title: Evidence of lateral gene transfer among strains of Streptococcus zooepidemicus in weanling horses with respiratory disease.
abstract: Streptococcus zooepidemicus (Sz) is a tonsillar commensal of healthy horses but with potential to opportunistically invade the lower respiratory tract. Sz is genetically variable and recombinogenic based on analysis of gene sequences including szp, szm and MLST data. Although a variety of serovars of the protective SzP are commonly harbored in the tonsils of the same horse, lower respiratory infections usually involve a single clone. Nevertheless, isolation of specific clones from epizootics of respiratory disease has been recently reported in horses and dogs in N. America, Europe and Asia. In this report, we provide evidence suggestive of lateral gene exchange and recombination between strains of Sz from cases of respiratory disease secondary to experimental equine herpes 1 virus infection in an isolated group of weanling horses and ponies. Nasal swabs of 13 of 18 weanlings with respiratory disease yielded mucoid colonies of Sz following culture. Comparison of arcC, nrdE, proS, spi, tdk, tpi and yqiL of these Sz revealed 3 Clades. Clade-1 (ST-212) and 2 (ST-24) were composed of 7 and 3 isolates, respectively. ST-24 and 212 differed in all 7 housekeeping as well as szp and szm alleles. Two isolates of Clade-1 were assigned to ST-308, a single locus variant of ST-212 that contained the proS-16 allele sequenced in ST-24. One isolate of ST-308 contained szm-2, the same allele sequenced in Clade 2 isolates; the other was positive for the szp-N2HV2 allele of Clade 2. These observations are consistent with gene transfer between Sz in the natural host and may explain formation of novel clones that invade the lower respiratory tract or cause epizootics of respiratory disease in dogs and horses.
authors.affiliation: Gluck Equine Research Center, University of Kentucky, Lexington, KY, United States.
authors.forename: Sridhar
authors.initials: S
authors.lastname: Velineni
authors.affiliation: Gluck Equine Research Center, University of Kentucky, Lexington, KY, United States.
authors.forename: Cormac C
authors.initials: CC
authors.lastname: Breathnach
authors.affiliation: Gluck Equine Research Center, University of Kentucky, Lexington, KY, United States. Electronic address: jtimoney@uky.edu.
authors.forename: John F
authors.initials: JF
authors.lastname: Timoney
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics*; D004285:Dogs; D022761:Gene Transfer, Horizontal; D006566:Herpesviridae Infections / Q000662:veterinary* / Q000821:virology; D004861:Herpesvirus 1, Equid / Q000502:physiology; D006734:Horse Diseases / Q000382:microbiology* / Q000821:virology; D006736:Horses; D058885:Multilocus Sequence Typing; D011995:Recombination, Genetic; D012141:Respiratory Tract Infections / Q000382:microbiology / Q000662:veterinary* / Q000821:virology; D013290:Streptococcal Infections / Q000150:complications / Q000382:microbiology / Q000662:veterinary*; D018502:Streptococcus equi / Q000145:classification / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins
keywords: Lateral gene transfer; Streptococcus zooepidemicus; proS allele; szm; szp