[Show abstract][Hide abstract] ABSTRACT: Background / Purpose:
To investigate the relationship between fitness and drug resistance.
Heterogeneity in fitness is a function of the drug resistance mutations and the strain genetic background.
34th Congress of the European Society of Mycobacteriology 2013; 08/2013
[Show abstract][Hide abstract] ABSTRACT: Spoligotyping has shown Mycobacterium tuberculosis strains to be composed of different lineages and some of them are not just geographically restricted but also affect specific ethnic populations and are associated with outbreaks and drug resistance. We recently described a particular subtype within the Latin American-Mediterranean family, called RD(Rio), widespread in Brazil. Moreover, recent data also indicate that RD(Rio) is present in many countries in all continents and are associated with cavitary disease and multi-drug resistance (MDR). To further explore the relationship between RD(Rio) and MDR, we conducted a study in a TB reference center responsible for care of MDR patients in Rio Grande do Sul, the most southern Brazilian state. From a collection of 237 clinical isolates, RD(Rio) alone was responsible for half of all MDR cases, including one large group composed by strains with identical IS6110-RFLP and having the LAM 5 signature. We additionally had complete data records of 96 patients and could compare with the presence or not of RD(Rio). No difference in clinical, radiological or laboratorial features was observed but significant more cases with MDR was described in patients infected with a RD(Rio) strain (p= 0.0015). Altogether, RD(Rio) was responsible for 38% of all TB cases. These data support and confirmed previous findings that RD(Rio) is the main responsible for TB in Brazil and is associated with drug resistance. Considering that RD(Rio) is a globally distributed genotype, such findings raise concern about the increase in MDR in certain human population.
Journal of clinical microbiology 01/2013; · 4.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: When bacteria develop drug-resistant mutations, there is often an associated biological cost; however, some strains can exhibit low- or no-cost mutations. In the present study, a quantitative resazurin reduction assay was used to measure the biological cost of Mycobacterium tuberculosis isolates that contained different mutations in the rpsL, rrs, rpoB, and katG genes, and showed different resistance profiles. Biological costs were determined by comparing the growth curves of drug-resistant isolates with drug-susceptible strains. Some strains, such as those with rpoB mutations other than S531L and strains with mutations in all of the studied genes, grew more slowly than did drug-susceptible strains. However, some strains grew more quickly than drug-susceptible strains, such as those that had only the rpsL K43R mutation. Strains with the mutation katG S315T presented heterogeneous biological costs. When analyzed individually, strains with the mutations rpsL43/katG315, rpoB531, and rpoB531/katG315 grew faster than drug-susceptible strains. The results suggest that some strains with the most common mutations correlated to a high resistance toward streptomycin, isoniazid and rifampicin can grow as well as or better than susceptible strains.
[Show abstract][Hide abstract] ABSTRACT: A major threat to tuberculosis (TB) control programs is the emergence of drug resistant Mycobacterium tuberculosis strains that cause TB that cannot be cured by standard anti-TB drug regimens. Because few data exist on MDR-TB in this region of the country, we performed an epidemiologic study that combined conventional and molecular analysis of MDR-TB cases from Rio Grande do Sul (RS) that were diagnosed in this period and included cases that were under treatment with second line drug schemes. Included were 121 MDR cases and sequencing of rpoB and katG showed that 106 (87.6%) strains were mutated in rpoB and 97 (80.2%) in katG. Spoligotyping demonstrated that the LAM genotype was predominant (n = 70, 57.8%) and included the largest group composed by 22 (18.1%) strains with the LAM5 ST93 genotype. Other main genotypes belonged to the families T (n = 22, 18.2%), U family (n = 16, 13.2%), Haarlem (n = 5, 4.1%) and X (n = 1, 0.8%). Genotyping by IS6110-RFLP analysis showed 51 distinct fingerprints, 38 (31.4%) of these observed only once and the other 13 patterns being shared among the rest of the isolates (n = 83, 68.6%). Among the 22 strains that were LAM5 ST93, only two had different IS6110-RFLP genotypes. In conclusion, there exists a high degree of M. Tuberculosis genotype clustering among MDR-TB cases in Rio Grande do Sul. Moreover, we observed a large MDR-TB outbreak.
[Show abstract][Hide abstract] ABSTRACT: Mutations related to streptomycin resistance in the rpsL and rrs genes are well known and can explain about 70% of this phenotypic resistance. Recently, the gidB gene was found to be associated with low-level streptomycin resistance in Mycobacterium tuberculosis. Mutations in gidB have been reported with high frequency, and this gene appears to be very polymorphic, with frameshift and point mutations occurring in streptomycin-susceptible and streptomycin-resistant strains. In this study, mutations in gidB appeared in 27% of streptomycin-resistant strains that contained no mutations in the rpsL or rrs genes, and they were associated with low-level streptomycin resistance. However, the association of certain mutations in gidB with streptomycin resistance needs to be further investigated, as we also found mutations in gidB in streptomycin-susceptible strains. This occurred only when the strain was resistant to rifampin and isoniazid. Two specific mutations appeared very frequently in this and other studies of streptomycin-susceptible and -resistant strains; these mutations were not considered related to streptomycin resistance, but as a polymorphism. We stratified the strains according to the different phylogenetic lineages and showed that the gidB(16) polymorphism (16G allele) was exclusively present in the Latin American-Mediterranean (LAM) genotype, while the gidB(92) polymorphism (92C allele) was associated with the Beijing lineage in another population. In the sample studied, the two characterized single-nucleotide polymorphisms could distinguish LAM and Beijing lineages from the other lineages.
Journal of clinical microbiology 05/2011; 49(7):2625-30. · 4.23 Impact Factor