Non-tuberculous mycobacteria: patterns of isolation. A multi-country retrospective survey

OBJECTIVE

To collect data on non-tuberculous mycobacteria (NTM) isolated from clinical laboratories in different countries to establish: 1) whether the isolation of NTM was increasing, 2) which species were increasing, and 3) whether there was any pattern of geographical distribution.

DESIGN

In 1996, the Working Group of the Bacteriology and Immunology Section of the International Union Against Tuberculosis and Lung Disease contacted 50 laboratories in different countries for the necessary information.

RESULTS

The number of patients reported with NTM was 36099 from 14 countries. Mycobacterium avium complex, M. gordonae, M. xenopi, M. kansasii and M. fortuitum were the five species most frequently isolated. There was a significant upward trend for M. avium complex and M. xenopi. Pigmented mycobacteria predominated in Belgium, the Czech Republic and the Mediterranean coast of Spain. Non-chromogenic mycobacteria were found to be predominant in the area of the Atlantic coast of Brazil and in Turkey, the United Kingdom, Finland and Denmark.

CONCLUSIONS

There was an increase in the number of NTM isolated from clinical samples of patients. Isolation of the most frequent species is constantly changing in most of the geographical areas, and newer species are emerging due to better diagnostic techniques to detect and identify NTM.

Generalized tuberculosis in llamas (Lama glama) due to Mycobacterium microti

Necropsy of two llamas revealed numerous caseous nodules containing abundant acid-fast bacilli (AFB) in various organs. The AFB were identified by spoligotyping as Mycobacterium microti, vole type. Infection caused by M. microti should be considered in the differential diagnosis of debilitating diseases in New World camelids.

[First isolation of tuberculous mycobacteria in man and animals in Chad]

This report describes the first successful isolation and identification of mycobacterial infection in humans and animals of Chad. All mycobacterial strains from human specimens were M. tuberculosis and strains from animal specimens (cattle) were M. bovis. None of the 10 of M. tuberculosis strains tested for antibiotic resistance were multidrug resistant. Due to the intrinsic resistance of M. bovis to pyrazinamide and the growing number of tuberculosis cases in HIV-infected people in Africa and elsewhere, more information on the potential of M. bovis for human infection is needed to guide disease control policy.

False-positive Mycobacterium tuberculosis culture revealed by restriction fragment length polymorphism analysis

BACKGROUND

The microbiological analysis of respiratory specimens is the most reliable approach to diagnose active pulmonary tuberculosis.

PATIENT AND METHODS

We report a 60-year-old female patient (index patient) who underwent diagnostic bronchoscopy for chronic cough. No acid-fast bacilli were detected in bronchial washings. Although cough subsided with symptomatic treatment, Mycobacterium tuberculosis grew on egg-based media after 12 weeks. A false-positive culture result was suspected. Chart review and DNA fingerprinting were carried out.

RESULTS

The bronchoscope used to examine the index patient was previously used for a 30-year-old patient (source patient) with smear- and culture-positive pulmonary tuberculosis. Restriction fragment length polymorphism (RFLP) analysis based on the IS 6110 element confirmed that the two strains were identical.

CONCLUSION

Cross-contamination is a reason for false-positive cultures with M. tuberculosis and should be suspected in patients with a low clinical probability for active tuberculosis.

Ocular manifestation of disseminated Mycobacterium simiae infection in a cat

Disseminated mycobacterial disease was diagnosed in an eight-year-old domestic shorthaired cat, with involvement of the skin, lungs, lymph nodes and one eye. Mycobacterium simiae was cultured from skin biopsies on solid agar and in liquid media. This organism is known to cause pulmonary, cutaneous or disseminated infection in human patients with acquired immunodeficiency syndrome but has never been encountered as a pathogen in companion animals. Combination treatment with rifampicin, enrofloxacin and clarithromycin resulted in complete clinical remission within six months, with no side effects. No recurrence was observed in a 22-month follow-up period.

Resistance to antimicrobial agents in Mycobacterium tuberculosis

According to the World Health Organization (WHO) more people will currently die of tuberculosis (TB) than in any other year in history. Of equal concern are the emergence and nosocomial transmission of multidrug-resistant (MDR) strains of Mycobacterium tuberculosis. Only recently, with the advent of new molecular biological techniques, the mechanisms of drug resistance in TB bacilli are more and more understood. In M. tuberculosis, the primary mechanism of drug resistance seems to be exclusively confined to chromosomal DNA and not, as in other bacteria, to mobile genetic elements as well.

[Sensitivity of bacteria to antibiotics (Zurich, 2000)]

This paper describes the frequency of susceptibility of Gram-negative and Gram-positive bacteria against antibacterial agents. Data are based on all susceptibility tests performed at the Department of Medical Microbiology of the University of Zurich in 2000. The evaluation of the results from 1987 to 2000 shows that susceptibilities against the antimicrobial agents tested have not markedly changed with the following exceptions: 7% of Staphylococcus aureus are resistant against methicillin, 8% of pneumococci have a reduced susceptibility to penicillin, 1% is resistant to penicillin, and 10% are resistant to macrolides. 9% of group A streptococci are resistant to macrolides. Quinolone resistance is markedly high in the medical practice with 10% of E. coli strains and 32% of Campylobacter sp. Strains of Klebsiella pneumoniae and E. coli producing extended spectrum betalactamases are isolated occasionally. Of all strains of Mycobacterium tuberculosis isolated from clinical specimens in 2000, 4% were multi-drug resistant. The tables may be a help for the physician in his decision for a "calculated chemotherapy" of bacterial infections.

Laboratory diagnosis of mycobacterial infections: new tools and lessons learned

Even in the 21st century, tuberculosis continues to be a problem. Although the number of cases continues gradually to decrease in the United States, cases get more difficult to treat, specifically those that are multiple-drug resistant. Infection of one-third of the world's population ensures that tuberculosis will not disappear in the near future. In light of this, it will be useful to know the goals for the health care system and how these goals may be accomplished. Laboratory testing in the mycobacteriology field is experiencing more changes today than ever before. Determining what assays will be most useful to the clinician is a challenge, and acceptance of the new technology by the medical community an even greater one. Clinicians must use the best available resources to determine the most appropriate care for their patients and work together with the laboratory to ensure that the communication channels are open. This review focuses on current state-of-the-art resources useful for accurate and rapid laboratory diagnosis of mycobacterial infections.

Application of the Sherlock Mycobacteria Identification System using high-performance liquid chromatography in a clinical laboratory

There is a growing need for a more accurate, rapid, and cost-effective alternative to conventional tests for identification of clinical isolates of Mycobacterium species. Therefore, the ability of the Sherlock Mycobacteria Identification System (SMIS; MIDI, Inc.) using computerized software and a Hewlett-Packard series 1100 high-performance liquid chromatograph to identify mycobacteria was compared to identification using phenotypic characteristics, biochemical tests, probes (Gen-Probe, Inc.), gas-liquid chromatography, and, when necessary, PCR-restriction enzyme analysis of the 65-kDa heat shock protein gene and 16S rRNA gene sequencing. Culture, harvesting, saponification, extraction, derivatization, and chromatography were performed following MIDI's instructions. Of 370 isolates and stock cultures tested, 327 (88%) were given species names by the SMIS. SMIS software correctly identified 279 of the isolates (75% of the total number of isolates and 85% of the named isolates). The overall predictive value of accuracy (correct calls divided by total calls of a species) for SMIS species identification was 85%, ranging from only 27% (3 of 11) for M. asiaticum to 100% for species or groups including M. malmoense (8 of 8), M. nonchromogenicum (11 of 11), and the M. chelonae-abscessus complex (21 of 21). By determining relative peak height ratios (RPHRs) and relative retention times (RRTs) of selected mycolic acid peaks, as well as phenotypic properties, all 48 SMIS-misidentified isolates and 39 (91%) of the 43 unidentified isolates could be correctly identified. Material and labor costs per isolate were $10.94 for SMIS, $26.58 for probes, and $42.31 for biochemical identification. The SMIS, combined with knowledge of RPHRs, RRTs, and phenotypic characteristics, offers a rapid, reasonably accurate, cost-effective alternative to more traditional methods of mycobacterial species identification.

Can the API (RAPID) Coryne system be used for identification of rapidly growing mycobacteria?

Fifty-six strains of rapidly growing mycobacteria (RGM) and 14 strains of aerobic actinomycetes as quality controls (QC) were tested in the API (RAPID) Coryne system version 2. Both groups yielded codes with low identification scores, considerable overlaps, and similar diagnoses. No species-specific codes were observed. Thus, the system would not be useful for the identification of RGM.

Multidrug-resistant tuberculosis in prison inmates, Azerbaijan

In a tuberculosis (TB) program in the Central Penitentiary Hospital of Azerbaijan, we analyzed 65 isolates of Mycobacterium tuberculosis by IS6110-based restriction fragment-length polymorphism (RFLP) and spoligotyping. From 11 clusters associated with 33 patients, 31 isolates had an IS6110-based banding pattern characteristic of the Beijing genotype of M. tuberculosis. In addition, 15 M. tuberculosis isolates with similar RFLP patterns constituted a single group by spoligotyping, matching the Beijing genotype. Multidrug resistance, always involving isoniazid and rifampin, was seen in 34 (52.3%) of 65 isolates, with 28 belonging to the Beijing genotype.

Farm and slaughter survey of bovine tuberculosis in captive deer in Switzerland

In 1998, a survey was conducted by postal questionnaire to gather basic knowledge about the management, health and productivity of captive deer in Switzerland. In addition, lymph nodes were collected from slaughtered deer from 124 of the 262 holdings surveyed, and tested for Mycobacterium bovis and Mycobacterium tuberculosis. The total farmed deer population was 8389 animals kept on 485 holdings; 87 per cent were fallow deer, 8 per cent red deer, 4 per cent sika deer, and there were small numbers of other species. The median herd sizes were 12 for fallow deer and eight for red deer. Few owners had handling facilities or crushes. In none of the lymph nodes examined were lesions typical of bovine tuberculosis observed, and neither M bovis nor M tuberculosis was cultivated from any of the samples.

Drug-resistant tuberculosis: resistance mechanisms and rapid susceptibility testing

Globally, the emergence of multidrug-resistant strains of Mycobacterium tuberculosis is an increasing problem which adversely affects patient care and public health. In contrast to other bacteria, resistance of M. tuberculosis is exclusively associated with chromosomal mutations. Recently developed molecular biological techniques have significantly helped in understanding the basis of drug action and resistance mechanisms in this organism. The information gained at the molecular level will help to develop efficient future diagnostic strategies and create novel drugs, both of which will ultimately have a direct impact on treatment programmes.

Surveillance of antituberculosis drug resistance in Switzerland 1995-1997: the central link

The purpose of the present paper is to investigate the usefulness of routine notification of antituberculosis drug susceptibilities. In Switzerland, laboratories have to report susceptibilities to isoniazid, rifampicin, ethambutol, and pyrazinamide to the Federal Office of Public Health. All clinical and laboratory information on every single tuberculosis case is routinely linked. Proportions of drug resistance were calculated and logistic regression was applied to evaluate the role of potential risk factors. Eighty percent (1056) of all culture-positive tuberculosis cases reported between October 1995 and December 1997 were analysed. The strains of 66 (6.3%) patients had resistances to at least one drug. Risk factors identified were previous antituberculosis treatment (adjusted odds ratio 7.3, 95% confidence interval 3.9-13.6), male sex (1.4, 1.1-2.0), and age <65 yrs (1.5, 1.0-2.3). Fourteen cases (1.3%), 13 of them foreign-born, were resistant to at least isoniazid and rifampicin. Reporting of drug susceptibilities allows routine assessment of the proportion of drug resistant tuberculosis and populations at risk. This proportion was found to be small in Switzerland. Risk factors were previous treatment for tuberculosis, male sex, and age <65 yrs. Resistance to at least isoniazid and rifampicin was predominantly found in foreign-born patients.

The role of clinical suspicion in evaluating a new diagnostic test for active tuberculosis: results of a multicenter prospective trial

CONTEXT

In laboratory trials, nucleic acid amplification tests for the diagnosis of tuberculosis (TB) are more accurate than acid-fast bacilli (AFB) smear microscopy and are faster than culture. The impact of these tests on clinical diagnosis is not known.

OBJECTIVE

To assess the performance of a nucleic acid amplification test, the enhanced Mycobacterium tuberculosis Direct (E-MTD) test, against a uniform clinical standard stratified by level of clinical suspicion.

DESIGN

Prospective multicenter trial conducted between February and December 1996, documenting the clinical suspicion of TB at enrollment and using final comprehensive diagnosis as the criterion standard.

SETTING

Six urban medical centers and 1 public health TB clinic.

PATIENTS

A total of 338 patients with symptoms and signs consistent with active pulmonary TB and complete clinical diagnosis were stratified by the clinical investigators to be at low (< or =25%), intermediate (26%-75%), or high (>75%) relative risk of having TB.

MAIN OUTCOME MEASURES

Sensitivity, specificity, and positive and negative predictive values of the E-MTD test in clinical suspicion of groups with low (n = 224); intermediate (n = 68); and high (n = 46) clinical suspicion of TB.

RESULTS

Based on comprehensive clinical diagnosis, sensitivity of the E-MTD test was 83%, 75%, and 87% for low, intermediate, and high clinical suspicion of TB, respectively, and corresponding specificity was 97%, 100%, and 100% (P = .25). Positive predictive value of the E-MTD test was 59% (low), 100% (intermediate), and 100% (high) compared with 36% (low), 30% (intermediate), and 94% (high) for AFB smear. Corresponding negative predictive values were 99%, 91%, and 55% [corrected] (E-MTD test) vs 96%, 71%, and 37% (AFB smear).

CONCLUSIONS

For complex diagnostic problems like TB, clinical risk assessments can provide important information regarding predictive values more likely to be experienced in clinical practice. For this series, a clinical suspicion of TB was helpful in targeting areas of the clinical spectrum in which nucleic acid amplification tests can make an important contribution.

Molecular epidemiology of tuberculosis among HIV-infected persons in Switzerland: a countrywide 9-year cohort study. Swiss HIV Cohort Study

We investigated tuberculosis transmission during a nine-year period (1988-1996) in a countrywide community-based cohort of HIV-infected persons in Switzerland (the Swiss HIV Cohort Study [SHCS]). We estimated the proportion of tuberculosis cases due to reinfection and relapse, and assessed factors which may increase the risk of tuberculosis transmission. HIV-infected persons were followed prospectively and molecular fingerprinting with insertion sequence (IS) 6110, 36-bp direct repeat, and IS6110-PCR was used to determine M. tuberculosis case clustering. Out of 7999 SHCS participants, 267 persons developed tuberculosis. 158 M. tuberculosis isolates from 138 patients were available for study. Molecular analysis identified 33 (24%) episodes of tuberculosis associated with 12 clusters including 2 to 8 patients. Two patients experienced reinfection, and nine had a relapse. Detailed contact investigation identified definite or possible epidemiological links between 21 of 33 cluster patients (64%). Multivariate logistic regression analysis did not identify any risk marker significantly associated with clustering. During a nine-year period, one fourth of tuberculosis cases were grouped in clusters within a selection of 138 HIV-infected patients. This may represent the lowest estimation of recently acquired tuberculosis infection. There were no large institutional or community outbreaks among HIV-infected participants of the Swiss HIV Cohort Study.

Sporadic tuberculous meningoencephalitis

Tuberculous meningoencephalitis in a 24-month-old boy is reported. He contracted the infection from his apparently healthy grandfather with unnoticed pulmonary tuberculosis, as suggested by restriction fragment length polymorphism analysis of the isolated pathogen.

Multicenter laboratory validation of susceptibility testing of Mycobacterium tuberculosis against classical second-line and newer antimicrobial drugs by using the radiometric BACTEC 460 technique and the proportion method with solid media

In a large multicenter study involving six major study sites in the United States, Canada, and Europe, the susceptibilities of 272 Mycobacterium tuberculosis strains to classical second-line antituberculosis (anti-TB) drugs (capreomycin, cycloserine, ethionamide, and kanamycin) and newer compounds (amikacin, clofazimine, ofloxacin, and rifabutin) were determined by the radiometric BACTEC 460 procedure and the conventional proportion method on Middlebrook 7H10 agar. Previously established critical concentrations for classical second-line anti-TB drugs were compared with several concentrations in liquid medium to establish equivalence. MICs of newer compounds determined in liquid medium were either the same or up to four times lower than those determined in agar medium. After establishing critical concentrations (breakpoints) in the extended testing of clinical isolates, we obtained an excellent overall correlation between the two systems, with no errors with amikacin, kanamycin, and ofloxacin and very few major or very major errors with the other drugs; however, for cycloserine, no breakpoint concentration could be recommended due to repeatedly inconsistent results by both methods. Based on these data we conclude that the BACTEC 460 procedure is a simple and rapid method requiring 4 to 8 days on average to generate accurate antimicrobial susceptibility testing (AST) results for eight anti-TB drugs other than those considered primary ones. These data not only fill a major gap of knowledge regarding the critical test concentrations of secondary anti-TB drugs but also provide a baseline for future evaluations of M. tuberculosis AST with the more recently developed, nonradiometric broth-based culture systems.

Mycobacterium wolinskyi sp. nov. and Mycobacterium goodii sp. nov., two new rapidly growing species related to Mycobacterium smegmatis and associated with human wound infections: a cooperative study from the International Working Group on Mycobacterial Taxonomy

Previous investigations demonstrated three taxonomic groups among 22 clinical isolates of Mycobacterium smegmatis. These studies were expanded to 71 clinical isolates, of which 35 (49%) (group 1) were identical to five ATCC reference strains including the type strain ATCC 19420T. Twenty-eight isolates (39%) were group 2, and eight isolates (11%) were group 3. Isolates of groups 2 and 3 were most often associated with post-traumatic or post-surgical wound infections including osteomyelitis, were susceptible to sulfamethoxazole, amikacin, imipenem and the tetracyclines, variably resistant to clarithromycin, and susceptible (group 1), intermediately resistant (group 2) or resistant (group 3) to tobramycin. The three groups were similar by routine biochemical and growth characteristics, but had different mycolic acid dimethoxy-4-coumarinylmethyl ester elution patterns by HPLC and different PCR-restriction enzyme patterns of a 439 bp fragment of the hsp-65 gene. Group 3 isolates differed from group 1 by 18 bp by 16S rRNA sequencing and exhibited < 25% homology by DNA-DNA hybridization, being most closely related to Mycobacterium mageritense. The 16S rRNA of group 1 and group 2 isolates differed by only 3 bp, but by DNA-DNA hybridization they exhibited only 40% homology. The following names are proposed: Mycobacterium goodii sp. nov. for group 2 isolates (type strain ATCC 700504T = MO69T), Mycobacterium wolinskyi sp. nov. for group 3 isolates (type strain ATCC 700010T = MO739T) and Mycobacterium smegmatis sensu stricto for group 1 isolates.

Enteric infections and diarrhea in human immunodeficiency virus-infected persons: prospective community-based cohort study. Swiss HIV Cohort Study

BACKGROUND

Persons infected with human immunodeficiency virus (HIV) are at increased risk for diarrhea and enteric infections. We studied (1) the epidemiology of enteric pathogens associated with diarrhea, (2) the diagnostic yield of stool examination and endoscopic evaluation, (3) risks to develop diarrhea, and (4) the impact of diarrhea on patients' survival.

METHODS

A total of 1933 participants in the Swiss HIV Cohort Study were prospectively followed up for a median of 25.5 months. A total of 560 diarrheal episodes were evaluated by standardized stool examination. Endoscopic evaluation was performed in 25% of patients with chronic diarrhea.

RESULTS

The incidence of diarrhea was 14.2 per 100 person-years (95% confidence interval, 13.0-15.4). Among patients with CD4 cell counts below 0.05 x 10(9)/L, the probability to develop diarrhea within 1, 2, and 3 years was 48.5%, 74.3%, and 95.6%, respectively. The risk to develop diarrhea was increased among patients with severe immunodeficiency, homosexual men, and patients taking antiretroviral therapy. Pneumocystis carinii chemoprophylaxis did not reduce the risk of diarrhea. Diarrhea was an independent negative predictor of survival. Enteric pathogens were detected in 16.5% of 212 acute diarrheal episodes and in 46% of 348 chronic diarrheal episodes. The sensitivity of histological and stool examination was similar except for the diagnosis of intestinal cytomegalovirus infection and leishmaniasis, which required invasive evaluation.

CONCLUSIONS

Intestinal infections were diagnosed in less than 50% of chronic diarrheal episodes. The prevalence of enteric pathogens tended to decrease during the observation period, possibly because of improved antiretroviral therapy. Endoscopic evaluation did not improve the diagnostic yield compared with stool examination except for the diagnosis of cytomegalovirus enteritis and leishmaniasis.

Performance characteristics of the BDProbeTec system for direct detection of Mycobacterium tuberculosis complex in respiratory specimens

Strand displacement amplification (SDA) technology has been established in a fully automated system known as BDProbeTec. Target sequences of the insertion sequence IS6110 and the 16S rRNA gene are simultaneously amplified, which thus allows the detection of Mycobacterium tuberculosis complex and, as an additional option, of most Mycobacterium species. Detection occurs via a chemiluminescent microwell assay that employs the simultaneous hybridization and capture of SDA products with a biotinylated capture probe and an alkaline phosphatase detector probe. We have evaluated the performance of the BDProbeTec system in detecting M. tuberculosis complex by testing 799 respiratory specimens and comparing the results to those obtained by conventional diagnostic techniques, i.e. , microscopy and culture (solid and radiometric media). M. tuberculosis was cultivated from 41 specimens, of which 28 (68.4%) were smear positive and 13 (31.6%) were smear negative. The overall sensitivity of the SDA assay was 97.6% (for smear-positive specimens, 100%; for smear-negative specimens, 92.3%), and specificity was 95. 0%. After resolution of the discrepancies by studying the patients' clinical data, sensitivity and specificity were 97.9 and 96.5%, respectively, and positive and negative predictive values were 63.9 and 99.9%, respectively. These preliminary data demonstrate that the BDProbeTec system has promising performance characteristics with respiratory specimens and that it allows the detection of M. tuberculosis complex within hours.

Multicenter evaluation of the mycobacteria growth indicator tube for testing susceptibility of Mycobacterium tuberculosis to first-line drugs

In a multicenter study involving three reference centers for mycobacteria, the reliability of the Mycobacteria Growth Indicator Tube (MGIT) for rapid antimicrobial susceptibility testing (AST) of Mycobacterium tuberculosis was evaluated and compared to the radiometric method (BACTEC 460TB). Test cultures for which the results of the MGIT and BACTEC 460TB tests were discordant were checked by the conventional proportion method on solid medium. Four hundred forty-one isolates have been tested for susceptibility to isoniazid (INH), rifampin (RMP), ethambutol (EMB), and streptomycin (SM). Discrepant results were obtained for three isolates (0.7%) with INH (susceptible by MGIT, resistant by BACTEC 460TB), for four isolates (0.9%) with RMP (susceptible by MGIT, resistant by BACTEC 460TB), for six isolates (1.9%) with EMB (four susceptible by MGIT, resistant by BACTEC 460TB; two resistant by MGIT, susceptible by BACTEC 460TB), and for four isolates (0.9%) with SM (two susceptible by MGIT, resistant by BACTEC 460TB; two resistant by MGIT, susceptible by BACTEC 460TB). When cultures with discordant results were tested by the conventional proportion method, about half of the cultures yielded results similar to the BACTEC 460TB results, while the other half yielded results similar to the MGIT results. Turnaround times were 3 to 14 days (median, 8.8 days) for MGIT and 3 to 15 days (median, 7.8 days) for BACTEC 460TB. There was no statistically significant difference between the susceptibility testing results of the two methods (P > 0.05). These data demonstrate that the MGIT system is an accurate, nonradiometric alternative to the BACTEC 460TB method for rapid susceptibility testing of M. tuberculosis.

Rapid diagnosis of pulmonary tuberculosis with the LCx Mycobacterium tuberculosis assay and comparison with conventional diagnostic techniques

The LCx MTB amplification assay is a nucleic acid amplification test intended for the direct detection of Mycobacterium tuberculosis complex in respiratory specimens. We evaluated its performance on 2,001 consecutive respiratory specimens; 78 were culture positive for M. tuberculosis. Sensitivity, specificity, and positive and negative predictive values of this assay for all specimens compared to culture results were 88.5, 97.7, 60.5, and 99.5%, respectively. When referred to resolved clinical diagnosis of active tuberculosis, these values improved to 90.2, 98.4, 72.8, and 99.5%, respectively.

Drug resistant tuberculosis in prisons in Azerbaijan: case study

OBJECTIVES

To document the existence of drug resistance in a tuberculosis treatment programme that adheres strictly to the DOTS principles (directly observed treatment, short course) and to determine the extent of drug resistance in a prison setting in one of the republics of the former Soviet Union.

DESIGN

Case study.

SETTING

Central Penitentiary Hospital in Baku, the referral centre for tuberculosis patients from all prisons in Azerbaijan.

SUBJECTS

Prisoners with tuberculosis: 28 selected patients not responding clinically or bacteriologically to the standard treatment (group 1) and 38 consecutive patients at admission to the programme (group 2).

MAIN OUTCOME MEASURES

Drug resistance of Mycobacterium tuberculosis strains grown from sputum.

RESULTS

All the non-responding patients (group 1) had strains resistant to at least one drug. 25 (89%) of the non-responding patients and nine (24%) of the consecutive patients had M tuberculosis strains resistant to both rifampicin and isoniazid. A further 17 patients in group 2 had strains resistant to one or more first line drugs.

CONCLUSIONS

Drug resistant M tuberculosis strains are common in prisons in Azerbaijan. Tuberculosis problems tend to be worse in prisons, but prisoners and former prisoners may have an important role in the transmission of tuberculosis, particularly of drug resistant forms, in the community. National programmes to control tuberculosis will have to take into account and address the problems in prisons to ensure their success.

Transmission of tuberculosis in the metropolitan area of Zurich: a 3 year survey based on DNA fingerprinting

Between 1991 and 1993, 444 inhabitants of the metropolitan area of Zurich were reported as confirmed or suspected cases of tuberculosis (TB). Overall, isolates of Mycobacterium tuberculosis of 361 patients (90% of the bacteriologically confirmed cases) were available to study the frequency of transmission of the strains on a molecular level. Restriction fragment length polymorphism (RFLP) analysis was performed by using IS6110 and the polymorphic GC-rich sequence (PGRS) as genetic markers. Ninety nine isolates shared by 77 patients (21.3%) were associated with 28 IS6110-defined clusters. However, secondary typing of low copy number isolates decreased the number of clusters to 25, encompassing 81 isolates from 63 (17.5%) patients. By deoxyribonucleic acid (DNA) fingerprinting plus conventional contact tracing, definite transmission of TB was proven in only five patients (1.4%) and assumed in 20 patients (5.6%). In all other cluster-associated isolates, no epidemiological connections between the patients could be found using the clinical and sociodemographic data available. The present study demonstrates that in the time period studied only minor transmission occurred.

[Molecular pathologic detection of mycobacteria]

In recent years, significant advances in the diagnosis of mycobacterial infections have been made by the introduction of direct pathogen detection methods. These techniques are usually based on the polymerase chain reaction (PCR) or on a transcription-mediated amplification (TMA) process. The majority of the protocols have been optimized for the detection of mycobacterial nucleic acids in fresh fluid or fresh tissue specimen. Unfortunately pathologists are frequently confronted with the problem that tissues with histologically suspicious lesions have been entirely fixed in formalin. As a result of this routine fixation, DNA and RNA are heavily degraded and the usually high sensitivity of the amplification techniques is greatly impaired. Consequently, only PCR protocols designed for small amplification targets are still suitable for an efficient detection of microbial DNA in formalin-fixed and paraffin-embedded tissues. We therefore adapted PCR assays with amplification products < 200 bp for the detection of M. tuberculosis-complex DNA (targets: IS6110 and 65 kDa-antigen gene) in routine biopsies. Although the sensitivities of the two assays varied significantly with the degree of DNA degradation, we were able to detect M. tuberculosis-complex specific DNA in about 25% of the tissues with a granulomatous inflammation and negative Ziehl-Neelson stain. Recently, we have added a third PCR-assay, which in combination with direct sequencing also allows us to detect DNA from M. leprae and several atypical mycobacteria species. PCR-analysis has significantly improved the diagnosis of mycobacterial infections by supplementing conventional histological examination of formalin-fixed and paraffin-embedded tissues.

Mycobacterium canettii, the smooth variant of M. tuberculosis, isolated from a Swiss patient exposed in Africa

An exceptionally smooth and glossy morphotype of Mycobacterium tuberculosis complex was isolated from a 56-year-old Swiss patient with mesenteric tuberculosis. Direct 16S rRNA sequence analysis of the hypervariable signature gene regions revealed a 100% homology to the specific M. tuberculosis complex sequence. Spoligotyping and restriction fragment length polymorphism analyses using the insertion sequences IS6110 and IS1081 and the polymorphic GC-rich sequence as additional genetic markers identified the isolate as the novel taxon M. canettii. Like a Somali child with a similar case, this patient probably contracted the infection in Africa, which raises questions about the geographic distribution of M. canettii.

Role of embB in natural and acquired resistance to ethambutol in mycobacteria

The mycobacterial embCAB operon encodes arabinosyl transferases, putative targets of the antimycobacterial agent ethambutol (EMB). Mutations in embB lead to resistance to EMB in Mycobacterium tuberculosis. The basis for natural, intrinsic resistance to EMB in nontuberculous mycobacteria (NTM) is not known; neither is the practical implication of resistance to EMB in the absence of embB mutations in M. tuberculosis well understood. The conserved embB resistance-determining region (ERDR) of a collection of 13 strains of NTM and 12 EMB-resistant strains of M. tuberculosis was investigated. Genotypes were correlated with drug susceptibility phenotypes. High-level natural resistance to EMB (MIC, . or =64 microg/ml) was associated with a variant amino acid motif in the ERDR of M. abscessus, M. chelonae, and M. leprae. Transfer of the M. abscessus emb allele to M. smegmatis resulted in a 500-fold increase in the MICs. In M. tuberculosis, embB mutations were associated with MICs of > or =20 microg/ml while resistance not associated with an ERDR mutation generally resulted in MICs of < or =10 microg/ml. These data further support the notion that the emb region determines intrinsic and acquired resistance to EMB and might help in the reassessment of the current recommendations for the screening and treatment of infections with EMB-resistant M. tuberculosis and NTM.

Rapid detection of mycobacteria in clinical specimens by using the automated BACTEC 9000 MB system and comparison with radiometric and solid-culture systems

Recovery rates of acid-fast bacilli (AFB) and the mean time to their detection from clinical specimens were determined by using the fluorescent BACTEC 9000 MB system. Data were compared to those assessed by the radiometric BACTEC 460 system and by cultivation on solid media. A total of 3,095 specimens were processed with N-acetyl-L-cysteine-NaOH by two laboratories. The contamination rates for the BACTEC 9000 MB system were 6.8% (center 1) and 9.8% (center 2). A total of 451 mycobacterial isolates were detected (Mycobacterium tuberculosis complex, n = 296; nontuberculous mycobacteria [NTM], n = 155). These isolates originated from 94 (20.8%) smear-positive and 357 (79.2%) smear-negative specimens. The BACTEC 9000 MB system was significantly better than solid media (P < 0.05) in detecting AFB, but it was less efficient than the radiometric system (P < 0.01). The BACTEC 9000 MB system plus solid media (combination A) recovered 393 (87.1%) of the isolates, while the BACTEC 460 system plus solid media (combination B) detected 430 (95.3%) of all AFB isolates. Between combination A and B there was no statistically significant difference for the detection of isolates from smear-positive specimens (P > 0.05), in contrast to the recovery of AFB from smear-negative specimens for M. tuberculosis complex, P < 0.05; for NTM, P < 0.01). The mean time to detection of M. tuberculosis complex was 12.2 days for smear-positive specimens and 18.1 days for smear-negative specimens with the BACTEC 9000 MB system; 9.3 and 15.6 days, respectively, with the BACTEC 460 system; and 21.2 and 28.4 days, respectively, with solid media. For NTM, the average detection times were 15.1, 17.3, and 31.3 days by the three methods, respectively. In conclusion, the BACTEC 9000 MB system is a rapid, less labor-intensive detection system which allows for higher levels of recovery of AFB than solid media. There is no risk of cross contamination, which is known to be the case for the BACTEC 460 system, and data management is greatly facilitated. As a whole, however, the BACTEC 9000 MB system should only be used in conjunction with solid media.

Pretreatment of clinical specimens with sodium dodecyl (lauryl) sulfate is not suitable for the mycobacteria growth indicator tube cultivation method

When using the Mycobacteria Growth Indicator Tube (MGIT), pretreatment of clinical specimens with N-acetyl-L-cysteine-NaOH is recommended by the manufacturer. Processing of clinical specimens (n = 1,000) with sodium dodecyl (lauryl) sulfate-NaOH resulted in both poor recovery and delayed mean time to detection of acid-fast bacilli. Values were comparable to those obtained on solid media.

Mycobacterium smegmatis infection in a healthy woman following a facelift: case report and review of the literature

In a 35-year-old female HIV-negative patient a facelift was followed by a Pseudomonas aeruginosa wound infection. The infection persisted despite treatment with ciprofloxacin, and an additional bacteriological wound examination revealed Mycobacterium smegmatis as the causative agent. Combination therapy with ciprofloxacin, doxycycline and amikacin led to a slow healing process without the need for further surgical intervention. A relapse 6 months after initial therapy was successfully treated with local measures. Infection with M. smegmatis might have come about by contaminated intraoperative liquids or the application of lipid creams to the open wound. However, microbiological examination of potential sources remained negative. Infection caused by M. smegmatis following plastic surgery should be considered in patients with spontaneous ulceration and violaceous discoloration of the skin adjacent to the surgical wound. Prolonged antibiotic therapy and possibly repeat surgical interventions may become necessary to treat this rare infection.

Molecular epidemiology of Mycobacterium tuberculosis strains isolated from patients in a human immunodeficiency virus cohort in Switzerland

From 1989 to 1995, 46 patients infected with the human immunodeficiency virus were diagnosed with tuberculosis at the University Hospital in Zurich. Using the IS6110 insertion sequence as a genetic marker, restriction fragment length polymorphism analyses were done for 52 Mycobacterium tuberculosis isolates. We have found a large degree of IS6110 polymorphism, ranging from 1 to 16 copies. For isolates from patients from whom multiple isolates had been available, the IS6110 pattern remained virtually stable over a period of up to 4 years, as well as during emerging drug resistance. In none of the cases was a reinfection of a patient with another strain detected. For isolates from 10 patients we detected identical patterns which could be associated with four clusters. In one of these, the strains exhibited a low IS6110 copy number (four bands), and the strains were further analyzed by hybridizing with (i) the polymorphic GC-rich repetitive sequence (PGRS) and (ii) the 36-bp direct-repeat (DR) cluster sequence. One of these isolates had a different pattern with the PGRS as well as with the DR sequence and could therefore be safely excluded from that cluster. These findings point to the importance of applying more than one genetic criterion in the molecular biological study of strain relatedness.

Comparison of the Mycobacteria Growth Indicator Tube (MGIT) with radiometric and solid culture for recovery of acid-fast bacilli

In a multicenter study involving three reference centers for mycobacteria, the rate of recovery of acid-fast bacilli (AFB) and the mean time to their detection from clinical specimens was determined by using the Mycobacteria Growth Indicator Tube (MGIT). These parameters were compared to those assessed by the radiometric BACTEC 460 TB system and by cultivation on solid media. Clinical specimens (n = 1,500) were pretreated with N-acetyl-L-cysteine (NALC)-NaOH. The contamination rates for MGITs were 2.0% (center 1), 13.8% (center 2), and 6.1% (center 3). A total of 180 mycobacterial isolates were detected (M. tuberculosis complex, n = 113; nontuberculous mycobacteria [NTM], n = 67). When using a combination of liquid and solid media (the current "gold standard" for culture), MGIT plus solid media detected 156 (86.7%) of the isolates, whereas BACTEC plus solid media recovered 168 (93.3%) of all AFB. Between these two gold standards there was no statistically significant difference (P > 0.05). The combination of MGIT plus BACTEC detected 171 (95.0%) of all isolates (compared with MGIT plus solid media, P < 0.01; compared with BACTEC plus solid media, P > 0.05). Considering the efficacies of the different media separately, MGIT was superior to solid media (although not significantly; P > 0.05) in detecting AFB but was inferior to the BACTEC system (P < 0.01). The mean time to the detection of M. tuberculosis complex was 9.9 days with MGIT, 9.7 days with BACTEC, and 20.2 days with solid media. NTM needed, on average, 11.9, 13.0, and 22.2 days to appear by the three methods, respectively. In conclusion, MGIT proved to be a valuable alternative to the radiometric cultivation system.

[Cervical lymphadenitis in an immunocompetent patient: Mycobacterium gordonae as the cause?]

HISTORY AND FINDINGS

A 76-year-old man went to an ENT outpatient clinic because of stabbing pain in the left throat and difficult swallowing. He was found to have tonsillitis on the left and cervical lymphadenitis. The symptoms regressed on treatment with amoxycillin and clavulanic acid, but the cervical lymphadenitis persisted. Fine-needle biopsy of the cervical swelling was not diagnostic. Computed tomography of the neck showed an encapsulated liquid space-occupying lesion with infiltration of surrounding soft tissues.

TREATMENT AND COURSE

The cervical lymph-node mass was excised and histologically found to contain epithelioid granulomas with a few giant cells and scattered centrally caseous necroses. Tuberculostatic treatment was started; drainage fluid from the wound grew acid-fast bacilli, identified by gene probe as Mycobacterium gordonae.

CONCLUSIONS

Mycobacterium gordonae is ubiquitous in the environment and is being identified ever more frequently in microbiological laboratories, usually as contaminant. It rarely causes infections of soft tissues and the lungs or systemically.

[Tuberculosis therapy in canton Zurich 1991-1993: what are the causes for recurrence and therapy failure?]

A retrospective cohort analysis of TB patients in the Canton of Zurich was undertaken to evaluate the effectiveness of a primary care physician-based tuberculosis treatment program in the Canton of Zurich (1991-1993) and compare it with treatment results in selected patient groups in controlled prospective studies. Of the 440 TB patients (62.5% men, 51% foreign born, 9.6% with HIV infection) 65% were initially hospitalized. The total treatment duration was 210 (+/-108) days on average. Only 75% of the patients who were treated by a total of 410 hospital and primary care physicians were treated with standard regimens according to guidelines. 3 patients were treatment failures; 13 relapsed (5.1% of the 257 patients reexamined in 1995). Possible causes for relapses were poor patient compliance due to alcoholism, homelessness, drug addiction, psychiatric disorders; prescription errors with inadequate treatment durations, concurrent AIDS disease, or use of a three-drug combination despite primary drug resistance. In 4 of the relapse patients and in all 3 treatment failures, secondary drug resistance developed under treatment. 5 of these 7 patients were treated initially only with a fixed three-drug regimen (Rifater). The relatively high INH resistance rate (8.6%) and relapse rate (5.1%) in the Canton of Zurich renders the use of a four-drug combination therapy necessary. In the outpatient maintenance phase, more effort must be devoted to ensuring patient compliance and adherence to a proper treatment duration. This should be documented by a standardized questionnaire at 6 or 12 months after initiation of therapy. In high risk patients in particular, home care visits by a TB nurse in addition to consultations by primary care physicians are necessary to ensure directly observed therapy (DOT) in order to prevent relapses and treatment failures.

[Extrapulmonary infections with Mycobacterium tuberculosis complex]

In a retrospective study we reviewed all records of patients with newly diagnosed Mycobacterium tuberculosis complex infection during the years 1990-1994. Of the 45 patients identified, 27 (60%) had only pulmonary tuberculosis and 18 (40%) had extrapulmonary tuberculosis with (5 patients, 11%) or without (13 patients, 18%) concomitant pulmonary infection. The extrapulmonary manifestations were as follows: miliary 5, joint 3, meningeal 2, pleural 2, kidney 1, peritoneal 1, bone 1, psoas 1, lymphatic 1, and anal 1. In the 18 patients with extrapulmonary tuberculosis the infection was due to Mycobacterium tuberculosis 14 times, Mycobacterium bovis twice, and Mycobacterium bovis BCG once.

Isolation of Arthrobacter spp. from clinical specimens and description of Arthrobacter cumminsii sp. nov. and Arthrobacter woluwensis sp. nov

Arthrobacter spp. are very widely distributed in the environment (e.g., soil) but have not been described as causing disease in humans. Over a 6-year period, two reference laboratories isolated or received 11 strains which were eventually identified as belonging to the genus Arthrobacter. These strains had been initially identified as Centers for Disease Control and Prevention coryneform group B-1 and B-3 bacteria (whitishgrayish colonies of 2 mm or greater in diameter after 24 h of incubation, respiratory metabolism, absent or weak acid production from sugars, and hydrolysis of gelatin). However, chemotaxonomic investigations revealed lysine as the diamino acid of the cell wall and the presence of branched cellular fatty acids (with anteiso-pentadecanoic acid predominating) which was compatible with an assignment of the 11 isolates to the genus Arthrobacter only. Peptidoglycan and 16S rRNA gene sequence analyses demonstrated that three of the strains studied were representatives of a new Arthrobacter species for which the name Arthrobacter cumminsii sp. nov. is proposed and that one other strain represented a second new Arthrobacter species for which the name Arthrobacter woluwensis sp. nov. is proposed. This report is the first on the isolation of Arthrobacter spp. from clinical specimens.

[Mycobacterium haemophilum infection in a patient with AIDS]

HISTORY AND FINDINGS

A 35-year-old HIV-infected man with a CD4 cell count of 100/microliter who had returned from a holiday in Spain presented with fever, chronic diarrhoea, cough, oral ulcers, subcutaneous nodules of about 1 cm in diameter and crusted skin ulcers of about 2 cm in diameter at his right arm, both wrists and buttocks.

INVESTIGATIONS

Microscopic examination and culture of smears of a skin ulcer revealed acid-fast bacteria. Mycobacterial cultures of blood, sputum, urine and stool remained sterile.

TREATMENT AND COURSE

Before the microorganisms were identified culturally, atypical mycobacteriosis was assumed and treatment with rifampicin, ethambutol, isoniazid and clarithromycin was started. Mycobacterium haemophilum was identified by using molecular biological techniques. Within 3 weeks the patient became afebrile and the skin ulcers healed completely. After a 7-week course, the treatment had to be stopped, and one month later painful subcutaneous nodules developed again at his arms and legs. A relapse of Mycobacterium haemophilum infection was confirmed by culture of a fine needle aspirate of a nodule. The same treatment was restarted and the nodules disappeared.

CONCLUSIONS

Mycobacterium haemophilum, first identified in 1978, is an emerging pathogen in immunocompromised patients. Clinical manifestations usually are skin ulcers, subcutaneous nodules and subcutaneous abscesses, and less frequently, systemic infection. Treatment options of this life threatening disease have yet to be defined but therapeutic response to tuberculostatic combination therapy has been observed. Since Mycobacterium haemophilum is a fastidious organism, special laboratory methods are required for cultivation as well as for identification.

Utility of PCR in diagnosing pulmonary tuberculosis

At present, the rapid diagnosis of pulmonary tuberculosis rests with microscopy. However, this technique is insensitive and many cases of pulmonary tuberculosis cannot be initially confirmed. Nucleic acid amplification techniques are extremely sensitive, but when they are applied to tuberculosis diagnosis, they have given variable results. Investigators at six centers in Europe compared a standardized PCR system (Amplicor; Roche) against conventional culture methods. Defined clinical information was collected. Discrepant samples were retested, and inhibition assays and backup amplification with a separate primer pair were performed. Mycobacterium tuberculosis complex organisms were recovered from 654 (9.1%) of 7,194 samples and 293 (7.8%) of 3,738 patients. Four hundred fifty-two of the M. tuberculosis isolates from 204 patients were smear positive and culture positive. Among the culture-positive specimens, PCR had a sensitivity of 91.4% for smear-positive specimens and 60.9% for smear-negative specimens, with a specificity of 96.1%. Analysis of 254 PCR-positive, culture-negative specimens with discrepant results revealed that 130 were from patients with recently diagnosed tuberculosis and 94 represented a presumed laboratory error. Similar analysis of 118 PCR-negative, culture-positive specimens demonstrated that 27 discrepancies were due to presumed uneven aliquot distribution and 11 were due to presumed laboratory error; PCR inhibitors were detected in 8 specimens. Amplicor enables laboratories with little previous experience with nucleic acid amplification to perform PCR. Disease in more than 60% of the patients with tuberculosis with smear-negative, culture-positive specimens can be diagnosed at the time of admission, and potentially all patients with smear-positive specimens can immediately be confirmed as being infected with M. tuberculosis, leading to improved clinical management.

Isolation and characterization of a unique group of slowly growing mycobacteria: description of Mycobacterium lentiflavum sp. nov

A distinct group of slowly growing mycobacteria was identified on the basis of growth characteristics, biochemical and lipid profiles, and nucleic acid analyses. The isolates showed growth at 22 to 37 degrees C, yellow pigmentation, and negative tests for Tween 80 hydrolysis, nicotinic acid, nitrate reductase, and urease; tests for arylsulfatase, pyrazinamidase, and heat-stable catalase were variable. Analysis of cellular fatty acids by gas-liquid chromatography and mycolic acids by thin-layer chromatography and high-performance liquid chromatography indicated a distinctive pattern which was unlike those of other species. Determination of the 16S rRNA gene sequence showed a unique sequence closely related to Mycobacterium simiae and M. genavense. On the basis of DNA homology studies, we suggest that these organisms are representatives of a novel species, for which the name M. lentiflavum sp. nov. is proposed.

Etiological agents of mycobacterioses in pet birds between 1986 and 1995

Between May 1986 and June 1995, mycobacteriosis was diagnosed by histology and microscopy in 204 (3.8%) of 5,345 necropsied pet birds. The predominant macroscopic changes were enlargement of the liver and spleen and thickening of intestinal walls. Attempts to cultivate mycobacteria were made in 110 cases. Acid-fact bacilli grew in 66 specimens (60%) only. In 18 cases we failed to obtain subcultures. Therefore, species identification could be performed for only 48 isolates. Identification was carried out by conventional biochemical tests as well as by PCR-mediated sequencing of the 16S rRNA gene. The majority of the isolates were Mycobacterium genavense (34 isolates), followed by M. avium complex (8), M. fortuitum (2), M. tuberculosis (2), M. gordonae (1), and M. nonchromogenicum (1). The significance of M. genavense as a zoonotic agent remains to be determined.

Diagnostic performance of amplified Mycobacterium tuberculosis direct test with cerebrospinal fluid, other nonrespiratory, and respiratory specimens

The Gen-Probe Amplified Mycobacterium tuberculosis Direct Test (MTD) was adapted to be used for cerebrospinal fluid (CSF) and a large variety of other nonrespiratory specimens. Standardized with artificially spiked dilution series of CSF, the modified MTD procedure consists of (i) increasing the amount of sample 10-fold, (ii) pretreating the specimen with a detergent, and (iii) increasing the amplification time from 2 to 3 h. Performance of MTD in a clinical mycobacteriology laboratory was tested over an extended period of time, involving a total of 322 nonrespiratory as well as 1,117 respiratory specimens from 998 patients. Results from MTD were compared with those from microscopy, culture, analysis of tuberculostearic acid by gas-liquid chromatography-mass spectrometry (CSF only), and the final clinical diagnosis. When MTD results were compared with resolved data, the sensitivity, specificity, and positive and negative predictive values for MTD were 93.1, 97.7, 90.0, and 98.5%, respectively, for nonrespiratory specimens and 86.6, 96.4, 76.8, and 98.1%, respectively, for respiratory specimens. Our data demonstrate that (i) MTD is a robust, highly sensitive and specific technique for the rapid detection of M. tuberculosis complex in all types of clinical specimens, (ii) there was no statistically significant difference (P > 0.005) in sensitivity and specificity for nonrespiratory compared with respiratory specimens, and (iii) repeating all MTDs which yield a result between 30,000 and 200,000 relative light units would help prevent a large number of false positives and, thus, enhance test specificity.

Treatment of nontuberculous mycobacterial lymphadenitis with clarithromycin plus rifabutin

Treatment with clarithromycin plus rifabutin in children with nontuberculous mycobacterial lymphadenitis was associated with resolution of chronic sinus formation and discharge after incomplete excision in five of five cases, and involution of the enlarged lymph nodes in two of three cases treated without surgery.