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Flavobacterium psychrophilum causes rainbow trout fry syndrome (RTFS) and cold water disease (CWD) in salmonid aquaculture. We report characterization of F. psychrophilum strains and their bacteriophages isolated in Chilean salmonid aquaculture. Results suggest that under laboratory conditions phages can decrease mortality of salmonids from infection by their F. psychrophilum host strain. Twelve F. psychrophilum isolates were characterized, with DNA restriction patterns showing low diversity between strains despite their being obtained from different salmonid production sites and from different tissues. We isolated 15 bacteriophages able to infect some of the F. psychrophilum isolates and characterized six of them in detail. DNA genome sizes were close to 50 Kbp and corresponded to the Siphoviridae and Podoviridae families. One isolate, 6H, probably contains lipids as an essential virion component, based on its chloroform sensitivity and low buoyant density in CsCl. Each phage isolate rarely infected F. psychrophilum strains other than the strain used for its enrichment and isolation. Some bacteriophages could decrease mortality from intraperitoneal injection of its host strain when added together with the bacteria in a ratio of 10 plaque-forming units per colony-forming unit. While we recognize the artificial laboratory conditions used for these protection assays, this work is the first to demonstrate that phages might be able protect salmonids from RTFS or CWD.

The use of bacteriophages has been proposed as an alternative method to control pathogenic bacteria. During recent years several reports have been published about the successful use of bacteriophages in different fields such as food safety, agriculture, aquaculture, and even human health. Several companies are now commercializing bacteriophages or bacteriophage-based products for therapeutic purposes. However, this technology is still in development and there are challenges to overcome before bacteriophages can be widely used to control pathogenic bacteria. One big hurdle is the development of efficient methods for bacteriophage production. To date, several models for bacteriophage production have been reported, some of them evaluated experimentally. This mini-review offers an overview of different models and methods for bacteriophage production, contrasting their principal differences.

A clonal population of pathogenic Vibrio parahaemolyticus O3 : K6 serovar has spread in coastal waters, causing outbreaks worldwide since 1996. Bacteriophage infection is one of the main factors affecting bacterial strain concentration in the ocean. We studied the occurrence and properties of phages infecting this V. parahaemolyticus pandemic strain in coastal waters. Analysing 143 samples, phages were found in 13. All isolates clustered in a closely related group of podophages with at least 90% nucleotide sequence identity in three essential genes, despite distant geographical origins. These bacteriophages were able to multiply on the V. parahaemolyticus pandemic strain, but the impact on host concentration and subsequent growth was negligible. Infected bacteria continued producing the phage but were not lysogenized. The phage genome of prototype strain VP93 is 43 931 nucleotides and contains 337 bp direct terminal repeats at both ends. VP93 is the first non-Pseudomonas phage related to the PhiKMV-like subgroup of the T7 supergroup. The lack of a major effect on host growth suggests that these phages exert little control on the propagation of the pandemic strain in the environment. This form of phage growth can be modelled if phage-sensitive and -resistant cells that convert to each other with a high frequency are present in clonal cultures of pandemic V. parahaemolyticus.

No abstract

Seafood consumption-related diarrhoea increased drastically in Chile when the pandemic strain of Vibrio parahaemolyticus serotype O3:K6 reached Region de Los Lagos, where most of Chile's seafood is produced. Outbreaks peaked in 2005 with 3725 clinical cases in this region and gradually decreased to fewer than 10 cases in 2010 and 2011. We show here that the pandemic strain concurrently vanished from mussels; we also report further environmental data. Integration of the 2010/2011 data with those obtained since 2004 suggests that after its arrival in southern Chile, the pandemic strain grew in mussels, likely facilitated by a minor rise in surface seawater temperature and by warming of the mussels in the intertidal region due to frequent sunny days. However, since these environmental parameters probably equally affected the pandemic strain and more than 30 V. parahaemolyticus DNA restriction clusters that inhabit local shellfish, a selective effect of bacteriophages is proposed. Lytic bacteriophage VP93 may have favoured the growth of the pandemic strain versus similar phage-sensitive strains, as shown here in a particular case. However, the pandemic strain's decline may have been promoted by temperate phage VP58.5, which kills the pandemic strain and increases the UV sensitivity of lysogenized phage-resistant cells.

Xanthomonas arboricola pv. juglandis is an important pathogen responsible for walnut blight outbreaks globally. Here, we report four draft genome sequences of X. arboricola pv. juglandis strains isolated from Chilean walnut trees.

Artículo de publicación ISIBackground: The surveillance of Vibrio parahaemolyticus in the Chilean coast has been mainly performed by multiplex PCR amplification of three different hemolysin genes, which are specie-specific virulence factors. These genes are also employed in the determination of V. parahaemolyticus pathogenic load in seafood and for characterization of pathogenic strains associated to diarrhea cases in human. During environmental surveillance that we performed every summer, we occasionally observed a thermolabile hemolysin (tlh) PCR product of a slightly smaller size than expected, which was coincident with low loads of V. parahaemolyticus in the environment. In order to understand this observation, we probed the specificity of tlh primers for the detection of V. parahaemolyticus at different bacterial loads and DNA concentrations. Results: Primers used for the detection of V. parahaemolyticus specific tlh amplified a slightly smaller tlh gene, which is found in Vibrio alginolyticus and other related strains. These amplicons were observed when V. parahaemolyticus was absent or in undetectable loads in the environment. Conclusions: Surveillance of V. parahaemolyticus using tlh primers can be imprecise because amplification of a V. parahaemolyticus specific marker in V. alginolyticus and other related strains occurs. This situation complicates potentially the estimation of bacterial load in seafood, because do not ensure the correct identification of V. parahaemolyticus when his load is low. Additionally, it could complicate the tracking of outbreaks of V. parahaemolyticus infections, considering the genetic markers used would not be specie-specific.Fondecyt 11140257 11140412 Scientific Information Program/Fund for Scientific Journals Publishing FP14001