title: Identification of the first blaCMY-2gene in Salmonella enterica serovar Typhimurium isolates obtained from cases of paediatric diarrhoea illness detected in South America.
abstract: The objectives of this study were to investigate clinical isolates of Salmonella enterica serovar Typhimurium resistant to β-lactam antibiotics, to characterise their mechanisms of antibiotic resistance and to evaluate the possible biological cost of expressing resistance genes. Two oxyimino-cephalosporin-resistant Salmonella isolates obtained from children with diarrhoea were characterised. The occurrence of plasmid-encoded blaCMY-2genes was confirmed by molecular methods and conjugation assays; transcription levels were determined by quantitative real-time PCR (qRT-PCR). The genomic context of the β-lactamases, replicon type and addiction systems were analysed by PCR. Genomic relatedness of both isolates was studied by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) assays. Growth curves, motility and invasiveness assays in Caco-2 cells were performed to analyse the bacterial fitness of both isolates. Both isolates carried a blaCMY-2-like allele in an IncI plasmid and belonged to the same MLST sequence type (ST19); nevertheless, they showed extensive differences in their PFGE profiles and virulotypes. Isolate STM709 appeared to lack the Salmonella virulence plasmid and displayed less motility and invasiveness in cultured cells than isolate STM910. qRT-PCR showed that isolate STM709 had higher blaCMY-2mRNA levels compared with STM910. Altogether, the results suggest that a plasmid carrying blaCMY-2could be disseminating among different clones of S. Typhimurium. Different levels of blaCMY-2mRNA could have an effect on the fitness of this micro-organism, resulting in lower invasiveness and motility.
authors.affiliation: Departamento de Bacteriología y Virología, Instituto de Higiene, Facultad de Medicina, Universidad de la República, Alfredo Navarro 3051, CP: 11600 Montevideo, Uruguay.
authors.forename: Nicolás F
authors.initials: NF
authors.lastname: Cordeiro
authors.affiliation: Departamento de Desarrollo Biotecnológico, Instituto de Higiene, Facultad de Medicina, Universidad de la República, Alfredo Navarro 3051, CP: 11600 Montevideo, Uruguay.
authors.forename: Lucía
authors.initials: L
authors.lastname: Yim
authors.affiliation: Departamento de Bacteriología y Virología, Instituto de Higiene, Facultad de Medicina, Universidad de la República, Alfredo Navarro 3051, CP: 11600 Montevideo, Uruguay; Departamento de Desarrollo Biotecnológico, Instituto de Higiene, Facultad de Medicina, Universidad de la República, Alfredo Navarro 3051, CP: 11600 Montevideo, Uruguay.
authors.forename: Laura
authors.initials: L
authors.lastname: Betancor
authors.affiliation: Cátedra de Microbiología, Facultad de Farmacia y Bioquímica, Junín 956, CP: 1113 Buenos Aires, Argentina.
authors.forename: Daniela
authors.initials: D
authors.lastname: Cejas
authors.affiliation: Departamento de Bacteriología y Virología, Instituto de Higiene, Facultad de Medicina, Universidad de la República, Alfredo Navarro 3051, CP: 11600 Montevideo, Uruguay.
authors.forename: Virginia
authors.initials: V
authors.lastname: García-Fulgueiras
authors.affiliation: Departamento de Bacteriología y Virología, Instituto de Higiene, Facultad de Medicina, Universidad de la República, Alfredo Navarro 3051, CP: 11600 Montevideo, Uruguay; Laboratorio Central del Hospital Pereira Rossell - Ministerio de Salud Pública, Br. Artigas 1550, CP: 11600 Montevideo, Uruguay.
authors.forename: María Inés
authors.initials: MI
authors.lastname: Mota
authors.affiliation: Departamento de Bacteriología y Virología, Instituto de Higiene, Facultad de Medicina, Universidad de la República, Alfredo Navarro 3051, CP: 11600 Montevideo, Uruguay.
authors.forename: Gustavo
authors.initials: G
authors.lastname: Varela
authors.affiliation: Hospital Policial, Sanidad Policial, José Batlle y Ordóñez s/n, CP: 12000 Montevideo, Uruguay.
authors.forename: Leonardo
authors.initials: L
authors.lastname: Anzalone
authors.affiliation: Departamento de Bacteriología y Virología, Instituto de Higiene, Facultad de Medicina, Universidad de la República, Alfredo Navarro 3051, CP: 11600 Montevideo, Uruguay; Laboratorio Central del Hospital Pereira Rossell - Ministerio de Salud Pública, Br. Artigas 1550, CP: 11600 Montevideo, Uruguay.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Algorta
authors.affiliation: Cátedra de Microbiología, Facultad de Farmacia y Bioquímica, Junín 956, CP: 1113 Buenos Aires, Argentina.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Gutkind
authors.affiliation: Centro de Biología Molecular 'Severo Ochoa', CSIC-UAM, Campus de Cantoblanco, 28049 Madrid, Spain.
authors.forename: Juan A
authors.initials: JA
authors.lastname: Ayala
authors.affiliation: Departamento de Desarrollo Biotecnológico, Instituto de Higiene, Facultad de Medicina, Universidad de la República, Alfredo Navarro 3051, CP: 11600 Montevideo, Uruguay.
authors.forename: José A
authors.initials: JA
authors.lastname: Chabalgoity
authors.affiliation: Departamento de Bacteriología y Virología, Instituto de Higiene, Facultad de Medicina, Universidad de la República, Alfredo Navarro 3051, CP: 11600 Montevideo, Uruguay. Electronic address: rvignoli@higiene.edu.uy.
authors.forename: Rafael
authors.initials: R
authors.lastname: Vignoli
keywords: CMY-2; Fitness; Salmonella