Molecular cloning of a novel gene, dtsR, which rescues the detergent sensitivity of a mutant derived from Brevibacterium lactofermentum

Several strains of Corynebacterium and Brevibacterium are known for their ability to secrete large amounts of amino acids, especially L-glutamate. We focused on the mechanism of L-glutamate secretion triggered by a detergent, namely polyoxyethylenesorbitan monopalmitate (PESP). A mutant strain, AJ11060, derived from Brevibacterium lactofermentum ATCC 13869 indicates the sensitivity to PESP. A multicopy suppresser gene that compliments the sensitivity of AJ11060 to the detergent was derived from a gene library of B. lactofermentum AJ12036. A 2855-bp DNA fragment was cloned and sequenced. An open reading frame was found that coded for the rescuer gene of the sensitivity to PESP of AJ11060 and was designated dtsR. The expression of the dtsR gene in B. lactofermentum was confirmed by using anti-DtsR antibody. The deduced DtsR protein indicated significant homology with some biotin enzymes such as the beta chain of propionyl-CoA carboxylase from rat (48.3%) and human (48.7%), or a 12S chain of methylmalonyl-CoA carboxyltransferase from Propionibacterium freudenreichii (43.1%).

[Outbreaks of pulmonary tuberculosis in a family and in a hospital. Analysis of restriction-fragment-length polymorphisms]

Restriction-fragment-length polymorphism, analysis was used to study two outbreaks of pulmonary tuberculosis, one in a family and one in a hospital. The DNA probe was derived from the insertion sequence IS 6110. Two groups of isolates were analyzed, both of which were suspected to be common sources of each infection. Both groups showed identical fingerprints within each group. These results suggest that analysis of restriction-fragment-length polymorphism is useful in epidemiological studies of pulmonary tuberculosis.

[Detection of Mycobacterium tuberculosis in clinical specimens other than sputum by the Mycobacterium Tuberculosis Direct Test (MTD)--assessment of sample preparation methods and clinical evaluation]

The Gen-Probe Amplified Mycobacterium Tuberculosis Direct Test (MTD) has been widely used as a rapid test for the identification of Mycobacterium tuberculosis complex in clinical samples, and several research groups have verified its clinical usefulness. However, most of the specimens they tested were sputum, and there have been few reports on other specimens. In particular, there have been no reports on assessments of methods of preparing samples other than sputum for the MTD. We assessed methods of preparing samples other than sputum and the influence of a local anesthetic and an anticoagulant that may be present in samples, and also evaluated the MTD as a means of detecting M. tuberculosis in pleural fluid, bronchial lavage cerebrospinal fluid, urine and ascitic fluid. 1. Assessment of three sample preparation methods, i.e., the NALC-NaOH method GuSCN-Diatom nucleic acid extraction method, and the ultrasonication method, revealed that the combination of the NALC-NaOH method and the ultrasonication method, widely used to prepare sputum samples, is also a valid method of preparing other samples. 2. The local anesthetic and the anticoagulant used clinically and remained in specimens did not affect the results of the MTD. 3. Seven (36.8%) of 19 pleural fluid samples from patients diagnosed as tuberculous pleurisy were positive of M. tuberculosis by the MTD, while five (27.8%) of 18 pleural fluid samples cultured for bacteria were positive for M. tuberculosis complex. None of the 20 pleural fluid samples from patients diagnosed as non-tuberculous pleurisy were positive for M. tuberculosis complex either by MTD or culture. 4. Eight (32.0%) of 25 bronchial lavage samples from patients diagnosed as pulmonary tuberculosis were positive for M. tuberculosis complex by the MTD, while 3 (12.0%) were positive by culture. None of the 18 bronchial lavage samples from patients diagnosed as non-tuberculous disease were positive for M. tuberculosis complex either by the MTD or culture. Based on these results, it is concluded that the MTD is a very useful method of detecting M. tuberculosis in clinical samples other than sputum because it is more sensitive than culture on Ogawa's egg medium in detecting M. tuberculosis complex in pleural fluid samples, bronchial lavage samples, and so on, with the same preparation method as used for sputum.

Resistance to antituberculosis drugs in Japan

SETTING

Five years after the last survey of drug-resistant tuberculosis in Japan, a serious new phenomenon has gradually begun to appear. A nationwide survey was conducted by the Tuberculosis Research Committee.

OBJECTIVE

To determine resistance patterns to five anti-tuberculosis drugs and risk factors.

DESIGN

Cultures were obtained from patients hospitalized at 38 hospitals in various districts of Japan throughout 6 months, from 1 June through 30 November in 1992. Drug susceptibility testing was carried out in the national reference laboratory.

RESULTS AND CONCLUSIONS

Resistance to one or more drugs was found in 5.6% of new cases and 27.8% of recurrent cases (P < 0.001). About 88% of drug resistant isolates from the new cases were resistant to one drug, while 50.8% of the drug resistant isolates from the recurrent cases had resistance to two or more drugs (P < 0.001). Resistance rates to both isoniazid and rifampin in new cases was very low (only 0.14%). Primary drug resistance rates were higher in age groups less than 60 years old, compared to those of 60 years and over (P = 0.05). Compared with the rate in Japanese patients, foreign-born individuals had a higher resistance rate in the recurrent cases (P = 0.034). This survey indicated a similar trend in resistance rates to five antituberculosis drugs to those of the last survey in 1987.

[Evaluation of a new rapid detection system for mycobacteria using an oxygen sensitive fluorescent sensor]

A comparison of the rate of recovery and time for detection of mycobacteria from clinical specimens of the newly developed Mycobacteria Growth Indicator Tube (MGIT), the biphasic Septi-Chek, and the egg-based Ogawa medium was made. From the 305 sputum specimens processed, a total of 83 mycobacterial isolates were detected. From these 80 (84.3%) isolates were detected with both the MGIT and Septi-Chek systems, respectively, and 50 (60.2%) were detected by the Ogawa egg method. The difference in the percentages of positive cultures between the two systems based on liquid media and the Ogawa egg method was significant (p < 0.001). The mean time for the detection of the Mycobacterium tuberculosis complex were 16.3 days with the MGIT system, 25.6 days with the Septi-Chek, and 21.5 days with Ogawa egg method. These results indicate that the MGIT system is efficient for the recovery of mycobacteria.

[A study on prevalence of resistance to antituberculosis drugs in Japan: comparison of results in the local facilities and in the reference laboratory]

During five years since the last survey of drug-resistant tuberculosis in Japan, features of tuberculosis in Japan have been changed. A nationwide survey was conducted by the Tuberculosis Research Committee of Japan. A total of 38 hospitals in various districts of Japan participated in the cooperative study. Each collaborating laboratory sent all mycobacterial cultures isolated during 1 June to 30 November, 1992 to the reference laboratory of the Committee, where species of the isolates were identified and drug susceptibility of Mycobacterium tuberculosis isolates were reexamined. The reference laboratory received a total of 1,236 cultures. Among them, 290 cultures were excluded from further examination by various reasons, such as contamination (52 cultures), non-viability (53), growth of nontuberculous mycobacteria (182) and other reasons (3). Thus, drug susceptibility test results were available for 946 cultures, including 26 cultures from non-Japanese persons. In the local laboratories, two methods, the absolute concentration method using 1% Ogawa egg slant (standard method, 26 hospitals) and its modified method using a microwell plate (microtiter method, 12 hospitals), were used for drug susceptibility testing, and the standard method was used in the reference laboratory. The results in the local laboratories were compared with those in the reference laboratory. The overall coincidence rate between drug susceptibility results reported from the local laboratories and those from the reference laboratory was 92.5%. A high coincidence rate (94.3%) was seen when the standard method was used in both local and reference laboratories. On the other hand, the coincidence rates between the results with the microtiter method in the local laboratory and those with the standard method in the reference laboratory were lower (standard method vs microtiter method; P < 0.01). Out of 19 hospitals, when the isolates were tested by the standard method 17 (89.5%) showed high coincidence rates (over 85%). Three hospitals using the microtiter method showed the coincidence rate over 90%, while other three showed lower rate (less than 80%) with high overestimation rates (over 19%), indicating that there are variations among facilities in performing the microtiter test. A part of the results concerning the resistance patterns to five antituberculosis drugs will be reported elsewhere.

KatG sequence deletion is not the major cause of isoniazid resistance in Japanese and Yemeni Mycobacterium tuberculosis isolates

One of the mechanisms of isoniazid resistance to Mycobacterium tuberculosis has been proved to be the chromosomal deletion of katG. Based on this finding, 22 isoniazid-resistant isolates of M. tuberculosis obtained in Japan and Yemen were analysed for katG by polymerase chain reaction and catalase activity. Only six (27%) of the 22 isolates were compatible with the mechanism (lack of amplification of katG and loss of catalase activity). In contrast, eight isolates (36%) were katG positive but catalase activity-negative and eight (36%) were positive for both factors, indicating that isoniazid resistance is multifactorial and the deletion of katG was not the major cause of resistance in the isolates examined in this study.

[The mode of infection of tuberculosis--analysis using molecular epidemiologic methods]

In the 1950's, evidence showed that INH-resistant Mycobacterium tuberculosis organisms were attenuated in both virulence and pathogenicity in animals, and it was postulated that these bacilli might also be attenuated in their virulence to humans. Subsequent studies, however, indicated that all INH-resistant strains should not be considered as being attenuated in their virulence to humans. The general conclusion was that patients excreting INH-resistant organisms are somewhat less infectious to their contacts than patients excreting INH-susceptible organisms. Insertion sequences are suitable tools for the diagnosis and epidemiology of tuberculosis because of the highly variable copy number and variability of insertion sites in the chromosome. This variability allows the subtyping of M. tuberculosis strains by restriction fragment length polymorphism (RFLP) analysis. Patients with the same RFLP pattern constitute an epidemiologically linked cluster. Clustering indicates recent infection and rapid progression to clinical illness. Nearly one thirds of new cases of tuberculosis in San Francisco are the result of recent infection. In Thailand, tuberculosis has now emerged as the most common opportunistic disease associated with HIV infection. Cluster analysis showed the risk of progression to active tuberculosis among individuals infected with HIV. Ther have been numerous outbreaks of multidrug-resistant tuberculosis in the United States. Most of such outbreaks have primarily involved persons infected with HIV, who are thought to have been exposed to the strains in medical or correctional facilities.

[Epidemiology of Mycobacterium tuberculosis infection based on RFLP analysis]

In Japan, the decline of the tuberculosis incidence rates has been slowed down since 1970s. To study factors influencing this slow down of the decline, we have carried out the analysis of RFLP patterns of 941 strains of M. tuberculosis which were isolated at 38 hospitals in various districts of Japan in 1992. The outline of the results is as follows; (1) Distribution of the number of IS6110: The number of the occurring IS elements varies from 1 to 19, and the majority of the isolates have 9 to 14 copies. This finding is identical to the result of the previous investigation carried out in 1987 using 123 strains of M. tuberculosis. There were groups of individuals with identical patterns among those having the same number of copies. The characteristics of the RFLP pattern variety in Japan looks like that of Africa where tuberculosis in highly prevalent. In our country, however, it is considered that the influence of elderly people is very important. Thirty-seven strains contained only one hybridizing band. In 35 of these strains the copy was observed in a 7.9 kbp fragment, and in the other two strains the copy was observed in a 1.5 kbp fragment. Isolates which contain only one or small number of copies could not be differentiated by IS6110, so that other targets for RFLP analysis such as IS1081, DR sequence, and PGRS are to be further investigated. (2) Cluster analysis was shown to be an appropriate epidemiological methodology.(ABSTRACT TRUNCATED AT 250 WORDS)

[Reproducibility of MTD system for detection of Mycobacterium tuberculosis: a cooperative study among six laboratories]

The Gen-Probe Amplified Mycobacterium Tuberculosis Direct Test (MTD) is a rapid test for the detection of Mycobacterium tuberculosis, utilizing the rRNA amplification method. For assessing the reliability and reproducibility of the method, a co-operative blind study was conducted among 6 laboratories. Materials for test were sputum and water samples containing known numbers of Mycobacterium bovis BCG or Mycobacterium avium, and samples without bacteria. From three of 6 laboratories, false-positive results were reported for bacteria negative samples, however, the ratio was below 10%; 8.3% (3/36 samples), 5.6% (2/36), and 2.8% (1/36), respectively. It indicates the indispensability of negative controls for sample pretreatment and RNA extraction stages in the routine MTD test. In every laboratory, all the samples with 10(2) BCG in water and 10(4) BCG in sputum were found to be MTD positive. For the sputum samples with 10(2) BCG, positive results with the ratio above 80% were reported from 4 laboratories. These results indicate that the MTD test based on rRNA amplification method is quite useful for the rapid diagnosis of M. tuberculosis infection.

[An outbreak of tuberculosis involving foreign workers from South America]

A twenty-four year old male Peruvian of Japanese origin, who came to Japan in September 1990 and had been working in a minor factory in a rural area, was admitted to a hospital in March '91 with severe cough. Smear examination of his sputum smear was positive for acid-fast bacilli and his chest X-ray showed multiple cavities (Index case). Subsequent contact examination identified further four patients with pulmonary tuberculosis among his colleagues in the factory, all of whom lived in the same house with the index case. During following three years, further six patients with mycobacteriosis, two Peruvians and four Japanese, were found among the employee of that factory. M. tuberculosis was cultured from the sputa obtained from seven of these eleven patients. Another patient was diagnosed as non-tuberculous mycobacteriosis. Restriction fragment length polymorphism (RFLP) analysis carried out with five strains of M. tuberculosis isolated from these patients revealed the identical RFLP pattern which is uncommon in Japan. Still more, an isolate from another patient was subjected to RFLP analysis by chance, and was found to show the same RFLP pattern. Later epidemiological study revealed that the last patient, a 53 year-old saleswoman of boxlunch, might have some contact with the index case at her booth. Though RFLP analysis was not done for the isolate from the index case, from the identity of RFLP patterns of other isolates, clinical course and epidemiological study, it is considered that six patients were certainly, and two others were probably infected from the index case.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of rifampin-resistance in pathogenic mycobacteria

The emergence of rifampin-resistant strains of pathogenic mycobacteria has threatened the usefulness of this drug in treating mycobacterial diseases. Critical to the treatment of individuals infected with resistant strains is the rapid identification of these strains directly from clinical specimens. It has been shown that resistance to rifampin in Mycobacterium tuberculosis and Mycobacterium leprae apparently involves mutations in the rpoB gene encoding the beta-subunit of the RNA polymerases of these species. DNA sequences were obtained from a 305-bp fragment of the rpoB gene from 110 rifampin-resistant and 10 rifampin-susceptible strains of M. tuberculosis from diverse geographical regions throughout the world. In 102 of 110 rifampin-resistant strains 16 mutations affecting 13 amino acids were observed. No mutations were observed in rifampin-susceptible strains. No association was found between particular mutations in the rpoB gene and drug susceptibility patterns of multidrug-resistant M. tuberculosis strains. Drug-resistant M. tuberculosis strains from the same outbreak and exhibiting the same IS6110 DNA fingerprint and drug susceptibility pattern contained the same mutation in the rpoB gene. However, mutations are not correlated with IS6110 profiling outside of epidemics. The evolution of rifampin resistance as a consequence of mutations in the rpoB gene was documented in a patient who developed rifampin resistance during the course of treatment. Rifampin-resistant strains of M. leprae, Mycobacterium avium, and Mycobacterium africanum contained mutations in the rpoB gene similar to that documented for M. tuberculosis. This information served as the basis for developing a rapid DNA diagnostic assay (PCR-heteroduplex formation) for the detection of rifampin susceptibility of M. tuberculosis.

[Application of immunosuppressants for therapy of patients with vasculitis]

Immunosuppressants are applied clinically on vasculitis. Cyclophosphamide, azathioprine, and methotrexate are used most often. Other immunosuppressants, such as bredinin, FK506, monoclonal antibody, and adhesion molecule are studied in laboratory level or in small group clinical trial. In combination therapy, immunosuppressants are used with corticosteroids, which are the first choice drug on angitis. Methotrexate is administered as intermittent manner. Since immunosuppressants have side effects including oncogenicity and immunotoxicity, clinicians have to pay much attention on clinical course of the patients with vasculitis.

[Commemorative lecture of receiving Imamura Memorial Prize. I. Studies on bacteriological diagnostic methods for mycobacteria]

Two systems, radiometric BACTEC and biphasic MB-Check, based on liquid media proved to be significantly better than the egg-based solid media for the isolation of mycobacteria from clinical specimens. The difference in the rates of isolation of mycobacteria between two groups of media was more remarkable with smear-negative specimens. The time to the detection of the Mycobacterium tuberculosis complex with MB- Check was shorter than that with the 3% Ogawa egg method but longer than that with BACTEC. The polymerase chain reaction (PCR) using oligonucleotides based on the repetitive sequence (IS986) of M. tuberculosis as a primer and the Gen-Probe Amplified Mycobacterium Tuberculosis Direct Test (MTD), which combines an M. tuberculosis rRNA amplification method with the hybridization protection assay format, were evaluated for detection of M. tuberculosis in clinical samples. Although the sensitivities of the PCR and MTD appeared to be similar to that of culture with the MB-Check system, the two methods based on nucleic acid amplification should be very useful for rapid detection of M. tuberculosis infections without the long time required for culture of M. tuberculosis. Epidemiological studies with techniques which allow differentiation of strains within M. tuberculosis groups are important for limiting the dissemination of the disease. We analyzed six groups of small outbreaks of M. tuberculosis infections by restriction fragment length polymorphism (RFLP) analysis. Five showed identical fingerprints within each group, but one which as also suspected to have a common source of infection showed different banding patterns, emphasizing that RFLP analysis using IS986 as a probe is useful in epidemiological studies of tuberculosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Detection of Mycobacterium tuberculosis in clinical specimens by polymerase chain reaction and Gen-Probe Amplified Mycobacterium Tuberculosis Direct Test

The polymerase chain reaction (PCR) using oligonucleotides based on the repetitive sequence (IS986) of Mycobacterium tuberculosis as a primer and the Gen-Probe Amplified Mycobacterium Tuberculosis Direct Test (MTD), which combines an M. tuberculosis rRNA amplification method with the hybridization protection assay format, were evaluated for detection of M. tuberculosis in clinical samples. The detection limits of these two assay systems based on nucleic acid amplification for cultured M. tuberculosis were less than 10 cells per reaction. A total of 135 sputum specimens were examined by the two assay systems. The PCR and the MTD systems for detection of M. tuberculosis gave overall positivity rates of 84.2% (32 of 38) and 91.9% (34 of 37), respectively, as compared with 71.9% (23 of 32) by smear and 96.9% (31 of 32) by culture in the liquid medium MB-Check. Procedures for sample preparation used in the two methods were different. Although the sensitivities of the PCR and MTD appeared to be similar to that of culture with the MB-Check system, the two methods based on nucleic acid amplification should be very useful for rapid detection of M. tuberculosis infections without the long time required for culture of M. tuberculosis.

[Advances in diagnostic methods for mycobacteria]

Two systems, biphasic MB-Check and radiometric BACTEC, based on liquid media proved to be significantly better than the egg-based solid media for the isolation of mycobacteria from clinical specimens. The difference in the rates of isolation of mycobacteria between two groups of media was more remarkable with smear-negative specimens. The time to the detection of the Mycobacterium tuberculosis complex with MB-Check was shorter than that with the 3% Ogawa egg method but longer than that with BACTEC. A total of 135 sputum specimens were examined by the polymerase chain reaction (PCR) using oligonucleotides based on the repetitive sequence (IS986) of M. tuberculosis as a primer. The PCR gave an overall positivity rate of 84.2%, as compared with 71.9% by smear and 96.9% by culture in the liquid medium, MB-Check. Although the sensitivity of the PCR appeared to be similar to that of culture with the MB-Check system, the PCR should be very useful for rapid detection of M. tuberculosis infections. DNA probe technology facilitates a rapid and specific identification of microorganisms. The diagnostic specificity and sensitivity of the nonradioactive Accuprobe M. tuberculosis complex and Accuprobe M. avium complex culture confirmation tests were nearly 100%. The results of the colorimetric microdilution plate hybridization test (DDH-Mycobacteria) for identification of mycobacteria were consistent with those of biochemical identification. About 90% of clinical isolates could be identified by the DDH kit. Both of these methods may contribute to the rapid diagnosis of mycobacterial infections. Epidemiological studies with techniques which allow differentiation of strains within M. tuberculosis groups are important for limiting the dissemination of the disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Restriction fragment length polymorphism analysis of epidemiologically related Mycobacterium tuberculosis isolates

Restriction fragment length polymorphism (RFLP) analysis of a large number of Japanese isolates of Mycobacterium tuberculosis, containing isolates from small outbreaks of M. tuberculosis infection, and clinical isolates of M. bovis BCG, was carried out using a DNA probe derived from the insertion sequence IS986. Clinical isolates of M. tuberculosis had a high degree of RFLP. The occurrences of the IS element varied from 1 to 19, the majority of isolates having 8 to 15 copies. Very similar fingerprints, however, were seen among strains isolated in the Kanto district. In particular, 3 strains were of the same pattern with or without an additional band. Similarity of the banding patterns of strains isolated in the same district was observed in other areas. Six groups of strains, each group arising from a suspected common source of infection, were analyzed. Of these, 5 showed identical fingerprints within each group, but one showed different fingerprints. RFLP patterns of three strains isolated from individuals with lymphadenitis developed about two months after BCG vaccination, and one strain isolated from a bladder cancer patient with BCG instillation therapy were identical to those of BCG-Tokyo which had been used for the vaccination and therapy. These results confirm that RFLP analysis using IS986 is a suitable tool for epidemiology of tuberculosis.

[Comparison of MB-Check, BACTEC, and egg-based media for recovery of mycobacteria]

The rate of recovery and time to the detection of mycobacteria from clinical specimens were measured for biphasic and radiometric liquid-based culture systems and egg-based media (3% Ogawa and Ogawa K). From the 245 sputum specimens processed, a total of 86 (35.1%) mycobacterial isolates were detected. Of these, 81 (94.2%) and 80 (93.0%) isolates were detected with the MB-Check and BACTEC systems, respectively, and 65 (75.6%) isolates were detected with the 3% Ogawa egg method. The difference in the percentages of positive cultures between the two systems based on liquid media and the 3% Ogawa egg method was significant (P < 0.01). This difference was even greater among smear-negative specimens. The detection time was shorter with the liquid-based systems. The mean times to the detection of the Mycobacterium tuberculosis complex were 19.1 days with the MB-Check system, 13.4 days with the BACTEC system, and 21.7 days with the 3% Ogawa egg method. These results indicate that both the MB-Check and the BACTEC systems, based on liquid media, are efficient for the recovery of mycobacteria.

A synthetic peptide corresponding to 86-93 of the human type I IL-1 receptor binds human recombinant IL-1 (alpha and beta) and inhibits IL-1 actions in vitro and in vivo

A synthetic peptide corresponding to 86-93 of the human type I IL-1 receptor and its analogues bound human recombinant (hr) IL-1 (alpha and beta) and inhibited dose-dependently both Con A-stimulated proliferation of mouse spleen cells and hrIL-1 beta-stimulated formation of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells in rat bone marrow cell cultures. Furthermore, hrIL-1 beta-induced mouse paw edema was dose-dependently inhibited by systemic administration (ip) of the synthetic peptide. These results suggest that one of the IL-1 binding sites of the human type I IL-1 receptor comes to the region of 86-93 and the synthetic peptide having the ability to bind hrIL-1 (alpha and beta) blocks the biological activities of exogenous hrIL-1 beta and endogenous mouse IL-1.

Results of the third immunology of leprosy/immunology of tuberculosis antimycobacterial monoclonal antibody workshop

An international workshop was sponsored by the World Health organization to screen new antimycobacterial monoclonal antibodies and to identify antibodies which could be recommended as standard reagents giving consistent results under differing assay conditions. Fifty-eight antibodies were submitted to the workshop by eight independent laboratories. Nineteen of the antibodies recognized antigens distinct from those identified in earlier workshops, defining at least 10 new protein antigens. Monoclonal antibodies characterized in the workshop provide a set of convenient reagents for further characterization of mycobacterial antigens.

Comparison of MB-Check, BACTEC, and egg-based media for recovery of mycobacteria

The rate of recovery and time to the detection of mycobacteria from clinical specimens were measured for biphasic (MB-Check; Nippon Roche Co., Ltd., Tokyo, Japan) and radiometric (BACTEC; Nippon Becton Dickinson Co., Ltd., Tokyo, Japan) liquid-based culture systems and egg-based media (3% Ogawa and Ogawa K). From the 245 sputum specimens processed, a total of 86 (35.1%) mycobacterial isolates were detected. Of these, 81 (94.2%) and 80 (93.0%) isolates were detected with the MB-Check and BACTEC systems, respectively, and 65 (75.6%) isolates were detected with the 3% Ogawa egg method. The difference in the percentages of positive cultures between the two systems based on liquid media and the 3% Ogawa egg method was significant (P less than 0.01). This difference was even greater among smear-negative specimens. The detection time was shorter with the liquid-based systems. The mean times to the detection of the Mycobacterium tuberculosis complex were 19.1 days with the MB-Check system, 13.4 days with the BACTEC system, and 21.7 days with the 3% Ogawa egg method. These results indicate that both the MB-Check and the BACTEC systems, based on liquid media, are efficient for the recovery of mycobacteria.

Cloning and expression of the gene for the Avi-3 antigen of Mycobacterium avium and mapping of its epitopes

The Avi-3 antigen, which is found only in Mycobacterium avium culture sonic extracts, is species specific and results in strong skin test activity in guinea pigs sensitized with heat-killed M. avium. Its gene was cloned by using a previously developed single-probe method and was sequenced. The gene encoded a 194-amino-acid polypeptide with a molecular weight of 21,500. A recombinant Avi-3 antigen expressed in Escherichia coli reacted with monoclonal and polyclonal antibodies raised against the native Avi-3 antigen. To identify epitopes on this protein for immunodiagnostic purposes, various parts of the Avi-3 antigen were expressed as beta-galactosidase fusion proteins, using pUR and pURS expression vectors. The clones screened by both antibody reactivity and T-cell proliferative activity defined fragments with coexisting B- and T-cell epitopes. A B-cell epitope (Asn-176 to Ala-186) and two T-cell epitopes (Glu-75 to Ile-86 and Arg-155 to Leu-164) were thus defined. The synthetic polymerized peptides of the T-cell epitopes were proven to elicit a delayed cutaneous hypersensitivity reaction in guinea pigs. This mapping method would be useful in the development of a subunit vaccine consisting of an immunodominant B-cell epitope linked to a T-cell epitope in the vicinity.

Computer-aided detection of diffuse liver disease in ultrasound images

The authors are developing an automated method of determining measures of texture in liver ultrasound images to improve the accuracy of diagnosis of diffuse liver abnormalities. In each digitized image, the background trend of pixel values is estimated to isolate the underlying pattern of liver texture. After correcting for background trend, the root mean square (RMS) variation and the first moment of the power spectrum are calculated; these measures have been applied successfully to texture analysis of digital chest radiographs. Background trend-corrected measurements detected statistically significant differences in digitized ultrasound images of 11 normal and 11 abnormal livers. Without correction for background trend, the measures are unable to distinguish normal from abnormal liver texture. The authors also investigated the effect on the texture measures of varying several ultrasound imaging parameters in normal patients and in an ultrasound phantom.

[Study on recombinant BCG]

For the purpose to establish the system to express foreign antigen from Mycobacterium bovis BCG. We have cloned, sequenced and expressed genes for secreting proteins, alpha antigen, MPB64, MPB57 and MPB70 from M. bovis BCG. The upstreams and structural genes were characterized. The gene for alpha antigen of Mycobacterium kansasii was also characterized. The gene for alpha antigen of M. kansasii (k-alpha) was chosen for the further study at first. This gene was fused with shuttle plasmid PIJ666-PAL5000 obtained from T. Kisser and transfected to M. bovis BCG (Tokyo). Transformant was obtained by a selection with kanamycin. It was able to secrete k-alpha antigen. DNA-containing a B-cell epitope (Glu-12-Leu-Asp-Arg-Trp-Glu-Lys-Ile-19) of human immunodeficiency virus type 1 P17 gag was fused to this vector at C terminal of k-alpha. Using this vector, we have succeeded to express foreign antigen in M. bovis BCG. The products were analyzed in one or two dimensional electro-phoresis. The results thus obtained will be reported elsewhere.

Potential usefulness of an artificial neural network for differential diagnosis of interstitial lung diseases: pilot study

An artificial neural network approach was applied to the differential diagnosis of interstitial lung diseases. The neural network was designed to distinguish between nine types of interstitial lung diseases on the basis of 20 items of clinical and radiographic information. A data base for training and testing the neural network was created with 10 hypothetical cases for each of the nine diseases. The performance of the neural network was evaluated by means of receiver operating characteristic analysis. The decision performance of the neural network was high; it was comparable to that of chest radiologists and superior to that of senior radiology residents. The preliminary results strongly suggest that the neural network approach has potential utility in the computer-aided differential diagnosis of interstitial lung diseases.