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Association of maternal, obstetric, fetal, and neonatal mortality outcomes with Lady Health Worker coverage from a cross-sectional survey of >10,000 households in Gilgit-Baltistan, Pakistan. PLOS GLOBAL PUBLIC HEALTH 2024; 4:e0002693. [PMID: 38412169 PMCID: PMC10898742 DOI: 10.1371/journal.pgph.0002693] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Accepted: 01/17/2024] [Indexed: 02/29/2024]
Abstract
Pakistan has among the highest rates of maternal, perinatal, and neonatal mortality globally. Many of these deaths are potentially preventable with low-cost, scalable interventions delivered through community-based health worker programs to the most remote communities. We conducted a cross-sectional survey of 10,264 households during the baseline phase of a cluster randomized controlled trial (cRCT) in Gilgit-Baltistan, Pakistan from June-August 2021. The survey was conducted through a stratified, two-stage sampling design with the objective of estimating the neonatal mortality rate (NMR) within the study catchment area, and informing implementation of the cRCT. Study outcomes were self-reported and included neonatal death, stillbirth, health facility delivery, maternal death, postpartum hemorrhage (PPH), and Lady Health Worker (LHW) coverage. Summary statistics (proportions and rates) were weighted according to the sampling design, and mixed-effects Poisson regression was conducted to explore the relationship between LHW coverage and maternal/newborn outcomes. We identified 7,600 women who gave birth in the past five years, among whom 13% reported experiencing PPH. The maternal mortality ratio was 225 maternal deaths per 100,000 live births (95% confidence interval [CI] 137-369). Among 12,376 total births, the stillbirth rate was 41.4 per 1,000 births (95% CI 36.8-46.7) and the perinatal mortality rate was 53.0 per 1,000 births (95% CI 47.6-59.0). Among 11,863 live births, NMR was 16.2 per 1,000 live births (95% CI 13.6-19.3) and 65% were delivered at a health facility. LHW home visits were associated with declines in PPH (risk ratio [RR] 0.89 per each additional visit, 95% CI 0.83-0.96) and late neonatal mortality (RR 0.80, 95% CI 0.67-0.97). Intracluster correlation coefficients were also estimated to inform the planning of future trials. The high rates of maternal, perinatal, and neonatal death in Gilgit-Baltistan continue to fall behind targets of the 2030 Sustainable Development Goals.
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Detection and absolute quantification of Lactiplantibacillus plantarum ATCC 202195 by quantitative real-time PCR. Microbiol Spectr 2024; 12:e0271123. [PMID: 38018977 PMCID: PMC10783133 DOI: 10.1128/spectrum.02711-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Accepted: 10/09/2023] [Indexed: 11/30/2023] Open
Abstract
IMPORTANCE When administered for seven consecutive days shortly after birth, the probiotic bacterium Lactiplantibacillus plantarum ATCC 202195 plus fructooligosaccharide (FOS) was reported to reduce sepsis and lower respiratory tract infection events during early infancy in a randomized trial in India. Since probiotic effects are often strain specific, strain-level detection and quantification by routine molecular methods enables the monitoring of safety outcomes, such as probiotic-associated bacteremia, and allows for the quality of probiotic interventions to be assessed and monitored (i.e., verify strain identity and enumerate). Despite the potential clinical applications of L. plantarum ATCC 202195, an assay to detect and quantify this strain has not previously been described. Herein, we report the design of primer and probe sequences to detect L. plantarum ATCC 202195 and the development and optimization of a real-time PCR assay to detect and quantify the strain with high specificity and high sensitivity.
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An integrated newborn care kit (iNCK) to save newborn lives and improve health outcomes in Gilgit Baltistan (GB), Pakistan: study protocol for a cluster randomized controlled trial. BMC Public Health 2023; 23:2480. [PMID: 38082395 PMCID: PMC10714624 DOI: 10.1186/s12889-023-17322-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Accepted: 11/23/2023] [Indexed: 12/18/2023] Open
Abstract
BACKGROUND Ongoing high neonatal mortality rates (NMRs) represent a global challenge. In 2021, of the 5 million deaths reported worldwide for children under five years of age, 47% were newborns. Pakistan has one of the five highest national NMRs in the world, with an estimated 39 neonatal deaths per 1,000 live births. Reducing newborn deaths requires sustainable, evidence-based, and cost-effective interventions that can be integrated within existing community healthcare infrastructure across regions with high NMR. METHODS This pragmatic, community-based, parallel-arm, open-label, cluster randomized controlled trial aims to estimate the effect of Lady Health Workers (LHWs) providing an integrated newborn care kit (iNCK) with educational instructions to pregnant women in their third trimester, compared to the local standard of care in Gilgit-Baltistan, Pakistan, on neonatal mortality and other newborn and maternal health outcomes. The iNCK contains a clean birth kit, 4% chlorhexidine topical gel, sunflower oil emollient, a ThermoSpot™ temperature monitoring sticker, a fleece blanket, a click-to-heat reusable warmer, three 200 μg misoprostol tablets, and a pictorial instruction guide and diary. LHWs are also provided with a handheld scale to weigh the newborn. The primary study outcome is neonatal mortality, defined as a newborn death in the first 28 days of life. DISCUSSION This study will generate policy-relevant knowledge on the effectiveness of integrating evidence-based maternal and newborn interventions and delivering them directly to pregnant women via existing community health infrastructure, for reducing neonatal mortality and morbidity, in a remote, mountainous area with a high NMR. TRIAL REGISTRATION NCT04798833, March 15, 2021.
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Associations between human milk oligosaccharides and infant growth in a Bangladeshi mother-infant cohort. Pediatr Res 2023:10.1038/s41390-023-02927-1. [PMID: 38052861 DOI: 10.1038/s41390-023-02927-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Revised: 11/01/2023] [Accepted: 11/14/2023] [Indexed: 12/07/2023]
Abstract
BACKGROUND We aimed to estimate associations between human milk oligosaccharides (HMOs) and infant growth (length-for-age (LAZ) and weight-for-length (WLZ) z-scores) at 12 months postnatal age. METHODS In this secondary analysis of data from a maternal vitamin D trial in Dhaka, Bangladesh (N = 192), absolute concentrations of HMOs were measured in 13 ± 1 week(s) postpartum milk samples, infant anthropometric measurements were obtained soon after birth and at 12 months postpartum, and infant feeding was classified during 6 months postpartum. Associations between individual HMOs or HMO groups and LAZ or WLZ were estimated by multivariable linear regression adjusting for infant feeding pattern, maternal secretor status, and other potential confounders. RESULTS The concentrations of 6'sialyllactose, lacto-N-neotetraose, and the non-fucosylated non-sialylated HMOs were inversely associated with LAZ at 12 months of age, whereas the fucosylated non-sialylated HMO concentration was positively associated with LAZ at 12 months. These associations were robust in analyses restricted to infants who were primarily exclusively/predominantly fed human milk during the first 3 (or 6) months. CONCLUSIONS Since HMOs are both positively and negatively associated with postnatal growth, there is a need for randomized trials to estimate the causal benefits and risks of exogenously administered HMOs on infant growth and other health outcomes. IMPACT 6'sialyllactose, lacto-N-neotetraose, and the non-fucosylated non-sialylated human milk oligosaccharides (HMOs) were inversely associated with length-for-age z-scores (LAZ) at 12 months, whereas the fucosylated non-sialylated HMO concentration was positively associated with LAZ at 12 months among Bangladeshi infants. Associations between individual and grouped HMOs with infant length growth at 12 months were as strong or stronger in analyses restricted to infants who were exclusively or predominantly fed human milk up to 3 (or 6) months. Randomized trials are needed to characterize the effects of specific HMOs on infant growth, particularly in countries where postnatal linear growth faltering is common.
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A Bayesian adaptive design for clinical trials of rare efficacy outcomes with multiple definitions. Clin Trials 2022; 19:613-622. [PMID: 36408565 DOI: 10.1177/17407745221118366] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
INTRODUCTION Bayesian adaptive designs for clinical trials have gained popularity in the recent years due to the flexibility and efficiency that they offer. We consider the scenario where the outcome of interest comprises events with relatively low risk of occurrence and different case definitions resulting in varying control group risk assumptions. This is a scenario that occurs frequently for infectious diseases in global health research. METHODS We propose a Bayesian adaptive design that incorporates different case definitions of the outcome of interest that vary in stringency. A set of stopping rules are proposed where superiority and futility may be concluded with respect to different outcome definitions and therefore maintain a realistic probability of stopping in trials with low event rates. Through a simulation study, a variety of stopping rules and design configurations are compared. RESULTS The simulation results are provided in an interactive web application that allows the user to explore and compare the design operating characteristics for a variety of assumptions and design parameters with respect to different outcome definitions. The results for select simulation scenarios are provided in the article. DISCUSSION Bayesian adaptive designs offer the potential for maximizing the information learned from the data collected through clinical trials. The proposed design enables monitoring and utilizing multiple composite outcomes based on rare events to optimize the trial design operating characteristics.
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Pretravel plans and discrepant trip experiences among travelers attending a tertiary care centre family travel medicine clinic. PLoS One 2022; 17:e0262075. [PMID: 35113872 PMCID: PMC8812894 DOI: 10.1371/journal.pone.0262075] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Accepted: 12/18/2021] [Indexed: 11/19/2022] Open
Abstract
Background International travel can expose travelers to a number of health risks. Pretravel consultation (PC) helps mitigate risk and prepare travelers for health concerns that might arise. The assessment of risk, mitigation strategies, and relevance of pretravel advice is dependent on how closely travelers adhere to their planned travel itinerary and activities. We determined the proportion of returned travelers whose completed travel experiences differed from their stated travel itineraries, and identified discrepancies that significantly altered the traveler’s health risk and would have required alternative counseling during their PC. Methods We conducted a prospective cohort study at the SickKids’ Family Travel Clinic between October 2014 and November 2015. Returned travelers who completed a post-travel survey were included. Pretravel consultation assessments and post-trip surveys were compared to identify discrepant trip experiences. Results A total of 389 travelers presented to the clinic for a PC during the study period and 302 (77.6%) were enrolled. Post-travel surveys were received from 119 (39.4%) participants, representing 101 unique itineraries. The median participant age was 36.3 years (IQR 26.6–47.5) and there were 73 female travelers (61%). Most participants (n = 87,73%) were healthy as well as Canadian born (n = 84, 71%). A quarter of travelers were visiting friends and relatives (VFR) (n = 30, 25.2%). The vast majority of returned travelers (n = 109, 92%) reported discrepant trip experiences involving trip duration, countries visited, accommodations, environmental surroundings and/or activities. Almost two thirds of these individuals (n = 68, 62%) would have required alternative pretravel counseling. We did not identify any demographic or planned trip characteristics that predicted discrepant trip experiences requiring alternative pretravel counseling. Conclusions The majority of travelers reported discrepant trip experiences and the discrepancies often affected health risk. Therefore, clinicians should consider providing broader counselling during the PC as discrepancies from planned travel are common.
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The Human-Milk Oligosaccharide Profile of Lactating Women in Dhaka, Bangladesh. Curr Dev Nutr 2021; 5:nzab137. [PMID: 34993388 PMCID: PMC8728024 DOI: 10.1093/cdn/nzab137] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Revised: 10/29/2021] [Accepted: 11/04/2021] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Human-milk oligosaccharides (HMOs) are an abundant component of human milk that have health-related effects on breastfeeding infants. Since variation in HMO composition can be explained by maternal and environmental factors, understanding the diversity in HMOs across settings and identifying context-specific factors associated with HMO abundances is important. OBJECTIVES The aim was to describe the HMO profile of Bangladeshi women and to estimate the effect of maternal vitamin D supplementation on HMO composition. METHODS In a cross-sectional analysis of data and samples from the Maternal Vitamin D for Infant Growth trial in Dhaka, Bangladesh (clinicaltrials.gov; NCT01924013), 192 participants were randomly selected including 96 from each of the placebo and highest-dose vitamin D supplementation groups. In mid-feed breast milk samples collected at a mean (±SD) postpartum age of 93 ± 7 d, absolute and relative abundances of 19 HMOs were analyzed by HPLC. "Secretors" were defined as participants with 2'fucosyllactose concentrations >350 nmol/mL. Associations between HMO concentrations and selected maternal or environmental factors were estimated by multivariable linear regression, adjusting for vitamin D group allocation and secretor status. HMO profiles of Bangladeshi women were compared with data from other international cohorts. RESULTS Overall, 34% (65/192) of participants were nonsecretors. Secretor status was associated with the concentrations of total HMOs and 79% (15/19) of individual HMOs. Vitamin D supplementation did not affect the total or individual concentration of any measured HMO. 3-Fucosyllactose concentration was significantly higher in breast milk samples collected in December to February compared with samples collected in March to May. HMO composition was similar to other previously reported cohorts. CONCLUSIONS The HMO profile of Bangladeshi women is predominantly determined by secretor status. Context-specific HMO data may improve understanding of the effects of HMOs on the infant microbiome and health and guide the development of HMO-containing interventions.
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Micronutrient supplements can promote disruptive protozoan and fungal communities in the developing infant gut. Nat Commun 2021; 12:6729. [PMID: 34795270 PMCID: PMC8602372 DOI: 10.1038/s41467-021-27010-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Accepted: 11/01/2021] [Indexed: 11/14/2022] Open
Abstract
Supplementation with micronutrients, including vitamins, iron and zinc, is a key strategy to alleviate child malnutrition. However, association of gastrointestinal disorders with iron has led to ongoing debate over their administration. To better understand their impact on gut microbiota, we analyse the bacterial, protozoal, fungal and helminth communities of stool samples collected from a subset of 80 children at 12 and 24 months of age, previously enrolled into a large cluster randomized controlled trial of micronutrient supplementation in Pakistan (ClinicalTrials.gov identifier NCT00705445). We show that while bacterial diversity is reduced in supplemented children, vitamins and iron (as well as residence in a rural setting) may promote colonization with distinct protozoa and mucormycetes, whereas the addition of zinc appears to ameliorate this effect. We suggest that the risks and benefits of micronutrient interventions may depend on eukaryotic communities, potentially exacerbated by exposure to a rural setting. Larger studies are needed to evaluate the clinical significance of these findings and their impact on health outcomes.
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Antimicrobial susceptibilities and comparative whole genome analysis of two isolates of the probiotic bacterium Lactiplantibacillus plantarum, strain ATCC 202195. Sci Rep 2021; 11:15893. [PMID: 34354117 PMCID: PMC8342526 DOI: 10.1038/s41598-021-94997-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Accepted: 07/13/2021] [Indexed: 12/24/2022] Open
Abstract
A synbiotic containing Lactiplantibacillus plantarum [American Type Culture Collection (ATCC) strain identifier 202195] and fructooligosaccharide was reported to reduce the risk of sepsis in young infants in rural India. Here, the whole genome of two isolates of L. plantarum ATCC 202195, which were deposited to the ATCC approximately 20 years apart, were sequenced and analyzed to verify their taxonomic and strain-level identities, identify potential antimicrobial resistant genes and virulence factors, and identify genetic characteristics that may explain the observed clinical effects of L. plantarum ATCC 202195. Minimum inhibitory concentrations for selected antimicrobial agents were determined using broth dilution and gradient strip diffusion techniques. The two L. plantarum ATCC 202195 isolates were genetically identical with only three high-quality single nucleotides polymorphisms identified, and with an average nucleotide identity of 99.99%. In contrast to previously published reports, this study determined that each isolate contained two putative plasmids. No concerning acquired or transferable antimicrobial resistance genes or virulence factors were identified. Both isolates were sensitive to several clinically important antibiotics including penicillin, ampicillin and gentamicin, but resistant to vancomycin. Genes involved in stress response, cellular adhesion, carbohydrate metabolism and vitamin biosynthesis are consistent with features of probiotic organisms.
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Effects of Maternal Vitamin D Supplementation During Pregnancy and Lactation on Infant Acute Respiratory Infections: Follow-up of a Randomized Trial in Bangladesh. J Pediatric Infect Dis Soc 2021; 10:901-909. [PMID: 34213544 PMCID: PMC8557369 DOI: 10.1093/jpids/piab032] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Accepted: 04/29/2021] [Indexed: 11/25/2022]
Abstract
BACKGROUND We examined the effect of maternal vitamin D supplementation during pregnancy and lactation on risk of acute respiratory infection (ARI) in infants up to 6 months of age in Bangladesh. METHODS This study was nested in a randomized, double-blind, placebo-controlled, 5-arm dose-ranging trial of prenatal and postpartum vitamin D supplementation. One group of women received 0 IU vitamin D per week during pregnancy and for 26 weeks post delivery ("placebo" group), one group received high-dose prenatal vitamin D supplementation of 28 000 IU per week and 26 weeks post delivery, and there were 3 additional dose-ranging groups receiving vitamin D supplementation during pregnancy only (4200, 16 800, and 28 000 IU per week, respectively). Episodes of ARI were identified by active and passive surveillance. The primary outcome was microbiologically confirmed ARI, and the primary analysis compared the high-dose prenatal plus postpartum vitamin D vs placebo groups. RESULTS In total, 1174 mother-infant pairs were included. Among infants born to mothers in the placebo group, 98% had a venous umbilical cord 25(OH)D level below 30 nmol/L compared with none in the high-dose prenatal plus postdelivery vitamin D group. Incidence of microbiologically confirmed ARI in the high-dose prenatal plus postpartum vitamin D (1.21 episodes per 6 person-months; N = 235) and placebo groups (1.07 episodes per 6 person-months; N = 234) was not significantly different (hazard ratio of 1.12 [95% confidence intervals: 0.90-1.40]). There were no differences in the incidence of microbiologically confirmed or clinical ARI, upper, lower, or hospitalized lower respiratory tract infection between high-dose prenatal plus postpartum vitamin D and placebo groups. CONCLUSIONS Despite a high prevalence of maternal baseline vitamin D deficiency and significant effects of maternal vitamin D supplementation on infant vitamin D status, the intervention did not reduce the risk of microbiologically confirmed ARI in infants up to 6 months of age.
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Abstract
Background In 2018, Pakistan had the world’s highest neonatal mortality rate. Within Pakistan, most neonatal deaths occur in rural areas where access to health facilities is limited, and robust vital registration systems are lacking. To improve newborn survival, there is a need to better understand the causes of neonatal death in high burden settings and engage caregivers in the promotion of newborn health. Objective To describe the causes of neonatal death in a rural area in Pakistan and to estimate the effect of an integrated neonatal care kit (iNCK) on cause-specific neonatal mortality. Methods We analyzed data from a community-based, cluster-randomized controlled trial of 5286 neonates in Rahim Yar Khan (RYK), Punjab, Pakistan between April 2014 and August 2015. In intervention clusters, Lady Health Workers (LHW) delivered the iNCK and education on its use to pregnant women while control clusters received the local standard of care. The iNCK included interventions to prevent and identify signs of infection, identify low birthweight (LBW), and identify and manage hypothermia. Verbal autopsies were attempted for all deaths. The primary outcome was cause-specific neonatal mortality. Results Verbal autopsies were conducted for 84 (57%) of the 147 reported neonatal deaths. The leading causes of death were infection (44%), intrapartum-related complications (26%) and prematurity/LBW (20%). There were no significant differences in neonatal mortality due to prematurity/LBW (RR 0.43; 95% CI 0.15–1.24), infection (RR 1.10; 95% CI 0.58–2.10) or intrapartum-related complications (RR 1.04; 95% CI 0.0.45–2.41) among neonates who died in the intervention arm compared to those who died in the control arm. Conclusion The major causes of neonatal deaths in RYK, Pakistan mirror the global landscape of neonatal deaths. The iNCK did not significantly reduce any cause-specific neonatal mortality.
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Adherence to recommendations at a Canadian tertiary care Family Travel Clinic - A single centre analysis. Travel Med Infect Dis 2020; 34:101579. [PMID: 32074482 DOI: 10.1016/j.tmaid.2020.101579] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Revised: 01/27/2020] [Accepted: 02/08/2020] [Indexed: 12/16/2022]
Abstract
BACKGROUND Infectious and non-infectious risks associated with international travel can be reduced with adherence to pre-travel advice from practitioners trained in travel medicine. METHODS A prospective cohort study was conducted in a tertiary care children's hospital to assess adherence to malaria chemoprophylaxis, safe water and food consumption, mosquito bite protection, motor vehicle safety and travel vaccines using structured questionnaires. High risk groups assessed included child travelers and those visiting friends and relatives (VFRs). RESULTS In total, 290 participants (133 children and 157 adults) were enrolled and completed at least one study questionnaire. In general, with the exception of vaccines, adherence to recommendations was sub-optimal. Among children and adults, adherence to malaria prophylaxis recommendations was lower in VFRs than in non-VFRs. The proportion of children VFRs (cVFRs) and adult VFRs (aVFRs) who adhered to the following recommendations were malaria chemoprophylaxis (47%, 33%), safe water (71%, 74%) and food recommendations (18%, 6%), insect bite avoidance (21%, 12%), and motor vehicle safety (13%, 11%) respectively. Adherence to recommended vaccines uptake was greater than 90% in all groups. CONCLUSION With the exception of vaccine uptake, sub-optimal adherence levels to travel recommendations was identified in all groups, and in particular VFRs, highlighting the need for proactive discussions around barriers to adherence.
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Effect of Maternal Vitamin D Supplementation During Pregnancy and Lactation on Early Infant Nasal Pneumococcal Carriage in Bangladesh (P10-125-19). Curr Dev Nutr 2019. [DOI: 10.1093/cdn/nzz034.p10-125-19] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Abstract
Objectives
To estimate the dose-dependent effects of maternal vitamin D3 (VD) supplementation during pregnancy and lactation on the risk of first nasal pneumococcal colonization (PnC) and the dynamics of nasal pneumococcal (Pn) carriage in infants from birth to 6 months (mos) of age in Dhaka, Bangladesh.
Methods
Infants born to mothers who received weekly VD doses in one of 4 pre/post-partum dose combinations or placebo as part of the Maternal Vitamin D Supplementation during Pregnancy and Lactation to Prevent Acute Respiratory Illness (MDARI) study, were monitored from 0–6 mos for signs of an acute respiratory infection (ARI). A nasal swab was performed to obtain a sample of nasal epithelial tissue if the infant met pre-set ARI criteria. Nasal PnC was detected by qPCR. The effect of VD on the risk of first observed PnC was estimated by an interval-censored survival model. A multi-state model was used to characterize the dynamics of Pn carriage using transition probabilities of state changes.
Results
Of 1060 infants in MDARI, PnC was observed in 90% during the first 6 mos of life with 69% of swabs being positive (n = 3792). There was no significant difference between any VD group and placebo on the risk of initial nasal PnC (Table 1). Overall, the predicted median time to colonization was 7 weeks. Transitioning between positive and negative episodes was common: among 949 infants who were ever positive, 238 (25%) were observed to revert to negative during the first 6 mos of life, of whom 99 (40%) had at least one additional positive swab. Across all groups, an infant was predicted to spend 69 days negative and 120 days positive during the first 6 mos; yet, no Pn dynamics differed significantly across treatment groups (P >0.05). PnC and Pn dynamics were associated with season of birth, parental education and number of siblings, but were not associated with infant characteristics including anthropometric parameters.
Conclusions
These results do not provide evidence supporting an effect of VD on infants’ risk of first nasal PnC nor the dynamics of carriage in a setting where early infant PnC is highly probable. In contrast to in vitro data that demonstrated that VD promoted immune responses against pneumococcus, the present study does not support the hypothesis that improvements in VD status in early infancy reduces the risk of Pn colonization.
Funding Sources
Bill & Melinda Gates Foundation.
Supporting Tables, Images and/or Graphs
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Human Milk Oligosaccharide Composition of Breast Milk from Lactating Women in Dhaka, Bangladesh (P11-040-19). Curr Dev Nutr 2019. [DOI: 10.1093/cdn/nzz048.p11-040-19] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Abstract
Objectives
We aimed to describe the human milk oligosaccharide (HMO) composition of breast milk from Bangladeshi women, overall and by galactoside 2-alpha-L-fucosyltransferase 2 (FUT 2) secretor status, and to estimate the effect of prenatal and postpartum vitamin D3 supplementation on HMO composition.
Methods
In a sub-study of the Maternal Vitamin D for Infant Growth trial in Dhaka, Bangladesh, we selected 96 participants from the placebo group and 96 who were administered 28,000 IU/week vitamin D3 from 17–24 weeks gestation to 6-months postpartum. Breast milk collected at 13 ± 1 week(s) postpartum were analyzed by high-performance liquid chromatography to determine absolute concentrations, relative abundancies of 19 HMOs and total amount HMOs, summarized using medians (interquartile range (IQR)). Associations between each HMO and selected maternal factors (e.g., age, parity, breastfeeding pattern) were estimated by multiple linear regression, adjusting for vitamin D group.
Results
Total median HMO concentration was 16.8 mmol/mL (IQR 9.5-18.7) overall, but varied by secretor status: 18.0 mmol/mL (IQR 16.9-19.2) in secretors (66%) and 9.2 mmol/mL (IQR 8.9-9.5) in non-secretors (34%). Individual HMO concentrations also varied within secretor groups: 2’FL, the most abundant HMO among secretors, ranged from 1.3 to 15.8 mmol/mL among secretors and LNFP II, most abundant among non-secretors, ranged from 0.02 to 4.3 mmol/mL among non-secretors. Vitamin D3 supplementation did not affect total or individual HMO concentration. Other maternal factors were not significantly associated with secretor status, total or individual HMO concentration; however, breastmilk collected during winter had a significantly higher concentration of 3’FL compared to breastmilk collected during spring. The proportion of secretors in Bangladesh was similar to cohorts in Africa and North America. Relative HMO concentrations within secretor groups were similar to other international cohorts.
Conclusions
The HMO composition of breast milk from Bangladeshi women is predominantly determined by secretor status, similar to other countries worldwide. Further research is required to understand the effect of variations in HMO composition on infant health outcomes.
Funding Sources
The Bill and Melinda Gates Foundation.
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Effect of an integrated neonatal care kit on neonatal health outcomes: a cluster randomised controlled trial in rural Pakistan. BMJ Glob Health 2019; 4:e001393. [PMID: 31179036 PMCID: PMC6528753 DOI: 10.1136/bmjgh-2019-001393] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Revised: 04/01/2019] [Accepted: 04/20/2019] [Indexed: 11/27/2022] Open
Abstract
Introduction In 2016, 2.6 million children died during their first month of life. We assessed the effectiveness of an integrated neonatal care kit (iNCK) on neonatal survival and other health outcomes in rural Pakistan. Methods We conducted a community-based, cluster randomised, pragmatic, open-label, controlled intervention trial in Rahim Yar Khan, Punjab, Pakistan. Clusters, 150 villages and their lady health workers (LHWs), were randomly assigned to deliver the iNCK (intervention) or standard of care (control). In intervention clusters, LHWs delivered the iNCK and education on its use to pregnant women. The iNCK contained a clean birth kit, chlorhexidine, sunflower oil, a continuous temperature monitor (ThermoSpot), a heat reflective blanket and reusable heat pack. LHWs were also given a hand-held scale. The iNCK was implemented primarily by caregivers. The primary outcome was all-cause neonatal mortality. Outcomes are reported at the individual level, adjusted for cluster allocation. Enrolment took place between April 2014 and July 2015 and participant follow-up concluded in August 2015. Results 5451 pregnant women (2663 and 2788 in intervention and control arms, respectively) and their 5286 liveborn newborns (2585 and 2701 in intervention and control arms, respectively) were enrolled. 147 newborn deaths were reported, 65 in the intervention arm (25.4 per 1000 live births) compared with 82 in the control arm (30.6 per 1000 live births). Neonatal mortality was not significantly different between treatment groups (risk ratio 0.83, 95% CI 0.58 – 1.18; p = 0.30). Conclusion Providing co-packaged interventions directly to women did not significantly reduce neonatal mortality. Further research is needed to improve compliance with intended iNCK use.
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Genetic characterization of human metapneumovirus identified through community and facility-based surveillance of infants in Dhaka, Bangladesh. J Med Virol 2018; 91:549-554. [PMID: 30372530 DOI: 10.1002/jmv.25351] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Accepted: 10/16/2018] [Indexed: 11/09/2022]
Abstract
BACKGROUND Acute respiratory infection (ARI) is a leading cause of morbidity and mortality in children in low and middle-income countries. Human metapneumovirus (hMPV) is one of the most common viral etiological agents for ARIs in children. OBJECTIVES In this study, we explored the genotypic diversity and the epidemiology of hMPV among infants in Dhaka, Bangladesh. STUDY DESIGN Between December 2014 and August 2016, a total of 3810 mid-turbinate nasal swab samples were collected from infants (0 to 6 months of age) who met clinical ARI criteria, as a part of a prospective ARI cohort study. hMPV was detected using polymerase chain reaction, and genotyped by sequencing and phylogenetic analysis. RESULTS hMPV was identified in 206 (5.4%) nasal swab specimens. One-tenth of the hMPV-positive swabs (n = 19) were also positive for other respiratory viruses. hMPV activity peaked in January and September in 2015; however, no seasonal pattern of hMPV infection was detected. Phylogenetic analyses of the N and F gene-fragments revealed that the hMPV strains circulating in Dhaka, Bangladesh, belonged to three genotypes: A2b, A2c, and B1. Genotype A (57%) was the predominant hMPV genotype circulating in Bangladesh during the study period. CONCLUSION This study describes both the epidemiology of hMPV infection and its genotypic strain diversity in Dhaka, Bangladesh.
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Abstract
BACKGROUND It is unclear whether maternal vitamin D supplementation during pregnancy and lactation improves fetal and infant growth in regions where vitamin D deficiency is common. METHODS We conducted a randomized, double-blind, placebo-controlled trial in Bangladesh to assess the effects of weekly prenatal vitamin D supplementation (from 17 to 24 weeks of gestation until birth) and postpartum vitamin D supplementation on the primary outcome of infants' length-for-age z scores at 1 year according to World Health Organization (WHO) child growth standards. One group received neither prenatal nor postpartum vitamin D (placebo group). Three groups received prenatal supplementation only, in doses of 4200 IU (prenatal 4200 group), 16,800 IU (prenatal 16,800 group), and 28,000 IU (prenatal 28,000 group). The fifth group received prenatal supplementation as well as 26 weeks of postpartum supplementation in the amount of 28,000 IU (prenatal and postpartum 28,000 group). RESULTS Among 1164 infants assessed at 1 year of age (89.5% of 1300 pregnancies), there were no significant differences across groups in the mean (±SD) length-for-age z scores. Scores were as follows: placebo, -0.93±1.05; prenatal 4200, -1.11±1.12; prenatal 16,800, -0.97±0.97; prenatal 28,000, -1.06±1.07; and prenatal and postpartum 28,000, -0.94±1.00 (P=0.23 for a global test of differences across groups). Other anthropometric measures, birth outcomes, and morbidity did not differ significantly across groups. Vitamin D supplementation had expected effects on maternal and infant serum 25-hydroxyvitamin D and calcium concentrations, maternal urinary calcium excretion, and maternal parathyroid hormone concentrations. There were no significant differences in the frequencies of adverse events across groups, with the exception of a higher rate of possible hypercalciuria among the women receiving the highest dose. CONCLUSIONS In a population with widespread prenatal vitamin D deficiency and fetal and infant growth restriction, maternal vitamin D supplementation from midpregnancy until birth or until 6 months post partum did not improve fetal or infant growth. (Funded by the Bill and Melinda Gates Foundation; ClinicalTrials.gov number, NCT01924013 .).
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Maternal vitamin D supplementation during pregnancy and lactation to prevent acute respiratory infections in infancy in Dhaka, Bangladesh (MDARI trial): protocol for a prospective cohort study nested within a randomized controlled trial. BMC Pregnancy Childbirth 2016; 16:309. [PMID: 27737646 PMCID: PMC5064894 DOI: 10.1186/s12884-016-1103-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Accepted: 10/08/2016] [Indexed: 02/08/2023] Open
Abstract
Background Early infancy is a high-risk period for severe acute respiratory infection (ARI), particularly in low-income countries with resource-limited health systems. Lower respiratory tract infection (LRTI) is commonly preceded by upper respiratory infection (URTI), and often caused by respiratory syncytial virus (RSV), influenza and other common community-acquired viral pathogens. Vitamin D status is a candidate modifiable early-life determinant of the host antiviral immune response and thus may influence the risk of ARI-associated morbidity in high-risk populations. Methods/Design In the Maternal Vitamin D for Infant Growth (MDIG) study in Dhaka, Bangladesh (NCT01924013), 1300 pregnant women are randomized to one of five groups: placebo, 4200 IU/week, 16,800 IU/week, or 28,000 IU/week from 2nd trimester to delivery plus placebo from 0–6 months postpartum; or, 28,000 IU/week prenatal and until 6-months postpartum. In the Maternal Vitamin D for ARI in Infancy (MDARI) sub-study nested within the MDIG trial, trained personnel conduct weekly postnatal home visits to inquire about ARI symptoms and conduct a standardized clinical assessment. Supplementary home visits between surveillance visits are conducted when caregivers make phone notifications of new infant symptoms. Mid-turbinate nasal swab samples are obtained from infants who meet standardized clinical ARI criteria. Specimens are tested by polymerase chain reaction (PCR) for 8 viruses (influenza A/B, parainfluenza 1/2/3, RSV, adenovirus, and human metapneumovirus), and nasal carriage density of Streptococcus pneumoniae. The primary outcome is the incidence rate of microbiologically-positive viral ARI, using incidence rate ratios to estimate between-group differences. We hypothesize that among infants 0–6 months of age, the incidence of microbiologically-confirmed viral ARI will be significantly lower in infants whose mothers received high-dose prenatal/postpartum vitamin D supplements versus placebo. Secondary outcomes include incidence of ARI associated with specific pathogens (influenza A or B, RSV), clinical ARI, and density of pneumococcal carriage. Discussion If shown to reduce the risk of viral ARI in infancy, integration of maternal prenatal/postpartum vitamin D supplementation into antenatal care programs in South Asia may be a feasible primary preventive strategy to reduce the burden of ARI-associated morbidity and mortality in young infants. Trial registration NCT02388516, registered March 9, 2015.
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Effect of provision of an integrated neonatal survival kit and early cognitive stimulation package by community health workers on developmental outcomes of infants in Kwale County, Kenya: study protocol for a cluster randomized trial. BMC Pregnancy Childbirth 2016; 16:265. [PMID: 27608978 PMCID: PMC5016984 DOI: 10.1186/s12884-016-1042-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Accepted: 08/22/2016] [Indexed: 11/21/2022] Open
Abstract
Background Each year, more than 200 million children under the age of 5 years, almost all in low- and middle-income countries (LMICs), fail to achieve their developmental potential. Risk factors for compromised development often coexist and include inadequate cognitive stimulation, poverty, nutritional deficiencies, infection and complications of being born low birthweight and/or premature. Moreover, many of these risk factors are closely associated with newborn morbidity and mortality. As compromised development has significant implications on human capital, inexpensive and scalable interventions are urgently needed to promote neurodevelopment and reduce risk factors for impaired development. Method/Design This cluster randomized trial aims at evaluating the impact of volunteer community health workers delivering either an integrated neonatal survival kit, an early stimulation package, or a combination of both interventions, to pregnant women during their third trimester of pregnancy, compared to the current standard of care in Kwale County, Kenya. The neonatal survival kit comprises a clean delivery kit (sterile blade, cord clamp, clean plastic sheet, surgical gloves and hand soap), sunflower oil emollient, chlorhexidine, ThermoSpotTM, Mylar infant sleeve, and a reusable instant heater. Community health workers are also equipped with a portable hand-held electric scale. The early cognitive stimulation package focuses on enhancing caregiver practices by teaching caregivers three key messages that comprise combining a gentle touch with making eye contact and talking to children, responsive feeding and caregiving, and singing. The primary outcome measure is child development at 12 months of age assessed with the Protocol for Child Monitoring (Infant and Toddler version). The main secondary outcome is newborn mortality. Discussion This study will provide evidence on effectiveness of delivering an innovative neonatal survival kit and/or early stimulation package to pregnant women in Kwale County, Kenya. Study findings will help inform policy on the most appropriate interventions for promoting healthy brain development and reduction of newborn morbidity and mortality in Kenya and other similar settings. Trial registration ClinicalTrial.gov NCT02208960 (August 1, 2014)
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Characteristics and pre-travel preparation of travelers at a Canadian pediatric tertiary care travel clinic: A retrospective analysis. Travel Med Infect Dis 2015; 14:148-54. [PMID: 26705839 DOI: 10.1016/j.tmaid.2015.11.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Revised: 10/05/2015] [Accepted: 11/24/2015] [Indexed: 01/24/2023]
Abstract
BACKGROUND International travelers are susceptible to a wide spectrum of travel related morbidities. Despite rising number of international travelers in Canada, the demographics, risk profiles, and preventative strategies of high-risk traveler groups, including pediatric travelers visiting friends and relatives (VFRs) are not well described. METHODS A descriptive analysis was conducted on pre-travel consultations completed between January 2013 and August 2014 at a large pediatric tertiary care center in Toronto, Canada. Data on demographics, travel characteristics, and pre-travel interventions were extracted from 370 pre-travel consultations. Results were compared between all VFR and non-VFR travelers, as well as between children traveling to visit friends and relatives, for vacation, and for education and/or volunteer purposes. RESULTS Forty-eight percent of consultations were for children <18 years of age (n = 177), of which 31% were for young children (<5 years of age). Young children were more likely to travel to visit friends and/or relatives than for other purposes (29% vs 9%, p < 0.0001). Children VFRs (cVFRs) were more likely to travel for >28 days than children traveling for vacation (43% vs 1%, p < 0.0001), and children traveling for education/volunteer purposes (43% vs 21%, p = 0.03). Around half of cVFRs traveled to destinations in Asia (51%). The majority stayed with locals, friends and/or relatives (85%), and nearly all traveled to urban destinations (98%). The most prescribed interventions for children were azithromycin (84%), Dukoral (66%), and the hepatitis A vaccine (60%). Atovaquone/proguanil was the most commonly prescribed antimalarial for children. CONCLUSION Children that travel to visit friends and relatives represent a unique travel group and may require specific considerations during pre-travel preparations. Our findings can help develop targeted pre-travel strategies for children VFRs.
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36: Characteristics and Risk Profiles of Paediatric International Travelers Visiting Friends and Relatives. Paediatr Child Health 2015. [DOI: 10.1093/pch/20.5.e46] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Epidemiology and clinical management of tuberculosis in children in Canada. Paediatr Child Health 2015; 20:83-8. [PMID: 25838781 PMCID: PMC4373581 DOI: 10.1093/pch/20.2.83] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/16/2014] [Indexed: 11/14/2022] Open
Abstract
Although often regarded as a foreign disease, latent tuberculosis or tuberculosis disease will be encountered in many clinical situations by the Canadian child health practitioner. There are key differences between tuberculosis in children and adults. In the present article, the changing epidemiology of tuberculosis in children in Canada and around the world, the pathogenesis of infection, diagnostic tests, and clinical management of childhood latent tuberculosis and tuberculosis disease are reviewed.
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The community-based delivery of an innovative neonatal kit to save newborn lives in rural Pakistan: design of a cluster randomized trial. BMC Pregnancy Childbirth 2014; 14:315. [PMID: 25201572 PMCID: PMC4177060 DOI: 10.1186/1471-2393-14-315] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Accepted: 09/04/2014] [Indexed: 11/28/2022] Open
Abstract
Background Worldwide, an estimated 2.9 million neonatal deaths occurred in 2012, accounting for 44% of all under-five deaths. In Pakistan, more than 200,000 newborns die annually and neonatal mortality rates are higher than in any other South Asian country and haven’t changed over the last three decades. The high number of neonatal deaths highlights the urgent need for effective and sustainable interventions that target newborn mortality in Pakistan. Method/Design This cluster randomized trial aims at evaluating the impact of delivering an integrated neonatal kit to pregnant women during the third trimester of pregnancy and providing education on how to use the contents (intervention arm) compared to the current standard of care (control arm) in the district of Rahimyar Khan, Punjab province, Pakistan. The kit, which will be distributed through the national Lady Health Worker program, comprises a clean delivery kit (sterile blade, cord clamp, clean plastic sheet, surgical gloves and hand soap), sunflower oil emollient, chlorhexidine, ThermoSpot™, Mylar infant sleeve, and a reusable instant heat pack. Lady health workers will be provided with a standard portable hand-held electric weighing scale. The primary outcome measure is neonatal mortality (death in the first 28 days of life). Discussion While many cost-effective, evidence-based interventions to save newborn lives exist, they are not always accessible nor have they been integrated into a portable kit designed for home-based implementation entirely by caregivers. The implementation of cost-effective, portable, and easy-to-use interventions has tremendous potential for sustainably reducing neonatal mortality and long-term improvements in population health. The bundling of interventions and commodities together also has much potential for cost-effective delivery and maximizing gains from points of contact. This study will provide empirical evidence on the feasibility and effectiveness of the delivery of an innovative neonatal kit to pregnant women in Pakistan. Together, these findings will help inform policy on the most appropriate interventions to improve newborn survival. Trial registration ClinicalTrial.gov NCT02130856. Registered May 1, 2014.
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A Conserved Spiral Structure for Highly Diverged Phage Tail Assembly Chaperones. J Mol Biol 2013; 425:2436-49. [DOI: 10.1016/j.jmb.2013.03.035] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2013] [Revised: 03/06/2013] [Accepted: 03/23/2013] [Indexed: 11/28/2022]
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Tail tip proteins related to bacteriophage λ gpL coordinate an iron-sulfur cluster. J Mol Biol 2013; 425:2450-62. [PMID: 23542343 DOI: 10.1016/j.jmb.2013.03.032] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2013] [Revised: 03/12/2013] [Accepted: 03/23/2013] [Indexed: 01/20/2023]
Abstract
The assembly of long non-contractile phage tails begins with the formation of the tail tip complex (TTC). TTCs are multi-functional protein structures that mediate host cell adsorption and genome injection. The TTC of phage λ is assembled from multiple copies of eight different proteins, including gpL. Purified preparations of gpL and several homologues all displayed a distinct reddish color, suggesting the binding of iron by these proteins. Further characterization of the gpL homologue from phage N15, which was most amenable to in vitro analyses, showed that it contains two domains. The C-terminal domain was demonstrated to coordinate an iron-sulfur cluster, providing the first example of a viral structural protein binding to this type of metal group. We characterized the iron-sulfur cluster using inductively coupled plasma-atomic emission spectroscopy, absorbance spectroscopy, and electron paramagnetic resonance spectroscopy and found that it is an oxygen-sensitive [4Fe-4S](2+) cluster. Four highly conserved cysteine residues were shown to be required for coordinating the iron-sulfur cluster, and substitution of any of these Cys residues with Ser or Ala within the context of λ gpL abolished biological activity. These data imply that the intact iron-sulfur cluster is required for function. The presence of four conserved Cys residues in the C-terminal regions of very diverse gpL homologues suggest that utilization of an iron-sulfur cluster is a widespread feature of non-contractile tailed phages that infect Gram-negative bacteria. In addition, this is the first example of a viral structural protein that binds an iron-sulfur cluster.
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Long noncontractile tail machines of bacteriophages. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 726:115-42. [PMID: 22297512 DOI: 10.1007/978-1-4614-0980-9_6] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
In this chapter, we describe the structure, assembly, function, and evolution of the long, noncontractile tail of the siphophages, which comprise ∼60% of the phages on earth. We place -particular emphasis on features that are conserved among all siphophages, and trace evolutionary connections between these phages and myophages, which possess long contractile tails. The large number of high-resolution structures of tail proteins solved recently coupled to studies of tail-related complexes by electron microscopy have provided many new insights in this area. In addition, the availability of thousands of phage and prophage genome sequences has allowed the delineation of several large families of tail proteins that were previously unrecognized. We also summarize current knowledge pertaining to the mechanisms by which siphophage tails recognize the bacterial cell surface and mediate DNA injection through the cell envelope. We show that phages infecting Gram-positive and Gram-negative bacteria possess distinct families of proteins at their tail tips that are involved in this process. Finally, we speculate on the evolutionary advantages provided by long phage tails.
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The X-ray crystal structure of the phage lambda tail terminator protein reveals the biologically relevant hexameric ring structure and demonstrates a conserved mechanism of tail termination among diverse long-tailed phages. J Mol Biol 2009; 389:938-51. [PMID: 19426744 DOI: 10.1016/j.jmb.2009.04.072] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2009] [Revised: 04/23/2009] [Accepted: 04/28/2009] [Indexed: 01/28/2023]
Abstract
The tail terminator protein (TrP) plays an essential role in phage tail assembly by capping the rapidly polymerizing tail once it has reached its requisite length and serving as the interaction surface for phage heads. Here, we present the 2.7-A crystal structure of a hexameric ring of gpU, the TrP of phage lambda. Using sequence alignment analysis and site-directed mutagenesis, we have shown that this multimeric structure is biologically relevant and we have delineated its functional surfaces. Comparison of the hexameric crystal structure with the solution structure of gpU that we previously solved using NMR spectroscopy shows large structural changes occurring upon multimerization and suggests a mechanism that allows gpU to remain monomeric at high concentrations on its own, yet polymerize readily upon contact with an assembled tail tube. The gpU hexamer displays several flexible loops that play key roles in head and tail binding, implying a role for disorder-to-order transitions in controlling assembly as has been observed with other lambda morphogenetic proteins. Finally, we have found that the hexameric structure of gpU is very similar to the structure of a putative TrP from a contractile phage tail even though it displays no detectable sequence similarity. This finding coupled with further bioinformatic investigations has led us to conclude that the TrPs of non-contractile-tailed phages, such as lambda, are evolutionarily related to those of contractile-tailed phages, such as P2 and Mu, and that all long-tailed phages may utilize a conserved mechanism for tail termination.
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