McCracken J.P.,Harvard University |
Schwartz J.,Harvard University |
Diaz A.,University of the Valley of Guatemala |
Bruce N.,University of Liverpool |
Smith K.R.,University of California at Berkeley
PLoS ONE | Year: 2013
Household air pollution (HAP) due to solid fuel use is a major public health threat in low-income countries. Most health effects are thought to be related to exposure to the fine particulate matter (PM) component of HAP, but it is currently impractical to measure personal exposure to PM in large studies. Carbon monoxide (CO) has been shown in cross-sectional analyses to be a reliable surrogate for particles<2.5 μm in diameter (PM2.5) in kitchens where wood-burning cookfires are a dominant source, but it is unknown whether a similar PM2.5-CO relationship exists for personal exposures longitudinally. We repeatedly measured (216 measures, 116 women) 24-hour personal PM2.5 (median [IQR] = 0.11 [0.05, 0.21] mg/m3) and CO (median [IQR] = 1.18 [0.50, 2.37] mg/m3) among women cooking over open woodfires or chimney woodstoves in Guatemala. Pollution measures were natural-log transformed for analyses. In linear mixed effects models with random subject intercepts, we found that personal CO explained 78% of between-subject variance in personal PM2.5. We did not see a difference in slope by stove type. This work provides evidence that in settings where there is a dominant source of biomass combustion, repeated measures of personal CO can be used as a reliable surrogate for an individual's PM2.5 exposure. This finding has important implications for the feasibility of reliably estimating long-term (months to years) PM2.5 exposure in large-scale epidemiological and intervention studies of HAP. © 2013 McCracken et al.
Muller E.E.,South African National Institute for Communicable Diseases |
Paz-Bailey G.,University of the Valley of Guatemala |
Lewis D.A.,South African National Institute for Communicable Diseases |
Lewis D.A.,University of Witwatersrand |
Lewis D.A.,University of Cape Town
Sexually Transmitted Infections | Year: 2012
Objectives: To determine whether the 23S ribosomal RNA (rRNA) A2058G and A2059G mutations that confer macrolide resistance are present among southern African strains of Treponema pallidum and to determine their subtype distribution. Methods: 117 genital ulcer specimens, collected between March 2005 and April 2010 in South Africa and Lesotho and previously determined to be positive for T pallidum DNA by molecular testing, were retested using a commercial real-time PCR assay. Those specimens that were still positive for T pallidum DNA were screened for the macrolide resistance-encoding point mutations in the 23S rRNA gene using rapid PCR-based restriction digest assays. Molecular characterisation of two variable treponemal genes, arp and tpr, was used to subtype the T pallidum strains. Results: 1 of 100 T pallidum-positive specimens, collected in Lesotho, contained the A2058G macrolide resistance-encoding 23S rRNA gene mutation, whereas the A2059G mutation was absent. It was possible to fully type 97/100 of all T pallidum DNA-positive samples. A total of nine arp repeat sizes, nine tpr patterns and a combined total of 20 subtypes were identified. Overall, the most common subtypes were 14d (32%), followed by 17d (12%), 14a (10%), 14b (8%), 22b (6%) and 14i (5%). Subtypes 14d and 14a were the predominant subtypes in samples from South Africa (43%) and Lesotho (22%), respectively. Conclusions: Macrolide resistance among T pallidum strains appears to be uncommon in southern Africa. Although a high degree of genetic heterogeneity was observed among the strains tested, T pallidum subtype 14d appears to be the predominant circulating strain.
Rolz C.,University of the Valley of Guatemala
Biochemical Engineering Journal | Year: 2016
The juice extracted from sweet sorghum stalks has been previously explored to produce ethanol and also to grow oleaginous yeasts and algae with the objective of producing microbial oil. In this paper we propose a different process route in order to produce ethanol and microbial oil in two consecutive fermentation steps. Ethanol is produced first followed by the growth of oleaginous yeast employing the residual carbon and nitrogen left from the first step. Two yeasts were compared for ethanol production. Trichosporon oleaginosus was cultivated for lipid production. The yeast selection for the first step was the most important factor for achieving a high ethanol yield and the effect of inorganic nitrogen addition was not significant. The remaining sugars consisted of a mixture of sucrose and fructose and no residual glucose was detected in any of the runs. In the second step T. oleaginosus DSM 11815 grew in the pooled juices remaining from the first step for 168 h and produced biomass with 28% lipid content. Glucose showed the highest uptake rate, sucrose was utilized until low glucose values prevailed, and fructose was slowly metabolized and a substantial amount remained. Although the two step process has flexibility in choosing the proper microorganism for each step, it is necessary to look for a rapid fructose uptake strain for both fermentations. © 2016 Elsevier B.V. All rights reserved.
Ruiz-Mercado I.,University of California at Berkeley |
Canuz E.,University of the Valley of Guatemala |
Walker J.L.,University of California at Berkeley |
Smith K.R.,University of California at Berkeley
Biomass and Bioenergy | Year: 2013
The sustained use of cookstoves that are introduced to reduce fuel use or air pollution needs to be objectively monitored to verify the sustainability of these benefits. Quantifying stove adoption requires affordable tools, scalable methods and validated metrics of usage. We quantified the longitudinal patterns of chimney-stove use of 80 households in rural Guatemala, monitored with Stove Use Monitors (SUMs) during 32 months. We counted daily meals and days in use at each monitoring period and defined metrics like the percent stove-days in use (the fraction of days in use from all stoves and days monitored). Using robust Poisson regressions we detected small seasonal variations in stove usage, with peaks in the warm-dry season at 92% stove-days (95%CI: 87%, 97%) and 2.56 average daily meals (95%CI: 2.40, 2.74). With respect to these values, the percent stove-days in use decreased by 3% and 4% during the warm-rainy and cold-dry periods respectively, and the daily meals by 5% and 12% respectively. Cookstove age and household size at baseline did not affect usage. Qualitative indicators of use from recall questionnaires were consistent with SUMs measurements, indicating stable sustained use and questionnaire accuracy. These results reflect optimum conditions for cookstove adoption and for monitoring in thisproject, which may not occur in disseminations undertaken elsewhere. The SUMs measurements suggestthat 90% stove-days is a more realistic best-case for sustained use thanthe 100% often assumed. Half of sample reported continued use of open-cookfires, highlighting the critical need to verify reduction of open-fire practices in stove disseminations. © 2013 Elsevier Ltd.
Barrington C.,University of North Carolina at Chapel Hill |
Wejnert C.,Centers for Disease Control and Prevention |
Guardado M.E.,Tephinet Inc. |
Nieto A.I.,National AIDS Program |
Bailey G.P.,University of the Valley of Guatemala
AIDS and Behavior | Year: 2012
The purpose of this study is to improve understanding of HIV vulnerability and opportunities for HIV prevention within the social networks of male-to female transgender persons in San Salvador, El Salvador. We compare HIV prevalence and behavioral data from a sample of gay-identified men who have sex with men (MSM) (n = 279), heterosexual or bisexual identified MSM (n = 229) and transgender persons (n = 67) recruited using Respondent Driven Sampling. Transgender persons consistently reported higher rates of HIV risk behavior than the rest of the study population and were significantly more likely to be involved in sex work. While transgender persons reported the highest rates of exposure to HIV educational activities they had the lowest levels of HIV-related knowledge. Transgender respondents' social networks were homophilous and efficient at recruiting other transgender persons. Findings suggest that transgender social networks could provide an effective and culturally relevant opportunity for HIV prevention efforts in this vulnerable population © 2011 Springer Science+Business Media, LLC.