Mycobacterium xenopi pulmonary infection in two renal transplant recipients under sirolimus therapy.

Opportunistic infection is a major threat to immunocompromised patients. However, infection due to Mycobacterium xenopi is rare in renal transplant recipients. We report two new cases of M. xenopi pulmonary infection (one case of interstitial pneumopathy and one of a pulmonary nodule) in renal transplant recipients, detected in the same center at an interval of a few months. Both patients were on an immunosuppressive regimen including a recent switch to sirolimus. Sirolimus is a new immunosuppressive drug already known to be responsible for interstitial pneumonitis. It also inhibits interleukin-12-induced proliferation of activated T lymphocytes, which is critical for the development of the cell-mediated immunity that protects against mycobacteria. These two case reports suggest that sirolimus therapy may lead to an impairment of the immune response against intracellular pathogens such as M. xenopi.

Pulmonary resection for Mycobacterium xenopi pulmonary infection.

BACKGROUND: Results of medical therapy for Mycobacterium xenopi pulmonary infection remain unreliable. Pulmonary resection may be beneficial to patients whose disease is localized and who can tolerate a resectional operation. METHODS: Eighteen patients underwent pulmonary resection between 1991 and 2000: 14 men and 4 women, with a mean age of 50 +/- 12 years (range 27 to 68 years). Indications for operation were either therapeutic (n = 9) or diagnostic (n = 9). Four patients received antimycobacterial chemotherapy before their operation and 2 patients were HIV positive. RESULTS: Therapeutic procedures included completion pneumonectomy (n = 1), lobectomy (n = 6), segmentectomy (n = 1), and bilateral wedge resection (n = 1). Diagnostic procedures included lobectomy (n = 1) and wedge resection (n = 8). Complete resection could be achieved in 15 patients (83%). There was no in-hospital mortality. Postoperative complications included prolonged air leak (5 of 18 patients, 27.7%) and pleural effusion requiring insertion of a new chest tube (3 of 18 patients, 16.6%). Mean hospital stay was 14 +/- 8 days. Follow-up was 100% complete. Eleven patients received antimycobacterial chemotherapy for 4 to 24 months, postoperatively. Late mortality was 11% and was unrelated to progression of mycobacterial disease. After the operation, the sputum remained positive in only 2 patients (11%) with incomplete resections. Fourteen patients were asymptomatic with no relapse at a mean follow-up of 38 +/- 22 months (range 85 to 13 months). CONCLUSIONS: Resection represents an important adjunct to chemotherapy for the treatment of M. xenopi pulmonary disease. In the setting of localized nodular or cavitary disease, failure to respond to medical therapy, relapse after treatment discontinuation, coexistent aspergilloma or polymicrobial contamination, or patient intolerance of medical therapy, pulmonary resection can be undertaken with acceptable morbidity and mortality.

Molecular fingerprinting of Mycobacterium tuberculosis and risk factors for tuberculosis transmission in Paris, France, and surrounding area.

Forty-three percent of the tuberculosis cases reported in France are from the Ile de France region. The incidence of tuberculosis in this region is 33 cases per 100,000 inhabitants, twice the national average. A restriction fragment length polymorphism (RFLP) analysis was performed with clinical isolates of Mycobacterium tuberculosis isolated during 1995 in 10 hospitals in Paris and surrounding areas to detect tuberculosis transmission and define the factors associated with clustering in this population. The molecular markers used were the insertion sequence IS6110 and the direct repeat (DR) sequence. Social, demographic, and clinical data were collected from the patients' medical files. Ten patients with isolates with a single copy of IS6110 were excluded from further analysis. Twenty-four patients with false-positive cultures due to laboratory contamination (based on RFLP analysis with IS6110 and examination of patient data) were also excluded. The study was then conducted with 272 strains isolated from 272 patients. Further fingerprinting was performed by using the DR element with strains with patterns by RFLP analysis with IS6110 that differed by one band only and strains with identical patterns by RFLP analysis with IS6110 and with low numbers of copies of IS6110. The combined use of both markers identified unique patterns for 177 strains and clustered 95 (35.7%) strains in 26 groups, each containing isolates from 2 to 12 patients. The clustering was strongly associated with homelessness and the male sex. It was not associated with age, birth in a foreign country, human immunodeficiency virus positivity, or residence in hostels or prison. Isolates from homeless people were often included in large clusters, and homeless people could be the source of tuberculosis transmission for more than 50% of the clustered patients. These results suggest that homeless people play a key role in the spread of M. tuberculosis in the community and that poor socioeconomic conditions are the main risk factors associated with active tuberculosis transmission.

The phagosomal environment protects virulent Mycobacterium avium from killing and destruction by clarithromycin.

Murine bone marrow-derived macrophages (Mphis) infected with virulent strains of Mycobacterium avium (TMC 724 and a human clinical isolate) or with an avirulent opaque variant that spontaneously dissociates from the virulent human clinical isolate were subjected to a prolonged and continuous treatment with clarithromycin added at the MIC. The efficiency of this antibiotic in terms of inhibition of bacterial growth and bacterial degradation was evaluated during a 21-day treatment period. Growth was assessed by determination of CFU of intracellular bacteria and by a quantitative ultrastructural analysis which allowed us also to determine the extent of bacterial degradation. A similar treatment was applied to the same strains growing in liquid medium. Our data show that in liquid medium, clarithromycin caused a 90% decrease in CFU within 7 days of treatment. When applied to Mphis infected with virulent M. avium, clarithromycin immediately arrested bacterial growth but was unable to fully kill and degrade intracellularly growing virulent bacteria. After 21 days of treatment, 25% of intracellular bacteria were still morphologically intact. These bacteria resumed growth upon removal of the antibiotic, with a normal replication rate. These bacteria had not become more resistant to the drug, since the MIC was unchanged as compared to the one determined for the initial stock used to infect Mphis. Our data therefore suggest that the intraphagosomal environment protects bacteria from degradation. We propose that the inability of the drug to completely destroy bacteria is the result of a limited accessibility of the drug due to prevention of fusions between the immature phagosomes in which virulent bacteria reside and lysosomes in which clarithromycin accumulates. In accord with our proposal, we show that the avirulent opaque variant, which does not prevent phagosome-lysosome fusions (unpublished data), is finally destroyed by clarithromycin even within the phagosomal environment.

Evaluation of tuberculosis transmission in a community by 1 year of systematic typing of Mycobacterium tuberculosis clinical isolates.

Interhuman transmission of Mycobacterium tuberculosis was investigated by using molecular typing, including restriction fragment length polymorphism with probes IS6110, DR (direct repeat) and PGRS (polymorphic GC-rich sequence) and a PCR method using the inverted repeat sequences of IS6110 as primers. From 105 patients hospitalized for tuberculosis during a 1-year survey in three hospitals in Paris, France, 111 isolates were collected and analyzed. Eighty-eight patients were infected with genetically different isolates, demonstrating the clonal heterogeneity of M. tuberculosis in these patients originating from various geographical areas. Fourteen patients were infected by strains clustered with identical fingerprints. An epidemiological relatedness was demonstrated for isolates from only seven of these patients. Thus, the typing of isolates from all tuberculous patients in hospitals during 1 year allows the detection of transmission in the general community. This would improve the case findings, thereby further improving the detection of outbreaks.

Value of liver biopsy for the rapid diagnosis of infection in human immunodeficiency virus-infected patients who have unexplained fever and elevated serum levels of alkaline phosphatase or gamma-glutamyl transferase.

We prospectively determined the value of liver biopsy for microbiological diagnosis of infection in patients infected with the human immunodeficiency virus (HIV) who had unexplained fever and whose serum levels of alkaline phosphatase or gamma-glutamyl transferase were at least 1.5 times the upper limit of normal. From December 1989 to December 1991, 108 HIV-infected patients were referred to the Liver Unit at Hôpital Laënnec (Paris) with liver abnormalities related to viral hepatitis (generally chronic), AIDS-related sclerosing cholangitis, or nonspecific lesions (detected on histologic examination). Twenty-four patients had unexplained fever and increased levels of alkaline phosphatase or gamma-glutamyl transferase, and none had evidence of hepatobiliary disease. All 24 patients had undergone routine microbiological tests to determine the cause of their chronic fever. The results of all microbiological tests were negative. We performed liver biopsies for these 24 patients and examined the specimens by means of standard direct microbiological techniques; in addition, the specimens were cultured, the specimens were analyzed by standard histopathologic methods, and specific histologic studies for fungi, mycobacteria, and viruses were performed. A microbiological diagnosis was made in 13 (54%) of the 24 cases within 12 hours to 3 days of the liver biopsy. In conclusion, liver biopsy is a powerful diagnostic tool for rapid diagnosis of infection in HIV-infected patients who have unexplained fever and abnormal liver function test results.

Bacillus Calmette-Guérin infection after vaccination of human immunodeficiency virus-infected children.

The use of Mycobacterium bovis/Bacillus Calmette-Guérin (BCG) to vaccinate against tuberculosis remains controversial. The development of tuberculosis in human immunodeficiency virus (HIV)-infected children demands specific evaluation of the risk/benefit ratio of BCG vaccination in this situation. In our institution 9 of 68 HIV-infected children vaccinated with BCG before the diagnosis of HIV infection was suspected developed vaccine-related complications: 7 of these children had a large satellite adenopathy with or without skin fistulae, whereas the other 2 had disseminated BCG infection beyond the satellite ganglion (involvement of the spleen and mesenteric and mediastinal lymph nodes in one case and the liver and lungs in the other). The children were vaccinated soon after birth; no particular problems were observed at that time, but complications appeared 3 to 35 months later. All but one of these children had a rapidly progressive form of HIV disease. The possibility of delayed local or disseminated BCG infection must be considered in analysis of the risk/benefit ratio of vaccination of HIV-infected children. The prognosis of HIV infection must be taken into account, even if the child is asymptomatic when vaccination is being considered.

Implication of phagosome-lysosome fusion in restriction of Mycobacterium avium growth in bone marrow macrophages from genetically resistant mice.

The ability of the host to resist infection to a variety of intracellular pathogens, including mycobacteria, is strongly dependent upon the expression of the Bcg gene. Mouse strains which express the resistance phenotype (Bcgr) restrict bacterial growth, whereas susceptible strains (Bcgs) allow bacterial growth. Expression of the Bcg allele is known to influence the priming of host macrophages (M phi s) for bactericidal function. In the present work, bone marrow-derived M phi s from congenic BALB/c (Bcgs) and C.D2 (BALB/c.Bcgr) mice were infected with the virulent strain Mycobacterium avium TMC 724 to define the mechanism involved in growth restriction of M. avium. By combining CFU measurements and ultrastructural analyses, we show that growth of this bacterium is restricted in marrow M phi s from resistant mice. Using acid phosphatase as a lysosomal marker, we provide evidence that the hydrolytic activity of M phi s, as measured by the capacity of lysosomes to fuse with and transfer active hydrolytic enzymes to phagosomes in which M. avium resides, is an expression of the Bcg gene and that this phenomenon is a key antibacterial activity responsible for growth restriction of M. avium: (i) the percentage of phagosome-lysosome fusions was twice as high in Bcgr M phi s as in Bcgs M phi s, and (ii) the percentage of intact viable bacteria residing in acid phosphatase-negative phagosomes was twice as low in Bcgr M phi s as in the Bcgs counterparts. These differences are not due to a lower activity of the enzyme in Bcgr M phi s. The mechanism by which the Bcg gene exerts control over the phagolysosomal fusion is discussed.

Intramacrophage growth of Mycobacterium avium during infection of mice.

Growth of the virulent Mycobacterium avium strain TMC 724 in host tissues during persistent infection of mice was studied. Following intravenous infection of C57BL/6 mice, the kinetics of bacterial growth was biphasic in the spleen and liver, with a significant reduction of the multiplication rate after day 21 to 28 of infection. An electron-microscopic study of the liver and spleen of infected mice showed that the bacteria were strictly intracellular. They were observed within inflammatory macrophages populating granulomas disseminated in host tissues. The bacteria were confined to the phagosome compartment, and they were encapsulated. Phagosome-lysosome fusions were encountered, but the bacteria showed no visible signs of degradation and continued to multiply. These results are the first in vivo evidence that virulent M. avium multiplies exclusively intracellularly and that encapsulated bacteria resist the microbicidal mechanisms of macrophages inside the phagosomal compartment.

Molecular typing of nosocomial isolates of Legionella pneumophila serogroup 3.

In Paris, France, an outbreak of pneumonia due to Legionella pneumophila serogroup 3 was observed in Necker (four cases) and Pitié (six cases) hospitals. Neither the 10 clinical isolates nor 5 tap water isolates from Necker Hospital harbored plasmids. Clinical and environmental serogroup 3 isolates and serogroup 3 reference strain Bloomington 2 were analyzed by chromosomal probe fingerprinting. rRNA, 16S and 23S from Escherichia coli and a randomly cloned 15-kilobase-pair nucleotide sequence from L. pneumophila serogroup 3 were used as probes. All strains tested showed a single pattern after HindIII digestion of DNA and hybridization with the 32P-end-labeled rRNA probe, whereas three patterns were obtained after hybridization with the 32P-labeled 15-kilobase-pair DNA probe. One pattern was given by all clinical and tap water isolates from Necker Hospital, another one was given by all clinical isolates from Pitié Hospital, and a last one was given by reference strain Bloomington 2. Thus, molecular analysis showed that the two hospital outbreaks of legionellosis were unrelated and could link the outbreak in Necker Hospital to contaminated tap water.