Pseudomonas aeruginosa in CF and non-CF homes is found predominantly in drains.

BACKGROUND: For patients with cystic fibrosis (CF) Pseudomonas aeruginosa infection is a major contributor to progressive lung disease. While colonizing strains are thought to be primarily environmental, which environments are important in lung colonization is unclear. METHODS: We took 11,674 samples from a broad range of sites over 3-8 visits to homes with (7) and without (8) CF patients. RESULTS: Twenty-eight percent of sampled drains yielded P. aeruginosa at least once, and a general mixed linear model estimated that 6.3% of samples from drains yield P. aeruginosa. This is more than eight times the estimated recovery from any other type of household environment. CONCLUSIONS: These findings implicate drains as important potential sources of P. aeruginosa infection. They suggest that maximizing P. aeruginosa control efforts for drains would reduce exposure with minimal extra burden to CF patients and families.

Utilization of larval and pupal detritus by Aedes aegypti and Aedes albopictus.

The utilization of detritus sources by mosquito larvae during development may significantly affect adult life history traits and mosquito population growth. Many studies have shown invertebrate carcasses to be an important detritus source in larval habitats, but little is known regarding how invertebrate carcasses are utilized by mosquito larvae. We conducted two studies to investigate the rate of detritus consumption and its effect on larval development and life history traits. Overall, we found that Aedes aegypti and Aedes albopictus larvae rapidly consumed larval detritus, while pupal detritus was consumed at a significantly slower rate. We also found that the consumption of larval detritus significantly increased larval survivorship and decreased male development time but did not significantly influence female development time or pupal cephalothorax length for either sex. Our results suggest that the direct consumption of larval detritus can support the production of adults in larval habitats that lack allochthonous detritus inputs or where such organic inputs are insufficient. These studies indicate that different forms of invertebrate detritus are utilized in distinct ways by mosquito larvae, and therefore different forms of invertebrate detritus may have distinct effects on larval development and adult life history traits.

Susceptibility of larval Aedes aegypti and Aedes albopictus (Diptera: Culicidae) to dengue virus.

Mosquitoes vertically transmit many arthropod borne viruses, and as a consequence arboviruses are often present within the larval environment. We tested the hypothesis that Aedes aegypti (L.) and Aedes albopictus (Skuse) larvae were susceptible to dengue virus through two infection methods: exposure to dengue in the larval growth environment via viral supernatant, and exposure to infected tissue culture along with viral supernatant. In addition to investigating for the first time the susceptibility of larval Ae. albopictus to dengue virus, we analyzed the infection rate and viral titer of infected pools of Ae. aegypti when exposed to multiple serotypes of dengue. We found that both Ae. aegypti and Ae. albopictus larvae were susceptible to the three dengue virus serotypes to which they were exposed regardless of the exposure method and that there were significant differences between the serotypes in infection titer and infection rate. The finding that larval Ae. aegypti and Ae. albopictus are susceptible to dengue indicates that dengue might be able to spread among larvae within the larval habitat potentially contributing to the persistence of dengue in the environment.

Contribution of individual random mutations to genotype-by-environment interactions in Escherichia coli.

Numerous studies have shown genotype-by-environment (GxE) interactions for traits related to organismal fitness. However, the genetic architecture of the interaction is usually unknown because these studies used genotypes that differ from one another by many unknown mutations. These mutations were also present as standing variation in populations and hence had been subject to prior selection. Based on such studies, it is therefore impossible to say what fraction of new, random mutations contributes to GxE interactions. In this study, we measured the fitness in four environments of 26 genotypes of Escherichia coli, each containing a single random insertion mutation. Fitness was measured relative to their common progenitor, which had evolved on glucose at 37 degrees C for the preceding 10,000 generations. The four assay environments differed in limiting resource and temperature (glucose, 28 degrees C; maltose, 28 degrees C; glucose, 37 degrees C; and maltose, 37 degrees C). A highly significant interaction between mutation and resource was found. In contrast, there was no interaction involving temperature. The resource interaction reflected much higher among mutation variation for fitness in maltose than in glucose. At least 11 mutations (42%) contributed to this GxE interaction through their differential fitness effects across resources. Beneficial mutations are generally thought to be rare but, surprisingly, at least three mutations (12%) significantly improved fitness in maltose, a resource novel to the progenitor. More generally, our findings demonstrate that GxE interactions can be quite common, even for genotypes that differ by only one mutation and in environments differing by only a single factor.