Use of boronic acid disk methods to detect the combined expression of plasmid-mediated AmpC beta-lactamases and extended-spectrum beta-lactamases in clinical isolates of Klebsiella spp., Salmonella spp., and Proteus mirabilis.
A study using boronic acid (BA), an AmpC enzyme inhibitor, was designed to detect the combined expression of plasmid-mediated AmpC beta-lactamases (pAmpCs) and extended-spectrum beta-lactamases (ESBLs) in bacterial isolates naturally lacking chromosomal ampC genes. A total of 122 Klebsiella spp., Salmonella spp., and Proteus mirabilis isolates producing or nonproducing pAmpCs and/or ESBLs were analyzed. Detection of genes encoding ESBLs and AmpCs was confirmed by polymerase chain reaction (PCR) followed by sequencing of PCR products. A > or = 5-mm increase in zone diameter for i) cefoxitin (FOX) and/or cefotetan (CTT) containing BA versus FOX and/or CTT alone was considered positive for AmpC; ii) ceftazidime (CAZ)-clavulanate (CA) and/or cefotaxime (CTX)-CA tested in combination with BA versus CAZ and/or CTX containing BA was considered positive for ESBL. The disk tests of FOX and/or CTT alone and with BA detected 98.4% of organisms producing pAmpCs. All of the 21 pAmpC and ESBL coproducers were accurately detected ESBL by the disk tests of CTX-CA and/or CAZ-CA containing BA and CTX and/or CAZ containing BA. In conclusion, The BA disk test using Clinical and Laboratory Standards Institute methodology is simple and very efficient method to detect pAmpC and ESBL in organisms naturally lacking chromosomal AmpC enzymes. In particular, the method accurately detects the isolates that harbor both AmpCs and ESBLs.
Song
Wonkeun
W
Department of Laboratory Medicine, Hallym University College of Medicine, Seoul, South Korea.
Jeong
Seok Hoon
SH
Kim
Jae-Seok
JS
Kim
Han-Sung
HS
Shin
Dong Hun
DH
Roh
Kyoung Ho
KH
Lee
Kyu Man
KM
D001426:Bacterial Proteins / Q000032:analysis* / Q000737:chemistry; D001897:Boronic Acids / Q000494:pharmacology; D052978:Disk Diffusion Antimicrobial Tests / Q000379:methods*; D006801:Humans; D007709:Klebsiella / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D010957:Plasmids; D011513:Proteus mirabilis / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D012475:Salmonella / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D001618:beta-Lactamases / Q000032:analysis* / Q000737:chemistry / Q000235:genetics
D001426:Bacterial Proteins; D001897:Boronic Acids; C048795:AmpC beta-lactamases; D001618:beta-Lactamases; C010686:benzeneboronic acid