Transmission of Drug-Resistant Tuberculosis in Texas and Mexico

Quitugua, Teresa; Seaworth, Barbara; Weis, Stephen E.; Taylor, Jeffery P.; Gillette, John S.; Rosas, Ishmael I.; Jost, Kenneth C.; Magee, D. Mitchell; Cox, Rebecca A.

doi:10.1128/jcm.40.8.2716-2724.2002

Cited by 29 publications

(37 citation statements)

References 16 publications

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“…Since the pace of the molecular clock of the DR locus appears to be much slower than that of IS6110 and since that spoligotype has been observed in other countries (20), these patients likely were infected before they arrived in Norway. This spoligotype and other spoligotypes found in Norway had also been identified in other countries (18,20). Since many of the strains that carried fewer than five copies of IS6110 had been identified in other countries, it was possible that this was also the case for strains that carried more than four copies of IS6110.…”

Section: Discussionmentioning

confidence: 98%

“…They all carried one copy of IS6110. The remaining 47 strains had IS6110 patterns and spoligotypes that were unique in the Norwegian database, although the spoligotypes for some of these had been observed in other countries (18,20).…”

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

“…Another method, spoligotyping, involves the simultaneous detection of the presence or absence of 43 DNA spacer sequences and is superior to IS6110 RFLP analysis in discriminating isolates with fewer than five IS6110 copies (12,13,20). Spoligotyping is therefore generally used to analyze strains with fewer than five copies of IS6110 (12,13,18,20) and has been performed on such strains isolated in Norway since 1999.These methods have been used to demonstrate that transmission of and reinfection with M. tuberculosis are uncommon in low-incidence countries and that most patients suffer from endogenous reactivation (1,4,9,10,16,22). This has also been the situation in Norway (4).…”

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confidence: 99%

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Continued Low Rates of Transmission of Mycobacterium tuberculosis in Norway

et al. 2003

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In this study, we determined the genetic diversity of Mycobacterium tuberculosis isolated in Norway from 1999 to 2001. The results were compared to those for strains isolated from 1994 to 1998. A total of 818 patients were diagnosed with tuberculosis (TB) during the last 3-year period. Of these cases, 576 (70%) were verified by culturing, and strains from 551 patients (96%) were analyzed by the IS6110 restriction fragment length polymorphism (RFLP) method. We excluded 13 strains (2.4%) from the analyses, since they were found to represent false-positive samples. A total of 67 strains (12%) that carried fewer than five copies of IS6110 were analyzed by spoligotyping. The strains were from 157 patients (29%) of Norwegian origin and 381 patients (71%) of foreign origin. The rate of diversity among all of the strains was 90%, while in 1994 to 1998 it was 87%. Clusters were assumed to have arisen from recent transmission; the degree of such transmission was 10% in 1999 to 2001, while for the whole 8-year period (1994 to 2001), it was 11%. Of the 109 patients diagnosed as being part of a cluster in 1999 to 2001, 89 were infected with a strain that carried more than four copies of IS6110. Among these 89 patients, 52 (58%) were infected with a strain that had already been identified in 1994 to 1998. The results indicated that most cases of TB in Norway were due to the import of new strains rather than to transmission within the country. This finding demonstrates that screening of immigrants for TB upon arrival in Norway needs to be improved. Outbreaks, however, were caused mainly by strains that have been circulating in Norway for many years.Globally, the number of tuberculosis (TB) cases is currently increasing at 2% per year (8). Programs to keep TB from rising in low-incidence countries are challenged by international traveling and immigration from high-burden countries (2-5, 14, 15, 18, 22). In Norway, patients with a foreign background contribute substantially to the TB incidence (4, 5, 11).In recent years, DNA fingerprinting of Mycobacterium tuberculosis based on restriction fragment length polymorphism (RFLP) analysis with IS6110 as a probe has given new insight into the nature of TB transmission. It has also become an indispensable tool for quality assurance of the processing and culturing of patient samples (1, 4, 5, 7, 9, 13-16, 18, 21, 22). Since 1994, IS6110 RFLP analysis has been performed on basically all strains of M. tuberculosis isolated in Norway (4, 5). However, isolates of M. tuberculosis that possess few copies of IS6110 do not generate sufficient polymorphisms to be readily distinguished by this technique. Another method, spoligotyping, involves the simultaneous detection of the presence or absence of 43 DNA spacer sequences and is superior to IS6110 RFLP analysis in discriminating isolates with fewer than five IS6110 copies (12,13,20). Spoligotyping is therefore generally used to analyze strains with fewer than five copies of IS6110 (12,13,18,20) and has been performed on such strains isolated in...

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Section: Discussionmentioning

confidence: 98%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Continued Low Rates of Transmission of Mycobacterium tuberculosis in Norway

et al. 2003

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“…While the bulk of the global MDR-TB burden occurs in large, populous, middle-income countries, richer countries with low TB incidence rates are not spared. International clusters of drug-resistant TB cases have involved, among others, western European countries and the USA [6,7]. In many low TB incidence countries, TB patients of foreign origin are at higher risk of MDR-TB than native patients; in 18 European countries in 2012, for instance, the pooled…”

Section: @Erspublicationsmentioning

confidence: 99%

Drug resistance and tuberculosis elimination in low-incidence countries

Falzon¹,

Zellweger²,

Migliori

et al. 2014

Eur Respir J

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@ERSpublicationsCountries on track to eliminate TB in the 21st century should be vigilant about the threat of drugresistant strains http://ow.ly/AWJ36Countries that have already reduced their tuberculosis (TB) caseloads to low levels are now embarking on the road to reduce them even further and faster [1, 2]. In these countries, TB cases now predominate in subgroups of the population that are at greater risk of infection, progression to disease or unfavourable outcome, risks that oftentimes overlap within the same individual [3]. As low TB incidence countries approach the pre-elimination threshold, i.e. moving from ,100 TB cases per million population per year today to ,10 TB cases per million, it is expected that the concentration of disease in these subgroups will persist and possibly intensify as a result of the continued, natural attrition of the older population that accounts for many of the native TB cases today [4]. If the declining trend in TB incidence in these countries continues, TB will become rarer. The prospect of having fewer cases in the future does not automatically imply that the task of controlling TB becomes any lighter for national authorities. In fact, cases may become more difficult to find and to treat as a result of patient mobility, absent or incomplete healthcare coverage, lack of entitlements for those with irregular legal status, and other vulnerabilities linked to poverty, substance use, and co-existence of diseases such as HIV and diabetes, in a context of diminishing resources and expertise for TB case management. The development of resistance to anti-TB medication, which may be potentiated by some of these factors, compounds the picture even further. These epidemiological developments may put the progress towards TB elimination at risk.The large majority of the TB cases occurring in most of the world and in low TB incidence settings remains drug susceptible and potentially curable with standard, first-line regimens, which have become widely available in recent decades. One of the threats to TB elimination has been the propagation of resistance, much of it fuelled by the improper use of the drugs making up these regimens. The emergence of combined resistance to rifampicin and isoniazid, the two most effective anti-TB medicines today (multidrug-resistant (MDR)-TB), has now become a matter of global concern [5]. While the bulk of the global MDR-TB burden occurs in large, populous, middle-income countries, richer countries with low TB incidence rates are not spared. International clusters of drug-resistant TB cases have involved, among others, western European countries and the USA [6,7]. In many low TB incidence countries, TB patients of foreign origin are at higher risk of MDR-TB than native patients; in 18 European countries in 2012, for instance, the pooled

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