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Publications

Publications by Sónia Dias

2022

Descriptive Statistics based on Frequency Distribution

Authors
Dias, S; Brito, P;

Publication
Analysis of Distributional Data

Abstract

2022

Fundamental Concepts about Distributional Data

Authors
Dias, S; Brito, P;

Publication
Analysis of Distributional Data

Abstract

2007

Coccoid form of Helicobacter pylori as a morphological manifestation of cell adaptation to the environment

Authors
Azevedo, NF; Almeida, C; Cerqueira, L; Dias, S; Keevil, CW; Vieira, MJ;

Publication
APPLIED AND ENVIRONMENTAL MICROBIOLOGY

Abstract
After characterization of preferred conditions for Helicobacter pylori survival in the sessile state, it was observed that the bacterium transforms from spiral to coccoid under mild circumstances, whereas under extreme ones it is unable to undergo shape modification. This strongly supports the view that transformation into the coccoid form is an active, biologically led process, switched on by the bacterium as a protection mechanism.

2008

Survival of gastric and enterohepatic Helicobacter spp. in water: Implications for transmission

Authors
Azevedo, NF; Almeida, C; Fernandes, I; Cerqueira, L; Dias, S; Keevil, CW; Vieira, MJ;

Publication
APPLIED AND ENVIRONMENTAL MICROBIOLOGY

Abstract
Part of the reason for rejecting aquatic environments as possible vectors for the transmission of Helicobacter pylori has been the preference of this microorganism to inhabit the human stomach and hence use a direct oral-oral route for transmission. On the other hand, most enteric bacterial pathogens are well known for being able to use water as an environmental reservoir. In this work, we have exposed 13 strains of seven different Helicobacter spp. (both gastric and enterohepatic) to water and tracked their survival by standard plating methods and membrane integrity assessment. The influence of different plating media and temperatures and the presence of light on recovery was also assessed. There was good correlation between cultivability and membrane integrity results (Pearson's correlation coefficient = 0.916), confirming that the culture method could reliably estimate differences in survival among different Helicobacter spp. The species that survived the longest in water was H. pylori (> 96 It in the dark at 25 degrees C), whereas H. felis appeared to be the most sensitive to water (<6 h). A hierarchical cluster analysis demonstrated that there was no relationship between the enterohepatic nature of Helicobacter spp. and an increased time of survival in water. This work assesses for the first time the survival of multiple Helicobacter spp., such has H. mustelae, H. muridarum, H. felis, H. canadensis, H. pullorum, and H. canis, in water under several conditions and concludes that the roles of water in transmission between hosts are likely to be similar for all these species, whether enterohepatic or not.

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