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. 2020 Sep 22:44:e104.
doi: 10.26633/RPSP.2020.104. eCollection 2020.

[National surveillance of clinical isolates of Enterococcus faecalis resistant to linezolid carrying the optrA gene in Colombia, 2014-2019]

[Article in Spanish]
Sandra Yamile Saavedra  1 , Johan Fabian Bernal  2 , Efrain Montilla-Escudero  1 , German Torres  3 , Mabel Karina Rodríguez  1 , Andrea Melissa Hidalgo  1 , María Victoria Ovalle  1 , Sandra Rivera  3 , Enrique Perez-Gutierrez  4 , Carolina Duarte  2
Affiliations

[National surveillance of clinical isolates of Enterococcus faecalis resistant to linezolid carrying the optrA gene in Colombia, 2014-2019]

[Article in Spanish]
Sandra Yamile Saavedra et al. Rev Panam Salud Publica. .

Abstract
in English, Spanish

Objective: To describe the epidemiological, phenotypical and genetic characteristics of clinical isolates carrying the optrA gene identified in antimicrobial resistance surveillance by the laboratory of the National Institute of Health of Colombia.

Methods: Between October 2014 and February 2019, 25 isolates of Enterococcus spp. resistant to linezolid were received. Antimicrobial identification and sensitivity were determined using Vitek 2 and the minimum inhibitory concentration (MIC) to linezolid was established with E-test. The optrA gene was detected by PCR, and the genetic diversity of optrA-positive isolates was tested with Diversilab®. Six isolates were selected to perform whole genome sequencing.

Results: The optrA gene was confirmed in 23/25 isolates of E. faecalis from seven departments in Colombia. The isolates presented a MIC to linezolid between 8 and >256µg/mL. Typing by Diversilab® showed a wide genetic variability. All the isolates analyzed by whole genome sequencing showed the resistance genes fexA, ermB, lsaA, tet(M), tet(L) and dfrG in addition to optrA and were negative for other mechanisms of resistance to linezolid. Three type sequences and three optrA variants were identified: ST16 (optrA-2), ST476 (optrA-5) and ST618 (optrA-6). The genetic environment of the optrA-2 (ST16) isolates presented the impB, fex, optrA segment, associated with plasmid, while in two isolates (optrA-6 and optrA-5) the transferable chromosomal element Tn6674-like was found.

Conclusion: OptrA-positive clinical isolates present a high genetic diversity, with different optrA clones and variants related to two types of structures and different mobile genetic elements.

Objetivo.: Describir las características epidemiológicas, fenotípicas y genéticas de aislamientos clínicos portadores de optrA identificados en la vigilancia de resistencia antimicrobiana por el laboratorio del Instituto Nacional de Salud de Colombia.

Métodos.: Entre octubre de 2014 y febrero 2019, se recibieron 25 aislamientos de Enterococcus spp. resistentes al linezolid. La identificación y sensibilidad antimicrobiana se determinó con Vitek 2 y la concentración inhibitoria mínima (CIM) al linezolid se estableció con E-test. El gen optrA se detectó mediante PCR. La diversidad genética de aislamientos positivos para optrA se analizó con Diversilab®. Se seleccionaron seis aislamientos para llevar a cabo la secuenciación del genoma completo.

Resultados.: Se confirmó el gen optrA en 23/25 aislamientos de E. faecalis de siete departamentos de Colombia. Los aislamientos presentaron una CIM al linezolid entre 8 y >256µg/mL. La tipificación por Diversilab® indicó una amplia variabilidad genética. Todos los aislamientos analizados mediante secuenciación del genoma completo, presentaron genes de resistencia fexA, ermB, lsaA, tet(M), tet(L) y dfrG además de optrA y fueron negativos para otros mecanismos de resistencia al linezolid. Se identificaron tres secuencias tipos y tres variantes de optrA: ST16 (optrA-2), ST476 (optrA-5) y ST618 (optrA-6). El entorno genético de los aislamientos optrA-2 (ST16) presentó el segmento impB, fex, optrA, asociado a plásmido, mientras que en dos aislamientos (optrA-6 y optrA-5) se encontró el elemento cromosómico transferible Tn6674-like.

Conclusión.: Los aislamientos clínicos positivos para optrA presentan una alta diversidad genética, con diferentes clones y variantes de optrA relacionados con dos tipos de estructuras y diferentes elementos genéticos móviles.

Keywords: Colombia; Enterococcus faecalis; drug resistance, microbial; linezolid.

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Figures

FIGURA 1.
FIGURA 1.. Dendrograma, imagen del gel virtual y matriz de similitud de aislamientos de Enterococcus faecalis positivos para optrA, tipificados con Diversilab®
FIGURA 2.
FIGURA 2.. Representación esquemática de ambiente genético del gen optrA. Las flechas indican la dirección de la transcripción. a. Representación esquemática de aislamientos portadores de optrA-2 comparados con la cepa pS7316 (LC499744). b. Representación esquemática de aislamientos portadores de optrA-5 y optrA-6, comparados con la plataforma Tn6674 del aislamiento TZ2 (MH225421).
FIGURA 3.
FIGURA 3.. Árbol filogenético de aislamientos de E. faecalis portadores del gen optrA basados en los datos de secuenciación del genoma completo, datos demográficos y concentración inhibitoria mínima al linezolid del aislamiento
See this image and copyright information in PMC

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