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Differential pathogenicity of five S treptococcus agalactiae isolates of diverse geographic origin in N ile tilapia ( O reochromis niloticus L .)
Author(s) -
Evans Joyce J,
Pasnik David J,
Klesius Phillip H
Publication year - 2015
Publication title -
aquaculture research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.646
H-Index - 89
eISSN - 1365-2109
pISSN - 1355-557X
DOI - 10.1111/are.12393
Subject(s) - nile tilapia , oreochromis , streptococcus agalactiae , biology , veterinary medicine , aquaculture , microbiology and biotechnology , fish <actinopterygii> , bacteria , fishery , streptococcus , medicine , genetics
S treptococcus agalactiae is an emerging pathogen of fish and has caused significant morbidity and mortality worldwide. The main objective of this study is to assess whether pathogenic differences exist among isolates from different geographic locations. Nile tilapia ( O reochromis niloticus L .) were administered an intraperitoneal injection of suspension containing USA , B razil, H onduras, I srael, or K uwait S . agalactiae isolates at concentrations ranging from 10 2 to 10 7 cfu mL −1 . The LD 50 values 7 days after challenge were as follows: USA (1.0 × 10 2 cfu mL −1 ), B razil (1.5 × 10 3 cfu mL −1 ), H onduras (6.8 × 10 3 cfu mL −1 ), I srael (1.0 × 10 4 cfu mL −1 ) and K uwait (7.2 × 10 5 cfu mL −1 ). Fish from all groups exhibited lethargy, anorexia, exophthalmia, corneal opacity, erratic swimming, petechiae and mortality. Opercular clearing and ascites were only found after infection with certain geographic isolates. The findings in this study indicate that S . agalactiae isolates of different geographic origin can cause significant mortalities after experimental challenge and can have different pathogenic capacities. Isolates from the A mericas ( USA , B razil and H onduras) were more pathogenic to N ile tilapia than isolates from the M iddle E ast/ A sia ( I srael and K uwait).