Browsing by Author "Mzula, Alexanda"

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Antibiotic-resistant microbial populations in urban receiving waters and wastewaters from Tanzania
(Elsevier, 2023) Ripanda, Asha; Rwiza, Mwemezi; Nyanza, Elias; Miraji, Hossein; Bih, Numfor; Mzula, Alexanda; Mwega, Elisa; Njau, Karoli; Vuai, Said; Machunda, Revocatus
Antimicrobial resistance against certain medications in the pathogenic microbial community is globally increasing due to the continual discharge and disposal of pharmaceuticals in the environment. The phenomenon resulted in significant antibiotic resistance among several exposed Enterobacteriaceae species, with wastewater treatment plants (WWTPs) and rivers serving as significant reservoirs. Despite antibiotic resistance being a tragedy, particularly in treating diseases by using antibiotics, local and regional studies indicating the severity, resistant species and the molecular level insight into these pathogens are scarce, thus requiring immediate intervention. This study, therefore, investigated wastewater from wastewater treatment ponds and receiving waters for the presence of resistant pathogens through phenotypical and molecular approach screening of their genes. Among the 57 analyzed samples, 18 (67%, n = 27) isolates of Klebsiella spp.., 4 (80%, n = 5) isolates of Proteus spp., 1 (100%, n = 1) of isolated Pseudomonas aeruginosa and 6 (18%, n = 34) of E. coli found were resistant to at least 1 among the tested antibiotics. E. coli had an 83% higher proportion of multi-drug resistance (MDR) than Klebsiella spp.., which had 68.5%, and no MDR was shown by P. aeruginosa isolates. Among the 20 bacterial isolates of antibiotic-resistant genes, showed that E. coli harboured 39%, followed by 22% of Klebsiella spp. Eleven (11) isolates of these 20 (55%) contained sulphonamides resistant genes: Sul 1 (n = 4) and Sul 2 (n = 7). Ten (10) isolates (50%) contained the tetracycline-resistant genes in which 4 isolates showed the Tet A, Tet B – 1 and 5 isolates contained Tet D. β-lactamases (bla CTX-M and bla SHV) were found in 7 isolates (35%). The existence of these antibiotic-resistant species in the urban receiving and wastewater presents a threat of transmission of diseases to humans and animals that are not cured by the existing medications, jeopardizing public health safety.
Characterization of aeromonads and development of vaccine candidate from aeromonas hydrophila isolated from tilapia fish farms in Tanzania
(NM-AIST, 2020-06) Mzula, Alexanda
Tanzania produces less than half of the country annual demand in fish. Therefore, there is an urgent need to produce more fish, particularly through fish farming. However, aeromonads infections cause major lose in aquaculture worldwide and especially in developing countries, including Tanzania, lacking advanced capacity for fish disease control and prevention. Poor fish farming management practices, lack of data on prevalence, emergence of resistances to commonly used drugs, drug residues and limited capacity to control aeromonads bacterial infections emerged as major health problems in fish farming in Tanzania. This study aimed to characterise the aeromonads species circulating in fish farms and then develop a monovalent vaccine candidate from selected prevalent aeromonads specie for supporting tilapia fish farming improvement in Tanzania. A cross sectional study was conducted in Ruvuma, Mbeya, Iringa and Kilimanjaro regions between February 2017 and October 2018. A questionnaire was administered to 32 selected fish farmers to explore their knowledge on pond, fish health and diseases management practices. The results showed that the selected farmers had limited knowledge on pond, fish health and disease management practices. Onfarm training on the same to these farmers would improve their knowledge. A total of 816 whole fish samples were aseptically collected from these 32 fish farms to detect and identify aeromonads using molecular methods in order to establish the prevalence and characterise their virulence properties. The overall prevalence of 24.6% was recorded. Seventy five percent of the isolates had virulence genes of varying combinations and the in-vivo study showed high mortality (98.3%) to isolates with more virulence genes indicating their capacity to establish disease in a favourable environment. The Aeromonas hydrophila strain TZR72018 was selected and attenuated using a novel thermo-continuous sub-culturing method to develop a vaccine candidate. The experimental study was carried out to assess its protective efficacy. The results showed that the vaccine candidate had acceptable protective efficacy of 82.3% and 71.4% when given through intraperitoneal injection (IP) and immersion (IM); respectively. To the best of my knowledge this study reports the development of thermoattenuated and stabilized A. hydrophila vaccine candidate for the first time in Tanzania or elsewhere.
Current State of Modern Biotechnological-Based Vaccines for Aquaculture: A Systematic Review.
(Hindawi, 2019-07-29) Mzula, Alexanda; Wambura, Philemon; Mdegela, Robinson; Shirima, Gabriel
This systematic review describes what "the cutting edge vaccines for 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 -barrels were shown to be a potential antigenic entity for 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 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 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).
Phenotypic and molecular detection of Aeromonads infection in farmed Nile tilapia in Southern highland and Northern Tanzania
(Elsevier Ltd., 2019-08) Mzula, Alexanda; Wambura, Philemon; Mdegela, Robinson; Shirima, Gabriel;
Present status of aquaculture and the challenge of bacterial diseases in freshwater farmed fish in Tanzania; A call for sustainable strategies
(Elsevier, 2020-07-07) Mzula, Alexanda; Wambura, Philemon; Mdegela, Robinson; Shirima, Gabriel
Aquaculture provides significant contributions to household food security, as the capture of wild fish from lakes, dams, and oceans do not meet the current demand for animal protein in Tanzania. Sustainable aquaculture requires well-established regulatory systems and extension services for good pond management practices and maintaining fish health by fish farmers. Fish farming is practiced widely in Tanzania, from small-to large-scale ponds and these farming systems are moving from extensive normal operations (low input demand) to intensive farming (high input demand). However, the industry is largely still operating at a subsistence level with low production. Bacterial infections have been occurring in these fish farms and will continue to be an issue of concern into the future. This review highlights the current challenges, successes, and prospects towards a sustainable aquaculture industry in Tanzania, including: limited extension services mirroring the limited knowledge by farmers regarding pond management practices; the inadequacy of funds to carry out fish disease research or implement a surveillance system; little expertise in fish disease diagnosis and treatment; and poor management options. To minimize disease outbreaks and optimize production in the future, we suggest a strengthening of extension services, augmented with on-farm knowledge transfer. Emphasis should be on pond management practices and fish disease management; the creation of a well-functioning fish disease surveillance system; and strengthening collaborative research on aquaculture between the government research institutions and academia. Establishing small cooperative fish farmer groups within the Aquaculture Association of Tanzania (AAT) for easy access to information is also recommended.
Virulence pattern of circulating aeromonads isolated from farmed Nile tilapia in Tanzania and novel antibiotic free attenuation of Aeromonas hydrophila strain TZR7-2018
(Elsevier B.V., 2020-07) Mzula, Alexanda; Wambura, Philemon; Mdegela, Robinson; Shirima, Gabriel
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 inactivation from the same parent strain. Humoral responses were assayed using quantitative serological agglutination 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 gradually and reached maximum at day 28 in both attenuated and bacterin formulation given through intraperitoneal (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.