16S rRNA gene microbial analysis of the skin of fleece rot resistant and susceptible sheep

Abstract

Fleece rot is a bacterial dermatitis that follows prolonged wetting of the sheep’s skin, and a major pre-disposing condition to body strike in the Australian Merino. Several studies have examined bacterial load of the fleece in relation to fleece rot using traditional culture-based techniques focussing on only a few bacterial species. We examined the natural bacterial diversity of the healthy sheep skin and changes that occurred in fleece-rot resistant and susceptible animals during fleece rot development. Presented is a preliminary molecular genetic analysis of the bacterial ecology of the sheep skin. Eight 16S rRNA gene libraries were constructed from susceptible and resistant sheep both before and after onset of the disease following induction by simulated rainfall. Approximately 75% of the sequences obtained in this study have not been previously identified in fleece-rot studies. Four operational taxonomic units (OTU; groups of >97% sequence similarity) of major interest were present on susceptible animals and absent from resistant animals. Data on these OTU expand current knowledge of bacteria involved in inflammation and wounding of sheep skin tissue, and provide direction for future research that may lead to new treatment options for fleece rot and body strike.

A genomics-informed, SNP association study reveals FBLN1 and FABP4 as contributing to resistance to fleece rot in Australian Merino sheep

“…Interestingly, an earlier report from our group identified Corynebacterium sp. as the most abundant bacterial genera present in the fleece of SUS sheep [ 22 ]. However, no SNPs in this gene were associated with a fleece rot phenotype.…”

Fleece rot in sheep: a review of pathogenesis, aetiology, resistance and vaccines

“…This picture of a complex bacterial aetiology has been borne out by many subsequent studies. The presence of a specialised adapted flora on the wool and skin (Jackson et al 2002) and variation among animals in this flora (Dixon et al 2007) support the concept that resident flora can provide a defence barrier against overgrowth of pathogenic species. This concept of a complex skin microbiome participating in a dynamic ecology with the host has also emerged in studies of human skin in recent years (Oh et al 2016).…”

“…Bacterial profiles on healthy skin and in fleece rot lesions have been investigated using a variety of approaches, including (1) determining infectivity and pathogenicity of bacteria applied to the skin of sheep (Stuart 1894), (2) laboratory culture and examination of colony morphology, growth characteristics and exoproducts (Watts and Merritt 1981b;Burrell and MacDiarmid 1984;MacDiarmid and Burrell 1986;Burrell 1990), (3) DNA profiling (Kingsford and Raadsma 1997;Dixon et al 2007;Norris et al 2008), ( 4) serology (Burrell and MacDiarmid 1984;MacDiarmid and Burrell 1986;Chin and Watts 1992;Dai 1997) and ( 5) the ability of specific vaccines to protect sheep from some fleece rot bacterial species or strains, but not others (MacDiarmid and Burrell 1986;Burrell 1990;Burrell et al 1992;Dai 1997).…”

“…Bacterial culture and microbial DNA analyses have indicated that healthy fleece contains a diversity of bacterial species Merritt 1981a, 1981b;Burrell 1990;Chin and Watts 1992;Lyness et al 1994;Kingsford andRaadsma 1995, 1997;Dixon et al 2007;Norris et al 2008). These populations can undergo sudden and enormous growth in numbers under conditions of high moisture content of fleece and warm temperatures (Watts and Merritt 1981b;Burrell et al 1982;Burrell 1990;Lyness et al 1994;Norris et al 2008).…”

“…More recently, Dixon et al (2007) used 16S rRNA sequence profiles to identify predominant bacterial populations repre senting eight major bacterial orders in samples from skin and wool in two resistant and two susceptible sheep from the NSW DPI selection lines before and following 3 days of artificial wetting. Sheep were free of fleece rot prior to artificial wetting.…”