Summary auto-generated
This article investigates the genetic and phenotypic diversity of Vibrio parahaemolyticus isolates from clinical and environmental sources. The study analyzed 63 isolates using molecular typing methods and examined their pathogenic potential through virulence factor detection and hemolytic activity assays. Researchers identified three distinct pathogenic serovars based on O and K antigen combinations, with clinical isolates showing significantly higher virulence marker prevalence compared to environmental strains. The work characterized thermostable direct hemolysin (TDH) production patterns across isolates cultured at various temperatures (15-37°C). Genetic analysis revealed the presence of tdh genes and their expression profiles correlated with hemolytic phenotypes. Clinical isolates demonstrated stronger hemolytic activity and higher frequency of virulence-associated genes. The findings suggest that specific serovar combinations and genetic markers can distinguish potentially pathogenic V. parahaemolyticus strains from environmental populations, with temperature playing a modulating role in virulence expression. This has implications for understanding transmission routes and infection risk from seafood and other environmental sources.
Key findings
- Three distinct pathogenic serovars of V. parahaemolyticus were identified; clinical isolates belonged primarily to specific serotypes while environmental isolates showed greater diversity
- Clinical isolates produced significantly more thermostable direct hemolysin (TDH) and showed higher prevalence of tdh genes compared to environmental strains
- Temperature conditions (15-37°C) modulated TDH production and hemolytic activity, with optimal expression occurring at 37°C
- Genetic markers including tdh genes correlated strongly with hemolytic phenotype and virulence potential in clinical isolates
- Environmental V. parahaemolyticus strains generally exhibited lower virulence factor expression and reduced pathogenic potential compared to clinical isolates
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Abstract
A rapid method to detect extracellular proteolytic activity around colonies of Cryptococcus neoformans was developed with tannic acid used to complex with residual protein in a solid medium. A survey was conducted with 32 isolates of C. neoformans var. gattii and 31 isolates of C. neoformans var. neoformans which were cultured on medium containing gelatin as the sole nitrogen source. The annulus of clearing around fungal colonies was >1.25mumm in 24 (77%) isolates of C. neoformans var. neoformans compared with only 7 (22%) isolates of C. neoformans var. gattii. There was no difference in proteolytic activity between environmental and human clinical isolates of C. neoformans. However, there was a difference between the size of the annulus around animal isolates of C. neoformans var. neoformans and isolates of the same variety from other sources. The annuli around the 14 animal isolates were all >1.25mumm, while 7 (70%) of 10 human clinical isolates and only 3 (43%) of 7 environmental isolates were scored in the high proteinase range. A difference between the genetic types (as characterised by RAPD typing) of C. neoformans var. gattii was also evident with 17 (77%) of 22 VG-I isolates having a small annulus compared with only 1 (17%) of 6 VG-II and VG-III isolates with annuli of similar size. Relatively low proteinase production by C. neoformans var. gattii may reduce local and systemic spread of infection in mammalian hosts.