Laboratory diagnosis of mycobacterial infections in patients with acquired immunodeficiency syndrome

Preparation, in vitro characterization, and in vivo pharmacokinetic evaluation of respirable porous microparticles containing rifampicin

This study aimed to prepare and evaluate rifampicin microparticles for the lung delivery of rifampicin as respirable powder. The microparticles were prepared using chitosan by the spray-drying method and evaluated for aerodynamic properties and pulmonary drug absorption. To control the drug release, tripoly-phosphate in different concentrations 0.6, 0.9, 1.2, and 1.5 was employed to get a sustained drug release profile. The microparticles were evaluated for drug loading, % entrapment efficiency, tapped density, morphological characteristics, and in vitro drug release studies. Aerosol properties were determined using the Andersen cascade impactor. Porous microparticles with particle sizes (d_0.5) less than 10 μm were obtained. The entrapment of rifampicin in microparticles was up to 72%. In vitro drug release suggested that the crosslinked microparticles showed sustained release for more than 12 hrs. The drug release rate was found to be decreased as the TPP concentration was increased. The microparticles showed a fine particle fraction in the range of 55–63% with mass median aerodynamic diameter (MMAD) values below 3 μm. The in vivo pulmonary absorption of the chitosan microparticles suggested a sustained drug release profile up to 72 hrs with an elimination rate of 0.010 per hr. The studies revealed that the spray-dried porous microparticles have suitable properties to be used as respirable powder in rifampicin delivery to the lungs.

In-hospital mortality of disseminated tuberculosis in patients infected with the human immunodeficiency virus

BACKGROUND

Tuberculosis (TB) is a cause of significant morbidity and mortality in patients with AIDS. The goal of our study was to determine predictors of in-hospital mortality in patients with AIDS and disseminated tuberculosis in a middle-income country.

MATERIAL AND METHODS

We conducted a retrospective cohort study in a tertiary care center, for patients with AIDS in southern Brazil. From 1996 to 2008, all patients with the diagnosis of disseminated TB were included.

RESULTS

Eighty patients were included. In-hospital mortality was 35% (N = 28). On multivariate Cox regression analysis, low basal albumin (P < .01) was associated with death, and fever at admission was related to better survival (P < .01).

CONCLUSION

Albumin levels or fever are independent predictors of survival in patients with HIV and disseminated TB. They can serve as indirect markers of immunodeficiency in patients with disseminated TB and AIDS.

Optimisation of culture of Mycobacterium avium subspecies paratuberculosis from blood samples

Mycobacterium avium subspecies paratuberculosis (MAP) is the causative agent of Johne's disease or paratuberculosis, a chronic enteritis of ruminants, and has been suggested to play a role in Crohn's disease in humans. While disease expression is primarily in the gastrointestinal tract, isolation of MAP or MAP DNA at distant sites indicates that disseminated infections also occur. This is the first study to compare, optimise and critically evaluate different methods of concentrating MAP from spiked blood samples to enable its culture. Whole blood, erythrocytes, but not plasma, delayed the growth of MAP in BACTEC 12B medium. Culture of MAP from buffy coats (concentrated leukocytes) after lysis of erythrocytes and washing of the cells was an effective preparatory method. Several antibiotics were evaluated to reduce contamination of the slow growing MAP cultures with microbes which were derived from the skin during venipuncture, but were detrimental to the growth of MAP. However, decontamination of erythrocyte-lysed washed buffy coat samples in 0.75% hexadecylpyridinium chloride (HPC) for 72 h prior to inoculation of culture media did not inhibit the growth of MAP. The prepared samples can be stored at -80 degrees C prior to batch culture. MAP was isolated from the blood of 2 of 23 sheep 20 months after experimental inoculation. The optimised method has an analytical sensitivity of at least 10(1) MAP per ml of spiked whole blood and will enable trials to determine the incidence, duration and magnitude of mycobacteraemia in infected animals and humans.

Prevalence of mycobacteremia in Indian HIV-infected patients detected by the MB/BacT automated culture system

The use of automated blood cultures system, such as MB/BacT, has provided a novel opportunity for laboratories to diagnose mycobacteremia in HIV-infected patients. However, no such study has been carried out in India so far. This prospective study was conducted on 52 HIV-positive patients with suspected tuberculosis who were referred to our tertiary care hospital in New Delhi. In these patients, the prevalence of mycobacteremia was evaluated using the MB/BacT automated culture system (bioMérieux, France). Twenty-seven HIV-negative but suspected tuberculosis patients were also included for comparison. Mycobacteria could be isolated from sputa or fecal samples of 20 HIV-positive patients (38.4%), and in nine (45%) of these 20 cases, mycobacteria could also be isolated simultaneously from their blood specimens. In the remaining 32 patients, all relevant non-hematological clinical samples remained negative for mycobacteria, but the pathogen could be detected from the blood samples of seven (21.87%) of these 32 patients. Therefore, only 25 (48%) clinically suspected patients remained negative in both Löwenstein-Jensen (L-J) and MB/BacT culture methods, and 12 of these responded to anti-tubercular treatment, while in the rest either non-tubercular diagnosis was established or they were lost to follow-up. The study revealed that low CD+(4) counts and poor or no reactivity to purified protein derivative (PPD) were the best clinical predictors for the occurrence of mycobacteremia in HIV-positive patients. Of the 16 isolates from blood, 13 were diagnosed as Mycobacterium tuberculosis and one each were identified as M. avium, M. kansasii, and a mixed infection of M. tuberculosis and M. avium complex. The prevalence rate of mycobacteremia was significantly low (11.1%) in HIV-negative patients. In conclusion, this study showed that blood culture could be an important adjunct investigation for confirming the clinical diagnosis of tuberculosis in HIV-positive patients.

Comparative radiological features of disseminated disease due to Mycobacterium tuberculosis vs non-tuberculosis mycobacteria among AIDS patients in Brazil

Background

Disseminated mycobacterial disease is an important cause of morbidity and mortality in patients with HIV-infection. Nonspecific clinical presentation makes the diagnosis difficult and sometimes neglected.

Methods

We conducted a retrospective cohort study to compare the presentation of disseminated Mycobacterial tuberculosis (MTB) and non-tuberculous Mycobacterial (NTM) disease in HIV-positive patients from 1996 to 2006 in Brazil.

Results

Tuberculosis (TB) was diagnosed in 65 patients (67.7%) and NTM in 31 (32.3%) patients. Patients with NTM had lower CD4 T cells counts (median 13.0 cells/mm³ versus 42.0 cells/mm³, P = 0.002). Patients with tuberculosis had significantly more positive acid-fast smears (48.0% vs 13.6%, P = 0.01). On chest X-ray, miliary infiltrate was only seen in patients with MTB (28.1% vs. 0.0%, P = 0.01). Pleural effusion was more common in patients with MTB (45.6% vs. 13.0%, P = 0.01). Abdominal adenopathy (73.1% vs. 33.3%, P = 0.003) and splenic hypoechoic nodules (38.5% vs. 0.0%, P = 0.002) were more common in patients with TB.

Conclusion

Miliary pulmonary pattern on X-ray, pleural effusion, abdominal adenopathy, and splenic hypoechoic nodules were imaging findings associated with the diagnosis of tuberculosis in HIV-infected patients. Recognition of these imaging features will help to distinguish TB from NTM in AIDS patients with fever of unknown origin due to disseminated mycobacterial disease.

Pulmonary tuberculosis in children in a developing country

OBJECTIVE

We evaluated the clinical and epidemiologic characteristics of Peruvian children presenting with pulmonary tuberculosis (PTB) to determine whether features predictive of confirmed PTB could be identified.

STUDY DESIGN

This was a cross-sectional study of 135 children (mean age: 6.8 years) presenting to the Hospital del Niño in Lima, Peru, with presumptive diagnosis of PTB. Clinical, epidemiologic, and laboratory findings were compared between 3 groups of pediatric patients with a presumptive diagnosis of PTB: those with positive Mycobacterium tuberculosis (MTB) cultures, those likely to have PTB based on clinical criteria but with negative cultures, and those who did not meet clinical diagnostic criteria or have positive cultures.

RESULTS

A total of 50 (37%) patients were diagnosed with definitive PTB based on positive sputum culture. Another 55 (47%) patients were classified as having probable PTB based on meeting at least 2 of the following criteria: cough lasting for at least 2 weeks, typical chest radiograph changes, purified protein derivative (PPD) >/=10 mm, or history of tuberculosis family contact. Patients with definitive or probable PTB were significantly older than patients without clinical PTB, and those with symptomatic disease were significantly older than those with asymptomatic disease. Patients with PTB diagnosed by culture were significantly more likely than those diagnosed using clinical criteria to have cough lasting >/=2 weeks, fever, and a PPD >/=10 mm.

CONCLUSIONS

The typical presentation of PTB in Peruvian children includes symptoms of active pulmonary disease similar to those seen in adults. This presentation differs significantly from that reported in developed countries, where many children have minimal or no symptoms at the time of presentation. The diagnostic criteria for pediatric PTB must be modified in hyperendemic developing country environments where features may differ from those described in the United States. The triad of cough lasting >/=2 weeks, fever, and a PPD >/=10 mm was highly predictive for culture-positive PTB among children in this low-income Peruvian population.

Tumor and infection localization in AIDS patients: Ga-67 and Tl-201 findings

Examples of Ga-67 and Tl-201 scans in AIDS patients performed at St. Vincent's Hospital and Medical Center of New York are presented. Use of these methods is the adopted approach at this institution in AIDS patients for localizing sites of tumor or infection involvement. A Ga-67 scan is the most common nuclear medicine examination performed on AIDS patients. Sequential Tl-201 and Ga-67 scans have a role in differentiating Kaposi's sarcoma from malignant lymphoma and opportunistic infections. For intracranial lesions, Tc-99m MIBI or Tl-201-201-201-201 chloride can differentiate malignant from benign inflammatory lesions.

An effectiveness and cost analysis of presumptive treatment for Mycobacterium tuberculosis

BACKGROUND

Delay in treatment of tuberculosis has contributed to both the spread of tuberculosis and its case fatality rate.

METHODS

Decision analysis was used to examine the effectiveness and cost of presumptive treatment in patients evaluated for tuberculosis.

RESULTS

Over a range of assumptions, empiric antituberculous therapy for acid-fast bacillus smear-positive persons lowers mortality and cost per person evaluated when available rapid diagnostic laboratory methods for tuberculosis are used. In contrast, the average cost per life saved by giving presumptive treatment to all acid-fast bacillus smear- and HIV-negative patients exceeds. $1 million. Empiric treatment for HIV-infected patients with acid-fast bacillus-negative smears decreases average mortality by 2% at an additional cost of $8000 per life saved. When the prevalence of multiple-drug resistance exceeds 9.6%, presumptive drug-resistant therapy for acid-fast bacillus smear-positive patients, rather than the initial four-drug regimen recommended for much of the United States, minimizes both mortality and costs.

CONCLUSIONS

Empiric antituberculous therapy often minimizes average mortality and cost for patients evaluated for tuberculosis when rapid diagnostic methods are used.

Sites of tuberculous involvement in patients with AIDS. Autopsy findings and evaluation of gallium imaging

The purpose of this study was to review autopsy and gallium scan findings in two different acquired immune deficiency syndrome (AIDS) patient populations who had a confirmed diagnosis of tuberculosis (TB) to identify organs involved and accuracy of clinical diagnosis. The first group was comprised of 29 autopsies between January 1982 and December 1994, including only 18 patients who were diagnosed before death. Organs most commonly involved were the lymph nodes (59%), lungs (56%), spleen (53%), liver (45%), and kidneys (37%). Other opportunistic infections were present in 18 (59%) of autopsies, with more than one opportunistic infection present in 11 (37%) of the autopsies. Lungs were involved in 79% of all autopsies. The second population group included 94 patients with AIDS with a proven diagnosis of TB, only 24 of whom had gallium scans in the period between January 1992 and December 1994. Chest x-ray results were negative in 4 patients (17%); gallium scan results were positive in 16 patients (66%). The reasons for false-negative gallium scan results were due to anti-tuberculous treatment for periods varying from 2-21 months in 7 patients or the presence of extra pulmonary tuberculosis. The sites of TB involvement in the chest were: lung parenchyma in 5 patients (19%, 4 in mid and lower lung, and 1 in upper fields). There was lymph node involvement in all 16 patients (24 locations with mediastinal involvement in 23%, supraclavicular 23%, axillary 11%, retroperitoneal 11%, and inguinal region in 4%. We conclude that (1) tuberculosis in patients with AIDS behaves similar to primary tuberculosis; (2) the combination of chest x-ray and gallium imaging is sensitive for the diagnosis of pulmonary tuberculosis in patients with AIDS; (3) the involvement of mediastinal lymph nodes in gallium scans in the presence or absence of chest x-ray abnormalities should raise the possibility of TB involvement in patients with human immunodeficiency virus; (4) anti-TB treatment decreases the sensitivity of gallium scan.

Elevated concentrations of interleukins and leukotriene in response to Mycobacterium tuberculosis infection

There is significant research in the role of interleukins in lung disease, as the cytokines are important mediators in the host response to mycobacterium tuberculosis infection. Plasma from patients with pulmonary tuberculosis (TB) and healthy controls were investigated for their content of granulocyte-macrophage colony stimulating factor (GM-CSF), interleukin-6 (IL-6) and leukotriene B4 (LTB4). LTB4 and IL-6 were measured by enzyme immunoassay after lipid extraction in the case of LTB4 while GM-CSF was measured by enzyme amplified sensitive immunoassay. Significantly elevated concentrations of IL-6 were found in far-advanced lesions of pulmonary tuberculosis patients, P < 0.05. However, nonsignificant increases of IL-6 were obtained in moderate lesions and minimal lesions compared to normal healthy subjects. Marked elevations of LTB4 were found in TB patients, the highest values being shown in patients with far-advanced lesions followed by moderately advanced and minimal lesions in relation to the mean value for normal healthy controls, P < 0.001 for all groups. 93% of the tuberculosis patients showed a higher level of LTB4 above the upper limit of the control group. In contrast there was no significant increase of GM-CSF in any of the TB subgroups. These results suggest that LTB4 and the interleukins may play a role in the pathogenesis of mycobacterium tuberculosis infection.

Effectiveness and cost of rapid and conventional laboratory methods for Mycobacterium tuberculosis screening

OBJECTIVE

Because delay in the diagnosis of tuberculosis (TB) contributes to the spread of disease and the associated mortality risk, the authors examined the effectiveness and cost of recent advances in methods of diagnosing TB and testing for drug susceptibility, comparing these rapid methods to traditional approaches.

METHODS

Decision analysis was used to compare newer rapid and older nonrapid methods for diagnosing TB and testing for drug susceptibility. The average time to diagnosis, average time to treatment, average mortality, and cost of caring for patients evaluated for TB were compared.

RESULTS

Using a combination of solid medium and broth cultures, nucleic acid probes for identification, and radiometric broth drug susceptibility testing would lead to diagnosis on average 15 days faster and to appropriate therapy on average five days sooner than methods currently employed by many U.S. laboratories. The average mortality would drop by five patients per 1000 patients evaluated (31%) and the average cost per patient would drop by $272 (18%).

CONCLUSIONS

In this era of cost containment, it is important to incorporate test sensitivity and specificity when evaluating technologies. Tests with higher unit costs may lead to lower medical expenditures when diagnostic accuracy and speed are improved. U.S. laboratories should employ available rapid techniques for the diagnosis of TB.

Disseminated mycobacterium avium complex. Review of Ga-67 and TI-201 scans and autopsy findings

A retrospective analysis of the files and Ga-67 scan findings of 32 AIDS patients with established diagnosis of disseminated Mycobacterium avium complex (MAC) was conducted in order to determine the sensitivity of Ga-67 scans for the diagnosis of this disease and the sites of MAC organ involvement. Fourteen of the 32 patients had early and delayed TI-201 scans that were also reviewed. Autopsy findings of AIDS patients in the 5 years (January 1990 to December 1994) were reviewed to determine the incidence and sites of involvement of disseminated MAC in AIDS autopsies. Chest x-ray was positive in only 41% of patients. Ga-67 scans were positive in 84% with multi-lymph node sites of involvement in 78% (hilar lymph nodes in 37.5%, supraclavicular 28.1% [all were on the left side], para-aortic 31.2%, paratracheal 18.2%, mediastinal nodes 6.2%, and axillary 3.1%), lung parenchymal in 18.7% and pleural in 9.3%). Increased uptake in the spleen in 16%, colitis 53.1% and enteritis 18.7%. Kaposi sarcoma in 9.3% and malignant lymphoma in 3.1%. TI-201 scans were only positive in 6 of 14 patients (42.8%). The autopsy data found the incidence of disseminated MAC in 23.7% (54 patients) out of a total of 228 autopsies. Approximately half of these cases (52%) were diagnosed antemortem. Other opportunistic infections were identified in 74%. The most common sites of MAC involvement were lymph nodes (74%), spleen (74%), liver (52%), lungs (22%), colon (13%), small bowel (11%), and bone marrow (9%). Associated Kaposi sarcoma was detected in 22% and non-Hodgkin's lymphoma in 13%. Problems in antemortem diagnosis were due to nonspecific presentations, involvement of intrathoracic and extrathoracic lymph nodes, liver, spleen and colon; and the higher incidence of opportunistic infections and negative chest x-ray in the majority of the patients.

Morphological study of bacteria of the respiratory system using fluorescence microscopy of Papanicolaou-stained smears with special regard to the identification of Mycobacteria sp

In Papanicolaou-stained smears certain structures such as nucleoli, Pneumocystis carinii, Charcot-Leyden crystals, bacteria and fungi show a brilliant fluorescence. The morphological characteristics of microorganisms which can be detected by this system, especially mycobacteria, are described. This screening method offers the possibility of providing the clinician with a provisional diagnosis within hours. Proof of the nature of the organisms should be obtained by culture.

Recovery of mycobacteria from blood in mycobacteria growth indicator tube and Lowenstein-Jensen slant after lysis-centrifugation

Five hundred five blood samples for culture were processed in the Isolator lysis-centrifugation system and were then inoculated into a Mycobacteria Growth Indicator Tube (MGIT) and onto a Lowenstein-Jensen (L-J) slant. Forty-nine isolates of Mycobacterium avium complex and three isolates of Mycobacterium tuberculosis were recovered from 50 of the blood culture specimens. Forty-five isolates from 43 specimens were recovered in the MGIT, with a mean time to detection of 21 days. Forty-one isolates from 40 specimens were recovered in the L-J slants, and the mean time to detection was 36 days. Nine specimens were positive in the MGIT alone, while seven specimens were positive only in L-J medium.

Isolation of atypical mycobacteria from tap water in hospitals and homes: is this a possible source of disseminated MAC infection in AIDS patients?

Infections caused by mycobacteria other than tuberculosis (MOTT), especially Mycobacterium avium complex (MAC), are common in AIDS patients, but rare in immunocompetent persons. The route of transmission is unknown, but tap water could provide a possible source of infection: MAC was isolated from tap water in the U.S.A. but this has not been reported in Germany. We therefore investigated tap water in Berlin for the presence of mycobacteria and compared radiometric (Bactec) and standard plate culture methods processing large volumes of water samples. The Bactec method yielded equal results compared to standard methods but had the advantage of easy handling. Mycobacteria were isolated from 50/118 (42.4%) samples and from 21/30 (70%) sites. The most frequently isolated species was Mycobacterium gordonae (from 28% samples and from 53.3% sites); MAC was isolated from two samples only (1.7%).

The new diagnostic mycobacteriology laboratory

Recent surveys in the USA show that many mycobacteriology laboratories continue to use less-than-optimum culture and susceptibility testing methods. This seems to be true for European countries as well. The past few years have brought significant changes to the clinical tuberculosis laboratory. High-performance liquid chromatography and direct detection of acid-fast bacilli in clinical specimens aim at the same goal: increased sensitivity and specificity of the diagnostic approach and reduction of turnaround time. This review outlines a brief comparison between contemporary traditional methods and the latest developments in the direct detection of acid-fast bacilli. If patient care and public health are always considered paramount, regardless of admission time, hospital type, etc., the current concept of services has several shortcomings. One way to manage this situation is to sort and allocate specimens according to a system of priorities. There is a growing realization that no single method by itself is the best. To streamline the best choice for laboratory diagnosis, an additional dynamic acid-fast network is presented: 'Point-of-Care,' 'Fast Track,' and 'Specialty' laboratories. The physician interacts with all three types of laboratories, so ongoing communication between the physician and the laboratory is essential. Laboratorians must work together in the formation of this dynamic acid-fast network to improve service rendered for our patients.

Inhibitory effect of the Isolator blood culture system on growth of Mycobacterium avium-M. intracellulare in BACTEC 12B bottles

The examination of 6,938 clinical specimens collected during the period January 1991 through December 1992 suggested that the Isolator blood culture system (Wampole) inhibited growth of Mycobacterium avium-M. intracellulare complex (MAC) in BACTEC 12B medium. Of 162 MAC blood culture isolates, 94% were recovered from Lowenstein-Jensen (LJ) medium, while only 50% were recovered from 12B medium. The time to detection with LJ medium was 18 days, while that with 12B medium was 24 days. In contrast, 62% of the 305 MAC nonblood culture isolates were recovered from the LJ medium, while 87% were found in the 12B medium. The time to detection for these cultures was also reversed, i.e., 28 days for LJ medium versus 15 days for 12B medium. Dilution studies using the lysis-anticoagulant reagent from Isolator tubes demonstrated inhibition of both clinical and American Type Culture Collection strains of MAC, even at low concentrations of lysis-anticoagulant reagent. Washing the Isolator blood sediment prior to inoculating the 12B bottles eliminated any growth inhibition. Clinical and experimental data suggest that the use of the Isolator blood culture tube with the BACTEC 12B medium is contraindicated for mycobacterial blood cultures.

The Mycobacterium avium complex

Mycobacterium avium complex (MAC) disease emerged early in the epidemic of AIDS as one of the common opportunistic infections afflicting human immunodeficiency virus-infected patients. However, only over the past few years has a consensus developed about its significance to the morbidity and mortality of AIDS. M. avium was well known to mycobacteriologists decades before AIDS, and the MAC was known to cause disease, albeit uncommon, in humans and animals. The early interest in the MAC provided a basis for an explosion of studies over the past 10 years largely in response to the role of the MAC in AIDS opportunistic infection. Molecular techniques have been applied to the epidemiology of MAC disease as well as to a better understanding of the genetics of antimicrobial resistance. The interaction of the MAC with the immune system is complex, and putative MAC virulence factors appear to have a direct effect on the components of cellular immunity, including the regulation of cytokine expression and function. There now is compelling evidence that disseminated MAC disease in humans contributes to both a decrease in the quality of life and survival. Disseminated disease most commonly develops late in the course of AIDS as the CD4 cells are depleted below a critical threshold, but new therapies for prophylaxis and treatment offer considerable promise. These new therapeutic modalities are likely to be useful in the treatment of other forms of MAC disease in patients without AIDS. The laboratory diagnosis of MAC disease has focused on the detection of mycobacteria in the blood and tissues, and although the existing methods are largely adequate, there is need for improvement. Indeed, the successful treatment of MAC disease clearly will require an early and rapid detection of the MAC in clinical specimens long before the establishment of the characteristic overwhelming infection of bone marrow, liver, spleen, and other tissue. Also, a standard method of susceptibility testing is of increasing interest and importance as new effective antimicrobial agents are identified and evaluated. Antimicrobial resistance has already emerged as an important problem, and methods for circumventing resistance that use combination therapies are now being studied.

Mycobacteria in stool specimens: the nonvalue of smears for predicting culture results

A previous recommendation suggests that stool be cultured for mycobacteria only if the smear is positive. We have correlated smear and culture results of 2,176 stool specimens submitted for mycobacterial culture. The sensitivity, specificity, and positive and negative predictive values for smears to predict culture results are 34, 99, 90, and 87%, respectively. We recommend that the stool smear not be used as a screening technique to decide which specimens from at-risk patients should be cultured because it lacks the necessary sensitivity.

Gastro-intestinal involvement in Mycobacterium avium-intracellulare infection of patients with HIV

In a study of 866 faecal specimens from 437 persons, Mycobacterium avium-intracellulare (MAI) was isolated from 14.8% patients with AIDS and 1.3% patients with symptomatic HIV infection but not from any HIV seronegative or asymptomatic HIV seropositive persons. These data support the hypothesis that the gastro-intestinal tract is the portal of entry for MAI and confirm that MAI infection is a manifestation of late-stage HIV disease. Positive faecal cultures correlated well with disseminated disease. The use of faecal cultures for early diagnosis is therefore recommended.

Detection of mycobacteria from blood and bone marrow: a decade of experience

This study reports our experience with methods used at our department from 1981 through 1990 for detection of mycobacteria in blood and bone marrow specimens. Direct inoculation on Lowenstein Jensen media was replaced by Isolator lysis-centrifugation followed by inoculation on conventional solid media, and the Bactec 12B and Bactec 13A systems. A total of 3033 specimens were analyzed. A total of 137 mycobacterial isolates were obtained from 42 patients, all HIV-positive except one. Mycobacteremia caused by M. avium-intracellulare (83%), M. tuberculosis, M. scrofulaceum and M. kansasii was found. Of 680 blood specimens tested by the last three methods, 7.6% were found to be positive by at least one method and revealed recovery rates of 6.8% for the Isolator-solid media system, 3.4% for the Isolator-12B system and 6.9% for the 13A system (all isolates MOTT). Mean detection times for 21 cultures found positive by all three methods were 23.6, 23.3 and 17.7 days for the Isolator-solid media, Isolator-12B and 13A systems, respectively, with a significantly shorter detection time for the 13A system. Low degree (less than 1 cfu/ml) mycobacteremia (MOTT) caused delay in the Isolator-solid media and the 13A systems and no detection in the Isolator-12B system. Antituberculous therapy significantly prolonged the detection times for MOTT in the 13A system in contrast to the other systems.

In vitro activity of DNA gyrase inhibitors, singly and in combination, against Mycobacterium avium complex

The in vitro activities of the DNA gyrase inhibitors ciprofloxacin, coumermycin, and novobiocin against 31 clinical isolates of Mycobacterium avium complex were studied using a microdilution technique. Minimal inhibitory concentrations (MICs) were determined in 4 days using Middlebrook 7H9 broth, and minimal bactericidal concentrations (MBCs) were determined by subculturing to Middlebrook 7H10 agar. MICs were: ciprofloxacin, 0.5-greater than 16 (mean, 4.1) micrograms/ml; novobiocin, 4-greater than 128 (mean, 54.7) micrograms/ml; and coumermycin, 2-greater than 16 (mean, 17.5) micrograms/ml. MBCs were usually more than two dilution steps higher than MICs. Checkerboard studies failed to reveal synergistic or antagonistic inhibitory activity of DNA gyrase-A and DNA gyrase-B inhibitors in vitro.

Production and analysis of specific monoclonal antibodies against the cell wall of Mycobacterium avium

Monoclonal antibodies (mAbs) against Mycobacterium avium were produced which specifically reacted with cell walls of M. avium. The binding pattern was not limited to one subtype. The three most specific mAbs showed binding to the outer surface of M. avium but not to other mycobacterial or bacterial cell surfaces. The combined results of enzyme-linked immunosorbent assay, immunoblot and dot blot showed that mAb 4A006 bound to an epitope located in the cell wall and on the cell surface and mAb 4A010 to an epitope exposed on the cell surface and the cytoplasm. The mAb 4A009-binding epitope was only detectable on the cell surface but not in the cell wall or cytoplasmic fractions of M. avium. In the immunoblot technic a protein antigen with a molecular mass of 27-29 kDa was identified by the mAbs. The mAb 4A006 reacted with 142 out of 143 M. avium subtypes 1, 4 and 8 obtained from AIDS patients. These mAbs seem to be applicable for the identification of M. avium complex after culture.

Transmission of tuberculosis to hospital workers by a patient with AIDS

A patient with acquired immunodeficiency syndrome (AIDS) was admitted to a hospital with cough and fever and after 29 days was transferred to a hospice. He was eventually shown to have active pulmonary tuberculosis. This diagnosis was obscured clinically by simultaneous infection with Pneumocystis carinii and Mycobacterium avium complex (MAC). Laboratory recognition of Mycobacterium tuberculosis was delayed because of overgrowth of cultures by MAC but was later established using DNA probe techniques. Thirty (19 percent) of 158 health care workers who had been exposed to this patient had conversion of their tuberculin skin tests. Diagnostic difficulties and nosocomial transmission of tuberculosis may occur when patients with AIDS have mixed mycobacterial infections.

Medical management of AIDS patients. Tuberculosis and nontuberculous mycobacterial disease

AIDS has been responsible for a significant increase in mycobacterial disease, which in this setting is often extrapulmonary. In contrast to HIV-associated Mycobacterium avium complex disease, HIV-associated tuberculosis is normally transmissible between humans by the aerosol route, occurs earlier than most AIDS-related infections, and is readily treatable and preventable with conventional drugs.

Enhanced radiometric detection of Mycobacterium paratuberculosis by using filter-concentrated bovine fecal specimens

A commercial radiometric medium, BACTEC 12B, was modified by addition of mycobactin, egg yolk suspension, and antibiotics (vancomycin, amphotericin B, and nalidixic acid). Decontaminated bovine fecal specimens were filter concentrated by using 3-microns-pore-size, 13-mm-diameter polycarbonate filters, and the entire filter was placed into the radiometric broth. Comparison of the radiometric technique with conventional methods on 603 cattle from 9 Mycobacterium paratuberculosis-infected herds found that of 75 positive specimens, the radiometric technique detected 92% while conventional methods detected 60% (P less than 0.0005). Only 3.9% of radiometric cultures were contaminated. To measure the effect of filter concentration of specimens on the detection rate, 5 cattle with minimal and 5 with moderate ileum histopathology were sampled weekly for 3 weeks. M. paratuberculosis was detected in 33.3% of nonfiltered specimens and 76.7% of filtered specimens (P less than 0.005). Detection rates were directly correlated with the severity of disease, and the advantage of specimen concentration was greatest on fecal specimens from cattle with low-grade infections. Detection times were also correlated with infection severity: 13.4 +/- 5.9 days with smear-positive specimens, 27.9 +/- 8.7 days with feces from cows with typical subclinical infections, and 38.7 +/- 3.8 days with fecal specimens from cows with low-grade infections. Use of a cocktail of vancomycin, amphotericin B, and nalidixic acid for selective suppression of nonmycobacterial contaminants was better than the commercial product PANTA (Becton Dickinson Microbiologic Systems, Towson, Md.) only when specimens contained very low numbers of M. paratuberculosis. Radiometric culture of filter-concentrated specimens generally doubled the number of positive fecal specimens detected over conventional methods, making it a useful tool for diagnosis and control of bovine paratuberculosis.

Severe tuberculosis in patients with human immunodeficiency virus infection

Tuberculosis has now been well documented as a complication of infection with human immunodeficiency virus (HIV), but no studies concern patients requiring admission to the ICU. We report 12 cases of severe disseminated tuberculosis in patients who were seropositive for HIV. Eight patients had diffuse pulmonary involvement responsible for acute respiratory failure, 7 of whom required mechanical ventilation. Four developed septic shock, and in 3 blood cultures were positive for M. tuberculosis. Four patients had central nervous system involvement, with coma requiring mechanical ventilation 3 times. Rapid diagnosis was permitted in 10 patients by acid-fast smears of pulmonary specimens (8 patients) and/or tissue biopsies (4 patients). Seven patients died despite intensive therapy; autopsy was performed in 4 patients, showing disseminated tuberculosis. On the basis of this report, tuberculosis in HIV infection may present as an overwhelming systemic disease and thus requires an aggressive diagnostic and therapeutic approach.

Immunosuppression and mycobacteria other than Mycobacterium tuberculosis: results from patients with and without HIV infection

Infections caused by mycobacteria other than Mycobacterium tuberculosis (MOTT) have often been described as common in AIDS patients. To evaluate whether infections with MOTT are specific for HIV related immunosuppression or are also frequent in patients with immunosuppression of different aetiology, data on the frequency of isolation from immunosuppressed patients with HIV infection are important. Blood, stool and urine specimens from 134 patients with non-HIV related immunosuppression, and from 55 immunocompetent subjects were examined for mycobacteria. MOTT have been isolated from one immunocompetent person but from none of the immunosuppressed patients. Since in AIDS patients an initial colonization of the gastrointestinal tract (GI-tract) with MOTT is common, GI-tract biopsy specimens from an additional 80 patients were examined microscopically and histologically for mycobacteria. Mycobacteria were not isolated from these specimens. In the same period of time 72 AIDS patients have been examined; 7 (10%) had infections with M. tuberculosis whereas MOTT have been isolated from 16 (22%) of these patients. Mycobacteria have been found only rarely in immunocompetent patients and have not been isolated from patients with non-HIV related immunosuppression. The isolation of MOTT is highly correlated with an HIV-related immunosuppression.

Mycobacterial disease, immunosuppression, and acquired immunodeficiency syndrome

The mycobacteria are an important group of acid-fast pathogens ranging from obligate intracellular parasites such as Mycobacterium leprae to environmental species such as M. gordonae and M. fortuitum. The latter may behave as opportunistic human pathogens if the host defenses have been depleted in some manner. The number and severity of such infections have increased markedly with the emergence of the acquired immunodeficiency syndrome (AIDS) epidemic. These nontuberculous mycobacteria tend to be less virulent for humans than M. tuberculosis, usually giving rise to self-limiting infections involving the cervical and mesenteric lymph nodes of young children. However, the more virulent serovars of M. avium complex can colonize the bronchial and intestinal mucosal surfaces of healthy individuals, becoming virtual members of the commensal gut microflora and thus giving rise to low levels of skin hypersensitivity to tuberculins prepared from M. avium and M. intracellulare. Systemic disease develops when the normal T-cell-mediated defenses become depleted as a result of old age, cancer chemotherapy, or infection with human immunodeficiency virus. As many as 50% of human immunodeficiency virus antibody-positive individuals develop mycobacterial infections at some time during their disease. Most isolates of M. avium complex from AIDS patients fall into serotypes 4 and 8. The presence of these drug-resistant mycobacteria in the lungs of the AIDS patient makes their effective clinical treatment virtually impossible. More effective chemotherapeutic, prophylactic, and immunotherapeutic reagents are urgently needed to treat this rapidly increasing patient population.

Results of blood cultures for detection of mycobacteria in AIDS patients

Since the advent of the acquired immunodeficiency syndrome (AIDS) numerous M. avium intracellulare disseminated infections have been recognised. Blood culture is a convenient method for diagnosing these infections. At Pitié-Salpêtrière hospital AIDS patients with persistent unexplained fever each had three blood cultures. The blood samples, taken on 3 consecutive days without taking in account fever peaks, were collected in the Isolator-10 lysis-centrifugation system and inoculated onto Löwenstein-Jensen medium with and without 0.25% sodium pyruvate. From February 1986-September 1987, 564 samples taken from 165 patients were cultivated for the detection of mycobacteria. Sixty one (10.8%) taken from 19 patients (11.5%) were positive. M. avium intracellulare was the most frequently isolated mycobacterial species. In 10 patients, the positive blood culture was the only or the first positive culture for mycobacteria.

Evaluation of four mycobacterial blood culture media: BACTEC 13A, Isolator/BACTEC 12B, Isolator/Middlebrook agar, and a biphasic medium

Four commercially available mycobacterial blood culture systems were compared for sensitivity and time to detection of growth. A 5-ml volume of SPS-anticoagulated blood was cultured in a BACTEC 13A vial and a modified M7H11/BHI biphasic medium. In addition, two aliquots of Isolator concentrates, each derived from 5 ml of blood, were inoculated into a BACTEC 12B vial and onto a pair of Middlebrook 7H11 agar plates (M7H11). Mycobacteria were recovered from 32 of 180 cultured specimens (17.8%). Growth was detected in 30 (93.7%) of the 13A vials, 27 (84.4%) of the M7H11 agar plates, 26 (81.2%) of the 12B vials, and 14 (43.8%) of the biphasic bottles. The mean times to growth detection in the 13A vial (14.2 days) and the 12B vial (13.7 days) were shorter than in either the M7H11 plates (20.8 days) or the biphasic medium (24.1 days). When the Isolator/12B vial-and-M7H11 plates were evaluated as a single system, 29 cultures (90.6%) had a mean time to growth detection of 13.5 days. Colony-forming units per ml were inversely associated with time to growth detection. Delay in transport (greater than 24 h) appeared to reduce viability. The direct inoculation feature makes the 13A vial very suitable for mycobacterial blood cultures.

Mixed mycobacterial cultures--occurrence in the clinical laboratory

During a 2-year period we observed at our institution 22 mixed mycobacterial cultures among a total of 991, representing 20 patients. We found no evidence of double infection. Mixed cultures frequently contained saprophytic organisms. Our experiments have shown that subculturing, especially into liquid media, can significantly change the relative quantities of CFU's present in mixed cultures. We believe that the use of agar media is useful for the recognition of mixed cultures.

Mycobacteremia caused by simultaneous infection with Mycobacterium avium and Mycobacterium intracellulare detected by analysis of a BACTEC 13A bottle with the Gen-Probe kit

Simultaneous infection with Mycobacterium avium and Mycobacterium intracellulare in an AIDS patient was suspected after direct analysis of two BACTEC 13A blood cultures with the Gen-Probe kit for M. avium complex. A mixed infection was confirmed by evaluating isolated colonies. The Gen-Probe kit may provide a simple technique for detecting mixed M. avium-M. intracellulare infections.

Comparison of BACTEC 13A medium and Du Pont isolator for detection of mycobacteremia

BACTEC 13A medium (Johnston Laboratories, Towson, Md.) was compared with Isolator (Du Pont Co., Wilmington, Del.) concentrate for sensitivity, speed, and technical ease of isolation of mycobacteria from paired patient blood samples. Of 72 positive cultures, 63 were positive by both systems. Five positive cultures were detected by BACTEC 13A medium alone, and four were detected by Isolator alone. The median numbers of days to positivity were 12 for BACTEC 13A medium and 14 for Isolator concentrate. BACTEC 13A medium has an advantage over the Isolator in requiring less laboratory manipulation of the specimen but has the disadvantages of not providing isolated colonies or quantitation of organisms. Some technical problems with contamination in both systems are also discussed.

Comparison of three methods for recovery of Mycobacterium avium complex from blood specimens

Three methods were used for the recovery of mycobacteria from blood specimens obtained from acquired immunodeficiency syndrome patients: (i) inoculation of 7H11 agar plates with a concentrated specimen, (ii) inoculation of 7H12 BACTEC vials with a concentrated specimen, and (iii) inoculation of 7H13 BACTEC vials with a nonconcentrated specimen. In this study, we examined 255 specimens and obtained positive mycobacterial growth in 47 of them. Among these 47 cultures, 40 were found to be positive by all three methods, and the total recovery rates in relation to these culture-positive specimens were 94% for method 1, 89% for method 2, and 96% for method 3. The advantages and disadvantages of these three methods are discussed.

Comparative recoveries of Mycobacterium avium-M. intracellulare from isolator lysis-centrifugation and BACTEC 13A blood culture systems

Blood cultures processed with a lysis-centrifugation (Isolator) system and a radiometric (BACTEC 13A) broth system were compared for the recovery of Mycobacterium avium-M. intracellulare from patients with acquired immunodeficiency syndrome. Forty-nine isolates of M. avium-M. intracellulare were recovered by both systems, 9 were recovered by the Isolator system only, and 12 were recovered by the BACTEC system only. Average times to detection were 16 and 14 days for the Isolator and BACTEC systems, respectively. There was no significant difference between the two blood culture systems in sensitivity or time to detection.

Rapid identification using a specific DNA probe of Mycobacterium avium complex from patients with acquired immunodeficiency syndrome

Specific DNA probes (Gen-Probe Corp., San Diego, Calif.) for Mycobacterium avium, Mycobacterium intracellulare, and Mycobacterium tuberculosis were compared with conventional methods for the identification of isolates of the Mycobacterium avium complex. A total of 56 isolates of M. avium complex were recovered from 34 respiratory, 13 blood, 6 stool, and 3 urine samples from 23 patients. A total of 33 isolates were tested directly from Middlebrook 7H11 agar plates, and 23 isolates were tested directly from BACTEC radiometric 12B bottles (Johnston Laboratories, Inc., Towson, Md.). Of the 56 M. avium complex isolates, 41 tested positive with the M. avium probe, 4 were positive with the M. intracellulare probe, and 7 were positive with both probes. Four direct tests from BACTEC bottles were initially negative but were subsequently M. avium probe positive when subcultures from Lowenstein-Jensen agar were tested. All 56 strains were negative when tested with the M. tuberculosis probe.