Molecular Epidemiology and Virulence Gene Expression of Enterococcus spp. isolated from clinical samples in Southern Brazi

Date: 3 August 2018

Venue: Federal University of Health Sciences of Porto Alegre - R. Sarmento Leite 245 - 90050-170 Centro Histórico, Porto Alegre - RS

PhD candidate: Renata Oliveira Soares

Principal investigator: Paul Cos - Guy Caljon

Short description: Doctoral Defence Renata Oliveira Soares - Department of Pharmaceutical Sciences


Molecular Epidemiology and Virulence Gene Expression of Enterococcus spp. isolated from clinical samples in Southern Brazil


Joint PhD Student: Renata Oliveira Soares

Supervisors: Prof. dr. P. Cos, Prof. dr. G. Caljon, Prof. dr. P.A. d’Azevedo

Co-supervisor: Prof. dr. J. Caierão



Enterococcus faecalis and Enterococcus faecium are opportunistic pathogens, able to cause different types of infections, from ordinary urinary tract infections to life-threatening healthcare-associated ones. This capacity is directly associated with their ability to form biofilm and the presence of many virulence factors and resistance genes, giving them selective advantages in adverse conditions. Vancomycin-Resistant Enterococci (VRE) has become increasingly common in some settings around the world and their rapid and accurate identification, as well as the understanding of their clonal spread, can improve treatment and infection control policies. In this study, we evaluated the performance of a selective chromogenic medium (chromID™ VRE agar) using 184 clinical isolates of Enterococcus spp. (susceptible and resistant to vancomycin) and reference strains. Secondly, we characterized the susceptibility profile and clonal relationships of 115 VRE, recovered from inpatients attended at three general Hospitals of Porto Alegre, Brazil. Thirdly, we evaluated the ability to form biofilm of 123 E. faecalis clinical isolates in the presence and absence of 1% D-(+)-glucose and the expression of four biofilm-related genes (ebpA, efaA, ace and gelE) in eleven clinical isolates and E. faecalis ATCC 29212 by qPCR. Lastly, we evaluated the E. faecalis V583 biofilm formation capability in the absence and presence of human serum (1%, 5%, 25% and 50%) and the expression of five virulence genes ebpA, efaA, ace, gelE and asa in planktonic and sessile cells by qPCR. Although ChromID™ VRE agar had a very good sensitivity (95.52%), it presented a worrisome low specificity (30%). All VRE were identified as E. faecium and exhibited high-level resistance to vancomycin, resistance to teicoplanin, ampicillin, ciprofloxacin and 13.9% of them were resistant to high level of gentamicin. All VRE harbored vanA gene, 86.1% esp gene and 95.7% acm gene. PFGE profile analysis revealed a polyclonal distribution with 23 clonal types encompassing 79 isolates, while 15 isolates exhibited unique patterns and 21 were non-typable. Considering biofilm formation, 1% glucose supplementation increased significantly the biofilm formation among E. faecalis. However, gene expression varied among them, showing that patterns of virulence gene expression may be dependent partially on the bacterial genetic background, rather than exclusively environmental conditions. On the other hand, it was observed an inhibition of the adhesion in the presence of 5% human serum compared to the control group. Planktonic cells of E. faecalis V583 exhibited upregulation of asa gene in 5%, 25% and 50% of human serum, while in the sessile cells, efaA, gelE, ace and asa genes were significantly upregulated in high concentrations of human serum (25% and 50%). A better understanding of this process as well as the application of these findings in vivo may help in the search for strategies to control the biofilm formation by this microorganism.