title: Divergence of a strain of Pseudomonas aeruginosa during an outbreak of ovine mastitis.
abstract: Bacterial infections causing mastitis in sheep can result in severe economic losses for farmers. A large survey of milk samples from ewes with mastitis in Sardinia, Italy, indicated an increasing prevalence of Pseudomonas aeruginosa infections. It has been shown previously that during chronic, biofilm-associated infections P. aeruginosa populations diversify. We report the phenotypic and genomic characterisation of two clonal P. aeruginosa isolates (PSE305 and PSE306) from a mastitis infection outbreak, representing distinct colony morphology variants. In addition to pigment production, PSE305 and PSE306 differed in phenotypic characteristics including biofilm formation, utilisation of various carbon and nitrogen sources, twitching motility. We found higher levels of expression of genes associated with biofilm formation (pelB) and twitching motility (flgD) in PSE305, compared to the biofilm and twitching-defective PSE306. Comparative genomics analysis revealed single nucleotide polymorphisms (SNPs) and minor insertion/deletion variations between PSE305 and PSE306, including a SNP mutation in the pilP gene of PSE306. By introducing a wild-type pilP gene we were able to partially complement the defective twitching motility of PSE306. There were also three larger regions of difference between the two genomes, indicating genomic instability. Hence, we have demonstrated that P. aeruginosa population divergence can occur during an outbreak of mastitis, leading to significant variations in phenotype and genotype, and resembling the behaviour of P. aeruginosa during chronic biofilm-associated infections.
authors.affiliation: Institute of Infection and Global Health, University of Liverpool, Liverpool L69 7BE, UK.
authors.forename: Elli A
authors.initials: EA
authors.lastname: Wright
authors.affiliation: Laboratorio di Microbiologia Molecolare e Biotecnologia, Dipartimento di Biologia Molecolare, Università di Siena, Siena, Italy.
authors.forename: Valeria
authors.initials: V
authors.lastname: Di Lorenzo
authors.affiliation: Laboratorio di Microbiologia Molecolare e Biotecnologia, Dipartimento di Biologia Molecolare, Università di Siena, Siena, Italy.
authors.forename: Claudia
authors.initials: C
authors.lastname: Trappetti
authors.affiliation: Istituto Zooprofilattico Sperimentale della Sardegna, Italy.
authors.forename: Manuele
authors.initials: M
authors.lastname: Liciardi
authors.affiliation: Dipartimento di Scienze Chirurgiche, Servizio Sequenziamento DNA, Policlinico, Università di Cagliari, Cagliari, Italy.
authors.forename: Germano
authors.initials: G
authors.lastname: Orru
authors.affiliation: Dip. di Biotecnologie Agrarie, Università di Firenze, Firenze, Italy.
authors.forename: Carlo
authors.initials: C
authors.lastname: Viti
authors.affiliation: Institute of Infection and Global Health, University of Liverpool, Liverpool L69 7BE, UK.
authors.forename: Christina
authors.initials: C
authors.lastname: Bronowski
authors.affiliation: Institute of Infection and Global Health, University of Liverpool, Liverpool L69 7BE, UK.
authors.forename: Amanda J
authors.initials: AJ
authors.lastname: Hall
authors.affiliation: Institute of Integrative Biology, University of Liverpool, Liverpool L69 7BE, UK.
authors.forename: Alistair C
authors.initials: AC
authors.lastname: Darby
authors.affiliation: Laboratorio di Microbiologia Molecolare e Biotecnologia, Dipartimento di Biologia Molecolare, Università di Siena, Siena, Italy; UOC Batteriologia, Azienda Ospedaliera Universitaria Senese, Siena, Italy; Department of Genetics, University of Leicester, Leicester LES1 7RH, UK. Electronic address: mro5@leicester.ac.uk.
authors.forename: Marco R
authors.initials: MR
authors.lastname: Oggioni
authors.affiliation: Institute of Infection and Global Health, University of Liverpool, Liverpool L69 7BE, UK. Electronic address: C.Winstanley@liv.ac.uk.
authors.forename: Craig
authors.initials: C
authors.lastname: Winstanley
mesh_terms: D000818:Animals; D015373:Bacterial Typing Techniques; D001483:Base Sequence; D018441:Biofilms / Q000254:growth & development; D004196:Disease Outbreaks; D005260:Female; D014644:Genetic Variation; D005838:Genotype; D007558:Italy; D008413:Mastitis / Q000453:epidemiology / Q000382:microbiology*; D008969:Molecular Sequence Data; D058885:Multilocus Sequence Typing / Q000662:veterinary; D009154:Mutation; D010641:Phenotype; D011552:Pseudomonas Infections / Q000453:epidemiology / Q000382:microbiology*; D011550:Pseudomonas aeruginosa / Q000235:genetics* / Q000254:growth & development / Q000302:isolation & purification; D017422:Sequence Analysis, DNA / Q000662:veterinary; D012756:Sheep / Q000235:genetics*; D012757:Sheep Diseases / Q000453:epidemiology / Q000382:microbiology*
keywords: Biofilm; Diversity; Gene expression; Mastitis; Pseudomonas aeruginosa; Strain divergence