Synergistic interaction between Chlorella vulgaris extract and Origanum elongatum essential oil against methicillin-resistant Staphylococcus aureus.

The massive emergence of antimicrobial resistance in recent decades has rendered the use of a single-agent strategy ineffective. Consequently, the combination of different therapeutic agents has emerged as a promising new approach. The aim of the present study was to investigate the combined effect of Chlorella vulgaris methanol extract (CVME) and Origanum elongatum essential oil (OEEO) on methicillin-resistant Staphylococcus aureus (MRSA). Thus, the antibacterial activity of OEEO and CVME on Escherichia coli, Staphylococcus aureus, and MRSA was evaluated using the agar well diffusion and broth microdilution methods. The killing activity of CVME and OEEO, individually and in combination, on MRSA ATCC 43300 was tested using the time-kill assay. The synergistic effect was examined by determining the fractional inhibitory concentration index (FICI) using the checkerboard test. The results showed very significant antibacterial activity against all the bacteria tested, for both OEEO and CVME, with minimum inhibitory concentrations (MICs) ranging from 0.125 to 0.25% (v/v) for OEEO and from 3.12 to 6.25 mg mL-1 for CVME. Minimum bactericidal concentration (MBC) values for OEEO and CVME were in the range 0.125-0.5% (v/v) and 6.25-12.5 mg mL-1, respectively. The inhibition zones associated with OEEO were distinctly greater than those associated with CVME for all the bacteria examined. When used individually, the time-kill curves of OEEO and CVME revealed a dose-dependent effect on MRSA proliferation. Compared with controls, both agents were able to prolong the latent phase of growth curves and decelerate bacterial growth. The killing effect of OEEO on MRSA was considerably higher than that observed with CVME. OEEO prevented MRSA proliferation at only 1/2 of its MIC, while the CVME did so at 2 times its MIC. The combination of OEEO with CVME demonstrated a synergistic effect against MRSA, with a FIC index value of 0.49. The findings therefore suggest that the combination of C. vulgaris methanol extract and O. elongatum essential oil at very low doses may be promising anti-MRSA candidates. A search of the published literature revealed that, to our knowledge, no studies have yet been carried out on the antibacterial potential of combining essential oils and microalgae extracts in the fight against MRSA.

Mathematical modeling of Escherichia coli O157:H7 growth in carrot juice influenced by Thymbra capitata essential oil, heat treatment, and storage temperature.

The aim of this study was to develop a mathematical model describing the survival of Escherichia coli O157:H7 in carrot juice treated with Thymbra capitata essential oil combined with mild heat treatment and stored at different temperatures. The viable count method was used to investigate the effect of the treatment on bacterial survival, and the response surface methodology was used to develop a statistical model fitting the data. The results showed that the variance of bacterial growth is explained by storage temperature (37 %) and heat treatment (35 %), these are followed by Thymbra capitata essential oil (18 %) and their interaction (9 %). Positive multiplicative interaction was obtained for any pair of the studied treatments and cooperative effect synergy was observed over a large domain of these factors. A mathematical model was successfully developed to describe Escherichia coli O157:H7 response to the selected factors, within the study limits, and to estimate the risk of juice contamination and shelf-life. Based on our results, the use of Thymbra capitata essential oil combined with heat treatment may control Escherichia coli O157:H7 growth in carrot juice stored at low temperature.

Prevalence and antimicrobial profiling of Campylobacter spp. isolated from meats, animal, and human feces in Northern of Morocco.

The present work was carried out to understand the occurrence and antimicrobial susceptibility of Campylobacter spp., in various samples in Northern of Morocco. For this purpose, a random sampling was undertaken from butcher shops, traditional markets, and slaughterhouse. First, the research of Campylobacter was performed according to the Moroccan standard NM ISO: 10272-1 (2008). Second, the isolates were identified by biochemical tests and real time PCR. After the biochemical and molecular identification of suspected colonies, a disk diffusion method was executed to determine the sensitivity of Campylobacter spp. against 18 antibiotics. The results showed a moderate prevalence of Campylobacter species (130/466) recovered mainly on the Campylobacter blood base agar, where C. coli (108/130) were more prevalent comparable to C. jejuni (22/130) in poultry and cattle meat, raw milk, cloacal and surface swabs, and stool of patient suffering from diarrhea. The findings supported also the sensitivity of multiplex qPCR to detect Campylobacter strains compared to Moroccan standard NM ISO: 10272-1 (2008). Among our isolates, C. jejuni were the most susceptible strain toward colistin, florfenicol, gentamicin, streptomycin, and erythromycin. Nonetheless, the presence of multidrug Campylobacter resistant strains was highly observed in C. jejuni isolated, particularly, from broiler chickens toward the antibiotic classes of cephalosporin, penicillin, monobactam, quinolone, fluoroquinolone, sulfamide, as well as tetracycline. This may be due to common use of these drugs in veterinary medicine and farms as growth factor, which limits the usefulness of these molecules. Hence, the study highlights the importance of resistance profile monitoring of these pathogens in Northern of Morocco, in order to develop appropriate control measures and to reduce the emergence of multidrug-resistant strains.

Molecular identification and antibiotic resistance of bacteriocinogenic lactic acid bacteria isolated from table olives.

In the present study, lactic acid bacteria were isolated from table olive in Morocco. Random Amplified Polymorphic DNA fingerprinting with (GTG)'(5) primer revealed a remarquable variability within isolates. According to the molecular identification, Enterococcus faecium was the most dominant species isolated with 32 strains (84.21%), followed by 4 strains of Weissella paramesenteroides (10.52%), 1 strain of Leuconostoc mesenteroides (2.63%) and Lactobacillus plantarum (2.63%). All of the strains that were identified showed occurrence of more than one bacteriocin-encoding gene. Based on the results obtained, L. plantarum 11 showed a mosaic of loci coding for nine bacteriocins (pln A, pln D, pln K, pln G, pln B, pln C, pln N, pln J, ent P). A phenotypic and genotypic antibiotic resistance was also examined. L. plantarum 11, L. mesenteroides 62, W. paramesenteroides 9 and W. paramesenteroides 36 as well as all the strains of E. faecium were susceptible to ampicillin, clindamycin and teicoplanin; however, isolates showed a resistance profile against tetracycline and erythromycin. Except E. faecium 114, E. faecium 130 and L. plantarum 11, no antibiotic resistance genes were detected in all of the strains, which might be due to resistances resulting from non-transferable or non-acquired resistance determinants (intrinsic mechanism).