Evaluation of in-vitro interactions of streptomyces antibiotic substances and standard antibiotics against sensitive and resistant bacteria by activity index profile

Evaluation of the combined in-vitro antibacterial activities of Streptomyces antibiotic substances (UY1 – UY9) produced by Streptomyces species isolated from soil and standard antibiotics: ampicillin (AMP), tetracycline (TET) and chloramphenicol (CHL) against bacterial isolates: Staphylococcus aureus (SA), coagulase-negative Staphylococcus aureus (CONSA), methicillin–resistant Staphylococcus aureus (MRSA), Bacillus subtilis (BS), Streptococcus pnueumoniae (SP), Escherichia coli (EC), Pseudomonas aeruginosa (PA), Salmonella typhimurium (ST), Shigella dysentariae (SD) and Vibrio cholerae (VC) was carried out at 1 x MIC by the modified agar – well diffusion technique. The inhibitory zones of the interactions were assessed by the activity index profile (AIP), to evaluate the nature of the interactions. The combination of the agents at 1 x MIC against the test organisms showed qualitative inhibitory activity within the range (10.0 – 25.0 mm). The comparative assessment of the inhibitory activities by AIP, indicated synergism, additivity, indifferent and antagonism interactions. The standard definitions of synergy, additivity, indifference and antagonism were utilized in the assay. All the antimicrobial combinations demonstrated some degrees of synergism against the test organisms mostly the Gram-positives for ampicillin, and both Gram-positives and Gram–negatives for chloramphenicol; and lessly, tetracycline with infrequent antagonism. Conversely, antagonism was predominantly demonstrated in the combinations with tetracycline, while synergism was infrequent.Keywords: In-vitro interactions, Streptomyces Antibiotic Substances, Sensitive and Resistant Bacteria, Activity Index Profil

Larvicidal efficacy of ethanol leaf and seed extracts of Picralima nitida in the control of Culex quinquefasciatus and Aedes aegypti

Picralima nitida is a medicinal plant used for the treatment of various ailments in southern Nigeria. This study aims at evaluating the prospects of using ethanolic extract of leaf and seed of Picralima nitida in the control of larvae of Culex quinquefasciatus and Aedes aegypti, Fourth instar larvae of test organisms were exposed in static bioassays to the crude extracts of P. nitida. Concentrations tested were 0.15-0.75 %w/v, at exposure periods of 24, 48 and 72 hours. At the end of assays (72 hr), the highest concentration (0.75 %w/v) of the ethanol leaf extract of P. nitida resulted in 48.00 and 50.40% mortality of larvae of Cu. quinquefasciatus and Ae. aegypti, respectively. At the same exposure period (72 hr) the ethanol seed extract (0.75 %w/v) resulted in larval mortality of 74.40 and 60.80% for Cu. quinquefasciatus and Ae. aegypti, respectively. The 72 hLC50 values obtained from probit analysis revealed that larvae of Cu. quinquefasciatus were more susceptibe to the seed extract than larvae of Ae. aegypti, with 72hLC50 values of 0.500 and 0.650%w/v, respectively. Phytochemical (qualitative) screening of the leaves and seeds of P. nitida detected the presence of alkaloids, cardiac glycosides, saponins and terpenes. In addition, flavonoids and tannins were detected in the seeds. This preliminary investigation has revealed that the leaves and seeds of P. intida have larvicidal potentials, and could be incorporated into the control measures for mosquito larvae.Keywords: Picralima nitida, extracts, 72 hLC50, Culex quinquefasciatus, Aedes aegypt