS

Charts of all patients with positive Legionella cultures, direct immunofluorescent antibody (DFA), or urine antigen between April 1989 and November 2001 were reviewed. Frequencies of DFAs and urine antigens were obtained from the laboratory.

RESULTS

None of the 930 cultures of hospital water have been positive since moving into the new building. Fifty-three (0.02%) of 219,521 patients had a positive Legionella test; 41 had pneumonia (40 community acquired). One definite L. pneumophila pneumonia confirmed by culture and DFA in August 1994 was nosocomial (0.0005%) by dates. This patient was transferred after prolonged hospitalization in another country, was transplanted 11 days after admission, and developed symptoms 5 days after liver transplant. However, tap water from the patient's room did not grow Legionella. Seventeen (2.5%) of 670 urine antigens were positive for Legionella (none nosocomial). Thirty-three (1.2%) of 2,671 DFAs were positive, including 7 patients (21%) without evidence of pneumonia and 6 (18%) who had an alternative diagnosis.

CONCLUSION

Ultraviolet light usage was associated with negative water cultures and lack of clearly documented nosocomial Legionella infection for 13 years at this hospital.

Nosocomial Legionella pneumophila serogroup 5 outbreak associated with persistent colonization of a hospital water system

An outbreak of infections caused by Legionella pneumophila serogroup 5 was detected in a university hospital, and nosocomial reservoirs of the legionella epidemic were examined. Clinical isolates from two patients who had been affected by the L. pneumophila serogroup 5 outbreak, and from another patient with a legionella infection caused by the same serogroup 3 years later, were compared to L. pneumophila serogroup 5 isolates from the hospital water supply by two molecular methods, amplified fragment length polymorphism (AFLP) analysis and random amplified polymorphic DNA analysis (RAPD). Genotyping confirmed the epidemiological linkage of the first two patients, and linked their infections with the hospital water supply. The third clinical strain, which was also linked to the hospital water, was very similar to the epidemic strain. Even though the water distribution system was sanitized (superheat and flush sanitation), the epidemic strain was shown to be persisting in the hospital water outlets several years after its initial discovery.

Presence and chromosomal subtyping of Legionella species in potable water systems in 20 hospitals of Catalonia, Spain

OBJECTIVE

To investigate the presence and clonal distribution of Legionella species in the water supply of 20 hospitals in Catalonia, Spain.

SETTING

20 hospitals in Catalonia, an area of 32,000 km2, located in northeast Spain.

METHODS

Environmental cultures of 186 points of potable water supply and 10 cooling towers were performed for the presence of Legionella species. Following filtration and acid treatment, the samples were seeded in selective MWY (modified Wadowsky Yee)-buffered charcoal yeast extract-alpha agar. All isolates obtained were characterized microbiologically and genotyped by SfiI pulsed-field gel electrophoresis (PFGE).

RESULTS

73 of 196 water samples, representing 17 of the 20 hospitals included in the study, were positive for Legionella pneumophila (serogroups 1, 2-14, or both). The degree of contamination ranged from 200 to 74,250 colony-forming units/L. Twenty-five chromosomal DNA subtypes were detected by PFGE. A single DNA subtype was identified in 10 hospitals, 2 DNA subtypes were observed in 6 hospitals, and 1 hospital exhibited 3 different DNA subtypes. Each hospital had its own Legionella DNA subtype, which was not shared with any other hospitals.

CONCLUSIONS

Legionella was present in the water of most of the hospitals studied; each such hospital had a unique, dominant chromosomal DNA subtype. The verification of several genomic DNA restriction profiles in such a small geographic area demonstrates the great genetic diversity of Legionella in the aquatic environment.

Legionnaires' disease in a newly constructed long-term care facility

OBJECTIVES

To determine whether a newly-constructed long-term care facility would become colonized with Legionella and whether Legionnaires' disease would occur in residents of this new facility.

DESIGN

Prospective environmental surveillance of the hospital's water distribution system for the presence of Legionella pneumophila during construction. Utilization of diagnostic tests for Legionnaires' disease in cases of nosocomial pneumonia.

SETTING

The Pittsburgh VA Health Care System, Aspinwall Division, a two-building 400-bed complex.

PARTICIPANTS

Six patients who acquired Legionnaires' disease while in the facility.

INTERVENTION

Installation of copper-silver ionization systems.

MEASUREMENTS

Isolation of L. pneumophila from potable water and the occurrence of Legionnaires' disease.

RESULTS

L. pneumophila serogroup 1 was recovered from the water distribution system within 1 month of operation; 74% (61/82) of distal sites were positive during construction. In the first 2 years of occupancy, six cases of legionellosis were diagnosed. Both clinical isolates of L. pneumophila were identical to environmental isolates by pulsed field gel electrophoresis (PFGE). Copper-silver ionization systems were installed to control Legionella in the water system.

CONCLUSIONS

We conclude that long-term care residents are at risk for acquiring nosocomial Legionnaires' disease in the presence of a colonized water system, even in a newly constructed building.

Evaluation of the Binax and Biotest urinary antigen kits for detection of Legionnaires' disease due to multiple serogroups and species of Legionella

The Binax and the Biotest urinary antigen kits for the detection of Legionnaires' disease caused by organisms other than Legionella pneumophila were compared by testing 45 urine samples from non-Legionella pneumophila serogroup 1 patients previously positive in a broad-spectrum enzyme-linked immunosorbent assay (ELISA). Eighteen were positive with the Binax kit, and 13 were positive with the Biotest. Although neither kit is as sensitive as ELISA, these results extend the number of serogroups and species of Legionella that can be diagnosed with the Binax or Biotest kit.

An outbreak of Legionella micdadei pneumonia in transplant patients: evaluation, molecular epidemiology, and control

PURPOSE

To describe a nosocomial outbreak of Legionella micdadei pneumonia in transplant patients and to characterize the source of the outbreak and the control measures utilized.

SUBJECTS AND METHODS

We performed retrospective Legionella micdadei serologic testing to enhance case finding in transplant patients with pneumonia that lacked a documented microbial etiology, as well as prospective environmental surveillance of water sites and testing for Legionella in clinical specimens.

RESULTS

During a 3-month period, 12 cases of Legionella micdadei pneumonia were identified either by culture or serologic testing among 38 renal and cardiac transplant patients. Legionella micdadei isolates from hot water sources were found by pulsed-field gel electrophoresis to have a DNA banding pattern that was identical to the isolates from the first 3 culture-positive cases and from 2 cases that occurred 16 months later.

CONCLUSIONS

Hospitals caring for organ transplant recipients and other immunosuppressed patients must be aware of the possibility of environmental sources of outbreaks of Legionella infection. A first-line screen with the Legionella urine antigen test will identify Legionella pneumophila serogroup 1. However, specific cultures in outbreak situations should be considered to identify other Legionella pneumophila serotypes and the nonpneumophila Legionella species.

Single clonal origin of a high proportion of Legionella pneumophila serogroup 1 isolates from patients and the environment in the area of Paris, France, over a 10-year period

Arbitrarily primed PCR with three primers and pulsed-field gel electrophoresis were used to characterize a set of 75 clinical Legionella pneumophila serogroup 1 isolates, with no apparent epidemiological link, obtained from 24 hospitals in Paris, France, from 1987 to 1997. Unexpectedly, 25 clinical isolates from 15 hospitals had an identical profile (termed type A) by both methods. The same profile was subsequently found in 16 of 64 randomly selected environmental L. pneumophila serogroup 1 isolates from 15 different sites in the Paris area. There was no evidence of geographic clustering or a peak incidence of type A isolation. Type A has not been found in France outside the Paris area, suggesting that a particular type of L. pneumophila serogroup 1 is specifically present in the Paris water distribution network.

Nosocomial legionnaires' disease discovered in community hospitals following cultures of the water system: seek and ye shall find

BACKGROUND

The reservoir for hospital-acquired legionnaires' disease is the water distribution system. The Allegheny County (Pa.) Health Department recommended environmental cultures for all health care facilities for the prevention of hospital-acquired Legionella infection including facilities with no known cases of legionnaires' disease.

METHODS

Environmental cultures of hot water tanks, faucets, and showerheads were performed in six health care facilities according to health department guidelines. If hot water tanks, faucets, or showerheads yielded Legionella, monitoring with Legionella culture and urinary antigen was performed for all cases of nosocomial pneumonia.

RESULTS

Legionella was isolated from the water distribution system in 83% (five of six) of facilities. Three facilities dropped out of the study; two decided to disinfect the water and one had no Legionella in the water system. The other three facilities all discovered cases of legionnaires' disease during the 1-year study period after introduction of Legionella testing. L. pneumophilia, serogroups 1, 3, and 5, caused 12 cases of hospital-acquired legionnaires' disease. Positive diagnostic tests included: 10 of 12 (83%) urinary antigen, 6 of 8 (75%) respiratory cultures, and 2 of 5 (40%) serology. Molecular typing confirmed that the source of infection was the water supply in two hospitals.

CONCLUSION

Routine environmental cultures for Legionella in the water distribution system are recommended even if the hospital had not previously recognized cases of hospital acquired legionnaires' disease. The Allegheny County Health Department guidelines were inexpensive to implement and resulted in the discovery of cases that would have otherwise been undiagnosed.