Why tubercular lesions commonly involve apical region of lungs?

Why tubercular lesions commonly involve apical region of lungs?

3. The cavitary lesion, characteristic of tuberculous disease, is often located in the apical regions in the lungs. 4. Whereas the primary implant can occur anywhere in the lungs, for the progression from infection to disease, the tubercle bacilli must gain access to the ‘vulnerable’ regions in the apex of the lungs.

Why does TB occur in the apex of the lung?

Moreover, ex vivo experiments conducted with macrophages demonstrated that a high oxygen pressure induced a higher bacillary growth than a low oxygen pressure 39, thus explaining why most cases of lung TB develop at the apex of the lungs, where oxygen concentrations are higher 6.

What are the mechanisms of development of tuberculosis?

The main mechanism of development of fluoroquinolone resistance in M. tuberculosis is by chromosomal mutations in the quinolone resistance-determining region of gyrA or gyrB. The most frequent mutations found are at position 90 and 94 of gyrA but mutations at position 74, 88 and 91 have also been reported [78,79].

Which lobe is affected in tuberculosis?

Parenchymal disease in primary TB commonly affects the middle and lower lung zones on CXR, corresponding to the middle lobe, basal segments of lower lobes, and anterior segments of upper lobes.

What is post primary TB?

Post-primary tuberculosis, also known as reactivation tuberculosis or secondary tuberculosis usually occurs during the two years following the initial infection. Reactivation frequently occurs in the setting of decreased immunity and usually involves the lung apex.

What are the mechanisms of drug resistances in tuberculosis?

Drug resistance in TB occurs through two main mechanisms: (i) primary or transmitted drug resistance, occurs when resistant strains are transmitted to a new host, and (ii) secondary or acquired drug resistance, which occurs through the acquisition of drug resistance mutations to one or more drugs.