Aeromonas hydrophila AHL 0905-2 and Streptococcus agalactiae N14G as Combined Vaccine Candidates for Nile Tilapia

Abstract

In Indonesia, the Nile tilapia (Oreochromis niloticus) is the most widely farmed and available fish for consumption. Production loss due to bacterial infection by Aeromonas hydrophila and Streptococcus agalactiae is the main problem in tilapia cultivation. This study aimed to determine the occurrence of concurrent infection of Aeromonas hydrophila AHL 0905-2 and Streptococcus agalactiae N14G in Nile tilapia based on biochemical and molecular characteristics. From the results of biochemical assay and sequence analysis of the 16S rRNA fragment, Aeromonas hydrophila and Streptococcus agalactiae were confirmed. Genes for aerolysin (417 bp), nuclease (504 bp), lipase (155 bp), and serine protease (211 bp) were found in Aeromonas hydrophila AHL 0905-2, while Streptococcus agalactiae N14G was determined as a 1b serotype group that had genes for CPS L (688 bp), CPSG (621 bp), and CPS J (272 bp). The confirmation in tilapia of Aeromonas hydrophila and Streptococcus agalactiae by PCR and sequencing is important for enabling the detection of these organisms and also for the development of a combined vaccine to tackle co-infection.

Impact of temperature on the virulence of Streptococcus agalactiae in Indonesian aquaculture: A better vaccine design is required

“…The next vaccine consisted of two antigens, namely, a combination of S. agalactiae and Aeromonas hydrophila, in which A. hydrophila was thought to often exacerbate Streptococcus. The next vaccine consists of three types of antigens with the aim providing of better protection against streptococcosis [76,77].…”

Streptococcosis on Nile tilapia (Oreochromis niloticus) in Indonesian freshwater aquaculture

“…Based on morphological, physical, and biochemical assays (Taukhid & Purwaningsih, 2011;Hardi et al, 2011;Taukhid et al, 2014;Suhermanto et al, 2019) and confirmatory molecular diagnosis (Nafiqoh et al, 2022), it was concluded that S. agalactiae is the predominant cause of streptococcosis on tilapia culture in Indonesia, and based on phylogenetic tree analysis of a number of isolates that have been characterized two biotypes were confirmed, i. e. S. agalactiae β-hemolytic and non-hemolytic (Suhermanto et al, 2019).…”

“…Diagnosis Level III, the diagnosis can be used as confirmatory/definitive diagnosis (if needed) performed molecularity (Polymerase Chain Reaction/PCR and/or DNA sequencing with 16 and 23S rRNA genes) of pure cultures of S. agalactiae bacteria. Molecular detection of S. agalactiae bacteria has been widely practiced, among others by (Jiménez et al, 2011;Rodkhum et al, 2011;Angel et al, 2014;Kayansamruaj et al, 2014;Nafiqoh et al, 2022). Detecting genes to the molecular level, not only knows the species of bacteria to the species level; but can also determine the genetic clustering of the bacteria isolates.…”