Extended-spectrum beta-lactamase-producing Escherichia coli harbouring sul and mcr-1 genes isolates from fish gut contents in the Mekong Delta, Vietnam

This study investigated the existence of sulfonamides and colistin resistance genes among extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli recovered from fish gut in Vietnam and evaluated the susceptibility patterns of the ESBL-producing E. coli to relevant antimicrobials. A total of 88 ESBL-producing E. coli isolates were analysed for the presence of the ESBLs, sul (1, 2, 3) and mcr (1-3) genes by PCR. Antimicrobial resistance phenotypes of isolates were determined by disc diffusion. Results showed that: (i) A high prevalence of 94·3% of sulfonamide resistance was observed in 88 isolates. Moreover, the existence of 2·3% of ESBL-producing E. coli harbouring mcr-1 gene were detected; (ii) The phylogenetic types A and B1 were most frequent, and the bla_CTX-M group1 and bla_TEM genes encoding ESBL were detected in 47·7% of the isolates; (iii) ESBL-producing E. coli harbouring mcr-1 gene exhibited resistance to 11 antibiotics. The existence of mcr-1 and sul1,2,3 genes and the extremely high level of multiple drug resistance in all ESBL-producing E. coli isolates obtained from sampled fish in Vietnam is a major concern. Therefore, it is imperative to monitor ESBL-producing E. coli in the river waters of Vietnam.

Allergen sensitisation among chronic respiratory diseases in urban and rural areas of the south of Viet Nam

OBJECTIVE

To evaluate the prevalence of and risk factors for allergen sensitisation among patients with chronic respiratory disease (CRD) in southern Viet Nam.

DESIGN

An environmental questionnaire and skin prick tests for airborne and food allergens were administered to patients with CRD, defined as individuals with respiratory symptoms and lung function defects.

RESULTS

Of 610 CRD patients, 56% had chronic obstructive pulmonary disease and 31% were asthma patients; 80% were males. The most frequent sensitisers were dust mites (Dermatophagoides farinae 22%, Blomia tropicalis 19%, D. pteronyssinus 18%) and cockroach droppings (13%). Among study participants, 37% were from rural settings and 36% from urban areas, whereas 27% had migrated from rural to urban areas. Compared with people from rural areas, being born in an urban area was a risk factor for sensitisation to mites (OR 1.56, 95%CI 1.11-2.20, P < 0.02). In multivariate analysis, place of birth remained a risk factor for mite sensitisation. Compared with the native urban population, the risk of mite sensitisation was not significantly different among patients born in rural areas and those migrating to urban areas.

CONCLUSION

Dust mites and cockroach droppings were the most frequent allergens among people with CRD in the south of Viet Nam. Compared with the urban population, being native to a rural area was protective against mite sensitisation, but this effect ceased to be significant after migration from rural to urban areas.

Air-breathing fishes in aquaculture. What can we learn from physiology?

During the past decade, the culture of air-breathing fish species has increased dramatically and is now a significant global source of protein for human consumption. This development has generated a need for specific information on how to maximize growth and minimize the environmental effect of culture systems. Here, the existing data on metabolism in air-breathing fishes are reviewed, with the aim of shedding new light on the oxygen requirements of air-breathing fishes in aquaculture, reaching the conclusion that aquatic oxygenation is much more important than previously assumed. In addition, the possible effects on growth of the recurrent exposure to deep hypoxia and associated elevated concentrations of carbon dioxide, ammonia and nitrite, that occurs in the culture ponds used for air-breathing fishes, are discussed. Where data on air-breathing fishes are simply lacking, data for a few water-breathing species will be reviewed, to put the physiological effects into a growth perspective. It is argued that an understanding of air-breathing fishes' respiratory physiology, including metabolic rate, partitioning of oxygen uptake from air and water in facultative air breathers, the critical oxygen tension, can provide important input for the optimization of culture practices. Given the growing importance of air breathers in aquaculture production, there is an urgent need for further data on these issues.

Low numbers of repeat units in variable number of tandem repeats (VNTR) regions of white spot syndrome virus are correlated with disease outbreaks

White spot syndrome virus (WSSV) is the most important pathogen in shrimp farming systems worldwide including the Mekong Delta, Vietnam. The genome of WSSV is characterized by the presence of two major 'indel regions' found at ORF14/15 and ORF23/24 (WSSV-Thailand) and three regions with variable number tandem repeats (VNTR) located in ORF75, ORF94 and ORF125. In the current study, we investigated whether or not the number of repeat units in the VNTRs correlates with virus outbreak status and/or shrimp farming practice. We analysed 662 WSSV samples from individual WSSV-infected Penaeus monodon shrimp from 104 ponds collected from two important shrimp farming regions of the Mekong Delta: Ca Mau and Bac Lieu. Using this large data set and statistical analysis, we found that for ORF94 and ORF125, the mean number of repeat units (RUs) in VNTRs was significantly lower in disease outbreak ponds than in non-outbreak ponds. Although a higher mean RU number was observed in the improved-extensive system than in the rice-shrimp or semi-intensive systems, these differences were not significant. VNTR sequences are thus not only useful markers for studying WSSV genotypes and populations, but specific VNTR variants also correlate with disease outbreaks in shrimp farming systems.

Population dynamics of shrimps in littoral marine waters of the Mekong Delta, south of Viet Nam

The population dynamics of eight commercial species of shrimp (Haliporoides sibogae, Harpiosquilla harpax, Metapenaeus affinis, Metapenaeus brevicornis, Metapenaeus tenuipes, Parapenaeopsis cultrirostris, Parapenaeopsis gracillima and Parapenaeus maxilipedo) distributed in littoral marine zone of the Mekong Delta were investigated. Length-based stock assessment using FiSAT II software package was used to assess the growth and mortality parameters: Asymptotic size (L8), growth coefficient (K), total (Z) and natural (M) mortality, exploitation rate (E), recruitment pattern, current probability of capture and selectivity of fishing gears. Yield-per-recruit analyses were carried out showing different levels of the exploitation. Results showed that the maximum sustainable yield would be reached for an exploitation rate higher than the current one for each population. However, the size of first capture should be increased for every population. The findings indicated that the current exploitations of shrimp populations distributed in littoral marine zone of the Mekong Delta are under exploitation level for maximum sustainable yield; however, all the shrimp populations are subject to growth over-exploitation.

Biology and population dynamics of the goby Pseudapocryptes elongatus in the coastal mud flat areas of the Mekong Delta, Vietnam

This study describe the reproductive biological characteristics and population parameters of the goby, Pseudapocryptes elongatus (Cuvier, 1816), in the coastal mud flat areas of the Mekong Delta, Vietnam. A total of 1058 specimens was collected from January 2004 to June 2005 and results showed that the breeding season occurred with two spawning peaks in July and October. Length at first maturity (L(m)) was 15.4 and 16.3 cm for females and males, respectively. The batch fecundity estimates ranged from 2,652 to 29,406 hydrated oocytes per ovary in the fish ranging from 12.8 to 22.4 cm TL. Length frequency data of the goby ranging from 9.0 to 24.0 cm TL were analyzed using the FiSAT II software. The von Bertalanffy growth parameters were determined as L8 = 25.9 cm, K = 0.66 year(-1) and t(o) = - 0.26 year(-1). The longevity (t(max)) of the goby was estimated to be 4.55 years. There were two recruitment peaks with very different magnitudes and the means of these two peaks were separated by an interval of 5 months. Length at first capture (L(c)) was 10.05 cm, the instantaneous fishing mortality rate (F = 1.38 year(-1)) and natural mortality rate (M = 1.46 year(-1)) accounted for 49 and 51% of the total mortality (Z = 2.84 year(-1)), respectively. Relative yield-per-recruit and biomass-per-recruit analyses gave E(max) = 0.65, E0.1 = 0.55 and E0.5 = 0.33. Results show that the fish stock is subjected to growth overexploitation.

Prospective case-control study of encephalopathy in children with dengue hemorrhagic fever

We present a prospective case-control study of 27 serologically confirmed dengue hemorrhagic fever (DHF) patients with severe central nervous system symptoms. Dengue associated encephalopathy accounted for 0.5% of 5,400 patients admitted with DHF. The mortality rate among children with encephalopathy was 22%, with the survivors experiencing a complete recovery. Liver enzymes and bilirubin were significantly elevated in the study group. In analysis of the cerebrospinal fluid (CSF), reverse transcriptase-polymerase chain reaction revealed dengue-3-specific RNA in one evaluated case. Dengue-specific immunoglobulin M was detected in CSF in 14 of 22 assessable patients, indicating a localized infection. Magnetic resonance imaging scans showed cerebral edema in the majority of patients, although encephalitis-like changes were less common. There was an equal distribution of primary and secondary infections. On the basis of previous reports and of the findings of our study, DHF probably encompasses an expanding clinical spectrum that infrequently involves encephalitis due to a direct neurotropic effect of dengue virus.

Dioxin levels in adipose tissues of hospitalized women living in the south of Vietnam in 1984-89 with a brief review of their clinical histories

Agent Orange, a phenoxyherbicide consisting of 50% 2,4-D and 50% 2,4,5-T, the latter contaminated in the parts per million range with the highly toxic dioxin, 2,3,7,8-TCDD, was sprayed in the south of Vietnam from 1962 to 1971. The chemicals are of concern because of their potential to be causally involved in cancer, adverse reproductive outcomes, immune deficiency and other illness. Because exposed women would be especially involved in the adverse reproductive outcomes, specifically spontaneous abortions and congenital malformations, as well as developmental deficiencies in children, we elected to conduct a pilot study in Vietnam to determine whether elevated 2,3,7,8-tetrachloro-p-dioxin-(TCDD), the dioxin characteristic of Agent Orange could still be found in some women between one and two decades after exposure, and whether the types of illness characteristic of dioxins was present in women with elevated dioxin levels. We were easily able to find some women with increased TCDD from Agent Orange, A surprisingly high level of dioxins from industrial sources was also found in these women in the south. Much lower levels of all dioxins were found in patients in the north of Vietnam. No obvious relation between elevated dioxins and disease was noted in this pilot study, which is meant to precede epidemiology studies which will test the hypotheses that elevated dioxins in humans may lead to an increase in adverse reproductive outcomes and in rates of certain cancers.