Use of Antimicrobials from Plants in Feed as a Control Measure for Pathogenic Microorganisms

Animal Feed has become an increasing critical component of the integrated food chain, in 2010 about 1000 mt of animal feed was produced globally and 150 mt in the EU27. The animal feed has an important impact in the human health. The farm or feedlot is the origin of microorganisms introduced onto carcasses during slaughter and dressing. It appears that changes in diet and management practices could precipitate increased shedding of pathogens. Additionally, antibiotics are used in animals, not only for treatment or prevent diseases, but also to promote growth. As a result of the use of antibiotics, food can contain antibiotic-resistant bacteria and resistance genes with important public health consequences. Although antibiotics are banned as growth promoters in the European Union and some other countries, this is not the case throughout the WHO European Region. Travel and the globalization of trade further increase the risk of spreading antibiotic-resistant bacteria.Peer reviewe

Comparative study of the effects of citral on the growth and injury of Listeria innocua and Listeria monocytogenes cells.

This study investigates the effect of citral on growth and on the occurrence of sublethal damage in Listeria innocua Serovar 6a (CECT 910) and Listeria monocytogenes Serovar 4b (CECT 4032) cells that were exposed to citral as a natural antimicrobial agent. Two initial inoculum concentrations were considered in this investigation: 10(2) and 10(6) cfu/mL. Citral exhibited antilisterial activity against L. innocua and L. monocytogenes, and the observed effects were dependent on the concentration of citral present in the culture medium (0, 0.150 and 0.250 μL/mL) (p ≤ 0.05). L. innocua had a shorter lag phase than L. monocytogenes, and the two species had nearly identical maximum specific growth rates. These results indicate that L. innocua could be used as surrogate for L. monocytogenes when testing the effects of this antimicrobial. Significant differences in the lag phase and growth rate were observed between the small and large inoculum concentration (p ≤ 0.05). Citral-treated L. innocua and L. monocytogenes that were recovered on selective medium (i.e., TSA-YE-SC) had a shorter lag phase and a higher maximum specific growth rate than cells that were recovered on non-selective medium (i.e., TSA-YE) (p ≤ 0.05). This result suggests that damage occurs at sublethal concentrations of citral

Mean values ± standard error of the duration of the lag phase (λ) and the maximum specific growth rate (μ_max) of <i>Listeria monocytogenes</i> cells that were recovered on TSA-YE medium as a function of the initial inoculum size (i.e., 10² cfu/mL or 10⁶ cfu/mL) and the concentration of citral (μL/mL).

<p>^A–CMean values followed by different letters in the same column differ significantly by Fisher’s LSD test (p ≤ 0.05).</p><p>^{a, b}Mean values followed by different letters in the same row differ significantly by Fisher’s LSD test (p ≤ 0.05).</p><p>Mean values ± standard error of the duration of the lag phase (λ) and the maximum specific growth rate (μ_max) of <i>Listeria monocytogenes</i> cells that were recovered on TSA-YE medium as a function of the initial inoculum size (i.e., 10² cfu/mL or 10⁶ cfu/mL) and the concentration of citral (μL/mL).</p

Mean values ± standard error of the duration of the lag phase (λ) and the maximum specific growth rate (μ_max) of <i>Listeria innocua</i> as a function of the recovery culture medium (i.e., TSA-YE and TSA-YE-SC) and the concentration of citral using an initial inoculum size of 10² cfu/mL and of 10⁶ cfu/mL.

<p>^A–CMean values followed by different letters in the same column differ significantly by Fisher’s LSD test (p ≤ 0.05).</p><p>^{a, b}Mean values followed by different letters in the same row differ significantly by Fisher’s LSD test (p ≤ 0.05).</p><p>Mean values ± standard error of the duration of the lag phase (λ) and the maximum specific growth rate (μ_max) of <i>Listeria innocua</i> as a function of the recovery culture medium (i.e., TSA-YE and TSA-YE-SC) and the concentration of citral using an initial inoculum size of 10² cfu/mL and of 10⁶ cfu/mL.</p

Mean values ± standard error of the duration of the lag phase (λ) and of the maximum specific growth rate (μ_max) of <i>Listeria innocua</i> cells that were recovered on TSA-YE medium as a function of the initial inoculum size (i.e., 10² cfu/mL or 10⁶ cfu/mL) and the concentration of citral (μL/mL).

<p>^A–CMean values followed by different letters in the same column differ significantly by Fisher’s LSD test (p ≤ 0.05).</p><p>^{a, b}Mean values followed by different letters in the same row differ significantly by Fisher’s LSD test (p ≤ 0.05).</p><p>Mean values ± standard error of the duration of the lag phase (λ) and of the maximum specific growth rate (μ_max) of <i>Listeria innocua</i> cells that were recovered on TSA-YE medium as a function of the initial inoculum size (i.e., 10² cfu/mL or 10⁶ cfu/mL) and the concentration of citral (μL/mL).</p

. <i>L. monocytogenes</i> growth curves in reference medium in the presence of different concentrations of citral (μL/mL) with N₀ = 10² Log(cfu/mL).

<p>The lines represent the fit of the experimental data to the modified Gompertz model. The standard deviation associated with each average value is expressed by error bars.</p

Mean values ± standard error of the duration of the lag phase (λ) and the maximum specific growth rate (μ_max) of <i>Listeria monocytogenes</i> cells as a function of the recovery culture medium (i.e., TSA-YE and TSA-YE-SC) and the concentration of citral using an initial inoculum size of 10² cfu/mL and of 10⁶ cfu/mL.

<p>^A–CMean values followed by different letters in the same column differ significantly by Fisher’s LSD test (p ≤ 0.05).</p><p>^{a, b}Mean values followed by different letters in the same row differ significantly by Fisher’s LSD test (p ≤ 0.05).</p><p>Mean values ± standard error of the duration of the lag phase (λ) and the maximum specific growth rate (μ_max) of <i>Listeria monocytogenes</i> cells as a function of the recovery culture medium (i.e., TSA-YE and TSA-YE-SC) and the concentration of citral using an initial inoculum size of 10² cfu/mL and of 10⁶ cfu/mL.</p