Intrapopulation variability in mutator prevalence among urinary tract infection isolates of Escherichia coli.

Bacteria with elevated mutation rates represent a risk factor for treatment failure and are often found with high frequency in clinical isolates from different sources. How this frequency reflects the among-population and within-population proportion of hypermutators is unknown, despite its importance to the choice of antibiotic therapies that minimize the likelihood of resistance development. Here we screened for hypermutators among the urine of 80 patients with urinary tract infections, at an unprecedented resolution of 24 isolates per sample. We found hypermutators in four patients (5%), at frequencies ranging from 4.2% to 62.5%. Molecular characterization revealed alterations in the oxidized guanine (GO) and methly-directed mistmatch repair (MMR) systems as the genetic basis of hypermutability. These observations suggest that mutators may be present in more patients than previously anticipated, at frequencies that are difficult to detect but still sufficient to impact on adaptation to antibiotics or the host environment.

Characterization of Mycobacterium tuberculosis Beijing isolates from the Mediterranean area.

BACKGROUND: The Beijing lineage of Mycobacterium tuberculosis is causing concern due to its global distribution and its involvement in severe outbreaks. Studies focused on this lineage are mainly restricted to geographical settings where its prevalence is high, whereas those in other areas are scarce. In this study, we analyze Beijing isolates in the Mediterranean area, where this lineage is not prevalent and is mainly associated with immigrant cases. RESULTS: Only 1% (N = 26) of the isolates from two population-based studies in Spain corresponded to Beijing strains, most of which were pan-susceptible and from Peruvian and Ecuadorian patients. Restriction fragment length polymorphism typing with the insertion sequence IS6110 identified three small clusters (2-3 cases). Mycobacterial interspersed repetitive unit-variable number tandem repeat typing (MIRU-15) offered low discriminatory power, requiring the introduction of five additional loci. A selection of the Beijing isolates identified in the Spanish sample, together with a sample of Beijing strains from Italy, to broaden the analysis context in the Mediterranean area, were assayed in an infection model with THP-1 cells. A wide range of intracellular growth rates was observed with only two isolates showing an increased intracellular replication, in both cases associated with contained production of TNF-alpha. No correlation was observed between virulence and the Beijing phylogenetic group, clustered/orphan status, or resistance. The Beijing strain responsible for extensive spread on Gran Canaria Island was also identified in Madrid, but did not lead to secondary cases and did not show high infectivity in the infection model. CONCLUSIONS: The Beijing lineage in our area is a non-homogeneous family, with only certain highly virulent representatives. The specific characterization of Beijing isolates in different settings could help us to accurately identify the virulent representatives before making general assumptions about this lineage.

Transmission permeability of tuberculosis involving immigrants, revealed by a multicentre analysis of clusters.

In recent years, the number of cases of tuberculosis (TB) among immigrants in Spain has increased markedly, and led to this analysis of the recent transmission patterns of TB in the immigrant population in Madrid. The countries from which the highest number of immigrant cases have been reported were Ecuador (21%), Romania (16%), Morocco (12%), Peru (11%) and Bolivia (9%). Fifty-one per cent of the cases were from South America. In a multicentre study (2004-2006), IS6110 restriction fragment length polymorphism and spoligotyping were used to genotype the Mycobacterium tuberculosis isolates from 632 immigrant cases from 47 countries. A total of 183 cases (29%) were grouped into 59 clusters, which are markers of potential transmission events. Most of the clusters (81%) included patients living in different healthcare districts, and 54% of the clusters were multinational. When a sample of 478 autochthonous cases was included, 53% of the clusters involving immigrants also included autochthonous cases. This study revealed marked transmission permeability among nationalities and between the immigrant and the autochthonous populations.

Evaluation of alternatives to RFLP for the analysis of clustered cases of tuberculosis.

BACKGROUND: Mycobacterial interspersed repetitive unit-variable number tandem repeat (MIRU-VNTR) analysis is a recently developed method which could be suitable as a 'real-time' genotyping tool for Mycobacterium tuberculosis. METHODS: One hundred and thirty-four M. tuberculosis isolates were analysed using the reference method, IS6110-restriction fragment length polymorphism (RFLP), and by MIRU, alone and together with spoligotyping. RESULTS: MIRU reduced the genotyping turnaround time by 21 days. The discriminatory power (HGDI) for MIRU and RFLP was 0.978 and 0.989, respectively. RFLP clustered 41.8% of the isolates (17 clusters; 2-9 representatives), whereas MIRU increased the number and size of the clusters (57.5% of the isolates in 20 clusters; 2-14 representatives). With respect to the RFLP clusters, MIRU data showed full correlation in only 7/ 17 (41%) clusters and low correlation in 8/17 (47%) clusters. When MIRU and spoligotyping were considered together, the analysis fitted better with RFLP data: 1) 42.5% of the isolates were grouped in 20 clusters of 2-6 representatives, and 2) the number of clusters with full correlation with RFLP data increased to 11/17 and those with low correlation decreased to 2/17. CONCLUSION: MIRU-VNTR analysis showed low correlation with RFLP. The addition of spoligotyping to MIRU analysis fitted much better with RFLP analysis, although full correlation was still not achieved.