Plasmid Profiles of Virulent Rhodococcus equi Strains Isolated from Infected Foals in Poland

Abstract

Rhodococcus equi is an important bacterial pathogen in foals up to 6 months old, widespread in horse farms all over the world. It was found that only virulent R. equi strains expressing 15–17 kDa virulence-associated protein (VapA) and having large virulence plasmid of 85–90 kb containing vapA gene are pathogenic for horses. To date, 12 plasmid types have been reported in VapA positive strains from horses. There are no data concerning plasmid types of Polish field R. equi strains isolated from horses and horse farm environment. The aim of the study is to determine plasmid profiles of virulent R. equi strains isolated in Poland from dead foals as well as from soil samples taken from horse breeding farms. Plasmid profiles of 10 clinical strains derived from 8 farms and 11 environmental strains from 3 farms, confirmed as virulent by PCR, were compared with 12 reference strains containing the known plasmid size and type. Plasmid DNAs were analysed by digestion with the restriction endonucleases BamHI, EcoRI, EcoT22I, and HindIII for detailed comparison and estimation of plasmid sizes. The results of RFLP analysis revealed that all except one isolates used in the study are classified as VapA 85 kb type I plasmid. One strain harboured VapA 87 kb type I plasmid. This is the first report of plasmid types of Polish field R. equi strains. The results of our preliminary investigations on horse farms located in central and eastern Poland indicate that the virulent R. equi strains thus far isolated from diseased foals and horse farms environment represent a highly uniform plasmid pattern.

Molecular analysis of the chromosomal 16S rRNA gene and vapA plasmid gene of Polish field strains of R. equi

“…All microbial strains had the vapA virulence gene. In addition, in previous research [ 33 ] to determine the plasmid profiles of clinical and environmental strains of R . equi occurring in Poland, the majority of strains were classified as presenting the 85-kb type I profile.…”

“…The material for the laboratory tests was collected during the anatomopathological examination from abscesses located in the lung tissue, using a sterile Pasteur pipette. The procedure for isolation and identification of bacteria from pus samples has been described in a previous paper [ 33 ]. After identification, clinical strains numbered 1–22 were stored for further testing in a 20% suspension of glycerol in PBS at −70°C.…”

“…In total, 55 soil samples were collected for laboratory testing. The procedure for isolation and identification of bacteria from soil samples was described in a previous paper [ 33 ]. The environmental strains were numbered 23–40 and stored for further testing in a 20% suspension of glycerol in PBS at −70°C.…”

“…Literature data on the genotypic characteristics of R . equi strains isolated in Poland are scarce [ 33 – 34 ]. Most reports from around the world focus on the determination of R .…”

Ecological Monitoring of Lacz Marked Strain of Azotobacter Chroococcum in the Rhizoplane of Triticum Aestivum

“…To assess the potential of agriculturally important microorganisms including Azotobacter chroococcum in terms of increase in yield, it is essential to monitor the survival and persistence of inoculated strains of bacteria in soil. Strain identification has been done using different methods based on serological properties 1 , bacteriophage susceptibility 2 , antibiotic resistant markers 3 , DNA homology 4 and plasmid profile 5,6 . Since such studies are very laborious, there is a need for simple and specific methods of strain identification.…”