Anti-Salmonella activity of metabolites from African soldier termites, Macrotermes bellicosus

Background: The global emergence and rapid dissemination of multidrug resistant Salmonella strains necessitate research to find new antimicrobials that will effectively be used against these pathogens. In the present study, anti-Salmonella activity of metabolites from African Soldier Termites, Macrotermes bellicosus was demonstrated and subsequently compared with a potent antibiotic, ciprofloxacin.Materials and Methods: N-hexane, ethylacetate, methanol and aqueous extracts of metabolites from the M. bellicosus were assayed for anti-Salmonella activity using the agar dilution method in the determination of the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The inhibitory activities of the extracts were compared to ciprofloxacin (256μg/ml). Also, the bioactive components of the extracts were determined using standard techniques.Results: At 4000 μg/ml, N-hexane extract inhibited the growth of Salmonella Typhi, S. Paratyphi A, B and C while ethylacetate extract was able to inhibit S. Paratyphi A and C. Methanolic and aqueous extracts at the same concentration were unable to inhibit these strains of Salmonella. Furthermore, our findings revealed that the MIC of ethylacetate extract was 2000μg/ml for S. Paratyphi A and B, 250μg/ml for S. Typhi, and 125μg/ml for S. Paratyphi C. Also, the MIC of hexane extract was 4000μg/ml for S. Paratyphi B, 2000 μg/ml for S. Paratyphi C, 500μg/ml for S. Typhi and 250μg/ml for S. Paratyphi A respectively. The screening of bioactive components revealed the presence of cardiac glycosides and alkaloids.Conclusion: Our results provide evidence of anti-Salmonella action of metabolites from African Soldier Termites, M. bellicosus. N-hexane and ethylacetate extracts of M. bellicosus may be explored as novel antimicrobials for the treatment of typhoid and paratyphoid fevers thereby reducing the pressure exerted on available antibiotics.Keywords: Salmonella, antimicrobials, insects, extract

Warmed-over flavour profiles, microbial changes, shelf-life and check-all-that-apply sensory analysis of cooked minced pork treated with varying levels of Moringa oleifera leaf and root powder

DATA AVAILABILITY STATEMENT : Data will be made available on request.This study investigated warmed-over flavour profiles, microbial changes, shelf-life and sensory characteristics of minced cooked pork treated with Moringa oleifera (M. oleifera) root and leaf powder during refrigerated storage at 4 °C. A total of 8 treatments (control = no antioxidant; 0.5ML = 0.5% M. oleifera leaf; 1ML = 1% M. oleifera leaf; 0.5MR = 0.5 % M. oleifera root; 1MR = 1% M. oleifera root; 0.5MLR = 0.5% M. oleifera leaf and root mixed; 1MLR = 1% M. oleifera leaf and root mixed; BHT = 0.02% butylated hydroxytoluene) were evaluated. The minimum inhibitory concentration (MIC) of the plant extracts against the test bacteria was determined using the serial dilution in 96 well microtiter plates technique. Warmed-over flavour profiles were determined using the test for carbonyls assay where hexanal was used as a marker for warmed-over flavour. The check-all-that-apply sensory tool was used to characterise minced cooked pork treated with different antioxidants according to warmed-over flavour taste and odour intensities. The results showed that the antibacterial assay of the extracts exhibited a broad-spectrum of activity against the tested bacteria. The leaf extracts demonstrated better activity against both gram-negative and gram-positive bacteria, with most of the MICs at less than 1 mg/mL, while the root performed better against gram-negative bacteria compared to gram-positive bacteria. There was a significant rapid increase in the warmed-over flavour profiles of the control compared to the M. oleifera and BHT treated pork. The pork samples which had M. oleifera leaf, root, and their combination at inclusion levels of 1% and 0.5% displayed lower warmed-over flavour profiles that fell in the range (1.0–1.46 mg hexanal/100g fat) throughout the storage period. Consumer sensory evaluation revealed that pork samples treated with the highest inclusion level (1%) of the M. oleifera leaf powder received the lowest consumer rating scores for appearance. Based on these results, adding M. oleifera leaf and root powder can decrease warmed-over flavour development and improve the shelf-life of processed pork. Furthermore, the incorporation of M. oleifera root powder can potentially be more acceptable to consumers because of its colour compared to the leaf, which gives the product a green colour that may not be pleasant for some consumers. This suggests that the inclusion of the root powder at 1% may be well accepted for consumption by consumers.The National Research Foundation South Africa.http://www.cell.com/heliyonCentre for the Advancement of Scholarshi