Inhibitor-based methods for detection of derepressed hyperproduction and plasmid-mediated AmpC β-lactamases / 中华检验医学杂志

ABSTRACT

Objective To investigate the reliability of using inhibitors including Phenylboronic acid (PBA)and Fqucloxacillin(FCC)in detecting derepressed hyperproduction and plasmid-mediated AmpC B-lactamases.Methods PBA and FCC were chosen as inhibitors and double-disk potentiation method and double-disk synergy method were used to detect positive and negative control strains of AmpC β-lactamases and 107 clinical isolates for AmpC β-lactamases production.The positive control strains included E.cloacae (029M),plasmid-mediated ACT-1 type of E.coli DH5a2919,MOX-1 type of k pheumoniae,LAT-2 type of E.coil.The negative control strains included E.cloacae 029(wild-type),E.coli SHV-1,E.coli SHV-2, E.coil SHV-5,E.coli TEM-1,E.coli TEM-3,k peumoniae SHV-18 and E.coli ATCC25922.We compared the results above with the three dimensional test(3-DT)to observe the accuracy in detecting AmpC-BLA.Results 3-DT together with PBA and FCC based inhibition tests showed the 4 positive control strains and the 9 negative control strains were determined as expected.AmpC-BILA was detected in 107 clinical isolates ofEnterobacteriaceaes.The positive rate of3-DTmethod is24.3%.The positive rates ofPBA.FCC double-disk potentiation method and double-disk synergy method are 30.8%(33/107),26.2%(28/107) and 23.4%(25/107),respectively.The conjugate results in two strains of P mirabilis and one strain of K.peumoniae were positive.They were all plasmid-mediated AmpC-Bi.A.There Was a higher false positive when using PBA and FCC-based double-disk potentiation method to detect the induction type of AmpC-BLA, but the accuracy of double-disk synergy method was high.Compared with the 3-DT,the coincidence rate using PBA and FCC-based double-disk synergy method is 99.1%.Conclusions Using PBA and FCC as inhibitors in the double-disk synergy test is a accurate and reliable method to detect AmpC-BLA regardless of derepressed hyperproduction type or plasmid-mediated type.