Genetic and Virulence Potential Relationship of Escherichia Coli Isolates from Children of Quilombola Communities
Name: CAROLINE GASTALDI GUERRIERI TRÉS
Publication date: 22/02/2018
Advisor:
Name |
Role |
|---|---|
| LILIANA CRUZ SPANO | Advisor * |
Examining board:
| Name |
Role |
|---|---|
| ANA PAULA FERREIRA NUNES | Internal Examiner * |
| LILIANA CRUZ SPANO | Advisor * |
Summary: Enteroaggregative Escherichia coli (EAEC) is an emerging pathotype responsible for acute and persistent diarrhea. It is characterized by high heterogeneity of the potential virulence factors among the isolates. EAEC can be classified as typical (tEAEC) and atypical (aEAEC) based on the presence of the AggR regulon, suggesting a higher virulence for tEAEC, although the aEAEC is related to outbreaks of diarrhea. We aimed to determine the genetic relationship and in vivo virulence potential of tEAEC and aEAEC isolates from children of quilombola communities. To analyze the clonal diversity, we used the electrophoresis pulsed field gel electrophoresis (PFGE) after digestion with XbaI restriction enzyme in 73 strains previously characterized according to the repertoire of virulence genes. The virulence of 20 EAEC strains (10 tEAEC and 10 aEAEC) in addition to reference strains of tEAEC (EAEC 042), aEAEC (C1096) and non-pathogenic E. coli HB101 was investigated with Galleria mellonella model. The survival of the larvae was analyzed after inoculation of 104 to 107 CFU/larvae and the bacterial load in the hemolymph
was determined after inoculation of 105 CFU/larvae of the reference strains, at
different periods after infection. In addition, we evaluated phenotypic characteristics of virulence of 10 EAEC isolates (enzyme, siderophores and biofilm production). For epidemiological analysis at the global level, 10 isolates were submitted to molecular typing using the Multilocus Sequence Typing (MLST). We observed 58 distinct pulsotypes, with no relationship between the virulence gene profile and the community of origin, for most of the strains. Concerning G. mellonella model, we observe: (i) mortality of the larvae was dependent on the inoculated concentration of tEAEC and aEAEC; (ii) strains of aEAEC were as virulent as those of tEAEC, but the mean virulence was higher for tEAEC; (iii) There was no relationship between the number of virulence genes and the in vivo virulence; (iv) in contrast to EAEC 042 and
EAEC C1096, E. coli HB101 does not cause melanization and is eliminated from the
haemolymph at 2 hours post infection. Regarding the phenotypic characteristics of
virulence: (i) no strain produced phospholipase, protease or esterase; (ii) only one strain produced haemolysin; (iii) all analyzed strains produced siderophores; (iv) only one strain did not produce biofilm. The 10 isolates analyzed by MLST belong to distinct STs and, therefore, represent different evolutionary lineages. The STs: 443, 730, 1178, 1286 and 2481, detected in our strains, had not been described for EAEC to date. In conclusion, the results obtained demonstrate a high heterogeneity of EAEC from quilombola communities, even though they are semi-isolated, since most of the strains had no genotypic relationship between them. In addition, new STs were
observed in EAEC strains and, in contrast to what is suggested in the literature, in the model of the study, aEAEC may be as virulent as tEAEC.
