Laboratory Surveillance for Prospective Plasmid-Mediated AmpC ß-Lactamases in the Kinki Region of Japan

ABSTRACTExtended-spectrum ß-lactamases, plasmid-mediated AmpC ß-lactamases (PABLs), and plasmid-mediated metallo-ß-lactamases confer resistance to many ß-lactams. In Japan, although several reports exist on the prevalence of extended-spectrum ß-lactamases and metallo-ß-lactamases, the prevalence and characteristics of PABLs remain unknown. To investigate the production of PABLs, a total of 22,869 strains of 4 enterobacterial species, Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca, and Proteus mirabilis, were collected during six 6-month periods from 17 clinical laboratories in the Kinki region of Japan. PABLs were detected in 29 (0.13%) of 22,869 isolates by the 3-dimensional test, PCR analysis, and DNA sequencing analysis. PABL-positive isolates were detected among isolates from 13 laboratories. Seventeen of 13,995 (0.12%) E. coliisolates, 8 of 5,970 (0.13%) K. pneumoniaeisolates, 3 of 1,722 (0.17%) K. oxytocaisolates, and 1 of 1,182 (0.08%) P. mirabilisisolates were positive for PABLs. Of these 29 PABL-positive strains, 20 (69.0%), 6 (20.7%), 2 (6.9%), and 1 (3.4%) carried the genes for CMY-2, DHA-1, CMY-8, and MOX-1 PABLs, respectively. Pattern analysis of randomly amplified polymorphic DNA and pulsed-field gel electrophoretic analysis revealed that the prevalence of CMY-2-producing E. colistrains was not due to epidemic strains and that 3 DHA-1-producing K. pneumoniaestrains were identical, suggesting their clonal relatedness. In conclusion, the DHA-1 PABLs were predominantly present in K. pneumoniaestrains, but CMY-2 PABLs were predominantly present in E. colistrains. The present findings will provide significant information to assist in preventing the emergence and further spread of PABL-producing bacteria.