A comprehensive and contemporary “snapshot” of β-lactamases in carbapenem resistant Acinetobacter baumannii

Successful treatment of Acinetobacter baumannii infections require early and appropriate antimicrobial therapy. One of the first steps in this process is understanding which β-lactamase (bla) alleles are present and in what combinations. Thus, we performed WGS on 98 carbapenem-resistant A. baumannii (CR Ab). In most isolates, an acquired bla(OXA) carbapenemase was found in addition to the intrinsic bla(OXA) allele. The most commonly found allele was bla(OXA-23) (n = 78/98). In some isolates, bla(OXA-23) was found in addition to other carbapenemase alleles: bla(OXA-82) (n = 12/78), bla(OXA-72) (n = 2/78) and bla(OXA-24/40) (n = 1/78). Surprisingly, 20% of isolates carried carbapenemases not routinely assayed for by rapid molecular diagnostic platforms, i.e., bla(OXA-82) and bla(OXA-172); all had ISAba1 elements. In 8 CR Ab, bla(OXA-82) or bla(OXA-172) was the only carbapenemase. Both bla(OXA-24/40) and its variant bla(OXA-72) were each found in 6/98 isolates. The most prevalent ADC variants were bla(ADC-30) (21%), bla(ADC-162) (21%), and bla(ADC-212) (26%). Complete combinations are reported.