pCF10 MEDIATES INTERSPECIES DISSEMINATION OF ANTIBIOTIC RESISTANCE DETERMINANTS IN MIXED SPECIES BIOFILMS

Abstract

Enterococcus faecalis is a commensal bacterium, which upon acquisition of virulence factors on mobile genetic elements can cause sepsis, urinary tract infections and endocarditis. E. faecalis isolates can be multi-drug resistant and have been implicated in the dissemination of antibiotic resistance genes to other genera. Although the host range of pheromone inducible conjugative plasmids is restricted to Enterococci, they often carry transposons, which are capable of transposing into the chromosome of other genera. The plasmid pCF10 contains the antibiotic resistance gene tetM on a conjugative transposon Tn925. Tn925 is a Tn916-like plasmid and is capable of pCF10-independent conjugative transfer to multiple bacterial species at low levels. Biofilms are communities of bacteria growing within a matrix. In biofilms, bacteria are more difficult to kill because of their lower susceptibility to antibiotics. In hospital settings, biofilms can grow on medically implanted devices, catheters or even human tissue. In mixed species biofilms, antibiotic resistances are able to be transferred through horizontal gene transfer from E. faecalis to other bacterial species. In mixed species biofilms, it has been show that Tn925 can transpose into S. aureus at rates of 10-8 by Ella Massie Schuh. Using static mixed species biofilms, the transfer of tetM from E. faecalis to S. aureus was studied, hoping to better understand the underlying mechanisms. The goal of these studies was to determine if residence on pCF10 increased the transfer frequency of Tn925 in mixed species biofilms. Mixed species biofilms containing E. faecalis (pCF10) and S. aureus (pALC2073aPSM) were established and pCF10 conjugation was induced with pheromone cCF10. Transfer of Tn925