1,721,044 research outputs found
Approccio molecolare alla valutazione quantitativa e qualitativa di indicatori di inquinamento fecale dell'ambiente marino costiero
No full textGli enterococchi sono batteri gram positivi, abitanti della flora intestinale degli animali a
sangue caldo, compreso l’uomo. Essi causano un ampio range di infezioni di interesse
clinico. L’eradicazione degli enterococchi resistenti alla maggior parte degli antibiotici usati
per contrastare le infezioni causate dai suddetti superbugs oggi rappresenta una sfida in
ambito clinico. Gli enterococchi sono usati come indicatori di contaminazione fecale (FIB)
nel monitoraggio microbiologico delle acque. Questa tesi è stata focalizzata sulla
comprensione del contributo dell’ambiente marino alla presenza, diffusione ed evoluzione
di enterococchi superbugs. A raggiungere tale obbiettivo, campioni di acqua e di
sedimento sono stati raccolti da differenti siti, inclusi impianti di acquacoltura, del Mare
Adriatico, e sono stati analizzati per la presenza di enterococchi antibiotico resistenti
tramite metodiche colturali e nuovi protocolli molecolari, inoltre sono state valutate le
relazioni genetiche tra loro e con ceppi clinici tramite la ERIC PCR. In conclusione in
questa Tesi è stata evidenziata l’importanza del sedimento nel monitoraggio dei FIB, è
stato dimostrato il ruolo dell’attività dell’acquacoltura relativamente alla presenza e
diffusione di enterococchi antibiotico resistenti e il ruolo di diverse pressioni selettive
presenti in ambiente e in ambito clinico nel selezionare ceppi ambientali e clinici.Enterococci are gram positive bacteria, inhabitants of the intestinal flora of warm blood
animals, including humans. They cause a range of infections in clinical settings. The
eradication of enterococcal strains resistant to most antimicrobials used to contrast serious
gram-positives infections the so called superbugs is nowadays a clinical challenge.
Enterococci are used as Fecal Indicator Bacteria (FIB) for monitoring recreational waters
to assess the potential risks for human health. This thesis was focused on the
understanding of the contribution of the marine environment in the emergence, evolution
and spread of enterococcal “superbugs”. To reach this goal water and sediment samples
collected from different areas, including aquaculture sites, of the Adriatic Sea were
analysed for the presence of antibiotic resistant enterococci by cultural and improved
molecular methods, their genetic relationships and relatedness with clinical strains by
ERIC PCR. In conclusion in this Thesis it has been highlighted the importance of
sediment analysis when monitoring FIB, it has been demonstrated the role of the
aquaculture activity on the presence and spread of antibiotic resistant enterococci and the
role of the different selective pressures exerted in environmental and clinical setting, in the
shaping of environmental and clinical strains
Co-selection of antibiotic and heavy metal resistance in freshwater bacteria
Full text linkAntibiotic resistant bacteria are found in most environments, especially in highly anthropized waters. A direct correlation between human activities (e.g., pollution) and spread and persistence of antibiotic resistant bacteria (ARB) and resistance genes (ARGs) within the resident bacterial communities appears more and more obvious. Furthermore, the threat posed for human health by the presence of ARB and ARGs in these environments is enhanced by the risk of horizontal gene transfer of resistance genes to human pathogens. Although the knowledge on the spread of antibiotic resistances in waters is increasing, the understanding of the driving factors determining the selection for antibiotic resistance in the environment is still scarce. Antibiotic pollution is generally coupled with contamination by heavy metals (HMs) and other chemicals, which can also promote the development of resistance mechanisms, often through co-selecting for multiple resistances. The co-selection of heavy metal resistance genes and ARGs in waters, sediments, and soils, increases the complexity of the ecological role of ARGs, and reduces the effectiveness of control actions. In this mini-review we present the state-of-the-art of the research on antibiotic- and HM-resistance and their connection in the environment, with a focus on HM pollution and aquatic environments. We review the spread and the persistence of HMs and/or ARB, and how it influences their respective gene co-selection. In the last chapter, we propose Lake Orta, a system characterized by an intensive HM pollution followed by a successful restoration of the chemistry of the water column, as a study-site to evaluate the spread and selection of HMs and antibiotic resistances in heavily disturbed environments
Rainfall increases the abundance of antibiotic resistance genes within a riverine microbial community
No full textInfections with antibiotic resistant bacteria are among the major threats for human health. Studies elucidating the role of the environment in their spread are still in their infancy, it, however, seems that different environments might function as a long-term reservoir of antibiotic resistance genes (ARGs) that reside within their microbial communities. An increasing number of studies target the presence and the persistence of ARGs in waters and soils that are exposed to human activities; they, however, rarely consider the spatial/temporal variability that predominate in these environments. Here we evaluated the effect of a moderate rain event (4 mm rain hâ1) on the abundance and distribution of ARGs (tetA, ermB, blaCTXM, sulII, and qnrS), by comparing measurements of gene abundances during the rainfall to the yearly average, in the waters of a large subalpine river. ARG abundances, which all increased during the rain event, were then correlated to several microbiological, physical and chemical variables, in order to establish their potential origin. Increments in ARG abundances during rainfall (total ARGs: 24 fold) was concomitant to an increase in total phosphorous, N-NH4, and microbial aggregates. Our results show a strong influence of a moderate rainfall on the abundances of ARGs, and suggest the catchment as their source. The impact of moderate rainfalls in areas exposed to anthropic activities should then be considered in modelling and management of ARG dynamics
Impact of industrial wastewater on the dynamics of antibiotic resistance genes in a full-scale urban wastewater treatment plant
No full textUrban Wastewater Treatment Plants (UWTPs) treating mixed urban sewage and industrial wastewater are among the major hotspots for the spread of Antibiotic Resistance Genes (ARGs) into the environment. This study addresses the impact of the wastewater origin on ARG dynamics in a full-scale UWTP (15,000 Population Equivalent, PE) by operating the plant with and without industrial wastewater. Composite samples (4 L) from different treatment points were characterized for their chemical composition, bacterial abundance and for the abundance of four resistance genes against tetracycline, sulfonamides, erythromycin, and quinolones (tetA, sul2, ermB, and qnrS), and of the class 1 integrons (intI1). Although the chemical composition of the outflow significantly differed when the plant operated with or without industrial wastewater, the system efficiency in the removal of bacterial cells, ARGs, and intI1 was constant. The final disinfection by peracetic acid (PAA) did not affect the removal of ARGs, independently of the wastewater origin and the chemical characteristics of the inflows. Our results demonstrated that a well-functioning small size UWTP could treat a significant amount of industrial wastewater mixed in the urban sewage without affecting the overall ARGs and class 1 integrons released into the environment
Data from: Constitutive presence of antibiotic resistance genes within the bacterial community of a large subalpine lake
No full textThe fate of antibiotic resistance genes (ARGs) in environmental microbial communities is of primary concern as prodromal of a potential transfer to pathogenic bacteria. Although of diverse origin, the persistence of ARGs in aquatic environments is highly influenced by anthropic activities, allowing potential control actions in well-studied environments. However, knowledge of abundance and space–time distribution of ARGs in ecosystems is still scarce. Using quantitative real-time PCR, we investigated the presence and the abundance of twelve ARGs (against tetracyclines, β-lactams, aminoglycosides, quinolones and sulphonamides) at different sampling sites, depths and seasons, in Lake Maggiore, a large subalpine lake, and in the area of its watershed. We then evaluated the correlation between each ARG and a number of ecological parameters in the water column in the deepest part of the lake. Our results suggest the constitutive presence of at least four ARGs within the bacterial community with a high proportion of bacteria potentially resistant to tetracyclines and sulphonamides. The presence of these ARGs was independent of the total bacterial density and temperature. The dynamics of tet(A) and sulII genes were, however, positively correlated with dissolved oxygen and negatively to chlorophyll a, suggesting that the resistant microbes inhabit specific niches. These observations indicate that the lake is a reservoir of antibiotic resistances, highlighting the need of a deeper understanding of the sources of ARGs and the factors allowing their persistence in waters
The marine environment as a reservoir of enterococci carrying resistance and virulence genes strongly associated with clinical strains
No full textTo gain insights into the relationships and the genetic exchange among environmental and clinical enterococci, 59 strains (29 from marine aquaculture sites and 30 from clinical settings) resistant to tetracycline, erythromycin, ampicillin and/or gentamicin were analysed for the antibiotic resistance tet(M), tet(L), tet(O), erm(A), erm(B), mef blaZ, aac(6â2)-Ie aph(2â3)-Ia and virulence gelE, cylB, efaA and esp genes, and for the copper resistance gene tcrB. Antibiotic resistance and virulence genes were detected more frequently in clinical than in environmental enterococci; the opposite was true for copper resistance. Conjugation experiments demonstrated the transfer of antibiotic resistance genes from marine to clinical enterococci in interspecific mating and the uncommon joint transfer of tet(L) and erm(B). Enterobacterial repetitive intergenic consensus polymerase chain reaction typing evidenced a cluster (90% similarity) encompassing strains carrying multiple antibiotic resistance genes from both sets; the others marine isolates exhibited polyclonality and bore tcrB. Our results demonstrate that antibiotic-resistant marine enterococci bear antibiotic resistance genes transferable to humans and suggest that copper resistance, not observed among clinical strains, may be useful for survival in the environment, whereas virulence genes likely confer no advantage to enterococcal populations adapted to a lifestyle outside the host. © 2013 Society for Applied Microbiology and John Wiley & Sons Ltd
Daphnia as a refuge for an antibiotic resistance gene in an experimental freshwater community
No full text<p>Mechanisms that enable the maintenance of antibiotic resistance genes in the environment are still greatly unknown.<br>
Here we show that the tetracycline resistance gene tet(A) is largely removed from the pelagic aquatic<br>
bacterial community through filter feeding by Daphnia obtusa while it becomes detectable within the<br>
microbiome of the daphniids themselves, where it was not present prior to the experiment. We moreover<br>
show that a multitude of Daphnia-associated bacterial taxa are potential carriers of tet(A) and postulated that<br>
the biofilm-like structures,where bacteria growin,may enable horizontal transfer of such genes. This experiment<br>
highlights the need to take ecological interactions and a broad range of niches into consideration when studying<br>
and discussing the fate of antibiotic resistance genes in nature.</p>
Co-treatment of landfill leachate with urban wastewater by chemical, physical and biological processes: Fenton oxidation preserves autochthonous bacterial community in the activated sludge process
No full textThe impact of Fenton oxidation (FO) and Air stripping (AS) pre-treatments on the bacterial community of a biological activated sludge (B-AS) process for the co-treatment of mature landfill leachate (MLL) and urban wastewater (UWW) was assessed. In this work high-throughput sequencing was used to identify changes in the composition of the bacterial communities when exposed to different landfill leachate's pre-treatments. The combination of FO and AS to increase biodegradability (BOD5/COD) and reduce ammonia concentration (NH3) respectively, allowed to successfully operate the B-AS and effectively treat MLL. In particular, BOD5/COD resulted to be the key factor for bacterial community shifting. The microbiological community of the B-AS, mainly composed by the phylum Bacteroidota (Saprospiraceae, PHOS-HE51, Chitinophagaceae) after FO pre-treatment, shifted to Pseudomonadota (Caulobacteraceae and Hyphomicrobiaceae) when FO was not used. At the same time a drastic reduction in BOD5 removal was observed (90%-58%). On the other hand, high NH3 concentration affected the abundance of the family Saprospiraceae, known to play a key role in the degradation of complex organic compounds in B-AS. The results obtained suggest that a suitable combination of pre-treatments can reduce the negative effect of MLL on the B-AS process, reducing the pressure on autochthonous bacteria and therefore the acclimatization time of the biological process
Antibiotic-Resistant Enterococci in Seawater and Sediments from a Coastal Fish Farm
No full textThe aim of this study was to detect and characterize antibiotic-resistant enterococci in seawater and sediment
from a Mediterranean aquaculture site where no antibiotics are used. Colonies (650) grown on Slanetz-Bartley
(SB) agar were amplified on antibiotic-supplemented SB, and erythromycin (ERY), tetracycline (TET), and
ampicillin (AMP) MICs were determined. Of 75 resistant isolates (17 to TET, 5 to ERY, and 45 to AMP), 5
Enterococcus faecalis, 25 E. faecium, 5 E. casseliflavus, 1 E. gallinarum, 1 E. durans, and 23 Enterococcus spp. were
identified by genus- and species-specific polymerase chain reaction (PCR). tet(M), tet(O), tet(L), tet(K), erm(B),
erm(A), erm(C), mef, msr, blaZ, and int(Tn916) were sought by PCR, including an improved multiplex PCR assay
targeting tet(M), tet(L), and erm(B). Tet(M) was the most frequent TET resistance gene; msr(C) was the sole ERY
resistance gene detected. blaZ was found in 29/45 AMP-resistant isolates; however, no b-lactamase production
was detected. Antibiotic-resistant enterococci were recovered 2km off the coast despite the absence of selective
pressure exerted by antibiotic use. The occurrence of resistant strains in the absence of the tested genes may
indicate the presence of less common resistance determinants. This first evidence of resistant enterococci at a
Mediterranean aquaculture site suggests the existence of a marine reservoir of antibiotic resistances potentially
transmissible to virulent strains that could be affected by mariculture in an antibiotic-independent manner
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