Gram Negative Coccobacilli
A 2-year old child has a high fever and is irritable. He has a still neck. Gram strain smear of spinal fluid reveals gram-negative, small pleomorphic coccobacillary organisms. What is the most appropriate procedure to following in order to reach an etiological diagnosis? (AIIMS Nov 2009)
|A||Culture the spinal fluid in the chocolate agar and identity the organism by growth factors|
|B||Culture the spinal fluid in mannitol-salt agar|
|C||Perform a catalase test with the isolated organism|
|D||Perform a coagulase test with the isolated organism|
a. Meningitis caused by H. influenzae cannot be distinguished on clinical grounds from that caused by pneumo cocci or meningococci. The symptoms described are typical for all three organisms.
b. H. influenzae is a small, gram-negative rod with a polysaccharide capsule. It is able to grow on laboratory media if two factors are added. Heme (factor X) and NAD (factor V) provide for energy production. Use of the conjugate vaccine (type b polysaccharide) reduces the disease incidence more than 90%.
c. Pneumococci are gram-positive diplococci, and meningococci are gram-negative diplococci, which grow on blood agar and chocolate agar with no X and V factors needed, respectively.