(a) (i) Describe the morphological characteristics of *Cryptococcus neoformans* on microscopic examination. Discuss the…

Cryptococcus neoformans. On microscopic examination, C. neoformans is a narrow-based budding yeast with a thick polysaccharide capsule. In India ink or mucicarmine-stained CSF or tissue smears, the capsule appears as a clear halo around oval yeast cells, and urease positivity helps separate it from other yeasts. The capsule is the major virulence factor, inhibiting phagocytosis and allowing survival in macrophages. Pathogenesis follows inhalation of desiccated pigeon droppings or soil, producing a small pulmonary focus. In immunocompromised patients, especially HIV/AIDS with low CD4 counts, the organism multiplies in alveolar macrophages, escapes locally, and spreads haematogenously to the meninges and brain, causing meningitis, meningoencephalitis or cryptococcomas.

Meningococcaemia and meningitis. Meningococcaemia is the presence of Neisseria meningitidis in the blood, producing bacteraemia or septicaemia, often with fever, petechiae or purpura. Laboratory diagnosis of acute meningococcal meningitis begins with CSF Gram stain showing Gram-negative diplococci, followed by culture on chocolate agar or Thayer-Martin medium. CSF is typically turbid with neutrophilic pleocytosis, low glucose and raised protein. Capsular polysaccharide can be detected by latex agglutination or counterimmunoelectrophoresis, and PCR gives rapid confirmation; blood culture and skin-lesion swabs may also be positive. Prevention relies on conjugate MenACWY vaccines and MenB vaccines such as Bexsero and Trumenba. In India, MenACWY is available for outbreak or high-risk use and may be procured through UIP/State immunisation channels, while MenB vaccines are available for selected indications.

IPC definitions and bullet markings. Under the IPC, injury (Section 44) means bodily pain, disease or infirmity. Hurt (Section 319) is voluntarily causing injury, disease or bodily pain. Grievous hurt (Section 320) is a specified serious hurt: permanent privation of sight of either eye; permanent privation of hearing of either ear; privation of any member or organ of its use; extirpation of any part of the reproductive organs; permanent privation of the use of any member or organ; fracture or dislocation of bone or joint; bodily pain disabling for twenty days; or continued severe bodily pain. Secondary markings on a fired bullet are fine individual striations produced by microscopic imperfections, wear, nicks and scratches in the barrel. They are distinct from primary rifling impressions, i.e. land and groove engravings, which are class characteristics. Class characteristics identify make, model or calibre; individual characteristics identify the specific gun.

Finger impressions and DNA fingerprinting. Finger impressions are friction-ridge patterns classified as arches (plain and tented), loops (ulnar and radial) and whorls (central pocket spiral, double loop and accidental). Each pattern is further identified by minutiae such as ridges, bifurcations and dots. DNA fingerprinting identifies individuals by analysing variable DNA regions. Classically, Alec Jeffreys’ VNTR method used restriction digestion, Southern blotting and hybridisation; modern forensic practice uses STR analysis by PCR and capillary electrophoresis. Applications include paternity, kinship, disaster victim identification and criminal cases, where a match narrows the suspect pool and a mismatch excludes.

Potassium-sparing diuretics. These act on collecting duct principal cells. Spironolactone competitively antagonises aldosterone, reducing Na+ reabsorption and K+ secretion, while amiloride and triamterene directly block epithelial sodium channels. The result is mild natriuresis with potassium retention, useful when hypokalaemia must be avoided. They are used in heart failure or with other diuretics to offset potassium loss.

Zidovudine. Zidovudine is an NRTI and chain terminator used in HIV treatment, prevention of perinatal transmission, and post-exposure prophylaxis. It inhibits reverse transcriptase after phosphorylation to triphosphate. Adverse effects include myelosuppression, especially anaemia and neutropenia, lactic acidosis, hepatotoxicity, lipodystrophy, and GI intolerance; monitoring of haemoglobin and liver function is important.

Together, the answer requires ordered description of morphology, pathogenesis, laboratory steps, legal definitions, forensic identification and drug action, with public-health relevance in infection control, vaccination and safe drug use.