BACKGROUND : The rise in antimicrobial resistance in a plethora of nosocomial and opportunistic bacterial pathogens
often isolated from commercial eggs, poses a serious public health concern. The existence of these contaminants
may also serve as a drawback in the current efforts of improving the well-being of immunocompromised patients.
The aim of this study was to determine the efficacy of plant extracts that had good activity on Escherichia coli in
previous word on pathogens isolated from eggs for possible use in combating pathogens from eggs.
METHODS : Acetone leaf extracts of nine trees with good activities against Escherichia coli were tested for their in
vitro antibacterial activity against six opportunistic bacterial isolates from commercial eggs (Stenotrophomonas
maltophilia, Klebsiella pneumoniae, Salmonella serotype Typhimurium, Proteus mirabilis, Enterobacter cloacae and
Escherichia coli) using a serial microdilution method with tetrazolium violet as indicator of growth. Cytotoxicity was
determined using a tetrazolium-based colorimetric assay against Vero kidney cells, and selectivity index calculated.
RESULTS : The MIC values range of the different extracts against Stenotrophomonas maltophilia was 0.08-0.31 mg/ml,
Klebsiella pneumonia 0.08-0.63 mg/ml, Salmonella ser. Typhimurium 0.08-0.63 mg/ml, Proteus mirabilis 0.02-1.25 mg/
ml, Enterobacter cloacae 0.08-0.31 mg/ml and Escherichia coli 0.08-0.16 mg/ml respectively. Escherichia coli was the
most sensitive while Proteus mirabilis was most resistant pathogen to the different test extracts, with mean MIC
values of 0.08 mg/ml and 0.46 mg/ml respectively. Cremaspora triflora extracts had good activity against all the
pathogenic egg isolates, with the exception of Proteus mirabilis. Maesa lanceolata and Elaeodendron croceum had
the best total antibacterial activity (TAA), while generally the selectivity index of the extract was low (SI < 1).
CONCLUSION : The exceptional activity of C. triflora extracts suggests that the plant has potential as a therapeutic
agent against some members of the Enterobacteriaceae. Further pharmacological investigations may be interesting
in the search for new antimicrobial leads.
This manuscript is an output of a Ph. D. research project.