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Animal Tuberculosis
Published in Lloyd N. Friedman, Martin Dedicoat, Peter D. O. Davies, Clinical Tuberculosis, 2020
Members of the M. tuberculosis complex include the following mycobacteria: M. tuberculosis, Mycobacterium africanum, Mycobacterium canetti, M. bovis, M. microti, Mycobacterium orygis, M. caprae, M. pinnipedii, and the recently recognized Mycobacterium mungi.58 WHO reported that there were 9 million new cases and 1.5 million deaths due to these mycobacteria in 2014.
Thiacetazone
Published in M. Lindsay Grayson, Sara E. Cosgrove, Suzanne M. Crowe, M. Lindsay Grayson, William Hope, James S. McCarthy, John Mills, Johan W. Mouton, David L. Paterson, Kucers’ The Use of Antibiotics, 2017
In mice and guinea pigs, thiacetazone had activity similar to streptomycin and superior to paraaminosalicylic acid (PAS) (Domagk, 1950). In a detailed study of 14 clinical isolates performed in Colarado, USA, thiacetazone was found to have poor bactericidal activity but good inhibitory capacity, with minimum inhibitory concentrations (MICs) in the range 0.08–1.2 µg/ml (Heifets et al., 1990). Primary isolates from different regions of the world may vary in their sensitivity to thiacetazone. Strains isolated in East Africa are usually more sensitive MIC 0.4 µg/ml than those found in southern India, Hong Kong, and Singapore (Citron, 1973; Ellard et al., 1974). Mycobacterium africanum is frequently resistant to thiacetazone, meaning that regimens containing this drug may be unsuitable for some patients (Abate et al., 2002; Bercion and Kuaban, 1997; van der Werf et al., 1989). As with other antituberculosis drugs, thiacetazone resistance emerges rapidly if it is used alone (Cohen et al., 1953).
Respiratory Tuberculosis
Published in Peter D O Davies, Stephen B Gordon, Geraint Davies, Clinical Tuberculosis, 2014
Tuberculosis is named after the rounded tubercles formed within infected tissues. The infection comes from mycobacteria of the M. tuberculosis complex, comprising M. tuberculosis, Mycobacterium bovis [including the M. bovis Bacille Calmette–Guerin (BCG)], Mycobacterium africanum and Mycobacterium microti [8]. More recently, Mycobacterium caprae [9] and Mycobacterium pinnipedii [10] have been included within the complex that causes TB. Infection does not always lead to disease (as will be discussed in this chapter). Environmental mycobacteria may also infect humans, particularly those with damaged lungs, immunodeficiency or co-existing malignancy. The environmental mycobacteria are tissue damaging, particularly in the lung, but are not contagious and are described in detail in Chapter 27.
Tuberculosis and leprosy associated with historical human population movements in Europe and beyond – an overview based on mycobacterial ancient DNA
Published in Annals of Human Biology, 2019
Initially, studies focussed on the detection of the MTB complex, which, in addition to M. tuberculosis (sensu stricto), contains other species associated with human infections, including Mycobacterium africanum, and closely related strains found in animal infections that may infect humans, such as Mycobacterium bovis (cattle), Mycobacterium capri (goats), Mycobacterium microti (rodents) and Mycobacterium pinnepedii (seals) (Donoghue 2016). In addition there is the smooth colony strain Mycobacterium canettii that may be ancestral to the other members of the MTB complex (Jankute et al. 2017). This is found in the Horn of Africa and appears to have an environmental habitat, although non-native inhabitants can become infected and demonstrate symptoms.
Prevalence of tuberculosis and multidrug resistant tuberculosis in the Middle East Region
Published in Expert Review of Anti-infective Therapy, 2018
Suhail Ahmad, Eiman Mokaddas, Noura M. Al-Mutairi
The natural history of TB is unlike any other infectious disease. Most active TB disease cases in humans are caused by M. tuberculosis, the world’s most successful human pathogen [1]. Some disease cases in Africa are also caused by Mycobacterium africanum while consumption of unpasteurized milk can also cause TB by Mycobacterium bovis in exposed individuals [2]. Infection is acquired by inhalation of bacilli released by sputum smear-positive pulmonary TB patients during close human contact, however, primary infection leads to clinically active TB disease in only ~10% of exposed individuals [3]. In other individuals, immune response mounted by the host arrests multiplication of tubercle bacilli, however, complete sterilization is achieved in only a sub-set of individuals while in others, infection is contained but not eradicated as some bacilli escape killing and persist in granulomatous lesions (latent TB infection, LTBI) [3–5]. The LTBI either remains dormant for several years lasting up to a lifetime or resuscitates to cause active TB, often due to waning of the host immune response [3,5]. Nearly 25–33% of the world population has LTBI and 5–10% of the infected individuals will likely develop active TB disease during their life-time [3–6]. The risk of reactivation of LTBI is much higher in individuals with underlying immunodeficiencies, diabetes, other immunocompromising/immunosuppressing conditions or co-infection with human immunodeficiency virus (HIV) [3,5,7]. Most active TB disease cases in low TB incidence/high-income countries occur in foreign-born individuals due to reactivation of previous infection while recent infection/re-infection is more common in TB endemic countries [3,5,8,9].