title: Assessing the intra-species genetic variability in the clonal pathogen Campylobacter fetus: CRISPRs are highly polymorphic DNA markers.
abstract: Campylobacter fetus is a Gram-negative, microaerophilic bacterium that infects animals and humans. The subspecies Campylobacter fetus subsp. fetus (Cff) affects a broad range of vertebrate hosts and induces abortion in cows and sheep. Campylobacter fetus subsp. venerealis (Cfv) is restricted to cattle and causes the endemic disease bovine genital campylobacteriosis, which triggers reproductive problems and is responsible for major economic losses. Campylobacter fetus subsp. testudinum (Cft) has been isolated mostly from apparently healthy reptiles belonging to different species but also from ill snakes and humans. Genotypic differentiation of Cff and Cfv is difficult, and epidemiological information is scarce because there are few methods to study the genetic diversity of the strains. We analyze the efficacy of MLST, ribosomal sequences (23S gene and internal spacer region), and CRISPRs to assess the genetic variability of C. fetus in bovine and human isolates. Sequences retrieved from complete genomes were included in the analysis for comparative purposes. MLST and ribosomal sequences had scarce or null variability, while the CRISPR-cas system structure and the sequence of CRISPR1 locus showed remarkable diversity. None of the sequences here analyzed provided evidence of a genetic differentiation of Cff and Cfv in bovine isolates. Comparison of bovine and human isolates with Cft strains showed a striking divergence. Inter-host differences raise the possibility of determining the original host of human infections using CRISPR sequences. CRISPRs are the most variable sequences analyzed in C. fetus so far, and constitute excellent representatives of a dynamic fraction of the genome. CRISPR typing is a promising tool to characterize isolates and to track the source and transmission route of C. fetus infections.
authors.affiliation: Sección Genética Evolutiva, Facultad de Ciencias, Universidad de la República, Iguá 4225, 11400 Montevideo, Uruguay. Electronic address: calleros@fcien.edu.uy.
authors.forename: Lucía
authors.initials: L
authors.lastname: Calleros
authors.affiliation: Departamento de Bacteriología y Virología, Instituto de Higiene, Facultad de Medicina, Universidad de la República, Dr. Alfredo Navarro 3051, 11600 Montevideo, Uruguay. Electronic address: laurabet@higiene.edu.uy.
authors.forename: Laura
authors.initials: L
authors.lastname: Betancor
authors.affiliation: Sección Genética Evolutiva, Facultad de Ciencias, Universidad de la República, Iguá 4225, 11400 Montevideo, Uruguay; Unidad de Bioinformática, Institut Pasteur Montevideo, Mataojo 2020, 11400 Montevideo, Uruguay. Electronic address: giraola@pasteur.edu.uy.
authors.forename: Gregorio
authors.initials: G
authors.lastname: Iraola
authors.affiliation: Laboratorio de Bacteriología, Unidad Integrada INTA-Universidad Nacional de Mar del Plata, Ruta 226 km. 76.5, Balcarce 7620, Argentina. Electronic address: mendez.maria@inta.gob.ar.
authors.forename: Alejandra
authors.initials: A
authors.lastname: Méndez
authors.affiliation: Laboratorio de Bacteriología, Unidad Integrada INTA-Universidad Nacional de Mar del Plata, Ruta 226 km. 76.5, Balcarce 7620, Argentina. Electronic address: morsella.claudia@inta.gob.ar.
authors.forename: Claudia
authors.initials: C
authors.lastname: Morsella
authors.affiliation: Laboratorio de Bacteriología, Unidad Integrada INTA-Universidad Nacional de Mar del Plata, Ruta 226 km. 76.5, Balcarce 7620, Argentina. Electronic address: paolicchi.fernando@inta.gob.ar.
authors.forename: Fernando
authors.initials: F
authors.lastname: Paolicchi
authors.affiliation: División de Laboratorios Veterinarios, Ministerio de Ganadería Agricultura y Pesca, Ruta 8 Brig. Gral. J. A. Lavalleja Km. 17.500, Montevideo, 12000, Uruguay. Electronic address: silwabal@gmail.com.
authors.forename: Silvia
authors.initials: S
authors.lastname: Silveyra
authors.affiliation: Laboratorio de Bacteriología, Unidad Integrada INTA-Universidad Nacional de Mar del Plata, Ruta 226 km. 76.5, Balcarce 7620, Argentina. Electronic address: velilla.alejandra@inta.gob.ar.
authors.forename: Alejandra
authors.initials: A
authors.lastname: Velilla
authors.affiliation: Sección Genética Evolutiva, Facultad de Ciencias, Universidad de la República, Iguá 4225, 11400 Montevideo, Uruguay. Electronic address: rperez@fcien.edu.uy.
authors.forename: Ruben
authors.initials: R
authors.lastname: Pérez
mesh_terms: D000818:Animals; D015373:Bacterial Typing Techniques; D002168:Campylobacter fetus / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification; D002417:Cattle; D002418:Cattle Diseases / Q000175:diagnosis / Q000382:microbiology; D064112:Clustered Regularly Interspaced Short Palindromic Repeats / Q000235:genetics*; D003141:Communicable Diseases / Q000175:diagnosis / Q000382:microbiology; D004269:DNA, Bacterial / Q000235:genetics; D056426:Genetic Loci; D005819:Genetic Markers; D014644:Genetic Variation; D006801:Humans; D058885:Multilocus Sequence Typing; D012338:RNA, Ribosomal, 23S / Q000235:genetics; D017422:Sequence Analysis, DNA; D013045:Species Specificity
chemical_list: D004269:DNA, Bacterial; D005819:Genetic Markers; D012338:RNA, Ribosomal, 23S
keywords: CRISPR; Campylobacter fetus; Genetic variability