title: Effect of growth temperature on maintenance of virulent Rhodococcus equi.
abstract: Repeated passage of virulent Rhodococcus equi ATCC 33701 and L1 at 38 degrees C resulted in attenuation of the strains as a result of curing the virulence plasmid; at 30 degrees C, repeated passage had no such effect. At a temperature of 38 degrees C the plasmid-bearing cells replicated more slowly than their plasmid-cured derivatives and so were gradually replaced by cells lacking plasmids. In contrast, at a temperature of 30 degrees C the growth rate of either strain was not affected by the presence or absence of the plasmid. No plasmid-cured derivative was recovered from mouse organs at 48 h after inoculation of a mixture of equal numbers of bacteria with and without plasmids. It is concluded that under nonselective conditions growth temperature is an important factor in maintaining the virulence of R. equi.
authors.affiliation: Department of Animal Hygiene, School of Veterinary Medicine and Animal Sciences, Kitasato University, Aomori, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Takai
authors.forename: T
authors.initials: T
authors.lastname: Sugawara
authors.forename: Y
authors.initials: Y
authors.lastname: Watanabe
authors.forename: Y
authors.initials: Y
authors.lastname: Sasaki
authors.forename: S
authors.initials: S
authors.lastname: Tsubaki
authors.forename: T
authors.initials: T
authors.lastname: Sekizaki
mesh_terms: D000193:Actinomycetales Infections / Q000382:microbiology*; D000818:Animals; D005260:Female; D007928:Lethal Dose 50; D051379:Mice; D010957:Plasmids; D016929:Rhodococcus equi / Q000235:genetics / Q000254:growth & development* / Q000472:pathogenicity; D012692:Serial Passage; D013696:Temperature; D014774:Virulence / Q000235:genetics; D014779:Virus Replication