Identification of the first blaCMY-2 gene in Salmonella enterica serovar Typhimurium isolates obtained from cases of paediatric diarrhoea illness detected in South America

Nicolás F Cordeiro; Lucía Yim; Laura Betancor; Daniela Cejas; Virginia García-Fulgueiras; María Inés Mota; Gustavo Varela; Leonardo Anzalone; Gabriela Algorta; Gabriel Gutkind; Juan A Ayala; José A Chabalgoity; Rafael Vignoli

doi:10.1016/j.jgar.2013.04.003

Identification of the first bla_CMY-2 gene in Salmonella enterica serovar Typhimurium isolates obtained from cases of paediatric diarrhoea illness detected in South America

J Glob Antimicrob Resist. 2013 Sep;1(3):143-148. doi: 10.1016/j.jgar.2013.04.003. Epub 2013 Jun 1.

Affiliations

¹ Departamento de Bacteriología y Virología, Instituto de Higiene, Facultad de Medicina, Universidad de la República, Alfredo Navarro 3051, CP: 11600 Montevideo, Uruguay.
² Departamento de Desarrollo Biotecnológico, Instituto de Higiene, Facultad de Medicina, Universidad de la República, Alfredo Navarro 3051, CP: 11600 Montevideo, Uruguay.
³ 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.
⁴ Cátedra de Microbiología, Facultad de Farmacia y Bioquímica, Junín 956, CP: 1113 Buenos Aires, Argentina.
⁵ 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.
⁶ Hospital Policial, Sanidad Policial, José Batlle y Ordóñez s/n, CP: 12000 Montevideo, Uruguay.
⁷ Centro de Biología Molecular 'Severo Ochoa', CSIC-UAM, Campus de Cantoblanco, 28049 Madrid, Spain.
⁸ 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.

PMID: 27873624
DOI: 10.1016/j.jgar.2013.04.003

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 bla_CMY-2 genes 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 bla_CMY-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 bla_CMY-2 mRNA levels compared with STM910. Altogether, the results suggest that a plasmid carrying bla_CMY-2 could be disseminating among different clones of S. Typhimurium. Different levels of bla_CMY-2 mRNA could have an effect on the fitness of this micro-organism, resulting in lower invasiveness and motility.

Keywords: CMY-2; Fitness; Salmonella.