Mutational change of CTX ‐M‐15 to CTX‐M‐127 resulting in mecillinam resistant Escherichia coli during pivmecillinam treatment of a patient

In this study, we investigated the genetics behind mecillinam resistance which occurred in an extended ‐spectrum β‐lactamase‐producingEscherichia coli during pivmecillinam treatment of a patient. The genomic comparison of the two isolates points toward a mutational change of blaCTX ‐M‐15 into blaCTX‐M‐127 along with a serotype shift from rough to full‐length O25 as the mechanisms contributing to the change in mecillinam susceptibility. AbstractPivmecillinam (amdinocillin pivoxil) is the recommended first ‐choice antibiotic used to treat urinary tract infections (UTIs) in Denmark. The frequency of mutation to mecillinam (MEC) resistance is described as high in vitro; however, treatment of UTI has a good clinical response and prevalence of mecillinam resistance inEscherichia coli remains low despite many years of use. We describe occurrence of in vivo mecillinam resistance in a clinical isolate of ESBL ‐producingE.  coli following pivmecillinam treatment. The identified phenotypic differences in the mecillinam resistant isolate compared with the original mecillinam susceptible isolate were a full ‐length LPS with O‐antigen (O25), mecillinam resistance and a lower MIC for ceftazidime. Regarding genotype, the resistant isolate differed with a mutation inblaCTX ‐M‐15 toblaCTX ‐M‐127, loss of a part of a plasmid and a genomic island, respectively, and insertion of a transposase inwbbL, causing the rough phenotype. The observed mecillinam resistance...
Source: MicrobiologyOpen - Category: Microbiology Authors: Tags: ORIGINAL ARTICLE Source Type: research