Etiology of Diarrhea in Children Younger Than 5 Years Attending the Bengo General Hospital in Angola.

BACKGROUND: Diarrheal disease is among the leading causes of death in children younger than 5 years, especially in developing countries. The aim of this study was to investigate the most frequent etiological agents of diarrhea and its associated factors in children younger than 5 years attending the Bengo General Hospital in Angola. METHODS: From September 2012 through December 2013, stool samples were collected from 344 children presenting with diarrhea to investigate the presence of viral, bacterial and parasitic agents. Relevant sociodemographic and clinical data were obtained from parents and caregivers. RESULTS: An enteric pathogen was detected in 66.6% of stool samples: Cryptosporidium spp. (30.0%), rotavirus (25.1%), Giardia lamblia (21.6%), diarrheagenic Escherichia coli (6.3%), Ascaris lumbricoides (4.1%), adenovirus (3.8%), Strongyloides stercoralis (3.5%), astrovirus (2.6%), Hymenolepis nana (1.7%), Entamoeba histolytica/dispar (0.9%), Taenia spp. (0.6%), Trichuris trichiura (0.3%) and Entamoeba histolytica (0.3%). Children younger than 12 months were more frequently infected with Cryptosporidium spp. compared with older children (age: 12-59 months), independently of sex, season, lethargy and wasting [odds ratio (OR): 3.5, 95% confidence interval (95% CI): 2.0-6.2]. Age (OR: 5.0, 95% CI: 2.6-9.3), vomiting (OR: 2.7, 95% CI: 1.5-4.8) and type of admission (inpatients, OR: 0.5, 95% CI: 0.3-0.9) were significantly associated with rotavirus infection. CONCLUSIONS: This study demonstrates high rates of infection with an enteric pathogen, particularly in children younger than 12 months, emphasizing the need to address diarrheal disease in this age group.

High rate of detection of G8P[6] rotavirus in children with acute gastroenteritis in São Tomé and Príncipe.

The burden of rotavirus infections greatly affects the low-income African countries. In the absence of epidemiological data on pediatric diarrhea in São Tomé and Príncipe (STP), a study was conducted from August to December 2011. Rotavirus antigen was detected in 36.7 % of the collected fecal samples (87/237). G8P[6] was identified as the predominant genotype (71.1 % detection rate), while G1P[8] represented only 8.4 %. Phylogenetic analysis of VP7 G8 strains showed clustering within lineage G8d, while VP4 P[6] strains clustered within lineage 1a. Our results represent the first report on rotavirus from STP and show one of the highest detection rates of G8 rotaviruses worldwide.

Iron oxide nanoparticles modulate the interaction of different antibiotics with cellular membranes.

The interaction of nanomaterials with cells and lipid bilayers is critical in many applications such as phototherapy, imaging and drug/gene delivery. These applications require a firm control over nanoparticle-cell interactions, which are mainly dictated by surface properties of the nanoparticles. The aim of this study was to investigate the interaction of Fe3O4 nanoparticles functionalized with several wide use antibiotics with opossum kidney (OK) cellular membranes in order to reveal changes in the membrane organization at different temperatures. We also investigated the in vivo biodistribution of the tested nanoparticles in a mouse model. Our results showed that, at low temperatures (31-35°C), plain Fe3O4 nanoparticles induced a drop of the membrane fluidity, while at physiological or higher temperatures (37-39°C) the membrane fluidity was increased. On the other hand, when nanoparticles functionalized with the tested antibiotics were used, we observed that the effect was opposite as compared to control Fe3O4 nanoparticles. Although most of antibiotics, used as plain solutions or linked on magnetite nanoparticles, proved heterogeneous effect on in vitro OK cells membrane fluidity, the aminoglycosides streptomycin and neomycin, used both as plain solutions and also combined with nanoparticles kept the same effect in all experimental conditions, increasing the membrane fluidity of OK cells plasma membrane. In vivo results showed that the antibiotic functionalized nanoparticles have a similar biodistribution pattern within the mouse body, being transported through the blood flow and entering the macrophages through endocytosis. Functionalized magnetite nanoparticles manifested a preferential biodistribution pattern, clustering within the lungs and spleen of treated mice. These results demonstrate that antibiotics manifest a different effect on plasma membrane fluidity depending on their type and temperature. Magnetite nanoparticles may interfere with antibiotic-cellular interactions by changing the plasma membrane fluidity. The fact that the antibiotic functionalized magnetite nanoparticles have a similar biodistribution pattern, are transported through the blood flow, and they increase the cellular uptake of the drug, suggest that they may be used for further studies aiming to develop personalized targeted delivery and controlled release nanoshuttles for treating localized and systemic infections.

Interaction of gentamicin polycation with model and cell membranes.

The interaction of positively-charged antibiotic gentamicin with cell membranes was studied to determine if any changes in membrane organization were induced by the drug. Opossum kidney epithelia (OK) cells were used as models of eukaryotic cells. Two methods were used: laurdan fluorescence spectroscopy and fluorescence anisotropy recordings on 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene p-toluenesulfonate (TMA-DPH) labeled cell suspensions. Both methods showed an altered membrane hydration and fluidity of gentamicin treated cells. Liposomes prepared from dimyristoyl-phosphatidylcholine (DMPC) mixed with cardiolipin, which mimics the heterogeneous charge composition of the natural cell membrane, were used to determine the effect of gentamicin on artificial bilayers. The membrane lipid packing as revealed by generalized polarization (GP) and fluorescence anizotropy variation with increasing temperature was studied. It was found that the generalized polarization of liposomal membranes containing a negatively charged lipid (cardiolipin) is higher in the presence of gentamicin; in the membrane of living cell (OK), gentamicin induces, on the contrary, a decrease of general polarization. Considering the role of membrane organization in the function of transmembrane channels and receptors, our findings suggest hypotheses that may explain the permeation of gentamicin through the living cell membrane by using these channels.

Rotavirus stimulates release of serotonin (5-HT) from human enterochromaffin cells and activates brain structures involved in nausea and vomiting.

Rotavirus (RV) is the major cause of severe gastroenteritis in young children. A virus-encoded enterotoxin, NSP4 is proposed to play a major role in causing RV diarrhoea but how RV can induce emesis, a hallmark of the illness, remains unresolved. In this study we have addressed the hypothesis that RV-induced secretion of serotonin (5-hydroxytryptamine, 5-HT) by enterochromaffin (EC) cells plays a key role in the emetic reflex during RV infection resulting in activation of vagal afferent nerves connected to nucleus of the solitary tract (NTS) and area postrema in the brain stem, structures associated with nausea and vomiting. Our experiments revealed that RV can infect and replicate in human EC tumor cells ex vivo and in vitro and are localized to both EC cells and infected enterocytes in the close vicinity of EC cells in the jejunum of infected mice. Purified NSP4, but not purified virus particles, evoked release of 5-HT within 60 minutes and increased the intracellular Ca²âº concentration in a human midgut carcinoid EC cell line (GOT1) and ex vivo in human primary carcinoid EC cells concomitant with the release of 5-HT. Furthermore, NSP4 stimulated a modest production of inositol 1,4,5-triphosphate (IP3), but not of cAMP. RV infection in mice induced Fos expression in the NTS, as seen in animals which vomit after administration of chemotherapeutic drugs. The demonstration that RV can stimulate EC cells leads us to propose that RV disease includes participation of 5-HT, EC cells, the enteric nervous system and activation of vagal afferent nerves to brain structures associated with nausea and vomiting. This hypothesis is supported by treating vomiting in children with acute gastroenteritis with 5-HT3 receptor antagonists.