Molecular epidemiology of dairy cattle-associated Escherichia coli carrying blaCTX-M genes in Washington State.

Molecular epidemiology of dairy cattle-associated Escherichia coli carrying blaCTX-M genes in Washington State. Appl Environ Microbiol. 2018 Jan 05;: Authors: Afema JA, Ahmed S, Besser TE, Jones LP, Sischo WM, Davis MA Abstract An increase in prevalence of commensal Escherichia coli carrying blaCTX-M genes among dairy cattle was observed between 2008 and 2012 in Washington State. To study the molecular epidemiology of this change, we selected 126 blaCTX-M-positive and 126 blaCTX-M-negative isolates for multi-locus sequence typing (MLST) and antibiotic resistance phenotyping from E. coli obtained during a previous study. For 99 isolates we also determined the blaCTX-M alleles using PCR and sequencing and identified the replicon types of blaCTX-M carrying plasmids. The blaCTX-M-negative E. coli comprised 76 sequence types (STs) compared with 32 STs in blaCTX-M-positive E. coli; the blaCTX-M-positive E. coli formed three MLST clonal complexes accounting for 83% of these isolates; 52% percent of blaCTX-M-negative E. coli isolates clustered into 10 clonal complexes and the remainder were singletons. Overall, blaCTX-M-negative E. coli had more diverse genotypes that were distinct to farms whereas blaCTX-M-positive E. coli had a clonal population structure and were widely disseminated on farms in both regions included in the study. Plasmid replicon types included IncI1 which predominated, followed by IncFIB and IncFIA/FIB. blaCTX-M-15 was t...
Source: Applied and Environmental Microbiology - Category: Microbiology Authors: Tags: Appl Environ Microbiol Source Type: research