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- Collin, Betty, 1976-
(author)
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Characterization and persistence of potential human pathogenic vibrios in aquatic environments
- 2012
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Doctoral thesis (other academic/artistic)abstract
- Vibrio spp., natural inhabitants of aquatic environments, are one of the most common causes of bacterial gastroenteritis in the world, being spread to humans via the ingestion of seafood, contaminated drinking water or exposure to seawater. The majority of Vibrio spp. are avirulent, but certain strains may sporadically be human pathogenic. Vibrio cholerae may cause cholera and fatal wound infections, Vibrio parahaemolyticus may cause gastroenteritis and Vibrio vulnificus may cause wound infections and sepsis. To expand current knowledge of the occurrence, ecological niche and persistence of potential human pathogenic Vibrio spp. in aquatic environments, occurrence and laboratory studies were performed. The seasonal variation of Vibrio spp. in clams and mussels from Mozambique and Sweden were studied, with isolated strains characterized and compared with those isolated from water samples collected in India. Results showed that the numbers of Vibrio spp. in Mozambican clams peaked during the warmer rainy season and that the dominating species was V. parahaemolyticus. Biochemical fingerprinting and virulence screened by PCR revealed a high similarity among strains from the different aquatic environments. However, isolate functional hemolytic analyses and antibiotic resistance patterns differed between strains; Swedish and Indian strains were less sensitive to the tested antibiotics and had a lower hemolytic capacity than those from Mozambique. Molecular analysis of bacterial DNA from Swedish mussels showed the presence of the three Vibrio spp. most commonly linked with human illness, as well as their associated virulence genes. The strains isolated from marine and clinical environments were equally and highly harmful to the tested eukaryotic cells. The persistence of clinical V. cholerae in aquatic environments was investigated in vivo. Strains were exposed to mussels, with bacterial uptake and elimination then examined. The mussels were able to avoid the most potent strain by complete closure of shells. The less potent strain was accumulated in mussel tissue in low levels and one marine control strain to a higher degree. Mussels eliminated the pathogenic strain less efficiently than they did the marine strain. One clinical and one marine strain were then exposed to 4°C for 21 days, with the temperature then increased to 20°C. The clinical strain was more prone to lose culturability than the marine strain at 4°C, the former performed significantly better in regaining culturability after the temperature up-shift. Subsequently, the persistence of the clinical strain in natural bottom sediment, incubating as above, was studied and results showed a similar decrease in culturable numbers in the sediment as in the water. As the clinical V. cholerae strains did not carry any of the standard set of virulence genes, the ability to change from non-culturable to culturable may be of great importance to strain pathogenicity. The results also show that natural bottom sediment may be a potential reservoir of human pathogenic Vibrio spp.
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| 2. |
- Kaur-Kahlon, G., et al.
(author)
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Response of a coastal tropical pelagic microbial community to changed salinity and temperature
- 2016
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In: Aquatic Microbial Ecology. - 0948-3055 .- 1616-1564. ; 77:1, s. 37-50
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Journal article (peer-reviewed)abstract
- Studies on the responses of tropical microbial communities to changing hydrographic conditions are presently poorly represented. We present here the results from a mesocosm experiment conducted in southwest (SW) coastal India to investigate how changes in temperature and salinity may affect a coastal tropic microbial community. The onset of algal and bacterial blooms, the maximum production and biomass, and the interrelation between phytoplankton and bacteria were studied in replicated mesocosms. The treatments were set up featuring ambient conditions (28 °C, 35 PSU), hyposalinity (31 PSU), warming (31 °C) and a double manipulated treatment with warming and hyposalinity (31 °C, 31 PSU). The hyposaline treatment had the most considerable influence manifested as significantly lower primary production, and the most dissimilar microphytoplankton species community. The increased temperature acted as a catalyst in the double manipulated treatment and higher primary production was maintained. We investigated the dynamics of the microbial community with a structural equation model approach, and found a significant interrelation between phytoplankton biomass and bacterial abundance. Using this methodology, it became evident that temperature and salinity changes, individually and together, mediate direct and indirect effects that influence different compartments of the microbial loop. In the face of climate change, we suggest that in relatively nutrient replete tropical coastal zones, salinity and temperature changes will affect nutrient assimilation with subsequent significant effects on the quantity of microbial biomass and production.
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