• Journal of Food Hygiene and Safety
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• v.39 no.3
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• pp.181-190
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• 2024

Bovine mastitis-associated Escherichia coli (BMEC) is considered the main causative agent of significant financial losses in the dairy industry worldwide, as it alters both the quantity and quality of milk produced and increases the rate of culling. This creates a variety of challenges for researchers, veterinarians, and farmers in understanding and determining the most effective therapies and diagnostic techniques. Subclinical mastitis is particularly concerning, as infected bovines exhibit no obvious symptoms and continue to secrete apparently normal milk over an extended period, allowing the causative pathogen, E. coli, to spread within the herd. For effective prevention, understanding the pathogenesis of mastitis through three stages invasion, infection, and inflammation is essential. To date, no clear correlation has been found between virulence factors and pathogenicity contributing to the clinical severity of BMEC. Multidrug-resistant E. coli and the evolution of novel resistance mechanisms have become concerns owing to the extensive use of antibiotics to treat mastitis. Therefore, it is vital to explore alternative controls to enhance the efficacy of BMEC treatment. Over the past 30 years, various genetic typing techniques have been used to examine the subspecies-level epidemiology of bovine mastitis. These studies have advanced our understanding of the origin, transmission pathway, population structure, and evolutionary relatedness of BMEC strains. In this review we provide an overview of BMEC, including insights into its etiology, genetic relationship, pathogenesis, and management of the disease, as well as new therapy options.

• Clinical and Experimental Pediatrics
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• v.49 no.8
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• pp.882-888
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• 2006

Purpose : Bacteremia is one of the major concerns in the treatment of pediatric cancer patients. This study was to determine the etiologic agents and the pattern of antibiotic susceptibilities in a single tertiary medical center. Methods : We retrospectively reviewed the medical records of the cases of bacteremia in pediatric cancer patients from 1998 to 2005 in Keimyung University Dongsan Medical Center. Results : There were 62 cases of bacteremia from 44 patients. Gram-positive organisms(48.3%) were more common than gram-negative organisms(38.7%) or fungi(13%). Among gram-positive organisms, Staphylococcus epidermidis was the most common etiologic agent(63.3%), followed by Staphylococcus aureus(16.7%), ${\alpha}$-hemolytic Streptococcus(16.7%), and Streptococcus mitis(3.3%). Among gram-negative organisms, Alcaligenes xylosoxidans was the most common agent(41.7%) and the other organisms were Klebsiella pneumoniae(20.8%), Stenotrophomonas maltophilia(12.5%), Acinetobacter baumanii(8.2%), etc. In febrile neutropenic patients, however, K. pneumoniae was the most common cause of gram-negative bacteremia. All of the isolated K. pneumoniae in our center produced extended-spectrum beta-lactamase and were related with high mortality. S. aureus, S. epidermidis, and Streptococcus species were all susceptible to vancomycin and teicoplanin. Most staphylococci were resistant to penicillin and oxacillin. Most of the gram-negative organisms were susceptible to imipenem. Conclusion : Gram-positive organisms were more commonly isolated than gram-negative organisms in pediatric cancer patients like other studies. We could obtained valuable information on the choice of proper antibiotics in our institution. Further studies will be needed to explain the prevalence of A. xylosoxidans in our center.

• Pediatric Infection and Vaccine
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• v.25 no.2
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• pp.82-90
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• 2018

Purpose: Survival after liver transplantation (LT) has improved over the years, but infection is still a major complication. We aimed to identify the characteristics of bacterial infections in pediatric LT recipients. Methods: This study is a retrospective review of 189 consecutive children undergoing LT between 2000 and 2015 at a single center. In this study, the incidence of infection was determined for the following periods: within 1 month, between 1-5 months, and between 6-12 months. Patients who underwent liver transplants more than once or multiple organ transplants were excluded. Results: All patients had received postoperative antibiotic for 3 days. Only the maintenance immunosuppression with oral tacrolimus and steroids were performed. As a result, 132 bacterial infections developed in 87 (46.0%) patients (0.70 events per person-year). Bacterial infections occurred most frequently within the first month (n=84, 63.6%) after LT. In the pathogens, Staphylococcus aureus (15.2%), Enterococcus species (15.2%), and Klebsiella species (13.6%) were most common. Regarding the organ infected, bloodstream was most common (n=39, 29.5%), followed by peritoneum (n=28, 21.2%), urinary tract (n=25, 18.9%), and lungs (n=20, 15.2%). We changed prophylactic antibiotics from ampicillin-sulbactam to piperacillin-tazobactam at 2011, October, there were no significant effects in the prevalence of antibiotics resistant bacterial infections. The 1-year mortality was 9.0% (n=17), in which 41.2% (n=7) was attributable to bacterial infection; septicemia (n=4), pneumonia (n=2), and peritonitis (n=1). Conclusions: The incidence and type of bacterial infectious complications after LT in pediatric patients were similar to those of previous studies. Bacterial complications affecting mortality occur within 6 months after transplantation, so proper prophylaxis and treatment in this period may improve the prognosis of LT.

• Childhood Kidney Diseases
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• v.16 no.2
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• pp.80-88
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• 2012

Purpose: The aim of our study was to investigate the characteristics of the peritoneal dialysis (PD) - related peritonitis and to evaluate the effectiveness of the empirical antibiotics recommended by the International Society for Peritoneal Dialysis in Korean children. Methods: We retrospectively reviewed the medical records of 72 children on peritoneal dialysis at the Department of Pediatrics, Asan Medical Center over the period from March 2000 to February 2012. Results: Seventy-nine episodes of peritonitis occurred in 32 patients. The incidence of peritonitis was 0.43 episodes/patient year. There were no significant differences in the incidence of peritonitis in terms of dialysis modality (P=0.459). Twenty-one patients experienced 51 catheter exit-site infections (0.28 episode/patient year). There were no significant differences in the incidence of peritonitis between those with and without history of exit-site infections (P=0.721). Specific pathogens were isolated from 68.4% (54/79) of the patient with peritonitis episodes, including Gram-positive bacteria (n=34), Gram-negative bacteria (n=25) and fungus (n=1). Among Gram-positive bacteria, 85.3% of the isolates were susceptible to ${\beta}$-lactam antibiotics, among Gram-negative rods, 94.7% of the isolates were susceptible to ceftazidime. Among 25 cases with unknown etiologies, 92.0% of cases demonstrated satisfactory responses to cefazolin and ceftazidime. Conclusions: The incidence of peritonitis was 0.43 episodes/patient year. Initial empirical therapy consisting of cefazolin and ceftazidime was appropriate for 91.1% of the PD-related peritonitis treatment. Continuous monitoring for the emergence of the resistant organisms is an important part of the appropriate managements of PD-related peritonitis.

• Proceedings of the Korea Society of Poultry Science Conference
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• 2003.07b
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• pp.37-54
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• 2003

It has been recognized that the hen. like its mammalian counterparts. provides young chicks with antibodies as protection against hostile invaders. This system facilitates the transfer of specific antibodies from serum to egg yolk. and provides a supply of antibodies called immunoglobulin Y(IgY) to the developing embryo and the hatched chick. The protection against pathogens that the relatively immuno-incompetent newly hatched chick has. is through transmission of antibodies from the mother via the egg. Egg yolk. therefore. can be loaded with a large amount of IgY against pathogens which can immobilize the existing or invading pathogens during the embryo development or in day-old chicks. Thus. the immunization of laying hens to various pathogens results in production of different antigen-specific IgY in eggs. Egg yolk contains 8~20 mg of immunoglobulins (IgY) per $m\ell$ or 136~340 mg per yolk suggesting that more than 30 g of IgY can be obtained from one immunized hen in a year. By immunizing laying hens with antigens and collecting IgY from egg yolk. low cost antibodies at less than ＄10 per g compared to more than ＄20.000 per g of mammalian IgG can be obtained. This IgY technology opens new potential market applications in medicine. public health veterinary medicine and food safety. A broader use of IgY technology could be applied as biological or diagnostic tool. nut-raceutical or functional food development. oral-supplementation for prophylaxis. and as pathogen-specific antimicrobial agents for infectious disease control. This paper has emphasized that when IgY-loaded chicken eggs are produced and consumed. the specific antibody binds. immobilizes and consequently reduces or inhibits the growth or colony forming abilities of microbial pathogens. This concept could serve as an alternative agent to replace the use of antibiotics. since today. more and more antibiotics are less effective in the treatment of infections. due to the emergence of drug-resistant bacteria.

• Journal of the Korean Society of Food Science and Nutrition
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• v.30 no.5
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• pp.796-801
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• 2001

A total of 277 mineral spring water samples in Kangwon province from 1999 to 2000 were analyzed for the presence of Yersinia spp. by the conventional Food and Drug Administration protocol, and presumptive strains were identified by morphological, cultural and biochemical tests according to Bergey’s manual. Also, the biotypes, serotypes, and susceptibility to 12 antibiotics were tested. Among the total 277 mineral spring water samples, 40 samples (14.4%) were found to be contaminated with Yersinia species. Among the 40 strains of Yersinia spp. isolates, 33 strains (82.5%) for Yersinia enterocolitica, 4 strains (10%) for Yersinia frederiksenii, 2 strains (5%) for Yersinia intermedia, and 1 strain (2.5%) for Yersinia sakazaki were identified, respectively. Of 40 Yersinia spp. isolates, Yersinia enterocolitica (82.5%) was the most predominant species in the mineral spring water samples compared to other Yersinia species. Compared to direct culture method after KOH treatment and KOH treatment method after cold enrichment for better isolation ratio of according to comparision of Yersinia species, the detection ration (18.5%) of KOH treatment method after cold enrichment was about 3 times better than that (6.1%) of direct culture method after KOH treatment. According to serotypes of Y. enterocolitica isolates, O : 5 (12.9%) was the most predominant and followed by O : 3 (9.7%), O : 8 (6.5%), and O : 9 (3.2%), and others. For biotypes of Y. enterocolitica isolates, 1A (71.0%) was the most predominantly abundant and followed by 3A (12.9%), 3B (9.7%), 1B (3.2%) and 5 (3.2%). Also, an antibiotic susceptibility test showed that Yersinia spp. isolates were very susceptible to the antibiotics tested, but they were very strongly resistant to ampicillin, cephalothin and carbenicillin.

• Tuberculosis and Respiratory Diseases
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• v.64 no.1
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• pp.8-14
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• 2008

Background: Acinetobacter infections are difficult to treat as they often exhibit multiple resistance to the antibiotics that are currently available for the treatment of pneumonia. Colistin is active against gram-negative bacteria, including the multiple drug resistant (MDR) Acinetobacter species. However, intravenous administration of colistin was abandoned because of its nephrotoxicity and neurotoxicity. The aims of this study were to examine the efficacy and safety of colistin administered by aerosol in the treatment of pneumonia caused by MDR Acinetobacter baumannii. Methods: We retrospectively reviewed the medical records of patients admitted to the intensive care unit (ICU) from Dec. 2006 to Aug. 2007 who had been diagnosed as suffering from pneumonia due to MDR Acinetobacter baumannii and had been treated with nebulized colistin. Results: 31 patients received aerosolized colistin. The average duration of the treatment was $14{\pm}7$ days and the daily dose of ranged from 225 mg to 300 mg. All patients received concomitant intravenous antimicrobial agents. The average length of the stay in the ICU was $34{\pm}21$ days and in the hospital $58{\pm}52$ days. The overall microbiological eradication was observed in 25 patients (80.6%). 14 of these (56%) were cured, and 11 (44%) were infected with other microorganisms. The overall crude mortality of the ICU was 48%. Nephrotoxicity and significant bronchial constriction did not occur in any patient during neublized colistin treatment. Conclusion: Nebulized colistin may be a safe and effective option in the treatment of pneumonia due to MDR Acinetobacter baumannii. Its role in therapy warrants further investigation in comparative studies.

• Journal of the korean academy of Pediatric Dentistry
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• v.36 no.2
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• pp.237-244
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• 2009

When the symptom of periapical infection is not released by mechanical instrumentation. anti-microbial agents including antibiosis become necessary in order to remove microorganisms from the root canal. Since anti-microbial agents of natural origins are currently popular, more natural remedies are being sought out. As it turns out, it is well known isothiocyanates (ITCs) in horseradish root extract have anti-microbial activity from many studies. In this research, anti-microbial effects of horseradish root extract and chlorhexidine, a typical anti-microbial agent, were investigated and compared against two kinds of obligate anaerobes. Fusobacterium nucleatum and Prevotella nigrescens, that are often discovered in infected root canal, and Clostridium perfringens, which is resistant to antibiotics and frequently used as a control strain for antibacterial studies 1. The MIC and MBC of horseradish root extract were ranged from 87 to 470 ppm and from 156 to 625 ppm against three kinds of obligate anaerobes, respectively. Horseradish root extract showed the strongest anti-bacterial activity (MBC, 156 ppm) against F. nucleatum and also showed anti-bacterial activity against antibiotic resistant obligate anaerobes. C. perfringens. 2. The MIC and MBC of chlorhexidine were ranged from 3.12 to 6.25 ppm and 10.94 ppm against three kinds of obligate anaerobes, respectively. 3. The MIC with 87-470 ppm of horseradish root exact has the same growth inhibiting effect as the one of 3.12-6.25 ppm of chlorhexidine. Likewise, the MBC with 156-625 ppm of horseradish has the similar bactericidal effect as 10.94 ppm of chlorhexidine.

• The Journal of the Korean Society for Microbiology
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• v.9 no.1
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• pp.7-11
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• 1974

The authors identified fifty-eight Shigella cultures among 1644 cultures and specimens of enteric pathogens collected from all over the country in 1973. Fifty-one out of fifty-eight cultures belonged to Shigella flexneri and the rest to Shigella sonnei. None of cultures belonging to either subgroup A or C was detected in 1973. Of fifty-one cultures of Shigella flexneri twenty-six cultures were $B_{2a}$, which were isolated in Seoul area and Kwangwon-Do. The rest were $B_{3a}$ which were isolated in Jeonla-bug-Do and Kangwon-Do. It would not be possible to understand that there might not have been the cases or carriers of Shigella in the areas where the organisms were not isolated in 1973 and that there might not have been any other serotypes existing in the country, although there was a quite disparity found in the distribution between different areas and in the detection of the serotypes as shown in Table 1. Concerning the biochemical properties there were only two cultures showing positive arginine decarboxylase test among $B_{2a}$, and there were three cultures of trehalose negative cultures, one of rhamnose positive culture and one of glycerol positive culture observed, which were considered to be unusual. All the Shigella cultures were sensitive to nitrofurantoin, cephalosporin and ampicillin, and resistant to colistin, bacitracin and neomycin. Majority of them showed sensitive results to gentamycin, and the majority of Shigella $B_{3a}$ appeared to be sensitive to chloramphenicol, tetracycline, oxytetracycline and doxycycline, but the majority of $B_{2a}$ and Shigella sonnei were observed resistant to those antibiotics by means of the In-Vitro tests.

• Microbiology and Biotechnology Letters
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• v.34 no.4
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• pp.342-351
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• 2006

The aim of this study was to survey susceptibilities of Escherichia coli and Klebsiella pneumoniae isolates against cefotaxime and to determine the prevalences of CTX-M type extended-spectrum $\beta$-lactamases (ESBLs) producing E. coli and K. pneumoniae in Korea. During the period of February to July, 2005, 153 E. coli and 52 K. neumoniae isolates were collected from 2 hospitals in Busan. Antimicrobial susceptibilities to cefotaxime were tested by the disk diffusion method. ESBL production of E. coli and K. pneumoniae was determined by the double disk synergy test. MICs of $\beta$-lactam antibiotics were determined by the agar dilution method. Blac$_{CTX-M}$ genes of the organism were detected by PCR. Among 153 isolates of E. coli and 52 isolates of K. neumoniae, 27 (17.6%) and 25 (48.0%) were intermediate or resistant to cefotaxime, respectively. Twenty-three (15.0%) isolates out of 153 E. coli and 13 (25.0%) out of 52 K. neumoniae isolates showed positive results for ESBL by the double disk synergy test. Twenty isolates out of 23 ESBL producing E. coli and 12 out of 13 ESBL producing K. neumoniae isolates harbored biacTx-M gene,11 of ESBL producing E. coli and 12 of ESBL producing K. neuinoniae isolates harbored bla$_{CTX-M}$ gene, 11 of the ESBL producing E. coli and 2 of ESBL producing K. neumoniae isolates harbored bla$_{TEM}$ gene, and 1 of the ESBL producing E. coli and 12 of ESBL producing K. neumoniae isolates harbored bla$_{SHV}$ gene. E. coli and K. neumoniae isolates producing CTX-M-type ESBLs were not uncommon in Korea. It is thought that continuous survey are necessary for inspecting the spread and novel variants of CTX-M-type ESBL genes. Further me]'e investigation and research on ESBL producing strains are needed in order to prevent the spread of resistant bacteria.