Improvement in mycobacterial yield and reduced time to detection in pediatric samples by use of a nutrient broth growth supplement

Strain structure analysis of Mycobacterium tuberculosis circulating among HIV negative, positive and drug resistant TB patients attending chest clinics in Western Kenya

BACKGROUND

Despite global tuberculosis (TB) interventions, the disease remains one of the major public health concerns. Kenya is ranked 15th among 22 high burden TB countries globally.

METHODS

A cross-sectional study was conducted in Western Kenya, which comprises 10 counties. A multistage sampling method was used where a single sub-county was randomly selected followed by sampling two high volume health facility from each sub-county. Identification of spoligotype profiles and their family distribution and lineage level were achieved by comparison with SITVIT database.

RESULTS

Lineage distribution pattern revealed that the most predominant lineage was CAS 220 (39.8%) followed by Beijing 128 (23.1%). The other lineages identified were T, LAM, H, X, S and MANU which were quantified as 87 (15.7%), 67 (12.1%), 16 (2.8%), 10 (1.8%), 8 (1.4%) and 5 (0.9%) respectively. CAS and Beijing strains were the most predominant lineage in both HIV negative and positive TB patients. The Beijing lineage was also the most predominant in resistant M. tuberculosis strains as compared to wild type. A total of 12 (2.0%) were orphaned M. tuberculosis strains which were spread across all the 10 counties of the study site. In multivariate logistic regression adjusting for potential cofounders three potential risk factors were significant. HIV status (OR = 1.52, CI = 0.29-3.68 and P value of 0.001), Alcohol use (OR = 0.59, CI = 0.43-3.12 and P-value =0.001) and cross border travel (OR = 0.61, CI = 0.49-3.87 and P value = 0.026). Most M. tuberculosis clinical isolates showed genetic clustering with multivariate logistic regression indicating three potential risk factors to clustering. HIV status (OR = 1.52, CI = 0.29-3.68 and P value of 0.001), Alcohol use (OR = 0.59, CI = 0.43-3.12 and P-value =0.001) and cross border travel (OR = 0.61, CI = 0.49-3.87 and P value = 0.026).

CONCLUSION

There exist diverse strains of M. tuberculosis across the 10 counties of Western Kenya. Predominant distribution of clustered genotype points to the fact that most TB cases in this region are as a result of resent transmission other than activation of latent TB.

The spectrum of cerebrospinal fluid findings in tuberculous meningitis and their relation to severity, radiological features, and outcome

Objectives

The aim of the study was to evaluate cerebrospinal fluid (CSF) findings in tuberculous meningitis (TBM) and correlate it with severity, radiological features, and outcome of TBM.

Materials and Methods

In a retrospective study, data from admitted TBM patients were analyzed, and findings of CSF examinations were recorded. The CSF was categorized as typical (protein 50-500 mg/dL, cells 50-500/mm3, and glucose 50% or lower of blood sugar); those above and below these values were categorized as increased or decreased, respectively. The CSF findings were correlated with stage of TBM, and 3-month outcome and radiological features. Paradoxical response was also noted.

Results

There were 111 patients with TBM (definite 34, highly probable 77). On admission, 20 patients were in Stage I, 63 in Stage II, and 28 in Stage III TBM. CSF cells were in typical range in 73, low in 27 and increased in 11 patients. Protein was in typical range in 92 patients decreased in 11 patients and increased in eight patients. Sugar was normal in 41 and reduced in 70 patients. CSF cells, glucose, and protein did not correlate with the severity of meningitis. Fifteen patients had normal initial magnetic resonance imaging (MRI). Tuberculomas were present in 53 patients, hydrocephalus in 43 patients, basal exudates in 43 patients, and infarction in 44 patients. Mixed findings were present in 65 patients. The MRI features did not correlate with CSF. Second CSF was available after a median duration of 26 (13-276) days in 50 patients. The CSF cells were decreased in 20 and increased in 30 patients, protein increased in 30 and sugars decreased in 16 patients. Paradoxical worsening occurred in 27 patients. Fifty-one patients recovered completely, 41 partially, 15 had poor, three patients were lost to follow-up, and one died. CSF parameters did not correlate with 3-month outcome or paradoxical worsening. CSF parameters do not differ significantly between baseline and 1 month CSF, but cells and lymphocytes changed significantly between 1st month and 3rd month CSF.

Conclusion

Typical CSF findings were present in 66% and did not correlate severity of TBM, radiological features paradoxical worsening or 3-month outcome. CSF cell count decreased within 3 months of treatment.

Nano sized gallium oxide surface features for enhanced antimicrobial and osteo-integrative responses

Gallium oxide has known beneficial osteo-integrative properties. This may have importance for improving the osteointegration of orthopedic implants. At high concentrations gallium is cytotoxic. Therefore, integration of gallium into implant devices must be carefully controlled to limit its concentration and release. A strategy based on surface doping of gallium although challenging seems an appropriate approach to limit dose amounts to minimize cytotoxicity and maximize osteointegration benefits. In this work we develop a novel form of patterned surface doping via a block copolymer-based surface chemistry that enables very low gallium content but enhanced osteointegration as proven by comprehensive bioassays. Polystyrene-b-poly 4vinyl pyridine (PS-b-P4VP) BCP (block copolymer) films were produced on surfaces. Selective infiltration of the BCP pattern with a gallium salt precursor solution and subsequent UV-ozone treatment produced a surface pattern of gallium oxide nanodots as evidenced by atomic force and scanning electron microscopy. A comprehensive study of the bioactivity was carried out, including antimicrobial and sterility testing, gallium ion release kinetics and the interaction with human marrow mesenchymal stomal cells and mononuclear cells. Comparing the data from osteogenesis media assay tests with osteoclastogenesis tests demonstrated the potential for the gallium oxide nanodot doping to improve osteointegration properties of a surface.

Diagnostic Advances in Childhood Tuberculosis—Improving Specimen Collection and Yield of Microbiological Diagnosis for Intrathoracic Tuberculosis

There is no microbiological gold standard for childhood tuberculosis (TB) diagnosis. The paucibacillary nature of the disease, challenges in sample collection in young children, and the limitations of currently available microbiological tests restrict microbiological confirmation of intrathoracic TB to the minority of children. Recent WHO guidelines recommend the use of novel rapid molecular assays as initial diagnostic tests for TB and endorse alternative sample collection methods for children. However, the uptake of these tools in high-endemic settings remains low. In this review, we appraise historic and new microbiological tests and sample collection techniques that can be used for the diagnosis of intrathoracic TB in children. We explore challenges and possible ways to improve diagnostic yield despite limitations, and identify research gaps to address in order to improve the microbiological diagnosis of intrathoracic TB in children.

Distribution patterns of drug resistance Mycobacterium tuberculosis among HIV negative and positive tuberculosis patients in Western Kenya

INTRODUCTION

Globally anti-tuberculosis drug resistance is one of the major challenges affecting control and prevention of tuberculosis. Kenya is ranked among 30 high burden TB countries globally. However, there is scanty information on second line antituberculosis drug resistance among tuberculosis patients. Therefore, this study aimed at determining Mycobacterium tuberculosis drug resistant strain distribution pattern in 10 counties of Western Kenya among HIV positive and negative patients.

METHOD

A cross-sectional study was conducted in Western Kenya, which comprises 10 counties. A multistage sampling method was used where a single sub-county was randomly selected followed by sampling one high volume health facility from each sub-county. Consenting study subjects with at least two smear positive sputum at the time of enrolment were randomly selected. The collected sputum was decontaminated with N-acetyl-L-cysteine-sodium hydroxide (NALC-NaOH) and then stained with Ziehl Neelsen Stain before visualizing the presence of bacilli under microscope at ×100 magnification with oil immersion. Further, the identified bacilli were cultured and susceptibility test carried out using known first and second line antimycobacterial tuberculosis. HIV testing was carried out using Determine^® HIV-1/2 rapid test (Abbot Diagnostics, Maidenhead, United Kingdom). Those who had smear converted were dropped from the study. Finally, drug susceptibility pattern across the 10 counties of Western Kenya was evaluated.

RESULTS

Our study showed that Mycobacterium tuberculosis drug resistance among HIV negative and positive cases in Western Kenya was prevalent in all the 10 counties surveyed. Based on the drug susceptibility tests, 53.2% and 42.7% of the study samples were resistant to at least one antituberculosis drug among HIV negative and HIV positive patients respectively. The data analysis revealed that among the HIV-positive and HIV-negative patients, resistance to INH was predominant (28.5%, and 23.6%, respectively), followed by RIF (16.4% and 14.6% respectively). Second-line drug resistant strains identified among HIV negative patients included Ethionamide (0.3%), Gatifloxacin (0.3%), Amikacin (0.3%) and Capreomycin (0.3%). There was no second line drug monoresistance among HIV positive TB patients. Multi/poly drug resistance were noted among HIV-negative patients in, INH + AMK (0.7%), INH + PZA (1%), INH + GFX (0.7%, INH + ETO (0.7%, STY + ETO (1%), ETH + ETO (1.0%), INH + KAN (0.7%) and INH + CAP (0.7%) strains/cases at 95% confidence interval. Among HIV positive patients INH + GFX (1.1%), INH + ETO (0.4%) and INH + KAN (0.4%) strains of M. tuberculosis were identified with a confidence interval of 95%. Geographical distribution patterns analysis of M. tuberculosis drug polyresistant strains across the 10 counties were recorded. Among HIV TB patients, resistant strains were identified in Nyamira (INH + GFX, INH + KAN), Bungoma ((ETO + STY), Busia (ETH + ETO and STY + ETO) Homabay (RIF + AMK. ETO + ETH and ETO + STY), Kisumu (ETH + ETO and PZA + ETO) and in Kakamega, Kisii and Vihiga (INH + KAN and RIF + AMK). There was no M. tuberculosis polyresistant strain identified in Migori and Siaya counties. Among HIV positive TB patients, M. tuberculosis resistant strains were identified in three counties, Nyamira (INH + KAN) Homabay (INH + GFX and INH + AMK) and Kakamega (INH + GFX). There was no polyresistant M. tuberculosis strain identified in Migori, Bungoma, Kisii, Vihiga, Busia, Siaya and Kisumu Counties.

DISCUSSION

The distribution patterns of M. tuberculosis drug resistance among HIV negative and positive TB patients could be as a result of reported high prevalence of HIV in Western Kenya counties especially the area under study. Tuberculosis is one of the opportunistic diseases that have been shown to be the major cause of AIDS among HIV infected patients. Resent reports by National AIDS Control Council shows that Kisumu, Siaya, Homabay, Migori, Busia have the overall leading in HIV prevalence in Kenya. The low prevalence of drug resistant strains among HIV tuberculosis patients could be as a result of drug adherence attitude adopted by HIV patients, availability of continuous counselling and close follow up and notification by healthcare workers and community health volunteers.

CONCLUSION

Drug resistant M. tuberculosis strains prevalence is still high among HIV negative and positive patients in Western Kenya with the most affected being HIV negative TB patients. It is therefore probable that the existing control measures are not adequate to control transmission of drug resistant strains. Further, miss diagnosis or delayed diagnosis of TB patients could be contributing to the emergence of M. tuberculosis drug polyresistant strains.

RECOMMENDATION

Based on the result of this study, regular TB drug resistance surveillance should be conducted to ensure targeted interventions aimed at controlling increased transmission of the tuberculosis drug resistant strains among HIV/AIDS and HIV negative patients. There is also need for improved drug resistant infection control measures, timely and rapid diagnosis and enhanced and active screening strategies of tuberculosis among suspected TB patients need to be put in place. Further, studies using a larger patient cohort and from counties across the country would shed much needed insights on the true national prevalence of different variants of M. tuberculosis drug resistance.

Effect of Neutralization of Gastric Aspirate on culture yield of mycobacterium tuberculosis in children with pulmonary tuberculosis

INTRODUCTION

Conventionally gastric aspirates are neutralized with sodium bicarbonate to improve the culture yield of MTB. However, only limited data is there to support this practice. The aim of this study was to compare the contamination rate, culture yield and time to detection of Mycobacterium tuberculosis (MTB) in neutralized and non-neutralized gastric aspirate samples and report the drug resistance.

MATERIALS AND METHODS

A total of 336 neutralized and non-neutralized gastric aspirate samples were simultaneously cultured by both LJ culture and MGIT 960 to compare the difference in isolation rate, time to detection and contamination rate. First line drug susceptibility testing was performed using MGIT 960 SIRE kit.

RESULTS

MTB was isolated from 8.6% (29/336) of GA samples by one or more of the culture methods. The isolation rate of MTB from neutralized and non-neutralized GA samples by combined LJ and MGIT 960 culture was 7.1% (24/336) and 6.8% (23/336), respectively. Both of them detected 18 MTB isolates in common. However, the neutralized and non-neutralized GA samples detected additional 6 and 5 MTB isolates, respectively. The mean time to detection of MTB were similar. In MGIT 960 culture, contamination rate of non-neutralized samples (17%) was significantly lower when compared to neutralized samples (21.1%) (P = 0.044). Drug susceptibility testing of MTB isolates revealed that, out of 26 isolates, 2 were resistant to ethambutol, one each was resistant to isoniazid and rifampicin.

CONCLUSION

The findings of this study suggest that non-neutralized samples should be routinely processed in addition to the neutralized samples for optimum isolation of MTB from gastric aspirate samples.

Performance of Mycobacterium Growth Indicator Tube BACTEC 960 with Lowenstein-Jensen method for diagnosis of Mycobacterium tuberculosis at Ethiopian National Tuberculosis Reference Laboratory, Addis Ababa, Ethiopia

BACKGROUND

Bacteriological confirmed active case detection remains the corner stone for diagnosing tuberculosis. Non-radiometric liquid culture system Mycobacterium Growth Indicator Tube with automated interface had been recommended by expert groups in addition to conventional solid culture media such as Lowenstein-Jensen. However in high burden resource limited countries advanced non-radiometric based tuberculosis diagnostic methods such as MGIT 960 is limited. Therefore we have evaluated the performance of MGIT 960 system compared to LJ for recovery of Mycobacterium complex (MTBC) from clinical specimens.

METHODS

A cross sectional study was conducted from a total of 908 samples between January 1st, 2013 to December 31st, 2014. Clinical specimens were processed following standard procedures and the final suspension was inoculated to MGIT tubes and LJ slant. Identification and confirmation of MTBC was done by ZN staining and SD Bioline test. Data was analyzed by SPSS version 20. The sensitivity, specificity, recovery rate and the average turnaround time to recover the organism was computed.

RESULTS

From a total of 908 clinical specimens processed using both LJ and BACTEC MGIT liquid culture methods the recovery rate for LJ and MGIT, for smear positive samples was 66.7% (74/111) and 87.4% (97/ 111) respectively while for smear negative samples was 13.4% (108/797) and 17.4% (139/797) for LJ and MGIT methods respectively. The overall recovery rate for MGIT is significantly higher than LJ methods [26% (236/908; vs. 20%, 182/908, P = 0.002)]. The average turnaround time for smear positive samples was 16 and 31 days for MGIT and LJ respectively. Turnaround time for smear negative samples was 20 and 36 days for MGIT and LJ respectively. The overall agreement between MGIT and LJ was fairly good with Kappa value of 0.59 (P < 0.001). In the present study the contamination rate for MGIT is higher than the LJ methods, 15 and 9.3% respectively.

CONCLUSIONS

The BACTEC MGIT liquid culture system has better MTBC recovery rate with shorter turnaround time for both smear positive and negative clinical specimens compared to Conventional LJ method. However, efforts should be made in order to reduce the high contamination rate in BACTEC MGIT system and to lesser extent to LJ methods.

Laboratory Diagnosis of Mycobacterium tuberculosis Infection and Disease in Children

Diagnosis of tuberculosis in children is challenging; even with advanced technologies, the diagnosis is often difficult to confirm microbiologically in part due to the paucibacillary nature of the disease. Clinical diagnosis lacks standardization, and traditional and molecular microbiologic methods lack sensitivity, particularly in children. Immunodiagnostic tests may improve sensitivity, but these tests cannot distinguish tuberculosis disease from latent infection and some lack specificity. While molecular tools like Xpert MTB/RIF have advanced our ability to detect Mycobacterium tuberculosis and to determine antimicrobial resistance, decades old technologies remain the standard in most locales. Today, the battle against this ancient disease still poses one of the primary diagnostic challenges in pediatric laboratory medicine.

Optimizing Mycobacterial Culture in Smear-Negative, Human Immunodeficiency Virus-Infected Tuberculosis Cases

Introduction

Tuberculosis (TB) is a significant public health problem and the diagnosis in human immunodeficiency virus (HIV)—infected individuals is challenging. The use of mycobacterial culture remains an important complementary tool and optimizing it has important benefits. We sought to determine the effect of an increase in the number of specimens evaluated, addition of nutritional supplementation to the culture medium, sputum appearance and volume on diagnostic yield and time to detection of pulmonary TB among smear-negative, HIV-infected adults.

Methods

In this prospective study conducted at the Tshwane District Hospital and Academic TB Laboratory, Pretoria, South Africa we collected three sputum specimens an hour apart from presumptive TB cases at an antiretroviral treatment site. We analysed specimens from 236 patients. Specimen appearance and volume were recorded. All specimens were processed for culture using both standard and supplemented media.

Results

A single specimen identified 79% of PTB cases using standard media; the second and third specimens added 12.5% and 8.3% respectively. Media supplementation, sputum appearance and specimen volume had no effect on culture yield or contamination rates. The mean time to detection was reduced from 19.8 days in standard cultures to 11.8 days in nutrient supplemented cultures (p = 0.002). For every 1 ml increase in sputum volume, time to detection was decreased by a factor of 0.797 (p = 0.011).

Conclusion

Use of an inexpensive culture supplement substantially reduced time to detection and could contribute to reducing treatment delay among HIV-infected cases.

Newer Diagnostic Tests for Pulmonary Tuberculosis in Children

It has been well recognized that the diagnosis of pulmonary tuberculosis in children is often compromised by non-specific symptoms, paucibacillary nature of the disease, and the difficulty in collecting the specimen. Consequently, most tuberculosis cases in children are not confirmed, due to which the estimation of the global burden of tuberculosis in children may be inaccurate. There has also been a common misperception that diagnosis of tuberculosis and collecting respiratory specimen in children is always difficult. Because of this, microbiological confirmation of tuberculosis in young children is not routinely attempted in most endemic areas. With the emergence of HIV-related tuberculosis disease and drug-resistant tuberculosis, the availability of accurate, rapid and child friendly diagnostic tools to identify Mycobacterium tuberculosis in respiratory specimen are urgently required in endemic settings. There have been a large number of studies evaluating new diagnostic tests for tuberculosis in the past decade, but few have been evaluated in children. This review will address the developments in respiratory specimen collection and laboratory diagnostic tests of tuberculosis, with a focus on those that have been evaluated in children.

Intensified specimen collection to improve tuberculosis diagnosis in children from Rural South Africa, an observational study

BACKGROUND

In drug-resistant TB settings, specimen collection is critical for drug-susceptibility testing (DST). This observational study included multiple specimen types collected from pediatric TB suspects with the aim to determine diagnostic yield and inform clinical practice in children with drug-resistant and drug-susceptible TB.

METHODS

From 03/2009-07/2010, TB suspects aged ≥6 months and ≤12 years were recruited among outpatient and inpatient settings. Subjects were new TB suspects or had persistent symptoms despite ≥2 months of TB treatment. The protocol included collection of a single blood and urine specimen, a single sputum induction and, if inpatients and <5 years of age, collection of 3 gastric aspirates (GA). Samples were cultured on solid and/or liquid media. DST was by 1% proportion method.

RESULTS

Among 118 children with possible, probable or confirmed TB, the mean age was 4.9 years [SD 3.2] and 64 (62%) of those tested were HIV-positive. Eight (7%) subjects were culture-positive from at least one specimen; yield did not differ by HIV status or TB treatment history. Among those with positive cultures, 7/8 (88%) were from induced sputum, 5/6 (83%) from GA, 3/8 (38%) from blood, and 3/7 (43%) from urine. In subjects with both induced sputum and GA collection, sputum provided one additional case compared to GA. Multidrug resistant (MDR)-TB was detected by urine culture alone in one child >5 years old. Pan-resistant extensively drug resistant (XDR)-TB was identified by cultures from all sites in one subject.

CONCLUSIONS

TB was cultured from HIV-positive and -negative children, and allowed for identification of MDR and XDR-TB cases. Urine and induced sputum each provided an additional TB diagnosis and, when compared to GA, may be considered a less invasive, same-day method of specimen collection for childhood TB suspects. This study illustrates the continued challenges and limitations of available strategies for pediatric TB diagnostics.

Evaluation of new strategies for the diagnosis of tuberculosis among pediatric contacts of tuberculosis patients

BACKGROUND

In young children, underdiagnosis and diagnostic delay have an adverse effect on morbidity and mortality of tuberculosis (TB). This study evaluated new strategies for early TB diagnosis using an outpatient protocol in children between 0 and 5 years of age, with a recent household TB contact.

METHODS

Case recruitment was performed in Manaus, Amazonas, Brazil, from 2008 to 2009. Epidemiologic and clinical data, tuberculin test, chest radiograph and 2 induced sputum respiratory samples from each participant were obtained. Laboratory diagnosis was based on Lowenstein-Jensen (LJ) culture, mycobacteria growth indicator tube (MGIT) and polymerase chain reaction. We conducted a study of comparison of diagnostic tests and a study of cases and controls to identify the clinical characteristics of the population with positive culture and polymerase chain reaction results.

RESULTS

A total of 102 children were evaluated. Thirty-two fulfilled criteria of suspicion of TB. MGIT was more sensitive (P = 0.035) and faster (P < 0.001) than LJ. Clinical score, MGIT, LJ and polymerase chain reaction presented no concordance or slight concordance. A positive MGIT culture was only associated with a strong tuberculin test reaction (P = 0.026). The combination of MGIT with the clinical score allowed the diagnosis of 33% more cases with little or no symptomatology compared with the exclusive use of the clinical classification.

CONCLUSIONS

The sensitivity and speed of MGIT demonstrate the utility of liquid cultures for the diagnosis in children. Furthermore, these results suggest that the use of MGIT in children presenting recent household TB contact and a strong tuberculin test reaction may be a strategy to improve early TB diagnosis.

Childhood tuberculosis: an emerging and previously neglected problem

Although awareness is growing, childhood tuberculosis (TB) remains a neglected disease in many resource-limited settings. In part this reflects operational difficulties, lack of visibility in official reports, as well as perceptions that children tend to develop mild disease, contribute little to disease transmission, and do not affect epidemic control. At an international level there is greater appreciation that children contribute significantly to the global TB disease burden and suffer severe TB-related morbidity and mortality, particularly in TB-endemic areas, where the disease often remains undiagnosed. However, this is not always the case at the national or local level and there remains an urgent need for feasible and implementable policies to guide clinical practice. Pediatric TB can be regarded as an emerging epidemic in areas where the adult epidemic remains out of control and Mycobacterium tuberculosis transmission is ongoing. This article reviews important concepts, challenges, and management principles related to childhood TB; it also summarizes the main priorities for future research.

Tuberculosis during the first year of antiretroviral therapy in a South African cohort using an intensive pretreatment screening strategy

OBJECTIVE

To determine the baseline prevalence of tuberculosis (TB) in a cohort using a strategy of intensive pretreatment screening for TB and the subsequent incidence rate and temporal distribution of cases during the first year of antiretroviral therapy (ART).

DESIGN

Prospective observational community-based ART cohort in South Africa.

METHODS

Adults enrolling for ART and who did not have a current TB diagnosis were intensively screened for TB at baseline using culture of two sputum samples, chest radiography and investigations for extrapulmonary disease as required. Patients who developed symptoms consistent with incident TB during ART were similarly investigated.

RESULTS

Two hundred forty-one patients had a median CD4 cell count of 125 cells/microl (interquartile range 70-186) and 200 (83%) started ART. TB was diagnosed in 87 (36%) patients, with 82% of pulmonary cases being culture-proven. Most TB cases (87%) were prevalent disease detectable at baseline, whereas just 11 (13%) were incident cases that presented during the first year of ART. The incidence rate during 0-4 months of ART was similar to the rate during months 5-12 of ART [10.9 (95% confidence interval [CI] 4.6-23.3) cases per 100 person-years versus 8.1 (95% CI 3.6-18.0) cases per 100 person-years].

CONCLUSION

Systematic culture-based screening detected a very high burden of prevalent TB present at baseline. This intensified screening strategy was associated with an approximately two-fold lower incidence rate in the first 4 months of ART than previously observed in this cohort. This suggests that many incident cases of symptomatic TB presenting during early ART can be detected as prevalent disease prior to ART initiation using sensitive diagnostic tests.