Detection of extended-spectrum beta-lactamases by using boronic acid as an AmpC beta-lactamase inhibitor in clinical isolates of Klebsiella spp. and Escherichia coli.
We evaluated highly sensitive methods using boronic acid (BA) to detect extended-spectrum beta-lactamase (ESBL) production. A total of 182 clinical isolates of Klebsiella spp. (n = 118) and Escherichia coli (n = 64) were analyzed: 62 harbored only ESBLs, 80 harbored both ESBLs and plasmid-mediated AmpC beta-lactamases (pAmpCs), and 40 harbored only pAmpCs. The CLSI confirmatory test detected all isolates that produce only ESBLs but detected 85% of isolates that produce both enzymes. When a >/=5-mm increase in the zone diameter of either the cefotaxime (CTX) or the ceftazidime (CAZ) disk in the presence of both clavulanic acid (CA) and BA was considered to be a positive result, the test detected all isolates that harbor ESBLs (+/- pAmpCs) but showed frequent false-positive results (50%) for isolates that produce only pAmpCs. Meanwhile, when a >/=3-mm increase in the zone diameter of either the CTX/BA or the CAZ/BA disk in the presence of CA was considered to be a positive result, the test also detected all isolates that harbor ESBLs (+/- pAmpCs) and showed less frequent false-positive results (5%) in isolates that produce only pAmpCs. The latter new interpretive guideline has enhanced detection of ESBLs in clinical isolates of Klebsiella spp. and Escherichia coli and allowed detection of an ESBL even when potentially masked by a pAmpC.
Song
Wonkeun
W
Department of Laboratory Medicine, Kosin University College of Medicine, 34 Amnam-Dong, Suh-Gu, Busan, Republic of Korea.
Bae
Il Kwon
IK
Lee
You-Nae
YN
Lee
Chae-Hoon
CH
Lee
Sang Hee
SH
Jeong
Seok Hoon
SH
D001426:Bacterial Proteins / Q000037:antagonists & inhibitors; D001897:Boronic Acids / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004926:Escherichia coli / Q000187:drug effects* / Q000201:enzymology; D004927:Escherichia coli Infections / Q000382:microbiology; D005189:False Positive Reactions; D006801:Humans; D007709:Klebsiella / Q000187:drug effects* / Q000201:enzymology; D007710:Klebsiella Infections / Q000382:microbiology; D008826:Microbial Sensitivity Tests / Q000379:methods*; D010957:Plasmids / Q000235:genetics; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D018440:beta-Lactam Resistance; D065093:beta-Lactamase Inhibitors; D001618:beta-Lactamases / Q000378:metabolism*
D001426:Bacterial Proteins; D001897:Boronic Acids; D004791:Enzyme Inhibitors; D065093:beta-Lactamase Inhibitors; C048795:AmpC beta-lactamases; D001618:beta-Lactamases