Clostridium difficile is a nosocomial pathogen that causes a serious toxin-mediated enteric disease in humans. Reducing C. difficile toxin production could significantly minimize its pathogenicity and improve disease outcomes in humans. This study investigated the efficacy of two, food-grade, plant-derived compounds, namely trans-cinnamaldehyde (TC) and carvacrol (CR) in reducing C. difficile toxin production and cytotoxicity in vitro. Three hypervirulent C. difficile isolates were grown with or without the sub-inhibitory concentrations of TC or CR, and the culture supernatant and the bacterial pellet were collected for total toxin quantitation, Vero cell cytotoxicity assay and RT-qPCR analysis of toxin-encoding genes. The effect of CR and TC on a codY mutant and wild type C. difficile was also investigated. Carvacrol and TC substantially reduced C. difficile toxin production and cytotoxicity on Vero cells. The plant compounds also significantly down-regulated toxin production genes. Carvacrol and TC did not inhibit toxin production in the codY mutant of C. difficile, suggesting a potential codY-mediated anti-toxigenic mechanism of the plant compounds. The antitoxigenic concentrations of CR and TC did not inhibit the growth of beneficial gut bacteria. Our results suggest that CR and TC could potentially be used to control C. difficile, and warrant future studies in vivo.

Many pathogenic bacteria and fungi produce potentially lethal toxins that cause cytotoxicity or impaired cellular function either at the site of colonization or other locations in the body through receptor-mediated interactions. Various factors, including biotic and abiotic environments, competing microbes, and chemical cues affect toxin expression in these pathogens. Recent work suggests that several natural compounds can modulate toxin production in pathogenic microbes. However, studies explaining the mechanistic basis for their effect are scanty. This review discusses the potential of various plant-derived compounds for reducing toxin production in foodborne and other microbes. In addition, studies highlighting their anti-toxigenic mechanism(s) are discussed.

Salmonella Enteritidis is a common foodborne pathogen transmitted to humans largely by consumption of contaminated eggs. The external surface of eggs becomes contaminated with Salmonella Enteritidis from various sources on farms, the main sources being hens' droppings and contaminated litter. Therefore, effective egg surface disinfection is critical to reduce pathogens on eggs and potentially control egg-borne disease outbreaks. This study investigated the efficacy of GRAS (generally recognized as safe) status, plant-derived antimicrobials (PDA), namely trans-cinnamaldehyde (TC), carvacrol (CR), and eugenol (EUG), as an antimicrobial wash for rapidly killing Salmonella Enteritidis on shell eggs in the presence or absence of chicken droppings. White-shelled eggs inoculated with a 5-strain mixture of nalidixic acid (NA) resistant Salmonella Enteritidis (8.0 log cfu/mL) were washed in sterile deionized water containing each PDA (0.0, 0.25, 0.5, or 0.75%) or chlorine (200 mg/kg) at 32 or 42°C for 30 s, 3 min, or 5 min. Approximately 6.0 log cfu/mL of Salmonella Enteritidis was recovered from inoculated and unwashed eggs. The wash water control and chlorine control decreased Salmonella Enteritidis on eggs by only 2.0 log cfu/mL even after washing for 5 min. The PDA were highly effective in killing Salmonella Enteritidis on eggs compared with controls (P < 0.05). All treatments containing CR and EUG reduced Salmonella Enteritidis to undetectable levels as rapidly as within 30 s of washing, whereas TC (0.75%) completely inactivated Salmonella Enteritidis on eggs washed at 42°C for 30 s (P < 0.05). No Salmonella Enteritidis was detected in any PDA or chlorine wash solution; however, substantial pathogen populations (~4.0 log cfu/mL) survived in the antibacterial-free control wash water (P < 0.05). The CR and EUG were also able to eliminate Salmonella Enteritidis on eggs to undetectable levels in the presence of 3% chicken droppings at 32°C (P < 0.05). This study demonstrates that PDA could effectively be used as a wash treatment to reduce Salmonella Enteritidis on shell eggs. Sensory and quality studies of PDA-washed eggs need to be conducted before recommending their use.

No abstract

c Salmonella enterica serovar Enteritidis is a major foodborne pathogen in the United States, causing gastroenteritis in humans, primarily through consumption of contaminated eggs. Chickens are the reservoir host of S. Enteritidis. In layer hens, S. Enteritidis colonizes the intestine and migrates to various organs, including the oviduct, leading to egg contamination. This study investigated the efficacy of in-feed supplementation with trans-cinnamaldehyde (TC), a generally recognized as safe (GRAS) plant compound obtained from cinnamon, in reducing S. Enteritidis cecal colonization and systemic spread in layers. Additionally, the effect of TC on S. Enteritidis virulence factors critical for macrophage survival and oviduct colonization was investigated in vitro. The consumer acceptability of eggs was also determined by a triangle test. Supplementation of TC in feed for 66 days at 1 or 1.5% (vol/wt) for 40-or 25-week-old layer chickens decreased the amounts of S. Enteritidis on eggshell and in yolk (P < 0.001). Additionally, S. Enteritidis persistence in the cecum, liver, and oviduct in TC-supplemented birds was decreased compared to that in controls (P < 0.001). No significant differences in feed intake, body weight, or egg production in birds or in consumer acceptability of eggs were observed (P > 0.05). In vitro cell culture assays revealed that TC reduced S. Enteritidis adhesion to and invasion of primary chicken oviduct epithelial cells and reduced S. Enteritidis survival in chicken macrophages (P < 0.001). Follow-up gene expression analysis using real-time quantitative PCR (qPCR) showed that TC downregulated the expression of S. Enteritidis virulence genes critical for chicken oviduct colonization (P < 0.001). The results suggest that TC may potentially be used as a feed additive to reduce egg-borne transmission of S. Enteritidis. Salmonella enterica serovar Enteritidis is one of the major foodborne pathogens in the United States responsible for causing enteric illnesses in humans (1). Eggs are the primary source of S. Enteritidis infection of humans (1, 2). Approximately 90 billion eggs are produced and 67.5 billion shell eggs consumed annually in the United States (3). Thus, the microbiological safety of eggs is a major concern to the government, the poultry industry, and consumers due to the potential impacts on public health and the economy. Chickens act as asymptomatic carriers of S. Enteritidis, resulting in its environmental dissemination and potential infection of humans. Humans contract S. Enteritidis infection via consumption of contaminated, raw, or undercooked eggs, and several epidemiological studies have confirmed this association between human salmonellosis and egg consumption (4, 5).Despite the implementation of various pre-and postharvest control measures, S. Enteritidis remains a major cause of eggborne disease outbreaks in the United States (1). Recently, the U.S. Centers for Disease Control and Prevention (CDC) reported that the incidence of foodborne salmonellosis did not decrease signi...

In this study, we investigated the therapeutic efficacy of the plant compounds trans-cinnamaldehyde (TC) and eugenol (EG) on reducing Salmonella enterica serovar Enteritidis (SE) in commercial, market-age broiler chickens. Straight run, day-old commercial broiler chicks (N = 84) were randomly grouped into 6 groups of 14 birds each (n = 14/group): a negative control (no SE, no TC or EG), EG control (no SE, 1% EG), TC control (no SE, 0.75% TC), a positive control (SE, no TC or EG), an EG challenge group (SE, 1% EG), and a TC challenge group (SE, 0.75% TC). Before the start of each experiment, the flock was screened for any inherent Salmonella (n = 12 birds/experiment). Birds were given ad libitum access to Salmonella-free feed and water. On d 30, birds were challenged with a 4-strain mixture of SE (8 log 10 cfu/bird). Two birds from each group were killed after 24 h (d 31) to check for colonization of SE in the cecum. Birds were given feed supplemented with TC (0.75%) or EG (1%) for 5 d before slaughter on d 42 (n = 10 birds/group) for determination of SE populations in the cecum and cloaca. The experiment was repeated 2 times. The trans-cinnamaldehyde and EG consistently reduced SE in the samples in both experiments (P < 0.05). Body weights and feed consumption did not differ among the groups (P > 0.05). On the basis of histological analysis, no abnormal changes in the liver were observed because of supplementation of plant compounds. Therefore, TC and EG supplemented through the feed could reduce SE colonization in market-age chickens.

No abstract

No abstract