Revisiting the CNS tuberculosis with emphasis on giant tuberculomas and introducing the "outer rim excrescence sign".

Central nervous system tuberculosis is a leading cause of morbidity and mortality in developing countries with Mycobacterium tuberculosis as the main etiological agent. Classical imaging findings pose no problem for diagnosis of CNS tuberculosis. Cases of giant or solitary ring enhancing lesions are increasing which mimic other infectious and noninfectious pathologies. This is a retrospective study of 40 patients (28 male and 12 female) of either surgically or clinically proven CNS tuberculosis. Solitary tuberculomas (ring or solid enhancing) were seen in 19 patients. Four patients showed presence of two to three lesions and the lesion more than one centimeter size was categorized as 'giant tuberculoma'. Multiple lesions with other associated findings were noted in 21 patients. Total 33 patients showed solitary or multiple ring enhancing lesions. Seven patients showed solid enhancing lesions (giant tuberculoma). The "Outer rim excrescence sign" was noted in a total of 16 patients. Both brain and spinal tuberculosis was noted in six patients. Seven patients presented with meningitis and hydrocephalous which is considered as the most common manifestation in the literature. Spinal leptomeningeal involvement was seen in five patients, whereas intramedullary cord tuberculomas were noted in four patients. Profound T2W hypointensity is a reliable predictor for giant tuberculomas with intense contrast enhancement, especially in deep locations. 'Outer rim excrescence' sign may contribute in cases of ring and solid enhancing lesions, however it requires further comprehensive study with MT Imaging and MR Spectroscopy to be recorded as a differentiating feature.

Analogue-resistant mutants of Azotobacter chroococcum derepressed for nitrogenase activity and early ammonia excretion having potential as inoculants for cereal crops.

Spontaneous mutants resistant to methionine sulfoximine (Msx), methyl alanine (Mal) and methyl ammonium chloride (Mac) were derived from A. chroococcum strain A103. Msx and Mal-resistant mutants expressed 1.73 to 10.98% of the fully derepressed nitrogenase activity when grown in Burk's medium containing ammonium acetate. Mac-resistant mutants did not express nitrogenase activity in ammonium acetate supplemented medium. The mutants excreted ammonia even after 2 days of growth and some mutants excreted more ammonia as compared to the parent. Selected mutants were inoculated on wheat (Triticum aestivum) and barley (Hordeum vulgare) under field conditions. Majority of the derepressed mutants increased grain yield of wheat and barley varying from 1.2 to 33.3%. However, host-dependent effects on grain yield were observed with different mutants. Two mutants, Mal 27 and Mac 19 showed significant increase in grain yields of both the crops. The results suggest that metabolic analogue-resistant mutants of Azotobacter have potential for use as a biofertilizer for cereal crops.