An infant had high grade fever and respiratory distress at the time of presentation to the emergency room. The sample collected for blood culture was subsequently positive showing growth of a haemolytic colonies. On Gram staining these were gram positive cocci. In the screening test for identification, the suspected pathogen is likely to be susceptible to the following agent:
Correct Answer: Optochin
Description: Pneumococci are the most common cause of community-acquired pneumonia, meningitis, sepsis in splenectomized individuals, otitis media, and sinusitis. 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. Rapid diagnosis of pneumococcal meningitis can be made by detecting its capsular polysaccharide in spinal fluid using the latex agglutination test. A rapid test that detects urinary antigen (capsular polysaccharide) is also available for the diagnosis of pneumococcal pneumonia and bacteremia. Ref: Levinson W. (2012). Chapter 15. Gram-Positive Cocci. In W. Levinson (Ed), Review of Medical Microbiology & Immunology, 12e.
Category:
Microbiology
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