Detecting legionellosis by unselected culture of respiratory tract secretions and developing links to hospital water strains

Systematic active environmental surveillance successfully identified and controlled the Legionella contamination in the hospital

INTRODUCTION

Legionella disease can manifest as severe respiratory tract infection with a high mortality rate and is sometimes associated with a hospital outbreak by a contaminated water supply. A patient with breast cancer admitted about a month before. High fever was observed 18 days after admission and the Legionella antigen test showed the positive result.

METHODS

Due to the incidence of Legionella infection, we demonstrated the active surveillance of Legionella contamination in the entire hospital.

RESULTS

Cultures of her environmental samples revealed that hot water in two bathrooms were contaminated with Legionella. In our hospital, the hot water is heated and pumped up on the roof and distributed to each room. The contaminated bathrooms were related to the same plumbing. Therefore, we further collected samples throughout the hot water system. Legionella was not detected in the central part of the system. However, we detected Legionella in the hot water sampled from other five rooms, which were also associated with the same plumbing of the two bathrooms. The temperature and chlorine concentration of the hot water were not high enough to inactivate Legionella at the end of the plumbing. After the adjustment of the water temperature and chlorine concentration, Legionella became undetectable. Our prompt and active surveillance successfully identified the plumbing of the hot water system as the source of Legionella contamination and took precautions against future outbreaks.

CONCLUSIONS

Monitoring of water temperature and chloride concentration at the end of the hot water circulation is important to prevent nosocomial Legionella disease.

Environmental Cultures and Hospital-Acquired Legionnaires' Disease: A 5-Year Prospective Study in 20 Hospitals in Catalonia, Spain

Objective:

To determine whether environmental cultures forLegionellaincrease the index of suspicion for legionnaires' disease (LD).

Design:

Five-year prospective study.

Setting:

Twenty hospitals in Catalonia, Spain.

Methods:

From 1994 to 1996, the potable water systems of 20 hospitals in Catalonia were tested forLegionella, Cases of hospital-acquired LD and availability of an “in-house”Legionellatest in the previous 4 years were assessed. After the hospitals were informed of the results of their water cultures, a prospective 5-year-study was conducted focusing on the detection of new cases of nosocomial legionellosis and the availability and use of Legionella testing.

Results:

Before environmental cultures were started, only one hospital had conducted active surveillance of hospital-acquired pneumonia and usedLegionellatests includingLegionellaurinary antigen in all pneumonia cases. Only one other hospital had used the latter test at all. In six hospitals,Legionellatests had been completely unavailable. Cases of nosocomial LD had been diagnosed in the previous 4 years in only two hospitals. During prospective surveillance, 12 hospitals (60%) usedLegionellaurinary antigen testing in house and 11 (55%) found cases of nosocomial legionellosis, representing 64.7% (11 of 17) of those with positive water cultures. Hospitals with negative water cultures did not find nosocomial LD.

Conclusions:

The environmental study increased the index of suspicion for nosocomial LD. The number of cases of nosocomial LD increased significantly during the prospective follow-up period, and most hospitals began using theLegionellaurinary antigen test in their laboratories.

Environmental Cultures and Hospital-Acquired Legionnaires' Disease: A 5-Year Prospective Study in 20 Hospitals in Catalonia, Spain

Objective:

To determine whether environmental cultures forLegionellaincrease the index of suspicion for legionnaires' disease (LD).

Design:

Five-year prospective study.

Setting:

Twenty hospitals in Catalonia, Spain.

Methods:

From 1994 to 1996, the potable water systems of 20 hospitals in Catalonia were tested forLegionella, Cases of hospital-acquired LD and availability of an “in-house”Legionellatest in the previous 4 years were assessed. After the hospitals were informed of the results of their water cultures, a prospective 5-year-study was conducted focusing on the detection of new cases of nosocomial legionellosis and the availability and use of Legionella testing.

Results:

Before environmental cultures were started, only one hospital had conducted active surveillance of hospital-acquired pneumonia and usedLegionellatests includingLegionellaurinary antigen in all pneumonia cases. Only one other hospital had used the latter test at all. In six hospitals,Legionellatests had been completely unavailable. Cases of nosocomial LD had been diagnosed in the previous 4 years in only two hospitals. During prospective surveillance, 12 hospitals (60%) usedLegionellaurinary antigen testing in house and 11 (55%) found cases of nosocomial legionellosis, representing 64.7% (11 of 17) of those with positive water cultures. Hospitals with negative water cultures did not find nosocomial LD.

Conclusions:

The environmental study increased the index of suspicion for nosocomial LD. The number of cases of nosocomial LD increased significantly during the prospective follow-up period, and most hospitals began using theLegionellaurinary antigen test in their laboratories.

Assessing risk of health care-acquired Legionnaires' disease from environmental sampling: the limits of using a strict percent positivity approach

BACKGROUND

Elevated percent positivity (≥30%) of Legionella in hospital domestic water systems has been suggested as a metric for assessing the risk of health care-acquired Legionnaires' disease (LD).

METHODS

We examined the validity of this metric by analyzing data from peer-reviewed studies containing reports of Legionella prevalence in hospital water (ie, percent positivity) and temporally matched reports of patients with health care-acquired LD.

RESULTS

Our literature review identified 31 peer-reviewed publications reporting matched data. We abstracted a total of 206 data points, representing 119 hospitals, from these articles. We determined that the proposed 30% positivity metric has 59% sensitivity and 74% specificity (ie, a 41% false-negative rate and a 26% false-positive rate). These notable error rates could have significant implications, given that we identified 16 peer-reviewed articles and 6 government guidance documents that referenced the 30% positivity metric as a risk assessment tool.

CONCLUSIONS

Environmental sampling of hospital water distribution systems for Legionella can be an important component of risk management for LD. However, the possible consequence of using a percent positivity metric with low sensitivity and specificity is that many hospitals might fail to mitigate when a true risk is present, or might unnecessarily allocate limited resources to deal with a negligible risk.

Recovery of Legionella species from water samples using an internal method based on ISO 11731: suggestions for revision and implementation

The study aim was to determine retrospectively whether the parallel use of 2 media [buffered charcoal yeast extract (BCYE) and medium of Wadowsky and Yee (MWY)] to isolate Legionella spp. from water samples taken from hospital water supply systems increased the sensitivity of the culture method as compared with methods/protocols in which only seeding on a selective medium is used. We analyzed the results obtained from 931 positive water samples. In 484 of the 931 positive water samples, Legionella spp. was isolated in the presence of other microorganisms; in 83% (400/484), we used MWY to count suspected colonies, which gave a lower number of unreadable plates. In the 447 samples containing only Legionella spp., the highest frequency of positive samples (93%, 418/447) was obtained with BCYE, whereas seeding on MWY yielded 78% (348/447) (P < 0.001). Evaluation of the influence of the media on the Legionella spp. counts obtained by the 2 media showed that BCYE agar produced significantly higher counts than MWY (P < 0.001). The major conclusions that may be drawn from our data are as follows: 1) BCYE gives a high recovery rate of positive samples (93%) and a much greater yield of Legionella spp. than MWY; 2) BCYE was necessary for the detection of non-L. pneumophila spp. which grew poorly on selective media; 3) selective media [MWY or GVPC (glycine, vancomycin, polymyxin B, and cycloheximide)] were necessary for the recovery of Legionella spp. when the non-selective medium (BCYE) was difficult to interpret because of contaminating background flora. The use of different media is recommended for routine water tests in hospitals.

Genetic diversity of Legionella pneumophila in hospital water systems

It has been shown that different patients who had acquired legionellosis in a hospital setting were infected with the same strain even years apart. However, there are no longitudinal data describing the molecular epidemiology of Legionella pneumophila strains that contaminate a water system. This raised the question if there are any shifts of L. pneumophila strains over time, or after carrying out control measures. Using genotyping on a large collection of isolates, we investigated in a retrospective study the distribution of L. pneumophila serogroups and PFGE types in six different hospitals of the University of Heidelberg between 1991 and 2001. A total of 2012 water samples were drawn for routine testing and for evaluation of control measures, 747 samples were positive for L. pneumophila. Serogroups were determined by latex agglutination or by direct fluorescence assay; and 515 L. pneumophila isolates from water systems and six from patients underwent PFGE typing after SfiI-restriction. We identified seven serogroups and 19 genotypes among the water isolates. Each hospital had one to four predominating PFGE types that were stable over the investigation period. The oldest buildings in hospitals 4 and 5 (built 1876 and 1907) had more types than the newest one (built 1986). In all hospitals PFGE types were identified that could be found only sporadically. Although each hospital had its own warm water supply, we identified types that could be found in more than one hospital. However, there was no overlap of types in buildings that were fed from different wells. Infrequently occurring nosocomial legionellosis (n=3) were only caused by predominant strains. Contamination of water supplies seemed to be dominated by stable genotypes, even after various control measures. Additional genotypes could be isolated sporadically, however, their pathogenetic relevance seemed to be questionable.

A proactive approach to prevention of health care-acquired Legionnaires' disease: the Allegheny County (Pittsburgh) experience

BACKGROUND

The Allegheny County Health Department (ACHD) in Pennsylvania distributed the first guidelines for prevention and control of health care-acquired Legionnaires' disease (LD) by 1995. The proactive approach advocated in the guidelines differed notably from that of the Centers for Disease Control and Prevention (CDC) by recommending routine environmental testing of the hospital water distribution system even when cases of health care-acquired Legionnaires' disease had never been identified.

OBJECTIVES

Our purpose was to (1) evaluate the impact of the ACHD guidelines on the Legionella diagnostic and preventive practices of health care facilities in Allegheny and surrounding counties and (2) compare the incidence of health care-acquired LD before and after issuance of the ACHD guidelines.

METHODS

CDC case reports of LD from 1991 to 2001 were tabulated and compiled by the ACHD Infectious Disease Unit and the Association for Professionals in Infection Control and Epidemiology, Inc, Three Rivers Chapter. A survey was distributed to 110 hospitals and long-term care facilities in the region. The results were analyzed as occurring either in the preguideline period (1991-1994) or postguideline period (1995-2001).

RESULTS

A significant decrease in the number of health care-acquired cases was demonstrated between the preguideline (33%) and postguideline (9%) periods (P=.0001). In contrast, community-acquired cases increased from 67% pre guideline to 91% post guideline. A total of 71% of the facilities were colonized with Legionella. Disinfection of the water distribution system was initiated by 44% of facilities. Use of urinary antigen testing significantly increased from 40% pre guideline to 79% post guideline (P=.0001).

CONCLUSIONS

Health care-acquired LD declined significantly after the issuance of guidelines for prevention and control of health care-acquired LD. The decline was associated with health care facilities performing routine environmental monitoring of their water distribution systems followed by the initiation of disinfection methods if indicated. Two unanticipated benefits were (1) cases of LD in the community and long-term care facilities were uncovered as a result of increased availability of Legionella tests and (2) litigation and unfavorable publicity involving ACHD hospitals ceased.

Prevention and control of health care-associated waterborne infections in health care facilities

The current article is a review of the public health risks attributable to waterborne pathogens in health care. The consequences of health care-associated infections (HAIs) are discussed. Not only are Legionella spp involved in HAIs, but also Pseudomonas aeruginosa, other gram-negative microorganisms, fungi, and amoeba-associated bacteria. This is particularly noteworthy among immunocompromised patients. New prevention strategies and control measures brought about through advanced planning, facility remodelling and reconstruction, disinfection, and filtration have resulted in a significant reduction of the incidence of waterborne HAIs. The positive consequences of a comprehensive multibarrier approach including prevention and control programs in health care facilities are discussed. Environmental cultures are now integrated within the infection control program of some European countries. In high-risk areas, the application of disposable sterile point-of-use filters for faucets and shower heads appears to be the practice of choice to efficiently control waterborne pathogens and to prevent infections.

Efficacy of new point-of-use water filter for preventing exposure to Legionella and waterborne bacteria

BACKGROUND

Legionella species cause health care-acquired infections in which immunocompromised patients are disproportionately affected. Epidemiologic studies have demonstrated that point-of-use water fixtures are the reservoirs for these infections. The current approach to prevention is system-wide chemical disinfection of the hospital water system. These methods affect both low-risk and high-risk areas. A more effective approach to prevention may be a targeted approach aimed at protecting high-risk patients. One option is the application of a physical barrier (filter) at the point-of-use water fixture.

OBJECTIVES

To evaluate the ability of point-of-use filters to eliminate Legionella and other pathogens from water.

METHODS

One hundred twenty-milliliter hot water samples were collected from 7 faucets (4 with filters and 3 without) immediately and after a 1-minute flush. Samples were collected every 2 or 3 days for 1 week. This cycle was repeated for 12 weeks. Samples were cultured for Legionella, total heterotrophic plate count (HPC) bacteria, and Mycobacterium species.

RESULTS

Five hundred ninety-four samples were collected over 12 cycles. No Legionella or Mycobacterium were isolated from the faucets with filters between T = 0 and T = 8 days. The mean concentration of L pneumophila and Mycobacterium from the control faucets was 104.5 CFU/mL and 0.44 CFU/mL, respectively. The filters achieved a greater than 99% reduction in HPC bacteria in the immediate and postflush samples.

CONCLUSIONS

Point-of-use filters completely eliminated L pneumophila and Mycobacterium from hot water samples. These filter units could prevent exposure of high-risk patients to waterborne pathogens.

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.

Hospital-acquired Legionnaires' disease: new developments

PURPOSE OF REVIEW

Hospital-acquired Legionnaires' disease is being increasingly discovered with the advent of rapid diagnostic techniques. This review examines both the clinical and political aspects of this important problem.

RECENT FINDINGS

New sources are being recognized, including the water supply of pediatric hospitals, long-term care facilities, and rehabilitation centers. Concern by the public, unfavorable publicity and litigation are now emerging as hospital-acquired Legionnaires' disease is coming under scrutiny by the lay media.

SUMMARY

Pro-active approaches to environmental detection and disinfection of hospital water systems are being demanded by public officials in place of the passive approach favored by many public health agencies.

Legionella pneumophila induces apoptosis via the mitochondrial death pathway

Legionella pneumophila has been shown to induce apoptosis within macrophages, monocytic cell lines and alveolar epithelial cells. The mechanisms and significance of L. pneumophila-associated apoptosis are not well understood. It has been speculated that L. pneumophila may induce apoptosis through ligation of death receptors by bacterial surface components or by secreted bacterial factors. Translocation of apoptotic factor(s) through the Dot/Icm secretion machinery followed by direct activation of caspases within the cytosol is discussed as another possible mechanism of apoptosis induction by L. pneumophila. Here, it is shown that L. pneumophila induced the mitochondrial release of cytochrome c in CD95 (Fas/Apo-1)-negative monocytic Mono Mac 6 cells, indicating that Legionella-induced apoptosis is mediated via the mitochondrial signalling pathway. In addition, blocking of the death receptor pathway at distinct stages using CD95-, FADD- or caspase-8-deficient Jurkat cells did not affect induction of apoptosis by L. pneumophila. Conversely, inhibition of the mitochondrial death pathway by overexpression of the anti-apoptotic protein Bcl-2 potently inhibited the processing of caspases and the induction of apoptosis. Therefore, these findings support a model in which the induction of apoptosis by L. pneumophila is mediated by activation of the intrinsic mitochondrial death pathway in the absence of external death receptor signalling.

Hospital-acquired legionellosis: solutions for a preventable infection

Hospital-acquired Legionnaires' disease has been reported from many hospitals since the first outbreak in 1976. Although cooling towers were linked to the cases of Legionnaires' disease in the years after its discovery, potable water has been the environmental source for almost all reported hospital outbreaks. Microaspiration is the major mode of transmission in hospital-acquired Legionnaires' disease; showering is not a mode of transmission. Since the clinical manifestations are non-specific, and specialised laboratory testing is required, hospital-acquired legionellosis is easily underdiagnosed. Discovery of a single case of hospital-acquired Legionnaires' disease is an important sentinel of additional undiscovered cases. Routine environmental culture of the hospital water supply for legionella has proven to be an important strategy in prevention. Documentation of legionella colonisation in the water supply would increase physician index of suspicion for Legionnaires' disease and the necessity for in-house legionella test methods would be obvious. Legionella is a common commensal of large-building water supplies. Preventive maintenance is commonly recommended; unfortunately, this measure is ineffective in minimising legionella colonisation of building water supplies. Copper-silver ionisation systems have emerged as the most successful long-term disinfection method for hospital water disinfection systems. There is a need for public-health agencies to educate the public and media that discovery of cases identifies those hospitals as providers of superior care, and that such hospitals are not negligent.

Control of nosocomial Legionnaires' disease by keeping the circulating hot water temperature above 55 degrees C: experience from a 10-year surveillance programme in a district general hospital

After a nosocomial outbreak of Legionnaires' disease in a 450-bed district general hospital in 1991, the circulating hot water temperature was kept above 55 degrees C as the sole control measure. From 1991 to 2000, all cases of nosocomial pneumonia were clinically monitored and tested for Legionella pneumophila serogroup 1 by serology or urinary antigen detection. Water samples from peripheral tap sites were cultured for Legionella spp. twice a year. An infection with L. pneumophila serogroup 1 was diagnosed in four out of 366 (1.1%) patients treated for nosocomial pneumonia, representing one case per 26,000 admissions. All patients were cured without complications. L. pneumophila serogroup 1 was isolated in 30 of 251 (12%) cultured hospital water samples during the monitoring period. We conclude that control of nosocomial Legionnaires' disease in a primary referral hospital is possible by keeping the circulating hospital hot water temperature above 55 degrees C, together with careful clinical surveillance. Complete eradication of Legionella spp. from the hot water system does not seem necessary.

Nosocomial legionellosis

Numerous reports of endemic legionellosis have been published within the past year. The scope has been expanded to longterm care facilities, nursing homes, rehabilitation centers, and pediatric hospitals. The institutional water supply has been the source in all reports and aspiration was explicitly linked as the mode of transmission in several reports. Discovery of a single case should not be considered as an isolated sporadic event, but instead indicative of unrecognized cases within that hospital. Copper-silver ionization has displaced hyperchlorination as the longterm disinfection modality of choice. Guidelines mandating the use of routine environmental cultures in hospital water supplies have been implemented in several American states and European countries.