A total of 244 lactic acid bacteria (LAB) strains were isolated from 180 dairy and pharmaceutical products that were collected from different areas in Minia governorate, Egypt. LAB were identified phenotypically on basis of morphological, physiological and biochemical characteristics. Lactobacillus isolates were further confirmed using PCR-based assay. By combination of phenotypic with molecular identification Lactobacillus spp. were found to be the dominant genus (138, 76.7%) followed by Streptococcus spp. (65, 36.1%) and Lactococcus spp. (27, 15%). Some contaminant organisms such as (Staphylococcus spp., Escherichia coli, Salmonella spp., mould and yeast) were isolated from the collected dairy samples but pharmaceutical products were free of such contaminants. Susceptibility of LAB isolates to antibiotics representing all major classes was tested by agar dilution method. Generally, LAB were highly susceptible to Beta-lactams except penicillin. Lactobacilli were resistant to vancomycin, however lactococci and streptococci proved to be very susceptible. Most strains were susceptible to tetracycline and showed a wide range of streptomycin MICs. The MICs of erythromycin and clindamycin for most of the LAB were within the normal range of susceptibility. Sixteen Lactobacillus,8 Lactococcus and 8 Streptococcus isolates including all tetracycline and/or erythromycin resistant strains were tested for the presence of tetracycline and/or erythromycin resistant genes [tet(M) and/or erm(B)]. PCR assays shows that some resistant strains harbor tet(M) and/or erm(B) resistance genes.

Antimicrobial resistance is one of the greatest threats to human health. Alternatives to antimicrobials are needed to combat the rise of bacterial resistance. Essential oils (EOs) and their components are potential sources of new antimicrobials. The present study was conducted to evaluate the antibacterial and antifungal activities of two components of EOs. The antimicrobial mechanisms of eugenol and linalool were investigated against five bacterial strains and four Candida strains. Broth macrodilution method was used to compare the antibacterial and anticandidal activities of the two compounds. They exhibited antimicrobial activity against all tested strains. Germ tube formation by Candida albicans was investigated and it was found that it was completely inhibited at sub-MICs of eugenol while linalool showed minor activity compared to eugenol. Time kill kinetic studies indicated that eugenol was highly toxic to all bacterial and fungal strains within 2.5 h of exposure. Absorbance of intracellular constituents was measured at 260 nm. Only eugenol was highly effective toward lysis and cellular content leakage compared to control drugs. In addition, scanning electron microscopy (SEM) was used to charactize the effect of the two components on cell morphology and showed that both compounds induced cellular deformity of nearly all tested cells. Also, it was found that only eugenol inhibited the Beta-lactamase production and urease activity and it diminished bacterial motility of all tested bacterial strains. These results indicate that eugenol and linalool are effective antimicrobial agents and both antibacterial and antifungal activities of linalool were much weaker than that of eugenol. Key words: Antimicrobial resistance, antimicrobials, germ tube formation, time kill kinetic, cellular deformity.