Detection of Legionella DNA in human and guinea pig urine samples by the polymerase chain reaction

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.

Identification of legionella species by use of an oligonucleotide array

The genus Legionella contains a diverse group of motile, asaccharolytic, nutritionally fastidious gram-negative rods. Legionella pneumophila is the most important human pathogen, followed by L. micdadei, L. longbeachae, L. dumoffii, and other rare species. Accurate identification of Legionella spp. other than L. pneumophila is difficult because of biochemical inertness and phenotypic identity of different species. The feasibility of using an oligonucleotide array for identification of 18 species of Legionella was evaluated in this study. The method consisted of PCR amplification of the macrophage infectivity potentiator mip gene, followed by hybridization of the digoxigenin-labeled PCR products to a panel of 30 oligonucleotide probes (16- to 24-mers) immobilized on a nylon membrane. A collection of 144 target strains (strains we aimed to identify) and 50 nontarget strains (44 species) were analyzed by the array. Both test sensitivity (144/144 strains) and specificity (50/50 strains) of the array were 100%. The whole procedure for identification of Legionella species by the array can be finished within a working day, starting from isolated colonies. It was concluded that species identification of clinically relevant Legionella spp. by the array method is very reliable and can be used as an accurate alternative to conventional or other molecular methods for identification of Legionella spp.

Evaluation of real-time PCR for the early detection of Legionella pneumophila DNA in serum samples

Legionella pneumonia can be difficult to diagnose. Existing laboratory tests all have shortcomings, especially in the ability to diagnose Legionnaires' disease (LD) at an early stage of the disease in a specimen that is readily obtainable. The aim of this study was to assess the performance of PCR as a rapid diagnostic method and to compare the results of different PCR assays of serum samples from patients with LD. Samples included 151 serum samples from 68 patients with proven LD and 60 serum samples from 36 patients with respiratory tract infections other than Legionella. PCR assays were based on the 5S rRNA gene, 16S rRNA gene and the mip gene. The samples from patients with infections caused by pathogens other than Legionella all tested negative in PCR. Among the patients with proven LD 54.4 % (37/68) tested positive in 5S rRNA PCR, 52.9 % (36/68) in mip gene PCR and 30.9 % (21/68) in 16S rRNA PCR in the first available serum sample. The association between threshold cycle value in 5S PCR positive serum samples (n=49) and C-reactive protein value was determined, and showed a strong negative correlation (Pearson correlation coefficient r=−0.63, P<0.0001). In addition to existing tests for the diagnosis of LD, detection of Legionella DNA in serum could be a useful tool for early diagnosis of LD caused by any Legionella species and serogroup, and has the potential to provide a diagnosis in a time frame that could affect initial infection management.

Molecular genetic methods in the diagnosis of lower respiratory tract infections

Molecular diagnostic techniques, such as PCR, have become useful tools for the rapid etiological diagnosis of lower respiratory tract infections. Nucleic acid amplification tests (NAATs) have been evaluated for detecting most respiratory pathogens, and commercial assays are available for some pathogens. However, standardized protocols are needed before these assays are introduced into routine diagnostic use. For pneumonia, NAATs offer advantages over conventional tests for the detection of Mycoplasma pneumoniae, Legionella spp. and Chlamydia pneumoniae. For pneumococcal pneumonia in adults, PCR adds little to existing diagnostic tests, and is unable to distinguish pneumococcal colonization from infection when testing respiratory samples. Although less sensitive than culture-based methods, several commercial molecular diagnostic assays have been developed for tuberculosis and are useful rapid tests for selected patients. PCR can now be considered the rapid diagnostic test of choice for pertussis and some respiratory virus infections. Further work is required to better characterize the role of molecular diagnostic tests for diagnosing lower respiratory tract infections, and to develop standard assays that can be readily adopted by routine diagnostic laboratories.

Laboratory diagnosis of legionnaires’ disease due to Legionella pneumophila serogroup 1: comparison of phenotypic and genotypic methods

Laboratory results of 67 cases of legionnaires' disease caused by Legionella pneumophila serogroup (Sg) 1 spanning a 6-year period were analysed by both phenotypic and genotypic methods. The methods compared were urinary antigen enzyme immunoassay (EIA), an immunofluorescent antibody (IFA) test, direct fluorescent antibody (DFA), culture and a 5S rRNA PCR with Southern blotting confirmation. Urine was available in 53 cases, of which 35 (66%) were positive, with an antigen peak observed at 5-10 days after onset of disease symptoms. The IFA test was positive in 62 (92.5%) cases, with 56 (90.3%) cases producing a greater than fourfold rise in titre and 6 (9.7%) giving presumptive high titres of > or =1:128. There were two antibody peaks, one at 10-15 days and another at >25 days after onset. In 23 cases where samples were available, DFA and culture were respectively positive in 5 (22%) and 10 (48%) cases. There was a peak in culture-positives 5-10 days after onset of disease. A Legionella-specific 5S rRNA PCR on patient serum was positive in 54 (80.5%) cases, with a peak in PCR positivity at 6-10 days after disease onset. In 22 of the 67 cases, the full panel of diagnostic methods was available for comparison. The relative sensitivity and specificity of the urinary antigen EIA and the serum PCR was 100%. The IFA gave relative sensitivity and specificity values of 93.8 and 95%. DFA and culture, although 100% specific, produced only low sensitivities, of 19 and 42.8%, respectively. This study has shown that urinary antigen and serum PCR are valuable tests in the acute phase of disease, with excellent sensitivity and specificity values. At present, the Legionella species causing infection requires to be verified by IFA serology and/or culture, but this could become unnecessary as new antigen and L. pneumophila Sg 1-specific PCR tests become available.

Nucleic acid amplification tests for the diagnosis of pneumonia

Molecular diagnostic techniques, such as polymerase chain reaction (PCR), are promising tools for the rapid etiological diagnosis of pneumonia. PCR offers potential advantages over conventional tests for the detection of Mycoplasma pneumoniae, Legionella species, and Chlamydia pneumoniae. For pneumococcal pneumonia in adults, PCR adds little to existing diagnostic tests and is unable to distinguish pneumococcal colonization from infection when testing respiratory samples. Although PCR is probably more sensitive than are conventional microscopy-based methods for diagnosing Pneumocystis carinii pneumonia, the specificity is uncertain, because P. carinii can occasionally be detected in the absence of clinical symptoms. PCR is useful for the diagnosis of viral pneumonia in immunocompromised patients. Further work is required to better characterize the role of PCR versus the role of other tests for diagnosing pneumonia and to develop standard PCR assays that can be readily adopted by routine diagnostic laboratories.

Detection of Legionella DNA by PCR of whole-blood samples in a mouse model

A detection system for Legionella DNA in blood samples based on the PCR was developed and evaluated in A/J mice with experimentally induced Legionella pneumonia. Primers were designed to amplify a 106 bp DNA fragment of the 16S rRNA gene specific to Legionella species. The PCR system could detect clinically relevant Legionella species including Legionella pneumophila, Legionella micdadei, Legionella bozemanae, Legionella dumoffii, Legionella longbeachae, Legionella gormanii and Legionella jordanis. The sensitivity of the PCR system was 20 fg extracted DNA. In the mouse model, the blood PCR was compared with results obtained by PCR on bronchoalveolar lavage fluid (BALF) samples, cultures of blood and BALF and detection of Legionella urinary antigen. Blood PCR was positive until 8 days after infection, while BALF PCR became negative on day 4. These results indicate that PCR using blood samples may be a useful, convenient and non-invasive method for the diagnosis of Legionella pneumonia.

Diagnosis of Legionella infection

Legionellae, which are important causes of pneumonia in humans, continue to be incorrectly labeled as exotic pathogens. The ability to diagnose Legionella infection is limited by the nonspecific nature of clinical features and the shortcomings of diagnostic tests. Despite recent improvements, existing diagnostic tests for Legionella infection either lack sensitivity for detecting all clinically important legionellae or are unable to provide results within a clinically useful time frame. Understanding local Legionella epidemiology is important for making decisions about whether to test for Legionella infection and which diagnostic tests to use. In most situations, the use of both the urinary antigen test plus sputum culture is the best diagnostic combination. Polymerase chain reaction (PCR) is a promising tool, but standardized assays are not commercially available. Further work needs to focus on the development of urinary antigen tests assays that detect a wider range of pathogenic legionellae and on the development of standardized PCR assays.

Legionella and Legionnaires' disease: 25 years of investigation

There is still a low level of clinical awareness regarding Legionnaires' disease 25 years after it was first detected. The causative agents, legionellae, are freshwater bacteria with a fascinating ecology. These bacteria are intracellular pathogens of freshwater protozoa and utilize a similar mechanism to infect human phagocytic cells. There have been major advances in delineating the pathogenesis of legionellae through the identification of genes which allow the organism to bypass the endocytic pathways of both protozoan and human cells. Other bacteria that may share this novel infectious process are Coxiella burnetti and Brucella spp. More than 40 species and numerous serogroups of legionellae have been identified. Most diagnostic tests are directed at the species that causes most of the reported human cases of legionellosis, L. pneumophila serogroup 1. For this reason, information on the incidence of human respiratory disease attributable to other species and serogroups of legionellae is lacking. Improvements in diagnostic tests such as the urine antigen assay have inadvertently caused a decrease in the use of culture to detect infection, resulting in incomplete surveillance for legionellosis. Large, focal outbreaks of Legionnaires' disease continue to occur worldwide, and there is a critical need for surveillance for travel-related legionellosis in the United States. There is optimism that newly developed guidelines and water treatment practices can greatly reduce the incidence of this preventable illness.

Assessment of a new test to detect Legionella urinary antigen for the diagnosis of Legionnaires' Disease

Given that the rate of mortality by Legionella pneumonia increases in incorrectly treated patients, rapid diagnosis and early antibiotic treatment are needed. We have assessed the performance of a new enzyme immunoassay (EIA) test (Bartels Inc. Trinity Biotech Company, Wicklow, Ireland) to detect Legionella pneumophila antigen in urine comparing it to Binax EIA (Binax, Portland, Maine). We also evaluated the capability of both EIAs to detect extracted soluble antigens of Legionella strains. Using nonconcentrated urine samples (NCU) the sensitivity of Bartels EIA was 74.1% (66/89) and the sensitivity of Binax EIA was 51.7% (46/89). The sensitivity of both EIA tests were 91.5% (54/59) using concentrated urine samples (CU). Specificity of both EIA tests was 100% in NCU and CU. Bartels EIA was able to detect all serogroup L. pneumophila antigens, achieving a higher sensitivity in the case of L. pneumophila serogroup 1 soluble antigen. The new EIA was found to be a useful test for the rapid diagnosis of Legionella pneumonia, being a better alternative to the Binax EIA if NCU is used.

Development of conventional and real-time PCR assays for detection of Legionella DNA in respiratory specimens

The development and validation of a PCR assay based on the use of new 16S ribosomal DNA (rDNA)-targeted primers to detect Legionella DNA in respiratory specimens are described. The assay was originally developed as conventional PCR followed by electrophoretic detection and was then adapted to Lightcycler format with SYBR Green I detection and melting curve analysis. The 73 Legionella pneumophila strains tested were amplified with both applications. In addition, 21 and 23 out of 27 other Legionella strains were found positive by conventional and real-time PCR assays, respectively, including the clinically important species L. micdadei, L. bozemaniae, and L. dumoffii. Two DNA purification methods were compared using artificially seeded clinical specimens: a standard organic extraction method and a commercial kit based on adsorption of DNA to silica particles. The detection limit of the assay varied from 2 CFU to >200,000 CFU per ml of clinical specimen, depending on the background sample (i.e., pooled sputa or BAL fluids) and the DNA purification method, the silica method achieving lower detection limits. Analysis of 77 clinical samples (66 bronchoalveolar lavage fluid and 11 sputum samples) by conventional PCR yielded results that were consistent with Legionella culture results. The melting curve analysis in the Lightcycler system readily detected the specific amplification products. However, run-to-run variations in the measured melting temperatures required normalization against the standard sample in each run. The results obtained with the clinical specimens were similar to those obtained with conventional PCR, but more samples are required to determine whether the system can be applied to routine screening of samples for the presence of Legionella DNA.

Direct detection of Legionella species from bronchoalveolar lavage and open lung biopsy specimens: comparison of LightCycler PCR, in situ hybridization, direct fluorescence antigen detection, and culture

We developed a rapid thermocycling, real-time detection (also known as real-time PCR) method for the detection of Legionella species directly from clinical specimens. This method uses the LightCycler (Roche Molecular Biochemicals, Indianapolis, Ind.) and requires approximately 1 to 2 h to perform. Both a Legionella genus PCR assay and Legionella pneumophila species-specific PCR assay were designed. A total of 43 archived specimens from 35 patients were evaluated, including 19 bronchoalveolar lavage (BAL) specimens and 24 formalin-fixed, paraffin-embedded open lung biopsy specimens. Twenty-five of the specimens were culture-positive for Legionella (9 BAL specimens and 16 tissue specimens). BAL specimens were tested by LightCycler PCR (LC-PCR) methods and by a direct fluorescent antibody (DFA) assay, which detects L. pneumophila serogroups 1 to 6 and several other Legionella species. Tissue sections were tested by the two LC-PCR methods, by DFA, by an in situ hybridization (ISH) assay, specifically designed to detect L. pneumophila, and by Warthin-Starry (WS) staining. The results were compared to the "gold standard" method of bacterial culture. With BAL specimens the following assays yielded the indicated sensitivities and specificities, respectively: Legionella genus detection by Legionella genus LC-PCR, 100 and 100%; Legionella genus detection by DFA assay, 33 and 100%; and L. pneumophila detection by L. pneumophila species-specific LC-PCR, 100 and 100%. With open lung biopsy specimens the following assays yielded the indicated sensitivities and specificities, respectively: Legionella genus detection by LC-PCR 68.8 and 100%; Legionella genus detection by DFA assay, 44 and 100%; Legionella genus detection by WS staining, 63 and 100%; L. pneumophila species-specific detection by LC-PCR, 17 and 100%; and L. pneumophila species-specific detection by ISH, 100 and 100%. The analytical sensitivity of both LC-PCR assays was <10 CFU/reaction. LC-PCR is a reliable method for the direct detection of Legionella species from BAL specimens. The Legionella genus LC-PCR assay could be performed initially; if positive, L. pneumophila species-specific LC-PCR could then be performed (if species differentiation is desired). The speed with which the LC-PCR procedure can be performed offers significant advantages over both culture-based methods and conventional PCR techniques. In contrast, for the methods evaluated, culture was the best for detecting multiple Legionella species in lung tissue. WS staining, Legionella genus LC-PCR, and L. pneumophila species-specific ISH were useful as rapid tests with lung tissue.

Legionella and community-acquired pneumonia: a review of current diagnostic tests from a clinician's viewpoint

Many physicians are unaware of the limitations of the available tests for diagnosing infections with Legionella organisms. Geographic differences in the importance of nonpneumophila Legionella species as pathogens are underrecognized, in part because available diagnostic tests are biased toward the detection of pneumophila serogroup 1. Routine laboratory practices reduce the likelihood of culturing Legionella species from clinical isolates. Failure of seroconversion is common, particularly with nonpneumophila species; even when seroconversion occurs, it may take much longer than 4 weeks. Urinary antigen testing has insufficient sensitivity to affect clinical management in most regions of the United States, as it can reliably detect only L. pneumophila serogroup 1 infections. Polymerase chain reaction-based techniques offer hope of providing highly sensitive, rapid diagnostic tests for all Legionella species, but limitations in the current tests will make validating them difficult.

Detection of Legionella pneumophila using a real-time PCR hybridization assay

A real-time PCR hybridization assay for Legionella pneumophila is described; the assay uses LightCycler (Idaho Technology) methodology to specifically detect 2.5 CFU/reaction, equivalent to 1,000 CFU/liter of starting water sample. The assay, including DNA extraction and confirmation of product identity, is completed within 90 min of receipt of a sample.

Detection of Legionella DNA in peripheral leukocytes, serum, and urine from a patient with pneumonia caused by Legionella dumoffii

The polymerase chain reaction (PCR) has been used to detect Legionella DNA in respiratory tract, serum, and urine samples from patients with pneumonia. In addition, a preliminary study using a guinea pig model suggested that testing of peripheral leukocytes by PCR may be more sensitive than testing of other samples. We used PCR to detect Legionella DNA in serial peripheral leukocyte (buffy coat), serum, and urine samples from a patient with pneumonia caused by Legionella dumoffii. Legionella DNA was detected in all 3 sample types when first collected. Buffy coat and urine samples remained positive up to 56 days after the onset of symptoms, whereas serum samples were positive from 10 up to 16 days after the onset of symptoms. Sequencing of PCR amplicons indicated the presence of L. dumoffii DNA in positive samples. It appears that buffy coat may be a useful sample to test for Legionella DNA, but further study is required to determine the precise sensitivity and to make comparisons with other sample types.

Polymerase chain reaction for detection of Legionellae DNA in urine samples from patients with community-acquired pneumonia

Polymerase chain reaction (PCR) was used for detecting Legionella DNA in water, sputum, tracheal aspirate and bronchoalveolar lavage fluid. There is paucity of data on the use of PCR for detection of Legionella in serum and urine samples. In 82 patients admitted with community-acquired pneumonia, urinary PCR was used in addition to urinary antigen assay for Legionella pneumophila serogroup 1 and serological tests (indirect immunofluorescence and ELISA) in paired sera. PCR was positive in urine samples from 21 patients (26%): in six of seven patients with acute legionellosis by CDC criteria, and 15 patients with negative urine antigen showing no fourfold rise in antibody titers in immunofluorescence test.

Comparison of sample preparation methods for detection of Legionella pneumophila in culture-positive bronchoalveolar lavage fluids by PCR

A prospective study was conducted on 25 Legionella pneumophila culture-positive and 98 culture-negative bronchoalveolar lavage fluid samples to compare two DNA preparation methods: a rapid modified Chelex-based protocol and a proteinase K method. PCR was found to be more sensitive with the Chelex-based method (P = 0.03). N difference was found concerning the inhibition rate.

Application of polymerase chain reaction for detection of Legionella pneumophila in serum samples

OBJECTIVE: To apply the polymerase chain reaction (PCR) to serum samples for the rapid diagnosis of Legionnaire's disease using the L5SL9 and L5SR93 primers designed to generate a 104-base-pair (bp) fragment from the 5S RNA gene of Legionella spp. The amplified product was detected by electrophoresis and by hybridization with the L5S-1-specific probe. METHODS: Single specimens of serum obtained from 24 patients with confirmed legionellosis, at different stages of their disease, were tested by PCR. Additionally, 10 serum samples from patients with no clinical symptoms of pneumonia and 10 samples from patients suffering from pneumonia caused by Mycoplasma pneumoniae, Coxiella burnetii or Chlamydia psittaci were also tested as controls in order to determine the specificity of the method. RESULTS: Of the 24 examined serum samples, the amplified products from 12 hybridized with the L5S-1 probe (sensitivity 50%). None of the negative controls was positive after PCR. No correlation was found between the day of illness and the positivity in the test. CONCLUSIONS: The PCR technique could be applied as a diagnostic tool for the rapid diagnosis of legionellosis in serum samples after modification, mainly to improve its sensitivity.

Development of a new seminested PCR method for detection of Legionella species and its application to surveillance of legionellae in hospital cooling tower water

The presence of PCR inhibitors in water samples is well known and contributes to the fact that a practical PCR assay has not been developed for legionella surveillance. In this study, we devised a new seminested PCR assay for detection of Legionella spp. in water samples as a means of overriding the PCR inhibitors without loss of sensitivity. The seminested PCR assay utilized primers to amplify the 16S rRNA gene (LEG primers) of 39 Legionella spp. The assay was specific to legionellae, and the sensitivity was 1 fg of extracted Legionella DNA in laboratory examination. To evaluate the feasibility and sensitivity of the PCR assay in identifying the presence of legionellae, it was used to survey Legionella contamination in the water of 49 cooling towers of 32 hospitals. A commercially available EnviroAmp Legionella kit and a culture method were also used in the survey for comparison with the seminested PCR assay. The detection rates of legionellae in the samples were 91.8% (45 of 49) by the PCR assay and 79.5% (39 of 49) by the culture method. The EnviroAmp kit revealed that 30.6% of the water samples (15 of 49) contained inhibitors of the PCR amplification. However, the seminested PCR assay could produce the Legionella-specific DNA bands in 14 of the 15 samples. Although 8 of the 14 samples were positive in the first-step PCR, 6 of the 14 samples became positive in the second-step PCR. These results suggest that the effect of PCR inhibitors in samples, if any, can be reduced because of the dilution of the sample in the second-step PCR and that sensitivity of detection can be increased by the second-step PCR. Thus, the seminested PCR assay with LEG primers to amplify the 16S rRNA gene of 39 Legionella spp. was a practical and sensitive method to detect Legionella spp. in water samples.

Rapid diagnosis of Legionella pneumophila serogroup 1 infection with the Binax enzyme immunoassay urinary antigen test

The Binax legionella urinary antigen (LUA) enzyme immunoassay (Binax, Portland, Maine) was evaluated in 159 patients with suspected or proven legionellosis and 209 controls. A positive LUA test was found in 37% of patients with suspected legionellosis overall and in 83% of those with proven Legionella pneumophila serogroup 1 infection. The sensitivity of the LUA test was significantly greater than that of the direct fluorescent-antigen test (83 versus 42%; P < 0.0001) but not significantly different from that of culture (85%) or serology (91%); specificity was at least 99.5%.

Relevance of nucleic acid amplification techniques for diagnosis of respiratory tract infections in the clinical laboratory

Clinical laboratories are increasingly receiving requests to perform nucleic acid amplification tests for the detection of a wide variety of infectious agents. In this paper, the efficiency of nucleic acid amplification techniques for the diagnosis of respiratory tract infections is reviewed. In general, these techniques should be applied only for the detection of microorganisms for which available diagnostic techniques are markedly insensitive or nonexistent or when turnaround times for existing tests (e.g., viral culture) are much longer than those expected with amplification. This is the case for rhinoviruses, coronaviruses, and hantaviruses causing a pulmonary syndrome, Bordetella pertussis, Chlamydia pneumoniae, Mycoplasma pneumoniae, and Coxiella burnetii. For Legionella spp. and fungi, contamination originating from the environment is a limiting factor in interpretation of results, as is the difficulty in differentiating colonization and infection. Detection of these agents in urine or blood by amplification techniques remains to be evaluated. In the clinical setting, there is no need for molecular diagnostic tests for the diagnosis of Pneumocystis carinii. At present, amplification methods for Mycobacterium tuberculosis cannot replace the classical diagnostic techniques, due to their lack of sensitivity and the absence of specific internal controls for the detection of inhibitors of the reaction. Also, the results of interlaboratory comparisons are unsatisfactory. Furthermore, isolates are needed for susceptibility studies. Additional work remains to be done on sample preparation methods, comparison between different amplification methods, and analysis of results. The techniques can be useful for the rapid identification of M. tuberculosis in particular circumstances, as well as the rapid detection of most rifampin-resistant isolates. The introduction of diagnostic amplification techniques into a clinical laboratory implies a level of proficiency for excluding false-positive and false-negative results.

A nested polymerase chain reaction for detection of Legionella pneumophila in clinical specimens

OBJECTIVE: Because presently used methods for diagnosis of Legionella pneumonia lack sufficient sensitivity and sometimes specificity and rapidity, the detection of Legionella spp. by amplification of nucleic acids might be valuable. However, performing polymerase chain reaction (PCR) on clinical samples such as sputum is difficult because of the presence of extraneous DNA and inhibitors of the reaction. An attempt to circumvent these problems was made. METHODS: A nested PCR method was devised using primers from the mip gene of Legionella pneumophila. This PCR was tested on pure cultures of legionellae and clinical isolates of other bacteria. Clinical samples (bronchoalveolar lavage fluid, bronchial aspirate and sputum) from patients who suffered from legionellosis and samples from patients who suffered from other causes of pneumonia were also tested. RESULTS: The PCR was specific for L. pneumophila and no non-Legionella bacteria reacted. Ten to 50 colony forming units of Legionella in the sample could be detected. Twenty-two of 25 clinical samples were positive among patients suffering from pneumonia proven to be due to L. pneumophila serogroups 1, 3, 4, 5 and 6. Two of the three negative samples were from patients who had been treated with adequate therapy for at least 2 days and were culture negative. However, nine other culture-negative samples were PCR positive, of which seven came from patients who had been treated for 3-7 days. All pneumonia patients in the control group proved negative in PCR. A commercial kit for DNA preparation from clinical samples, based on absorption of nucleic acids to silica gel, was superior to the traditional phenol/chloroform extraction and increased the rapidity, simplicity and sensitivity of the procedure. CONCLUSIONS: A nested, simplified and rapid PCR method using mip primers proved to be more sensitive than culture and as sensitive and specific as other PCR procedures previously reported.

Legionella urinary antigen testing: potential impact on diagnosis and antibiotic therapy

Although Legionella is an important cause of severe pneumonia, difficulty still exists in its diagnosis. Because at least 80% of patients with legionellosis excrete the Legionella antigen in their urine, various methods have been investigated for urinary antigen detection. Specificity for these methods has been reported to be 100%, and sensitivity has been shown to vary between 70 and 100%. The advantages of these methods include ease of specimen collection, the ability to obtain large quantities of specimen for concentration, the ability to detect antigen after initiation of antibiotic therapy, and the ability to obtain results quickly. Disadvantages include the ability to only reliably detect urinary L. penumophila serogroup 1 antigen and the inability to diagnose relapse or reinfection due to persistence of antigen excretion. Of the commercially-available detection methods, the polyclonal enzyme-linked immunosorbent assay (ELISA) appears to be most efficient. Its use with routine Legionella screening procedures should be considered in target populations, with the intent of early diagnosis and antibiotic therapy streamlining.

Evaluation of the detection of Borrelia burgdorferi DNA in urine samples by polymerase chain reaction

It is difficult in some cases to identify an infection caused by Borrelia burgdorferi and to monitor the effect of therapy. Seropositivity will persist even after successful treatment and therefore may suggest ongoing infection. For direct detection of B. burgdorferi DNA in human urine samples, the polymerase chain reaction (PCR) was evaluated. A published primer system was selected, which amplifies a 259 bp fragment from the gene encoding the 23S rRNA. The lower detection limit of the primer system was 10 fg of extracted B. burgdorferi DNA. Several methods for the pretreatment of urine samples were tested. Of these, the Geneclean kit (Bio 101, USA) showed the best results. A total of 114 urine samples from 74 patients belonging to three clinical groups was investigated: (i) 51 samples from 26 patients with active Lyme disease, (ii) 36 samples from 27 patients with previous infection but no symptoms at the time the urine was collected, and (iii) 27 samples from 21 seronegative control patients without Lyme disease. B. burgdorferi DNA was detected in 25 urine samples of 17 patients with active disease, whereas 26 samples from this group of patients were negative. Only one asymptomatic case with previous infection showed a positive result, and the urine samples of the patients without Lyme disease were uniformly negative. Two of four patients from whom samples before and directly after onset of therapy were available converted from negative to positive PCR results after initiation of therapy, accompanied by the symptoms of a Jarisch-Herxheimer reaction.(ABSTRACT TRUNCATED AT 250 WORDS)