RESUMO
INTRODUCTION: Nocardia spp. are common soil-inhabiting bacteria that frequently infect humans through traumatic injuries or inhalation routes and cause infections, such as actinomycetoma and nocardiosis, respectively. Nocardia brasiliensis is the main aetiological agent of actinomycetoma in various countries. Many bacterial non-coding RNAs are regulators of genes associated with virulence factors. OBJECTIVE: The aim of this work was to identify non-coding RNAs (ncRNAs) expressed during infection conditions and in free-living form (in vitro) in Nocardia brasiliensis. METHODS AND RESULT: The N. brasiliensis transcriptome (predominately < 200 nucleotides) was determined by RNA next-generation sequencing in both conditions. A total of seventy ncRNAs were identified in both conditions. Among these ncRNAs, 18 were differentially expressed, 12 were located within intergenic regions, and 2 were encoded as antisense of 2 different genes. Finally, 10 of these ncRNAs were studied by rapid amplification of cDNA ends and/or quantitative reverse transcription polymerase chain reaction. Interestingly, 3 transcripts corresponded to tRNA-derived fragments (tRNAsCys, Met, Thr), and one transcript was overlapped between an intergenic region and the 5´end of the 23S rRNA. Expression of these last four transcripts was increased during N. brasiliensis infection compared with the in vitro conditions. CONCLUSION: The results of this work suggest a possible role for these transcripts in the regulation of virulence genes in actinomycetoma pathogenesis.
RESUMO
Objetivo. Descubrir la heterogeneidad de la reinfección por Ascaris lumbricoides según grupos de edad, en distintos intervalos, después de un primer tratamiento antihelmíntico masivo. Material y métodos. A partir de datos de la prevalencia e intensidad de la infección por A. lumbricoides obtenidos en un estudio epidemiológico de ascariasis, realizado en Coatzacoalcos, Veracruz, México, se deriva el grado de agregación por medio del método de máxima verosimilitud, asumiendo una distribución binomial negativa del parásito en el huésped. Resultados. Se muestra que la distribución del parásito en el huésped es distinta en el ámbito poblacional que en el de grupos de edad, que la recuperación de la infección no es uniforme; y que la dinámica de asociación huésped-parásito exhibe una marcada desestabilización de su equilibrio endémico después de una primera intervención de masas. Conclusiones. Lo anterior sugiere que existe una alta variabilidad en la agregación entre los distintos grupos de edad y, por tanto, la infección y la reinfección son heterogéneas respecto a la edad. Después de la desestabilización del equilibrio endémico, los estados que alcanza el sistema huésped-parásito son transitorios. Dada la heterogeneidad de la infección, los tratamientos selectivos parecen ser la estrategia más adecuada para disminuirla
Objective. The degree of aggregation is determined for the whole population and for different age-specific strata and is used for assessing the reinfection rate after a mass antihelminthic chemotherapeutic intervention. Material and methods. The degree of aggregation of Ascaris lumbricoides is derived from prevalence and intensity of infection data obtained from an epidemiological study of ascariasis carried out in Coatzacoalcos, Veracruz, México by means of maximum likelihood estimation of the negative binomial distribution. Results. The results show that the distribution of the parasite for the whole population differs from the distribution of the parasite within each age-specific stratum; the reinfection rate is not uniform; the dynamics of the hostparasite association exhibits a clear destabilization of its endemic equilibrium after a first round of mass treatment.Conclusions. It is suggested that the aggregation among the different age-groups is highly variable and hence the infection and reinfection rates are heterogeneous with regard to age; these states of the host-parasite system are transient. Given the heterogeneity of the infection, the selective treatment seems to be the most adequate strategy to diminish helminth infection rates.