Abstract
Campylobacter jejuni is an important foodborne pathogen causing campylobacteriosis. It can infect humans through the consumption of contaminated chicken products or via the direct handling of animals. Diallyl trisulfide (DATS) is a trisulfide compound from garlic extracts that has a potential antimicrobial effect on foodborne pathogens. This study investigated the antimicrobial activity of DATS on C. jejuni by evaluating the minimal inhibitory concentrations (MICs) of C. jejuni 81-168, and fourteen C. jejuni isolates from chicken carcasses. Thirteen of 14 C. jejuni isolates and 81-176 had MICs ≤ 32 μg/mL, while one isolate had MIC of 64 μg/mL. Scanning electron microscopy (SEM) analysis showed the disruption and shrink of C. jejuni bacterial cell membrane after the DATS treatment. A time-killing analysis further showed that DATS had a dose-dependent in vitro antimicrobial effect on C. jejuni during the 24 h treatment period. In addition, DATS also showed an antimicrobial effect in chicken through the decrease of C. jejuni colony count by 1.5 log CFU/g (cloacal sample) during the seven-day DATS treatment period. The transcriptional analysis of C. jejuni with 16 μg/mL (0.5× MIC) showed 210 differentially expression genes (DEGs), which were mainly related to the metabolism, bacterial membrane transporter system and the secretion system. Fourteen ABC transporter-related genes responsible for bacterial cell homeostasis and oxidative stress were downregulated, indicating that DATS could decrease the bacterial ability to against environmental stress. We further constructed five ABC transporter deletion mutants according to the RNA-seq analysis, and all five mutants proved less tolerant to the DATS treatment compared to the wild type by MIC test. This study elucidated the antimicrobial activity of DATS on C. jejuni and suggested that DATS could be used as a potential antimicrobial compound in the feed and food industry.
Highlights
The antimicrobial activity of diallyl trisulfide (DATS) was evaluated by minimal inhibitory concentrations (MICs) over a serial of concentration on strain 81-176 and 15 strains from chicken samples collected during a previous study [23] (Table 1)
The MIC value of DATS to strain 81-176 was 32 μg/mL, while MICs for chicken isolates were ranged from 1 to 64 μg/mL (Table 1). 0.5% dimethyl sulfoxide (DMSO) was used as a negative control since it did not have an effect on the growth of C. jejuni (Figure 1)
Our results showed that MICs of all C. jejuni mutants for DATS were decreased at a range from 8 to 16 μg/mL, while the MIC of the wild type was 32 μg/mL (Table 3), indicating that transmembrane transporter could be an important factor the elimination of
Summary
Campylobacter is an important foodborne pathogen causing human infections through the consumption of contaminated meat products. Campylobacter spp. has caused 96 million human infection cases, which is the second most important foodborne pathogen for human infections [2]. The infection of Campylobacter is mainly caused by direct contact with animals during meat handling and the consumption of uncooked poultry products [3]. The frequent occurrence of multidrug-resistant Campylobacter pathogenic has increased the difficulties for the infection treatment. Since Campylobacter spp. are commensal bacteria colonizing in the poultry digestive system, the antimicrobial strategies to reduce Campylobacter at the farm level are considered as the priority [3,5]. The investigation of intervention strategies and antimicrobial alternatives that do not further increase bacterial resistance is important for preventing the transmission of Campylobacter in poultry production
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