<prompt> A 71 year old female presents with fever, chills, difficulty in breathing and productive cough. She also complaints of left sided chest pain. Physical examination shows, increased VF, dullness to percussion, decreased bronchial sounds. Chest X-ray shows left lower lobe consolidation. Culture grows organisms that are catalase negative and shows positive Quellung reaction. Gram staining of organism isGram positive diplococcusGram negative diplococcusGram positive cocci in clustersGram negative rods  <response>: Answer: a Gram positive diplococcus PANIKER 9th EDITION P-223 History, Physical examination and Chest X-ray suggest pneumonia Catalase negative organism showing positive Quellung reaction indicates Streptococcus pneumoniae Gram positive cocci Catalase positive-StaphylococciCatalase negativeCoagulase positiveCoagulase negativeCoNSStreptococci Staph, aureusNovobiocin susceptible Staph.epidermidis Staph, haemolyticus Staph.hominisNovobiocin resistant Staph. saprophyticus Staph.xylosusPneumococciSTREPTOCOCCUS PNEUMONIAE PNEUMOCOCCI Capsulated, flame shaped or lanceolate diplococci MCC of lobar pneumonia, sinusitis, otitis media MCC of bacterial meningitis in adults Culture - Draughtsman or carom coin appearance Ferments inulin - tested on Hisss serum sugars Quellung reaction - capsular swelling when mixed with type specific antisera and methylene blue Virulence factors - capsular polysaccharide or specific soluble substanceSSS, pneumolysin Type 3 pneumococci is most virulent as it contains abundant capsular material Oxygen labile hemolysin and leucocidin make no contributions to virulence Biomarkers- CRP, Procalcitonin both elevated in invasive pneumococcal disease Splenectomy and sickle cell disease are important predisposing conditions for infection 