Abstract
Previously, we constructed and characterized the vaccine efficacy of attenuated S. agalactiae strain YM001 in tilapia. In this study, the potential impacts of YM001 on the tilapia intestinal microbiota were assessed by qPCR and 16S rRNA sequencing methods. The results showed that YM001 distributed unevenly in different parts of intestine, peaked in the intestine at 12 h after oral administration, and then declined gradually. YM001 caused 0% mortality of fish during the entire experimental period, while the referent strain HN016 caused 100% mortality at 3 d after oral administration. However, the intestinal microbiota could be changed by YM001, the diversity of intestinal microbiota decreased first and gradually recovered after oral administration. The diversity of intestinal microbiota of tilapia was negatively correlated with the content of HN016 in the intestinal tract. The oral YM001 mainly changed the abundance of Streptococcus, Cetobacterium, Akkermansia, Romboutsia, Bacteroides, Brevinema, Lachnospiraceae_NK4A136-group, coprothermobactter, presiomonas, and Roseburia in intestine. The present study indicate that oral administration of YM001 altered the diversity and composition of intestinal microbiota in tilapia, but these change were only temporary, non-lethal, and recoverable. The results provide a more comprehensive experimental basis for the safety of oral YM001 vaccines.
Highlights
Streptococcus agalactiae, or Group B streptococcus (GBS) is an important pathogen causing sepsis and meningitis in newborns and mastitis in bovine (Edwards and Baker, 2005; Tazi et al, 2011; Edmond et al, 2012; Lamagni et al, 2013)
Tilapia intestinal samples were collected at 0 h, 12 h, 24 h, 3 d, 7 d, and 15 d after oral administration of S. agalactiae, respectively
The results showed that both YM001 and HN016 can be colonized in the foregut, rectum, duodenum and hindgut, but their number and distribution were significantly different
Summary
Streptococcus agalactiae, or Group B streptococcus (GBS) is an important pathogen causing sepsis and meningitis in newborns and mastitis in bovine (Edwards and Baker, 2005; Tazi et al, 2011; Edmond et al, 2012; Lamagni et al, 2013). S. agalactiae is a common aquaculture pathogen that can harm different fish species, such as tilapia, Barcoo grunter (Scortum barcoo), golden pompano (Trachinotus blochii), ya-fish (Schizothorax potanini), giant queensland grouper (Epinephelus lanceolatus), and silver pomfret (Pampus argenteus) (Jafar et al, 2008; Amal et al, 2012; Li et al, 2015). Outbreaks of S. agalactiae in tilapia have cost more than 40 million dollars every year worldwide (Mian et al, 2009; Chen et al, 2012). The use of antibiotics in aquaculture is severely restricted (Depaola et al, 1995; Baquero et al, 2008)
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