DEPARTMENT OF MICROBIOLOGY

Medicinal plants have long served as a vital source of bioactive compounds with therapeutic potential against a wide range of microbial pathogens. The increasing incidence of antibiotic resistance among pathogenic bacteria has renewed scientific interest in exploring plant-derived compounds as alternative antimicrobial agents. Mimosa pudica (commonly known as the “Sensitive Plant” or “Touch-Me-Not”) is a medicinal herb traditionally used in folk medicine for its reported antimicrobial, anti-inflammatory, and wound-healing properties. This study evaluated the phytochemical constituents and antibacterial activity of hot and cold water extracts of Mimosa pudica against three clinically significant bacterial isolates: Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. Qualitative phytochemical screening revealed the presence of saponins, flavonoids, and tannins, while terpenoids and glycosides were absent. Tannins were moderately present (++) in both extracts, suggesting their possible contribution to the plant’s antimicrobial potential. The antibacterial assay demonstrated concentration-dependent inhibitory effects against all test organisms. The cold extract exhibited higher antibacterial activity than the hot extract, with Staphylococcus aureus showing a maximum zone of inhibition of 26.00 ± 5.29 mm at 2000 mg/ml, compared to 8.00 ± 5.29 mm for the hot extract. Similarly, the cold extract showed superior inhibition against Escherichia coli (27.33 ± 6.11 mm) and Pseudomonas aeruginosa (18.67 ± 7.57 mm) at the highest concentration. The Minimum Inhibitory Concentration (MIC) values revealed that Staphylococcus aureus was most susceptible to the cold extract (80 mg/ml), whereas Pseudomonas aeruginosa exhibited the least susceptibility (175 mg/ml for both extracts). The Minimum Bactericidal Concentration (MBC) results indicated that both extracts were bacteriostatic rather than bactericidal at the tested concentrations (2000 mg/ml). Comparative antibiotic sensitivity tests showed that the bacterial isolates displayed varying degrees of resistance and susceptibility to standard antibiotics, underscoring the need for effective plant-based alternatives. Overall, the findings demonstrate that Mimosa pudica possesses promising antibacterial activity, particularly in its cold water extract, likely due to the presence of tannins, saponins, and flavonoids. These results support the traditional use of Mimosa pudica in herbal medicine and suggest its potential as a natural source of antimicrobial compounds for combating bacterial infections, especially those caused by antibiotic-resistant pathogens. x

The antibacterial activities of thyme (Thymus vulgaris) against some Gram positive isolates such as Staphylococcus aureus and interococcus faecalis were assayed using ethanol extract. The agar-well and paper disc diffusion method were used to determine the inhibitory effect of the thyme leaves on the tested microorganism. The extract produced different zone of inhibition on the tested organism. The ethanol extract had the highest antibacterial effect against interococcus faecalis (21.6±3.51 mm) at 100% and Staphylococcus aureus has the lowest zone of inhibition (21.3±3.2l mm) at 100%, while at 75% Enterococcus faecalis had the highest zone of inhibition (l 7±2.64 mm) and Staphylococcus aureus has the lowest zone of inhibition (12.3±2.5l mm), while at 62% Enterococcus faecalis showed the highest zone of inhibition (12±3.46 mm) while Staphylococcus aureus has the lowest zone of inhibition (11.3±1.52 mm). The ethanol extract had the highest antibacterial effect against Staphylococcus aureus (20.6±4.04 mm) at 87% and Enterococcus faecalis has the lowest zone of inhibition (20.3±1.52 mm) at 87% while at 50% Staphylococcus aureus showed the highest zone of inhibition (6.33±1.15 mm) while Enterococcus faecalis has the lowest zone of inhibition (5±0 mm). Among these isolates, Enterococcus faecalis were highly sensitive to the thyme oil at different percentage (100%, 75%, 62%) while Staphylococcus aureus were little more sensitive to the thyme oil at 87% and 50% using the same solvent (ethanol). The increase in multidrug resistant strains of pathogenic microorganism has led to extensive phytochemical and pharmacological studies of Thymus vulgaris as an important source of medicinal substances which possess antibacterial properties and their effective medicinal application, as well as use in pharmaceutical, food and cosmetic industries

The study microbial analysis of a mixed fruit juice sample using brine as the preservative was carried with the aim of producing mixed fruit juice from the extracted juices of watermelon and pineapple, and also to determine the effect of different rations of brine solution in preserving the produced mixed fruit juice. The fruit juice from the watermelon and orange was extracted using the pressing and filtration technique while the mixed fruit juice was prepared by mixing different rations of orange and watermelon (80:20), orange and watermelon (30:70) and orange and watermelon (60:40). The brine solution was prepared by using different rations (10:90, 20:80, 40:60 and 60:40) of sodium chloride and calcium chlorides respectively. The effect of the different rations of the brine solutions on the microbiological and physiological properties of the mixed fruit juices was done using standard laboratory procedures. The overall acceptability of the different mixed fruit juices after day 7 of the experiment was found to be 45%, 35% and 70% for the orange and watermelon (80:20), orange and watermelon (30:70) and orange and watermelon (60:40) respectively. The results of the effect of the different concentration of the brine solutions for the preservation of the different rations of the extracted juice showed that mixtures ration orange and watermelon (60:40) was more stable in terms of microbial growth on the juice while the pH of the different juice rations was found to be slightly neutral at day 0 of the experiment and then acidic at day 7 of the experiment. The results of the effect of the different brine solutions on the microbial count of the juice mixture recorded no microbial growth in any of the treatments at day 7 of the experiment. This was attributed to the increased acidity of the juice at day 7 of the experiment. Findings from this study has shown that the juice mixture orange and watermelon (60:40) was found to be more stable in terms of the sensory, physiological and microbiological evaluation

Microbiological quality is of importance to public health as it directly relates to spoilage of fish and food poisoning. This study was aimed at evaluating bacteria isolates from smoked fish sold in various location in Ekosodin. The bacterial isolates were characterized and identified using morphological and biochemical methods. The percentage distribution and frequency of the isolates were evaluated using statistical method. From the result obtained in this study, the total heterotrophic bacterial count ranged from 3.22±1.5 log10cfu/g to 4.550228±1.00 log10cfu/g. Using the cultural, morphological and biochemical test results, the bacterial isolates obtained in this study were Escherichia coli, Staphylococcus aureus, Salmonella sp, Enterobacter sp, Pseudomonas sp and Shigella sp The frequent of the bacterial isolation showed that E.coil has the highest percentage of 30%. The bacteria is obtained from this study were all susceptible to few antibiotics namely perfloxacin,, amoxicillin, rocephin and ciprofloxacin but were resistant to ampiclox, zinnacef, sulfamethoxazole and gentamicin. In conclusion, this study has revealed that the level of microbial contamination of dry fish roducts could either be environmentally dependent. It also revealed fish contamination is a problem and consumption of uncooked smoked fish can be hazardous and should be avoided.

Spices are food supplements or food products commonly used as flavouring and colouring agents, preservatives and/or herbs in folk medicine. Murraya koenigii (Linn, Spreng), (Family-Rutaceae) is a type of spice commonly called Curry leaves found in tropical and sub-tropical region and cultivated in China, Australia and Nigeria. It known as efirin oso in Yoruba and marugbo sanyan in Hausa. The aim of this study was to access the antibacterial activities of Murraya koenigii against Salmonella and Shigella species. Samples of commercial Murraya koenigii leaves were analysed and their phytochemical, phytocomponents and proximate components were assayed using standadrd methods. Also antibacterial activities of the olant extracts were investigated using well-in-agar diffusion methods. Data obtained for the different parameters were subjected to statistical analysis using the analysis of variance. The results of the phytochemical analysis revealed the presence flavonoid (8.81 ± 0.09 mg/100g), tannins (20.28 ± 0.53 mg/100g) and phenolic (44.83 ± 1.18 mg/100g) in aqueous extracts and flavonoid (67.1 ± 0.49 mg/100g), tannins (55.5 ± 1.98 mg/100g) and phenolic (68.0 ± 1.40 mg/100g) in ethanolic extract. Gas Chromatography-Mass Spectrometry confirmed the presence of Dodocanoic acid (0.40%), Tridecanoic acid (0.69%), Decanoic acid (0.29%), Tetramethyl-2- hexadecon-1-01 (1.65%), ctadecanoic acid (0.45%), Hexadecanoic acid (1.04%), Phthalic acid (1.14%), n-Hexadecanoic acid (29.6%), Hexadecanol (3.35%), acconic acid (6.23%), Octacosane (2.78%), Squalene (2.52%), Tetratetracontane (3.18%) and Cholesterol (1.57%). Zone of inhibition of the aqueous leave extract of Murraya koenigii on Salmonella sp and Shigella sp ranged from 0.10 ± 0.00 - 1.37 ± 0.03mm while zone of ethanolic extract ranged from 0.10 ± 0.00 - 1.67 ± 0.03mm respectively. The Minimum Inhibitory Concentration ranged from 9.17 ± 2.20 - 45.0 ± 2.88 mg/ml for aqueous extract and 15.0 ± 7.64 - 90.0 ± 5.77 mg/ml for ethanolic extract. inimum actericidal Concentration (MBC) were negative in both aqueous and ethanolic extracts. The proximate analysis revealed the presence of Moisture (8.69 ± 0.52 %), Protein (19.73 ± 0.30%), Ash (1.95 ± 0.00 %), Fibre (4.31 ± 0.29 %), Lipid (6.53 ± 0.50 %) and carbohydrate (43.48 ± 1.72%). Shigella sp and Salmonella sp were resistant to septrin, ciprofloxacin, amoxicillin and perfloxacin and susceptible to sparfloxacin, augmentin and gentamycin with Salmonella sp having the highest multiple antibiotic resistance index of 0.5. The isolates were found to harbor plasmids. Plasmid profile of the bacterial isolates after curing showed that Shigella sp was totally cured while presence of visible bands was observed for Salmonella sp. signifying inherent resistance to antibiotics. The antibacterial activities observed in Murraya koenigii leaves extract is due to the presence of phytochemicals. The use of Murraya koenigii in folk medicine is therefore recommended

The handling of currency notes is an everyday activity that exposes them to various sources of microbial contamination. This study was carried out to evaluate the bacteriological quality of Nigerian currency notes collected from different sources banks, park, and petrol stations. A total of samples of different denominations (₦1000, ₦500, ₦200, and ₦100) were randomly collected from banks, park and petrol station and analyzed using standard microbiological procedures. The currency notes were swabbed, and the isolates were cultured on nutrient agar, MacConkey agar, and mannitol salt agar plates. The bacterial isolates were identified based on their phenotypical characteristics. the isolates were evaluated for their virulence factors and antibiotic susceptibility profile. The results revealed a high level of bacterial contamination on most of the notes examined, with isolates including loads compared to those from banks, possibly due to frequent handling and poor hygiene practices. The presence Staphylococcus aureus, Klebsiella pneumoniae. Notes obtained from petrol stations and park showed higher microbial of potential pathogens on currency notes indicates their role as fomites in the transmission of infectious diseases. This study emphasizes the need for improved public hygiene awareness, regular replacement of old and damaged notes, and the promotion of cashless transactions to reduce the risk of disease spread.

Fomites are generally considered as any inanimate object that can serve as a means of transferring pathogens to a new host. Table surfaces which are fomites can be a major source of spread of infectious diseases. The main aim of the study is to enumerate, isolate and identify bacteria from Environmental Management and Toxicology (EMT) students lecture tables at University of Benin as well as to determine the antimicrobial susceptibility test of the bacterial isolates. Samples were collected twice on a weekly basis using a sterile swab. Methods involved in the isolation and identification of the bacteria were serial dilution, Gram staining, biochemical test which include oxidase, catalase, indole, urease, sugar fermentation and potassium hydroxide test, as well as antimicrobial sensitivity test. The probable isolates identified were Staphylococcus aureus, E. coli, Klebsiella spp., Pseudomonas spp. and Enterobacter aerogenes, with the second week having a higher number of bacterial population and isolates. Unhygienic practices by the students accounts for these isolates.

Watermelon fruit is a suitable medium for the production of probiotic juice due to its nutritional content, high amounts of sugar and the lack of competing starter. However, its utilisation as a probiotic drink is under-utilized. This research was carried out to evaluate the viability of three Lactobacillus species in watermelon juice. Watermelon juice was freshly prepared, sterilized and inoculated under aseptic condition. Incubation was carried out at 4 oC and 28±2 oC and uninoculated juiceserved as controls at both temperatures. Samples of juice were obtained every 24 hr for 7 days and tested for parameters which include pH, titratable acidity (%), average titre value (cm3) and viable cell counts (cfu/ml). Sensory analysis of the probioticated juice was also carried out using the hedonic scale. The pH of the probioticated
juice was measured using a pH meter, titration methods were used to determine titratable acidity and average titre value while the pour plate method was used to determine viable cell count. A significant reduction in pH was observed in samples stored at 28±2 oC with LB1 having the highest reduction in pH (5.20±0.06 – 3.60±0.06) and LB3 having a slight reduction (5.20±0.12 – 3.70±0.12). There was rapid increase in average titre value at 28±2 oC with LB1 having the highest increase (5.00 - 15.16) and LB3 having the lowest average titre value (5.00 – 14.72 cm3). There was only a slight increase of titre values in samples stored at 4
oC. This led to a corresponding increase in titratable acidity for both Lactobacillus species; LB1 (0.32 – 0.99%) and LB3 (0.32 – 0.94%) at 28±2
oC. However, at 4 oC , a slight increase was observed for the three Lactobacillus species. At 28±2 oC, there was an observable increase in viable cell counts with LB1 having the highest mean count (0.03 x 10 8 – 168 x 108) and LB2 having the lowest mean count (0.03 x 108 – 123 x 10 8 cfu/ml). Samples stored at 4 oC had little or insignificant increase during production. Samples stored at 4 oC had a better acceptability in terms of taste, colour and appearance compared to those stored at 28±2
oC with LB1 having the poorest acceptability. There are several challenges to overcome in the probiotication of watermelon juice which include the survival of probiotics, storage temperature, and their effects on sensory attributes. Longer shelf-life study should be investigated in the future to evaluate the acceptability of this juice.

Abacteriological evaluation of Garri, a cassava product, one of the most popular foods derived from cassava fermentation, is a staple Nigerian food, its raw product Cassava (Mamihot esculenta Crantz), is a dicotyledonous perennial plant. It was conducted in five major markets in Benin City, Edo State. The aim and objectives of this study was to isolate bacteria from garri sold at different markets in Benin City, in order to determine the bacterial count of the garri samples, determine the species of bacteria resent in the garri samples and gain insights into the susceptibility of the isolated bacteria. Methodology utilized in this research study include: isolation of bacteria utilizing nutrient agar, a total of six isolates (bacteria) with a sample size of five (Olukwu, Uselu, ingRoad, NewBenin, and Mami ) were examined. The mean total heterotrophic bacterial count ranged from (7.00- 7.91±2.0 log10cfu/g) in the five different markets and the pour plate method was employed in achieving the colony count in the Garri
samples. The primary bacteria strains identified after observing the cultural, morphological and biochemical test results, included Pseudomonas spp., Bacillus spp., Escherichia coli., Streptococcus sp., Micrococcus spp., and Staphylococcus spp. These bacterial strains were prevalent in Garri samples from all five markets, indicating potential contamination during processing or handling. The bacteria obtained from this study were all susceptible to the antibiotic, perfloxacin, but resistant to the others, namely, amoxicillin, rocephin, ciprofloxacin, ampiclox, zinnacef, erythromycin and gentamicin. The high occurrence of bacteria in Garri across these markets could be attributed to suboptimal sanitation conditions, processing techniques, materials used, and inadequate waste management practices. It is recommended that producers and retailers in Benin implement rigorous hygiene measures in preparation and packaging to ensure food safety and the protection of consumers.

The need for an alternative to inorganic fertilizer is on the increase owing to the drawbacks associated with inorganic fertilizers. This study was therefore carried out to evaluate the bacteriological profile of digestates from different waste streams and the ability of the isolates to promote the growth of plants. Standard bacteriological methods were used to analyze digestates from different waste streams. Total heterotrophic bacterial count was obtained using pour plate method. The cultural, morphological and biochemical characteristics of the bacterial isolates were evaluated using standard differential media along with appropriate reagents. Plant growth promoting capacity of the isolates were evaluated using standard protocols for nitrogen fixation, phosphate solubilization, indole acetic acid and ammonia production. The results obtained from this study revealed that the total heterotrophic bacterial count (Log10 cfu/g) of digestate from different waste streams had values, which ranged from 4.91±0.02 for cattle rumen digestate to 4.41±0.03 for a combination of cattle rumen fruit and food waste digestate. The cultural, morphological and biochemical characteristics of bacterial isolates revealed the presence of Enterobacter cloacae, Escherichia coli, Pseudomonas aeruginosa, Salmonella enterica, Proteus mirabilis and Bacillus cereus. The distribution of bacterial isolates in the different waste streams revealed that E. coli was present in all digestates obtained from different waste streams. All bacterial isolates were found to possess plant growth promoting properties with 100 % capacity for nitrogen fixation and phosphate solubilization. While 66.7 % of the isolates had the ability to produce ammonia and indole acetic acid. The phosphate solubilization index of the isolates revealed that E. coli (5.97) and P. aeruginosa (5.76) had the highest solarization index amongst all tested bacteria in the study