Poster presentado en ICAR2010. I International Conference on Antimicrobial Research

5 de noviembre de 2010

Marchant-Mella MA. y Moreno MA.

The discovery of plasmids and transposon was the begining of the understanding of the gene mobility between bacteria of the same and different specie. In the eightees the discovery of integrons by Stokes and Hall was done through the systemic analysis of transposons and resistant plasmids which contained a large number of interrelated genes. Integrons are defined as genetic configurations having a specific recombination site in the 5´conserved region (CS), followed by a variable region where are allocated the genes cassettes captured. In the 3´CS there are usually genes conferring resistance to amonium quaternary (qacEDelta1) and sulphonamides (sul1). Another sulphonamide resistance gene (sul3), initially detected in a conjugative plasmid identified in Escherichia coli isolated from pigs, was lately also associated with class 1 integrons (Antunes et al.), after being identified in Salmonella and E coli strains. In both bacteria the integrons were lacking genes qacDeltaE1 and sul1, being replaced by the genes qacH+tnP440+sul3.


To study the frequency and evolution of this unusual integrons class 1 among E. coli strains from food producing animals.


A Spanish collection of 393 E. coli strains obtained in two periods (1998/99 and 2006) from faecal samples from pigs (PO-98/99 (N=100); PO-06 (N=97)) and broilers (AV-98/99 (N=100); AV-06 (N=96)) was previously studied for class 1 integron, detecting a high frecuency in both species being more frequent in pigs (105= 60 (PO-98/99) + 45 (PO=06)) than in broilers (81= 40 (AV-98/99) + 41 (AV-06)), decreasing in pigs and remaining stable in broilers (Marchant et al.). To study the variable region, there were used the primers described by Levesque and Roy. In those strains were the variable region could not be amplified there were considered the three integron configurations detected by Antunes et al., as a model to determine the configuration. In first place there were amplyfied the cmlA and sul3 genes using the primers described by Saenz et al., and by Perreten and Boerling, respectively. Considering the main genes present in these integrons (aadA2+cmlA+aadA1+qacH-sul3), we used the primer walking technique to link the genes contained in the integron variable region. Once obtained the diferent amplicon sizes, there were sequenced the representative onces from each group. In this study, unusual class 1 integrons were classified in two clusters; integrons with unknown 3`CS (PO-99/98 (1), PO-06 (3); AV-98/99 (1), AV-06 (5)), and integrons harbouring qacH+tnP440+sul3 (PO-99/98 (17), PO-06 (12); AV-98/99 (5), AV-06 (10)). In the last cluster five configurations were detected; dfrA12 + orfF + aadA2 + cmlA + aadA1 + qacH + tnP440 + sul3 (Antunes et al. type I), sat + psp + aadA2 + cmlA + aadA1 + qacH + tnP440 + sul3 (Antunes et al. type IIII), dfrA12 + aadA2 + cmlA + aadA1 + qacH + tnP440 , dfrA1 + aadA1 + cmlA + aadA1 + qacH + tnP440 + sul3 , dfra12 + orfF + aadA2 + (unknown genes) (probably similar to Antunes type II). In relation with integrons harbouring qacH+tnP440+sul3 in its 3`CS, there were observed a decrease in pigs (PO-98/99 (41%); PO-06 (27%)) because of diminishing of type I, and an increase in broilers (AV-98/99 (15%); AV-06 (37%) due to the rise of type III.


Despite of the low detection of these unusual integrons in previous studies, integrons harbouring qacH+tnP440+sul3 in its 3’CS, are not a new configuration, being already present in E. coli strains isolated in 1998-1999. Moreover these data indicates that they are still common in pig and broiler E. coli strains sugesting them as a potential reservoirs

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

Enlace a ICAR2010. I International Conference on Antimicrobial Research