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Vet Microbiol. 2014 Aug 6;172(1-2):265-71. doi: 10.1016/j.vetmic.2014.04.013. Epub 2014 Apr 30.

Increasing of temperature induces pathogenicity of Streptococcus agalactiae and the up-regulation of inflammatory related genes in infected Nile tilapia (Oreochromis niloticus).

Author information

1
Department of Veterinary Microbiology, Faculty of Veterinary Science, Chulalongkorn University, Bangkok 10330, Thailand.
2
Department of Veterinary Pathology, Faculty of Veterinary Science Chulalongkorn University, Bangkok 10330, Thailand.
3
Laboratory of Genome Science, Tokyo University of Marine Science and Technology, Tokyo 108-8477, Japan.
4
Department of Veterinary Microbiology, Faculty of Veterinary Science, Chulalongkorn University, Bangkok 10330, Thailand. Electronic address: Channarong.R@chula.ac.th.

Abstract

Temperature strongly affects the health of aquatic poikilotherms. In Nile tilapia (Oreochromis niloticus), elevated water temperatures increase the severity of streptococcosis. Here we investigated the effects of temperature on the vulnerability and inflammatory response of Nile tilapia to Streptococcus agalactiae (Group B streptococci; GBS). At 35 and 28 °C, GBS took 4 and 7h, respectively to reach the log-phase and, when incubated with tilapia whole blood, experienced survival rates of 97% and 2%, respectively. The hemolysis activity of GBS grown at 35 °C was five times higher than that of GBS grown at 28 °C. GBS expressed cylE (β-hemolysin/cytolysin), cfb (CAMP factor) and PI-2b (pili-backbone) much more strongly at 35 °C than at 28 °C. Challenging Nile tilapia reared at 35 and 28 °C with GBS resulted in accumulated mortalities of about 85% and 45%, respectively. At 35 °C, infected tilapia exhibited tremendous inflammatory responses due to a dramatic up-regulation (30-40-fold) of inflammatory-related genes (cyclooxygenase-2, IL-1β and TNF-α) between 6 and 96 h-post infection. These results suggest that the increase of GBS pathogenicity to Nile tilapia induced by elevated temperature is associated with massive inflammatory responses, which may lead to acute mortality.

KEYWORDS:

Gene expression; Inflammation; Streptococcus agalactiae; Temperature; Tilapia; Virulence

PMID:
24856132
DOI:
10.1016/j.vetmic.2014.04.013
[Indexed for MEDLINE]

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