Integrons detection in Escherichia coli isolates through PCR technique
Presentation by Mauricio Alejandro Marchant Mella to obtain the Master of Research. Faculty of Veterinary Medicine, Complutense University of Madrid
June 27th, 2008
Massive administration of antibiotics in human and animals has promoted the acquisition of resistances genes that can be exchanged by conjugation, transformation or transduction into the same or different bacterial species. A few decades ago, the researchers were focused in genes dissemination through plasmids and transposons as mobile elements. Nowadays the past investigations are the bases to understand the new discoveries, being integrons responsible of genetic transmission of resistance and multiresistance.
Integron or integration elements were first proposed by Strokes and Hall in 1989. The actual definition was introduced in 1995 by Hall and Collins. Integrons belongs to a family of elements potentially mobile. There has been described many class of integrones but class 1, 2 and 3 are able to integrate and spread antimicrobial resistance genes. In the eighties Strokes and Hall demonstrated that this DNA sequences has two conserved segments (5`CS and 3`CS) and a variable region where resistance genes are allocated.
Integrons are extended mainly in gram negative bacteria and are commonly associated to Enterobacteria family.
Escherichia coli is the model bacteria that we have used to study the presence of integron in healthy animals (pigs and poultry) in two periods of time, 1998-1999 and 2006, through multiplex PCR.
Preliminary result has shown that class-1 integrons are more frequent in both animal species (39% in poultry (n=196) and 49% in pigs (n=197)) than in humans 11.4%. In addition, the analysis of both periods shows different trends; a stable scenery in poultry (38% in 1998-1999 (n=100) versus 40.6% in 2006 (n=96)) and paradoxically decreasing trend in pigs (59% in 1998-1999 (n=100) versus 39% in 2006 (n=97)). Finally there is a stability on E. coli class-2 integrons being more frequent in pigs (35% in 1998-1999 (n=100); and 43% in 2006 (n=97) than in poultry (17% in 1998-1999 (n=100); and 12.5% in 2006 (n=96)). Class-3 integrons have not been detected in any of the 393 isolates studied.
