agar and citral

The objective of the present study was to analyze the combined effect of heat treatment (55 to 62.5°C) and citral (0 to 3%) on the heat resistance of Escherichia coli O104:H4 inoculated into ground beef. Inoculated meat packages were immersed in a circulating water bath stabilized at 55, 57.5, 60, or 62.5°C for various times. The surviving microbial cells were counted after culture on tryptic soy agar. A factorial design (4 × 4) was used to analyze the effects and interaction of heat treatment and citral. Heat and citral promoted E. coli O104:H4 thermal inactivation, suggesting a synergistic effect. At 55°C, the incorporation of citral at 1, 2, and 3% decreased D-values (control = 42.75 min) by 85, 89, and 91%, respectively (P < 0.05). A citral concentration-dependent effect (P < 0.05) also was noted at other evaluated temperatures. These findings could be of value to the food industry for designing a safe thermal process for inactivating E. coli O104:H4 in ground beef under similar thermal inactivation conditions.

Topics: Agar; Animals; Cattle; Colony Count, Microbial; Escherichia coli O104; Escherichia coli O157; Food Microbiology; Hot Temperature; Water

The diversity found in the chemical compounds of a single species in different regions results in different biologic characteristics which can be considered as a strong source for identifying new chemotypes. Hymenocrater incanus Bunge and Dracocephalum kotschyi Boiss. are exclusive species of the Lamiaceae family which grow in the western and central habitats of Iran. This study was designed and carried out to determine the yield, identify the chemical compounds, and evaluate the antimicrobial characteristics of the essential oil (EO) of these two species in Iran for the first time.. The flowering twigs of the species D. kotschyi and H. incanus were collected from the villages of Totmach and Kamu in Isfahan province respectively, in May 2019. The EO of these plants was extracted and separated using the water distillation method, utilizing the Clevenger device. The EO compounds were analyzed using a gas chromatograph coupled with a mass spectrometer (GC-MS). The evaluation of antimicrobial characteristics was carried out by determining the growth inhibition zone implementing the Agar method, the minimum inhibition concentration (MIC), and the minimum bactericidal/fungicidal concentration (MFC/MBC) utilizing liquid dilution culture.. The results indicated that the highest yield belonged to the EO of D. kotschyi at %2.6 (w/w). In this EO there were citral (%25.44), neral (%20.87), α-pinene (%14.48), trans-geranic acid methyl ester (%9.74), and D-limonene (%6.87). Moreover, H. incanus had the dominant compounds (-)-Spathulenol (%12.61), caryophyllene (%10.00), linolenic acid (%8.54), 1,8-cineole (%5.95), palmitic acid (%5.35), and α-cadinol (%5.17). The largest diameter of growth inhibition zone belonged to the H. incanus EO against the Gram-positive bacteria S. pyogenes (~17.67mm). The strongest inhibition activities in the form of growth inhibition diameter exhibited by the D. kotschyi EO were against the Gram-negative bacteria S. paratyphi-A serotype (~ 12 mm), K. pneumoniae, and Sh. dysenteriae (~ 11 mm) which was significant compared to the Gram-positive rifampin (~ 8 mm).. It can be seen that these species are new chemotypes with special and novel chemical compounds which can potentially be used to manufacture natural antibiotics against some bacterial strains.

Topics: Acyclic Monoterpenes; Agar; alpha-Linolenic Acid; Anti-Bacterial Agents; Anti-Infective Agents; Biological Products; Ecosystem; Esters; Eucalyptol; Iran; Lamiaceae; Limonene; Microbial Sensitivity Tests; Oils, Volatile; Palmitic Acid; Rifampin; Water

The aim of this study was to evaluate the antibiotic susceptibility of Listeria innocua (L. innocua) and Listeria monocytogenes (L. monocytogenes) cells in the presence of citral and carvacrol at sublethal concentrations in an agar medium. The presence of terpenes in the L. monocytogenes and L. innocua culture medium provided a reduction in the minimal inhibitory concentration (MIC) of all the antibiotics tested. These effects were dependent on the concentration of terpenes present in the culture medium. The combination of citral and carvacrol potentiated antibiotic activity by reducing the MIC values of bacitracin and colistin from 32.0 and 128.0 μg ml⁻¹ to 1.0 and 2.0 μg ml⁻¹, respectively. Thus, both Listeria species became more susceptible to these drugs. In this way, the colistin and bacitracin resistance of L. monocytogenes and L. innocua was reversed in the presence of terpenes. Results obtained in this study show that the phytochemicals citral and carvacrol potentiate antibiotic activity, reducing the MIC values of cultured L. monocytogenes and L. innocua.. Phytochemicals citral and carvacrol potentiate antibiotic activity of erythromycin, bacitracin and colistin by reducing the MIC values of cultured Listeria monocytogenes and Listeria innocua. This effect in reducing the MIC values of the antibiotics tested in both micro-organisms was increased when natural antimicrobials were combined. This finding indicated that the combination among terpenes and antibiotic may contribute in reducing the required dosage of antibiotics due to the possible effect of terpenes on permeation barrier of the micro-organism cell membrane.

Topics: Acyclic Monoterpenes; Agar; Anti-Bacterial Agents; Bacitracin; Colistin; Cymenes; Drug Resistance, Bacterial; Listeria; Listeria monocytogenes; Microbial Sensitivity Tests; Monoterpenes

Topics: Acyclic Monoterpenes; Agar; Antifungal Agents; Aspergillus niger; Culture Media; Menthol; Monoterpenes; Rhizopus; Terpenes