Browsing by Author "Mdegela, Robinson H"

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Current state of modern biotechnological-based aeromonas hydrophila Vaccines for aquaculture: a systematic review
(Hindawi BioMed Research International, 2019-07-29) Mzula, Alexanda; Wambura, Philemon N; Mdegela, Robinson H; Shirima, Gabriel M
This systematic review describes what “the cutting edge vaccines for Aeromonas hydrophila are”. The focus is on types of high tech biotechnological based vaccines, target gene or antigen in developing these vaccines, and challenge model fish species used in vaccines efficacy testing. Vaccines delivery methods, immune response, and their efficacy, adjuvant or carrier systems used, and the overall experimental setup or design of the vaccines under investigation are also described. The search for the original papers published between 2009 and 2018 was conducted in June of 2018, using the PubMed and Google scholar electronic database. Twenty- three (23/4386) studies were included in the final assembly using PRISMA guidelines (Protocol not registered). Recombinant protein vaccines were the highly experimented type of the modern biotechnological based vaccines identified in the selected studies (16/23; 70%). Outer membrane proteins (OMPs) of different β-barrels were shown to be a potential antigenic entity for A. hydrophila vaccines (57%). Intraperitoneal route with conventional carries or adjuvants was the highly applied delivery system while very few studies used herbal based vaccine adjuvants and nanomaterial as a vaccine carrier. Variation was observed in terms of protection levels in the selected studies. The experimental designs partly contributed to the observed variation. Therefore, recombinant vaccines that use new carrier system technologies and delivered through oral route in feeds would have been of great value for use in the prevention and control of A. hydrophila infections in fish. Despite the usefulness as academic tools to identify what is important in pathogenicity of the etiological agent to the host fish, these vaccines are only economically viable in very high-value animals. Therefore, if vaccination is a good option for A. hydrophila group, then simple autogenous vaccines based on accurate typing and evidence-based definition of the epidemiological unit for their use would be the most viable approach in terms of both efficacy and economic feasibility especially in low and middle-income countries (LMIC).
Epifriedelanol is the key Compound to antibacterial Effects of extracts of synadenium glaucescens (pax) against Medically important bacteria
(Frontiers, 2023) Msengwa, Zaituni; Rwegoshora, Frank; David, Credo; Mwesongo, James; Mafuru, Magesa; Mabiki, Faith P; Mwang’onde, Beda J; Mtambo, Madundo M; Kusiluka, Lughano J. M; Mdegela, Robinson H; Olsen, John E
Introduction: Synadenium glaucescens has been used for the treatment of bacterial infections in many parts of the world. We investigated the antibacterial and cytotoxicity activities of secondary metabolites of this plant. Methods: Hexane, dichloromethane, methanol, and water were used as extraction solvents. The extract of the root bark was fractionated with ethyl acetate and methanol. The isolation of compounds from root barks, leaves and stem wood extracts were carried out using column chromatography. Antibacterial activities were characterized based on growth curves, killing curves and MIC determinations. Haemolytic effect towards sheep red blood cells (RBCs) was analysed with spectrophotometer at the wavelength of 540nm. Results and Discussion: Extracts from whole root and root bark showed strong activity against Staphylococcus aureus, and Streptococci and Enterococci species, and moderate to weak activity against Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella species, Shigella sonnei and Yersinia enterocolitica. Staphylococcus aureus was the most susceptible, and E. coli and Klebsiella pneumonia were the least susceptible ones. Likewise, extracts, fractions, sub-fractions and epifriedelanol demonstrated bacteriostatic activity against S. aureus. The haemolytic activity of the extracts, fractions, sub-fractions and epifriedelanol was significantly low compared to the positive control, hydrogen peroxide. But extract from leaves showed high haemolytic effects at the concentrations of 500 mg/mL and 1000 mg/mL. Thus, extracts of S. glaucescens have antibacterial activity against several Gram-positive bacteria including Methicillin Resistant S. aureus with low haemolytic activity. At high concentrations, the extracts from leaves have toxicity risk. More studies for the active compounds are required for biological testing.
In vitro antibacterial potential of extracts of sterculia Africana, acacia sieberiana, and cassia abbreviata ssp. abbreviata used by yellow baboons (papio cynocephalus) for possible self-medication in Mikumi national park, Tanzania
(Hindawi, 2018) Kirabo, Irene; Mabiki, Faith P; Mdegela, Robinson H; Obbo, Christopher J. D
In the animals in general and nonhuman primates in particular self-medication has been widely reported; however, little is still known about the pharmacological activity of the extracts present in their daily diet. The in vitro antibacterial activity of the stem, root bark, and leaf extracts of three selected plants on which yellow baboons feed in an unusual manner in Mikumi National Park, Tanzania, was evaluated. Crude plant extracts were tested against Gram positive and Gram negative bacteria of medical and veterinary importance employing a modified agar well diffusion method and Minimum Inhibitory Concentration (MIC) technique. The lowest MIC value for Gram positive strains was 0.31 mg/ml demonstrated by Cassia abbreviata ssp. abbreviata against Staphylococcus aureus (ATCC 25923). The highest susceptibility to the ethanol plant extracts was exhibited by Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus, examples of microbes that affect both human and nonhuman primates. These findings demonstrate that the plant extracts from Sterculia africana, Acacia sieberiana, and Cassia abbreviata ssp. abbreviata have antibacterial activity and may be used as feed for their prophylactic benefits. Remarkably, the lowest MIC of 0.16 mg/ml was only 16-fold weaker than Gentamicin, a standard drug.
Isolation and identification of euphol and β-sitosterol from the dichloromethane extracts of Synadenium glaucescens
(2016-06) Nyigo, Vitus A; Peter, Xolani; Fouche, Gerda; Mabiki, Faith; Malebo, Hamisi M; Mdegela, Robinson H
Purification of dichloromethane extract from root barks and leaves of Synadenium glaucescens respectively resulted into the isolation of two compounds namely Euphol and β -sitosterol. Chemical structures were established mainly by using 1 H an d 13 C NM R data and by comparing current NMR data with those reported in the literature. Both compounds are known and have been isolated from other plant species but are being reported from this plant species for the first time.
Occurrences of thermophilic Campylobacter in pigs slaughtered at Morogoro slaughter slabs, Tanzania
(Springer Science+Business Media B.V, 2010-08) Mdegela, Robinson H; Kibona, Laurence; Jacob, Petro; Nonga, Hezron Emmanuel
Occurrences of thermophlic Campylobacter in pigs and pig carcasses was investigated in a cross-sectional study that was carried out in three selected slaughter slabs in Morogoro municipality, Tanzania. Before sampling, the slab hygiene, slaughter, carcass dressing, and meat handling was assessed. Fecal samples were collected from 66 slaughter pigs at the kill floor. After slaughter, a 100-cm 2 area on medial surface of the thigh muscles of dressed carcasses was sampled using sterile cotton swabs. Thereafter, the jejunal, cecal, and colon contents were also sampled. The samples were subjected to standard bacteriological examination using Skirrows protocol. In all slaughter slabs visited, it was found that pig slaughter, dressing, and meat handling was done on the ground under unhygienic condition. All the slaughter slab environment were dirty and had neither tap water or drainage systems. Thermophilic Campylobacter prevalence in slaugh- tered pig was 66.7% while contamination rate of dressed carcasses was 10.6%. Of the Campylobacter-positive car- casses, five (12.2%) were from the animals which were also positive to Campylobacter. The isolation rate of Campylobac- ter in the cecum was higher (34.8%) compared to the small intestines (28.8%) and colon (16.7%) although the difference was not statistically significant (P>0.05). Campylobacter jejuni was the most prevalent species as it constituted 74% of all isolates, while Campylobacter coli was isolated at 26%. This suggests possible risks of infection to people through consumption of contaminated pork or through contact with infected pigs. Cecum was found to be the major part of intestine highly colonized by Campylobacter.
Phenotypic and molecular detection of Aeromonads infection in farmed Nile tilapia in Southern highland and Northern Tanzania
(Elsevier Ltd, 2019-07) Mzula, Alexanda; Wambura, Philemon N; Mdegela, Robinson H; Shirima, Gabriel M
Aeromonads disease outbreaks are now becoming a common phenomenon in freshwater farmed fish worldwide. In Tanzania, the aquaculture field is increasingly growing save to sustain food protein demand and strengthen household income. To avoid losses that tilapia fish farmers might account, information on magnitude of infection and characteristics of the aetiological agent is vital. This study aimed to establish the prevalence of aeromonads infection in farmed tilapia and assess pond and fish health management practices. A cross sectional study was carried out between February 2017 and October 2018 and a total of 816 whole fish samples were aseptically collected from 32 ponds in Ruvuma, Mbeya, Iringa and Kilimanjaro regions. During sampling, water quality parameters were taken and questionnaires to assess the knowledge of farmers were also provided. Isolation and identification of bacteria was conducted using conventional biotyping and molecular techniques. A total of 201 (80.4%) of 250 isolates that were conventionally identified were confirmed to be aeromonads by amplification of 820 bp rpoD gene, making the overall prevalence of 24.6% (201, n 1⁄4 816). Sequencing of rpoD gene and phylogenetic analysis revealed two aeromonads species, Aeromonas hydrophila and Aeromonas veronii. To the best of our knowledge this is the first report to establish the prevalence of aeromonads in apparently healthy farmed tilapia in Southern highlands and Northern zone of Tanzania. In addition it was observed that farmers were lacking proper knowledge and awareness on pond management practices and fish health management. In conclusion, the infection rate of aeromonads in apparently health tilapia coupled with lack of proper knowledge and awareness on pond and fish health management by fish farmers in the study area poses risk of diseases outbreaks in their farms in future. Therefore, it is recommended that the farmers should be trained on basic pond and fish health management and control strategies.
Virulence pattern of circulating aeromonads isolated from farmed nile tilapia in Tanzania and novel antibiotic free attenuation of aeromonas hydrophila strain tzr7-2018
(Aquaculture Reports, 2020) Mzula, Alexanda; Wambura, Philemon N; Mdegela, Robinson H; Shirima, Gabriel M
Aeromonads are gram-negative, rod-shaped, facultative anaerobes bacteria known to cause motile aeromonads septicemia diseases (MAS) in warm freshwater farmed fish. Outbreaks are associated with pathogenicity of aeromonads in fish which is partly contributed by virulence characteristics of the etiological agent. The objective of this study was to assess the virulence characteristics of the previously isolated and identified aeromonads, and attenuate potential Aeromonas hydrophila strain TZR7-2018 to serve as local vaccine candidate. Six virulence genes and other virulence characteristics were molecularly and phenotypically assessed both using in-vitro and in-vivo approaches. Attenuation of A. hydrophila parent strain TZR7-2018 + was performed by passaging through thermal continuous sub-culturing 40 times in Tryptic soy agar (TSA). Bacterin was prepared by formalin in- activation from the same parent strain. Humoral responses were assayed using quantitative serological agglu- tination test (qSAT) while protective efficacy was measured through relative percent survival (RPS). A total 240 Nile tilapia fingerlings with an average weight of 8.1 ± 0.4 g were used in all in-vivo studies. The presence of aerolysin (aer), cytotoxic enterotoxin (act), elastase (ahy), haemolysin (hly), serine (ser) and polar flagella (fla) genes were determined using PCR. Out of 201 isolates, 75.1 % (151/201) of the aeromonads possessed virulence genes (120=A. hydrophila and 31=Aeromonas veronii). The virulence gene pattern of aer/hly/fla was the most prominent with the prevalence of 12.6 %. The attenuated strain TZR7-2018 − showed reduced: colon size, multiplication rate, cell size and loss in; haemolysis, motility and capsule. Humoral responses increased gra- dually and reached maximum at day 28 in both attenuated and bacterin formulation given through in- traperitoneal (IP) injection and immersion (IM). A RPS of 82.3 %, 71.4 % and 85.1 %, were recorded to the attenuated vaccine given through IP and IM and bacterin provided through IP respectively. Therefore the attenuated strain TZR7-2018 − obtained through thermal continuous subculture technique and the bacterin proved to be efficacious and can serve as vaccine candidate.