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Multiresistance in Pasteurella multocida is due to cohabitance of small replicons

Abstract number: P2026

San Millan A., Escudero J., Nieto S., Gutierrez B., Hidalgo L., Dominguez L., Moreno M.A., Gonzalez-Zorn B.

Objectives:Pasteurella multocida is a world-wide-distributed pathogen responsible for a large variety of diseases. In the last years there has been an increase in reports due to P. multocida causing human pneumonia and meningitis as a result of pet biting or close contact to farm animals.

Tetracyclines and b-lactams are the two main antimicrobial families used as therapeutic tool against this pathogen. The objective in this work was to study the molecular basis of antimicrobial multiresistance mechanisms in P. multocida strains.

Methods: Antimicrobial susceptibility tests were performed following CLSI standard procedures. Pulsed Field Gel Electrophoresis (PFGE) was performed after total DNA digestion with ApaI. A blaROB-1 specific probe was used for Southern Blot. Plasmid Midi Kit (Qiagen) was used for plasmid purification. DNA digestions were performed following manufacturer's instructions. Automated sequencing was carried out at Secugen S. L. (Madrid, Spain). Sequence analysis was performed with DNA Strider software (France).

Results: Out of 604 P. multocida animal isolates identified between 2002 and 2005 in our laboratory, thirteen (2.15%) showed high-level resistance to b-lactams. Resistance was due to blaROB-1 borne in plasmid pB1000, a 4613 pb replicon recently described in Haemophilus parasuis (San Millan, A et al. Antimicrob Agents Chemother. 2007, 51: 2260–4.). PFGE analysis of the isolates revealed different profiles among the strains, showing that clonal dissemination is not responsible for spread of this phenotype. In addition to b-lactam resistance six of the twelve strains were concomitantly resistant to tetracycline, five were high-level resistant to streptomycin and two were resistant to both molecules. Every single multiresistance pattern from these strains corresponded to a unique plasmid profile, indicating that resistance was related to plasmid content. Complete nucleotide sequence of all plasmids was determined. We describe seven different replicons, each one bearing one, maximum two antimicrobial resistance determinants: pB1000 (blaROB-1), p13142 (tet(O)), p9956 (tet(H)), pTYM1 (sul2, strA), pB1001 (tet(B)), pB1002 (blaROB-1) and pB1003 (sul2, strA). All plasmids could be mobilised into Escherichia coli.

Conclusion: Multiresistance in P. multocida is due to cohabitance and spread of small plasmids bearing different antimicrobial resistance determinants.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Subject:
Location: Barcelona, Spain
Presentation type:
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