Solubilization of membrane-bound quinoprotein D-arabitol dehydrogenase (ARDH) was done successfully with the membrane fraction of Gluconobacter suboxydans IFO 3257. In enzyme solubilization and subsequent enzyme purification steps, special care was taken to purifiy ARDH as active as it was in the native membrane, after many disappointing trials. Selection of the best detergent, keeping ARDH as the holoenzyme by the addition of PQQ and Ca2+, and of a buffer system involving acetate buffer supplemented with Ca2+, were essential to treat the highly hydrophobic and thus labile enzyme. Purification of the enzyme was done by two steps of column chromatography on DEAE-Toyopearl and CM-Toyopearl in the presence of detergent and Ca2+. ARDH was homogenous and showed a single sedimentation peak in analytical ultracentrifugation. ARDH was dissociated into two different subunits upon SDS-PAGE with molecular masses of 82kDa (subunit I) and 14kDa (subunit II), forming a heterodimeric structure. ARDH was proven to be a q...

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 to 10 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.

The limitations in the therapeutic options for foodborne pathogens lead to treatments failure, especially for multidrug-resistant (MDR) Salmonella sp., worldwide. Therefore, we aimed to find alternative and complementary therapies against these resistant foodborne pathogens. Out of 100 meat products samples, the prevalence rate of salmonella was 6%, serotyped only as S. Typhimurium and S. Enteritidis. According to the antibiotic susceptibility assays, the majority of our isolates were MDR and susceptible to cefotaxime. Out of the 13 tested plant extracts, five only showed an inhibition zone in the range of 8–50 mm against both serotypes. Based on their promising activity, the oily extract of cinnamon and aqueous extract of paprika represented the highest potency. Surprisingly, a significant synergistic effect was detected between cinnamon oil and cefotaxime. Depending on Gas Chromatography/Mass Spectrometry (GC-MS), the antimicrobial activity of cinnamon oil was attributed to four components including linalool, camphor, (Z)-3-Phenylacrylaldehyde and its stereoisomer 2-Propenal-3-phenyl. The anti-virulence activities of these compounds were confirmed on the basis of computational molecular docking studies. Accordingly, we recommended the use of cinnamon oil as a food additive to fight the resistant foodborne pathogens. Additionally, we confirmed its therapeutic uses, especially when co-administrated with other antimicrobial agents.