Thesis (MScFoodSc)--Stellenbosch University, 2019. | ENGLISH ABSTRACT: Irrigation water has been identified as one way by which fresh produce can become contaminated with pathogens. This is a concern in South Africa, where some rivers used for the irrigation of fresh produce often carry pathogens. In this regard, treating river water prior to irrigation is important to reduce the possible risk of foodborne disease outbreaks associated with the consumption of contaminated produce. Ultraviolet (UV) irradiation can be used to decontaminate water and has been shown to be effective against waterborne pathogens. Knowledge gaps, however, still exist regarding the minimum effective UV dose required to effectively inactivate different waterborne pathogens. The aim of this study was, therefore, to evaluate the disinfection efficacy of low-pressure (LP) UV on river water. Escherichia coli (E. coli) strains including three Shiga-toxin producing Escherichia coli (STEC) strains were exposed to five different UV doses (20, 30, 40, 50 and 60 mJ.cm-2) in sterile Ringer’s solution. Variation in UV sensitivity among strains was observed at all doses. Log reductions ranged between 3.6 - 4.4 log for the lowest dose (20 mJ.cm -2). Environmental strains were more UV resistant than the ATCC strain. Based on these results, the influence of water quality on UV irradiation efficacy was investigated by inoculating a resistant environmental STEC strain (STEC 210) into both autoclaved river water and Ringer’s solution. Results showed that water quality parameters did not negatively influence UV disinfection efficacy provided the same dose was applied. The disinfection efficacy of UV (40 and 60 mJ.cm-2) irradiation was then investigated against river water (Eerste, Krom and Plankenburg rivers). The Eerste River showed E. coli levels falling below the recommended irrigation guideline limit. The Krom River also showed low E. coli levels, but a once-off STEC detection, as well as the consistent occurrence of ESBL producing Enterobacteriaceae was observed. The Plankenburg River showed the highest E. coli levels and consistent detection of STEC and ESBL producing Enterobacteriaceae. UV irradiation of the Eerste and Krom rivers resulted in undetectable levels of Enterobacteriaceae, total coliforms and E. coli. A targeted three log reduction was achieved following disinfection of the Plankenburg River water at both UV doses. This resulted in water within acceptable irrigation standards. A dose of 40 mJ.cm-2 was, however, ineffective against STEC. Repair of all indicator populations was observed and was less than 1% at both UV doses (40 and 60 mJ.cm-2) but, was less at the higher dose (60 mJ.cm-2). Lastly, the effects of combining pine biochar filtration with UV irradiation was investigated on river water. The combination treatment resulted in improved UVT% and better UV irradiation efficacy of microorganisms. Overall, UV irradiation showed potential in producing water of acceptable standard for fresh produce irrigation in terms of the E. coli load. However, UV efficacy against other important waterborne pathogens such as Salmonella was not investigated. It is recommended that, the disinfection efficacy of UV against these pathogens, be investigated in future. Acceptable levels of these pathogens in irrigation water should also be explored, to make guideline recommendations. | AFRIKAANSE OPSOMMING: Besproeiingswater is geïdentifiseer as een manier waarop vars landbouprodukte met patogene besmet kan word. Dit is van belang in Suid-Afrika waar sommige riviere wat vir besproeiing van vars produkte aangewend word dikwels patogene bevat. In hierdie verband is dit belangrik om rivierwater voor besproeiing te behandel om sodoende die moontlike risiko van voedseloordraagbare siektes wat met die inname van besmette produkte geassosieer word, te verminder. Ultraviolet (UV) bestraling kan gebruik word om water te ontsmet en daar is gevind dat dit effektief is teen watergedraagde patogene. Kennisgapings bestaan egter steeds ten opsigte van die minimum effektiewe UV dosis wat benodig word om verskillende watergedraagde patogene effektief te inaktiveer. Die doel van hierdie studie was dus om die ontsmettingseffektiwiteit van lae druk (LP) UV bestraling op rivierwater te evalueer. Escherichia coli (E. coli) isolate, insluitend drie Shiga-toksien produserende Escherichia coli (STEC) isolate, is blootgestel aan vyf verskillende UV dosisse (20, 30, 40, 50 en 60 mJ.cm-2) in steriele Ringer’s oplossing. Variasie in UV sensitiwiteit is tussen isolate waargeneem teen alle dosisse. Log reduksies het gewissel tussen 3.6 - 4.4 log vir die laagste dosis (20 mJ.cm -2). Omgewingsisolate was meer UV bestand as die ATCC isolaat. Gebaseer op hierdie resultate is die invloed van waterkwaliteit op UV bestralingseffektiwiteit ondersoek deur ‘n UV weerstandbiedende omgewing-STEC isolaat (STEC 210) in beide geoutoklafeerde rivierwater en Ringer’s oplossing te inokuleer. Die resultate het gewys dat waterkwaliteit parameters nie UV ontsmettingseffektiwiteit negatief beïnvloed nie mits die regte dosis toegepas is. Die ontsmettingseffektiwiteit van UV (40 en 60 mJ.cm-2) bestraling is daarna ondersoek in rivierwater (Eerste, Krom en Plankenburg riviere). Die Eerste rivier het E. coli vlakke getoon wat voldoen aan die aanbevole besproeiingsriglyn limiete . Die Krom rivier het ook lae E. coli vlakke getoon, maar ‘n eenmalige STEC teenwoordigheid, sowel as die konsekwente teenwoordigheid van ESBL produserende Enterobacteriaceae is waargeneem. Die Plankenburg rivier het die hoogste E. coli vlakke getoon asookkonsekwente teenwoordigheid van STEC en ESBL produserende Enterobacteriaceae. UV bestraling van die Eerste en Krom Riviere het gelei tot onopspoorbare lae vlakke van Enterobacteriaceae, totale kolivorme en E. coli. ‘n Geteikende drie log reduksie is behaal na behandeling van die Plankenburg Rivier water met beide UV dosisse. Dit het daartoe gelei dat die water binne aanvaarbare besproeiing standaarde val. ‘n Dosis van 40 mJ.cm-2 was egter oneffektief teen STEC. Die herstel van alle indikatorpopulasies is waargeneem en was minder as 1% by beide UV dosisse (40 en 60 mJ.cm-2), maar was minder by die hoër dosis (60 mJ.cm-2). Laastens is die effek van ‘n kombinasie van denneboom “biochar” filtrasie met UV bestraling op rivierwater ondersoek. Die kombinasie-behandeling het gelei tot ‘n verbeterde UVT% en beter UV bestralingseffektiwiteit teen mikroörganismes. In geheel toon UV bestraling die potensiaal om water van ‘n aanvaarbare standaard vir vars produk besproeiing, in terme van die E. coli lading, te produseer. UV bestralingseffektiwiteit teenoor ander belangrike watergedraagde voedselpatogene, soos Salmonella, is nie ondersoek nie. Daar word aanbeveel dat die ontsmettingseffektiwiteit van UV teenoor hierdie patogene in die toekoms ondersoek word. Aanvaarbare vlakke van hierdie patogene in besproeiingswater moet ook bepaal word om sodoende riglyn-aanbevelings te maak.

In this study, the correlation between 526 prospective teachers&rsquo: beliefs about education for sustainable development (ESD) and their perceptions of self-efficacy and abilities to focus on solutions was addressed. This descriptive study found that prospective teachers had strong beliefs about ESD. In terms of the &ldquo:beliefs about the implementation of sustainable development&rdquo: and &ldquo:beliefs about the limitation of sustainable development&rdquo:, the prospective teachers who are studying at the faculty of education had stronger beliefs than those enrolled in the Pedagogical Formation Certificate Program. In addition, fourth-year prospective teachers and those perceiving themselves as showing good academic performance had stronger beliefs about ESD. Also, participants&rsquo: beliefs about ESD were found to be related to their abilities to focus on solutions and their perceptions of self-efficacy. Additionally, our study found that perceptions of self-efficacy significantly predicts the ability to focus on solutions and beliefs about ESD (29%). One of the limitations of our study is that our findings can be generalized only to a limited extent. Furthermore, further research is needed to validate the predictive variables that have arisen. Finally, longitudinal and experimental research that use qualitative analysis techniques is needed to investigate the implications of the results for professional improvement and to find out what sort of sustainable education practices there are in different education levels.

International audience

Low yield of maize/cassava intercrop is majorly due to some identified constraints like poor density of component crops, inappropriate application of fertilizer and weed infestation. This study was conducted in Otukpo-Icho, southern Guinea savanna of Nigeria and Igbariam, Humid Tropical Forest of Nigeria during 2018/2019 cropping season to determine the weed control efficiency and performance of cassava/maize intercrop. The trials were laid out as randomized complete block design in a factorial arrangement with four replications. Cassava (TME 419) was planted as 1m x 0.8 m (12,5000 plants/ha) while maize (SAMMAZ 35) seeds were sowed at 1m x 0.5 m (20, 000 plants/ha) and 1m x 0.25 m (40, 000 plants /ha). Fertilizer was applied as 90 kg N,20 kg P, and 40 kg K /ha versus 75 kg N, 20 kg P and 90 kg K /ha. Data were collected on plant height, number of leaves and stem girth at 3,6 and 8WAS for maize while 3, 6 and 9 MAP for cassava. Weed density and weed biomass were estimated at 4, 8, 12,16 and 20 WAP. All the data collected were subjected to analysis of variance (ANOVA) using Genstat statistical package and significant were separated using LSD at P<0.05. The results showed Ageratum houstonianum Mill. (96.29), Cyperus rotundus Linn. (35.84) and Digitaria horizontalis Willd. (16.95) were prevalent in Igbariam while Lindernia crustacea (L.) F. Muell. (59.35), Stachytapheta jamaicensis (Linn.) Vahl. (37.30), Oldenlandia corymbosa Linn. (27.33), were prevalent in Otukpo-icho site. Weed density peaked at 8WAP.Intercropped plots had xi significantly lower weed infestation. The higher maize grains yield (3.69 - 4.25 ton/ha) obtained in 12,500 + 40,000 plants/ha maize + 90:20:40 kg/ha of NPK. Higher root yield (22.34 ton/ha) recorded in intercrop plots obtained in 12,500 plants/ha cassava + 20,000 pts /ha maize + 75:20:90 kg/ha of NPK. This study recommended a broad spectrum herbicide for Igbariam and Trazines mixture for Otukpo-Icho and any supplementary weed control strategy necessary targeted at the peak of weed emergence (8WAP). If maize is main crop, famer should plant 12,500 plants/ha of cassava and 40,000 plants/ha of maize with application of 90:20:40 kg/ha of NPK. If cassava is main crop, farmer should plant 12,500 plants/ha of cassava and maize 20,000 plants/ha with application of 75:20:90 kg/ha of NPK both suppresses weed.

International audience

The objectives of the study were to assess the efficacy of commercial PHPs on specific pathogen free (SPF) shrimp (Penaeus monodon) post larvae nursing in tanks.

Aphids (Myzus persicae) are one of the most important pest of celery, which is cultivated for its fleshy leafstalks, seeds and essential oil. Aphids suck sap from the plant and reduce yield. Also, they transmit viral diseases and contaminate celery produce with honeydew. Some safer insecticides namely flonicamid 50 WG @ 150, 175 and 200 g/ha, imidacloprid 200 SL @ 75, 100 and 125 ml/ha, thiamethoxam 25 WG @ 75, 100 and 125 g/ha and acetamiprid 20 SP @ 37.5, 50 and 62.5 g/ha were evaluated for their efficacy against aphids. Population of aphids per inflorescence before spray varied from 12.03 to 13.20. All the treatments were significantly better than control. On all observation dates flonicamid @ 175 and 175 and 200 g/ha, imidacloprid @ 100 and 125 ml/ha, thiamethoxam @ 100 and 125 g/ha, acetamiprid @ 50 and 62.5 g/ha were statistically better in reducing aphid population than other treatments. Highest seed yield of 11.30 q/ha was obtained with flonicamid50 WG @ 200 g/ha which was statistically at par with imidacloprid 200 SL @ 100 and 125 ml/ha, thiamethoxam 25 WG @ 100 and 125 g/ha and acetamiprid 20 SP @ 50 and 62.5 g/ha and flonicamid50 WG @ 175 g/ha.

The field experiments were conducted during Kharif 2016 and 2017 at Research Farm, College of Agriculture, RVSKVV, Gwalior (M.P.) to study the effective herbicide/combination of herbicides to control the problematic weeds in greengram (Vigna radiata). The experiments were laid out with ten treatments, viz. quizalofop-p-ethyl 50, 75 and 100 g/ha PoE, fenoxaprop-p-ethyl 100 g/ha PoE, pendimethalin 1000 g/ha pre-emergence (PE), pendimethalin + imazethapyr (RM) 750 and 1000 g/ha PE, imazethapyr + imazamox (RM) 80 g/ha PoE, two hand weeding at 20 and 40 DAS and weedy check in a randomized block design. The combination of imazethapyr + imazamox (RM) 80 g/ha applied as postemergence was found to be very efficient in controlling the dominant grassy as well as broad-leaved weeds and produced maximum seed yield (993 kg/ha), and was at par with two hand weedings at 20 and 40 DAS (983 kg/ha) and combination of pendimethalin + imazethapyr 750 g/ha and 1000 g/ha PE (844 and 758 kg/ha, respectively). Application of imazethapyr + imazamox (RM) 80 g/ha PoE resulted in the highest B:C ratio (3.03), and net returns, fb pendimethalin + imazethapyr 750 g/ha PE and two hand weeding at 20 and 40 DAS.

Furanones are analogues of acylated homoserine lactones with proven antifouling activity in both Gram-positive and Gram-negative bacteria though the interference of various quorum sensing pathways. In an attempt to find new strategies to prevent and control Listeria monocytogenes biofilm formation on stainless steel (SS) surfaces, different concentrations of six synthetic furanones were applied on biofilms formed by strains isolated from food, environmental, and clinical sources grown onto AISI 316 SS coupons. Among the furanones tested, (Z-)-4-Bromo-5-(bromomethylene)-2(5H)-furanone and 3,4-Dichloro-2(5H)-furanone significantly (p < 0.05) reduced the adhesion capacity (>1 log CFU cm−2) in 24 h treated biofilms. Moreover, individually conducted experiments demonstrated that (Z-)-4-Bromo-5-(bromomethylene)-2(5H)-furanone was able to not only significantly (p < 0.05) prevent L. monocytogenes adhesion but also to reduce the growth rate of planktonic cells up to 48 h in a dose-dependent manner. LIVE/DEAD staining followed by epifluorescence microscopy visualisation confirmed these results show an alteration of the structure of the biofilm in furanone-treated samples. Additionally, it was demonstrated that 20 µmol L−1 of 3,4-Dichloro-2(5H)-furanone dosed at 0, 24 and 96 h was able to maintain a lower level of adhered cells (>1 log CFU cm−2; p < 0.05). Since furanones do not pose a selective pressure on bacteria, these results represent an appealing novel strategy for the prevention of L. monocytogenes biofilm grown onto SS. | This research was financially supported by the Spanish Ministerio de Ciencia, Innovación y Universidades [SOLISTA, AGL2016-78549]. | Peer reviewed

Leishmaniasis is one of the most important neglected diseases worldwide. It is a life-threatening disease and causes significant morbidity, long-term disability, and early death. Treatment involves disease control or use of intervention measures, although the currently used drugs require long-lasting therapy, and display toxicity and reduced efficacy. The use of natural products isolated from plants, such as lapachol, an abundant naphthoquinone naturally occurring in South American Handroanthus species (Tabebuia, Bignoniaceae), is a promising option for the treatment of leishmaniasis. In this study, we investigated the leishmanicidal activity of lapachol in vitro and in vivo against Leishmania infantum and L. amazonensis, causative agents of visceral and cutaneous leishmaniasis, respectively. Low cytotoxicity in HepG2 cells (3405.8 ± 261.33 μM), good anti-Leishmania activity, and favorable selectivity indexes (SI) against promastigotes of both L. amazonensis (IC50 = 79.84 ± 9.10 μM, SI = 42.65) and L. infantum (IC50 = 135.79 ± 33.04 μM, SI = 25.08) were observed. Furthermore, anti-Leishmania activity assays performed on intracellular amastigotes showed good activity for lapachol (IC50 = 191.95 μM for L. amazonensis and 171.26 μM for L. infantum). Flow cytometric analysis demonstrated that the cytotoxic effect of lapachol in Leishmania promastigotes was caused by apoptosis-like death. Interestingly, the in vitro leishmanicidal effect of lapachol was confirmed in vivo in murine models of visceral and cutaneous leishmaniasis, as lapachol (25 mg/kg oral route for 24 h over 10 days) was able to significantly reduce the parasitic load in skin lesions, liver, and spleen, similar to amphotericin B, the reference drug. These results reinforce the therapeutic potential of lapachol, which warrants further investigations as an anti-leishmaniasis therapeutic.