Mycobacterium africanum--review of an important cause of human tuberculosis in West Africa

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pulmonary tuberculosis 1 infectiousdiseases
pyrazinamide 1 infectiousdiseasesdrugs
tuberculosis 67 infectiousdiseases

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pyrazinamide 4993 Mycobacterium africanum[3]. Like M. tuberculosis, M. africanum strains were found to be sensitive to pyrazinamide . However, like M. bovis, M. africanum tended to be nitrate negative, a weak producer of niacin, and
Select Disease Character Offset Disease Term Instance
pulmonary tuberculosis 962 West African 2. These lineages are restricted to West Africa, where they cause up to half of human pulmonary tuberculosis . In this review we discuss the definition of M. africanum, describe the prevalence and restricted geographical
tuberculosis 787 9/2010AbstractMycobacterium africanum consists of two phylogenetically distinct lineages within the Mycobacterium tuberculosis complex, known as M. africanum West African 1 and M. africanum West African 2. These lineages are restricted
tuberculosis 972 African 2. These lineages are restricted to West Africa, where they cause up to half of human pulmonary tuberculosis . In this review we discuss the definition of M. africanum, describe the prevalence and restricted geographical
tuberculosis 1285 in animals, and summarize the phenotypic differences described thus far between M. africanum and M. tuberculosis sensu stricto.IntroductionMycobacterium africanum causes up to half of human tuberculosis (TB) in West
tuberculosis 1375 africanum and M. tuberculosis sensu stricto.IntroductionMycobacterium africanum causes up to half of human tuberculosis (TB) in West Africa [1],[2]. It was first described as a distinct sub-species within the Mycobacterium
tuberculosis 1491 (TB) in West Africa [1],[2]. It was first described as a distinct sub-species within the Mycobacterium tuberculosis complex (MTBC) by Castets and colleagues in 1968 [3]. M. africanum yields variable results on classical
tuberculosis 2147 Africa [5] (Figure 1). The M. africanum type II (East African clade) has been reclassified into M. tuberculosis sensu stricto (Figure 1) [4], and is indicated as “Uganda” genotype in Figure 2. Castets wrote a
tuberculosis 3042 [16].10.1371/journal.pntd.0000744.g002Figure 2The position of M. africanum in the global phylogeny of the M. tuberculosis complex (MTBC) as originally published by Hershberg et al.[23].This phylogeny is based on over 65 kb
tuberculosis 3827 humans and the animal strains are indicated in different colors. The human MTBC lineages include four M. tuberculosis lineages and the two M. africanum type I lineages. The “Uganda” genotype (formally referred to as
tuberculosis 3998 “Uganda” genotype (formally referred to as M. africanum type II), which is a sub-lineage within M. tuberculosis lineage 4 (also known as the Euro-American lineage), is also shown. These lineages are completely congruent
tuberculosis 4825 colleagues reported mycobacterial strains that, in biochemical testing, were intermediaries between M. tuberculosis and Mycobacterium bovis, and named these mycobacteria Mycobacterium africanum[3]. Like M. tuberculosis,
tuberculosis 4928 tuberculosis and Mycobacterium bovis, and named these mycobacteria Mycobacterium africanum[3]. Like M. tuberculosis , M. africanum strains were found to be sensitive to pyrazinamide. However, like M. bovis, M. africanum
tuberculosis 5347 isolates from Ghana in 1969 [9]. On Lowenstein-Jensen solid agar, M. africanum grew more slowly than M. tuberculosis , with cultures occasionally yielding growth only after 10 weeks, compared to 3–4 weeks in M. tuberculosis[10],
tuberculosis 5455 tuberculosis, with cultures occasionally yielding growth only after 10 weeks, compared to 3–4 weeks in M. tuberculosis [10], [11]. Castets thus recommended a 90-day incubation for isolation of M. africanum[6]. In minimal
tuberculosis 6047 corresponded with the former East African M. africanum type II (i.e., today's Uganda genotype of M. tuberculosis ) [13], [14]. However, studies based on molecular typing have shown that M. africanum isolates can exhibit
tuberculosis 6886 MAF2 [2], [16].10.1371/journal.pntd.0000744.t001Table 1Classification of M. africanum Relative to M. tuberculosis and M. bovis.CharacteristicM. africanum Type IM. tuberculosisM. bovisReferenceWest African 1West African
tuberculosis 6948 1Classification of M. africanum Relative to M. tuberculosis and M. bovis.CharacteristicM. africanum Type IM. tuberculosis M. bovisReferenceWest African 1West African 2Morphological[3]Colony appearanceDysgonicDysgonicEugonicDysgonicDepth
tuberculosis 7998 are required for classification, as such spoligotype patterns could also indicate Euro-American M. tuberculosis . Members of MAF1 typically show more than five IS6110 copies and MAF2 generally harbors five or fewer
tuberculosis 8170 copies and MAF2 generally harbors five or fewer IS6110 copies [17], [18]. The completion of the first M. tuberculosis genome sequence facilitated the development of a mycobacterial classification system based on genomic
tuberculosis 8988 2) [21], [22]. These studies also demonstrated that M. africanum type II is in fact a member of M. tuberculosis sensu stricto as it contains the TbD1 deletion, which is a characteristic marker for a subset of M.
tuberculosis 9101 sensu stricto as it contains the TbD1 deletion, which is a characteristic marker for a subset of M. tuberculosis (Figure 2) [21]. Subsequent studies in which M. africanum DNA was compared to M. tuberculosis H37Rv
tuberculosis 9195 of M. tuberculosis (Figure 2) [21]. Subsequent studies in which M. africanum DNA was compared to M. tuberculosis H37Rv using comparative genome hybridization identified additional LSPs that are specific to MAF1 (RD711)
tuberculosis 10616 analysis of human remains from Egypt's Middle Kingdom (c. 2000–1600 B.C.) identified MAF2 alongside M. tuberculosis [26], [27], although M. africanum has not been identified in North or East Africa since [28] and has
tuberculosis 14804 variable results: In Ghana, no difference in drug resistance was identified between M. africanum and M. tuberculosis [49], whereas a previous regional survey identified more primary resistance among M. africanum isolates
tuberculosis 15326 [53]. A recent abstract reported lower drug resistance among MAF2 isolates from Mali relative to M. tuberculosis [54].Animal Connection of M. africanumThe proximity of MAF2 to the animal isolates on the phylogenetic
tuberculosis 16987 contacts sleeping in a different bedroom, with a similar gradient to the one seen with exposure to M. tuberculosis [63]. Close interaction between humans and monkeys is limited in West Africa, and it is unclear whether
tuberculosis 17317 animal species.Experimental Work on M. africanumA study in cows found that M. africanum, unlike M. tuberculosis , was equally pathogenic as M. bovis[62]. Other animal studies have yielded mixed results, possibly due
tuberculosis 17692 by the relative weight of the spleen, was lower for M. africanum than for the laboratory strain M. tuberculosis H37Rv. The histopathologic lesions observed in the liver resembled those seen after infection with M.
tuberculosis 18002 Ghana (where MAF1 is more prevalent than MAF2), M. africanum was found to be equally virulent as M. tuberculosis in guinea pigs, but avirulent in rabbits [9]. Isolates from Central Africa (MAF1 or M. tuberculosis)
tuberculosis 18102 tuberculosis in guinea pigs, but avirulent in rabbits [9]. Isolates from Central Africa (MAF1 or M. tuberculosis ) were found to be equally virulent in rabbits compared with M. tuberculosis[65]. Tuberculin skin tests,
tuberculosis 18178 Central Africa (MAF1 or M. tuberculosis) were found to be equally virulent in rabbits compared with M. tuberculosis [65]. Tuberculin skin tests, using purified protein derivative (PPD) derived from the respective organisms
tuberculosis 18367 from the respective organisms as well as from Mycobacterium avium, showed cross-reaction between M. tuberculosis and M. africanum PPD both in humans and in animals [66], [67].In a recent study, BALB/c and C57BL/6
tuberculosis 18683 intra-tracheal aerosol, and bacterial replication in spleen and lungs was compared to infection with M. tuberculosis H37Rv (K. Huygen, unpublished data). Significant differences in growth were observed between MAF2 isolates:
tuberculosis 18853 differences in growth were observed between MAF2 isolates: some isolates displayed the same virulence as M. tuberculosis reflected by increasing numbers of CFU in lungs, while other MAF2 isolates showed an attenuated phenotype
tuberculosis 19255 results in guinea pigs and rabbits.Clinical and Epidemiological Differences between M. africanum and M. tuberculosis In The Gambia, where we identified M. africanum (exclusively MAF2) in sputa of 38% of smear-positive
tuberculosis 19464 smear-positive TB patients, we identified various clinical and epidemiological differences between MAF2 and M. tuberculosis [68], [69]. In a recent multivariable analysis, we compared patients infected with MAF2 (n = 289)
tuberculosis 19622 analysis, we compared patients infected with MAF2 (n = 289) relative to the Euro-American lineage of M. tuberculosis (EAMTB, n = 403), which represent 90% of M. tuberculosis sensu stricto isolates in The Gambia [70].
tuberculosis 19683 relative to the Euro-American lineage of M. tuberculosis (EAMTB, n = 403), which represent 90% of M. tuberculosis sensu stricto isolates in The Gambia [70]. We found that TB patients infected with MAF2 were more likely
tuberculosis 20429 contacts were less likely to respond to ESAT-6 in an IFNγ ELISPOT assay than were those exposed to M. tuberculosis [63]. Transmission of MAF2 from TB patients to their household contacts occurred at the same rate as
tuberculosis 20553 Transmission of MAF2 from TB patients to their household contacts occurred at the same rate as that of M. tuberculosis , as measured by the tuberculin skin test at baseline and at 3 months, yet household contacts exposed
tuberculosis 20767 to MAF2 were less likely to develop TB disease in the next 2 years than were contacts exposed to M. tuberculosis [71]. The mortality on TB treatment in HIV-negative TB patients was similar between the two organisms,
tuberculosis 21051 progression to disease in HIV-negative patients suggest that MAF2 is somewhat attenuated compared to M. tuberculosis . The older age of MAF2 patients may reflect the lower rate of progression to disease. The lower rate
tuberculosis 21395 secretion, consistent with preliminary results of ESAT-6 immunoblots of culture filtrates of MAF2 and M. tuberculosis . It is unclear whether this ESAT-6 secretion defect results from the fact that the Rv3879c gene in the
tuberculosis 21822 deletion of Rv3878 to Rv3881 efficiently secreted the ESAT-6 and CFP-10 antigens. Similarly, a clinical M. tuberculosis isolate lacking Rv3878 and Rv3879c was found to secrete both ESAT-6 and CFP-10 [73], and an M. bovis
tuberculosis 22303 africanum.10.1371/journal.pntd.0000744.t003Table 3Epidemiological, Clinical, and Immunological Differences of M. africanum Relative to M. tuberculosis .CharacteristicCountryM. africanumOR(95% CI)p-ValueReferenceWest African 1West African 2Molecular clustering
tuberculosis 23293 antigen- 6 kDa; IS6110 RFLP, insertion sequence 6110 restriction fragment length polymorphisms; MTB, M. tuberculosis .Studying nearly 2,000 TB patients from Ghana, 29% of whom were infected with M. africanum (MAF1 and
tuberculosis 23438 patients from Ghana, 29% of whom were infected with M. africanum (MAF1 and MAF2 combined) as opposed to M. tuberculosis , no differences in the rates of HIV co-infection, nor chest X-ray severity, were seen between these
tuberculosis 23583 HIV co-infection, nor chest X-ray severity, were seen between these organisms [49]. HIV-negative M. tuberculosis patients were significantly more likely to have exclusively lower zone disease on chest X-ray. Chest
tuberculosis 23965 cluster) as opposed to reactivation disease. A lower clustering rate in M. africanum compared to M. tuberculosis is consistent with the lower progression to disease observed in The Gambia.Similar to early findings
tuberculosis 24163 early findings in Dakar [6], we observed a longer time to growth in culture of MAF2 relative to M. tuberculosis on primary isolation from sputum, both in liquid and solid medium, adjusted for the degree of smear
tuberculosis 24857 M. africanum did initially establish itself in the New World, but was subsequently outcompeted by M. tuberculosis , possibly due to its lower rate of progression to disease relative to M. tuberculosis. Moreover, M.
tuberculosis 24943 outcompeted by M. tuberculosis, possibly due to its lower rate of progression to disease relative to M. tuberculosis . Moreover, M. africanum may not have established itself in the indigenous American people and in their
tuberculosis 25283 described a host polymorphism found in Ghana that is associated with protection against Euro-American M. tuberculosis , yet not against M. africanum, and may thus have provided a selective advantage for M. africanum in
tuberculosis 26574 within the MTBC. We found that antigens from the TbD1 region, present in M. africanum but absent from M. tuberculosis , failed to induce a T cell response that could be measured in an IFNγ ELISPOT [76]. Availability of
tuberculosis 26961 allow us to compare the size of the reservoir of latent infection with M. africanum relative to M. tuberculosis , and to answer whether MAF2, with its lower rate of progression to disease, protects against progression
tuberculosis 27096 MAF2, with its lower rate of progression to disease, protects against progression to disease of M. tuberculosis . Such a protection could explain why MAF2, with its lower rate of progression and shared host, has not
tuberculosis 27236 explain why MAF2, with its lower rate of progression and shared host, has not been out-competed by M. tuberculosis .Understanding the genotypic differences underlying the phenotypic differences between MAF2 and M. tuberculosis
tuberculosis 27347 tuberculosis.Understanding the genotypic differences underlying the phenotypic differences between MAF2 and M. tuberculosis can greatly enhance our understanding of TB pathogenesis. To this end, the completion of the MAF2 whole
tuberculosis 27567 genome sequence will facilitate experimental studies on the biological differences between MAF2 and M. tuberculosis , such as candidate genes that may underlie the attenuated ESAT-6 response induced by MAF2. In addition,
tuberculosis 28111 phylogenetically “ancient” sub-species within the MTBC that show phenotypic differences relative to M. tuberculosis (as observed for MAF2 in The Gambia), and may be gradually outcompeted by M. tuberculosis (as suggested
tuberculosis 28201 relative to M. tuberculosis (as observed for MAF2 in The Gambia), and may be gradually outcompeted by M. tuberculosis (as suggested for MAF1 in Cameroon). Studies on MAF2 can inform on TB pathogenesis, as MAF2, if defective
tuberculosis 28751 ensure efficacy in M. africanum–endemic areas.Learning PointsM. africanum is a sub-species of the M. tuberculosis complex that consists of two distinct lineages, West African 1 and 2Unambiguous identification of M.
tuberculosis 29049 it causes up to half of human TBM. africanum West African 2 has distinct phenotypes compared to M. tuberculosis , such as a lower progression to disease in exposed contacts, despite a similar rate of transmissionInfection
tuberculosis 29743 africanum elicits an attenuated T cell response to early secreted antigenic target, 6 kDa, in patients with tuberculosis and their household contacts. J Infect Dis 193: 1279–1286.Meyer CG, Scarisbrick G, Niemann S, Browne
tuberculosis 29900 193: 1279–1286.Meyer CG, Scarisbrick G, Niemann S, Browne EN, Chinbuah MA, et al. (2008) Pulmonary tuberculosis : virulence of Mycobacterium africanum and relevance in HIV co-infection. Tuberculosis (Edinb) 88: 482–489.de
tuberculosis 30107 88: 482–489.de Jong BC, Hill PC, Aiken A, Awine T, Antonio M, et al. (2008) Progression to active tuberculosis , but not transmission, varies by Mycobacterium tuberculosis lineage in The Gambia. J Infect Dis 198:
tuberculosis 30167 M, et al. (2008) Progression to active tuberculosis, but not transmission, varies by Mycobacterium tuberculosis lineage in The Gambia. J Infect Dis 198: 1037–1043.Hershberg R, Lipatov M, Small PM, Sheffer H, Niemann
tuberculosis 30346 Lipatov M, Small PM, Sheffer H, Niemann S, et al. (2008) High functional diversity in Mycobacterium tuberculosis driven by genetic drift and human demography. PLoS Biol 6: e311. doi:10.1371/journal.pbio.0060311.Supporting

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