Lateral Antimicrobial Resistance Transfer is active in the open environment

NARDELLI MAXIMILIANO; CHAMOSA LS; CENTRÓN DANIELA; QUIROGA MARÍA PAULA; ÁLVAREZ VE; CASSINI MARCELO H.

Congreso; 1° Congresso Nazionale Congiunto SITE - UZI ? SIB ?Biodiversity: concepts, new tools and future challenges?; 2016

Società Italiana di Ecologia Unione Zoologica Italiana Società Italiana di Biogeografia

Lately,there have been recurrent findings of antimicrobial resistance genes in naturalhabitats close to human activities. In most of these studies, the environmentis viewed as a passive deposit of antimicrobial resistance mechanisms. It wasalso found that bacteria evidence biological cost and compensatory mutations inother parts of the genome for maintenance of these genes. Thus, in absence ofantimicrobial pressure, it is expected that they disappear from environmentalbacterial communities. In order to test this scenario,we obtained 11 class 1 integron-positive environmental strains from distant bacterial genera collectedin Patagonianand Paranaenseforests. We showed that 10 intI1 genes were capable of insertingclinically relevant antimicrobial gene cassettes in the native attI1site without the need of antibiotic selection. The 46% (5/11) of theenvironmental strains, including an Escherichia colisample, were found to be naturally competent for the acquisition of at leastone of the aadB and/orblaVIM-2 gene cassettes. The frequency ofrecombination in Pseudomonassp. 1SL5isolatewas 10 to 1000 times higher than in the traditional laboratory model of E. coli TOP10::IntI1 co-transformed with aadB or blaVIM-2 plasmid-borne.No significant fitness cost was found for the maintenance of both genecassettes. Native intI1 with inserted gene cassettes werestable in respective environmental strains for 30 days, proposing a scenario inwhich antimicrobial resistance genes can be stable and maintained in naturewithout antimicrobial pressure. Based on this data, a bi-directional flow ofantimicrobial resistance genes between natural and nosocomial habitats isproposed, which implies the active role of the open environment as reservoir,at the same time as recipient and donor of resistance mechanisms along time.