A new Approach for Presumptive Identification of Clinically Important Streptococci

Abstract

Several tests, bacitracin, CAMP, pyroglutamic acid-B-naphthylamide test (PYR test), bile aesculin hydrolysis, salt tolerance and pigment production tests were evaluated for their reliability and speed in presumptive identification of streptococci. Bacitracin correctly identified all of the group A streptococci but 5% of other beta haemolytic streptococci were misidentified as group A. The PYR reaction was just as sensitive but more specific for group A streptococci and the results were available within 2–3 h. The PYR reaction also effectively differentiated between enterococcal and non-enterococcal group D streptococci. Both the salt tolerance test and the PYR reaction misidentified bile aesculin positive non-group D streptococci as non-enterococcal group D streptococci. Pigment production by group B streptococci was more reliable than the CAMP test for identifying group B streptococci. The combination of PYR, bile aesculin and pigment production allowed rapid differentiation of several medically important groups of streptococci.