Pierre Ngassam

Extended-spectrum-beta-lactamase-producing Enterobacteriaceae in Yaounde, Cameroon

ABSTRACT Organisms producing extended-spectrum β-lactamases (ESBLs) have been reported in many countries, but there is no information on the prevalence of ESBL-producing members of the family Enterobacteriaceae in Cameroon. A total of 259 Enterobacteriaceae strains were isolated between 1995 and 1998 from patients at the Yaounde Central Hospital in Cameroon. Enterobacterial isolates resistant to extended-spectrum cephalosporin and monobactam were screened for ESBL production by the double-disk (DD) synergy test. Thirty-one (12%) of these Enterobacteriaceae strains were shown to be positive by the DD synergy test, suggesting the presence of ESBLs. Resistance to oxyimino-cephalosporins and monobactams of 12 (38.7%) of the 31 strains—i.e., 6 Klebsiella pneumoniae, 4 Escherichia coli, 1 Citrobacter freundii, and 1 Enterobacter cloacae strain—was transferred to E. coli HK-225 by conjugation. Resistance to gentamicin, gentamicin plus trimethoprim-sulfamethoxazole, or trimethoprim-sulfamethoxazole was cotransferred into 6, 2, and 1 of these transconjugants, respectively. All 12 transconjugants were resistant to amoxicillin, piperacillin, all of the cephalosporins, and aztreonam but remained susceptible to cefoxitin and imipenem. Crude extracts of β-lactamase-producing transconjugants were able to reduce the diameters of inhibition zones around disks containing penicillins, narrow- to expanded-spectrum cephalosporins or monobactams when tested against a fully susceptible E. coli strain but had no effect on such zones around cefoxitin, imipenem, and amoxicillin-clavulanate disks. The β-lactamases produced by the 12 tranconjugants turned out to be SHV-12 by DNA sequencing. Therefore, the ESBL SHV-12 is described for the first time in Cameroon.

Mapping of Schistosomiasis and Soil-Transmitted Helminthiasis in the Regions of Centre, East and West Cameroon

Background Schistosomiasis and soil-transmitted helminthiasis (STH) are widely distributed in Cameroon. Although mass drug administration (MDA) of mebendazole is implemented nationwide, treatment with praziquantel was so far limited to the three northern regions and few health districts in the southern part of Cameroon, based on previous mapping conducted 25 years ago. To update the disease distribution map and determine where treatment with praziquantel should be extended, mapping surveys were conducted in three of the seven southern regions of Cameroon, i.e. Centre, East and West. Methodology Parasitological surveys were conducted in April–May 2010 in selected schools in all 63 health districts of the three targeted regions, using appropriate research methodologies, i.e. Kato-Katz and urine filtration. Principal Findings The results showed significant variation of schistosomiasis and STH prevalence between schools, villages, districts and regions. Schistosoma mansoni was the most prevalent schistosome species, with an overall prevalence of 5.53%, followed by S. haematobium (1.72%) and S. guineensis (0.14%). The overall prevalence of schistosomiasis across the three regions was 7.31% (95% CI: 6.86–7.77%). The prevalence for Ascaris lumbricoides was 11.48 (95% CI: 10.93–12.04%), Trichuris trichiura 18.22% (95% CI: 17.56–18.90%) and hookworms 1.55% (95% CI: 1.35–1.78%), with an overall STH prevalence of 24.10% (95% CI: 23.36–24.85%) across the three regions. STH was more prevalent in the East region (46.57%; 95% CI: 44.41–48.75%) in comparison to the Centre (25.12; 95% CI: 24.10–26.17%) and West (10.49%; 95% CI: 9.57–11.51%) regions. Conclusions/Significance In comparison to previous data, the results showed an increase of schistosomiasis transmission in several health districts, whereas there was a significant decline of STH infections. Based on the prevalence data, the continuation of annual or bi-annual MDA for STH is recommended, as well as an extension of praziquantel in identified moderate and high risk communities for schistosomiasis.

Population genetic structure of the malaria vector Anopheles nili in sub-Saharan Africa

BackgroundAnopheles nili is a widespread efficient vector of human malaria parasites in the humid savannas and forested areas of sub-Saharan Africa. Understanding An. nili population structure and gene flow patterns could be useful for the development of locally-adapted vector control measures.MethodsPolymorphism at eleven recently developed microsatelitte markers, and sequence variation in four genes within the 28s rDNA subunit (ITS2 and D3) and mtDNA (COII and ND4) were assessed to explore the level of genetic variability and differentiation among nine populations of An. nili from Senegal, Ivory Coast, Burkina Faso, Nigeria, Cameroon and the Democratic Republic of Congo (DRC).ResultsAll microsatellite loci successfully amplified in all populations, showing high and very similar levels of genetic diversity in populations from West Africa and Cameroon (mean Rs = 8.10-8.88, mean He = 0.805-0.849) and much lower diversity in the Kenge population from DRC (mean Rs = 5.43, mean He = 0.594). Bayesian clustering analysis of microsatellite allelic frequencies revealed two main genetic clusters in the dataset. The first one included only the Kenge population and the second grouped together all other populations. High Fst estimates based on microsatellites (Fst > 0.118, P < 0.001) were observed in all comparisons between Kenge and all other populations. By contrast, low Fst estimates (Fst < 0.022, P < 0.05) were observed between populations within the second cluster. The correlation between genetic and geographic distances was weak and possibly obscured by demographic instability. Sequence variation in mtDNA genes matched these results, whereas low polymorphism in rDNA genes prevented detection of any population substructure at this geographical scale.ConclusionOverall, high genetic homogeneity of the An. nili gene pool was found across its distribution range in West and Central Africa, although demographic events probably resulted in a higher level of genetic isolation in the marginal population of Kenge (DRC). The role of the equatorial forest block as a barrier to gene flow and the implication of such findings for vector control are discussed.

Genetic diversity and phylogenetic position of the subclass Astomatia (Ciliophora) based on a sampling of six genera from West African oligochaetes (Glossoscolecidae, Megascolecidae), including description of the new genus Paraclausilocola n. gen

To more confidently assess phylogenetic relationships among astome ciliates, we obtained small subunit (SSU) rRNA sequences from nine species distributed in six genera and three families: Almophrya bivacuolata, Eudrilophrya complanata, Metaracoelophrya sp. 1, Metaracoelophrya sp. 2, Metaracoelophrya intermedia, Metaradiophrya sp., Njinella prolifera, Paraclausilocola constricta n. gen., n. sp., and Paraclausilocola elongata n. sp. The two new species in the proposed new clausilocolid genus Paraclausilocola n. gen. are astomes with no attachment apparatus, two files of contractile vacuoles, and an arc-like anterior suture that has differentiations of thigmotactic ciliature on the anterior ends of the left kineties of the upper surface. Phylogenetic analyses were undertaken using neighbor-joining, Bayesian inference, maximum likelihood, and maximum parsimony. The nine species of astomes formed a strongly supported clade, showing the subclass Astomatia to be monophyletic and a weakly supported sister clade to the scuticociliates. There were two strongly supported clades within the astomes. However, genera assigned to the same family were found in different clades, and genera assigned to the same order were found in both clades. Thus, astome taxa appear to be paraphyletic when morphology is used to assign species to genera.

Impact of urbanization on aquatic insect assemblages in the coastal zone of Cameroon: the use of biotraits and indicator taxa to assess environmental pollution

Abstract Internationally, waterways within urban area are subject to broad-scale environmental pollution. In this study, we used in-stream aquatic insects as surrogates to measure the aquatic health of urban streams in the Douala township. We compared these assessments with samples collected from a suburb stream. Aquatic insects were sampled monthly over a 13-month period in ten urban sites and two forest sites. Measurements of the environmental variables were done simultaneously. Results revealed that urban streams are highly polluted and ecologically impaired. The classification of samples by the self-organized mapping analysis permitted to clearly separate urban and non-urban aquatic insect assemblages. Higher total taxa richness, higher values of diversity indices, and higher Ephemeroptera–Plecoptera–Trichoptera (EPT) scores were recorded in forest sites. Inversely, in urban streams, very low taxa richness was observed, with the proliferation of dipterans, and the absence of EPT taxa. The EPT, coleoptera, and hemiptera taxa, the functional feeding groups of shredders and predators, and the insect taxa relying on gills and plastron for breathing were good predictors of anthropogenic pollution. Indicator taxa and ecological functioning traits identified in this study could enhance the accuracy of water quality assessment methodologies and potentially enable predictive models for evaluating the human impact in stream ecosystems.

Contribution to the study of hysterocinetidae Ciliates of the genus Ptychostomum. Description of six new species

Summary Six new species of Ciliates belonging to the genus Ptychostomum are described. They were found in the intestine of Glossoscolecidae Oligochaetes of the genus Alma from Cameroon. Though their organizational plan is basically the one of the genus and of the family Hysterocinetidae, the variability of certain particular characteristics confirms the existence of a large diversity within the genus, that forces reexamination of the diagnosis of the genus Ptychostomum .

[Revision of of the subfamily of Metaracoelophryinae de Puytorac 1972 (Oligohymenophora: Hoplytophryida: Hoplytophryidae), astome ciliates of the digestive tract of Oligochaeta worms of Africa: description of five new species].

Cinq nouvelles espèces de ciliés astomes, présentes dans le tube digestif de vers oligochètes du genre Alma du Cameroun, ont été décrites. Les techniques utilisées sont : l’observation vitale, la coloration au DAPI, la microscopie électronique à balayage et les imprégnations argentiques selon Fernandez Galiano, 1966. Ce travail confirme la présence des genres Paracoelophrya et Dicoelophrya dans le tube digestif des oligochètes du genre Alma du Gabon et du Cameroun ; il permet de faire une synthèse récapitulative de la sous-famille des Metaracoelophryinae. De plus, est confirmée l’homogénéité de ce groupe, et est reposée la question de la parenté phylogénétique des Hoplitophryida.

Description of the new genus Hysterocinetoides (Ciliophora, Hysterocinetidae) and revision of the systematics of the subclass Hysterocinetia

Two new species belonging to the new genus Hysterocinetoides are described after protargol staining. They were found in the intestine of worms of the genus Alma (Oligochaeta, Glossoscolecidae) from Cameroon. Their buccal apparatus and kinetosomal infraciliature are typically those of the family Hysterocinetidae. But the sucker has an inverted-U shape and is devoid of skeletal fibers and isolated segments of kineties. These characters justify the creation of the new genus. A review of the diversification of genera among the family Hysterocinetidae is followed by a revision of the systematics of the subclass Hysterocinetia.

Pléomorphisme de Blastocystis sp. dans des eaux polluées à Yaoundé (Cameroun)

Une etude visant a determiner la qualite des formes environnementales de Blastocystis sp.a ete menee dans la ville de Yaounde, region ecologique du centre-sud forestier du Cameroun, sur le cours d’eau Mingoa, le lac de retenue (municipal) et sur deux effluents de son bassin-versant, en zone urbaine. Les analyses biologiques ont revele la presence de sept formes de Blastocystis sp. dans les proportions globales de 29,4 % de granulaires, 28,1 % de blastocystes vacuolaires, 27,2 % de kystes, 7,3 % d’amiboides, 3,9 % de multivacuolaires, 2,1 % d’organismes de forme prekystique et 1,8 % de forme avacuolaire, pour un total moyen de 932 Ind/L. Les differentes formes ont ete identifiees par deux methodes : l’observation directe et la technique de flottation au reactif de Junod apres coloration au Lugol et au MIF (merthiolate-iode-formol). Les tailles varient de 3 a 20 μm. Les formes de petite taille dominent a toutes les stations. La dynamique d’abondance de cet organisme est significativement correlee a la couleur, aux TDS (total dissolved solids), a la turbidite de l’eau et au pH (p < 0,001). De plus, les formes granulaires, vacuolaires et kystiques sont les plus abondantes dans les echantillons analyses. La prevalence de Blastocystis hominis dans les eaux de surface, les eaux usees et les eaux issues d’une station de traitement pendant la periode d’etude represente une inquietude quant a la contamination pour les populations riveraines qui peuvent etre exposees a la blastocytose pendant l’utilisation des ressources hydriques.

Diversity, abundance and incidence of fruit pest insects on three Solanum varieties (Solanaceae) in two agro-ecological zones of Southern Cameroon

1 Laboratory of Zoology, Department of Animal Biology and Physiology, Faculty of Science, University of Yaounde I, P. O. Box 812 Yaounde, Cameroon. 2 Laboratory of Zoology, Department of Biological Sciences, Higher Teacher‟s Training College, University of Yaounde I, P. O. Box 47 Yaounde, Cameroon. 3 Department of Biology, Higher Teacher‟s Training College, University of Bamenda, P. O. Box 39 Bamenda, Cameroon. 4 Laboratory of Parasitology and Ecology, Department of Animal Biology and Physiology, Faculty of Science, University of Yaounde I, P. O. Box 812 Yaounde, Cameroon.