High prevalence of virulence genes and in-vitro biofilm production in clinical multidrug resistant Escherichia coli in Dakar Senegal

Abstract

Background Bacterial virulence is a key factor determining the outcome of each bacterial infection and virulent bacteria are often associated to high-risk infections. Extraintestinal pathogenic Escherichia coli (ExPEC) is the most implicated bacterium in human bacterial infections and its virulence factors are classified into five categories: adhesins, toxins, iron capture systems, protectins and invasins. Furthermore, bacterial biofilms are the main cause of hospital-acquired infections like urinary catheter-associated infections, valve endocarditis, Otitis and cystic fibrosis.Results For the sixteen virulence genes sought by standard polymerase chain reaction (PCR), all the 78 ExPECs isolates carried at least four virulence genes. Following prevalences of virulence genes were reported: adhesins genes fimH (98.7%), mrkD (98.7%), papC (46.2%), afaC (9%), sfa / focDE (1.3%); iron acquisition systems genes entB (98.7%), fepA (98.7%), ybtS (93.6%), fyuA (91%), iucA (91%), iucB (91%), iutA (34.6), iroB (6.4%), iroN (6.4%) and toxins genes hlyA (10.3%), cnf (1 & 2) (10.3%). Seventy-five out of 78 isolates (96.2%) carried at least the combination of two adhesins genes and two iron capture systems genes whereas 8 out of 78 (10.3%) harbored the combination of (adhesins genes + iron acquisition systems genes + toxins genes). Among the 78 strains studied, one hospital-acquired strain isolated from urine harbored 15 virulence genes out of 16 sought. The evaluation of biofilm-formation capacity revealed that all (29/29) hospital-acquired isolates were biofilm producers with (6/29; 20.7%) strong biofilm producers, (15/29; 51.7%) moderate biofilm producers and (8/29; 27.6%) weak biofilm producers. Isolates carrying papC had greater biofilm formation capacity than those not carrying papC (p < 0.001).Conclusions Most of our strains had moderate biofilm-formation capacity and carried an average of 9 virulence genes out of 16 sought. These eight strains carrying a combination of genes (adhesins + iron acquisition systems genes + toxins genes) may be hypervirulent isolates. Additional studies may confirm this. The deepening of this kind of study on bacterial virulence and hospital bacterial biofilms could lead to the improvement of infections investigation, prevention and therapeutic protocols.

Biofilm Formation by Escherichia coli Isolated from Urinary Tract Infections from Aguascalientes, Mexico

“…The presence of virulence factors (genes) with the ability of UPEC to form biofilms in vitro has been reported [27,28,30,35,69,73]; nevertheless, the quantitative correlation between biofilm and virulence factors has yielded different results. In agreement with previous studies [21,29,30,69,74,76,[80][81][82], strong biofilm-producing strains presented a higher prevalence of fimH and papC genes. Indeed, fimH, the gene coding for the α-Dmannose-specific tip adhesin of type 1 fimbriae, was present in almost all the strains, denoting their important role in adhesion and biofilm formation in UPEC.…”

“…Other studies have reported a prevalence of 78% [71], 80% [31,72], and 84.3% [73]. Most strains were able to form moderate biofilms, which is consistent with previous work [21,29,30,73]. Several studies have shown a lower frequency of moderate biofilm-forming strains and a higher prevalence of weak biofilm-producing strains [18,73,74].…”

“…Additionally, UPEC can form quiescent intracellular reservoirs (QIRs) that reside in the underlying urothelium and can trigger reactivation by the exfoliation of superficial epithelial cells, realizing bacteria back into the bladder and acting as a source of recurrent UTIs [7,8,19,20]. These microbial communities are difficult to eradicate because they are poorly responsive to conventional antimicrobial treatment and are more resistant to the host immune response [21,22]. In addition, it has been demonstrated that UPEC biofilms can persist despite treatment with multiple antibiotics [8,20,23,24].…”

“…Several virulence factors have been associated with UPEC strong biofilm-producing strains, including type 1 fimbriae [26][27][28], papC [29][30][31], papG alleles, sfa/focDE, focG, sfa [28,29,32,33], cnf1 [27,34], agn43 [2,6,35], afa, fimH [29,31,36], traT [36], hemolysin presence [21,37], sdiA, rcsA, and rpoS genes [38]. Moreover, the relationship between antimicrobial resistance and biofilm-producing on E. coli has been studied [21,[37][38][39][40]. However, an inconsistent conclusion was found.…”