Brief report
Detection of a cfr-positive MRSA CC398 strain in a pig farmer in SpainDetección de una cepa SARM del linaje CC398 y portadora del gen cfr en un granjero de cerdos en España

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Abstract

Objective

To characterize one linezolid- and methicillin-resistant Staphylococcus aureus (MRSA) isolate recovered from a nasal sample of a pig farmer patient.

Methods

The detection of linezolid resistance mechanisms was performed by PCR and sequencing. The antimicrobial resistance and virulence profile was investigated, and the molecular typing was performed by molecular techniques. The transference of cfr gene was assessed by conjugation experiments and its genetic environment was investigated by specific PCRs.

Results

The linezolid-resistant MRSA isolate was typed as t011-ST398/CC398-SCCmecV-agrI and carried the cfr gene. The isolate was multidrug-resistant but lacked the virulence genes studied. The cfr gene was co-located with the fexA gene on a Tn558 variant and was successfully transferred by conjugation.

Conclusion

We report the first description of LA-MRSA-CC398 carrying the cfr gene in Spain. This finding highlights the importance of surveillance programmes to determine the presence and spread of the cfr gene in the livestock and clinical settings.

Resumen

Objetivo

Caracterizar una cepa Staphylococcus aureus resistente a meticilina (SARM) y a linezolid aislada de una muestra nasal de un paciente granjero de cerdos.

Métodos

Mediante PCR y secuenciación se investigaron los mecanismos de resistencia a linezolid. Se determinó el perfil de resistencia a antimicrobianos y el perfil de virulencia, y se llevó a cabo el tipado molecular mediante diferentes técnicas moleculares. Se estudió la transferibilidad del gen cfr por conjugación y su entorno genético mediante PCR específicas.

Resultados

El aislado fue tipado como t011-ST398/CC398-SCCmecV-agrI y portaba el gen cfr. Presentó un feno/genotipo de multirresistencia, pero carecía de los genes de virulencia estudiados. Se detectó el gen cfr junto con fexA en una variante del Tn558 y se transfirió mediante conjugación.

Conclusión

Se describe el primer aislado SARM-CC398 cfr-positivo en España. Esto destaca la importancia de implementar programas de vigilancia para determinar su presencia y dispersión en el ámbito clínico y ganadero.

Introduction

Staphylococcus aureus clonal complex CC398 is the most common genetic lineage of livestock-associated (LA) methicillin-resistant S. aureus (MRSA) in Europe. Pigs are the main host of MRSA-CC398, however, its detection in humans is increasing in recent years either as colonizer or as causative agent of infection.1

Besides methicillin resistance, MRSA-CC398 usually exhibits a multiresistance phenotype which limits the therapeutic options. In this context, linezolid is an important antimicrobial agent for the treatment of serious infections caused by Gram-positive bacteria, including MRSA. Point mutations in the domain V of the 23S rRNA, as well as amino acid changes in the ribosomal proteins L3, L4, and L22 are the most common mechanisms of linezolid resistance in staphylococci.2 Moreover, linezolid resistance mediated by acquired resistance genes is of concern due to they are often located on mobile genetic elements, which can move between bacteria by horizontal gene transfer. To date, three transferable linezolid resistance genes have been described in staphylococcal species: cfr, optrA, and poxtA.3, 4, 5 Furthermore, these genes also confer reduced susceptibility to other antimicrobial agents, such as phenicols.2

In this study, we report, as far as we know, the first description of MRSA-CC398 harbouring the cfr gene in Spain, recovered from a nasal sample of a patient with professional contact with pigs.

Section snippets

Methods

A pig farmer was hospitalized in the Intensive Care Unit (ICU) of the Hospital Universitari Arnau de Vilanova (Lleida, Spain) due to a non-infectious disease. Active surveillance for multiresistant bacteria was performed upon ICU admission, and MRSA were isolated from nasal, pharyngeal, and bronchoalveolar lavage samples, that were considered as colonization.

The susceptibility to penicillin, oxacillin, erythromycin, clindamycin, gentamicin, tobramycin, amikacin, minocycline, tetracycline,

Results and discussion

The MRSA isolate was resistant to thirteen of the twenty-three antimicrobial agents tested, including linezolid (MIC 8 mg/L), but remained susceptible to vancomycin and daptomycin. It carried the mecA, blaZ, ant(4′)-Ia, tet(K), tet(M), cfr, and fexA resistance genes and showed the amino acid changes S80F and S84L in GrlA and GyrA proteins, respectively, related to fluoroquinolone resistance (Table 1). The cfr gene, which encodes a rRNA methyltransferase, mediates combined resistance to

Funding

This work was partially supported by project SAF2016-76571-R from the Agencia Estatal de Investigación (AEI) of Spain and the Fondo Europeo de Desarrollo Regional (FEDER) of EU. Laura Ruiz-Ripa has a pre-doctoral fellowship from the Universidad de La Rioja (Spain).

Conflict of interest

The authors declare no conflict of interest.

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