Dayéri Dianou

Burden of rotavirus and other enteropathogens among children with diarrhea in Burkina Faso

OBJECTIVE There is limited information available regarding the etiology of gastrointestinal infections in Burkina Faso. The aim of this study was to investigate the prevalence and epidemiology of enteric pathogens causing gastroenteritis in young children, with a focus on rotavirus, and to investigate the levels of malnutrition and other clinical factors in association with the severity of diarrhea. METHODS A prospective study was undertaken from May 2009 to March 2010, covering the rainy and dry seasons, at the Saint Camille Medical Center in Ouagadougou, Burkina Faso. A total of 309 children less than 5 years of age with diarrhea were enrolled and examined for rotavirus, bacterial, and parasitic infections, as well as clinico-epidemiological aspects. RESULTS At least one enteropathogen was detected in 57.9% (n=179) of the children. Of these, 32.4% had rotavirus infections, 16.8% bacterial infections (enteropathogenic Escherichia coli 9.7%, Shigella spp 5.8%, and Salmonella spp 2.3%), and 18.8% parasitic infections (Giardia lamblia 11.3%, Trichomonas intestinalis 6.8%, Entamoeba histolytica/dispar 1.3%). During the cold dry period from December 2009 to February 2010, we observed a large increase in diarrhea cases, which was mainly attributed to rotavirus infections, as 63.8% of these diarrhea cases were positive for rotavirus. In contrast, no rotavirus infection was observed during the rainy season (June-September 2009), when the frequency of parasitic infections was high. Rotavirus and parasitic infections were age-related, with rotavirus being more prevalent in young children (<12 months) and parasites more common in older children (>12 months), while bacteria were equally prevalent among all age groups. Rotavirus infections exhibited more severe symptoms compared to bacteria and parasites, and were associated with fever, vomiting, and severe dehydration. Malnutrition, especially acute malnutrition (wasting), was significantly associated with more severe symptoms in rotavirus-induced diarrhea. The undernourished children also exhibited a prolonged duration of diarrheal episodes. CONCLUSION This study demonstrates rotavirus as the main etiological agent in pediatric diarrhea in Burkina Faso, and further shows the great severity of rotavirus-induced diarrhea in undernourished children in Burkina Faso.

Methanoculleus chikugoensis sp. nov., a novel methanogenic archaeon isolated from paddy field soil in Japan, and DNA-DNA hybridization among Methanoculleus species

A strictly anaerobic, irregularly coccoid, methanogenic archaeon, strain MG62T (= JCM 10825T = DSM 13459T), was isolated from paddy field soil in Chikugo, Fukuoka, Japan. The cells stained gram-negative, were 1.0-2.0 microm in diameter, were lysed by SDS and hypotonic solutions and were flagellated. Motility was not observed. The strain was able to use H2/CO2, 2-propanol/CO2, formate, 2-butanol/CO2 and cyclopentanol/CO2 as substrates for methanogenesis, but did not utilize acetate, ethanol, methanol or methylamines. The optimum temperature and pH were 25-30 degrees C and 6.7-7.2. Analysis of lipid component parts (core lipids, phospholipid polar head groups and glycolipid sugar moieties) showed the characteristic pattern of members of the family Methanomicrobiaceae except for the absence of glucose as a glycolipid sugar moiety. The G+C content of the DNA was 62.2 mol %. Sequence analysis of the 16S rDNA revealed that the strain belonged to the genus Methanoculleus. The strain had DNA-DNA hybridization values of less than 50% with type strains of Methanoculleus species. On the basis of phenotypic, genotypic and phylogenetic characteristics, the name Methanoculleus chikugoensis sp. nov. is proposed for strain MG62T (= JCM 10825T = DSM 13459T). The DNA hybridization study also revealed the close relationships of three species, Methanoculleus olentangyi, Methanoculleus bourgensis and Methanoculleus oldenburgensis, among Methanoculleus species.

Diversity of Cultivable Methane-Oxidizing Bacteria in Microsites of a Rice Paddy Field: Investigation by Cultivation Method and Fluorescence in situ Hybridization (FISH)

The diversity of cultivable methane-oxidizing bacteria (MOB) in the rice paddy field ecosystem was investigated by combined culture-dependent and fluorescence in situ hybridization (FISH) techniques. Seven microsites of a Japanese rice paddy field were the focus of the study: floodwater, surface soil, bulk soil, rhizosphere soil, root, basal stem of rice plant, and rice stumps of previous harvest. Based on pmoA gene analysis and transmission electron microscopy (TEM), four type I, and nine type II MOB isolates were obtained from the highest dilution series of enrichment cultures. The type I MOB isolates included a novel species in the genus Methylomonas from floodwater and this is the first type I MOB strain isolated from floodwater of a rice paddy field. In the type I MOB, two isolates from stumps were closely related to Methylomonas spp.; one isolate obtained from rhizosphere soil was most related to Methyloccocus-Methylocaldum-Methylogaea clade. Almost all the type II MOB isolates were related to Methylocystis methanotrophs. FISH confirmed the presence of both types I and II MOB in all the microsites and in the related enrichment cultures. The study reported, for the first time, the diversity of cultivable methanotrophs including a novel species of type I MOB in rice paddy field compartments. Refining growth media and culture conditions, in combination with molecular approaches, will allow us to broaden our knowledge on the MOB community in the rice paddy field ecosystem and consequently to implement strategies for mitigating CH4 emission from this ecosystem.

Methylomonas koyamae sp. nov., a type I methane-oxidizing bacterium from floodwater of a rice paddy field

A novel methane-oxidizing bacterium, strain Fw12E-Y(T), was isolated from floodwater of a rice paddy field in Japan. Cells of strain Fw12E-Y(T) were Gram-negative, motile rods with a single polar flagellum and type I intracytoplasmic membrane arrangement. The strain grew only on methane or methanol as sole carbon and energy source. It was able to grow at 10-40 °C (optimum 30 °C), at pH 5.5-7.0 (optimum 6.5) and with 0-0.1% (w/w) NaCl (no growth above 0.5% NaCl). 16S rRNA gene sequence analysis showed that strain Fw12E-Y(T) is related most closely to members of the genus Methylomonas, but at low levels of similarity (95.0-95.4%). Phylogenetic analysis of pmoA and mxaF genes indicated that the strain belongs to the genus Methylomonas (97 and 92 % deduced amino acid sequence identities to Methylomonas methanica S1(T), respectively). The DNA G+C content of strain Fw12E-Y(T) was 57.1 mol%. Chemotaxonomic data regarding the major quinone (MQ-8) and major fatty acids (C(16:1) and C(14:0)) also supported its affiliation to the genus Methylomonas. Based on phenotypic, genomic and phylogenetic data, strain Fw12E-Y(T) is considered to represent a novel species of the genus Methylomonas, for which the name Methylomonas koyamae sp. nov. is proposed. The type strain is Fw12E-Y(T) ( = JCM 16701(T) = NBRC 105905(T) = NCIMB 14606(T)).

Methylomagnum ishizawai gen. nov., sp. nov., a mesophilic type I methanotroph isolated from rice rhizosphere.

An aerobic, methane-oxidizing bacterium (strain RS11D-PrT) was isolated from rice rhizosphere. Cells of strain RS11D-PrT were Gram-stain-negative, motile rods with a single polar flagellum and contained an intracytoplasmic membrane system typical of type I methanotrophs. The strain utilized methane and methanol as sole carbon and energy sources. It could grow at 20–37 °C (optimum 31–33 °C), at pH 6.8–7.4 (range 5.5–9.0) and with 0–0.2 % (w/v) NaCl (there was no growth at above 0.5 % NaCl). pmoA and mmoX genes were present. The ribulose monophosphate and/or ribulose bisphosphate pathways were used for carbon assimilation. Results of sequence analysis of 16S rRNA genes showed that strain RS11D-PrT is related closely to the genera Methylococcus, Methylocaldum, Methyloparacoccus and Methylogaea in the family Methylococcaceae. The similarity was low (94.6 %) between strain RS11D-PrT and the most closely related type strain (Methyloparacoccus murrellii R-49797T). The DNA G+C content was 64.1 mol%. Results of phylogenetic analysis of the pmoA gene and chemotaxonomic data regarding the major cellular fatty acids (C16 : 1ω7c, C16 : 0 and C14 : 0) and the major respiratory quinone (MQ-8) also indicated the affiliation of strain RS11D-PrT to the Methylococcus–Methylocaldum–Methyloparacoccus–Methylogaea clade. On the basis of phenotypic, genotypic and phylogenetic characteristics, strain RS11D-PrT is considered to represent a novel genus and species within the family Methylococcaceae, for which the name Methylomagnum ishizawai gen. nov., sp. nov. is proposed. The type strain is RS11D-PrT ( = JCM 18894T = NBRC 109438T = DSM 29768T = KCTC 4681T).

Isolation and some properties of methane-oxidizing bacteria from a subtropical paddy field

Abstract Methane is the second most important greenhouse gas which contributes to global warming. As an important source of methane, rice paddy fields contribute an estimated lO% to the global methane emissions (IPCe 1992). Land use and agricultural practices significantly affect atmospheric methane fluxes (Bouwman 1989; Hutsch et al. 1994). Microbial oxidation of atmospheric methane in terrestrial environments is the only known net biological methane sink and the process consumes the equivalent of 1–l0% of the total global emission (Adamsen and King 1993). Methane-oxidizing bacteria (MOB, methanotrophic bacteria) are considered to be obligately or facultatively aerobic respiratory bacteria that can utilize methane as the sole source of carbon and energy for growth (Hanson et al. 1992; Roslev and King 1994). As a result, they are important regulators of atmospheric methane fluxes in nature (Mancinelli 1995). MOB have been isolated from a variety of environments including freshwater lakes, wetlands, and th...

Methanogenic Bacterial Populations in Some Lowland Paddy Field Soils of Burkina Faso (West Africa)

Abstract In wetland ecosystems, such as rice fields, methanogenic bacteria (MB) play important roles in global carbon cycling as terminal organic decomposers and in hydrogen cycling as hydrogen consumers, leading to methane production (Jorgensen 1982). In the global atmosphere, concentration of methane has been increasing by about 1% per year (Blake and Rowland 1986; Bouwman 1989; Dlugokensky et al. 1994) and it is considered that 80% is of biological origin (Seiler 1984). The environmental impact of methane on global warming has also been confirmed (Chappellaz et al. 1990). Rice paddy fields contribute to an estimated 10% of the global methane emission (Bouwman 1989; IPCC 1992) and the intensification of paddy cultivation may contribute considerably to the gradual increase of atmospheric methane (Rasmussen and Khalil 1981). From 1970 to 1990, rice production increased by 110% in West Africa (FAO 1970, 1990), as a direct result of encroachment on new lands throughout most of West Africa (Windmeijer and An...

Characterization of Desulfovibrio sp. isolated from some lowland paddy field soils of Burkina Faso

Abstract In a wetland ecosystem such as lowland ricefields, the anaerobic mineralization of organic matter is a key mechanism for nutrient recycling (Jorgensen 1982; Freney et al. 1982). In the process which involves several bacterial groups, sulfate reducers (Watanabe and Furusaka 1980; Widdel 1988; Ouattara and Jacq 1992; Nozoe 1997), methanogens (Asakawa and Hayano 1995; Dianou et al. 1997), sulfur and ferric ion reducers (Jacq et al. 1991) become active when the soil becomes anoxic (Amstrong 1969). Sulfate reducers are common in flooded soils (Watanabe and Furusaka 1980; Widdel 1988; Furusaka et al. 1991). Reported densities in rice soils ranged from 103 to 105 g-1 dry soils in Asia (Watanabe and Furusaka 1980) and from 102 to 109 g-1 dry soil in Senegal (Ouattara and Jacq 1992). Among the sulfate reducers, the “classical” Desulfovibrio species are known to oxidize typical fermentation products such as hydrogen, lactate, pyruvate, and dicarboxylic acids (Widdel 1988). So far, data on the isolation and...