RESUMEN
INTRODUCTION: As an infectious disease, tuberculosis (TB) poses a serious threat to public health. Although amikacin (AMK) is an important antibiotic for the treatment of drug-resistant TB, its resistance mechanisms are not fully understood. METHODS: To investigate the role of Rv3737 gene on AMK drug susceptibility, a Mycobacterium tuberculosis (M.tb) Rv3737 knockout strain (H37Rvâ³Rv3737) and a Mycobacterium smegmatis (M.sm) Rv3737 overexpressing strain (Msm/pMV261-Rv3737) were used to detect their minimal inhibitory concentrations (MICs) in this study. RESULTS: The AMK MICs of Rv3737 knockout and overexpressing strains were 4-fold lower and 2-fold higher than those of the wild-type and empty plasmid strains, respectively. The results of clinical isolates showed that no Rv3737 gene mutation was found to be associated with AMK susceptibility, while the rrs A1401G mutation remained the main mechanism of high level of AMK resistance (MIC>32 µg/ml). There was a positive correlation between Rv3737 mRNA expression level and AMK MIC. In the isolates with low-level AMK resistance (MIC = 4 µg/ml) without rrs A1401G mutation, the expression level of Rv3737 gene was significantly higher than those of susceptible isolates. CONCLUSIONS: In this study, the Rv3737 gene was reported for the first time for its effect on AMK susceptibility in M.tb. Although the rrs A1401G mutation remains the main reason of high-level AMK resistance, high expression of the Rv3737 gene was associated with low-level AMK resistance in clinical isolates.
Asunto(s)
Mycobacterium tuberculosis , Tuberculosis Resistente a Múltiples Medicamentos , Humanos , Amicacina/farmacología , Amicacina/uso terapéutico , Kanamicina/farmacología , Capreomicina/farmacología , Capreomicina/uso terapéutico , Farmacorresistencia Bacteriana Múltiple/genética , Tuberculosis Resistente a Múltiples Medicamentos/tratamiento farmacológico , Mutación , Antituberculosos/farmacología , Antituberculosos/uso terapéutico , Pruebas de Sensibilidad MicrobianaRESUMEN
BACKGROUND: Rv3737 is the sole homologue of multifunctional transporter ThrE in Mycobacterium tuberculosis (Mtb). In this study, we aimed to investigate whether this transporter participates in vitro and in vivo survival of Mtb. METHODS: To characterize the role of Rv3737, we constructed and characterized a Mtb H37RvΔRv3737. This strain was evaluated for altered growth rate and macrophage survival using a cell model of infection. In addition, the comparative analysis was conducted to determine the association between Rv3737 mRNA expression and disease severity in active pulmonary TB patients. RESULTS: The H37RvΔRv3737 strain exhibited significantly slow growth rate compared to H37Rv-WT strain in standard culture medium. Additionally, the survival rate of H37Rv-WT strain in macrophages was 2 folds higher than that of H37RvΔRv3737 at 72 h. A significantly higher level of TNF-α and IL-6 mRNA expression was observed in macrophages infected with H37RvΔRv3737 as compared to H37Rv-WT. Of note, Rv3737 expression was significantly increased in clinical Mtb isolates than H37Rv-WT. The relative expression level of Rv3737 was positively correlated with lung cavity number of TB patients. Similarly, the higher Rv3737 mRNA level resulted in lower C(t) value by Xpert MTB/RIF assay, demonstrating that a positive correlation between Rv3737 expression and bacterial load in TB patients. CONCLUSIONS: Our data takes the lead in demonstrate that the threonine transporter Rv3737 is required for in vitro growth and survival of bacteria inside macrophages. In addition, the expression level of Rv3737 may be associated with bacterial load and disease severity in pulmonary tuberculosis patients.