STUDY OF HETEROGENEITY OF CHLORAMPHENICOL ACETYLTRANSFERASE (CAT) GENES IN STREPTOCOCCI AND ENTEROCOCCI BY POLYMERASE CHAIN-REACTION - CHARACTERIZATION OF A NEW CAT DETERMINANT

An assay based on the utilization of degenerate primers that enable en zymatic amplification of an internal fragment of cat genes known to be present in gram-positive cocci was developed to identify the genes en coding chloramphenicol resistance in streptococci and enterococci. The functionality of this system was illustrated by the detection of cat genes belonging to four different hydridization classes represented by the staphylococcal genes cat(pC221), cat(pC194), cat(pSC7), and the c lostridial gene catP, and by the characterization of a new streptococc al cat gene designated catS. A sequence related to the clostridial cat Q gene, which was present in one streptococcal strain, was not detecte d by this assay. These results reveal that these six cat genes account for chromosomal-borne chloramphenicol resistance in 12 group A, B, an d G streptococci tested. By contrast, only three of these six cat gene s (cat(pC221), cat(pC194), and cat(pSCS7)) were detected on the 10 ent erococcal plasmids studied here that encode resistance to chlorampheni col.