MLVA genotyping of Moritella viscosa reveals serial emergence of novel, host-specific clonal complexes in Norwegian salmon farming.

A Multi-Locus Variable number of tandem repeat Analysis (MLVA) genotyping scheme was developed for the epidemiological study of Moritella viscosa, which causes 'winter ulcer' predominantly in sea-reared Atlantic salmon (Salmo salar L.). The assay involves multiplex PCR amplification of six Variable Number of Tandem Repeat (VNTR) loci, followed by capillary electrophoresis and data interpretation. A collection of 747 spatiotemporally diverse M. viscosa isolates from nine fish species was analysed, the majority from farmed Norwegian salmon. MLVA distributed 76% of the isolates across three major clonal complexes (CC1, CC2 and CC3), with the remaining forming minor clusters and singletons. While 90% of the salmon isolates belong to either CC1, CC2 or CC3, only 20% of the isolates recovered from other fish species do so, indicating a considerable degree of host specificity. We further highlight a series of 'clonal shifts' amongst Norwegian salmon isolates over the 35-year sampling period, with CC1 showing exclusive predominance prior to the emergence of CC2, which was later supplanted by CC3, before the recent re-emergence of CC1. Apparently, these shifts have rapidly swept the entire Norwegian coastline and conceivably, as suggested by typing of a small number of non-Norwegian isolates, the Northeast Atlantic region as a whole.

Pirfenidone and candesartan ameliorate morphological damage in mild chronic anti-GBM nephritis in rats.

BACKGROUND: The antifibrotic substance pirfenidone and the angiotensin II type I receptor antagonist candesartan cilexetil, given alone and in combination, were tested in rats with chronic anti-glomerular basement membrane glomerulonephritis (anti-GBM GN). METHODS: Male Wistar rats with anti-GBM GN were treated for 8 weeks with candesartan (4 mg/kg body weight/day), pirfenidone (500 mg/kg body weight/day) or a combination of both drugs. One GN group received no treatment and untreated non-GN-rats were used as controls. Blood pressure and urinary protein excretion were measured after 3 and 7 weeks. Kidney histology was complemented by ultrastructural investigation and by quantification of collagen Ialpha mRNA. RESULTS: The percentage of glomeruli with adsorption droplets in podocytes correlated well with the amount of proteinuria (r = 0.873, P<0.01) and was significantly lowered in rats treated with candesartan (8.3 vs GN 24.6%), pirfenidone (9.8%) and combined treatment (2.6%, P<0.05 vs candesartan alone). A comparable lowering was seen for segmental sclerosis (GN 11%, candesartan 0.7%, P<0.05 vs GN, pirfenidone 1.8%, P = 0.09 vs GN, candesartan/pirfenidone 0.1%, P>0.5 vs candesartan alone). Cortical collagen Ialpha mRNA expression was significantly decreased in all treatment groups. Ultrastructural investigation showed an amelioration of basement membrane alterations and podocyte damage in the treatment groups. Candesartan caused significant blood pressure reduction and the effect was significantly enhanced by combination therapy after 3 weeks. Rats treated with pirfenidone showed blood pressure values similar to control rats. CONCLUSION: Pirfenidone has a beneficial effect on morphological changes in anti-GBM GN comparable with candesartan although with a trend to slightly better results with candesartan treatment. Moreover, our results suggest an additive effect of combination treatment.