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- Association between gentamicin resistance and stress tolerance in water isolates of Ralstonia pickettii and R. mannitolilyticaPublication . Ferro, Pompeyo; Vaz-Moreira, Ivone; Manaia, Célia M.Members of the species Ralstonia pickettii and R. mannitolilytica, although ubiquitous and lacking major virulence factors, have been associated with nosocomial outbreaks. Tolerance to metals, antibiotics, and disinfectants may represent an advantage for their ubiquity and opportunistic pathogenic potential. In this study, we compared five strains that differed on the origin (hospital effluent, tap water, mineral water) and in the susceptibility to aminoglycosides, regarding their tolerance to metals and disinfection. The growth kinetics and biofilm formation capacity were tested in four R. pickettii strains and one R. mannitolilytica at sub-inhibitory concentrations of aminoglycosides or arsenite. The survival to UV radiation, chlorine, or hydrogen peroxide was also compared in aminoglycoside resistant and susceptible strains. Aminoglycoside-resistant strains presented a higher tolerance to arsenite than the susceptible ones and either aminoglycosides or arsenite was observed to stimulate the biofilm formation. Sub-inhibitory concentrations of the aminoglycoside gentamicin or arsenite significantly decreased the growth rate and yield, but only arsenite caused a significant increase of the lag phase. Hydrogen peroxide presented higher disinfection effectiveness against aminoglycoside susceptible than against resistant strains, an effect that was not observed for UV or chlorine. Although this conclusion needs validation based on a larger number of isolates, including clinical, the results suggest that aminoglycoside resistance may be associated with traits that influence Ralstonia spp. fitness in the environment.
- Betaproteobacteria are predominant in drinking water: are there reasons for concern?Publication . Ferro, Pompeyo; Vaz-Moreira, Ivone; Manaia, Célia M.Betaproteobacteria include some of the most abundant and ubiquitous bacterial genera that can be found in drinking water, including mineral water. The combination of physiology and ecology traits place some Betaproteobacteria in the list of potential, yet sometimes neglected, opportunistic pathogens that can be transmitted by water or aqueous solutions. Indeed, some drinking water Betaproteobacteria with intrinsic and sometimes acquired antibiotic resistance, harbouring virulence factors and often found in biofilm structures, can persist after water disinfection and reach the consumer. This literature review summarises and discusses the current knowledge about the occurrence and implications of Betaproteobacteria in drinking water. Although the sparse knowledge on the ecology and physiology of Betaproteobacteria thriving in tap or bottled natural mineral/spring drinking water (DW) is an evidence of this review, it is demonstrated that DW holds a high diversity of Betaproteobacteria, whose presence may not be innocuous. Frequently belonging to genera also found in humans, DW Betaproteobacteria are ubiquitous in different habitats, have the potential to resist antibiotics either due to intrinsic or acquired mechanisms, and hold different virulence factors. The combination of these factors places DW Betaproteobacteria in the list of candidates of emerging opportunistic pathogens. Improved bacterial identification of clinical isolates associated with opportunistic infections and additional genomic and physiological studies may contribute to elucidate the potential impact of these bacteria.