Induction and characterization of lysogenic bacteriophages fromStreptococcus iniae

Abstract

Aims: To investigate the presence of prophage in Streptococcus iniae, a highly problematic fish pathogen. Methods and Results: Cross-spotting assays and mitomycin C inductions were conducted to screen for prophage in 48 Strep. iniae isolates. Bacteriophages were characterized by plaque assays, transmission electron microscopy and DNA restriction enzyme digestion. Plaque assays confirmed prophages in 14Á6% of isolates. lysed 78Á5% of Strep. iniae isolates and displayed distinctive host ranges. Microscopy revealed virions exhibiting long, non-contractile tails and isometric heads consistent with phages from the family Siphoviridae. Restriction digests revealed genome sizes ranging from 27Á5 to 66Á3 kbp, with distinct cutting patterns that indicate the presence of related prophages in bacteria isolated from different geographic regions. Conclusions: The rate of prophage carriage found is comparably low and induction rates varied between phages. The four characterized Siphoviridae phages have broad host ranges within the Strep. iniae isolates. Significance and Impact of the Study: This is the first description and characterization of lysogenic phages from Strep. iniae. These phages are candidates for research and diagnosis of the bacterium and their identification should accelerate the discovery of lytic phages to be trialled against Strep. iniae infections in fish.

Salmonella and Campylobacter : Antimicrobial resistance and bacteriophage control in poultry

“…This cycle uses the bacteria's machinery as do the other two cycles; however, filamentous systems do not result in cell death, rather continuous production and release of phages into the environment (Yee et al, 2013). The phages used for therapeutic purposes are usually strictly lytic (Wright et al, 2013) and mainly occupy three families of the order Caudovirales: Myoviridae, Siphoviridae, and Podoviridae (Wittebole et al, 2013). Phages are increasingly being studied and used to combat poultry related pathogens (Zhang et al, 2010), specifically Salmonella and Campylobacter during pre-and post-harvest.…”

“…Lysogenic phages inject their genome into the host cell which allows the host to replicate and pass the phage genome to the daughter cells, and bacterial death only occurs when initiated by environmental stimuli. Lysogenic cycles can result in increased amounts of phage gene transfer and contributes to bacterial phage resistance (Wright et al, 2013). There is a third, albeit less common, phage life cycle referred to as filamentous.…”

Induction and characterization of a lysogenic bacteriophage of Lactococcus garvieae isolated from marine fish species

“…; Wright et al . ). According to an epidemiological study on L. garvieae strains isolated from diseased fish in Japan, the S1 genotype is predominant in aquaculture and accounts for more than 74% of the strains (316/427) (Nishiki et al .…”

“…These results are in agreement with other studies showing that MMC does not induce all lysogenic phages, even though MMC was considered to be the most powerful inducing agent (Barksdale & Arden ; Loessner, Goeppl & Busse ; Wright et al . ). It is also possible that there are mutations in the prophages that were not detected by either PCR or restriction fragment analysis.…”

“…Lysogenic phage PLgT-1 of L. garvieae belongs to the family Siphoviridae according to its morphological features and the classification proposed by Ackermann (2001). Phages of this family were also detected in other lysogenic bacterial strains that cause streptococcosis, such as Streptococcus iniae and S. pyogenes (Canchaya et al 2002;Wright et al 2013). According to an epidemiological study on L. garvieae strains isolated from diseased fish in Japan, the S1 genotype is predominant in aquaculture and accounts for more than 74% of the strains (316/427) (Nishiki et al 2011).…”