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Tetanus arises from wound contamination with Clostridium tetani, but approximately one fifth of patients have no discernable entry wound. Clostridium tetani is culturable from animal feces, suggesting the gastrointestinal tract could be an endogenous reservoir or direct-entry portal, but human data are lacking. In this study of 101 Vietnamese adults with tetanus and 29 hospitalized control subjects, admission stool samples were cultured for C. tetani. Anti-tetanus toxin antibodies were measured by ELISA. Clostridium tetani toxigenicity was evaluated using polymerase chain reaction and sequencing. Toxigenic C. tetani was cultured from stool samples in 50 of 100 (50%) tetanus cases and 12 of 28 (42.9%) control subjects (P = 0.50), and stool samples of 44 of 85 (52.4%) tetanus cases with clinically identified wounds compared with 6 of 15 (47.6%) patients without clinically identified wounds (P = 0.28). Nine of 12 (75%) control subjects with toxigenic C. tetani in their stool samples lacked protective antibody concentrations. These findings fail to show evidence of an association between gastrointestinal C. tetani and tetanus infection, but emphasize the importance of increasing vaccination coverage.

Pre-existing colonization with Staphylococcus aureus or Klebsiella pneumoniae has been found to increase the risk of infection in intensive care patients. We previously conducted a longitudinal study to characterize colonization of these two organisms in patients admitted to intensive care in a hospital in southern Vietnam. Here, using genomic and phylogenetic analyses, we aimed to assess the contribution these colonizing organisms made to infections. We found that in the majority of patients infected with S. aureus or K. pneumoniae , the sequence type of the disease-causing (infecting) isolate was identical to that of corresponding colonizing organisms in the respective patient. Further in-depth analysis revealed that in patients infected by S. aureus ST188 and by K. pneumoniae ST17, ST23, ST25 and ST86, the infecting isolate was closely related to and exhibited limited genetic variation relative to pre-infection colonizing isolates. Multidrug-resistant S. aureus ST188 was identified as the predominant agent of colonization and infection. Colonization and infection by K. pneumoniae were characterized by organisms with limited antimicrobial resistance profiles but extensive repertoires of virulence genes. Our findings augment the understanding of the link between bacterial colonization and infection in a low-resource setting, and could facilitate the development of novel evidence-based approaches to prevent and treat infections in high-risk patients in intensive care.

Saltwater intrusion has become a severe issue for the Mekong Delta in Vietnam, especially near the coastline. This issue has led to farmers diversifying from exclusively growing rice to adopting a mixed rice-shrimp system with rice only cultivated in the wet season. However, the nutrient (nitrogen, phosphorus and carbon) cycling and nutrient use efficiency of this system remain poorly understood. To address this knowledge gap, we examined nutrient budgets across 12 farms using integrated rice-shrimp ponds, and in some cases semi-intensive or intensive shrimp grow-out ponds (Penaeus monodon or Penaeus vannamei), over a two-year period (2014–2015). In terms of nutrient budgets, the main nutrient input (92% of the N input, 57% P and 95% C) in the integrated rice-shrimp ponds (IRSPs) came from intake water (excluding C from primary production), while water discharge accounted for the highest output (75% of N output, 41% P, 57% C, excluding C from respiration). The study showed that IRSPs had low dissolved oxygen and high nutrient concentrations which may affect shrimp production. Conversely, salinity levels in the wet season were too high for rice plants thereby affecting rice production. Shrimp survival in the IRSPs was low over the two years (6.3 ± 2.2%), which resulted in the low proportion of nutrients exported from the ponds as harvested shrimp (6% N, 5% P and 10% C). In contrast, the shrimp grow-out ponds (SGOPs), had much higher survival (77.1% for P. vannamei and 59.2% for P. monodon) in three of the six farms where the shrimp survived through to harvest. In these ponds, formulated feed was the highest nutrient input (P. vannamei: 82% N, 75% P and 85% C; P. monodon: 75% N, 55% P and 77% C) with approximately a third of the nutrients being in the shrimp harvest. In our study, nutrients in the IRSPs were used less efficiently than in SGOPs, hence mechanisms to improve shrimp survival and production in IRSPs are urgently needed.

Acute hepatopancreatic necrosis disease (AHPND) is a severe shrimp disease that causes significant losses in the shrimp industry worldwide. In 2013, specific strains of Vibrio parahaemolyticus were found to be responsible for AHPND. Recently, inhibiting the detection of catecholamines has been reported to decrease the virulence of various pathogenic bacteria, including Vibrio anguillarum , Vibrio campbellii and human pathogenic Vibrio parahaemolyticus . Thus, in this study we investigated whether catecholamine sensing has any effect on the virulence of an AHPND-causing V . parahaemolyticus strain isolated from outbreaks in Vietnam. We found that the catecholamines norepinephrine and dopamine (50 μM) increased motility of V . parahaemolyticus ( P V . parahaemolyticus with catecholamines significantly increased its virulence to whiteleg shrimp ( Penaeus vannamei ), and pretreatment with the antagonist LED209 neutralized this effect ( P V . parahaemolyticus to levels that were even higher than those observed in shrimp challenged with untreated V . parahaemolyticus , suggesting that this type of compounds might be useful to decrease losses due to AHPND in shrimp.

Genetic improvement of tiger prawn Penaeus monodon is challenging due to difficulties in breeding and rearing of this species in captive environments. To date, there have been very limited quantitative genetic studies in this species, especially genotype by environment (G × E) interaction between diverse farming systems (e.g., tank vs. pond). Therefore, the present study ran the long-term captive selection program for tiger prawn and obtained an in-depth pedigree of five generations (including base population and first generation) for genetic assessment of the environment impacts on two economically important traits in this species (i.e., survival and body weight at harvest). Originally, we evaluated the G × E interaction effect on survival and harvest weight between Biosecure Recirculating System (RAS) at the breeding nucleus and outdoor commercial ponds. Quantitative genetic analysis within mixed model methodology framework was carried out on 57,435 individual prawns (phenotype data from three latest generations, G2-G4) to examine possible effects of rearing environments on genetic parameters (heritability and correlations) for survival and body weight at harvest. The heritability (h2) for body weight was moderate (0.31–0.49) and differed slightly between the three testing environments. There were also significant heritable genetic variations of survival (h2 = 0.37–0.77) across the environments studied. The common full-sib effects accounted for 16 to 21% of total phenotypic variation for body weight and 11 to 18% for survival. Genetic correlations between body weight and survival were positive (0.23–0.46) in this population of tiger prawn. To examine the G × E interaction effect on survival and harvest body weight, the trait expressions in each environment were treated as separate traits and bi-variate models were used to estimate genetic correlations between homologous characters. An important finding of this study was that the between-environment genetic correlations for both body weight and survival were medium to high (0.56–0.70) between outdoor ponds; however, the estimates were low to moderate (0.17–0.31) between indoor RAS in the nucleus and outdoor ponds under field conditions. In summary, the moderate heritability for body weight and survival suggest that long-term response to selection can be achieved in this population of tiger prawn, and that the effects of rearing environments should be taken into consideration when conducting genetic improvement programs for this species, specifically the management of candidate parents to produce the next generation for selection.

The pathogenesis of severe dengue remains unclear, particularly the mechanisms underlying the plasma leakage that results in hypovolaemic shock in a small proportion of individuals. Maximal leakage occurs several days after peak viraemia implicating immunological pathways. Skin is a highly vascular organ and also an important site of immune reactions with a high density of dendritic cells (DCs), macrophages and T cells. We obtained skin biopsies and contemporaneous blood samples from patients within 24 hours of onset of dengue shock syndrome (DSS), and from healthy controls. We analyzed cell subsets by flow cytometry, and soluble mediators and antibodies by ELISA; the percentage of migratory CD1a+ dermal DCs was significantly decreased in the DSS patients, and skin CD8+ T cells were activated, but there was no accumulation of dengue-specific antibodies. Inflammatory monocytic cells were not observed infiltrating the skin of DSS cases on whole-mount histology, although CD14dim cells disappeared from blood.

There is a paucity of data regarding initial bacterial colonization on admission to Intensive Care Units (ICUs) in low and middle-income countries (LMICs). Patients admitted to ICUs in LMICs are at high-risk of subsequent infection with antimicrobial-resistant organisms (AROs). We conducted a prospective, observational study at the Hospital for Tropical Diseases in Ho Chi Minh City, Vietnam from November 2014 to January 2016 to assess the colonization and antimicrobial susceptibility of Staphylococcus aureus, Escherichia coli, Klebsiella spp., Pseudomonas spp. and Acinetobacter spp. among adult patients within 48 hours of ICU admission. We found the admission colonization prevalence (with at least one of the identified organisms) was 93.7% (785/838) and that of AROs was 63.1% (529/838). The colonization frequency with AROs among patients admitted from the community was comparable to those transferred from other hospitals (62.2% vs 63.8%). Staphylococcus aureus was the most commonly isolated bacteria from nasal swabs (13.1%, 110/838) and the methicillin-resistant Staphylococcus aureus nasal colonization prevalence was 8.6% (72/838). We isolated Escherichia coli from rectal swabs from almost all enrolled patients (88.3%, 740/838) and 52.1% (437/838) of patients were colonized by extended spectrum β-lactamase producing Escherichia coli. Notably, Klebsiella pneumoniae was the most frequently isolated bacteria from the tracheal swabs (11.8%, 18/153). Vietnamese ICU patients have a high rate of colonization with AROs and are thus at risk of subsequent infections with these organisms if good infection control practices are not in place.

Data concerning intensive care unit (ICU)-acquired bacterial colonization and infections are scarce from low and middle-income countries (LMICs). ICU patients in these settings are at high risk of becoming colonized and infected with antimicrobial-resistant organisms (AROs). We conducted a prospective observational study at the Ho Chi Minh City Hospital for Tropical Diseases, Vietnam from November 2014 to January 2016 to assess the ICU-acquired colonization and infections, focusing on the five major pathogens in our setting: Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), Klebsiella spp., Pseudomonas spp. and Acinetobacter spp., among adult patients with more than 48 hours of ICU stay. We found that 61.3% (223/364) of ICU patients became colonized with AROs: 44.2% (161/364) with rectal ESBL-producing E. coli and Klebsiella spp.; 30.8% (40/130) with endotracheal carbapenemase-producing Acinetobacter spp.; and 14.3% (52/364) with nasal methicillin-resistant S. aureus. The incidence rate of ICU patients becoming colonized with AROs was 9.8 (223/2,276) per 100 patient days. Significant risk factor for AROs colonization was the Charlson Comorbidity Index score. The proportion of ICU patients with HAIs was 23.4% (85/364), and the incidence rate of ICU patients contracting HAIs was 2.3 (85/3,701) per 100 patient days. The vascular catheterization (central venous, arterial and hemofiltration catheter) was significantly associated with hospital-acquired bloodstream infection. Of the 77 patients who developed ICU-acquired infections with one of the five specified bacteria, 44 (57.1%) had prior colonization with the same organism. Vietnamese ICU patients have a high colonization rate with AROs and a high risk of subsequent infections. Future research should focus on monitoring colonization and the development of preventive measures that may halt spread of AROs in ICU settings.

Two fresh-food maturation diets were tested on wild Penaeus monodon broodstock during a period of 1 month in primary quarantine and 3 months in secondary quarantine; diet A was composed of 70.30% squid (Photololigo sp.), 7.66% marine worm (polychaetes), 7.94% oyster (Crassostrea sp.), and 14.10% pork liver and diet B was composed of 37.39% squid, 16.50% marine worm, 27.14% oyster, and 18.98% pork liver; all on a dry-weight basis. The formulation of diet B was to resemble the ratios of ARA/EPA, DHA/EPA, and n-3/n-6 fatty acids of mature ovaries of wild P. monodon. At the start of primary quarantine, the average weight of the shrimps allocated to the two diets was not significantly different (129.71 ± 2.96 g for females and 87.88 ± 2.49 g for males in the group of diet A and 131.74 ± 1.75 g for females and 88.95 ± 2.05 g for males in the group of diet B). After secondary quarantine, the growth rate of the female shrimps receiving diet B was significantly greater (P < 0.05) than the female shrimps fed diet A (24.44b ± 4.98% compared to 12.89a ± 3.24%, respectively). Shrimp fed diet B performed better than shrimp fed diet A in terms of spawning frequency (85% versus 57%) and fecundity (458,796a ± 35,658 and 245,718b ± 34,736 eggs/spawn, respectively), but number of spawns, hatching rate, fertilization rate and metamorphosis rate of the nauplii into zoea did not differ between the treatments (P > 0.05). The success of diet B in terms of spawning frequency, fecundity, fertilization rate and hatching rate indicates the importance of the ARA/EPA and DHA/EPA ratios in broodstock nutrition of black tiger shrimp. This study also confirmed the success of natural mating of P. monodon in small tanks (1.25 m2 bottom area). The two-step biosecure quarantine procedure was applicable for producing SPF shrimp.

N-acyl homoserine lactone molecules (AHL) are quorum sensing molecules known to be involved in the production of virulence factors. In this study, N-acyl homoserine lactone (AHL)-degrading enrichment cultures (ECs) as bio-control agent in prawn larviculture was investigated. Enrichment cultures EC5(D) and EC5(L), originating from microbial communities of the fish gut of Dicentrarchus labrax L. and Lates calcarifer, were tested in the larval rearing of Macrobrachium rosenbergii through their addition to the rearing water and by bio-encapsulation in Artemia nauplii. The ECs were grown at the expense of glycerol released in the medium by hatching Artemia. The larval stage index of AHL-exposed larvae was 4.06 ± 0.07 in Experiment 1 and 6.18 ± 0.10 in Experiment 2 and 5.04 ± 0.07 and 6.50 ± 0.08 in the control treatment, respectively. Furthermore, a distinct difference in survival between AHL-exposed larvae (37.3% ± 10.6 and 64.5% ± 2.0) versus non-exposed larvae (77.7% ± 5.6 and 76.8% ± 3.2 in Experiments 1 and 2, respectively) was observed. Both ECs were effective in improving prawn larvae survival under experimental conditions, i.e. when the survival of prawn larvae was compromised through a daily exposure to AHL molecules (1 mg l− 1). Through the addition of ECs, the negative effect of AHL could be counteracted, especially obtaining better larval quality, indicated by ammonia tolerance. These experiments demonstrated that AHL at a concentration of 1 mg l− 1 could have a negative effect on prawn larvae, presumably through their effect on the prevailing opportunistic pathogenic microorganisms, while the selected ECs can counteract this. For this reason, using N-acyl homoserine lactone-degrading microbial communities might be a useful tool in prawn larviculture.

Acinetobacter baumannii has become one of the major infection threats in intensive care units (ICUs) globally. Since 2008, A. baumannii has been the leading cause of ventilator-associated pneumonia (VAP) in our ICU at an infectious disease hospital in southern Vietnam. The emergence of this pathogen in our setting is consistent with the persistence of a specific clone exhibiting resistance to carbapenems. Antimicrobial combinations may be a strategy to treat infections caused by these carbapenem-resistant A. baumannii. Therefore, we assessed potential antimicrobial combinations against local carbapenem-resistant A. baumannii by measuring in vitro interactions of colistin with four antimicrobials that are locally certified for treating VAP. We first performed antimicrobial susceptibility testing and multilocus variable number tandem repeat analysis (MLVA) genotyping on 74 A. baumannii isolated from quantitative tracheal aspirates from patients with VAP over an 18-month period. These 74 isolates could be subdivided into 21 main clusters by MLVA and >80 % were resistant to carbapenems. We selected 56 representative isolates for in vitro combination synergy testing. Synergy was observed in four (7 %), seven (13 %), 20 (36 %) and 38 (68 %) isolates with combinations of colistin with ceftazidime, ceftriaxone, imipenem and meropenem, respectively. Notably, more carbapenem-resistant A. baumannii isolates (36/43; 84 %) exhibited synergistic activity with a combination of colistin and meropenem than carbapenem-susceptible A. baumannii isolates (2/13; 15 %) (P = 0.023; Fisher's exact test). Our findings suggest that combinations of colistin and meropenem should be considered when treating carbapenem-resistant A. baumannii infections in Vietnam, and we advocate clinical trials investigating combination therapy for VAP.

Ventilator-associated pneumonia (VAP) is a serious healthcare-associated infection that affects up to 30 % of intubated and mechanically ventilated patients in intensive care units (ICUs) worldwide. The bacterial aetiology and corresponding antimicrobial susceptibility of VAP is highly variable, and can differ between countries, national provinces and even between different wards in the same hospital. We aimed to understand and document changes in the causative agents of VAP and their antimicrobial susceptibility profiles retrospectively over an 11 year period in a major infectious disease hospital in southern Vietnam. Our analysis outlined a significant shift from Pseudomonas aeruginosa to Acinetobacter spp. as the most prevalent bacteria isolated from quantitative tracheal aspirates in patients with VAP in this setting. Antimicrobial resistance was common across all bacterial species and we found a marked proportional annual increase in carbapenem-resistant Acinetobacter spp. over a 3 year period from 2008 (annual trend; odds ratio 1.656, P = 0.010). We further investigated the possible emergence of a carbapenem-resistant Acinetobacter baumannii clone by multiple-locus variable number tandem repeat analysis, finding a bla OXA-23-positive strain that was associated with an upsurge in the isolation of this pathogen. We additionally identified a single bla NDM-1-positive A. baumannii isolate. This work highlights the emergence of a carbapenem-resistant clone of A. baumannii and a worrying trend of antimicrobial resistance in the ICU of the Hospital for Tropical Diseases in Ho Chi Minh City, Vietnam.

Sixteen female crossbred (localxAnglo-Nubian) goats raised from 20-30kg were fed a basal diet of cassava chips, cotton seed cake, rice bran and rice straw, where 0, 30, 40 or 50% of the diet dry matter was replaced with leaves from Gliricidia maculata. All the diets containing Gliricidia resulted in a higher intake than the diet without Gliricidia, but the diet with 30% Gliricidia gave the best intake and the highest growth rate, 105g per day. Total intake was 2.8% of the body weight (BW). Five male goats of the same breed and size were used to study the effect of supplementing rice straw with different levels of Gliricidia leaves on intake and apparent digestibility of the diets. Increasing the amount of Gliricidia leaves decreased the rice straw intake but increased intake of total dry matter (DM), organic matter (OM), neutral detergent fibre (NDF), acid detergent fibre (ADF) and crude protein (CP). Supplementing with Gliricidia leaves improved the dry matter digestibility (DMD), the OM digestibility and the CP digestibility in the mixed Gliricidia and rice straw diet, compared to pure rice straw, but the values were somewhat lower than could be expected by calculations from the pure rice straw and Gliricidia diets. The DMD of Gliricidia was 64.1%.

The International Center for Living Aquatic Resources Management (ICLARM), in collaboration with its partner organizations, has developed an improved strain of Nile tilapia (known as the GIFT strain) which shows superior performance in terms of growth and survival in on‐station conditions. The on‐station performance of the GIFT strain may, however, not be replicated in actual farm conditions. Before disseminating the GIFT strain, its performance and nature were evaluated in on‐farm conditions relative to the strains already being cultivated. This paper analyses the comparative performance of the GIFT strain on an average as well as on an efficient farm and assesses its nature in five Asian countries (i.e., Bangladesh, China, the Philippines, Thailand and Vietnam). Ordinary least squares regression and tobit models are estimated on the average weight at harvest and on the survival rate, respectively, to assess the comparative performance of the GIFT strain on an average farm. Stochastic frontier f...

White spot disease (WSD) is a viral disease of shrimp caused by white spot syndrome virus (WSSV). Stocking WSSV-infected seed has been implicated as a major risk factor for outbreaks of WSD. In addition, the quality of postlarvae batches has been proposed as a predictor for good crops. This paper describes the relationship between indicators of quality and WSSV in postlarvae (PL) of Penaeus monodon from Karnataka, India, over the period September 1999 to January 2000. Three outcome variables were considered: the WSSV status of the PL, as determined by PCR, and 2 subjective assessments of PL quality, namely the activity of the PL and the quality of the PL as determined by research assistants and farmers, respectively. Of the 73 batches of PL, 49.3% from a random sample of farms tested positive for WSSV. After adjusting for confounding, stocking earlier in the growing season and duration of transportation were the main risk factors for the presence of WSSV. The quality assessed by farmers and the PL activity assessed by research assistants showed only fair agreement (kappa 0.252) reaffirming the subjective nature of such techniques. The only variables consistently associated with either assessment of quality in univariate analysis were PL length, number per bag and salinity of the water in the delivery bags. After adjusting for confounding, no single variable was consistently associated with PL quality and activity. The research assistants' assessment of PL activity was also associated with the hatchery and a brown-orange hepatopancreas in univariate analysis. After adjusting for confounding, a brown-orange hepatopancreas was still significant and fitted into the model together with the salinity of the water in the PL bags. The farmers' assessment of quality was associated with PL length, date of stocking and duration of transportation in both univariate and multivariable analyses. There was no relationship between quality assessment and WSSV in PCR-positive PL.