Detection of mycobacterium tuberculosis in paraffin-embedded pleural biopsy specimens by commercial ribosomal RNA and DNA amplification kits

STUDY OBJECTIVES

To evaluate the utility of two gene amplification systems in historical paraffin-embedded pleural biopsy (PEB) tissues from patients with pleural tuberculosis, and to compare the results to those obtained with conventional histologic and microbiological methods.

DESIGN

A retrospective study.

PATIENTS AND METHODS

Seventy-four formalin-fixed PEB tissues collected and stored over 12 years (1984 through 1995) were retrieved. Gene amplifications were performed in 57 tissues from patients with diagnoses of pleural tuberculosis and in 17 from patients with carcinoma as controls, using the first version of the Amplified Mycobacterium tuberculosis Direct Test (AMTDT; Gen-Probe; San Diego, CA) and the LCx Mycobacterium tuberculosis Assay (LCxMTB; Abbott Laboratories; Abbott Park, IL).

RESULTS

The sensitivities of the AMTDT and LCxMTB were 52.6% and 63.2%, respectively (p = not statistically significant). The specificity of both tests was 100%. Twenty tissue samples (35.1%) were positive by both systems, and 10 tissues (17.5%) were positive only by the AMTDT, while 16 tissues (28.1%) were positive only by the LCxMTB. Both tests gave negative results for 11 specimens (19.3%). When both tests were used, a positive diagnosis was achieved in 80.7% of the samples. Diagnosis of 73.7% of patient conditions had previously been made by smear examination of pleural biopsy and sputum, pleural liquid, or biopsy culture. The overall diagnostic yield with both culture and amplification techniques was 96.5% (55 of 57 patients) for pleural tuberculosis, with amplification techniques adding 22.8% of the diagnoses.

CONCLUSIONS

Amplification techniques are useful in archival PEB tissues, providing additional diagnoses beyond culturing, although the sensitivity should be improved, possibly by standardizing protocols.

Evolution of granulomas in lungs of mice infected aerogenically with Mycobacterium tuberculosis

Aerogenous infection of C57Bl/6 mice with a virulent strain of Mycobacterium tuberculosis (CL 511) leads to the formation of primary granulomas in the lung where neutrophils, macrophages and subsequently, lymphocytes accumulate progressively around an initial cluster of infected macrophages. The spread of infection through the lung parenchyma gives rise to secondary granulomas featuring numerous lymphocytes that surround a small number of infected macrophages. Afterwards, foamy macrophages add an outer layer to the granulomas, which characteristically respect the pulmonary interstitium and remain confined within the alveolar spaces. This feature, in conjunction with the constant presence of M. tuberculosis in the products of broncho-alveolar lavage, suggests that the upward bronchial migration of infected macrophages may contribute significantly to pulmonary dissemination of mycobacterial infection. The latter would be in agreement with the persistence of chronic pulmonary infection in spite of a concomitant strong T helper 1 cell response.

Effect of cisapride on intestinal bacterial overgrowth and bacterial translocation in cirrhosis

Deranged intestinal motility, which occurs in cirrhosis, may facilitate the development of intestinal bacterial overgrowth (IBO), which can lead to bacterial translocation (BT). To assess the effect of cisapride on IBO and BT in cirrhosis, cirrhotic rats received cisapride or a placebo for 7 days, and measurements of jejunal bacterial content and BT studies were performed. In addition, jejunal fluid from 46 cirrhotic patients was obtained for quantitative bacterial culture. Those patients in whom gram-negative IBO was detected were randomized to receive or not to receive cisapride (20 mg twice per day) for 1 week. Cisapride significantly reduced IBO in cirrhotic rats. In addition, no BT was documented in treated animals, whereas it occurred in 40% in nontreated cirrhotic rats. Total IBO was documented in 23 of 46 cirrhotic patients, which was caused by gram-negative organisms in 10 cases. Orocecal transit time (OCT) significantly decreased after cisapride therapy, and was associated with the abolishment of bacterial overgrowth caused by gram-negative organisms in 4 out of 5 treated patients, whereas it persisted in nontreated cases. Cisapride administration to cirrhotic rats resulted in a reduction of the IBO, which is associated with a marked decrease in BT. On the other hand, cisapride facilitates the abolition of IBO caused by gram-negative organisms in cirrhotic patients.

Evaluation of a fluorescence hybridisation assay using peptide nucleic acid probes for identification and differentiation of tuberculous and non-tuberculous mycobacteria in liquid cultures

The performance was evaluated of a fluorescence in situ hybridisation assay using peptide nucleic acid probes (Dako Probe MTB Culture Confirmation Test; Dako, Denmark) for identification of Mycobacterium tuberculosis complex (MTC) organisms and differentiation between tuberculous and non-tuberculous mycobacteria (NTM) in material taken directly from Bactec 12B (Becton Dickinson, USA) and MB/BacT (Organon Teknika, USA) bottles. The test was applied to 129 smear-positive (Ziehl-Neelsen stain) clinical specimens, 48 previously identified clinical strains of mycobacteria (12 MTC and 36 NTM), and 51 reference strains (7 MTC and 44 NTM) which were all previously inoculated into Bactec 12B and MB/BacT bottles. The sensitivity and specificity of the assay for MTC-positive cultures was 87.6% and 100%, respectively, for Bactec 12B, and 100%, respectively, for MB/BacT. The sensitivity and specificity of the assay for NTM-positive cultures was 100% for both media.

Prospective study of community-acquired pneumonia of bacterial etiology in adults

The aim of this study was to prospectively analyze the bacterial etiology of community-acquired pneumonia in adults in Spain. From May 1994 to February 1996, 392 episodes of CAP diagnosed in the emergency department of a 600-bed university hospital were studied. An etiological diagnosis based on noninvasive microbiological investigations was achieved in 228 cases (58%); 173 of these diagnoses were definitive and 55 probable. Streptococcus pneumoniae, which caused 23.9% of the episodes, was the predominant pathogen observed, followed by Chlamydia pneumoniae (13.5%) and Legionella pneumophila (12.5%). Other less frequent pathogens found were Haemophilus influenzae (2.3%), Pseudomonas aeruginosa (1.5%), Mycoplasma pneumoniae (1.3%), Coxiella burnetii (1%), Moraxella catarrhalis (2 cases), Nocardia spp. (2 cases), and Staphylococcus aureus (2 cases). Streptococcus pneumoniae was significantly more frequent in patients with underlying disease and/or age > or =60 years (28% vs. 13%, P = 0.002), while Legionella pneumophila was more frequent in patients below 60 years of age and without underlying disease (20% vs. 9%, P = 0.006). Likewise, Streptococcus pneumoniae and Legionella pneumophila were the most frequent etiologies in patients requiring admission to the intensive care unit, occurring in 29% and 26.3% of the patients, respectively. In addition to Streptococcus pneumoniae, other microorganisms such as Chlamydia pneumoniae and Legionella spp. should be seriously considered in adults with community-acquired pneumonia when initiating empiric treatment or ordering rapid diagnostic tests.

Evaluation of a rapid immunochromatographic assay for the detection of Legionella antigen in urine samples

A new immunochromatographic membrane assay for detecting Legionella pneumophila serogroup 1 antigen in urine samples (Binax Now Legionella Urinary Antigen Test; Binax, USA) was evaluated. Its sensitivity, specificity and level of agreement with the Binax enzyme immunoassay were compared using nonconcentrated and concentrated urine samples. The overall agreement between the two tests was 98.1%; the specificity of both was 100%. The sensitivity of the immunochromatographic assay was 55.5% in nonconcentrated urine and 97.2% in concentrated urine in comparison with the enzyme immunoassay, using concentrated urine as the reference test. This immunochromatographic assay screens successfully for Legionella pneumophila serogroup 1 soluble antigen in concentrated urine samples.

The intravenous model of murine tuberculosis is less pathogenic than the aerogenic model owing to a more rapid induction of systemic immunity

The detection of mRNA in the murine model of tuberculosis for key cytokines involved in protective immunity in the lung tissues revealed a much faster emergence of the interferon (IFN)-gamma response in the intravenous route than in the aerosol route of inoculation. This slower response in the lungs was associated with a stronger inflammatory response, resulting in large granulomatous structures and eventual tissue damage.

Comparison of a nonradiometric system with Bactec 12B and culture on egg-based media for recovery of mycobacteria from clinical specimens

The MB/BacT (Organon-Teknika, USA) is a fully automated, rapid, nonradiometric system for the culture of mycobacteria from clinical samples. The rate of recovery of mycobacteria and the time to detection obtained with the MB/ BacT were compared with those obtained with Löwenstein-Jensen and Coletsos solid media and Bactec 7H12 (12B) (Becton-Dickinson, USA) broth when 600 processed specimens were inoculated into all media in parallel. Specimens included 383 respiratory samples, 20 urine samples, 23 purulent exudates, 13 stool samples, 103 blood samples, 14 bone marrow aspirates, and 44 body fluid samples or aspirates. Overall, 106 mycobacterial isolates comprising six species were recovered, of which 100 (94.3%) were detected with MB/BacT, 98 (92.5%) with egg-based media, and 96 (90.2%) with Bactec 12B. The recovery rates of Mycobacterium tuberculosis complex with MB/BacT, egg-based media, and Bactec 12B were 98.7%, 93.7, and 89.9%, respectively. The average number of days to detection of single mycobacterial isolates was 14.2 days for MB/BacT, 26.1 days for egg-based media, and 11.7 days for Bactec 12B. The contamination rates were higher in MB/BacT (5%) than in Bactec 12B (1.8%) or egg-based media (1.5%). MB/BacT is a reliable, nonradiometric, less labor-intensive alternative to Bactec 12B for recovery of mycobacteria, but, as with other liquid culture methods, MB/BacT should be used in combination with a solid medium, not on its own.

Evaluation of Meridian ImmunoCard Mycoplasma test for the detection of Mycoplasma pneumoniae-specific IgM in paediatric patients

The Meridian ImmunoCard Mycoplasma kit, a 10-min card-based enzyme-linked immunosorbent assay (ELISA) designed to detect immunoglobulin M (IgM) antibodies to Mycoplasma pneumoniae was evaluated. We compared the ImmunoCard with the Fujirebio Serodia Myco II particle agglutination test, as well as with the complement fixation (CF) test to detect M. pneumoniae antibodies in paediatric patients. The ImmunoCard test and Serodia Myco II test agreed in 93.95%, and ImmunoCard test and CF test agreed in 83.51% of the 182 specimens tested. Nine specimens gave negative particle agglutination titres in the acute phase sample, and 28 specimens gave negative CF titres in the acute phase sample, although in the ImmunoCard test they were positive. These results may indicate that the ImmunoCard assay detects lower IgM levels of antibodies than the Serodia Myco II and CF test. The ImmunoCard appears to be a good screening assay test for M. pneumoniae IgM in children in whom M. pneumoniae IgM is found frequently.

Rapid diagnosis of extrapulmonary tuberculosis by ligase chain reaction amplification

A rapid amplification-based test for the diagnosis of extrapulmonary tuberculosis, the LCx Mycobacterium tuberculosis Assay from Abbott Laboratories, was evaluated. Results from the LCx M. tuberculosis Assay were compared with those from culture and the final clinical diagnosis for each patient. A total of 526 nonrespiratory specimens from 492 patients were tested. The specimens included urine; feces; lymph node exudates; pleural, cerebrospinal, articular, and ascitic fluids; tissue biopsies; gastric aspirates; purulent exudates; blood; and bone marrow aspirates. After combination of the culture results and the patient's clinical data, a total of 135 specimens were collected from 122 patients with a diagnosis of extrapulmonary tuberculosis. The sensitivity, specificity, and positive and negative predictive values for the LCx M. tuberculosis Assay were 77.7, 98.7, 95.2, and 93.1%, respectively; these values rose in resolved cases of TB to 78.5, 100, 100, and 93.1%, respectively. For 37 (27.4%) specimens from patients smear positive for the disease and 98 (72.6%) specimens from patients smear negative for the disease, the sensitivities of the LCx M. tuberculosis Assay were 100 and 71.1%, respectively. Statistically significant differences (P < 0.01) in sensitivities were found between culture and the LCx M. tuberculosis Assay. These differences were even greater among smear-negative specimens. The results demonstrate that the LCx M. tuberculosis Assay will provide rapid and valuable information for the diagnosis of extrapulmonary tuberculosis.

Evaluation of a commercial probe assay for detection of rifampin resistance in Mycobacterium tuberculosis directly from respiratory and nonrespiratory clinical samples

A commercial assay (Inno-Line Probe Assay; Innogenetics, Belgium) was evaluated to determine its ability to detect rifampin resistance in Mycobacterium tuberculosis directly from clinical specimens. Fifty-nine selected specimens (42 respiratory and 17 nonrespiratory) culture positive for Mycobacterium tuberculosis were tested along with their corresponding isolates in culture. The results were compared with those obtained by in vitro susceptibility testing. The results of the line probe assay to detect rifampin resistance in Mycobacterium tuberculosis present in clinical specimens and in cultured isolates were concordant for 58 of 59 (98.3%) isolates (95% confidence limits = 90.9-99.9%). The line probe assay failed only once, when a fecal specimen was tested; no amplification was observed due to the presence of inhibitory compounds. The most frequently observed mutation was His526-->Asp (58.7%), followed by the His526-->Tyr (23.9%); together, they represented 82.6% of rifampin-resistant samples. In conclusion, the Inno-Line Probe Assay is a rapid, useful method for detecting the presence of Mycobacterium tuberculosis complex and its resistance to rifampin directly from clinical specimens and culture. Moreover, since rifampin resistance is a potential marker for multidrug resistance in Mycobacterium tuberculosis, this assay may constitute an important tool for the control of tuberculosis.

Comparative evaluation of initial and new versions of the Gen-Probe Amplified Mycobacterium Tuberculosis Direct Test for direct detection of Mycobacterium tuberculosis in respiratory and nonrespiratory specimens

We evaluated the initial version of the Amplified Mycobacterium Tuberculosis Direct Test (Gen-Probe) (AMTDT 1) and the new version of AMTDT (AMTDT 2) for the detection of Mycobacterium tuberculosis directly from respiratory and nonrespiratory samples and compared the results with those of culture and staining methods. The assays were applied to 410 respiratory and 272 nonrespiratory samples collected from 515 patients. The combination of the culture results and clinical diagnosis was considered to be the "gold standard." Ninety-five respiratory specimens were collected from 67 patients with a diagnosis of pulmonary tuberculosis (TB) and 68 nonrespiratory specimens were collected from 61 patients with a diagnosis of extrapulmonary TB. With respiratory specimens, the sensitivity, specificity, and positive and negative predictive values were 83, 100, 100, and 96%, respectively, for AMTDT 1 and 94.7, 100, 100, and 98.4%, respectively, for AMTDT 2. With nonrespiratory specimens, the sensitivity, specificity, and positive and negative predictive values were 83, 100, 100, and 94%, respectively, for AMTDT 1 and 86.8, 100, 100, and 98.4%, respectively, for AMTDT 2. The overall results of AMTDT 1 and AMTDT 2 were concordant for 97% (661 of 682) of the samples. Statistically significant differences in sensitivities were found between AMTDT 1 and AMTDT 2 with respiratory specimens. It was concluded that although both nucleic acid amplification methods are rapid, sensitive, and specific for the detection of M. tuberculosis complex in all types of clinical samples, AMTDT 2 appeared to be more sensitive than AMTDT 1 when applied to smear-negative specimens. In contrast AMTDT 2 is more susceptible than AMTDT 1 to inhibitory substances in the amplification reaction. The turnaround time of AMTDT 2 is shorter (3.5 h) than that for AMTDT 1 (5 h).

Comparative evaluation of two commercial assays for direct detection of Mycobacterium tuberculosis in respiratory specimens

Two commercial systems for the amplification and detection of Mycobacterium tuberculosis directly from respiratory samples were compared. The Roche Cobas Amplicor MTB Test and the Roche manual Amplicor MTB Test (Roche Diagnostic Systems, USA) were applied to 755 decontaminated respiratory specimens collected from 470 patients. Results were compared with those of acid-fast staining and culture. A total of 251 specimens were collected from 156 patients diagnosed with pulmonary tuberculosis, including 28 specimens corresponding to 13 patients that were receiving antituberculous treatment. Given the overall positivity rate of 33.2% (251/755), the sensitivity, specificity, and positive and negative predictive values were 92.4, 100, 100, and 96.5%, respectively, for the Cobas Amplicor MTB Test and 90.8, 100, 100, and 95.8%, respectively, for the Amplicor MTB Test. For 204 (81.3%) smear positive specimens and 47 (19.7%) smear negative specimens, the sensitivity values were 100 and 59.6%, respectively, for the Cobas Amplicor MTB Test and 100 and 51%, respectively, for the Amplicor MTB Test. There were no statistically significant differences in sensitivity or specificity between the two assays and culture (p>0.05). The overall results of both assays were concordant for 99.5% of the samples. It is concluded that although both nucleic acid amplification methods are rapid and specific for the detection of Mycobacterium tuberculosis complex in respiratory specimens, the Cobas Amplicor MTB Test appears to be slightly more sensitive than the Amplicor MTB Test when smear negative specimens are investigated.

Translocated intestinal bacteria cause spontaneous bacterial peritonitis in cirrhotic rats: molecular epidemiologic evidence

BACKGROUND/AIMS

Intestinal bacterial translocation is common in cirrhotic rats with spontaneous bacterial peritonitis, and it is thought to play a major pathogenic role. There has so far been no evidence for clonality between bacteria isolated from intestine and ascites. This study aimed to use molecular epidemiology techniques to show that spontaneous bacterial peritonitis is due to translocated intestinal bacteria.

METHODS

Samples of ascitic fluid, portal blood, mesenteric lymph nodes and ileal contents from healthy (n=10) and ascitic cirrhotic rats with (n=12) or without (n=15) spontaneous bacterial peritonitis were cultured. In six infected rats, DNA macrorestriction fragments of 30 bacterial isolates [Escherichia coli (n=13), Enterococcus faecalis (n=12) and Proteus mirabilis (n=5)] from ascites (n=8), mesenteric lymph nodes (n=7), portal blood (n=6), and ileal flora (n=9) were compared.

RESULTS

Bacterial translocation was more frequent in animals with (58%) than in those without spontaneous bacterial peritonitis (20%, p=0.049) or controls (10%, p=0.026). The same bacterial strain was simultaneously isolated in ascites and in mesenteric lymph nodes and/or ileum in 7/8 (87%) instances. The identity rate for bacteria present in both ascites and mesenteric lymph nodes was 80% (4/5). Likewise, identity was demonstrated in 3/4 instances of bacteria found in both ascites and portal blood.

CONCLUSIONS

These results indicate that spontaneous bacterial peritonitis in cirrhotic rats is mainly due to intestinal bacteria translocated to mesenteric lymph nodes. Portal blood could be a less frequent route.

Occurrence of an antigenic triacyl trehalose in clinical isolates and reference strains of Mycobacterium tuberculosis

A careful re-examination of the glycolipid content of clinical isolates and reference strains of the tubercle bacillus, Mycobacterium tuberculosis, led to the identification of a glycoconjugate that passed unnoticed in earlier studies. Nuclear magnetic resonance spectroscopy, gas chromatography-mass spectrometry and chemical degradations were used to identify the glycolipid as a 2,3,6-triacyl trehalose. The glycolipid contains a phthienoic acyl substituent, a family of multimethyl-branched, alpha,beta-unsaturated fatty acids specific for virulent strains of the tubercle bacillus. It reacted with sera from tuberculosis patients with a specificity and sensitivity of 96.2% and 76%, respectively. Comparable data were obtained with the 2,3-diacyl trehaloses of M. tuberculosis and M. fortuitum and with the triacyl trehaloses of M. fortuitum, suggesting that the antigens from the latter species may be used for the serodiagnosis of tuberculosis.

Rapid detection of Mycobacterium tuberculosis in respiratory specimens, blood and other non-respiratory specimens by amplification of rRNA

SETTING

Diagnostic methods employing gene technology based on amplification of DNA or RNA are expected to improve the speed, sensitivity, and specificity of Mycobacterium tuberculosis detection. The Amplified Mycobacterium Tuberculosis Direct Test (AMTDT) enables the amplification and detection of M. tuberculosis rRNA directly from respiratory specimens.

OBJECTIVE

To evaluate the performance of the AMTDT in direct detection of M. tuberculosis in respiratory specimens, blood and other clinical samples, and to compare this method with conventional culture and staining techniques.

DESIGN

A total of 554 samples from 450 patients were examined in this study. All clinical specimens (with the exception of bone marrow aspirates and blood samples) were digested and decontaminated with sodium dodecyl (lauryl) sulfate (SDS)-NaOH. Bone marrow aspirates and blood samples were treated with 10% SDS. All processed samples were stained by auramine-rhodamine fluorochrome and inoculated onto Löwenstein-Jensen and Coletsos solid media, and into BACTEC-12B medium. In addition, the blood samples were inoculated into BACTEC 13A medium. The AMTDT was performed according to manufacturer's instructions. In those cases where discrepant results were obtained for AMTDT and cultures, patients' clinical data and other microbiological results were evaluated.

RESULTS

The sensitivity, specificity, and positive and negative predictive values for AMTDT were 87.5, 100, 100, and 96.7%, respectively, in respiratory specimens and 86.8, 100, 100, and 92.8%, respectively, in non-respiratory specimens. The differences in sensitivity of these two groups of specimens were not highly statistically significant (P > 0.005).

CONCLUSION

The sensitivity and specificity of the AMTDT were satisfactory for detection of M. tuberculosis in all types of clinical samples. Some minor changes in assay format and laboratory protocols may increase the sensitivity of the AMTDT without adversely affecting its specificity.

Pancoast's syndrome due to chronic pneumonia by Pasteurella multocida

Infectious causes of Pancoast's syndrome are extremely rare. We describe the case of a patient with Pancoast's syndrome due to chronic pneumonia resulting from Pasteurella multocida. The patient was not immunosuppressed and had had no contact with animals. The diagnosis was made by transthoracic needle aspiration and institution of therapy with cefuroxime-axetil resulted in resolution of his symptoms.

Detection of lipoarabinomannan antibodies in patients with newly acquired tuberculosis and patients with relapse tuberculosis

A commercially available dot immunoassay that employs the lipoarabinomannan antigen was evaluated for the serologic diagnosis of tuberculosis. The test showed a high specificity (100%); however, its sensitivity was low (18.5%). Antibodies to lipoarabinomannan were detected in the sera of 7 of 71 patients with newly acquired tuberculosis and in sera of 10 of 21 patients with relapse tuberculosis. It has been shown by others that sera from patients with relapse tuberculosis had a higher concentration of antibodies and reacted with a greater variety of antigens (native culture filtrates of Mycobacterium tuberculosis H37Rv) than did sera from patients with newly acquired tuberculosis. Our data confirm the results of these previous studies as far as lipoarabinomannan is concerned. We conclude that the differences in the production of antibodies shown by the two groups of tuberculous patients (new and relapse) must be taken into account when assessing the usefulness of serologic tests for the diagnosis of tuberculosis.

Multicenter clinical comparison of resin-containing bottles with standard aerobic and anaerobic bottles for culture of microorganisms from blood

In a study comparing the Bactec 9240 (Plus Aerobic/F and Anaerobic/F bottles, containing resins; Becton Dickinson, USA) and the Vital (standard aerobic and anaerobic bottles, with no additives; bioMérieux, France) blood culture systems, 6456 sets of four bottles of 9660 blood cultures submitted were evaluated. There were 531 clinically significant isolates from 795 positive blood cultures. Of the 531 positive blood cultures, 355 were positive in both systems, 141 with the Bactec 9240 alone, and 30 with the Vital alone (p < 0.001); five were not detected by either system. The average time to detection of positive cultures for the matched sets was 10.65 h and 18.41 h by the Bactec 9240 system and the Vital system, respectively. The false-positive rate per bottle was 0.65% in the Bactec 9240 and 0.71% in the Vital. The rate of false-negative pairs (i.e., major errors) was very low (0.12% for the Bactec 9240, 0.19% for the Vital) and not significantly different between the two systems. The striking differences in recovery of microorganisms may be due to the presence of resins in the Bactec medium. However, the observed superiority of the Bactec 9240, even for patients not receiving antibiotics, suggests that resins adsorb other inhibitors present in patients' blood.

Detection and identification of mycobacteria by amplification of RNA and DNA in pretreated blood and bone marrow aspirates by a simple lysis method

A sodium dodecyl (lauryl) sulfate method was evaluated for the preparation of blood specimens and bone marrow aspirates for use in two amplification procedures (Gen-Probe Amplified Mycobacterium Tuberculosis Direct Test [AMTDT] and Roche Amplicor M. avium/M. intracellulare [MAI] Test) for the detection and identification of Mycobacterium tuberculosis and M. avium and M. intracellulare, respectively. The AMTDT is based on amplification of rRNA, whereas the Amplicor MAI Test amplifies a specific DNA region of the 16S rRNA gene. The results of amplification techniques were compared with those of standard culture and culture in BACTEC 13A and BACTEC 12B liquid media. A total of 121 blood specimens and 15 bone marrow aspirates were collected from 136 AIDS patients. Mycobacterial growth was recovered for 103 specimens; 35 yielded M. tuberculosis, 62 yielded M. avium, 5 yielded M. genavense, and 1 yielded M. kansasii. The values of sensitivity and specificity in pretreated specimens for detection of M. tuberculosis by the AMTDT were 94.3 and 100%, respectively, and those for detection of M. avium by the Amplicor MAI Test were 91.9 and 100%, respectively. The simple lysis method described in the present work allows the recovery of mycobacteria from blood specimens and bone marrow aspirates and may be used in combination with the AMTDT and the Amplicor MAI Test to detect and identify different members of the genus Mycobacterium. This method might also be applicable for the identification of mycobacteria from blood culture fluids with acridinium-ester-labeled DNA probes.

Inactivation of hepatitis B virus: evaluation of the efficacy of the disinfectant 'Solprogel' using a DNA-polymerase activity assay

The effects of sodium dichloroisocyanurate (NaDCC) and Solprogel (Laboratorios Inibsa, S.A., Barcelona, Spain), a compound that contains NaDCC plus a biodegradable polymer of acrylic acid, on the activity of DNA polymerase (DNA-P) associated with hepatitis B virus in serum were evaluated. DNA-P positive and negative pools of human serum samples were used as positive and negative stock virus. Inhibition of DNA-P activity by NaDCC and the commercial product was found to be concentration-dependent. Two minutes exposure to the minimum effective concentration of NaDCC (1000 ppm available chlorine) or Solprogel 16% (960 ppm available chlorine) totally inhibited DNA-P activity.

Evaluation of the semiautomated Abbott LCx Mycobacterium tuberculosis assay for direct detection of Mycobacterium tuberculosis in respiratory specimens

Five hundred twenty processed respiratory specimens from 326 patients received for the diagnosis of tuberculosis or other mycobacterial infections were tested by means of the LCx Mycobacterium tuberculosis Assay from Abbott Laboratories, which uses ligase chain reaction technology for the direct detection of M. tuberculosis complex in respiratory specimens. The results of the LCx M. tuberculosis Assay were compared with the results of culture and staining techniques. After a combination of culture results and the patient's clinical data, a total of 195 specimens were collected from 110 patients who were positively diagnosed as having pulmonary tuberculosis. Twenty-three of these 195 specimens which corresponded to 10 patients with a history of pulmonary tuberculosis (TB) and anti-TB treatment ranging from 1 to 6 months were culture negative. The other 172 specimens were culture positive for M. tuberculosis. With an overall positivity rate of 37.5% (195 of 520 specimens), the sensitivity, specificity, and positive and negative predictive values were 90.8, 100, 100, and 94.7%, respectively, for the LCx M. tuberculosis Assay; 88.2, 100, 100, and 93.4%, respectively, for culture; and 82.6, 92, 72.9, and 97.6%, respectively, for acid-fast staining. For 161 specimens (82.6%) from patients smear positive for the disease and 34 specimens (17.4%) from patients smear negative for the disease, the sensitivity values for the LCx M. tuberculosis Assay were 98.8 and 53%, respectively. There were no statistically significant differences in the sensitivities and specificities between the LCx M. tuberculosis Assay and culture (P > 0.05). Conclusively, the LCx M. tuberculosis Assay has proved to have an acceptable sensitivity and a high specificity in detecting M. tuberculosis and has the potential of reducing the diagnosis time to an 8-h working day.

Comparison of radioimmunoassay and enzyme immunoassay kits for detection of Legionella pneumophila serogroup 1 antigen in both concentrated and nonconcentrated urine samples

We evaluated a commercial enzyme immunoassay (EIA) kit for detection of Legionella pneumophila serogroup 1 soluble antigen by comparing it to radioimmunoassay (RIA), using both concentrated and nonconcentrated urine samples. The sensitivity of EIA was 67.4% in nonconcentrated urine samples and 82.6% in concentrated urine samples. The sensitivity of RIA was 60.9% and 84.8% in nonconcentrated and concentrated urine samples, respectively. Our study indicates that the sensitivity and specificity of EIA are comparable to those of RIA, and that concentrating the antigen by selective ultrafiltration increases sensitivity for both EIA and RIA, with no significant decrease in specificity.