Abstract
Brucellosis is a rarely encountered infection in Norway. The aim of this study was to explore all Brucella melitensis isolates collected in Norway from 1999 to 2016 in relation to origin of infection and antimicrobial resistance patterns. A total of 23 isolates were analysed by whole-genome sequencing and compared with selected sequences of B. melitensis available from NCBI. Additionally, SNP analysis in antibiotic resistance determining genes was performed. The majority belonged to the East Mediterranean clade (genotype II), while the remaining isolates belonged to the African clade (genotype III). These results indicate that human brucellosis in Norway is related to travels or migration from the Middle East, Asia or Africa, in accordance with results from Germany, Denmark and Sweden. Antibiotic susceptibility patterns were determined by broth microdilution method and/or gradient strip method. All isolates were susceptible for all tested antibiotics, except for rifampicin where phenotypical results indicated resistance or intermediate resistance in all isolates based on broth microdilution method, and in four isolates based on gradient strip testing. In contrast, screening of the rpoB gene did not reveal any mutations in the previously described rpoB “hot spot” regions related to rifampicin resistance, indicating overestimation of resistance based on phenotypical results.
Highlights
Brucellosis is a worldwide zoonotic disease, with an estimated 500 000 new cases annually[1]
13 previously published genome sequences of B. melitensis available from NCBI24 were included in this tree
The B. melitensis 16 M reference sequence grouped together with known 16 M genomes, as expected, and B. abortus B19 vaccine strain (#21) is the obvious outgroup compared to the other isolates
Summary
Brucellosis is a worldwide zoonotic disease, with an estimated 500 000 new cases annually[1]. The purpose of this study was to trace the origin of Brucella spp. infecting Norwegian patients in the period 1999 to 2016 using WGS based methods and comparison with publicly available B. melitensis sequences. Multilocus variable tandem-repeat typing analysis (MLVA) has been the method of choice for epidemiological fingerprinting of Brucella spp[15,22]. This method is limited to targeted regions in the genome. We have assessed antimicrobial resistance mechanisms in all isolates This is the first study in Norway where human brucellosis is studied in relation to geographical source and antimicrobial resistance pattern
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