Browsing by Author "Njiru, J. M."

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    Application of Genetic Engineering Approach in the Control of Cassava Brown Streak and Bacterial Blight Diseases
    (2013-12-14) Njiru, J. M.; Mgutu, Allan Jalemba; Tripathi, L.
    Cassava is the fifth most important food crop in the world. Cassava's importance in Africa and South America can't be overstated. As a drought-tolerant crop that does well in poor soils, it enhances household food security and is a source of income that provides livelihood to 800million people globally. Annual global production of cassava is estimated at 232 million tonnes; an average yield of 12.5 tonnes per hectare. Diseases and pests are the greatest biotic problems to cassava production across the East" and Central Africa (ECA) sub-region causing yield losses. Cassava bacterial blight (CBB) caused by Xanthomonas axonopodis pv. manihotis (Xam) is the most destructive bacterial disease in all cassava growing areas of the world causing yield losses of about 50% to 75%. Cassava is vulnerable to at least 20 different viral diseases, cassava brown streak disease (CBSD), being one of the most important viral diseases in Africa. CBSD is more lethal than other cassava viral disease because it causes severe necrosis within the edible storage roots. Crop improvement efforts through conventional breeding have aimed at attaining CBSD and CBB resistance, however these efforts have been largely unsuccessful due to the nature of the cassava plant for example poor flowering and low pollen fertility. This study aims at generating CBB and CBSD resistant plants through genetic engineering. Hypersensitivity response assisting protein (Hrap) gene will be used for transforming cultivar 60444. The constitutive expression of the Hrap in plants generates durable resistance against plant bacterial pathogens. This study seeks to use the Hrap gene to generate CBB resistance in cassava. There is no robust genotype-independent transformation protocol that has been developed for African farmer preferred cultivars. Through this study :;t protocol for transformation of three farmer preferred cultivars (TME 14, Mkombozi, Albert) using friable embryogenic callus (FEC) as the explant will be optimized, then transform one of the cultivars for resistance against CBSD using the optimized protocol. Post-transcriptional gene silencing (PTGS) offer significant potential for controlling RNA plant viruses like CBSD. Therefore this study aims at using the RNA interference (RNAi) approach in developing CBSD resistant lines. The presence, integration and expression of the transgenes will be confirmed by PCR, Southern blot and RT-PCR analysis followed by screen house evaluation to gauge resistance. Data on different stages of optimization during transformation and regeneration will be collected and analysed by ANOV A (p<0.05) and means will be separated using LSD (p<0.05). For FEC and cotyledon induction a completely, randomized design (CRD) will be used for all experiments with the FEC as the observation unit and the plate as the replicate. At list three replicates will be set per experiments. The regeneration Frequency (RF) and transformation frequency (TF) of all the cultivars will be determined
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    Effects of geohelmiths and schistosoma species on nutritional status of children in mwea irrigation scheme, Kenya
    (2011-11-24) Njiru, J. M.; Simbauni, Jemimah; Muhoho, N.
    Geohelminths and Schistosoma species are among the leading parasites causing morbidity and death to millions of people worldwide. Over 1450 million people are infected with geohelminths and over 200 million with schistosomes. These infections occur predominantly in rural areas and are associated with illiteracy, poverty, poor sanitation, unhygienic conditions and high risk of exposure to environmental and biological hazards. In Kenya the overall prevalence of geohelminths and schistosomiasis is estimated to be 25% but there appear to be pockets of very high endemicity. These are found in the Coast and in Nyanza Provinces, which also form pockets of high malnutrition cases in the country. Heavy infection with geohelminths and Schistosoma species has a negative impact on the nutritional status of children. The main objective of this study was to examine the prevalence of geohelminths and Schistosoma sp infections among the primary school children in Mwea Irrigation Scheme and how this affected their nutritional status. A sample population of 196 children was used for the study. Assessment of nutritional status was done using anthropometric measurements, infection rate was established using Kato Katz technique for examining stool and haemoglobin level, estimated using Drabkin's method was used to assess anaemia. All the infected children received treatment as part of the control program. Data was analysed using the Statistical Package for Social Sciences (SPSS) and Epi info statistical packages. The overall prevalence rate of geohelminths and Schistosoma sp was found to be 26%. Infection with Schistosoma mansoni was highest at a rate of 17.5%, that of hookworm and Ascaris lumbricoides was 5.6% and 4.6% respectively and the least was infection with Trichuris trichiura at 3.1%. Multiple infections were reported at the rate of 17.6% of the infected individuals. Malnutrition was prevalent, 27.5% of the sample population was underweight and 34.9% was stunted. A significant relationship existed between infection and malnutrition. The Chi-square test revealed a significant difference in stunting between the infected children and those with no infection (P < 0.05). A sub-sample of 103 pupils was assessed for anaemia. The prevalence of anaemia was found to be 44.1 % with boys being more anaemic than girls but the difference was not statistically significant. There was a relationship between infection and haemoglobin level with Schistosoma sp significantly causing anaemia more than the geohelminths (P < 0.05). The results of this study will act as a base for other researches and to advice the community on the importance of intervention measures that will give the child a sanitary environment.
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    Prevalence and antimicrobial resistance profile of bacterial foodborne pathogens in Nile tilapia fish (Oreochromis niloticus) at points of retail sale in Nairobi, Kenya
    (Frontiers in Antibiotics, 2023-05-24) Mumbo, M. T.; Nyaboga, E. N.; Kinyua, J.; Muge,E. K.; Mathenge,S. G. K.; Muriira, G.; Rotich, H.; Njiru, J. M.; Njiraini, B.
    Proteus spp., Staphylococcus spp., Pseudeomonas spp., and pathogenic Vibrios are among the major foodborne pathogens associated with the consumption of contaminated fish. The increasing occurrence of antimicrobial resistance in these pathogens is a serious public health concern globally and therefore continuous monitoring of antimicrobial resistance of these bacteria along the food chain is crucial for for control of foodborne illnesses. The aim of this study was to assess the prevalence, antimicrobial resistance patterns, antibiotic resistance genes, and genetic diversity of bacterial foodborne pathogens recovered from fresh Nile tilapia (Oreochromis niloticus) obtained from retail markets in Nairobi, Kenya. A total of 68 O. niloticus fish with an average weight of 300.12 ± 25.66 g and body length of 23.00 ± 0.82 cm were randomly sampled from retail markets and tested for the presence of Proteus, Staphylococcus aureus, Pseudomonas aeruginosa, Vibrio cholerae, and Vibrio parahaemolyticus. Standard culture-based microbiological and Kirby-Bauer agar disk diffusion methods were used to isolate and determine the antimicrobial resistance patterns of the isolates to 11 selected antibiotics. Statistical analysis was performed using Minitab v17.1, with p < 0.05 considered significant. The genetic diversity of the multidrug-resistant (MDR) and extensively drug-resistant (XDR) bacteria was determined using 16S rRNA sequencing and phylogenetic analysis, and polymerase chain reaction (PCR) was used for detection of antibiotic resistance genes in MDR bacterial isolates. High levels of bacterial contamination were detected in fresh O. niloticus fish (44/68, 64.71%). The most prevalent bacteria were Proteus spp. (44.12%), with the rest of the bacterial species registering a prevalence of 10.29%, 4.41%, 2.94%, and 2.94% (for S. aureus, P. aeruginosa, V. cholerae, and V. parahaemolyticus, respectively). Antimicrobial resistance was detected in all the bacteria species and all the isolates were resistant to at least one antibiotic except cefepime (30 µg). Additionally, 86.36% of the isolates exhibited multidrug resistance, with higher multiple antibiotic resistance indices (MAR index >0.3) indicating that fresh O. niloticus fish were highly contaminated with MDR bacteria. Results of 16S rRNA sequences, BLASTn analysis, and phylogenetic trees confirmed the identified MDR bacterial isolates as Proteus mirabilis and other Proteus spp., S. aureus, P. aeruginosa, V. cholerae, and V. parahaemolyticus. PCR analysis confirmed the presence of multiple antibiotic resistance genes blaTEM-1, blaCMY-2, tetA, tetC, Sul2, dfrA7, strA, and aadA belonging to β-lactamases, tetracycline, sulfonamide, trimethoprim, and aminoglycosides in all the MDR bacterial isolates. There was strong correlation between antibiotic- resistant genes and phenotypic resistance to antibiotics of MDR bacteria. This study showed high prevalence of multidrug resistance among foodborne bacterial isolates from fresh O. niloticus fish obtained from retail markets. From this study, we conclude that fresh O. niloticus fish are a potential source of MDR bacteria, which could be a major risk to public health as a consequence of their dissemination along the human food chain. These results highlight the prevalence of antimicrobial-resistant foodborne pathogens in fish purchased from retail markets and underscore the risk associated with improper handling of fish.