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Molecules 2020, 25, 4583 2 of 22
Molecules 2020, 25, 4583 2 of 22
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| Abstract: |
Bacterial outbreaks caused by Staphylococcus aureus (S. aureus) are interesting due to the
existence of multidrug resistant (MDR) isolates. Therefore, there is a need to develop novel ways to
control such MDR S. aureus. In this study, some natural agents such as honey bee (HB), extracts of
either Moringa oleifera seeds (MSE), or leaves (MLE) and essential oils of garlic, clove, and moringa
were studied for their inhibitory activity against this S. aureus pathogen. About 100 food samples
including beef luncheon (n = 25), potato chips (n = 50), and corn flakes (n = 25) were investigated for
possible pollution with the S. aureus bacteria. The isolated bacteria suspected to belong S. aureus that
grew well onto Baird–Parker agar (Oxoid) and shiny halo zones and positive coagulase reaction
were selected and identified by API-Kits; all of them that were approved belong to S. aureus (18
strains). The sensitivity of the obtained 18 S. aureus bacterial strains to 12 antibiotics were evaluated;
all of them were resistant to ofloxacin; however, other antibiotics tested showed variable results.
Interestingly, the S. aureus No. B3 isolated from beef luncheon was resistant to10 antibiotics out of
12 ones tested. Multiple antibiotic resistance index (MAR) of this S. aureus strain was about 83.3%.
Therefore, its identification was confirmed by sequencing of a 16S rRNA gene which approved a
successful biochemical identification carried out by API Kits and such strain was designated S.
aureus LC 554891. The genome of such strain appeared to contain mecA gene encoding methicillin
resistance; it was found to contain hla, hlb, tsst-1, and finbA that encode α-blood hemolysis, β-blood
hemolysis, toxic shock syndrome gene, and fibrinogen-binding protein gene, respectively. In
addition, the virulence factors viz. sea; seb; sec encoding enterotoxins were detected in the DNA
extracted from S. aureus B3 strain. Aqueous extract of Moringa oleifera seeds (MSE) showed inhibitory
activity against S. aureus LC 554891 better than that obtained by tetracycline, essential oils or HB.
Minimum inhibitory concentration (MIC) of MSE was 20μg/mL. Instrumental analysis of MSE
showed 14 bioactive chemical compounds. Combinations of both MSE and tetracycline showed
distinctive inhibitory activity against S. aureus LC 554891 than that obtained by either tetracycline
or MSE singly.
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