Mycobacterial Growth Indicator Tube Research Articles

Diagnostic utility of a line probe assay for multidrug resistant-TB in smear-negative pulmonary tuberculosis.

ObjectiveTo evaluate the performance of Genotype MTBDRplus VER 2.0 in the diagnosis of Mycobacterium tuberculosis (MTB) in sputum smear-negative pulmonary TB cases.MethodsA total of 572 Ziehl-Neelsen sputum smear-negative samples were selected and subjected to line probe assay (Genotype MTBDRplus VER 2.0), and culture in mycobacterial growth indicator tube (MGIT-960). Immunochromatographic test was used to confirm the MTB-complex (MTBC) in culture-positive samples and phenotypic drug-susceptibility testing was done using MGIT-960.ResultsThe line probe assay was able to diagnose MTBC in 38.2% (213/558) of specimens after excluding 14 nontuberculous mycobacteria. Sensitivity and specificity of the assay were 68.4% and 89.3% respectively, considering MGIT-960 culture as gold standard after excluding contaminated and invalid results. On comparing with composite reference standard, the assay had 71.5% sensitivity and 100% specificity in the diagnosis of tuberculosis. The sensitivity and specificity for detecting resistance to rifampicin (RMP) were 100% and 99.24% respectively and for resistance to isoniazid (INH) were 97.62% and 98.55%, respectively.ConclusionGenotype MTBDRplus VER 2.0 is a rapid and precise diagnostic tool for detection of MTB in sputum smear-negative samples. It also facilitates accurate diagnosis of RMP and INH resistance within turn around-time.

Diagnostic usefulness of Xpert MTB/RIF assay for detection of tuberculous meningitis using cerebrospinal fluid

Tuberculous meningitis (TBM) is the most severe form of extra-pulmonary tuberculosis (TB) due to association of diseases with high rates of mortality and morbidity. Diagnosis continues to be a clinical challenge as microbiological confirmation is rare and time consuming resulting in delayed treatment. Xpert MTB/RIF assay is a rapid and simple test, which has been endorsed by World Health Organization as an initial diagnostic test for the diagnosis of TBM. However, evidence still lacks for its performance on cerebrospinal fluid (CSF) for the diagnosis of TBM especially from India. A total of 267 CSF samples from patients with high clinico-radiological suspicion of TBM were included in this study. Ziehl-Neelsen (ZN) staining, BACTEC Mycobacterial Growth Indicator Tube (MGIT-960) culture system, and Xpert MTB/RIF assay (using cartridge version G4) were tested on all samples. Of total 267 samples, all were negative for smear AFB and 52 (19.5%) were culture positive by MGIT-960 culture system. However, out of 52 (19.5%) cultures detected positive by MGIT-960, 5 (9.6%) were detected as resistant to rifampicin. Xpert MTB/RIF assay was positive in 38 (14.2%) samples and negative in 223 (83.5%) samples. Cartridge error was detected in 6 (2.2%) samples, which could not be repeated due to insufficient sample volume. The sensitivity and specificity of Xpert MTB/RIF assay in comparison to MGIT-960 was 55.1% (95%, CI: 40.2-69.3) and 94.8% (95%, CI: 90.9-97.4) respectively. Overall, Xpert MTB/RIF assay detected 38 (14.2%) as positive for MTB of which 4 (10.5%), 31 (81.6%) and 3 (7.9%) were found to be rifampicin resistant, sensitive and indeterminate respectively. Xpert MTB/RIF assay showed lower sensitivity as compared to MGIT 960 culture for the diagnosis of TBM from CSF samples.

Pilot studies of a human BCG challenge model

Despite the great effort to develop an effective vaccine against tuberculosis (TB) there is currently no reliable and safe human challenge model that can be used for in vivo evaluation of new TB vaccine candidates and/or elucidation of the mechanisms of TB protective immunity. In this study, five volunteers were challenged with BCG intradermally (ID). Swab specimens were collected at multiple time points from the vaccination site pre- and post-vaccination to quantitate mycobacterial shedding as a surrogate of in vivo mycobacterial immunity. We compared the performance of the TaqMan qPCR assay against colony-forming unit cultures on 7H10 agar plates, and time to positivity (TTP) of mycobacterial growth indicator tubes (MGIT) in order to evaluate the reproducibility and sensitivity in measuring BCG burden in swab specimens. BCG was detected in swab specimens from all five volunteers by at least one method, and no single method was superior in terms of sensitivity and reproducibility. A comparison of all three methods showed significant correlations by Spearman's rank test between 7H10 agar plating and qPCR (R = 0.601, P = 0.00072), MGIT culture TTP and 7H10 agar plating (R = 0.412, P = 0.029) as well as MGIT culture TTP and qPCR (R = −0.708, P = 0.00003). However, the three methods were somewhat different with regard to early versus late detection of BCG shedding post-challenge. This ID BCG challenge model has unique potential to further explore correlations between reactogenicity and immune mechanisms involved in protection against mycobacterial infections, and could therefore become a reliable tool in the evaluation process of new TB vaccination strategies.

First Line Anti-Tuberculosis Drugs Resistance Patterns of <i>Mycobacterium tuberculosis</i> Isolates from Newly Diagnosed Cases of Tuberculosis

Introduction: Tuberculosis is a major cause of mortality and morbidity world-wide. Anti-tuberculosis drugs have been used for many decades but resistance to them is now widespread. Globally 5% of tuberculosis cases and in India 3% among new TB cases. This study was planned to know the pattern of first line anti-tuberculosis drug resistance in south Gujarat, Surat region in newly diagnosed patients of tuberculosis. Material and Methods: 350 samples were processed for homogenisation and concentration using 4% NAOH-2.9% trisodium citrate. Processed samples were inoculated in liquid medium that is MGIT (Mycobacterial growth indicator tube). Positive samples for M. tbwere processed further for first line anti-tuberculosis drugs sensitivity testing (DST). Reading was taken by using MicroMGIT system. Result: Out of 350 samples 59 (17%) were positive samples, of which 48 (13%) were M. tb and 11 (3%) were non tuberculous mycobacteria. Out of 48 samples 2% (1 isolate) was resistant to isoniazid and Rifampicin while 2% were monoresistant to isoniazide, 2% monoresistant to streptomycin. No rifampicin monoresistant was detected. Conclusion: Such study may help in control of tuberculosis at regional and national level which would in turn help in planning of measures to control Multi-drug resistance tuberculosis. Continuous surveillance should be applied to know the periodic changing patterns and trend in Drug resistant tuberculosis.

A simplified mycobacterial growth inhibition assay (MGIA) using direct infection of mouse splenocytes and the MGIT system

We describe a simplified Mycobacterial Growth Inhibition Assay (MGIA) for pre-clinical assessment of vaccine-mediated protection in mice. The assay is accomplished by directly infecting splenocytes from vaccinated mice with Mycobacterium tuberculosis and quantifying mycobacteria using Mycobacterial Growth Indicator Tubes (MGIT). Vaccine-mediated immunogenicity detected by this assay correlated with protection.

肺結核症例における結核菌群核酸検出検査のためのLAMP法（Direct TB-LAMP）の有用性の検討

To evaluate the efficiency of the direct tuberculosis-loop-mediated isothermal amplification (TB-LAMP) assay by using non-centrifuged sputum samples. STUDY PERIOD AND METHODS: The study was conducted between June 2013 and February 2014. We collected 111 sputum samples from patients who had been radiographically diagnosed with tuberculosis and had not received any treatments for longer than 5 days. In the direct TB-LAMP assay, a loop-mediated isothermal amplification kit and 60-μL sputum samples were used. A direct smear microscopy test was used as the smear test. Then, the same sputum samples were processed with a CCE pretreatment reagent, and 100 μL of the solution samples were cultured by using the mycobacterial growth indicator tube (MGIT) culture method. Forty-six of the 111 samples were positive in the smear microscopy tests. All the smear-positive samples were positive in both the MGIT and direct TB-LAMP assay (100%). The mean positive detection time with the direct TB-LAMP assay was 13 minutes 55 seconds. Of 56 smear-negative and MGIT positive samples, 44 (78.6%) were judged to be positive using the direct TB-LAMP assay, with a mean positive detection time of 15 minutes 59 seconds. The direct TB-LAMP assay using non-centrifuged sputum samples was demonstrated to have a high detection rate and thus may be considered useful for rapid and effective tuberculosis diagnosis.

Detection of Mycobacterium avium subsp. paratuberculosis in Iranian patients with type 1 diabetes mellitus by PCR and ELISA.

Mycobacterium avium subsp. paratuberculosis (MAP) is the causative agent of paratuberculosis or Johne's disease in ruminants. Its role in triggering autoimmunity, including type 1 diabetes mellitus (T1DM), has been reported in recent years. Due to the high contamination rate of MAP in Iran's livestock and the increasing outbreak of T1DM, we investigated this association in a small group of patients with T1DM in Iran. Blood samples of 29 T1DM patients and 29 healthy control subjects were tested through enzyme-linked immunosorbent assay (ELISA) to detect antibodies against MAP3865c and ZnT8 homologous epitopes and the presence of MAP DNA. Blood samples were also cultured in mycobacterial growth indicator tubes and Herrold's egg yolkmedium containing mycobactin J. The results of ELISA showed a significant difference between T1DM patients and healthy group. IS900 was also detected in 51.72% of T1DM patients but in none of the control group. None of the samples grew in culture media. Due to the presence of MAP DNA and antibodies against MAP peptides in a significant number of T1DM patients compared with healthy control subjects, we may consider MAP as a possible trigger of T1DM in Iran. This indicates that exposure to MAP occurred in the positive subjects. Identifying the sources of contamination and routes of MAP transmission to humans seems necessary to prevent and reduce the burden of MAP infection in Iran.

Loop-mediated isothermal amplification assay for detection of Mycobacterium tuberculosis complex in infertile women

Background: Female genital tuberculosis (FGTB) has a profound impact on the reproductive health of patients including infertility. Conventional diagnostic techniques have low sensitivity and specificity as well as long turnaround time. There is a need of developing newer, rapid and practically adaptable technique, especially in low-income countries. Objective: To standardize and evaluate loop-mediated isothermal amplification (LAMP) technique for diagnosis of FGTB. Methods: A total of 300 endometrial biopsy samples from infertile females were subjected to Ziehl–Neelsen (ZN) staining, Lowenstein–Jensen culture, automated culture (BACTEC mycobacterial growth indicator tube), histopathological examination (HPE), nucleic acid amplification by polymerase chain reaction (PCR) and LAMP technique. Composite gold standard (either smear/culture/HPE/PCR positive) was considered for calculation of outcome parameters. Results: The observed sensitivities of ZN smear, culture, HPE, PCR and LAMP were 2.94%, 10.29%, 8.82%, 95.59% and 66.18%, respectively. Overall concordance between PCR and LAMP was 63%, which shows a good agreement. Conclusion: This study is the first to evaluate LAMP in the diagnosis of FGTB and found it to be a rapid and convenient technique, especially in low resource endemic settings.

Comparison of Mycobacterial Growth Indicator Tube with Culture on RGM Selective Agar for Detection of Mycobacteria in Sputum Samples from Patients with Cystic Fibrosis.

Nontuberculous mycobacteria (NTM) are an important cause of pulmonary disease in patients with cystic fibrosis (CF). A new culture medium (RGM medium) for the isolation of rapidly growing mycobacteria from the sputum of cystic fibrosis patients has recently been reported. The aim of this study was to compare culture of sputum samples on RGM medium with culture using a standard automated liquid culture method. Sputum samples were obtained from 187 distinct patients with CF attending King's College Hospital, London, United Kingdom. Each sample was decontaminated with 3% oxalic acid and inoculated into a mycobacterial growth indicator tube (MGIT) that was monitored for 42 days using the Bactec MGIT 960 instrument. Each sample was also cultured, without decontamination, onto RGM medium, which was incubated for 10 days at 30°C. Mycobacteria were isolated from 28 patients (prevalence, 15%). Mycobacteria were detected in 24 samples (86%) using the MGIT and in 23 samples (82%) using RGM medium (P = 1.00). In this setting, RGM medium showed sensitivity equivalent to that of the MGIT for isolation of NTM from the sputum of patients with CF. RGM medium offers a simple, convenient tool that can be embedded into routine culture methods, allowing the culture of all sputum samples that are submitted from patients with CF.

Rapid diagnosis of MDR and XDR tuberculosis with the MeltPro TB assay in China.

New diagnostic methods have provided a promising solution for rapid and reliable detection of drug-resistant TB strains. The aim of this study was to evaluate the performance of the MeltPro TB assay in identifying multidrug-resistant (MDR-) and extensively drug-resistant tuberculosis (XDR-TB) patients from sputum samples. The MeltPro TB assay was evaluated using sputum samples from 2057 smear-positive TB patients. Phenotypic Mycobacterial Growth Indicator Tube (MGIT) 960 drug susceptibility testing served as a reference standard. The sensitivity of the MeltPro TB assay was 94.2% for detecting resistance to rifampicin and 84.9% for detecting resistance to isoniazid. For second-line drugs, the assay showed a sensitivity of 83.3% for ofloxacin resistance, 75.0% for amikacin resistance, and 63.5% for kanamycin resistance. However, there was a significant difference for detecting kanamycin resistance between the two pilot sites in sensitivity, which was 53.2% in Guangdong and 81.5% in Shandong (P = 0.015). Overall, the MeltPro TB assay demonstrated good performance for the detection of MDR- and XDR-TB, with a sensitivity of 86.7% and 71.4%, respectively. The MeltPro TB assay is an excellent alternative for the detection of MDR- and XDR-TB cases in China, with high accuracy, short testing turn-around time, and low unit price compared with other tests.

Drug-resistant tuberculosis in children less than 5 years old with culture positive mycobacterium tuberculosis

Background: Diagnosis of paediatric tuberculosis remains a challenge due to the difficulty in obtaining samples from children and the low sensitivity of culture confirmation. Drug resistance in TB continues to be a significant challenge in South Africa. Microbiologic confirmation of tuberculosis in children is necessary to exclude drug-resistant tuberculosis in face of the high multidrug-resistant TB (MDR-TB) and extensively drug-resistant TB (XDR-TB) rates reported in the adult population. We describe the rates of drug-resistant TB in children less than 5 years old from KwaZulu Natal – a province in South Africa with the highest burden of both TB and HIV disease. Methods & Materials: A retrospective descriptive analysis was done of specimens from children less than 5 years old submitted to TB reference laboratory in KwaZulu-Natal, South Africa. Data was collected from 2012 to 2014. Specimens cultured included respiratory samples, lymph node aspirates, pleural and peritoneal fluid, cerebrospinal fluid, bone and tissue samples. Cultures were performed using the automated Mycobacterial Growth Indicator Tube 960 system (Becton Dickinson) and identification and susceptibility was confirmed with the line probe MTBDR plus assay (Hain-Life Science). From 2012 the Xpert MTB/RIF was introduced into the diagnostic algorithm for MTB detection and Rifampicin resistance. Results: 903 children were found to have culture-confirmed TB during this 3 year period. Drug susceptibility testing showed susceptible MTB ranging from 71-82% in the various age groups. Overall the resistance to isoniazid and rifampicin (MDR) rates ranged from 11-16% with the highest rates found in 2 year old age group. Extensively drug-resistant TB (0-2.1%) was present in all age groups. INH mono-resistance was 3,4% and Rifampicin mono-resistance was 2.8%. Conclusion: High rates of Mycobacterium tuberculosis including extensively drug resistant TB were found in children less than one, which indicates the burden of TB infection among woman during childbearing years. INH mono-resistance is of concern as this will not be detected by the current diagnostic algorithm that includes the Xpert MTB/RIF for MTB detection and Rifampicin resistance. Children with INH mono-resistance may benefit from high-dose isoniazid therefore bacteriological confirmation through culture is important in management of childhood TB.

Cough Aerosols of Mycobacterium tuberculosis in the Prediction of Incident Tuberculosis Disease in Household Contacts.

Tuberculosis disease develops in only 5%-10% of humans infected with Mycobacterium tuberculosis The mechanisms underlying this variability remain poorly understood. We recently demonstrated that colony-forming units of M. tuberculosis in cough-generated aerosols are a better predictor of infection than the standard sputum acid-fast bacilli smear. We hypothesized that cough aerosol cultures may also predict progression to tuberculosis disease in contacts. We conducted a retrospective cohort study of 85 patients with smear-positive tuberculosis and their 369 household contacts in Kampala, Uganda. Index case patients underwent a standard evaluation, and we cultured M. tuberculosis from cough aerosols. Contacts underwent a standard evaluation at enrollment, and they were later traced to determine their tuberculosis status. During a median follow-up of 3.9 years, 8 (2%) of the contacts developed tuberculosis disease. In unadjusted and adjusted analyses, incident tuberculosis disease in contacts was associated with sputum Mycobacterial Growth Indicator Tube culture (odds ratio, 8.2; 95% confidence interval, 1.1-59.2; P = .04), exposure to a high-aerosol tuberculosis case patient (6.0, 1.4-25.2; P = .01), and marginally, human immunodeficiency virus in the contact (6.11; 0.89-41.7; P = .07). We present data demonstrating that sputum and aerosol specimens measure 2 related but different phenomena. We found an increased risk of tuberculosis progression among contacts of high-aerosol case patients. The hypothesis that a larger infectious inoculum, represented by high aerosol production, determines the risk of disease progression deserves evaluation in future prospective studies.

Activity of nitazoxanide and tizoxanide against Mycobacterium tuberculosis in vitro and in whole blood culture

Nitazoxanide (NTZ) and its metabolite tizoxanide (TIZ) were studied as antimycobacterial agents invitro (in mycobacterial growth indicator tube [MGIT] cultures) and in a whole blood bactericidal assay. Both NTZ and TIZ show high protein binding. In MGIT cultures (albumin concentration=78μM), inhibition of Mycobacterium tuberculosis growth occurred at total drug concentrations of ≥16μg/ml, whereas in whole blood cultures (albumin concentration=350μM), ≥128μg/ml was required. Free drug fractions at these two conditions were estimated to be 69% and 2%, respectively. Co-incubation of NTZ and TIZ in human plasma for 72h nearly completely eliminated their ability to inhibit mycobacterial growth in MGIT. Interactions with plasma proteins may limit the potential of NTZ and TIZ as drugs for human tuberculosis.

Clinical Evaluation of Automated BACTEC MGIT 960 System for Identification, Recovery and Drug Susceptibility Testing of Mycobacterium tuberculosis Clinical Isolates

Background and Objectives: The objective of this study was to evaluate the clinical applicability of BACTEC Mycobacterial Growth Indicator Tube 960 TM system with Lowenstein-Jensen (LJ) culture for routine recovery and drug susceptibility test analysis of mycobacteria from clinical specimens. Method and Statistical Analysis: One hundred and seven clinical specimens were processed by routine laboratory procedures like p-nitro benzoic acid test and PCR amplification of IS 6110 and inoculated in LJ medium and MGIT for mycobacterial growth recovery and DST procedures. Findings: Ninety four (87.8%) samples were demonstrated reproducible result by MGIT, in which 89 (83.1%) were smear positive and all the specimens were confirmed as M. tuberculosis complex by MGIT PNB and IS 6110 PCR procedures. The observed mean time for mycobacterial detection was 9 days for primary culture and 11 days for DST in MGIT system. Applications/Improvements: The use of BACTEC MGIT 960 system was found to be a sensitive, rapid mycobacterial recovery and culture system and offers precise identification and detection of drug resistance from clinical isolates at earliest.

PRESENCE OF MYCOBACTERIUM AVIUM SUBSP. PARATUBERCULOSIS IN ALPACAS (LAMA PACOS) INHABITING THE CHILEAN ALTIPLANO.

Mycobacterium avium subsp. paratuberculosis (MAP) is the etiologic agent of paratuberculosis. The organism causes disease in both domestically managed and wild ruminant species. South American camelids have a long, shared history with indigenous people in the Andes. Over the last few decades, increasing numbers of alpacas were exported to numerous countries outside South America. No paratuberculosis surveillance has been reported for these source herds. In this study, individual fecal samples from 85 adult alpacas were collected from six separate herds in the Chilean Altiplano. A ParaTB mycobacterial growth indicator tube (MGIT) liquid culture of each individual fecal sample, followed by real-time polymerase chain reaction (PCR) protocol was used for confirmation. DNA extracts from a subset of confirmed MAP isolates were subjected to mycobacterial interspersed repetitive units-variable number of tandem repeats (MIRU-VNTR) typing. Fifteen alpaca were fecal culture test-positive. Five false-positive culture samples were negative on PCR analysis for Mycobacterium avium subsp. avium (MAA), Mycobacterium bovis (M. bovis), and the 16 S rDNA gene. Three MAP isolates subset-tested belonged to the same MIRU-VNTR type, showing four repeats for TR292 (locus 1) in contrast to the three repeats typical of the MAP reference strain K10. The number of repeats found in the remaining loci was identical to that of the K10 strain. It is not known how nor when MAP was introduced into the alpaca population in the Chilean Altiplano. The most plausible hypothesis to explain the presence of MAP in these indigenous populations is transmission by contact with infected domestic small ruminant species that may on occasion share pastures or range with alpacas. Isolation of this mycobacterial pathogen from such a remote region suggests that MAP has found its way beyond the confines of intensively managed domestic agriculture premises.

Detection of multidrug-resistant tuberculosis using MGIT™(TM) and MAS-PCR in Tripura, India.

Multidrug-resistant tuberculosis (MDR-TB) poses a global threat that is further compounded by the human immunodeficiency virus (HIV) epidemic. To detect MDR-TB among pulmonary TB (PTB) patients with or without HIV coinfection by isolating and identifying Mycobacterium tuberculosis from clinical samples and performing drug susceptibility testing (DST). Sputum was collected from presumed PTB cases. Microscopic examination was performed following Ziehl-Neelsen (ZN) staining and cultured in Löwenstein-Jensen (LJ) medium. First-line anti-tuberculosis DST of the isolates was performed using MGIT™ (Mycobacterial Growth Indicator Tube) and multiplex allele-specific polymerase chain reaction (MAS-PCR). Of 172 study subjects, 59.3% (102/172) were smear-positive and 40.7% (70/172) were smear-negative. In the smear-positive and -negative groups, respectively 62.7% (64/102) and 8.6% (6/70) were culture-positive. DST on MGIT showed a cumulative resistance of 7.1% (5/70) to isoniazid (INH) and rifampicin. More ethambutol (EMB) and combined INH+EMB resistance was detected using MAS-PCR. MDR-TB is a problem in Tripura, and culture and phenotypic DST are required for diagnosis. MAS-PCR may provide an alternative rapid screening tool.

Comparative Study of Z N Staining vs. Flurochrome Staining and Impact of Sample Processing on Diagnosis of Tuberculosis from Various Clinical Samples

Background: Tuberculosis is a highly infectious disease and India has the highest burden with it. Diagnosis of tuberculosis in many countries is still dependent on microscopy. Although its sensitivity is low in comparison to culture and molecular methods, its sensitivity can still be improved by using fluorescence staining method and processing of samples by homogenization and concentration method. Material and methods: Samples were collected from all newly registered suspected cases of tuberculosis in tertiary care hospital from outward and indoor department during a period of one year. Smears were prepared for Ziehl Neelsen stain and fluorescence stain both before and after homogenization and concentration procedure by 4% NAOH-2.9% sodium citrate method and results of them were interpreted according to RNTCP criteria for grading of sputum samples. All the samples were cultured in liquid culture MGIT system (Mycobacterial Growth Indicator Tube) and results of microscopy were compared with liquid culture taken as gold standard. Data were analyzed by using SPSS software version 16. Result: 350 samples were collected during study period. Out of 350 samples, 48 samples were positive for M. tuberculosis by MGIT system. In comparison with MGIT system, sensitivity of Z N stain for detection of acid fast bacilli was 77% before decontamination procedure, which was increased up to 85.42% after decontamination and concentration process. Sensitivity of fluroscence stain was 85.42% before processing, which was increased up to 91.67% after processing of samples. Conclusion: Sensitivity of smear microscopy can be enhanced by use of fluroscence microscopy and concentration method.

In Vitro Evaluation of Linezolid and Meropenem Against Clinical Isolates of Multi Drug Resistant Tuberculosis By Mycobacterial Growth Indicator Tube (MGIT) 960.

To evaluate the in vitro effectiveness of multiple breakpoint concentrations of newer antituberculosis agents (Linezolid and Meropenem) against Multi Drug-Resistant Tuberculosis (MDR-TB) isolates. A descriptive cross-sectional study. Microbiology Department, Armed Forces Institute of Pathology (AFIP), Rawalpindi, from September 2011 to August 2013. A total of 100 MDR-TB isolates recovered during the study period were subjected to susceptibility testing against multiple breakpoint concentrations of Linezolid (LZD) and Meropenem (MER). The breakpoint concentration used for LZD were 0.5, 1.0 and 2.0 µg/ml, while for MER were 4.0, 8.0 and 16 µg/ml. Mycobacterial Growth Indicator Tube (MGIT) 960 system was used to carry out drug susceptibility testing as per recommended protocol. At break point concentration of 0.5 µg/ml, 80 out of 100 (80%) MDR-TB isolates were susceptible to LZD while at breakpoint concentration of 1.0 µg/ml and 2.0 µg/ml, 96/100, (96%) of MDR-TB isolates were susceptible. For MER, at breakpoint concentrations of 4.0 µg/ml no MDR-TB isolate was susceptible, while at 8.0 µg/ml 3/100, (3%) and at 16.0 µg/ml 11/100, (11%) of MDR-TB isolates were susceptible. LZD was found to have excellent in vitro efficacy as 96% of MDR-TB isolates were susceptible at breakpoint concentration of 1.0 µg/ml or more. In case of MER it was found that in vitro susceptibility improved as the break point concentrations were increased.

Extensively and pre-extensively drug resistant tuberculosis in clinical isolates of multi-drug resistant tuberculosis using classical second line drugs (levofloxacin and amikacin).

To find out the frequency of Extensively Drug Resistant (XDR) and pre-XDR tuberculosis in clinical isolates of Multi-Drug Resistant (MDR) Tuberculosis (TB) by determining the susceptibilities against Levofloxacin and Amikacin (classical second line antituberculosis drugs). Adescriptive cross-sectional study. Microbiology Department, Armed Forces Institute of Pathology (AFIP), Rawalpindi, from September 2011 to August 2013. Amikacin (AK) and Levofloxacin (LEVO) were obtained in chemically pure form from Sigma (Taufkirchen, Germany). The breakpoint concentration used for AK was 1.0 µg/ml and for LEVO 2.0 µg/ml. Mycobacterial Growth Indicator Tube (MGIT) 960 system was used to carry out drug susceptibility testing as per recommended protocol. A total of 3 MDR-TB isolates (3%) turned out to be XDR-TB based upon simultaneous resistance to injectable second line antituberculosis drug AK and one of the fluoro-quinolones (LEVO). A total of 24 MDR-TB isolates (24%) were found to be pre-XDR based upon resistance to LEVO alone. Treatment status record of patients with XDR and pre-XDRTB isolates revealed that majority of patients had received fluoroquinolones (FQs) during the course of treatment. XDR-TB has started to emerge in MDR-TB isolates in our set up. The worrying sign is the high frequency of pre-XDR tuberculosis. Urgent steps need to be taken to stem the tide of pre-XDR-TB in our population. It is thus recommended to develop facilities to carry out drug susceptibility testing to monitor the status of pre-XDR and XDR-TB in our population.

Pharmacodynamic Modeling of Bacillary Elimination Rates and Detection of Bacterial Lipid Bodies in Sputum to Predict and Understand Outcomes in Treatment of Pulmonary Tuberculosis.

Antibiotic-tolerant bacterial persistence prevents treatment shortening in drug-susceptible tuberculosis, and accumulation of intracellular lipid bodies has been proposed to identify a persister phenotype of Mycobacterium tuberculosis cells. In Malawi, we modeled bacillary elimination rates (BERs) from sputum cultures and calculated the percentage of lipid body-positive acid-fast bacilli (%LB + AFB) on sputum smears. We assessed whether these putative measurements of persistence predict unfavorable outcomes (treatment failure/relapse). Adults with pulmonary tuberculosis received standard 6-month therapy. Sputum samples were collected during the first 8 weeks for serial sputum colony counting (SSCC) on agar and time-to positivity (TTP) measurement in mycobacterial growth indicator tubes. BERs were extracted from nonlinear and linear mixed-effects models, respectively, fitted to these datasets. The %LB + AFB counts were assessed by fluorescence microscopy. Patients were followed until 1 year posttreatment. Individual BERs and %LB + AFB counts were related to final outcomes. One hundred and thirty-three patients (56% HIV coinfected) participated, and 15 unfavorable outcomes were reported. These were inversely associated with faster sterilization phase bacillary elimination from the SSCC model (odds ratio [OR], 0.39; 95% confidence interval [CI], .22-.70) and a faster BER from the TTP model (OR, 0.71; 95% CI, .55-.94). Higher %LB + AFB counts on day 21-28 were recorded in patients who suffered unfavorable final outcomes compared with those who achieved stable cure (P = .008). Modeling BERs predicts final outcome, and high %LB + AFB counts 3-4 weeks into therapy may identify a persister bacterial phenotype. These methods deserve further evaluation as surrogate endpoints for clinical trials.