The levels of haplotype diversity within the lineages defined by two single-nucleotide polymorphisms (SNPs) (-13910 C/T and -22018 G/A) associated with human lactase persistence were assessed with four fast-evolving microsatellite loci in 794 chromosomes from Portugal, Italy, Fulbe from Cameroon, São Tomé and Mozambique. Age estimates based on the intraallelic microsatellite variation indicate that the -13910*T allele, which is more tightly associated with lactase persistence, originated in Eurasia before the Neolithic and after the emergence of modern humans outside Africa. We detected significant departures from neutrality for the -13910*T variant in geographically and evolutionary distant populations from southern Europe (Portuguese and Italians) and Africa (Fulbe) by using a neutrality test based on the congruence between the frequency of the allele and the levels of intraallelic variability measured by the number of mutations in adjacent microsatellites. This result supports the role of selection in the evolution of lactase persistence, ruling out possible confounding effects from recombination suppression and population history. Reevaluation of the available evidence on variation of the -13910 and -22018 loci indicates that lactase persistence probably originated from different mutations in Europe and most of Africa, even if 13910*T is not the causal allele, suggesting that selective pressure could have promoted the convergent evolution of the trait. Our study shows that a limited number of microsatellite loci may provide sufficient resolution to reconstruct key aspects of the evolutionary history of lactase persistence, providing an alternative to approaches based on large numbers of SNPs.
The features of Helicobacter pylori antibiotic resistance in Lisbon from 1990 to 1999 were studied. Overall resistance rates to amoxycillin, tetracycline, metronidazole, clarithromycin and ciprofloxacin were 0, 0, 30.6, 19.0 and 9.6%, respectively. The incidence of resistance to clarithromycin was much higher in isolates from children (44.8%) than adults (14.6%). For metronidazole, the contrary was observed (children: 19.0%, adults: 32.3%). Ciprofloxacin-resistant isolates were all from adult patients. Concerning the adult population, the resistance rate to metronidazole showed a slight increase during the decade, while for clarithromycin and ciprofloxacin a significant increase was observed (4.6 to 22.0% and 0 to 20.9%, respectively).
The prevalence of H. pylori infection in the Portuguese pediatric population is still high. Although this study confirmed that the highest acquisition rate occurs at young age, it showed that in high-prevalence populations, older children can also acquire H. pylori infection at a rate similar to that of young children.
The primary resistance rate of H. pylori strains isolated from Portuguese children to the commonly used anti-H. pylori antibiotics used is high. Additionally, the increasing trend of ciprofloxacin-resistant and double-resistant strains may compromise H. pylori eradication in a high-prevalence population.
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