Detection of Plasmid-Mediated Resistance against Colistin in Multi-Drug-Resistant Gram-Negative Bacilli Isolated from a Tertiary Hospital

Mario Galindo-Méndez, Humberto Navarrete-Salazar, Reinaldo Pacheco-Vásquez, Devanhí Quintas-de la Paz, Isabel Baltazar-Jiménez, José David Santiago-Luna, Laura Guadarrama-Monroy

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Abstract

The aim of this study was to determine the prevalence of plasmid-mediated colistin resistance mcr-1 to mcr-5 genes among colistin and multi-drug-resistant Gram-negative bacilli strains isolated from patients in a tertiary hospital in Toluca, Mexico. The presence of mcr genes among the 241 strains collected was assessed by PCR. In the case of mcr-carrying E. coli, further PCR tests were performed to determine the presence of blaCTX-M and whether the strains belonged to the O25b-ST131 clone. Conjugation experiments were also carried out to assess the horizontal transmission of colistin resistance. A total of twelve strains (5.0%), of which four were E. coli; four were P. aeruginosa; three were K. pneumoniae, and one E. cloacae, were found to be resistant to colistin. Of these strains, two E. coli isolates were found to carry mcr-1, and Southern blot hybridization demonstrated its presence on an approximately 60 kb plasmid. Both mcr-1-carrying E. coli strains were found to co-express blaCTX-M, belong to the O25b-ST131 clone, and horizontally transmit their colistin resistance. The results of this study confirm the presence of plasmid-mediated colistin resistance in hospitalized patients in Mexico and demonstrated that the multi-drug-resistant O25b-ST131 E. coli clone can acquire mcr genes and transmit such resistance traits to other bacteria.

Original languageEnglish
Article number1996
JournalMicroorganisms
Volume11
Issue number8
DOIs
StatePublished - 1 Aug 2023

Keywords

  • antibiotic resistance
  • CTX-M
  • mcr-1
  • O25b-ST131
  • plasmid-mediated colistin resistance

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