What is Blood culture is done for and explain in detail?
Ans. d (All). (Ref. Anantanarayan, Microbiology, 6th/pg.274, 323, 361)LEPTOSPIRA# Leptospira disappear from blood after 1st week, blood examination is helpful only in early stages.# EMJH media can be used to cultivate them.# Microscopic agglutination is specific for it, but done in reference labs.# Immunofluoroscence has no role.BRUCELLA# In Brucellosis, blood culture is most definitive method of diagnosis.# Castaneda method is recommended for it.# Many a times cultures are unsuccessful and serological tests like agglutination test are performed most often.# Rapid methods employed are -- rapid plate agglutination test,- rose Bengal card test and- milk ring test.# ELISA differentiates between acute and chronic brucellosis.TYPHOID# In typhoid, blood cultures are positive in approximately 90% cases in 1st week of fever, 75% of 2nd week, 60% of 3rd week and 25% thereafter. (MacConkey, DC A and Wilson Blair media).# Faeces culture is almost as valuable as blood culture, as viruses shed during the disease and in convalescence, but they are also positive in carrier state is a drawback. But this is particularly valuable in patients on antibiotics, as they are not eliminated from faeces.# Widal test is negative in 1st week; titres start rising after 1st week, peaks at 3rd to 4th week and then starts falling.# Urine culture can be positive in 2nd and 3rd week, that too only in 25% cases.# Bone marrow culture is positive in most of the cases, when even blood cultures are negative.Educational Point:The mnemonic BASU is vague and not advisable to remember, because the fact is:B-Blood culture+ve in any week, however 90% +ve 1st weekA-Agglutination+ve in 3rd, 4th weekS-Stool culture+ve in any week, but can also be +ve in carriersU-Urine culture+ve in 2nd and 3rd week