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Genetic and pathogenic difference between Streptococcus agalactiae serotype Ia fish and human isolates.
Chishih Chu1, Pei-Yu Huang2, Hung-Ming Chen3
1Department of Microbiology, Immunology, and Biopharmaceutics, National Chiayi University, Chiayi, 60004, Taiwan, ROC.
BMC Microbiology
|August 4, 2016
Summary
Fish and human Streptococcus agalactiae (GBS) isolates show distinct genetic and pathogenic traits. Fish GBS strains, particularly pulsotype Ia, exhibit higher virulence and may serve as effective vaccine candidates for preventing fish infections.
Area of Science:
- Microbiology
- Veterinary Medicine
- Genetics
Background:
- Streptococcus agalactiae (GBS) is a significant pathogen affecting humans and fish.
- This study investigated GBS isolates from both sources between 2007-2012.
Purpose of the Study:
- To compare serotypes, antibiotic susceptibility, genetic profiles, and pathogenicity of human and fish GBS isolates.
- To explore potential vaccine strains for fish GBS infections.
Main Methods:
- Polymerase chain reaction (PCR) serotyping was employed.
- Antibiotic susceptibility testing was conducted.
- Pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) were used for genetic analysis.
- Pathogenicity was assessed in tilapia models.
Main Results:
- All fish GBS isolates were serotype Ia, distinct from the majority of human isolates.
- Fish GBS isolates possessed unique genetic profiles (ST7, specific pulsotypes) and plasmids, differing from human isolates (ST23, ST483).
- Fish GBS isolates exhibited increased resistance to certain antibiotics over time and demonstrated significantly higher pathogenicity and mortality in tilapia compared to human isolates.
Conclusions:
- Human and fish serotype Ia GBS isolates have diverse genetic origins and pathogenic potentials.
- Fish GBS pulsotype Ia strains show promise as vaccine candidates for controlling GBS infections in fish.
