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Objective: This study investigated the antibacterial activity of the acetone, methanol, and ethanol leaf extracts of Azadirachta indica and Psidium guajava against methicillin resistant Staphylococcus aureus (MRSA) and vancomycin resistant Staphylococcus aureus (VRSA) strains as well as the antimicrobial activity of some conventional antibiotics on these multidrug resistant organisms.Methods: MRSA and VRSA strains were obtained from the culture collection unit of a tertiary hospital in Ebonyi State, Nigeria. The test organisms and the plant extracts were processed using standard microbiology techniques. Kirby-Bauer disk diffusion technique was used to determine the antimicrobial susceptibility profile of the MRSA and VRSA strains to some conventionally used antibiotics; and the antibacterial activity of the plant extracts was evaluated using agar well diffusion technique with three solvents: ethanol, methanol and acetone.Results: It was revealed in this study that the extracts of A. indica and P. guajava demonstrated some level of antimicrobial activity against the test organism at concentrations of 100 mg/ml and 50 mg/ml. Compared to the conventional antibiotics used, the antibiotics showed better antimicrobial activity against the test organisms than the plant extracts which was least active against the MRSA and VRSA strains. Conclusions:Though the A. indica and P. guajava extracts showed some appreciable antimicrobial activity against the MRSA and VRSA strains, the conventional antibiotics produced better antimicrobial action against these multidrug resistant bacteria. The search for novel compounds with putative antimicrobial activity should be stepped up since plants holds the potential for discovering novel drugs.

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Lactobacillus spp. belongs to a class of bacteria known as lactic acid bacteria. This classification is because they are known to produce lactic acid as a major by-product of their metabolic activities. Most Lactobacillus spp. are generally regarded as safe (GRAS) bacteria. They also produce a bio-polymeric substance known as exopolysaccharide (EPS). The EPS are popular because of their wide potential medical and industrial applications. The wide application of the EPS in medicine and industry necessitates optimal production and recovery of these polymeric substances produced by Lactobacillus spp. In this book chapter, we aim to comprehensively discuss Lactobacillus EPS, its inherent properties, potential pharmaceutical and industrial applications. We also point to its contribution towards the achievement of the 3rd and 9th components of the United Nations Sustainable Development Goals which are to establish good health and wellbeing and to promote industrialization, innovation, and infrastructure respectively.

Antimicrobial activity against entero-pathogens and tolerance to acid stress are crucial characters of probiotic bacteria. Lactobacillus spp. isolates were phenotypically characterized using colony observation, catalase test and Gram stain reaction. The pH (1.5, 2.5 and 3.5) tolerance of each isolate was evaluated at 0 and 4 h. The antibacterial activities of the isolates were tested against pathogenic strains of Bacillus spp., Escherichia coli, Pseudomonas aeruginosa, Salmonella typhimurium and Staphylococcus aureus. Among the isolates screened, 20 were Gram positive and catalase negative. In an agar well diffusion, isolate O 4 resulted in the highest inhibition zone diameter, 13 mm against P. aeruginosa while isolates OK 4 , UK 1, P 2 , P 3 and P 4 did not produce any inhibition zones against any of the pathogens tested. Isolate Y 1 showed the broadest inhibitory activity against the pathogens tested inhibiting all the pathogens tested except S. typhimurium. The pH tolerability studies showed that the isolates proliferated more at lower acidic pH: 1.5 > 2.5 > 3.5. Food products containing Ogiri, Ukpaka, Okpeye, Akamu and Yoghurt provides useful sources of probiotic bacteria.