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Is Bartonella bacilliformis, endemic pathogen of the Andean areas, intrinsically resistant to quinolones?

Abstract number: R2273

Ruiz J., Flores L., Vargas M., Garcia de la Guardia R., Quispe R., Ibañez Z.B., Alvarado D., Ramirez P., del Valle L.J.

Objectives: To characterise the resistance to quinolones and the sequence of the gyrA and parC gene in Bartonella bacilliformis, responsible of the Carrion's disease in the Andean countries.

Methods: Three B. bacilliformis were included in the study. Two of them were isolated before of 1957 (CIP 57.17 and CIP 57.18, Institute Pasteur), previously to the introduction of the quinolones in the clinical practice, while the third was recovered in 1996. The specie was confirmed by amplification and sequence of the rRNA16S gene. The QRDR sequence of the gyrA and parC genes was characterised by PCR amplification and posterior DNA sequence. The susceptibility to nalidixic acid (Nal) and ciprofloxacin (Cip) was established both by disk diffusion and by the E-test method. In all cases the plates were incubated at 28°C in a 5% CO2 atmosphere and controlled once to day in order to avoid contaminations.

Results: The three strains exhibit resistance to Nal by the two tested methodologies, possessing a MIC > 256 mg/L by the E-test method. While, the two ancient isolates presents a MIC of 0.25 mg/L to Cip, and the remaining isolate has a MIC > 32 mg/L to Cip.

In accordance with that is reported in the Gene Bank, the three strains presents an Ala in the position 85 of the parC gene, equivalent to the 80 of the QRDR of the parC gene of Escherichia coli. Meanwhile, the two isolates pre-quinolone age presents a Ala in the position 91 of the gyrA gene, as is described in Gene Bank, possition equivalent to the 83 of the gyrA gene of E. coli while the remaining presents a Val.

Conclusions: Despite its isolation previous to the introduction of the quinolones in the clinical practice, the studied strains, presents a constitutive resistance to quinolones, which may be related with the presence of Ala in the position 91 and 85 of the QRDR of the quinolone-targets (GyrA and ParC). To our knowledge this is the first report of a clinical isolate of B. bacilliformis presenting an amino acid substitution in the QRDR of GyrA. These results dissapointed the current clinical guidelines that recommended the use of ciprofloxacin to treat bartonellosis in some countries of this area.

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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