Woo Kyung Jung

Antibacterial Activity and Mechanism of Action of the Silver Ion in Staphylococcus aureus and Escherichia coli

ABSTRACT The antibacterial effect and mechanism of action of a silver ion solution that was electrically generated were investigated for Staphylococcus aureus and Escherichia coli by analyzing the growth, morphology, and ultrastructure of the bacterial cells following treatment with the silver ion solution. Bacteria were exposed to the silver ion solution for various lengths of time, and the antibacterial effect of the solution was tested using the conventional plate count method and flow cytometric (FC) analysis. Reductions of more than 5 log10 CFU/ml of both S. aureus and E. coli bacteria were confirmed after 90 min of treatment with the silver ion solution. Significant reduction of S. aureus and E. coli cells was also observed by FC analysis; however, the reduction rate determined by FC analysis was less than that determined by the conventional plate count method. These differences may be attributed to the presence of bacteria in an active but nonculturable (ABNC) state after treatment with the silver ion solution. Transmission electron microscopy showed considerable changes in the bacterial cell membranes upon silver ion treatment, which might be the cause or consequence of cell death. In conclusion, the results of the present study suggest that silver ions may cause S. aureus and E. coli bacteria to reach an ABNC state and eventually die.

Prevalence and antibiotic resistance of Campylobacter spp. isolated from chicken meat, pork, and beef in Korea, from 2001 to 2006

A total of 770 samples of retail raw meat were examined for the presence of Campylobacter spp. The samples were obtained randomly from 232 retail stores in Korea from September 2001 to April 2006. The highest contamination rates were observed in chicken meat (220 181.4%] of 270 samples), whereas the rates of contamination in pork and beef were extremely low (1.6 and 1.2%, respectively). The antibiotic-resistant patterns of the 317 Campylobacter isolates were examined by the agar dilution method. Resistance to doxycycline was the most common (97.5%), followed by ciprofloxacin (95.9%), nalidixic acid (94.6%), tetracycline (94.6%), enrofloxacin (84.2%), and erythromycin (13.6%). All Campylobacter isolates from the retail raw meat were resistant to at least one of the six antibiotics tested, and 296 isolates (93.4%) showed multidrug (four or more antibiotics) resistance. This demonstrates that the multidrug-resistant Campylobacter species are widespread in meats in Korea. Therefore, further investigations will be needed to determine appropriate methods for eliminating Campylobacter contamination in industrial chicken production and food chains.

Quantification and differentiation of Campylobacter jejuni and Campylobacter coli in raw chicken meats using a real-time PCR method.

Campylobacter species are one of the most common causes of bacterial diarrhea in humans worldwide. The consumption of foods contaminated with two Campylobacter species, C. jejuni and C. coli, is usually associated with most of the infections in humans. In this study, a rapid, reliable, and sensitive multiplex real-time quantitative PCR was developed for the simultaneous detection, identification, and quantification of C. jejuni and C. coli. In addition, the developed method was applied to the 50 samples of raw chicken meat collected from retail stores in Korea. C. jejuni and C. coli were detected in 88 and 86% of the samples by real-time quantitative PCR and the conventional microbiological method, respectively. The specificity of the primer and probe sets was confirmed with 30 C. jejuni, 20 C. coli, and 35 strains of other microbial species. C. jejuni and C. coli could be detected with high specificity in less than 4 h, with a detection limit of 1 log CFU/ml by the developed real-time PCR. The average counts (log CFU per milliliter) of C. jejuni or C. coli obtained by the conventional methods and by the real-time PCR assay were statistically correlated with a correlation coefficient (R2) between 0.73 and 0.78. The real-time PCR assay developed in this study is useful for screening for the presence and simultaneous differential quantification of C. jejuni and C. coli.

Use of rMPB70 Protein and ESAT-6 Peptide as Antigens for Comparison of the Enzyme-Linked Immunosorbent, Immunochromatographic, and Latex Bead Agglutination Assays for Serodiagnosis of Bovine Tuberculosis

ABSTRACT Current assays used to detect Mycobacterium bovis infection lack accuracy, especially for recently infected animals, or are impractical for rapid field diagnostic applications. To overcome these limitations with serological assays, a synthetic peptide derived from early secretory antigenic target 6 (ESAT6-p) and a recombinant major secreted immunogenic protein (rMPB70) of M. bovis were used in an enzyme-linked immunosorbent assay (EIA), an immunochromatographic assay (ICGA), and a latex bead agglutination assay (LBAA). Sera from noninfected, M. bovis-infected, or M. avium subsp. paratuberculosis-infected (by natural and experimental routes) animals were evaluated. Receiver operating characteristic analysis comparing optical density values from the EIA with results of bacterial culture or skin test, the reference test, established suitable cutoff values for assessing sensitivity and specificity. The EIA and LBAA, respectively, had sensitivities of 98.6 and 94.8%, specificities of 98.5 and 92.6%, and kappa values of 0.97 and 0.88 with ESAT6-p. The EIA, ICGA, and LBAA, respectively, had sensitivities of 96.8, 83.0, and 86.7%, specificities of 90.1, 99.4, and 97.8%, and kappa values of 0.87, 0.85, and 0.83 with rMPB70. Examination of serial samples of sera collected from experimentally M. bovis-infected cattle and deer revealed that ESAT6-p-specific responses developed early after infection whereas responses to rMPB70 developed later in the course of disease. The advantage of the LBAA and ICGA as initial tests for multiple species is a rapid reaction obtained in 2 to 3 h by LBAA or 20 min by ICGA without species-specific secondary antibodies under field conditions, thus allowing immediate segregation of suspect animals for further testing before culling.

Antifungal activity of the silver ion against contaminated fabric

An anti‐fungal efficacy test of the silver laundry machine, which electrically generates silver ions, was carried out against four fungi –Trichophyton rubrum, Candida albicans, Microsporum canis and Aspergillus flavus– which cause major fungal infection in humans and animals. Compared with the conventional laundry machine, washing with the silver laundry machine regardless of detergent use was effective against most of the fungi with about 4 log10 (CFU ml−1) reduction and eliminated almost all the fungi when using the detergent. Moreover, the cleaning activity of the silver laundry machine with detergent was higher than that of the conventional laundry machine with detergent both after wash and after final spin step against all four examined fungi. The silver laundry machine may be useful in preventing skin irritation caused by fungi‐contaminated fabric in the hospital and in the home.

Antimicrobial performance of alkaline ionic fluid (GC-100X) and its ability to remove Escherichia coli O157:H7 from the surface of tomatoes.

An efficacy test of GC-100X, a noncorrosive alkaline ionic fluid (pH 12) composed of free radicals and supplemented with xylitol, was carried out against six major foodborne pathogens-Staphylococcus aureus FRI 913, Salmonella enterica serovar Enteritidis ATCC 13076, S. enterica serovar Typhimurium DT104 Korean isolate, Vibrio parahaemolyticus ATCC 17803, Escherichia coli O157:H7 ATCC 43894, and Pseudomonas aeruginosa KCTC 1637-at three different temperatures (4, 25, and 36 degrees C) with or without organic load (2% yeast extract). Results revealed a more than 4-log10 (CFU/ml) reduction (1.0 x 10(4) CFU/ml reduction) against all pathogens reacted at 37 degrees C for 3 h in the absence of organic material. GC-100X solution diluted with an equal volume of distilled or standard hard water (300 ppm CaCO3) showed effective bactericidal activity, particularly against gram-negative bacteria. Washing efficacy of GC-100X solution was compared against E. coli O157:H7 on cherry tomato surfaces with those of a commercially used detergent and chlorine water (100 ppm). Viable cell counts of E. coli O157:H7 that had penetrated to the cores of tomatoes after sanitizing treatment revealed that GC-100X stock and its 5% diluted solutions had similar washing effects to 100-ppm chlorine water and were more effective than the other kitchen detergent. These results indicate that GC-100X has good bactericidal and sanitizing activities and is useful as a new sanitizer for food safety and kitchen hygiene.

Immunostimulatory Effects of the Anionic Alkali Mineral Complex BARODON on Equine Lymphocytes

ABSTRACT Previous studies have shown that the anionic alkali mineral complex BARODON has an immunoenhancing effect on pigs as an adjuvant and as a nonspecific immunostimulant. Likewise, the equine immune system has been defined with various monoclonal antibodies specific to equine leukocyte differentiation antigens to determine the possibility of enhancing equine resistance to respiratory diseases and promoting other immunostimulatory effects with the application of BARODON. Compared with the control group, after 3 weeks of treatment, BARODON-treated groups showed higher proportions of cells (P < 0.05) expressing major histocompatibility complex class II and CD2, CD4+, CD4+ CD25+, CD8+, and CD8+ CD25+ T lymphocytes, dendritic cells, and surface immunoglobulin M+ B lymphocytes in peripheral blood, as well as enhanced cell proliferative responses with phytohemagglutinin and increased phagocytic activity against Streptococcus equi and Staphylococcus aureus strains with high antibiotic resistance, the bacteria frequently identified as etiologic agents of equine respiratory diseases at the Seoul Race Park in Seoul, Korea. This study shows that BARODON may act as an immunostimulator and can be an effective alternative to antimicrobial feed additives for nonspecific improvements in equine immune responses, particularly against respiratory diseases.