Extensively drug-resistant tuberculosis, Pakistan

The impact of antibiotic resistance on the rampant spread of infectious diseases in Pakistan: Insights from a narrative review

Background and Aims

Antibiotic resistance (ABR) is a global public health emergency which has seen an uptick in low- to middle-income countries in recent times due to a plethora of aggravating factors and has led to a whole host of setting-specific pathogens registering high rates of resistance, causing outbreaks with graver mortality and morbidity. This review analyzes available literature to determine the causes and effects of ABR and recommend solutions to the problem in a Pakistani setting.

Methods

Sources for this narrative review were identified via electronic databases using keyword search methods. The information was retrieved using databases such as PubMed and Science Direct. Additionally, websites such as CDC and World Health Organization were used to attain pertinent information. All the sources were selected as per their relevance and appropriateness toward the purpose of this review.

Results

This review details the causes by dividing them into three primary strata, namely (1) under-regulation, (2) over-prescription and self-medication, and (3) lack of medical stewardship. This is made much graver when the COVID-19 pandemic and the subsequent erratic treatment response is considered, with the pandemic augmenting already high levels of consumption. These factors have led a cascade of effects including, but not limited to, a considerable increase in ABR in pathogens to first-line drugs.

Conclusion

ABR is a serious and growing issue which will result in undesirable personal, local, and national consequences if unchecked. Mitigation and reversal of this trend is necessary by developing existing programs and investing in novel therapies and pharmaceutical research and strengthening regulatory policies and mechanisms.

Beijing genotype of Mycobacterium tuberculosis is associated with extensively drug-resistant tuberculosis: A global analysis

We found that the frequency of Beijing genotype among XDR-TB strains was high. The data in this study would help guide the TB control program, and we however need further investigation to confirm the reliability of the present findings.

Is spinal tuberculosis changing with changing time?

Introduction

Spinal tuberculosis is a chronic destructive disease with long-term morbidity. Patients are usually young especially from a poor socioeconomic background. Destruction of the intervertebral disk space and the adjacent vertebral bodies is the characteristic lesion. The dorsal spine is the most affected region with multi-level noncontiguous involvement being detected more frequently. Patients usually present with chronic back pain associated with spinal tenderness, paraplegia, spinal deformities, as well as with constitutional symptoms. Magnetic resonance imaging has proved to be more sensitive and specific for its diagnosis, but availability and affordability of this investigation remain a problem in developing countries. Anti-tuberculous drug therapy has revolutionized the treatment of this debilitating disease. Surgery is still required in selected cases especially with evolving neurological deficit, progressive deformity, intractable pain and lack of response to drug therapy. With early diagnosis and effective treatment, prognosis is generally good.

Materials/Methods: After getting permission from the clinical governance department, We collected the retrospective data of 305 patients with diagnosed spinal tuberculosis, who underwent surgical intervention.

Results

There was no significant difference in incidence among males and females. Housewives were the most affected. Lower dorsal spinal was the commonest site involved but our study didn't confirm the incidence of multi-level disease process. Anterior decompression along with Cage fixation was most frequently performed procedure.

Conclusion

Despite the availability of highly effective antituberculous drugs, advanced surgical procedure, the spinal tuberculosis still maintains its demographic profile. There has been no change in characteristics of spinal presentation of this chronic debilitating disease. Patients continue to suffer the same way as they were suffering decades ago.

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Spinal tuberculosis is a chronic destructive disease with long-term morbidity.

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The dorsal spine is the most affected region with multi-level involvement being detected.

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Analysis of data of 305 patients with diagnosed spinal tuberculosis, who underwent surgical intervention.

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Despite the availability of highly effective drugs, and surgical procedure, the spinal tuberculosis still maintains its demographic profile.

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There has been no change in characteristics of spinal presentation of this chronic debilitating disease.

Evaluation of risk factors associated with the development of MDR- and XDR-TB in a tertiary care hospital: a retrospective cohort study

Background

Drug resistant tuberculosis (DR-TB) infringes substantial burden in terms of longer treatment duration, morbidity and mortality. Timely identification of patients at risks of DR-TB will aid individualized treatment. Current study was aimed to ascertain several factors associated with DR-TB among patients attending a tertiary care hospital.

Methods

This retrospective study was conducted among patients with confirmed diagnosis of DR-TB and drug susceptible TB (DS-TB) seeking medical care from a tertiary care hospital during 2014–2019. The types of DR-TB included were rifampicin resistant tuberculosis (RR-TB), Multidrug resistant tuberculosis (MDR-TB) and extensively drug resistant tuberculosis (XDR-TB). Appropriate statistical methods were implied to evaluate the factors associated with DR-TB.

Results

Out of 580 patients, DS-TB was diagnosed in 198 (34.1%) patients while DR-TB was present in 382 patients. Of resistance cases, RR-TB, MDR-TB and XDR-TB were diagnosed in 176 (30.3%), 195 (33.6%) and 11 (1.9%) patients, respectively. Significant differences (P < 0.05) in demographics and clinico-laboratory characteristics were observed between patients with DS-TB and DR-TB. Logistic regression analysis revealed age ≤38 years (OR: 2.5), single marital status (OR: 11.1), tobacco use (OR: 2.9), previous treatment (OR: 19.2), treatment failure (OR: 9.2) and cavity on chest X-ray (OR: 30.1) as independent risk factors for MDR-TB. However, XDR-TB was independently associated with age group of ≤38 years (OR: 13.6), students (OR: 13.0), previous treatment (OR: 12.5), cavity on chest X-ray (OR: 59.6). The independent risk factors associated with RR-TB are age ≤38 years (OR: 2.8), females (OR: 5.7), unemployed (OR: 41.5), treatment failure (OR: 4.9), previous treatment (OR: 38.2) and cavity on chest X-ray (OR: 4.3). ROC curve analysis accentuate the excellent predictive accuracy of all logistic regression models as shown by AUC (0.968, P < 0.001) for MDR-TB, AUC (0.941, P < 0.001) for XDR-TB and AUC (0.962, P < 0.001) for RR-TB.

Conclusions

Current study demonstrates a sizeable extent of resistant cases among pulmonary TB patients. This study presaged significant risk of DR-TB among females, young adults, unemployed, smokers, patients with previous treatment failure and cavitation on chest X-ray. Timely identification of high risk patients will give pronounced advantages regarding appropriate choices of prevention, treatment and disease control.

DISTRIBUTION OF DR-TB BY SEX, AGE GROUPS, OCCUPATION, PROVINCE, DIVISION, DISTRICT, TYPE OF DISEASE, TYPE OF DRUG RESISTANCE, TREATMENT REGIMEN AND OUTCOME OF TREATMENT IN DR-TB POPULATION IN D.I.KHAN DIVISION, PAKISTAN

Background: Drug-resistant tuberculosis (DR-TB) is the major cause of mortality worldwide. Our objectives were to determine the distribution of DR-TB by sex, age groups, occupation, province, division, district, type of disease, type of drug resistance, treatment regimen and outcome of treatment in DR-TB population in D.I.Khan Division, Pakistan.Materials Methods: This cross-sectional study was conducted in Department of Community Medicine, Gomal Medical College, D.I.Khan, Pakistan. A sample of 286 DR-TB patients was selected consecutively from population at risk. Sex, age groups, occupation, province, division and district were demographic while type of disease, type of drug resistance, treatment regimen and outcome of treatment were research variables. All variables being nominal were described by count, percentage cumulative percentage with 95% confidence interval for proportion. Distribution of DR-TB patients by all the ten variables were substantiated by chi-square goodness-of-fit test.Results: Out of 286 DR-TB patients, 123 (43%) were men and 163 (57%) women. DR-TB cases were most prevalent in age group 15-44 years 172 (60.14%), housewife 140 (48.95%), Khyber Pakhtunkhwa 175 (61.19%), D.I.Khan Division 178 (62.24%) and district 121 (42.31%). Most common type of disease, drug resistance and treatment regimen was pulmonary TB 282 (98.60%), MDR 273 (95.45%) and longer treatment (n=273 MDR-TB) 246 (90.11%) respectively. Treatment success rate was 161 (56.29%). The observed prevalence by occupation, province, division, district and type of disease in our sample was similar to expected prevalence in population (p.05 for all), while it was different from population by sex, age groups, type of drug resistance, regimen and treatment outcome (p.05 for all).Conclusion: The prevalence of DR-TB was higher in women, age group 15-44 years, housewife, Khyber Pakhtunkhwa and D.I.Khan Division and District. Most common type of disease, drug resistance and treatment regimen was pulmonary TB, MDR and longer treatment respectively. Treatment success rate was 56.29%. The observed prevalence by occupation, province, division, district and type of disease in sample was similar to population, while it was different by sex, age groups, type of drug resistance, regimen and treatment outcome.

Understanding how geographic, demographic and treatment history impact health outcomes of patients with multi-drug-resistant tuberculosis in Pakistan, 2014-2017

Tuberculosis (TB) is one of the top 10 leading causes of morbidity and mortality worldwide [1]. In 2017, approximately 10 million people were infected with TB and 1.3 million patients faced mortality [1]. Patients with active TB can infect up to 10–15 people over a year. There is a greater risk of transmission in overcrowded areas with limited air ventilation including large family units, prisons and slums [1, 2]. Without proper diagnosis and treatment, roughly 45% of non-HIV positive TB patients face mortality [1]. With the help of global organizations and national TB treatment and control programmes, the global incidence of TB is declining by approximately 2% each year [1]. The World Health Organization (WHO) TB-strategy aims to end the TB epidemic and encourages partners to fund national TB programmes to improve diagnosis and treatment of TB. The goal is to ultimately decrease death rates by 90% and decrease incidence rates by 80% [1]. To achieve these goals, the decline in TB incidence needs to reach approximately 4–5% per year [1]. The WHO 2018 TB report identified multidrug resistant TB (MDR-TB) as the leading factor hindering that goal [1]. The incidence and spread of MDR-TB has drastically increased, where approximately 558 000 new cases of MDR-TB were diagnosed in 2017 causing more than 230 000 deaths globally [1]. MDR-TB is identified by resistance to the two most powerful anti-TB treatment drugs including isoniazid and rifampicin [3]. Patients with MDR-TB are required to start second-line anti-TB drugs (SLDs), which are limited, expensive, less effective and more toxic [1,2]. Therapy duration is one of the major limitations of second-line treatments, which may require up to two years of consistent use. Since TB affects mostly developing countries, long treatment durations and associated costs become a major challenge. In 2015, 15% of new TB cases were reported as MDR-TB, which drastically increased to 24% by 2017 [1]. Even with significant improvements in molecular tests and diagnostic methods, MDR-TB is still on the rise where the success rate of treatments is between 50 and 60% [1]. Additional characteristics including socioeconomic and sociocultural factors need to be considered when targeting and treating patients with MDR-TB.

Extensively Drug-Resistant Tuberculosis in the Time of COVID-19-How has the Landscape Changed for Pakistan?

The incidence of extensively drug-resistant tuberculosis (XDR-TB) has been rising consistently in Pakistan, and the country is likely to experience another surge of cases in the midst of the COVID-19 crisis. It is imperative to consider how the rising proportion of XDR-TB is best tackled during the pandemic; this includes finding a solution to the problem of non-adherence at the level of community-based healthcare, the utility and practicality of simultaneous testing for COVID-19 and TB, and reconciliation of the World Health Organization’s recommendation of home-based treatment with the need for frequent monitoring of anti-tubercular therapy in XDR-TB. Operational research is needed expeditiously to bypass these limitations.

Whole genome sequencing of drug resistant Mycobacterium tuberculosis isolates from a high burden tuberculosis region of North West Pakistan

Tuberculosis (TB), caused by Mycobacterium tuberculosis bacteria, is a leading infectious cause of mortality worldwide, including in Pakistan. Drug resistant M. tuberculosis is an emerging threat for TB control, making it important to detect the underlying genetic mutations, and thereby inform treatment decision making and prevent transmission. Whole genome sequencing has emerged as the new diagnostic to reliably predict drug resistance within a clinically relevant time frame, and its deployment will have the greatest impact on TB control in highly endemic regions. To evaluate the mutations leading to drug resistance and to assess for evidence of the transmission of resistant strains, 81 M. tuberculosis samples from Khyber Pakhtunkhwa province (North West Pakistan) were subjected to whole genome sequencing and standard drug susceptibility testing for eleven anti-TB drugs. We found the majority of M. tuberculosis isolates were the CAS/Delhi strain-type (lineage 3; n = 57; 70.4%) and multi-drug resistant (MDR; n = 62; 76.5%). The most frequent resistance mutations were observed in the katG and rpoB genes, conferring resistance to isoniazid and rifampicin respectively. Mutations were also observed in genes conferring resistance to other first and second-line drugs, including in pncA (pyrazinamide), embB (ethambutol), gyrA (fluoroquinolones), rrs (aminoglycosides), rpsL, rrs and giB (streptomycin) loci. Whilst the majority of mutations have been reported in global datasets, we describe unreported putative resistance markers in katG, ethA (ethionamide), gyrA and gyrB (fluoroquinolones), and pncA. Analysis of the mutations revealed that acquisition of rifampicin resistance often preceded isoniazid in our isolates. We also observed a high proportion (17.6%) of pre-MDR isolates with fluoroquinolone resistance markers, potentially due to unregulated anti-TB drug use. Our isolates were compared to previously sequenced strains from Pakistan in a combined phylogenetic tree analysis. The presence of lineage 2 was only observed in our isolates. Using a cut-off of less than ten genome-wide mutation differences between isolates, a transmission analysis revealed 18 M. tuberculosis isolates clustering within eight networks, thereby providing evidence of drug-resistant TB transmission in the Khyber Pakhtunkhwa province. Overall, we have demonstrated that drug-resistant TB isolates are circulating and transmitted in North West Pakistan. Further, we have shown the usefulness of whole genome sequencing as a diagnostic tool for characterizing M. tuberculosis isolates, which will assist future epidemiological studies and disease control activities in Pakistan.

Detection of rifampicin resistance of Mycobacterium tuberculosis using multiplex allele specific polymerase chain reaction (MAS-PCR) in Pakistan

Drug resistance in tuberculosis (TB) is a major public health challenge in developing countries such as Pakistan. Multiplex allele specific polymerase chain reaction (MAS-PCR) is a DNA amplification method that could contribute to rapid detection and control of drug resistant tuberculosis (DR-TB) in Pakistan. The purpose of this study was to test the utility of MAS-PCR to detect resistance in Pakistan. Drug susceptibility testing (DST) was used to identify rifampicin resistant and susceptible clinical isolates from TB cases in Pakistan. MAS-PCR was used to detect the most frequent mutations in the gene rpoB among 213 resistant and 37 susceptible isolates. Among 213 clinical isolates, MAS-PCR identified mutation D435Y (Asp435Tyr) in 24 (11.3%) cases, H445Y (His445Tyr) in 14 (6.6%), S450L (Ser450Leu) in 124 (58.2%) and S450W (Ser450Trp) in 18 (8.4%) cases. MAS-PCR did not detect known mutations in 33 (15.5%) cases. Among 12 cases, a novel mutation at codon 434 (Met434Ile) and a common variant at codon 435 (Asp435Tyr) was detected in rpoB gene which is indicative of double mutation. In 4 isolates, a novel mutation at codon 432 (Gln432Pro) was identified. In an additional 4 isolates, mutations Met434Val and His445Asn were identified. Moreover, a mutation in rpoB (Leu452Pro) was found in 5 isolates. DNA sequencing confirmed the absence of mutations in rpoB in the 8 remaining isolates. MAS-PCR had 88.3% sensitivity and 100% specificity using DST as the reference, which suggested that this method could be implemented as an initial marker for screening of multi-drug resistant tuberculosis (MDR-TB) in Pakistan.

The importance of Evolutionary Medicine in developing countries: A case for Pakistan's medical schools

Evolutionary Medicine (EM) is a fundamental science exploring why our bodies are plagued with disease and hindered by limitations. EM views the body as an assortment of benefits, mistakes, and compromises molded over millennia. It highlights the role of evolution in numerous diseases encountered in community and family medicine clinics of developing countries. It enables us to ask informed questions and develop novel responses to global health problems. An understanding of the field is thus crucial for budding doctors, but its study is currently limited to a handful of medical schools in high-income countries. For the developing world, Pakistan's medical schools may be excellent starting posts as the country is beset with communicable and non-communicable diseases that are shaped by evolution. Remarkably, Pakistani medical students are open to studying and incorporating EM into their training. Understanding the principles of EM could empower them to tackle growing health problems in the country. Additionally, some difficulties that western medical schools face in integrating EM into their curriculum may not be a hindrance in Pakistan. We propose solutions for the remaining challenges, including obstinate religious sentiments. Herein, we make the case that incorporating EM is particularly important in developing countries such as Pakistan and that it is achievable in its medical student body.

Predictors of poor treatment outcomes in multidrug-resistant tuberculosis patients: a retrospective cohort study

OBJECTIVES

We aimed to determine the characteristics, treatment outcomes and risk factors for poor treatment outcomes among multidrug-resistant (MDR) tuberculosis (TB) patients in Khyber Pakhtunkhwa province, Pakistan.

METHODS

A retrospective cohort study including all patients with MDR-TB who sought care at the MDR-TB unit in Peshawar was conducted between January 2012 and April 2014. Patients were followed until an outcome of TB treatment was recorded as successful (cured or completed) or unsuccessful. Binary logistic regression was used to identify predictors of poor outcome, i.e. unsuccessful treatment outcomes.

RESULTS

Overall, 535 patients were included. The proportion of female subjects was relatively higher (n = 300, 56.1%) than male subjects. The mean (standard deviation) age of patients was 30.37 (14.09) years. Of 535 patients for whom treatment outcomes were available, 402 (75.1%) were cured, 4 (0.7%) completed therapy, 34 (6.4%) had disease that failed to respond to therapy, 93 (17.4%) died and two (0.4%) defaulted; in total, 129 (24.1%) had an unsuccessful outcome. We found three significant predictors of unsuccessful treatment during multivariate logistic regression: being married (odds ratio (OR) = 2.17, 95% confidence interval (CI) 1.01, 4.66), resistance to second-line drugs (OR = 2.61, 95% CI 1.61, 4.21) and presence of extensively drug-resistant TB (OR = 7.82, 95% CI 2.90, 21.07).

CONCLUSIONS

Approximately 75% of the treatment success rate set by the Global Plan to Stop TB was achieved. Resistance to second-line drugs and presence of extensively drug-resistant TB are the main risk factors for poor treatment outcomes.

Single nucleotide polymorphisms in efflux pumps genes in extensively drug resistant Mycobacterium tuberculosis isolates from Pakistan

It is challenging to understand mechanisms of drug resistance in Mycobacterium tuberculosis (MTB) due to the large variability in resistance associated genes. Efflux pump genes contribute to drug resistance and thus add to this complexity. Efflux pump gene protein superfamilies have been characterized by genome analysis of drug resistant strains and through in vitro transcriptional studies. However, there is limited information regarding efflux pump genes in extensively drug resistant (XDR) tuberculosis (TB) isolates. Whole genome sequencing (WGS) based analysis of 37 extensively drug resistant (XDR) and five drug sensitive (DS) MTB clinical isolates was performed. Single nucleotide polymorphisms (SNPs) in efflux pump genes Rv0194, Rv1217, Rv1218, drrA, drrB, Rv1258, Rv1634, Rv2688, Rv1273, Rv1819, Rv1458, Rv1877 and Rv1250 were determined in the clinical isolates as compared with the H37Rv reference strain. Allele frequencies of SNPs identified in XDR strains were compared with DS strains. Gene expression of Rv0194, Rv2688, Rv1634, drrA and drrB was determined in XDR -TB isolates (n = 9), DS-TB strains (n = 4) and H37Rv. We identified SNPs in XDR-TB isolates which were either unique or present at very low frequencies in DS strains; Rv0194 G170V; Rv1217 L151R; Rv1258 P369T and G391R; Rv1273 S118G and I175T; Rv1877 I534T; Rv1250 V318X/A and S333A, and Rv2688 P156T. The expression of Rv2688 and drrB was found to be raised in XDR-TB as compared with DS-TB strains. We identified unique SNPs in efflux pump genes which may be associated with increased drug resistance in the isolates. Increased levels of Rv2688 and drrB efflux pump gene expression observed in XDR strains even in the absence of antibiotics suggests that these clinical isolates may be more refractory to treatment. Further studies are required to directly associate these mutations with increased resistance in MTB.

Emergence of fluoroquinolone resistance among drug resistant tuberculosis patients at a tertiary care facility in Karachi, Pakistan

BACKGROUND

Pakistan is classified as one of the high multi-drug resistant tuberculosis (MDR-TB) burden countries. A poorly regulated private sector, over-prescription of antibiotics and self-medication has led to augmented rates of drug-resistance in the country. Pakistan's first national anti-tuberculosis drug resistance survey identified high prevalence of fluoroquinolone resistance among MDR-TB patients. Further institutional evidence of fluoroquinolone drug-resistance can support re-evaluation of treatment regimens as well as invigorate efforts to control antibiotic resistance in the country.

FINDINGS

In this study, data for drug-susceptibility testing (DST) was retrospectively analyzed for a total of 133 patients receiving MDR-TB treatment at the Chest Department of Jinnah Postgraduate Medical Center, Karachi, Pakistan. Frequency analyses for resistance patterns was carried out and association of fluoroquinolone (ofloxacin) resistance with demographics and past TB treatment category were assessed. Within first-line drugs, resistance to isoniazid was detected in 97.7% of cases, followed by rifampicin (96.9%), pyrazinamide (86.4%), ethambutol (69.2%) and streptomycin (64.6%). Within second-line drugs, ofloxacin resistance was detected in 34.6% of cases. Resistance to ethionamide and amikacin was 2.3% and 1.6%, respectively. Combined resistance of oflaxacin and isoniazid was detected in 33.9% of cases. Age, gender and past TB treatment category were not significantly associated with resistance to ofloxacin.

CONCLUSION

Fluoroquinolone resistance was observed in an alarmingly high proportion of MDR-TB cases. Our results suggest caution in their use for empirical management of MDR-TB cases and recommended treatment regimens for MDR-TB may require re-evaluation. Greater engagement of private providers and stringent pharmacy regulations are urgently required.

High diversity of multidrug-resistant Mycobacterium tuberculosis Central Asian Strain isolates in Nepal

OBJECTIVES

Tuberculosis (TB) caused by Mycobacterium tuberculosis (MTB) poses a major public health problem in Nepal. Although it has been reported as one of the dominant genotypes of MTB in Nepal, little information on the Central Asian Strain (CAS) family is available, especially isolates related to multidrug resistance (MDR) cases. This study aimed to elucidate the genetic and epidemiological characteristics of MDR CAS isolates in Nepal.

METHODS

A total of 145 MDR CAS isolates collected in Nepal from 2008 to 2013 were characterized by spoligotyping, mycobacterial interspersed repetitive unit-variable number tandem repeat (MIRU-VNTR) analysis, and drug resistance-associated gene sequencing.

RESULTS

Spoligotyping analysis showed CAS1_Delhi SIT26 as predominant (60/145, 41.4%). However, by combining spoligotyping and MIRU-VNTR typing, it was possible to successfully discriminate all 145 isolates into 116 different types including 18 clusters with 47 isolates (clustering rate 32.4%). About a half of these clustered isolates shared the same genetic and geographical characteristics with other isolates in each cluster, and some of them shared rare point mutations in rpoB that are thought to be associated with rifampicin resistance.

CONCLUSIONS

Although the data obtained show little evidence that large outbreaks of MDR-TB caused by the CAS family have occurred in Nepal, they strongly suggest several MDR-MTB transmission cases.

Spoligotype defined lineages of Mycobacterium tuberculosis and drug resistance: Merely a casual correlation?

Drug-resistant tuberculosis (TB) is a major challenge to TB control strategy worldwide. Analysis of genetic polymorphism among drug resistant Mycobacterium tuberculosis (MTB) strains may help provide some insight into the transmission dynamics of these strains. Spoligotyping is a widely used technique to identify genetic polymorphism, based on 43 known spacers interspersed between direct repeat regions. Considerable work has been done in various parts of the world using this technique to identify and analyse the polymorphic nature of MTB. Many studies have been carried out to determine the association of drug resistance with spoligotype defined lineages, and much data has been produced over the years. New information continues to be generated. This review aims to put together the findings of relevant studies in an attempt to understand the correlation of drug resistance with spoligotype defined lineages of MTB. This would help provide a perspective of the available data that can be used as a starting point to understand the molecular epidemiology of drug resistant TB.

Association of plasma cytokines with radiological recovery in pulmonary tuberculosis patients

OBJECTIVE/BACKGROUND

The characterization of tuberculosis (TB) patients as slow or fast responders post anti-TB treatment has always been a matter of tremendous interest as slow responders are most likely to relapse and/or develop complications. Pulmonary tissue healing as assessed with radiology is the only available tool for tissue recovery but is not predictive at intake. The objective of the current study was to assess biomarkers associated with fast and slow recovery in TB patients at recruitment.

METHODS

Pulmonary TB patients (N=15) were assessed for radiological recovery serially in parallel with clinical signs and symptoms, hematological parameters, and plasma cytokines at 0months, 6months, 12months, and 24months. On the basis of differential radiological healing, patients were characterized into slow (>12months), intermediate (<12months), and fast (<6months) responders.

RESULTS

Baseline plasma cytokines (interleukin [IL]-2, -4, -6, -10, tumor necrosis factor-α, and interferon-γ) were determined using cytometric bead array. IL-2 and -4 were able to accurately differentiate slow and fast responders into two distinct clusters using hierarchal clustering analysis. Compared with fast responders, slow responders showed significantly high IL-2 and -4 at baseline (p=.001 Mann-Whitney U test).

CONCLUSION

In-depth analysis of cytokines and its association with radiological recovery in TB patients may be useful in monitoring TB patients postchemotherapy for both clinicians and TB control program.

Genome Analysis of the First Extensively Drug-Resistant (XDR) Mycobacterium tuberculosis in Malaysia Provides Insights into the Genetic Basis of Its Biology and Drug Resistance

The outbreak of extensively drug-resistant tuberculosis (XDR-TB) has become an increasing problem in many TB-burdened countries. The underlying drug resistance mechanisms, including the genetic variation favored by selective pressure in the resistant population, are partially understood. Recently, the first case of XDR-TB was reported in Malaysia. However, the detailed genotype family and mechanisms of the formation of multiple drugs resistance are unknown. We sequenced the whole genome of the UM 1072388579 strain with a 2-kb insert-size library and combined with that from previously sequenced 500-bp-insert paired-end reads to produce an improved sequence with maximal sequencing coverage across the genome. In silico spoligotyping and phylogenetic analyses demonstrated that UM 1072388579 strain belongs to an ancestral-like, non-Beijing clade of East Asia lineage. This is supported by the presence of a number of lineage-specific markers, including fadD28, embA, nuoD and pks7. Polymorphism analysis showed that the drug-susceptibility profile is correlated with the pattern of resistance mutations. Mutations in drug-efflux pumps and the cell wall biogenesis pathway such as mmpL, pks and fadD genes may play an important role in survival and adaptation of this strain to its surrounding environment. In this work, fifty-seven putative promoter SNPs were identified. Among them, we identified a novel SNP located at -4 T allele of TetR/acrR promoter as an informative marker to recognize strains of East Asian lineage. Our work indicates that the UM 1072388579 harbors both classical and uncommon SNPs that allow it to escape from inhibition by many antibiotics. This study provides a strong foundation to dissect the biology and underlying resistance mechanisms of the first reported XDR M. tuberculosis in Malaysia.

Whole genome sequencing based characterization of extensively drug-resistant Mycobacterium tuberculosis isolates from Pakistan

Improved molecular diagnostic methods for detection drug resistance in Mycobacterium tuberculosis (MTB) strains are required. Resistance to first- and second- line anti-tuberculous drugs has been associated with single nucleotide polymorphisms (SNPs) in particular genes. However, these SNPs can vary between MTB lineages therefore local data is required to describe different strain populations. We used whole genome sequencing (WGS) to characterize 37 extensively drug-resistant (XDR) MTB isolates from Pakistan and investigated 40 genes associated with drug resistance. Rifampicin resistance was attributable to SNPs in the rpoB hot-spot region. Isoniazid resistance was most commonly associated with the katG codon 315 (92%) mutation followed by inhA S94A (8%) however, one strain did not have SNPs in katG, inhA or oxyR-ahpC. All strains were pyrazimamide resistant but only 43% had pncA SNPs. Ethambutol resistant strains predominantly had embB codon 306 (62%) mutations, but additional SNPs at embB codons 406, 378 and 328 were also present. Fluoroquinolone resistance was associated with gyrA 91-94 codons in 81% of strains; four strains had only gyrB mutations, while others did not have SNPs in either gyrA or gyrB. Streptomycin resistant strains had mutations in ribosomal RNA genes; rpsL codon 43 (42%); rrs 500 region (16%), and gidB (34%) while six strains did not have mutations in any of these genes. Amikacin/kanamycin/capreomycin resistance was associated with SNPs in rrs at nt1401 (78%) and nt1484 (3%), except in seven (19%) strains. We estimate that if only the common hot-spot region targets of current commercial assays were used, the concordance between phenotypic and genotypic testing for these XDR strains would vary between rifampicin (100%), isoniazid (92%), flouroquinolones (81%), aminoglycoside (78%) and ethambutol (62%); while pncA sequencing would provide genotypic resistance in less than half the isolates. This work highlights the importance of expanded targets for drug resistance detection in MTB isolates.

Multi-drug resistant Mycobacterium tuberculosis complex genetic diversity and clues on recent transmission in Punjab, Pakistan

Multi-Drug Resistant Tuberculosis (MDR-TB), i.e. bacilli resistant to rifampicin (RIF) and isoniazid (INH), is a major Public Health concern in Pakistan according to WHO estimates (3.5% and 32% of new and retreated cases, respectively). Previous Pakistanis reports identified a correlation between being MDR and belonging to Beijing or EAI lineages in one study, and belonging to "H4"-Ural Euro-American sublineage in another study. In addition, MDR-TB transmission was suspected in Karachi. We tested MDR characteristics on a Punjab sample of 278 clinical isolates (without selection for Multi-Drug Resistance) including new and retreated cases collected from 2008 to 2012. All samples were characterized by a new, microbead-based method named "TB-SPRINT" (molecular diagnostic including spoligotype identification, and genetic resistance determinants to first-line anti-TB drugs RIF and INH). Isolates from 2011 to 2012 (n=100) were further analyzed using 24-loci MIRU-VNTR. We detected 8.7% MDR isolates (CI95%=[5.0; 12.5]), mainly among CAS lineage that predominates in this central-East region of Pakistan. Out of 20 MDR-TB cases, 12 different TB-SPRINT profiles were identified, limiting the suspicion of MDR-TB transmission. 24 MIRU-VNTR confirmed the unrelatedness of isolates with different TB-SPRINT profiles and discriminated 3 isolates with identical TB-SPRINT profiles. In conclusion, our study did not confirm any of the correlations between Multi-Drug Resistance and lineage or sublineage in Punjab, Pakistan. MDR-TB isolates were diverse indicating that transmission is not pervasive. TB-SPRINT proved useful as a first step for detecting MDR-TB likely transmission events, before more extensive genotyping such as 15 or 24 MIRU-VNTR and thorough epidemiological investigation.

Mycobacterium tuberculosis Central Asian Strain (CAS) lineage strains in Pakistan reveal lower diversity of MIRU loci than other strains

Mycobacterium tuberculosis (MTB) Central Asian Strain (CAS) lineage strains are predominant in South Asia. Mycobacterial interspersed repetitive units-variable number of tandem repeats (MIRU-VNTR) typing is an effective way of determining genetic diversity of strains. A maximum of 24 loci-based MIRU-VNTR typing can be used, however, it is important to investigate the relevance of specific MIRU loci for regional strains for more cost-effective MIRU typing. MIRU-VNTR typing was performed on MTB strains from Pakistan. Strains were comprised of CAS (n=113) and non-CAS lineages (n=87) - both multi-drug resistant (MDR) and drug susceptible. Hunter Gaston Discriminatory Index (HGDI) for each MIRU loci was interpreted as poor, moderate or highly discriminatory. Results were analyzed using Bionumerics software and miru-vntrplus database link. Clustering analysis revealed 185 different MIRU types. Eight clusters of 2 strains each were present amongst MDR (3 clusters) and drug susceptible (5 clusters) isolates. MDR clusters had orphan and Haarlem strains, whereas drug susceptible strain clusters were comprised of CAS and Beijing lineage strains. The HGDI for 15 loci-based MIRU typing of all isolates was 0.620, whereas HGDI for CAS was lower than non-CAS lineage strains (p-value: 0.023). HGDI of 8 MIRU-VNTR loci (Qub 26b, 10, 26, 4156, Mtub 04, 16, 31 and ETR-A) were all highly discriminatory. The average HGDI based on these 8 loci was significantly lower for CAS than non-CAS strains (P value: 0.03). The lower discriminatory index for CAS using both 15 and 8 MIRU loci-based analysis suggests less genetic diversity in these isolates than in other lineages. The eight highly discriminatory MIRU loci for CAS may help in monitoring the transmission of MTB strains in regions with high CAS lineage prevalence.

Multidrug-resistant tuberculosis in panama is driven by clonal expansion of a multidrug-resistant Mycobacterium tuberculosis strain related to the KZN extensively drug-resistant M. tuberculosis strain from South Africa

Multidrug-resistant tuberculosis (MDR-TB) is a significant health problem in Panama. The extent to which such cases are the result of primary or acquired resistance and the strain families involved are unknown. We performed whole-genome sequencing of a collection of 66 clinical MDR isolates, along with 31 drug-susceptible isolates, that were isolated in Panama between 2001 and 2010; 78% of the MDR isolates belong to the Latin American-Mediterranean (LAM) family. Drug resistance mutations correlated well with drug susceptibility profiles. To determine the relationships among these strains and to better understand the acquisition of resistance mutations, a phylogenetic tree was constructed based on a genome-wide single-nucleotide polymorphism analysis. The phylogenetic tree shows that the isolates are highly clustered, with a single strain (LAM9-c1) accounting for nearly one-half of the MDR isolates (29/66 isolates). The LAM9-c1 strain was most prevalent among male patients of working age and was associated with high mortality rates. Members of this cluster all share identical mutations conferring resistance to isoniazid (KatG S315T mutation), rifampin (RpoB S531L mutation), and streptomycin (rrs C517T mutation). This evidence of primary resistance supports a model in which MDR-TB in Panama is driven by clonal expansion and ongoing transmission of several strains in the LAM family, including the highly successful MDR strain LAM9-c1. The phylogenetic analysis also shows that the LAM9-c1 strain is closely related to the KwaZulu-Natal (KZN) extensively drug-resistant TB strain identified in KwaZulu-Natal, South Africa. The LAM9-c1 and KZN strains likely arose from a recent common ancestor that was transmitted between Panama and South Africa and had the capacity to tolerate an accumulation of multiple resistance mutations.

Susceptibility testing of extensively drug-resistant and pre-extensively drug-resistant Mycobacterium tuberculosis against levofloxacin, linezolid, and amoxicillin-clavulanate

Pakistan is a high-burden country for tuberculosis (TB). The emergence and increasing incidence of extensively drug-resistant (XDR) TB has been reported in Pakistan. Similarly, the prevalence of multidrug-resistant TB infections with fluoroquinolone resistance (pre-XDR) is also increasing. To treat these infections, local drug susceptibility patterns of alternate antituberculosis agents, including levofloxacin (LVX), linezolid (LZD), and amoxicillin-clavulanate (AMC), is urgently needed. The aim of this study was to determine the susceptibility frequencies of drug-resistant (DR) Mycobacterium tuberculosis against LVX, LZD, and AMC. All susceptibilities were determined on Middlebrook 7H10 agar. A critical concentration was used for LVX (1 μg/ml), whereas MICs were determined for LZD and AMC. M. tuberculosis H37Rv was used as a control strain. A total of 102 M. tuberculosis isolates (XDR, n = 59; pre-XDR, n = 43) were tested. Resistance to LVX was observed in 91.2% (93/102). Using an MIC value of 0.5 μg/ml as a cutoff, resistance to LZD (MIC ≥ 1 μg/ml) was noted in 5.9% (6/102). Although the sensitivity breakpoints are not established for AMC, the MIC values were high (>16 μg/ml) in 97.1% (99/102). Our results demonstrate that LZD may be effective for the treatment of XDR and pre-XDR cases from Pakistan. High resistance rates against LVX in our study suggest the use of this drug with caution for DR-TB cases from this area. Drug susceptibility testing against LVX and AMC may be helpful in complicated and difficult-to-manage cases.

Urbanization and Infectious Diseases: General Principles, Historical Perspectives, and Contemporary Challenges

In 2009, a major demographic line was crossed: for the first time in history, the majority of the world population lived in cities rather than in towns and countryside (Fig. 4.1). This shift has been occurring over the past 100 years, with the most rapid rate of urban growth occurring over in the latter half of the twentieth century. Urban centers in the more developed regions of the world (i.e., North America, Australia, New Zealand, and Europe) experienced earlier growth in the 1920s–1950s, and since then, the rapid rate of urban growth has been concentrated in the cities and towns of developing nations [1].

Characterization of mutations conferring extensive drug resistance to Mycobacterium tuberculosis isolates in Pakistan

The increasing incidence of extensively drug-resistant (XDR) Mycobacterium tuberculosis in high-tuberculosis-burden countries further highlights the need for improved rapid diagnostic assays. An increasing incidence of XDR M. tuberculosis strains in Pakistan has been reported, but drug resistance-associated mutations in these strains have not been evaluated previously. We sequenced the "hot-spot" regions of rpoB, katG, inhA, ahpC, gyrA, gyrB, and rrs genes in 50 XDR M. tuberculosis strains. It was observed that 2% of rifampin, 6% of isoniazid, 24% of fluoroquinolone, and 32% of aminoglycoside/capreomycin resistance in XDR M. tuberculosis strains would be undetected if only these common hot-spot regions were tested. The frequencies of resistance-conferring mutations were found to be comparable among all XDR M. tuberculosis strain families present, including the Central Asian Strain, Beijing, and East African Indian genogroups and the Unique isolates. Additional genetic loci need to be tested for detection of mutations conferring fluoroquinolone, aminoglycoside, and capreomycin resistance in order to improve molecular diagnosis of regional XDR M. tuberculosis strains.