Comprehensive antibiotic susceptibility profiling of Chilean <i>Piscirickettsia salmonis</i> field isolates

Henríquez, Patricio; Kaiser, Melanie; Bohle, H.; Bustos, Patricio; Mancilla, Marcos

doi:10.1111/jfd.12427

Cited by 75 publications

(83 citation statements)

References 20 publications

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“…Yáñez et al (2014) tested only three isolates making any comparison with their data of limited value. Henríquez et al (2015) performed a much larger study and it would seem worthwhile to compare the information available on the performance characteristics of the protocols they used and the protocols used in this work.…”

Section: Discussionmentioning

confidence: 99%

“…The degree of separation between the distribution of MICs for WT isolates and for NWT isolates would, therefore, represent a significant basis for a comparison of the performance of different test protocols. This study and that of Henríquez et al (2015) studied the susceptibility of Chilean isolates of P. salmonis , it would seem reasonable to examine the relative degree of WT/NWT separation they achieved.…”

Section: Discussionmentioning

confidence: 99%

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A Novel and Validated Protocol for Performing MIC Tests to Determine the Susceptibility of Piscirickettsia salmonis Isolates to Florfenicol and Oxytetracycline

et al. 2017

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This paper presents a validated protocol, using a novel, specifically formulated medium, to perform broth microdilution antimicrobial susceptibility assays of the salmonid bacterial pathogen Piscirickettsia salmonis. The minimum inhibitory concentrations (MIC) for florfenicol and oxytetracycline against 58 P. salmonis isolates recovered from various outbreaks occurred in Chilean salmonid farms were determined using this protocol. Normalized resistance interpretation (NRI) analysis was applied to these data to calculate appropriate protocol-specific epidemiological cut-off values. These cut-off values allow the isolates to be categorized as either fully susceptible wild type (WT) members of this species, or as manifesting reduced susceptibility non-wild type (NWT). The distribution of MIC values of florfenicol was bimodal and the distribution of the normalized values for the putative WT observation had a standard deviation of 0.896 log2 μg mL-1. This analysis calculated a cut-off value of ≤0.25 μg mL-1 and categorized 33 (56%) of the isolates as manifesting reduced susceptibility to florfenicol. For the oxytetracycline MIC data the NRI analysis also treated the distribution as bimodal. The distribution of the normalized values for the putative WT observation had a standard deviation of 0.951 log2 μg mL-1. This analysis gave a cut-off value of ≤0.5 μg mL-1 and categorized five isolates (9%) as manifesting reduced susceptibility to oxytetracycline. The susceptibility testing protocol developed in this study was capable of generating MIC data from all the isolates tested. On the basis of the precision of the data it generated, and the degree of separation of values for WT and NWT it achieved, it is argued that this protocol has the performance characteristics necessary for it to be considered as a standard protocol.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

A Novel and Validated Protocol for Performing MIC Tests to Determine the Susceptibility of Piscirickettsia salmonis Isolates to Florfenicol and Oxytetracycline

et al. 2017

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“…Similar disease outbreaks have later been diagnosed in Ireland and Scotland (4), Norway (5), and the Atlantic and Pacific coasts of Canada (6). SRS still causes major losses in salmon farming in Chile, and current annual losses are estimated at 250 million USD and the infection results in a high consumption of antibiotics toward the end of the production cycle (7). Disease outbreaks are seen in all salmonid species farmed in Chile, Chinook salmon ( Oncorhynchus tshawytscha ), rainbow trout ( Oncorhynchus mykiss ), and Atlantic salmon ( Salmo salar L.) (7), and also in other species like Sakura salmon ( Oncorhynchus masou ) (8), and pink salmon ( Oncorhynchus gorbuscha ) (1).…”

Section: Introductionmentioning

confidence: 99%

“…SRS still causes major losses in salmon farming in Chile, and current annual losses are estimated at 250 million USD and the infection results in a high consumption of antibiotics toward the end of the production cycle (7). Disease outbreaks are seen in all salmonid species farmed in Chile, Chinook salmon ( Oncorhynchus tshawytscha ), rainbow trout ( Oncorhynchus mykiss ), and Atlantic salmon ( Salmo salar L.) (7), and also in other species like Sakura salmon ( Oncorhynchus masou ) (8), and pink salmon ( Oncorhynchus gorbuscha ) (1). Infections with Rickettsia -like organisms (RLO) have been reported in Mediterranean sea bass ( Dicentrarchus labrax ) (9), white sea bass ( Atractoscion nobilis ) (10), grouper ( Epinephelus melanostigma ) (11), and five species of tilapia (12).…”

Section: Introductionmentioning

confidence: 99%

Immunization Strategies against Piscirickettsia salmonis Infections: Review of Vaccination Approaches and Modalities and Their Associated Immune Response Profiles

Evensen

2016

Front. Immunol.

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Salmonid rickettsial septicemia (SRS) is a serious, infectious disease in Chilean salmon farming caused by Piscirickettsia salmonis, causing heavy losses to the salmonid industry. P. salmonis belongs to the Gammaproteobacteria, order Thiotrichales. SRS was first described in Chile in 1989, and infection with P. salmonis has since been described from a high number of fish species and in several geographic regions globally. P. salmonis infection of salmonids causes multifocal, necrotic areas of internal organs such as liver, kidney, and spleen. Histologically and immunologically, the tissue response is the formation of granulomas, often with central suppuration. The exact sequence of infection is not known, but bacteria likely gain access to internal organs through mucosal surfaces and when infected, fish carry bacteria in macrophages. It has not been fully determined if the bacterium resides in the cytosol or “hide” within vesicular structures intracellularly, although there are indications that in vitro infection results in actin reorganization and formation of actin-coated vesicle within which the bacterium resides. Protection against lethal challenge is well documented in lab scale experiments, but protection from vaccination has proven more difficult to attain long term under field conditions. Current vaccination protocols include whole cell, inactivated and adjuvanted vaccines for injection for primary immunization followed by oral boost where timing of boost delivery is followed by measuring circulating antibody levels against the pathogen. Documentation also exist that there is correlation between antibody titers and protection against mortality. Future vaccination regimes will likely also include live-attenuated vaccines or other technologies such as DNA vaccination. So far, there is no documentation available for live vaccines and, for DNA vaccines, studies have been unsuccessful under laboratory conditions.

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“…Culture of P. salmonis on liquid or solid medium was performed on ADL-PSB or PSA, respectively (Henriquez, Kaiser, Bohle, Bustos, & Mancilla, 2016), at 18°C, while Escherichia coli strains were cultured on tryptic soy broth, TSB (Becton-Dickinson, Franklin Lakes, NJ, USA) or agar (TSA) at 37°C. All media were supplemented with 10 lg/ml of polymyxin B, 50 lg/ml of kanamycin, or both, depending on the purpose of the experiment.…”

Section: Bacterial Strains Growth Conditions and Plasmidsmentioning

confidence: 99%

The mutagenesis of a type IV secretion system locus of Piscirickettsia salmonis leads to the attenuation of the pathogen in Atlantic salmon, Salmo salar

Mancilla¹,

Saavedra²,

Grandón³

et al. 2017

Journal of Fish Diseases

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Piscirickettsiosis is a threatening infectious disease for the salmon industry, due to it being responsible for significant economic losses. The control of outbreaks also poses considerable environmental challenges. Despite Piscirickettsia salmonis having been discovered as the aetiological agent of the disease more than 25 years ago, its pathogenicity remains poorly understood. Among virulence factors identified so far, type four secretion systems (T4SS) seem to play a key role during the infection caused by the bacterium. We report here the genetic manipulation of P. salmonis by means of the transference of plasmid DNA in mating assays. An insertion cassette was engineered for targeting the icmB gene, which encodes a putative T4SS‐ATPase and is carried by one of the chromosomal T4SS clusters found within the genome of P. salmonis PM15972A1, a virulent representative of the EM‐90‐like strain. The molecular characterization of the resulting mutant strain demonstrated that the insertion interrupted the target gene. Further in vitro testing of the icmB mutant showed a dramatic drop in infectivity as tested in CHSE‐214 cells, which is in agreement with its attenuated behaviour observed in vivo. Altogether, our results demonstrate that, similar to other facultative intracellular pathogens, P. salmonis’ virulence relies on an intact T4SS.

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Comprehensive antibiotic susceptibility profiling of Chilean Piscirickettsia salmonis field isolates

Cited by 75 publications

References 20 publications

A Novel and Validated Protocol for Performing MIC Tests to Determine the Susceptibility of Piscirickettsia salmonis Isolates to Florfenicol and Oxytetracycline

A Novel and Validated Protocol for Performing MIC Tests to Determine the Susceptibility of Piscirickettsia salmonis Isolates to Florfenicol and Oxytetracycline

Immunization Strategies against Piscirickettsia salmonis Infections: Review of Vaccination Approaches and Modalities and Their Associated Immune Response Profiles

The mutagenesis of a type IV secretion system locus of Piscirickettsia salmonis leads to the attenuation of the pathogen in Atlantic salmon, Salmo salar

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