Prevalence of acquired AmpC β-lactamases in Enterobacteriaceae lacking inducible chromosomal ampC genes at a Spanish hospital from 1999 to 2007

In 2007, a significant increase in acquired ampC genes in Enterobacteriaceae from 0.06% in 1999 to 1.3% was observed. Proteus mirabilis showed the highest prevalence (0.95%) and CMY-2 was the most prevalent AmpC enzyme (66.7%). Other enzymes such as CMY-4, DHA-1, ACC-1, and three new enzymes called CMY-25, CMY-27 and CMY-40 were detected. Seven out of the 117 isolates (6%) also produced an extended-spectrum β-lactamase. As acquired AmpC enzymes are likely to become a serious public health issue worldwide, close surveillance is necessary to curb their spread.