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

Marcin Kalinowski,Tsutomu Kakuda,Łukasz Jarosz,Yu Hieda,Zbigniew Grądzki,Shinji Takai,Kiyoko Kato,Riccardo Manganelli

doi:10.1371/journal.pone.0152887

Marcin Kalinowski, Tsutomu Kakuda + Show 6 more

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https://doi.org/10.1371/journal.pone.0152887

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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.

Highlights

Rhodococcus equi is an important bacterial pathogen in young foals up to 6 months old [1,2]
The same concerns the relationship between the plasmid type and date of R. equi isolation (Table 1). This is the first study undertaken in Poland aiming at the characterisation of plasmid profiles of Polish field R. equi strains isolated of foals and soil samples
Our preliminary results indicate that virulent R. equi strains isolated from diseased foals and horse farms environment represent a similar plasmid pattern, because all isolates except one isolated so far in Poland were classified as belonging to VapA 85 kb type I

Summary

Introduction

Rhodococcus equi is an important bacterial pathogen in young foals up to 6 months old [1,2]. It was found previously 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 [12]. Those VapA-positive strains are much more prevalent in farms with endemic disease comparing to farms without or with sporadic infections [13]. The aim of the study is to determine plasmid profiles of virulent R. equi strains isolated in Poland from dead foals with confirmed rhodococcosis as well as from soil samples taken from horse breeding farms

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