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[Study of detailed conditions in DNA probe test by use of Gen-Probe Rapid Diagnostic System for identification of Mycobacterium avium complex and Mycobacterium tuberculosis complex].

In order to improve feasibility of technical procedures in Gen Probe Rapid Diagnostic System (Gen Probe Inc., San Diego, CA, U.S.A.) for identification of Mycobacterium avium complex (MAC) and M. tuberculosis complex (MTC), we studied several test conditions in the DNA probe testing, such as stability of test bacterial suspension, optimal duration of bacterial cultivation, the number of organisms in test bacterial suspension required for accurate determination, and so on. With respect to concentration of organisms (MAC and MTC) in test bacterial suspension (0.1ml), we found that 5-fold dilution as well as 5-fold condensation of the standard bacterial suspension (McFarland No.1) gave substantially the same result as in the case where bacterial suspension at the standard concentration was used. This indicates that the test bacterial suspensions (0.1ml) containing either 1.5 X 10(7)-5 X 10(8) of MAC or 3 X 10(5)-8 X 10(6) of MTC are available for the DNA probe testing. Test bacterial suspension at McFarland No.1 prepared from fresh cultures (3-4 week-old) could be stored either at -80, -20 or 4 degrees C at least for 17 weeks without significant loss of reactivity to M. avium, M. intracellulare and MTC DNA probes. In this case, stability of DNA probe-reactivity was preserved in the following order: MTC, M. avium and M. intracellulare. Concerning the age of bacterial cultures, at least 16-week-old cultures of MAC and MTC after initial appearance of cell growth on 1% Ogawa's egg media were sufficiently reactive to either MAC or MTC DNA probe. In this case, MTC showed most stable reactivity during the course of long-term cultivation.(ABSTRACT TRUNCATED AT 250 WORDS)

DNA Probes↗

Inhibition of adherence of Mycobacterium avium complex and Mycobacterium tuberculosis to fibronectin on the respiratory mucosa.

Mycobacterium species adhere to the respiratory mucosa via mucus and fibronectin of extracellular matrix exposed by damaged epithelium. We have investigated whether inhibiting adherence to fibronectin influences subsequent infection of human respiratory tissue by Mycobacterium avium complex and Mycobacterium tuberculosis. Human respiratory tissue was pretreated with mycobacterial fibronectin attachment proteins prior to infection with M. avium complex and M. tuberculosis and the number of recoverable bacteria over time was compared to untreated controls. Inhibition significantly reduced recovery of M. avium complex at 15min (P= 0.02), 7days (P = 0.04), and 14 days (P= 0.03); whereas recovery of M. tuberculosis was only reduced at 15 min (P = 0.01) and not at later timepoints. We conclude that M. avium complex and M. tuberculosis infection of the mucosa proceeds by different mechanisms, since M. tuberculosis infection is independent of fibronectin adherence.

Adhesins, Bacterial↗

Genetic diversity of the dnaJ gene in the Mycobacterium avium complex.

The Mycobacterium avium complex (MAC) is associated with various diseases in humans as a zoonosis. The dnaJ gene was partially sequenced in Schaefer's 28 reference strains of MAC, 14 human MAC isolates and 22 veterinary isolates. From substitutions affecting 21-32 nucleotides, all strains could be classified into 14 groups. Most nucleotide substitutions did not alter amino acid sequences. Approximately 8 % genetic diversity was seen in these strains, which divided into two clusters: cluster I (0.8 % genetic diversity), comprising the reference strain serotypes 1-6, 8-11 and 21 and all isolates; and cluster II (7 % genetic diversity), comprising the remaining reference strains. Analysis of the dnaJ gene in MAC may be useful in epidemiological studies.

Animals↗

Mechanism of Mycobacterium avium complex pathogenesis.

Mycobacterium avium complex (MAC) group of microorganisms are the most common opportunistic bacterial pathogens causing disseminated disease in HIV infected patients. These microorganisms are ubiquitous in nature, and are acquired by respiratory and oral routes. Pathogenesis of MAC depends on the ability of the organisms to colonize intestinal/respiratory mucosa, penetrate the protective barriers and resist intracellular killing by macrophages. Transient and reversible variation of colony morphology is one the characteristic feature of MAC that plays a significant role in the virulence and pathogenesis of these microorganisms. Isogenic colony variants of MAC differ in their virulence, susceptibility to antibiotics, stimulation of oxygen radicals and cytokines. The virulent smooth transparent colony variants are more frequently isolated from AIDS patients, more efficient in mucosal colonization, and adhere more efficiently to epithelial cells as compared to the less virulent smooth opaque variants. However, both the isogenic variants bind to the mucosal epithelial cells through the same multiple receptors. In addition, both the isogenic variants of MAC also bind to intestinal mucus through a single receptor. Study of the interaction of MAC with the host cells and characterization of MAC adhesins and host cell receptors facilitates the elucidation of the mechanisms involved in MAC pathogenesis.

Animals↗

[Promotion of phagocytosis and prevention of phagosome-lysosome (P-L) fusion in human peripheral blood monocytes by serotype specific glycopeptidolipid (GPL) antigen of Mycobacterium avium complex (MAC)].

Mycobacterium avium complex (MAC) is one of the most important opportunistic pathogens co-infected with HIV (AIDS) and a typical intracellular parasitic bacteria similar to M. tuberculosis. It is also noticed that M. avium infection causes immunosuppression especially in the cellular immunity of host animals, and specific serotype-subspecies such as sero-2, -4 or -8 can be isolated frequently in human infection. Furthermore, the prognosis after infection differs by the serotypes and serotype-4 shows heavy infection in general, while serotype-16 shows rapid improvement. Therefore, we have been interested in the immunomodifying activity of surface glycopeptidolipid (GPL) antigen. However, to date, no information has been available on the virulence factor of MAC related directly with intracellular bactericidal activity. Recently, we have tested the effect of various GPLs purified form MAC complex on phagocytic processes of human peripheral blood monocytes (PBMC). We have used GPL-coated heat-killed staphylococcal cells to be phagocytosed by PBMC, and phagosome-lysosome (P-L) fusion was estimated by the acridine orange staining of fused vesicles including bacteria. It was revealed that the serotype-4, -12 and -17 GPLs showed strong phagocytosis promotion and marked inhibition of P-L fusion, while serotype-9, -13, -16 and -19 GPLs showed neither promotion of phagocytosis, nor inhibition of P-L fusion in phagocytic cells. Serotype-5, -7, -8 and -10 GPLs showed stimulation of both phagocytosis and P-L fusion, concomitantly. These effects may be due to unknown interaction between specific carbohydrate chain of MAC and phagocytic cell membranes, and serotype-4, -12 and -17 GPLs may be one of the possible virulence factors in MAC.

Antigens, Bacterial↗

Use of potassium tellurite for rapid-drug susceptibility testing of Mycobacterium avium complex.

BACKGROUND: Mycobacterium avium complex (MAC) is a major cause of infection in immunocompromised patients. MAC possesses an enzyme that reduces potassium tellurite in less than 3 days and results in formation of a black precipitate. The objective of this study was to determine whether reduction of potassium tellurite by mycobacteria can be used as a means of testing the susceptibility of MAC to clarithromycin. METHODS: Minimum inhibitory concentrations (MICs) for 104 clinical isolates of MAC were determined by the tellurite method and compared with those tested by a recommended microdilution method. Microdilution breakpoints were used for interpretation of susceptibility. MIC of less than 8 microg/mL was considered as susceptible, and MIC of greater than or equal to 8 microg/mL was resistant. RESULTS: There was agreement within a 2-fold dilution between MICs for 89% of isolates. Of the 53 isolates that had discrepant MICs by the two methods, 70% had higher MICs by the tellurite method. When the MICs were classified into interpretive categories, there was 100% agreement by the two methods. The MIC tested by the tellurite method was available within 5 days. CONCLUSIONS: These data suggest that use of potassium tellurite is a more rapid, reliable, and inexpensive method of testing the susceptibility of MAC to clarithromycin.

Anti-Bacterial Agents↗

Modification of results of drug susceptibility tests by coexistence of Mycobacterium avium complex with Mycobacterium tuberculosis in a sputum sample: case report and experimental considerations.

We report on a patient whose sputum contained both Mycobacterium tuberculosis and Mycobacterium avium complex (MAC). The MAC failed to be detected by the PCR-based AMPLICOR test. The unrecognized coexistence of MAC in the sample modified the results of drug susceptibility tests. Experiments revealed that the presence of both M. tuberculosis and MAC was not detected by the AMPLICOR test under certain conditions.

Humans↗

Sporotrichoid cutaneous Mycobacterium avium complex infection.

Mycobacterium avium complex, a common opportunistic pathogen among patients with AIDS, usually manifests as disseminated disease involving the lung, lymph nodes, and gastrointestinal tract. Primary cutaneous infections with M avium complex are extremely rare, and most cutaneous lesions are caused by dissemination. Cutaneous manifestations thus far reported include scaling plaques, crusted ulcers, ecthyma-like lesions, verrucous ulcers, inflammatory nodules, panniculitis, pustular lesions, and draining sinuses. Localized skin involvement resembling sporotrichosis is unusual and to our knowledge has been reported only once in the English-language literature. We describe an additional case of primary cutaneous M avium complex infection manifesting as sporotrichosis-like lesions on a patient with AIDS.

AIDS-Related Opportunistic Infections↗

Host defense against Mycobacterium-avium complex.

Mycobacterium-avium complex (MAC) is an intracellular pathogen and the most common cause of widely disseminated bacterial infection in patients with the acquired immunodeficiency syndrome (AIDS). MAC is infrequently seen in other immunocompromised adults, suggesting that the host defense defect allowing for MAC infection is relatively unique for AIDS. A system was developed for studying the immune response to MAC infection, utilizing MAC isolated from patients with AIDS and monocytes from normal controls and patients with AIDS. Phagocytosis, superoxide anion (SOA) production, and killing were measured. Monocytes from normal controls and AIDS patients were identical with respect to phagocytosis of MAC. In contrast, baseline SOA production was elevated in monocytes from patients compared to normal monocytes and was minimally augmented in response to either phorbol myristate acetate or MAC. Fourteen-day kinetic studies revealed in patients and controls a biphasic pattern with 50-99% killing of AIDS-derived MAC initially, followed always by a rapid outgrowth of surviving bacilli. Despite a modest enhancement of MAC killing by normal but not patients' monocytes pretreated with either recombinant interferon-gamma or recombinant tumor necrosis factor-alpha, outgrowth of MAC was always observed in both, typically faster in patients than in controls. Even monocytes in the presence of lymphocytes stimulated with interleukin-2 did not demonstrate enhanced MAC killing. In contrast, high-titered anti-MAC immune serum derived from a patient with polymyositis and disseminated MAC significantly enhanced the killing of MAC by monocytes from both AIDS patients and healthy controls and prevented their outgrowth. These findings suggest that the host defense defect allowing for MAC infection appears not to reside in the monocyte and that the in vitro lymphocyte functions examined in this study do not appear to play a major role. What role specific antibody plays in vivo in preventing disseminated MAC is uncertain, but the lack of such antibody may help explain the propensity for AIDS patients to develop systemic infection.

Adjuvants, Immunologic↗

Mycobacterium avium complex and Mycobacterium tuberculosis in patients infected with the human immunodeficiency virus.

Primary care physicians play an important role in identifying and treating bacterial infections in adults infected with the human immunodeficiency virus (HIV). Mycobacterium avium complex and Mycobacterium tuberculosis are pathogens that can cause systemic or local infection in these patients. We review the epidemiology, pathogenesis, clinical presentation, and principles of treatment for these two mycobacterial pathogens. Because M tuberculosis disease is preventable and curable and yet communicable, physicians should maintain a high degree of suspicion for tuberculosis in HIV-infected adults. In comparison, the goal of treating M avium complex in patients with advanced HIV disease is to reduce constitutional symptoms and improve survival.

Acquired Immunodeficiency Syndrome↗

[Geographical distribution of Mycobacterium avium complex in environment and serovars of Mycobacterium avium complex isolates from patients with and without AIDS].

Mycobacterium avium complex (MAC) organisms have been isolated from water and soil. It is now generally accepted that environmental sources, especially natural waters, are the reservoirs for most human infections caused by MAC. Previously, we reported that M. avium and M. intracellular were distributed predominantly in the eastern and western part of Japan, respectively. To clarify the factor(s) of the difference, the following experiment was undertaken. MAC was isolated from soil samples collected in Tokai, Kinki and Chugoku districts, by the method of Ichiyama et al. MAC isolates were identified by AccuProbe Confirmation and Identification tests, together with some conventional tests. Seven (11.7%) of 60 isolates were identified as M. avium, twenty (33%) as M. intracellulaer and 33 (55%) as MAC-like organisms. Therefore, it was not found that the difference in the geographical distribution between soil MAC and disease-associated MAC. MAC-like strains possess MAC-specific alpha antigen, and biological and biochemical features of MAC. They reacted with the AccuProbe MAC but not with the AccuProbe M. avium and M. intracellulare. Sequencing analysis of 16s RNA gene implies that MAC-like strains show an intermediate sequence pattern of M. avium and M. intracellulare. HPLC patterns of these strains were compatible with those of MAC. It is known that the major serovars of MAC isolates from patients with or without AIDS are different. Serological aspects in this respect are not yet elucidated well in Japan. The major serovars of MAC from patients with AIDS are 4 and 8 in the USA and Australia, 6 and 4 in Sweden, and 8/21 and 8 in Germany. On the other hand, the major serovars of MAC from patients without AIDS are 8 and 16 (15) in the USA and 6 and 1 in Sweden. According to out recent study the major serovars of MAC from non-AIDS patients are 1 and 8 in the eastern part and 16 and 14 in the western part of Japan. In the present study, 38 MAC isolates from sputum, stool and blood and AIDS patients were identified. All of the isolates were identified as M. avium. Serovars of 15 strains were 4 (4 strains), 8 (3 strains), 9 (3 strains), 3 (2 strains), Darkin (2 strains) and 1 (1 strain). Therefore, it seems that the major serovars of the Japanese MAC strains from AIDS patients are similar to those of the American MAC strains from such patients.

Acquired Immunodeficiency Syndrome↗

The recovery of Mycobacterium avium complex and Mycobacterium tuberculosis from blood specimens of AIDS patients using the nonradiometric BACTEC NR 660 medium.

The ability of the nonradiometric BACTEC NR 660 aerobic 6A blood culture medium to support mycobacterial growth was investigated. During a 19-month period blood cultures from 140 AIDS patients were sent to the microbiology laboratory. After the cultures were incubated for seven days, aliquots of medium from the vials were centrifuged, sediments examined microscopically for mycobacteria, and cultured to mycobacterial media. Seventy-one AIDS patients (51%) had at least one blood culture positive for mycobacteria. There was a significant difference in the percent of female AIDS patients positive for mycobacteria compared to male patients (72% vs. 44%, P less than 0.01). Forty-four percent of all subsequently positive cultures were detected by an acid fast stain of the specimen sediment. Subcultures from the BACTEC 6A suspensions were positive on mycobacterial media at one-seven weeks (mean three weeks) after planting. Sixty-nine of the isolates were Mycobacterium avium complex, while two were Mycobacterium tuberculosis. Some bacteremias with M. tuberculosis may have been undetected because growth experiments with a reference strain showed that, in contrast to M. avium complex, M. tuberculosis did not increase in concentration in 6A medium.

Acquired Immunodeficiency Syndrome↗

[Extracellular and intracellular activity of sparfloxacin against Mycobacterium avium complex and Mycobacterium xenopi].

Activity of the new fluoroquinolone sparfloxacin against 30 strains of M. avium complex and 25 strains of M. xenopi was tested in vitro. Sparfloxacin was used alone (determination of MICs and MBCs) and in combination with ethambutol and rifabutin. Synergy studies with determination of the FIC and FBC indices showed that the sparfloxacin-ethambutol combination was synergistic against 10 M. avium complex strains and 12 M. xenopi strains. With the three-drug combination (sparfloxacin-ethambutol-rifabutin), synergy was found against 12 M. avium and 14 M. xenopi strains. Studies of intracellular bacteria showed that the decrease in viable bacteria with the three-drug combination was 1 log for M. avium and 2 log for M. xenopi.

Acquired Immunodeficiency Syndrome↗

[Nontuberculous mycobacteriosis; the present status and in the future. Mechanisms of host resistance to Mycobacterium avium complex and Mycobacterium tuberculosis infection].

In order to know profiles of the antimicrobial action of some microbicidal effector molecules against Mycobacterium avium complex (MAC) and M. tuberculosis (MTB), profiles of collaborating effects among reactive nitrogen intermediates (RNI), free fatty acids (FFA), and reactive oxygen intermediates (ROI) were studied, RNI and FFA exerted synergistic effects in killing MAC and MTB, while the combination of ROI (H2O2-mediated halogenation system) with FFA conversely caused antagonism. The combination of RNI with ROI displayed additive effects in killing MTB, whereas the same combination showed antagonistic effects against MAC. Murine peritoneal macrophages (M phi s) produced and/or released these three antimicrobial effectors in the order ROI, FFA, and RNI in response to cellular stimulation induced by their contact with MAC or MTB organisms. These findings indicate that the collaborating effect of RNI with FFA is crucial for M phi-mediated intracellular killing of MAC and MTB. Secondly, we examined the modes of bacterial growth of MAC and MTB in murine peritoneal M phi s and A-549 type II alveolar epithelial cell line. The growth rate of these organisms was much larger in A-549 cells than in M phi s. In addition, the growth rate of high-virulence MAC (N-260 strain) was significantly larger than that of low-virulence MAC (N-444 strain), when they were residing in M phi or A-549 cells. Although a high virulence MTB (strain Kurono) also showed much more rapid growth in M phi s than did low-virulence MTB (strain H37Ra), such a phenomenon was not observed for their intracellular growth in A-549 cells. MTB exhibited strong cytotoxic effects against M phi s but not against A-549 cells when resided in these cells. On the other hand, MAC organisms did not cause cytotoxicity even in M phi s. Although MAC and MTB infections caused significant increase in RNI production by M phi s but not by A-549 cells, there was no significant relationship between the degree of M phi RNI production by a given mycobacterial organism and its virulence. These findings indicate some important roles of type II alveolar epithelial cells as a target cell for primary invasion and transient growth of mycobacterial organisms in the host lungs.

Animals↗

Comparative genomic hybridizations reveal genetic regions within the Mycobacterium avium complex that are divergent from Mycobacterium avium subsp. paratuberculosis isolates.

Mycobacterium avium subsp. paratuberculosis is genetically similar to other members of the Mycobacterium avium complex (MAC), some of which are nonpathogenic and widespread in the environment. We have utilized an M. avium subsp. paratuberculosis whole-genome microarray representing over 95% of the predicted coding sequences to examine the genetic conservation among 10 M. avium subsp. paratuberculosis isolates, two isolates each of Mycobacterium avium subsp. silvaticum and Mycobacterium avium subsp. avium, and a single isolate each of both Mycobacterium intracellulare and Mycobacterium smegmatis. Genomic DNA from each isolate was competitively hybridized with DNA from M. avium subsp. paratuberculosis K10, and open reading frames (ORFs) were classified as present, divergent, or intermediate. None of the M. avium subsp. paratuberculosis isolates had ORFs classified as divergent. The two M. avium subsp. avium isolates had 210 and 135 divergent ORFs, while the two M. avium subsp. silvaticum isolates examined had 77 and 103 divergent ORFs. Similarly, 130 divergent ORFs were identified in M. intracellulare. A set of 97 ORFs were classified as divergent or intermediate in all of the nonparatuberculosis MAC isolates tested. Many of these ORFs are clustered together on the genome in regions with relatively low average GC content compared with the entire genome and contain mobile genetic elements. One of these regions of sequence divergence contained genes homologous to a mammalian cell entry (mce) operon. Our results indicate that closely related MAC mycobacteria can be distinguished from M. avium subsp. paratuberculosis by multiple clusters of divergent ORFs.

Conserved Sequence↗

In vitro susceptibility of Mycobacterium avium complex and Mycobacterium tuberculosis strains to a spiro-piperidyl rifamycin.

The spiro-piperidyl rifamycins are newly synthesized rifamycin S compounds. One of these compounds, LM 427, was tested in vitro against strains of the Mycobacterium avium complex and strains of M. tuberculosis; LM 427 inhibited 81.3% of 155 strains of the M. avium complex tested at a concentration of 1.0 microgram/ml compared with 5.8% inhibited by the same concentration of rifampin. Twenty-nine strains were resistant to both LM 427 and rifampin at 1.0 microgram/ml. Further testing of these 29 strains showed LM 427 inhibitory for all but 5 strains at 2.0 micrograms/ml and inhibitory for all but 1 at 5.0 micrograms/ml. Rifampin, on the other hand, inhibited none at 2.0 micrograms/ml and 11 strains at 5.0 micrograms/ml. The in vitro activity of LM 427 was also compared with rifampin by testing both compounds against M. tuberculosis at 1.0 microgram/ml. This comparison showed that all strains susceptible to rifampin were also susceptible to LM 427. However, 16 strains were susceptible to LM 427 and resistant to rifampin. The inhibition of drug-resistant mycobacterial species that cause pulmonary disease makes this compound an important consideration for future clinical studies.

Drug Resistance, Microbial↗

Characteristics of immunosuppressive macrophages induced in host spleen cells by Mycobacterium avium complex and Mycobacterium tuberculosis infections in mice.

The profile of generation and characteristics of immunosuppressive macrophages (M phi s), which suppress the ConA-mitogenic response of spleen cells (SPCs), in host CBA/JN mice during the course of Mycobacterium avium complex (MAC) and M. tuberculosis (MT) infections were investigated. In both infections, a marked reduction in ConA mitogenic response of splenic T cells was seen around 2 weeks after infection, and this was accompanied by generation of potent immunosuppressive M phi s in the SPCs of infected mice. The suppressive activity was much stronger in MT-infected mice than in MAC-infected ones. In both infections, the large part of the suppressive M phi s exhibited suppressor activity that depended on the arachidonic acid cascade, particularly mediated by prostaglandins (PGs), and the remainder showed the suppressor action independent from PGs. The unique finding of this study is that the generation of IL-2 reactive T cell populations in SPCs in response to ConA signal was markedly inhibited by the MAC- and MT-induced immunosuppressive M phi s, whereas the suppressive M phi s failed to reduce the IL-2-producing ability of splenic T cells. In any case, the present results indicate a close similarity in immunosuppressive M phi s induced by MAC and MT infections.

Animals↗

Relationship between clinical efficacy of treatment of pulmonary Mycobacterium avium complex disease and drug-sensitivity testing of Mycobacterium avium complex isolates.

We prospectively investigated the relationship between the clinical efficacy of treatment of pulmonary Mycobacterium avium complex (MAC) disease and drug-sensitivity testing of MAC isolates for antituberculous drugs, new quinolone antibiotics, and clarithromycin (CAM). Fifty-two patients who satisfied the diagnostic criteria of the American Thoracic Society (ATS) and who received treatment between April 1998 and December 2005, using combined therapy of rifampicin (RFP), ethambutol (EB), streptomycin (SM), and CAM, were enrolled in this study. The causative microorganisms isolated were Mycobacterium avium in 30 patients and M. intracellulare in 22 patients. Although separation of the two strains showed drug sensitivity testing to have slightly better minimal inhibitory concentrations (MIC) for M. intracellulare than for M. avium, there were no significant differences in the sputum eradication rate or clinical improvement between the two strains. The MICs of various antibiotics for the isolated MAC strains were as follows: RFP, 0.125-8 microg/ml; CAM, 0.25-16 microg/ml; SM, 2-128< or =microg/ml; EB, 128< or = microg/ml; levofloxacin (LVFX), 1-32 microg/ml; sparfloxacin (SPFX), 0.5-16 microg/ml; and gatifloxacin (GFLX), 0.25-8 microg/ml. The isolated MAC strains showed the same excellent drug sensitivity test results for RFP, new quinolones, and CAM, but they showed resistant drug-sensitivity results for EB and SM. Regarding the relationship between clinical efficacy and the MICs of RFP, EB, CAM, and SM, there was a good relationship only for CAM. Although the ATS has not yet recommended routine drug susceptibility testing of CAM, we believe that drug susceptibility testing of CAM should be performed before the initial treatment is undertaken for pulmonary MAC disease.

Anti-Bacterial Agents↗