Clinical Microbiology and Infection publica este artículo de investigación

1 de abril de 2006

Objectives: Haemophilus parasuis is a commensal organism of the upper respiratory tract of conventional pigs that, under appropriate conditions, can cause the Glasser disease, characterized by severe systemic infection, fibrinous polyserositis, arthritis and meningitis. This is an emerging infection with increasing importance in swine production. In our laboratory, we are detecting an increase in the prevalence of resistance to beta-lactam antibiotics in H. parasuis, being this antimicrobial family the first clinical election against respiratory tract infections in swine. Resistance to beta-lactam antimicrobials has yet not been described nor characterized in H. parasuis. Methods: Antimicrobial susceptibility test and MICs were performed folowing NCCLS standard procedures. Identification by PCR was performed with modified procedure of Oliveira, S. et al, 2001. Nitrocefine test was done using OXOID beta-lactamase identification sticks. CAMP test was performed following standard procedures. DNA digestions and cloning manipulation were performed following standard procedures. Results: Phenotypic characteristics and specific tests were used for presumptive identification of H. parasuis. We have developed a PCR based on specific amplification of 821 pb from the coding gene of the 16S subunit rRNA. We confirmed 67 H. parasuis isolates and tested them for antimicrobial susceptibility, 10 were highly resistant to ampicillin (MIC >/= 32 microg/ml). All resistant isolates showed positive reaction to the nitrocefine test, indicating that beta-lactamases enzymes are involved in this phenomenon. This kind of resistance mechanism is usually harboured in plasmid in other swine respiratory pathogens. The plasmid profile analysis of these strains in agarose gel electrophoresis, after digestion with PstI, was indifferenciable in 8 of the 10 strains. We attempted to transform plasmid DNA directly into E. coli altuogh results were negative, indicating that replication origin is specific to Haemophilus spp. Currently we are cloning the gene responsible for this phenotype in H. parasuis. Conclusion: We have identified beta-lactam resistance in H. parasuis. Resistance is due to beta-lactamases. We are characterizing the genetic determinants responsible for this emerging phenotype

San Millan A., Escudero JA., Catalan A., Porrero MC., Dominguez L., Moreno MA. y Gonzalez-Zorn B..

R1940 Beta-lactam resistance in Haemophilus parasuis

	Departamento de Sanidad Animal. Facultad de Veterinaria. Universidad Complutense (UCM).
	Servicio de Zoonosis de Transmisión Alimentaria y Resistencia a Antimicrobianos (ZTA). Centro de Vigilancia Sanitaria Veterinaria (VISAVET). Universidad Complutense (UCM).