Clinical significance of isolation of nontuberculous mycobacteria in pulmonary tuberculosis patients

Nontuberculous mycobacteria isolation from sputum specimens: A retrospective analysis of 1061 cases

Background

In recent years, with the development of laboratory methods, the frequency of nontuberculosis mycobacteria (NTM) infections has increased. The primary aim of this study was to evaluate the clinical significance of therapeutic drug monitoring (TDM) growths in respiratory samples, and the secondary aim was to evaluate the treatment regimens and treatment outcomes of treatment for TDM disease.

Methods

This study was a retrospective cohort study. Persons with NTM growth in respiratory samples admitted to the reference hospital between 2009 and 2020 were included in this study. Samples detected as NTM by the immunochromatographic rapid diagnostic test, those requested by the clinicians, species were determined by the hsp65PCRREA method. The subjects were classified into 3 groups: patients with NTM infection who received treatment (135, 12.7%), those followed up without treatment (690, 65.1%), and a last group of patients with Mycobacterium tuberculosis (TB) complex strains were isolated and received TB treatment (236, 22.2%). Initiating NTM treatment was decided in accordance with the American Thoracic Society recommendations.

Results

The mean ± standard deviation age of patients was 53.8 ± 16.5 years, and 749 (70.6%) were male. In total, 278 (26.2%) out of 1061 cases had identified, and the most frequent species were MAC (81; Mycobacterium avium: 39, Mycobacterium intracellulare: 39, and MAC: 3), Mycobacterium abscessus (67), Mycobacterium kansasii (48), Mycobacterium fortuitum (23), Mycobacterium chelonae (12), Mycobacterium gordonae (11), and Mycobacterium szulgai (11). In the NTM treatment group, 116 (85.9%) of 135 patients had multiple culture positivity. Previous TB treatment history had 51 (37.8%) of 135 patients, respiratory comorbidities were evident in 37 (27.4%) of 135 patients. Thorax computed tomography imaging in 84 patients revealed nodule 38 (45.2%), consolidation 46 (54.8%), cavity 52 (61.9%), and bronchiectasis 27 (32.1%). Treatment results in the NTM treatment group were as follows: ongoing treatment 14 (10.4%), cure 64 (47.4%), default 33 (24.4%), exitus 19 (14.1%), recurrence 3 (2.2%), and refractory disease 2 (1.5%).

Conclusion

This is a large case series evaluating the clinical significance of NTM growths and NTM treatment in Turkey. The clinical significance of NTM growth in respiratory samples is low. Treatment success rates of NTM patients who are treated are low. Treatment defaults and mortality rates are high. New drugs and new regimens are needed.

Surgical Treatment of Nontuberculous Mycobacterial Pulmonary Disease and a Combination of Nontuberculous Mycobacterium Pulmonary Disease and Pulmonary Tuberculosis

OBJECTIVES

Nontuberculous mycobacterial pulmonary disease (NTMPD) is an important health system problem worldwide. Surgical treatment experience is limited, and the safety of such operations is still unclarified. Therefore, improving our knowledge of NTMPD is important.

DESIGN

In this retrospective observational study, we analyzed the medical records of 2,432 patients operated on from January 2011 through December 2017 in our hospital. There were 20 patients with NTMPD in group 1 and 23 patients with combined NTMPD and pulmonary tuberculosis in group 2. Patients received antibiotic treatment before and after surgery as per Russian Federal clinical guidelines and individual drug susceptibility.

RESULTS

Postoperative complications occurred in 2 (10%) cases in group 1 and 4 (17.4%) in group 2, and intraoperative complications occurred in 2 (8.7%) cases in group 2. There was no 30-day mortality in both groups. After 1 year, all 40 traced patients had neither bacterial excretion nor cavities in the lungs. After 3 years and 5 years, the efficacy among 32 and 13 traced patients was 100%, respectively.

CONCLUSIONS

Modern surgery for small NTMPD forms is safe - helping improve outcomes for ineffective antibiotic treatment. Combined surgery and antibiotic treatment are acceptable in both the short and long term.

Changes in chest X-ray findings in 1- and 2-month group after treatment initiation for suspected pulmonary tuberculosis

BACKGROUND/AIMS

Although re-evaluation of radiographic follow-up after 2 to 3 months of therapy is recommended for patients administered anti-tuberculosis medication owing to suspected pulmonary tuberculosis, reported findings are limited. Therefore, this study aimed to investigate changes in 1- and 2-month chest X-ray (CXR) findings after the treatment initiation and compared them according to the final diagnosis of tuberculosis or non-tuberculosis.

METHODS

Patients who started anti-tuberculosis medication for suspected pulmonary tuberculosis were selected at a tertiary referral hospital in South Korea between January 2012 and December 2015. Changes in the 1- and 2-month CXR findings were classified as improved, unchanged, and aggravated.

RESULTS

Among the 120 patients enrolled in the 1-month CXR group, 76 (63.3%) had the final diagnosis of tuberculosis. Comparison between the 1-month CXR changes and diagnosis showed that the final diagnosis was tuberculosis in 81.8% (45/55), 50.0% (26/52), and 38.5% (5/13) of patients whose 1-month CXR was improved, unchanged, and aggravated, respectively. In the 2-month CXR group, 167 patients were enrolled, and 139 (83.2%) of them were diagnosed with tuberculosis. Tuberculosis was the final diagnosis in 92.6% (100/108), 70.0% (35/50), and 44.4% (4/9) patients with improved, unchanged, and aggravated 2-month CXR findings, respectively. In patients with the final diagnosis of non-tuberculosis, nontuberculous mycobacteria and malignancy were the most common causes of improved and aggravated 1- and 2-month CXR findings, respectively.

CONCLUSION

Two-month CXR findings were of limited value for deciding on whether to continue anti-tuberculosis treatment. One-month CXR findings could help determine the need for further work-up.

Nontuberculous mycobacterial lung disease epidemiology in Taiwan: A systematic review

Nontuberculous mycobacteria (NTM) are critical emerging global infectious pathogens. Though NTM can be mere colonizers when isolated from human specimens, NTM are also responsible for diverse human infections. NTM-lung disease (NTM-LD) is the most common human disease entity. The present review aims to provide general insight into NTM-LD epidemiology in Taiwan. In reviewing NTM epidemiology in Taiwan, we discovered three distinguishing features. First, NTM disease incidence has increased in Taiwan over the past decade. Second, the distribution of NTM varies geographically in Taiwan. Mycobacterium avium-intracellulare complex (MAC) is the dominant species in northern Taiwan, whereas Mycobacterium abscessus complex and MAC may be equally dominant in southern Taiwan. Third, researchers in Taiwan have published valuable research investigating NTM among special patient populations, including patients in intensive care units, with ventilator dependency, with pulmonary tuberculosis, and who are infected with specific NTM species. The largest obstacle to clarifying NTM epidemiology in Taiwan may be the lack of routine NTM species identification in laboratories. Increased awareness of NTM diseases and acknowledgment that NTM species identification is crucial and guides clinical management are essential steps for facilitating the identification of NTM species in laboratories.

Host immune response against environmental nontuberculous mycobacteria and the risk populations of nontuberculous mycobacterial lung disease

Nontuberculous mycobacterial lung disease (NTM-LD) prevalence has been increasing over the recent decades. Numerous host factors are associated with NTM-LD development, including susceptible phenotypes such as ciliary defect and lung structural change, pulmonary clearance defect with poor clearance of secretions, and immune suppression. Specifically, regarding the susceptible host phenotypes without clear pathogenesis, a slender body, pectus excavatum, and postmenopausal female status are common. Also, decreased host immunity to NTM, especially T helper 1 cell responses is frequently observed. Even so, the underlying mechanisms remain unclear and relevant large-scale studies are lacking. Infections due to host genetics associated defects are mostly untreatable but rare in Asia, particularly Taiwan. Nevertheless, some risks for NTM-LD are controllable over disease progression. We suggest that clinicians first manage host factors and deal with the controllable characteristics of NTM-LD, followed by optimizing anti-NTM treatment. Further researches focusing on NTM-LD pathogenesis, especially the host-NTM interaction may advance understanding the nature of the disease and develop efficient therapeutic regimens.

Evaluation of GeneXpert MTB/RIF for determination of rifampicin resistance among new tuberculosis cases in west and northwest Iran

Despite a Mycobacterium tuberculosis control programme and anti-tuberculosis drugs, drug-resistant tuberculosis (DR-TB) is one of the most serious public health issues worldwide. Rapid laboratory diagnosis of M. tuberculosis is needed for the diagnosis of multidrug-resistant (MDR) TB and to find the optimal treatment protocol. The purpose of this study was to detect resistance to rifampicin in new cases of TB using the GeneXpert MTB/RIF (M. tuberculosis/rifampicin) assay and the standard proportional method in west and northwest Iran. In this descriptive cross-sectional study, sputum samples were enrolled and screened for M. tuberculosis using Ziehl–Neelsen stain and mycobacterial culture. Samples from individuals with smear-positive TB were cultured on Lowenstein–Jensen medium; afterwards, the presence of resistance to rifampicin was examined by the GeneXpert MTB/RIF and standard proportional methods. A total of 400 new cases of suspected TB were collected, 162 (40.5%) of which were smear- and culture-positive for M. tuberculosis. The frequencies of rifampicin resistance in new smear-positive TB cases were 3.1% and 4.3% for GeneXpert and standard proportional method, respectively. Sensitivity and specificity of GeneXpert were 71% and 100%, respectively, compared with the proportional method. GeneXpert can be a quick and helpful method for the diagnosis of rifampicin-resistant TB in regions with high rates of DR-TB or MDR-TB. GeneXpert MTB-RIF assay must be used as an early diagnostic method whose results must be confirmed by the standard proportional method. The GeneXpert and proportional methods complement but do not replace each other.

Nontuberculous mycobacteria among pulmonary tuberculosis patients: a retrospective Belgian multicenter study

OBJECTIVES

Currently, there are no European data about the frequency and clinical significance of nontuberculous mycobacteria (NTM) grown from respiratory samples during the treatment of tuberculosis (TB). We determined the frequency and clinical significance of NTM isolated before or during pulmonary tuberculosis treatment in Belgian laboratories.

METHODS

We conducted a nationwide retrospective multicenter cohort study on the co-isolation of TB and NTM in Belgium. Starting from laboratory data between 2006 and 2013, possible TB-NTM co-isolations were searched for.

RESULTS

A total of 2569 unique culture-positive pulmonary tuberculosis cases were included in the study. Only 35 (1.4%) of these TB cases had an NTM co-isolated, and two of these 35 fulfilled the ATS criteria for NTM lung disease.

CONCLUSION

A very low prevalence of 1.4% NTM co-isolations was found in Belgian patients with culture-proven pulmonary TB.

Clinical significance of smear positivity for acid-fast bacilli after ≥5 months of treatment in patients with drug-susceptible pulmonary tuberculosis

Patients with pulmonary tuberculosis (TB) with acid-fast bacilli (AFB)-positive sputum smear at 5 months or later during treatment are considered to be cases of treatment failure according to World Health Organization guidelines. This study evaluated the proportion, clinical characteristics, and significance of positive sputum smears after ≥5 months of standard treatment in patients with drug-susceptible pulmonary TB.This was a retrospective cohort study of 1611 patients with culture-confirmed drug-susceptible pulmonary TB who received standard anti-TB treatment from January 2009 to February 2014. Forty-one patients (2.5%) who were smear-positive after ≥5 months of treatment and 123 age- and sex-matched control patients were evaluated.Among the 41 smear-positive patients, culture of the sputum specimens yielded Mycobacterium tuberculosis (MTB) in 1 patient (2.4%), nontuberculous mycobacteria (NTM) in 7 (17.1%), and no growth in the remaining 33 patients (80.5%). Treatment was successfully completed in 40 patients (97.6%) with prolongation of the continuation phase regimens without change to second-line anti-TB treatment. In patients with smear positivity after ≥5 months of treatment compared with controls, cavitation on chest radiographs (53.7% vs. 25.2%, P = 0.001), bilateral involvement (51.2% vs. 30.1%, P = 0.01) and combined pleural effusion (26.8% vs. 10.6%, P = 0.01) were found more frequently at the time of treatment initiation, and paradoxical response occurred more commonly (19.5% vs. 3.3%, P = 0.002) during treatment.Smear-positive sputum after ≥5 months of standard anti-TB treatment was mainly because of nonviable MTB bacilli or NTM in patients with drug-susceptible pulmonary TB. AFB smear alone should not be used to assess treatment failure and careful examination of microbiologic status, including culture and drug susceptibility testing, is needed before making changes to retreatment regimens or empirical second-line anti-TB regimens in these patients.

Prevalence and species spectrum of both pulmonary and extrapulmonary nontuberculous mycobacteria isolates at a tertiary care center

OBJECTIVE/BACKGROUND

Nontuberculous mycobacteria (NTM) infection associated with pulmonary and extrapulmonary disease has been increasing globally. Despite an increase in incidence rate of NTM infection, its prevalence, species diversity, and circulation pattern in India is largely unknown. This study sought to investigate the overall burden and diversity of NTM among both pulmonary and extrapulmonary clinical isolates from a Northern Indian population.

METHODS

The study was conducted in the Department of Microbiology, from January 2013 to December 2015. A total of 4620 clinical samples were collected from patients suspected to have pulmonary and extrapulmonary tuberculosis. Preliminary diagnosis was performed using Ziehl-Neelsen staining followed by liquid culture in BacT/ALERT three-dimensional system. A total of 906 positive cultures obtained were differentiated as either NTM or Mycobacterium tuberculosis complex using a biochemical and MPT64 antigen test. Further identification of NTM species was confirmed with a line probe assay.

RESULTS

Out of 906 cultures isolates, 263 (29.0%) were confirmed as NTM and 643 (71.0%) were identified as Mycobacterium tuberculosis complex. A total of 79.4% of the NTM were recovered from pulmonary and 18.2% from extrapulmonary specimens. The diversity of NTM species was high (13 species) and predominated by Mycobacterium abscessus (31.3%) followed by Mycobacterium fortuitum (22%), Mycobacterium intracellulare (13.6%), Mycobacterium chelonae (9.1%), however, M. abscessus and M. fortuitum were the predominant species in both types of clinical isolates. Men (60.4%) and older patients aged greater than 55years were the predominated risk group for NTM infection.

CONCLUSION

The high prevalence and species diversity of NTM suggests the need for immediate and accurate characterization of NTM for proper treatment and management of patients.

Health-related quality of life, comorbidities and mortality in pulmonary nontuberculous mycobacterial infections: A systematic review

Nontuberculous mycobacterial (NTM) infections are increasing in disease frequency worldwide. This systematic review examines health-related quality of life (HRQOL), comorbidities and mortality associated with pulmonary NTM disease. We searched MEDLINE, EMBASE, CINAHL, Scopus Life Sciences, conference proceedings and Google (earliest date available to February 2015) for primary studies. Eligible studies compared populations with and without pulmonary NTM disease in high-income jurisdictions. We excluded studies on HIV/AIDS. All languages were accepted. Two reviewers followed MOOSE and PRISMA reporting guidelines and independently appraised quality using STROBE. All studies were summarized qualitatively regardless of quality. Of 3193 citations screened, we included 17 studies mostly from Taiwan (n = 5) and the USA (n = 4). Two studies assessed HRQOL; one assessed comorbidities, 11 assessed mortality, and three assessed multiple outcomes. Populations with pulmonary NTM reported significantly worse or similar HRQOL than the general population, depending on the instruments used. Some suggested greater prevalence of having bronchiectasis (n = 2) and greater risk of developing pulmonary tuberculosis (n = 1). Most (n = 7) suggested no difference in mortality, although only one was age-matched and gender-matched to the general population. Four suggested NTM populations had higher mortality-two of which compared with the general population and were deemed of high quality, while two compared with non-NTM patients from hospital. High clinical heterogeneity in study design may explain discordant results. Bias assessments and controlling for confounding were carried out poorly. No consistent trends were observed although there is suggestion of an increased health burden from respiratory diseases and increased mortality associated with pulmonary NTM disease.

The significance of Mycobacterium abscessus subspecies abscessus isolation during Mycobacterium avium complex lung disease therapy

BACKGROUND

Isolation of Mycobacterium abscessus subspecies abscessus (MAA) is common during Mycobacterium avium complex (MAC) lung disease therapy, but there is limited information about the clinical significance of the MAA isolates.

METHODS

We identified 53 of 180 patients (29%) treated for MAC lung disease who had isolation of MAA during MAC lung disease therapy. Patients were divided into those without (group 1) and those with (group 2) MAA lung disease.

RESULTS

There were no significant demographic differences between patients with and without MAA isolation or between groups 1 and 2. Group 1 and 2 patients had similar total sputum cultures obtained (P = .7; 95% CI, -13.4 to 8.6) and length of follow-up (P = .8; 95% CI, -21.5 to 16.1). Group 2 patients had significantly more total positive cultures for MAA (mean±SD, 15.0 ± 11.1 vs 1.2 ± 0.4; P < .0001; 95% CI, -17.7 to -9.9), were significantly more likely to develop new or enlarging cavitary lesions while on MAC therapy (P > .0001), and were significantly more likely to meet all three American Thoracic Society diagnostic criteria for nontuberculous mycobacterial disease (21 of 21 [100%] vs 0 of 32 [0%]; P < .0001) compared with group 1 patients. Group 1 patients were significantly more likely to have single, positive MAA cultures than group 2 patients (25 of 31 vs 0 of 21; P < .0001).

CONCLUSIONS

Microbiologic and clinical follow-up after completion of MAC lung disease therapy is required to determine the significance of MAA isolated during MAC lung disease therapy. Single MAA isolates are not likely to be clinically significant.

"Multidrug-resistant tuberculosis" may be nontuberculous mycobacteria

INTRODUCTION

Multidrug resistant tuberculosis (MDR-TB) presents a great challenge to public health, especially for developing countries. Some nontuberculous mycobacteria (NTM) cause the similar clinical and radiological characteristics with tuberculosis. We aimed to identify the frequency of NTM infections among subjects who were suspected to have MDR-TB due to lack of response to anti-TB treatment.

METHODS

This retrospective study evaluated patients with suspected MDR-TB due to lack of sputum conversion after 2-3 month therapy with first line anti-TB treatment from 2009 through 2014. Cultures for mycobacteria were performed and identification was done to species level by phenotypic and molecular tests. The outcome of the patients with NTM disease and related risk factors for poor outcome were evaluated.

RESULTS

Out of 117 consecutive strains isolated from suspected MDR-TB subjects, 35 (30%) strains were identified as NTM by using conventional and molecular approaches. Of these patients with positive NTM cultures, 32 (27%) patients met ATS/IDSA diagnostic criteria. Out of 32, 29 (90%) individuals with confirmed NTM diseases had underlying disorders including 8 subjects with malignancy, 5 with organ transplantations, and 4 with the human immunodeficiency virus. No known underlying disorder was found in 3 (9%) subjects. Treatment outcomes were available for 27 subjects, 17 (63%) of whom were cured and 10 (37%) had poor outcome including 6 (60%) who failed and 4 (40%) who died during treatment.

CONCLUSION

The high costs to the patient and society should lead health care providers to consider NTM in all patients suspected of having TB.

Prevalence of nontuberculous mycobacteria among extrapulmonary tuberculosis cases in tertiary care centers in Northern India

The reports of nontuberculous mycobacteria (NTM) associated with extrapulmonary diseases are increasing in tertiary care hospitals. Despite a significant increase in knowledge about NTM infections, they still represent a diagnostic and therapeutic challenge. The aim of this study is to know the prevalence of NTN among extrapulmonary tuberculosis cases in tertiary care centers in Northern India. A total of 227 culture positive isolates from 756 cases were tested for niacin production and catalase assay. BIO-LINE SD Ag MPT64 TB test and final identification and differentiation between MTBC and different species of NTM were further confirmed by GenoType Mycobacterium CM/AS assay. 71 cases (9.3%) were positive for AFB by ZN staining and 227 cases (30.1%) were positive for mycobacteria by culture. Niacin production and catalase activity were negative in 62/227 (27.4%) strains and after using a panel of different biochemicals and final confirmation by GenoType Mycobacterium CM assay. Out of 227 cultures tested, 165 (72.6%) strains were confirmed as M. tuberculosis complex, and 62 (27.4%) were confirmed as NTM. The most common NTM species identified were M. fortuitum 17 (27.5%) and M. intracellulare 13 (20.9%). The rapid identification of NTM species may help in targeted therapy and management of the diseases.

High serum levels of procalcitonin and soluble TREM-1 correlated with poor prognosis in pulmonary tuberculosis

OBJECTIVES

Comparisons of procalcitonin (PCT), C-reactive protein (CRP), and soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) would expand our knowledge of which biomarker is the best predictor for outcomes of patients with pulmonary tuberculosis (PTB).

METHODS

We prospectively enrolled 243 PTB patients, in whom PCT, CRP, and sTREM-1 measurement were performed to evaluate their prognostic value for 6-month mortality.

RESULTS

Serum PCT, CRP, and sTREM-1 levels on diagnosis of PTB were significantly higher in nonsurvivors (2.22 ± 6.22 vs. 0.13 ± 0.31 ng/mL, P = 0.043; 42.1 ± 59.4 vs. 12.5 ± 29.1 mg/L, P = 0.004; 332 ± 362 vs. 128 ± 98 pg/mL, P = 0.001, respectively) as compared with 6-month survivors. In multivariate Cox regression analysis, PCT ≧ 0.5 ng/mL (hazard ratio 4.13, 95% CI, 1.99-8.58) and sTREM-1 ≧ 129 pg/mL (hazard ratio 3.39, 95% CI, 1.52-7.58) remained independent mortality predictors. Serum PCT and sTREM-1 levels above the cutoffs were also associated with the presence of disseminated tuberculosis.

CONCLUSIONS

Among PTB patients, higher PCT, CRP, and sTREM-1 levels are observed in nonsurvivors than in 6-month survivors. Serum levels of PCT and sTREM-1 over the cutoffs are independently associated with a poor outcome. In addition, higher PCT and sTREM-1 levels would raise the clinical suspicion of disseminated tuberculosis.

Trends and predictors of changes in pulmonary function after treatment for pulmonary tuberculosis

OBJECTIVES

The present study aimed to investigate the trends in changes in pulmonary function and the risk factors for pulmonary function deterioration in patients with pulmonary tuberculosis after completing treatment.

INTRODUCTION

Patients usually have pulmonary function abnormalities after completing treatment for pulmonary tuberculosis. The time course for changes in pulmonary function and the risk factors for deterioration have not been well studied.

METHODS

A total of 115 patients with 162 pulmonary function results were analyzed. We retrieved demographic and clinical data, radiographic scores, bacteriological data, and pulmonary function data. A generalized additive model with a locally weighted scatterplot smoothing technique was used to evaluate the trends in changes in pulmonary function. A generalized estimating equation model was used to determine the risk factors associated with deterioration of pulmonary function.

RESULTS

The median interval between the end of anti-tuberculosis treatment and the pulmonary function test was 16 months (range: 0 to 112 months). The nadir of pulmonary function occurred approximately 18 months after the completion of the treatment. The risk factors associated with pulmonary function deterioration included smear-positive disease, extensive pulmonary involvement prior to anti-tuberculosis treatment, prolonged anti-tuberculosis treatment, and reduced radiographic improvement after treatment.

CONCLUSIONS

After the completion of anti-tuberculosis TB treatment, several risk factors predicted pulmonary function deterioration. For patients with significant respiratory symptoms and multiple risk factors, the pulmonary function test should be followed up to monitor the progression of functional impairment, especially within the first 18 months after the completion of anti-tuberculosis treatment.

Predicting results of mycobacterial culture on sputum smear reversion after anti-tuberculous treatment: a case control study

Background

Little is currently known regarding sputum smear reversion (acid-fast smear becomes positive again after negative conversion) during anti-tuberculous treatment. This study aimed to evaluate its occurrence in patients with pulmonary tuberculosis (TB) and identify factors predicting results of mycobacterial culture for smear-reversion of sputum samples.

Methods

The retrospective review was performed in a tertiary referral center and a local teaching hospital in Taiwan. From 2000 to 2007, patients with smear-positive culture-confirmed pulmonary TB experiencing smear reversion after 14 days of anti-tuberculous treatment were identified.

Results

The 739 patients with smear-positive pulmonary TB had 74 (10%) episodes of sputum smear reversion that grew Mycobacterium tuberculosis in 22 (30%) (Mtb group). The remaining 52 episodes of culture-negative sputum samples were classified as the non-Mtb group. The anti-tuberculous regimen was modified after confirming smear reversion in 15 (20%). Fourteen episodes in the Mtb group and 15 in the non-Mtb group occurred during hospitalization. All were admitted to the negative-pressure rooms at the time of smear reversion. Statistical analysis showed that any TB drug resistance, smear reversion within the first two months of treatment or before culture conversion, and the absence of radiographic improvement before smear reversion were associated with the Mtb group. None of the smear reversion was due to viable M. tuberculosis if none of the four factors were present.

Conclusions

Sputum smear reversion develops in 10% of patients with smear-positive pulmonary TB, with 30% due to viable M. tuberculosis bacilli. Isolation and regimen modification may not be necessary for all drug-susceptible patients who already have radiographic improvement and develop smear reversion after two months of treatment or after sputum culture conversion.

Prevalence and associated risk factors of mycobacterial infections in slaughter pigs from Mubende district in Uganda

To date, the public health relevance of mycobacterial infections in pigs is not well investigated despite high risk of infection. Recently, there has been a documented increase in opportunistic infections and risk of acquiring opportunistic mycobacterial infections in HIV/AIDS patients in Mubende district; unfortunately, there has been no published information on the epidemiology of mycobacterial infections in this area. This study was carried out between September 2008 and February 2009. Investigations were done to assess the prevalence and associated risk factors of mycobacterial infections in slaughtered pigs in Mubende district of Uganda. A total of 997 pigs (53.7% male and 46.3% female) from 31 different slaughterhouses were examined for the presence of lesions compatible with TB and mycobacterial infections. Pathologic tissue specimens were collected for culturing and isolation of mycobacteria. A cross-sectional technique was used based on convenient visits to slaughterhouses but random selection of individual slaughtered pigs for a detailed post-mortem inspection on a daily basis. The results reflected a 9.3% and 3.1% (95% CI) prevalence of Mycobacterium species based on necropsy examinations and culture isolation, respectively. The highest prevalence of mycobacterial infection was recorded in Buwekula County (the mixed agro-zone) whilst the lowest was in Kassanda County (pastoral zone). A multivariable logistical regression analysis identified age (P < or = 0.001) and sex (P < or = 0.05) as risk factors for mycobacterial infections in pigs. Post-estimation statistics of the regression model evaluation and validation fit it well into the data (HL, chi (2) = 5.9; P = 0.69 for necropsy, HL chi (2) = 2.9; P = 0.94 for culturing). This study documented a high prevalence of mycobacterial infections in slaughter pigs in Mubende district. The fact that pigs and human often share common housing and environment poses a high risk of zoonotic transmission. This then warrants further molecular investigation to identify the specific Mycobacterium species and their public health importance in this area.