<prompt> If a quellungs test was done on a bacterial isolate, which one would you expect to be positive?S.pneumoniaeEnterobacterHaemophilus parainfluenzaC.diphtheriae  <response>: The quellung test determines the presence of bacterial capsules. Specific antibody is mixed with the bacterial suspension or with clinical material. The polysaccharide capsule-antibody complex is visible microscopically. The test is also termed capsular swelling. The capsules of S. pneumoniae as well as N. meningitidis, H. influenzae, and K. pneumoniae play a role in the pathogenicity of the organisms. These surface structures inhibit phagocytosis, perhaps by preventing attachment of the leukocyte pseudopod. C. diphtheriae, Enterobacter, and H. parainfluenzae are nonencapsulated. Also Know: Pneumococci are gram-positive lancet-shaped cocci arranged in pairs diplococci or sho chains . On blood agar they produce alpha-hemolysis. In contrast to viridans streptococci, they are lysed by bile or deoxycholate, and their growth is inhibited by optochin. Ref: Levinson W. 2012. Chapter 15. Gram-Positive Cocci. In W. Levinson Ed,Review of Medical Microbiology Immunology, 12e. 