Rapid impact of effective treatment on transmission of multidrug-resistant tuberculosis

BACKGROUND: Effective treatment for drug-susceptible tuberculosis (TB) rapidly renders patients noninfectious, long before conversion of sputum acid-fast smear or culture to negative. Multidrug-resistant TB (MDR-TB) patients on treatment are currently assumed to remain infectious for months. While the resources required for prolonged hospitalization are a barrier to the scale-up of MDR-TB treatment, the safety of community treatment is clear. OBJECTIVES : To estimate the impact of treatment on infectiousness among MDR-TB patients. METHODS: A series of five human-to-guinea pig TB transmission studies was conducted to test various interventions for infection control. Guinea pigs in adjacent chambers were exposed to exhaust air from a hospital ward occupied by mostly sputum smear- and culture-positive MDR-TB patients. The guinea pigs then underwent tuberculin skin testing for infection. Only the control groups of guinea pigs from each study (no interventions used) provide the data for this analysis. The number of guinea pigs infected in each study is reported and correlated with Mycobacterium tuberculosis drug susceptibility relative to treatment. RESULTS : Despite exposure to presumably infectious MDR-TB patients, infection percentages among guinea pigs ranged from 1% to 77% in the five experiments conducted. In one experiment in which guinea pigs were exposed to 27 MDR-TB patients newly started on effective treatment for 3 months, there was minimal transmission. In four other experiments with greater transmission, guinea pigs had been exposed to patients with unsuspected extensively drug-resistant tuberculosis who were not on effective treatment. CONCLUSIONS : In this model, effective treatment appears to render MDR-TB patients rapidly noninfectious. Further prospective studies on this subject are needed.NIOSH R01OH009050http://www.ingentaconnect.com/content/iuatld/ijtldhb201

Molecular characterization and second-line antituberculosis drug resistance patterns of multidrug-resistant mycobacterium tuberculosis isolates from the Northern Region of South Africa

Despite South Africa being one of the high-burden multidrug-resistant tuberculosis (MDR-TB) countries, information regarding the population structure of drug-resistant Mycobacterium tuberculosis strains is limited from many regions of South Africa. This study investigated the population structure and transmission patterns of drug-resistant M. tuberculosis isolates in a highburden setting of South Africa as well as the possible association of genotypes with drug resistance and demographic characteristics. A total of 336 consecutive MDR-TB isolates from four provinces of South Africa were genotyped using spoligotyping and mycobacterial interspersed repetitive-unit–variable number tandem repeat (MIRU-VNTR) typing. Drug susceptibility testing for ofloxacin, kanamycin, and capreomycin was performed using the agar proportion method. The results showed that 4.8% of MDR-TB isolates were resistant to ofloxacin, 2.7% were resistant to kanamycin, and 4.5% were resistant to capreomycin, while 7.1% were extensively drug resistant (XDR), and the remaining 83.6% were susceptible to all of the second-line drugs tested. Spoligotyping grouped 90.8% of the isolates into 25 clusters, while 9.2% isolates were unclustered. Ninety-one percent of the 336 isolates were assigned to 21 previously described shared types, with the Beijing family being the predominant genotype in the North-West and Limpopo Provinces, while the EAI1_SOM family was the predominant genotype in the Gauteng and Mpumalanga Provinces. No association was found between genotypes and specific drug resistance patterns or demographic information. The high level of diversity and the geographical distribution of the drug-resistant M. tuberculosis isolates in this study suggest that the transmission of TB in the study settings is not caused by the clonal spread of a specific M. tuberculosis strain.http://jcm.asm.org/am2013ay201

Molecular characterization and drug susceptibility of isolates from MDR-TB patients in the Eastern Cape and North West provinces of South Africa

Thesis (PhD)--Stellenbosch University, 2016.ENGLISH SUMMARY: South Africa is among the countries facing rising numbers of Mycobacterium tuberculosis (Mtb) drug resistant strains. In 2000, DOTS-Plus strategy was introduced nationally to combat drug resistant tuberculosis (TB). This necessitated the introduction of drug susceptibility testing for second-line drugs (SLDs) in order to detect and treat cases in a timely and effective manner. However, this was only routinely implemented following the description of extensively drug resistant (XDR-TB, defined as MDR-TB plus resistance to a fluoroquinolone and a second-line injectable, in South Africa in 2006. The impact of implementing a standardized MDR-TB therapy policy in South Africa on individual treatment outcomes and acquisition of additional drug resistance has not been widely documented. Improved knowledge of factors that lead to acquisition of second-line drug resistance will help better predict who is most at risk of drug resistance and contribute to the development of new tools and strategies to combat MDR-TB. To fill this gap, we sought to determine the prevalence of SLD resistance among MDR-TB patients in the DOTS-Plus cohort and its impact on treatment outcomes for these patients in two provinces in South Africa; Eastern Cape (EC) and North West (NW) province. The results show that treatment success was strongly influenced by the setting where the patients were treated. Default and death accounted for 58.1% (193/333) of all unfavourable outcomes in provinces. The EC province had the lowest (13.4%, 51/381) cure rate and the highest default rate of 38.3%; compared to a default rate of 6.39% in NW. This study also describes the resistance patterns against second line drugs among newly diagnosed MDR-TB patients in the NW and EC province using Genotype MTBDRsl assay (version 1) and targeted sequencing of genes known to confer resistance, and how these patients acquired resistance during treatment. These finding have important implications for infection control, because undiagnosed highly resistant strains could have been transmitted to contacts during treatment. The concordance between Genotype MTBDRsl and sequencing was 82% for all gyrA gene and 67% for the rrs gene. Resistance to all drugs (including ethambutol) tested at baseline was 15.8% (47/298) and resistance to both ofloxacin and kanamycin was 1.3% (4/298). Heteroresistance associated with the gyrA and embB gene was also observed. Furthermore, the study discusses the implementation of the DOTS-Plus policy with regards to whether it significantly contributed to the emergence of XDR-TB in individual patients. Implications for implementation of standardized MDR-TB treatment in the absence of knowledge of baseline resistance are also discussed. Analysis of 48 MDR-TB patients, with initial and last available isolates, showed that 45,8% gained resistance to second line drugs during treatment which suggests that the combination of in-hospital treatment with a standardized MDR-TB treatment regimen increased the risk to the patient gaining XDR during treatment. This thesis has contributed to our understanding of drug resistance in TB, and implications of implementing standardized MDR-TB treatment in South Africa. We propose an algorithm for rapidly diagnosing patients that are at risk of extensively drug resistant tuberculosis (XDR-TB) using a combination of the methods endorsed by the World Health Organization (WHO).AFRIKAANSE OPSOMMING: Suid-Afrika is ‘n land met stygende getalle middelweerstandige stamme van Mycobacterium tuberculosis. In 2000 is die DOTS-plus strategie oor die hele land ingestel om middelweerstandige tuberkulose (TB) te beveg. Dit het die bekendstelling van middelvatbaarheidstoetsing vir tweedeliniemiddels genoodsaak om gevalle tydig en effektief op te spoor en te behandel. Dit is egter eers in 2006, na die beskrywing van uitgebreide middelweerstandige (XDR)-TB, omskryf as MDR-TB plus weerstand teen fluorokinoloon en ’n tweedelinie inspuitbare middel as roetine geïmplementeer in Suid-Afrika. Die impak van die implementering van 'n gestandaardiseerde MDR-TB-terapiebeleid op individuele behandelingsuitkomste en die opdoen van addisionele middelweerstandigheid in SA is nie goed gedokumenteer nie. Verbeterde kennis van die faktore wat tot die opdoen van tweedeliniemiddelweerstandigheid lei, sal lei tot beter voorspellings oor wie die hoogste risiko loop vir middelweerstandigheid, en ook bydra tot die ontwikkeling van nuwe middels en strategieë om MDR-TB te beveg. Ten einde hierdie gaping te vul, het ons probeer vasstel wat die voorkomssyfer van tweedeliniemiddelweerstandigheid onder MDR-TB-pasiënte in die DOTS-plus-studiegroep is en die uitwerking daarvan op behandelingsuitkomste vir hierdie pasiënte in twee provinsies in Suid-Afrika, naamlik die Oos-Kaap en Noordwes. Die resultate toon dat behandelingsukses sterk beïnvloed word deur die plek waar die pasiënte behandel is. 58.1% (193/333) van alle ongunstige uitkomste in die provinsies is te wyte aan versuiming van behandeling en sterfte. Die Oos-Kaap het die laagste genesingskoers (13.4%, 51/381) en die hoogste versuimingskoers (38.3%) gehad, in vergelyking met 'n versuimingskoers van 6.39% in Noordwes. Hierdie studie beskryf ook die weerstandspatrone teen tweedeliniemiddels onder nuut-gediagnoseerde MDR-TB-pasiënte in Noordwes en die Oos-Kaap met genotipe-MTBDRsl-toetsing (weergawe 1) en geteikende DNS volgordebapaling van gene bekend vir die oordra van weerstandigheid, en hoe hierdie pasiënte weerstand gedurende die behandeling opgebou het. Hierdie bevindinge het belangrike implikasies vir infeksiebeheer omdat ongediagnoseerde, hoogs weerstandige stamme na kontakte gedurende behandeling oorgedra kan word. Die ooreenstemming tussen die genotipe-MTBDRsl en DNS volgorde was 82% vir al die gyrA-gene en 67% vir die rrs-geen. Weerstandigheid teen alle middels (insluitende etambutol) wat op aanvangsvlak getoets is, was 15.8% (47/298) en weerstandigheid teen sowel ofloksasien as kanamisien was 1.3% (4/298). Heteroweerstandigheid wat met sowel die gyrA-geen as die embB-geen geassosieer word, is ook waargeneem. Die studie bespreek verder die implementering van die DOTS-plus beleid en of dit betekenisvol aanleiding gee tot die verskyning van XDR-TB in individuele pasiënte. Die implikasies vir die implementering van gestandaardiseerde MDR-TB-behandeling met gebrek aan enige kennis oor aanvangsweerstandigheid, word ook bespreek. Die ontleding van 48 MDR-TB pasiënte, met ’n aanvanklike en ’n laaste kultuur toon dat 45,8% weerstand teen tweedeliniemiddels gedurende behandeling opgebou het. Dit dui daarop dat die kombinasie van behandeling in 'n hospitaal met ’n gestandaardiseerde behandelingsplan die risiko vir die pasiënt verhoog om XDR gedurende behandeling op te doen. Hierdie tesis dra by tot ons kennis oor en begrip van middelweerstandigheid in TB en die implikasies van die implementering van gestandaardiseerde MDR-TB-behandeling in Suid-Afrika. Ons doen 'n algoritme aan die hand om pasiënte wat gevaar loop om uitgebreide middelweerstandige tuberkulose (XDR-TB) op te doen, vinnig te diagnoseer met 'n kombinasie van metodes wat deur die Wêreld-gesondheidsorganisasie (WGO) goedgekeur is

Stain differentiation of South African clinical isolates of Mycobacterium tuberculosis by restriction and amplified fragment length polymorphisms

DNA fingerprinting of Mycobacterium tuberculosis strain has been used in combination with conventional epidemiologic investigation, which has improved the understanding of tuberculosis transmission. Restriction Fragment Length Polymorphism (RFLP) based on IS6110 probe has become a standard method of fingerprinting of M tuberculosis. Since the technique is labour intensive and the discriminatory power of IS611 0 fingerprinting method for strains habouring only one to five copies is poor, other typing methods for typing M tuberculosis should be evaluated. In this regard, Amplified Fragment Length Polymorphism (AFLP) has the potential to overcome many of the RFLP problems. The first objective was to determine the suitability of the RFLP and AFLP techniques and to study the extent of transmission of tuberculosis in a referral hospital in South Africa. A total of 47 M tuberculosis isolates were differentiated using RFLP technique. The same samples were typed using the PCR- based AFLP technique and results were compared. The second objective was to determine the prevalence of isoniazid (INH) resistance and estimate the incidence of recent transmission of the disease in the Eastern-Cape (EC) and North-West province (NW) by using the best suited technique. RFLP grouped the 47 typed M. tuberculosis isolates into five families and four clusters. AFLP grouped the analyzed isolates (previously typed by RFLP) into two groups based on the banding patterns observed. As a result of the low degree of genotypic variation among the AFLP band pattern of M tuberculosis isolates, AFLP seemed less promising for individual strain differentiation of M tuberculosis. This technique can be used in future for differentiation of Mycobacterial species and The prevalence of INH resistance was found to be 6.7% in the EC and 8.4% in the NW province. The magnitude of recent transmission in the Eastern Cape studied by RFLP method, was found to be at 22% among the positive tuberculosis isolates identified. Transmission of TB in NW province was associated with reactivation rather than recent transmission due to lack of clustering of strains in that region.Dissertation (MSc(Microbiology))--University of Pretoria, 2006.Microbiology and Plant Pathologyunrestricte