| Summary: |
Bacteria are known for their ubiquity and plasticity. Antibiotic resistant bacteria and resistance encoding genes have a widespread distribution, being detected in food products, drinking water, domestic environment, pets and healthy humans. Water, the most important bacterial habitat, represents the major vector of such dissemination. This study is designed to estimate and characterize the levels of antibiotic resistance along tap water circuit - from the source to the tap. Water samples will be collected in the water source, after water treatment and disinfection, in different sites of the distribution system, and from the taps of buildings with different levels of tap water usage, such as hotels, health care units or homes. The bacterial diversity along the water circuit will be characterized through PCR-DGGE using universal or family specific primers. The sequencing of the most intense/representative bands will give an idea about the groups more abundant at the different parts of the water circuit. Bacteria belonging to different taxonomic groups will be selectively cultured on media with specific elective properties. Groups of great relevance in terms of water colonization and of antibiotic resistance, for example, enterobacteria (e.g. Enterobacter, Shigella, Klebsiella), non-fermenting Gram-negative bacteria (e.g. Acinetobacter, Burkholderia, Pseudomonas, Aeromonas) and Staphylococcus will be the major focus of the project. Nevertheless, other organisms as Campylobacter spp., Legionella spp. or environmental mycobacteria observed to be prevalent in these samples will be also cultivated and analysed. About 1000-2000 isolates obtained throughout the water circuit, from the source to the tap, will be characterized for their taxonomy and antibiotic resistance patterns. The genetic determinants responsible for the antibiotic resistance phenotypes observed in selected bacterial isolates will be sequenced and identified. This procedure will permit the tracki  |
Summary
Bacteria are known for their ubiquity and plasticity. Antibiotic resistant bacteria and resistance encoding genes have a widespread distribution, being detected in food products, drinking water, domestic environment, pets and healthy humans. Water, the most important bacterial habitat, represents the major vector of such dissemination. This study is designed to estimate and characterize the levels of antibiotic resistance along tap water circuit - from the source to the tap. Water samples will be collected in the water source, after water treatment and disinfection, in different sites of the distribution system, and from the taps of buildings with different levels of tap water usage, such as hotels, health care units or homes. The bacterial diversity along the water circuit will be characterized through PCR-DGGE using universal or family specific primers. The sequencing of the most intense/representative bands will give an idea about the groups more abundant at the different parts of the water circuit. Bacteria belonging to different taxonomic groups will be selectively cultured on media with specific elective properties. Groups of great relevance in terms of water colonization and of antibiotic resistance, for example, enterobacteria (e.g. Enterobacter, Shigella, Klebsiella), non-fermenting Gram-negative bacteria (e.g. Acinetobacter, Burkholderia, Pseudomonas, Aeromonas) and Staphylococcus will be the major focus of the project. Nevertheless, other organisms as Campylobacter spp., Legionella spp. or environmental mycobacteria observed to be prevalent in these samples will be also cultivated and analysed. About 1000-2000 isolates obtained throughout the water circuit, from the source to the tap, will be characterized for their taxonomy and antibiotic resistance patterns. The genetic determinants responsible for the antibiotic resistance phenotypes observed in selected bacterial isolates will be sequenced and identified. This procedure will permit the tracking of the genetic determinants throughout the water circuit. Moreover, it will constitute the basis for the development of a method for the detection of antibiotic resistance determinants among the bacterial populations that are non-culturable and difficult to isolate, as those trapped in biofilm structures. In an attempt to identify major routes and modes of the spreading and persistence of antibiotic resistant bacteria along the water circuit, indications of clonal selection will be inferred in the culturable bacterial populations. Bacteria belonging to a same taxon, associated with a specific antibiotic resistance phenotype, and detected along the water circuit (from the source to the tap) will constitute the basis for a further investigation about the modes and routes of antibiotic resistance dissemination. The relatedness of antibiotic resistant isolates recovered along the water circuit, belonging to the same species and exhibiting similar genotypes, will be determined through multi-locus sequence typing (MLST).
This project aims at bringing some additional insights into the ecology of antibiotic resistant bacteria in water used for human consumption and will be conducted with the support of two entities - Águas de Douro e Paiva, responsible for the water collection and water treatment and disinfection, and Serviços Municipalizados de Águas e Saneamento do Porto, responsible for the distribution of that water. These entities manifested their interest and availability to supply the water samples and to give the technical advises necessary to accomplish the present proposal. |