Garlic (Allium sativum L.) has long history of reputed value and actual use for its medicinal, antimicrobial and pesticidal properties. This study was conducted to find possible developments to natural food preservatives and natural antimicrobials from garlic extracts. The antimicrobial activities of raw garlic extract, heat, pH, temperature against pathogenic bacteria were investigated. E. coli, S. Enteritidis, L. monocytogenes, and S. aureus exhibited antimicrobial activities at 20% garlic extract, but no antimicrobial activity was seen in E. faecium. Raw garlic extract and garlic extract heated for 2 min at 95 o C showed strong antimicrobial activities, but the antimicrobial activity of garlic extract heated for 10 min at 95 o C was much less. The antimicrobial activities of 50% garlic extract adjusted pH 4.0∼7.0 showed much the same, but the antimicrobial activities decreased at pH 8.0 or higher. The antimicrobial activities by storage −18 o C of garlic extract showed much the same. When five strains were cultured for 72 hr at 35 o C in the TSB containing 1∼10% garlic extract, viable cell number of five strains were decreased to 10 0 ∼104 CFU/ml even at 1% or 2.5% (E. faecium) after 24 hr, but later increased to 10 4 ∼10 9 CFU/ml after 72 hr. When five strains were cultured for 21 day at 4 o C in the TSB containing 1%, 2.5%, 5%, and 10% garlic extract, viable cell number of E. coli, S. Enteritidis, and S. aureus were decreased to 10 3, 10 0 ∼10 2, 10 1 ∼10 4 CFU/ml after 21 day, respectively, but L. monocytogenes and E. faecium increased to 10 8 and 10 6 CFU/ml after 21 day.
To detect the virulence genes (invA and spvC) and antimicrobial resistance genes, polymerase chain reaction (PCR) was carried out using total 67 strains of S. Schwarzengrund isolated from pigs. As results, invA was detected from all 67 strains of S. Schwarzengrund, however, spvC was not at all. All 12 strains with ampicillin resistance, 15 strains with chloramphenicol resistance, 9 strains with kanamycin resistance, 1 strain with sulfamethoxazole/trimethoprim resistance, and 66 (98.5%) of 67 strains with tetracycline resistance carried TEM (β-lactamase bla TEM ), cmlA (nonenzymatic chloramphenicol resistance), aphA1-Iab (aminoglycoside phosphotransferase), sulII (dihydropteroate synthase), and tetA (class A tetracycline resistance), respectively. All 63 strains with streptomycin resistance carried 3 aminoglycoside resistance genes, including aadA (aminoglycoside adenyltransferase), strA, and strB (streptomycin phosphotransferase). With respect to prevalence of antibiotic resistance genes occurred in S. Schwarzengrund, genes for strB (46.0%); strA and strB (30.2%); aadA, strA, and strB (9.5%); strA (7.9%); aadA and strB (3.2%); and aadA (3.2%) were detected by PCR.
Total 99 strains of Campylobacter spp. were isolated from 117 cases of duck's fecal samples. Among 99 strains of Campylobacter spp. isolates, 93 strains (93.9%) were C. jejuni and 6 strains (6.1%) were C. coli. Prevalence of virulence and GBS associated genes of 72 C. jejuni isolates was determined by m-PCR. Among the 10 kinds of virulence associated genes, cadF, dnaJ, flaA and ceuE genes were detected in all of C. jejuni isolates from ducks, racR, pldA, iamA, ciaB, virB11 and docC genes were 87.5%, 84.7%, 77.8%, 48.6%, 13.9% and 11.1%, respectively. Antimicrobial susceptibility test was performed on 72 C. jejuni isolates. The rate of resistance were 62.5% for oxytetracycline, 55.6% for kanamycin, 54.2% for enrofloxacin, 50% for ciprofloxacin, 37.5% for tetracycline and nalidixic acid, 18.1% for ampicillin, 15.3% for streptomycin, and 6.9% for ofloxacin. All isolates were susceptible to erythromycin. The adherence (intracellular and extracellular bacteria) abilities of the 20 isolates to INT-407 cells were between 4.21±1.27×10 4 CFU/well and 1.053±0.451×10 6 CFU/well from the isolates of cj-55 and cj-52, respectively, and that can be expressed as 0.1033% to 5.2655% to the infecting inoculum. The invasion (intracellular bacteria) abilities of the 20 isolates to INT-407 were between 1.00±1.73×10 3 CFU/well and 8.47±5.16×10 4 CFU/well from the isolates of cj-13 and cj-47, respectively, and that can be expressed as 0.0050% to 0.4235% to the infecting inoculums. The average CFU/well of 20 campylobacters isolated from ducks for adherence to and invasion were 2.646±2.886×10 5 and 3.03±2.7×10 4 respectively, and that was 1.3230±1.2139% and 0.1516±0.1343% of the starting viable inoculum. There was considerable correlation (R 2 =0.627) between the adherence and invasion ability of C. jejuni isolates for INT-407 cell.
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