Screening of AmpC β-lactamases-producing Acinetobacter by cefoxitin disk

Objective To evaluate the reliability of cefoxitin(FOX) disk for screening AmpC β-lactamases produced by Acinetobacter.Methods The FOX inhibition diameter 18 mm was identified as AmpC β-lactamases positive.Polymerase chain reaction(PCR) was used as confirmatory test.Results Among 130 strains,7 strains were AmpC β-lactamases negative by FOX disk screen test,which were ampC gene negative by PCR.123 trains were AmpC β-lactamases positive,in which 38 strains were ampC gene positive by PCR.The false-positive rate of FOX disk screening AmpC β-lactamases was 92.4%.There was no false-negative result.Conclusions FOX disk screen test has poor specificity in detecting AmpC β-lactamases produced by Acinetobacter.