Co-occurrence of heterogeneous Flavobacterium psychrophilum isolates within the same Chilean farm and during the same infectious outbreak

Flavobacterium psychrophilum is a pathogenic bacterium affecting Chilean salmonid farms. High antigenic and genetic diversity exists among Chilean F. psychrophilum isolates, but the distribution thereof among farms is poorly understood. These epidemiological data are key for developing isolate-specific vaccines. The present study isolated F. psychrophilum in diseased Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss) from five freshwater farms between 2018 and 2019. Each farm only raised one salmonid species and was geographically separated from and did not share culturing water with the other farms. Antigenic and genetic analyses were conducted to shed light on the possibility of isolates coexisting within the same farm during outbreaks. A total of 68 Chilean F. psychrophilum isolates were recovered from skin lesions, gills, fins, kidney and spleen of moribund and live fish. Among the 68 Chilean isolates, mPCR-serotyping indicated three major serotypes (i.e. 23.5% type 0; 47.1% type 2; and 26.5% type 4) and, to a lesser degree, serotype 1 (2.9%). Sixteen antigenic groups were detected by slide agglutination. Genetic characterizations by 16S rRNA alleles identified 71% of the isolates as the virulent genogroup CSF259-93 allele. A predominant serotype was associated with each farm, with types 0 and 4 related to Atlantic salmon and types 1 and 2 to rainbow trout. Notwithstanding, several antigenic groups coexisted within some farms. Likewise, the experimental intramuscular challenges (n = 20) demonstrated that the type-2 isolates from rainbow trout were the most pathogenic among isolates recovered from infectious outbreaks in Atlantic salmon, especially as compared to those from types-0 and -4. These results allow us to suggest that prevention measures, specifically vaccines, should be developed according to dominant isolates and with specificity to each farm, that is the use of autogenous or site-specific vaccines.

Different factors limit early- and late-season windows of opportunity for monarch development

Seasonal windows of opportunity are intervals within a year that provide improved prospects for growth, survival, or reproduction. However, few studies have sufficient temporal resolution to examine how multiple factors combine to constrain the seasonal timing and extent of developmental opportunities. Here, we document seasonal changes in milkweed (Asclepias fascicularis)-monarch (Danaus plexippus) interactions with high resolution throughout the last three breeding seasons prior to a precipitous single-year decline in the western monarch population. Our results show early- and late-season windows of opportunity for monarch recruitment that were constrained by different combinations of factors. Early-season windows of opportunity were characterized by high egg densities and low survival on a select subset of host plants, consistent with the hypothesis that early-spring migrant female monarchs select earlier-emerging plants to balance a seasonal trade-off between increasing host plant quantity and decreasing host plant quality. Late-season windows of opportunity were coincident with the initiation of host plant senescence, and caterpillar success was negatively correlated with heatwave exposure, consistent with the hypothesis that late-season windows were constrained by plant defense traits and thermal stress. Throughout this study, climatic and microclimatic variations played a foundational role in the timing and success of monarch developmental windows by affecting bottom-up, top-down, and abiotic limitations. More exposed microclimates were associated with higher developmental success during cooler conditions, and more shaded microclimates were associated with higher developmental success during warmer conditions, suggesting that habitat heterogeneity could buffer the effects of climatic variation. Together, these findings show an important dimension of seasonal change in milkweed-monarch interactions and illustrate how different biotic and abiotic factors can limit the developmental success of monarchs across the breeding season. These results also suggest the potential for seasonal sequences of favorable or unfavorable conditions across the breeding range to strongly affect monarch population dynamics.

First report and characterization of Tenacibaculum maritimum isolates recovered from rainbow trout (Oncorhynchus mykiss) farmed in Chile

The present study reports on the first isolation of Tenacibaculum maritimum in rainbow trout (Oncorhynchus mykiss) farmed in Chile. In March 2020, two cages raising rainbow trout (~250 g) in the Los Lagos Region suffered a disease outbreak. In total, 17,554 fish died (3.5%-4.8% accumulated mortality). Microbiological analysis of the diseased fish obtained two representative isolates (i.e. Tm-035 and Tm-036). These were obtained from the external gross skin lesions-typical of tenacibaculosis-of two fish. Phenotyping, PCR tests and sequencing of the 16S rRNA and housekeeping genes confirmed the isolates as T. maritimum. The pathogenic potential of Tm-035 was further assessed by bath challenging Atlantic salmon (Salmo salar), which killed 70 ± 15% of fish within 11 days. Dead fish presented the same external clinical signs as did the farmed rainbow trout specimens. This research further broadens the known host distribution of this pathogen. Furthermore, the virulence experiments demonstrated that T. maritimum does not have a specific host. Additional studies are needed to evaluate the risk of T. maritimum for the O. mykiss farming industry.

Characterization of the promoter of Grapevine vein clearing virus

Grapevine vein clearing virus (GVCV) is a recently discovered DNA virus in grapevine that is closely associated with the grapevine vein clearing syndrome observed in vineyards in Missouri and surrounding states. The genome sequence of GVCV indicates that it belongs to the genus Badnavirus in the family Caulimoviridae. To identify the GVCV promoter, we cloned portions of the GVCV large intergenic region in front of a GFP gene present in an Agrobacterium tumefaciens binary vector. GFP expression was assessed by ELISA 3 days after agroinfiltration of Nicotiana benthamiana leaves. We found that the GVCV DNA segment between nts 7332 and 7672 directed expression of GFP and this expression was stronger than expression using the Cauliflower mosaic virus 35S promoter. It was revealed by 5' and 3' RACE that transcription was initiated predominantly at nt 7571 and terminated at nt 7676.

Effect of policosanol on platelet aggregation in healthy volunteers

Policosanol is a new drug whose cholesterol-lowering effects have been demonstrated in experimental models, healthy volunteers, and patients with type II hypercholesterolaemia. The effect of policosanol on platelet aggregation was investigated in a randomized, placebo-controlled, double-blind study conducted on healthy volunteers. This included a trial of the effects of single doses (5 to 50 mg) and a study of the effects of repeated doses administered for 7 days. In the single-dose study, the percentage of platelet aggregation in response to the threshold concentration of ADP and epinephrine measured from 8:00 to 10:00 increased significantly in the placebo group, while policosanol (5, 10, 25 and 50 mg), administered orally, inhibited the increase of platelet aggregation induced by ADP and epinephrine determined at the same time. Policosanol administered at 20 mg/day for 7 days significantly inhibited platelet aggregation induced by ADP and epinephrine, although the inhibition reached by the 10 mg/day dose tended to be less significant (p = 0.06). A modest effect (p = 0.068) on collagen-induced platelet aggregation was only observed at the highest dose (50 mg/day). The low dose (5 mg/day) was ineffective. Policosanol did not affect the coagulation time when administered at single or repeated doses. No side-effects were reported in treated or placebo groups.

Modified inoculum for the enteric Minitek system from positive blood cultures

A modified Minitek inoculum procedure for the identification of Enterobacteriaceae from positive blood cultures was shown to be reliable. The method consisted of inoculating the Minitek enteric and nonfermenter broth with blood culture fluid and incubating the inoculum for 4 h before use.

Measurement of toe temperature for assessing the severity of acute circulatory failure

The temperature gradient between the ventral surface of the first toe and the ambient temperature was measured and compared with established hemodynamic measurements in 71 critically ill patients. Thirty-two patients had acute myocardial infarctions, 21 patients had primary bacteremia and 18 patients had primary hypovolemia which followed acute blood loss. The temperature gradient served as a more predictable indicator of survival or fatality than either arterial pressure or cardiac index in each group of patients. Patients who improved after treatment and survived had increases in the toe minus ambient temperature gradient to more than 4 degrees C., whereas a gradient of less than 3 degrees over an interval of 12 hours was typically observed in patients who subsequently died. These observations indicate that the toe minus ambient temperature gradient provides a valuable, inexpensive and noninvasive monitor of tissue perfusion in critically ill patients.