Haemophilus influenzae clinical isolates with plasmid pB1000 bearing blaROB-1. Fitness cost and interspecies dissemination
April 1st, 2010
Antimicrobial Agents and Chemotherapy publish this investigation article
Plasmid pB1000 is a mobilizable replicon bearing the blaROB-1 ß-lactamase gene that we have recently described in Haemophilus parasuis and Pasteurella multocida animal isolates. Here, we report presence of pB1000 and a derivate plasmid, pB1000`, in four H. influenzae clinical isolates from human origin. Pulsed-field gel electrophoresis showed unrelated patterns in all strains, indicating that existence of pB1000 in H. influenzae isolates is not the consequence of clonal dissemination. The replicon can be transferred both by transformation and conjugation into H. influenzae, giving rise to ampicillin (MIC > 64 μg/ml) and cefaclor (MIC > 64 μg/ml) resistant recipients. Stability experiments showed that pB1000 is stable in H. influenzae without antimicrobial pressure for at least 60 generations. Competition experiments between isogenic H. influenzae with and without pB1000 revealed a competitive disadvantage of 9% per 10 generations of the transformant versus the recipient. Complete nucleotide sequence of nine pB1000 plasmids from human and animal isolates, as well as the epidemiological data, suggest that animal Pasteurellaceae act as antimicrobial resistance reservoir for H. influenzae. Further, being P. multocida the only member of this family able to colonize both, humans and animals, we propose P. multocida as the vehicle of pB1000 between animal- and human-adapted Pasteurellaceae
San Millan A., Garcia-Cobos S., Escudero JA., Hidalgo L., Gutierrez B., Carrilero L., Campos J. and Gonzalez-Zorn B..
