• Korean Journal of Microbiology
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• v.49 no.2
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• pp.118-125
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• 2013

Antibiotic susceptibility was examined for 596 Salmonella isolates from patients with acute gastroenteritis during 2000-2009 in Gwangju area in South Korea. Of 16 antibiotics tested, ampicillin resistance (43%) was the most commonly observed resistance among the 596 Salmonella sp. isolates, followed by tetracycline (35.9%), nalidixic acid (31.5%), and chloramphenicol (26.2%). Antibiotic resistance varied among serotypes: The highest resistance of S. Enteritidis and S. Typhimurium was to ampicillin (51.1%) and tetracycline (77.9%), respectively. A total of 89 resistance patterns were observed, and 26% (155/596) of Salmonella isolates were susceptible to all antibiotics tested in this study. About 21% (127/596) and 15% (87/596) of the isolates were resistant to one and two antibiotics, respectively. The rest of Salmonella isolates (227/596, 38%) were resistant to three or more antibiotic agents. The highest multi-drug resistance (MDR) was observed in serotype S. Paratyphi B (76.5%), followed by S. Typhimurium (58.2%), and S. Enteritidis (40.2%). The most common resistance pattern of MDR isolates was ampicillin-chloramphenicol-nalidixic acid-ticarcillin (36/227, 15.8%), most of which (35/36, 97.2%) were S. Enteritidis.

• Korean Journal of Microbiology
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• v.45 no.2
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• pp.99-104
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• 2009

This study describes the antimicrobial susceptibility and multidrug resistance patterns in 115 isolates of Salmonella enterica serovar Enteritidis from diarrhea patients in Incheon from Jan. 2004 to Dec. 2008. Overall, the highest rate of resistance was found to the following antimicrobial agents: nalidixic acid 54.8%, ampicillin 40.0%, ticarcillin 38.3%, chloramphenicol 20.9%, and tetracycline 17.4%. 91% (104 isolates) were resistant to one or more antimicrobial agents tested. Among the described antimicrobial resistant patterns, the predominant patterns were only nalidixic acid (44.3%), ampicillin-chloramphenicol-ticarcillin (11.3%,) and ampicillin-ticarcillin (10.4%). Overall, the resistant rate to one drug was 51.9%, two drugs 18.2%, three drugs 14.5%, four drugs 5.8%, and five or more drugs 9.7%.

• Korean Journal of Microbiology
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• v.46 no.4
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• pp.326-333
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• 2010

A total of 105 nontyphoid Salmonella isolated from infants in Seoul from 2003 to 2009 was investigated for their serotype, antimicrobial resistance, characterization of integron, and the patterns of Pulsed-field gel electrophoresis (PFGE). Eighteen serotypes were detected in 105 isolates, and the two most common serotypes were S. Enteritidis (47.6%) and Montevideo (15.2%). Among the Salmonella serovars, a high level of antimicrobial resistance was found to ampicilin (60%), tetracycline (46.7%), streptomycin (35.2%) and nalidixic acid (28.6%). In the multi-drug resistance patterns, the predominant patterns were only nalidixic acid (15.7%), ampicillin-ampicillin/sulbactam-tetracycline (14.5%), and ampicillin-streptomycin-chloramphenicol-tetracycline (10.8%). PCR and DNA sequencing analysis revealed the presence of class 1 integron in 20 isolates (19%). Of the class 1 integron positive isolates 20% harboured the integron-associated gene cassettes : aadA2, blaP1, dfr17-aadA5, dfrA12-aadA2, and aadA7. PFGE was carried out to examine the genetic relatedness among S. Enteritidis isolates. Except for three strains, fifty strains were divided by three pulsotypes.

• Korean Journal of Microbiology
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• v.50 no.3
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• pp.185-190
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• 2014

The aim of this study was to investigate the prevalence of quinolone resistant E. coli from raw bulk milk and to characterize the resistance determinants. In this study, the gyrA, gyrB, parC, and parE quinolone resistance determining regions (QRDR) were sequenced from quinolone resistant E. coli isolates. Also, the presence of plasmid-mediated quinolone resistance (PMQR) and the expression of efflux pump genes based on quantitative real-time PCR (qRT-PCR) were investigated. Of the 487 coliform bacteria, 9 strains showed nalidixic acid resistance, and 6 of the 9 nalidixic acid resistant isolates were also ciprofloxacin resistant. These 9 strains had a single mutation at codon 83 (S83L) in gyrA, 2 of them had double mutations at codon 83 and 87 (S83L and D87N) in gyrA and 3 of the 9 isolates had single mutations at codon 80 (S80I) in parC. None of the 9 isolates harbored PMQR determinants. Compared with wild-type E. coli ATCC 25922, an over-expression of the acrB gene (2.15-5.74 fold), encoding the pump component of the AcrAB-TolC efflux pump was observed in 4 of 6 ciprofloxacin resistant isolates. This study identified the quinolone resistance mechanism of E. coli isolated from raw milk samples in Gyeonggi-do.

• Food Science and Biotechnology
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• v.17 no.1
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• pp.191-194
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• 2008

The antagonistic activity of probiotic strains (Bifidobacterium animalis BB-12, Bifidobacterium bifidum A, Bifidobacterium longum B6, Lactobacillus acidophilus ADH, Lactobacillus paracasei ATCC 25598, and Lactobacillus rhamnosus GG) against nalidixic acid resistant ($NA^R$) Escherichia coli O157:H7 MF1847, E. coli O157:H7 H2439, E. coli O157:H7 ATCC 43894, and E. coli O157:H7 C7927 was investigated using the agar-overlay, well diffusion, and broth culture tests. L. paracasei ATCC 25598 was the most effective probiotic strain in terms of in vitro antagonistic activity against $NA^R$ E. coli O157:H7, followed by L. rhamnosus GG, B. longum B6, and L. acidophilus ADH. The use of selected probiotic strains could be an effective pre-harvest intervention strategy to reduce the risk of $NA^R$ E. coli O157:H7 by maintaining a balanced microflora in animals and might provide many potential benefits in lieu of using antimicrobials.

• Korean Journal of Microbiology
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• v.23 no.1
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• pp.43-48
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• 1985

Strict anaerobic procedures and anaerobic chamber were employed in order to improve the isolation of obligate anaerobes from oral pyogenic infections. Also different culture media were utilized to maximize bacterial recovery. Two blood media: nalidixic acid Tween blood agar (NATB) and plain blood agar (BA), two non-blood media: nalidixic acid Tween agar (NAT) and Gifu anaerobic medium (GAM) were used and compared for their isolation efficacy. Specimens from seven patients were collected with syringe. After collection, the needle was sealed with sterilixed silicone rubber and brought to labortory. The time spent from specimen collection to its processing in anaerobic chamber usually was 15 min. Identification of isolated bacterial strains was done with the API-20A system. Increase in isolation of anaerobic vacteria was achieved. Obligate anaerobic bacteria isolated were 3.3 strains per specimen. This figure falls within the range of 1.9-4.4 strains per specimen reported in other countries. With respect to the media utilized, blood media were superior to non-blood media. NATB medium was effective especially for the isolation of Gram-positive cocci. A total of 15 species of Gram-negative rods was isolated and 12 of them belonged to Bacteroides.

• Pediatric Infection and Vaccine
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• v.15 no.2
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• pp.93-99
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• 2008

Fluoroquinolones have been widely used since the development of nalidixic acid because of the excellent spectrum of activity, superior tissue penetration, and convenient route of administration. Despite such advantages, the usage in children is limited by concerns of toxicity to cartilage, damage to joints in animal studies, and an increase in antibiotic resistance. However, pediatric use has been increasing under certain circumstances with no report of such adverse effects. Further study is required prior to recommendation for general use of fluoroquinolones in children. The careful administration of fluoroquinolones is recommended only in limited circumstances, such as failure of primary antibiotics and lack of alternative antibiotics.

• Journal of fish pathology
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• v.1 no.2
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• pp.95-101
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• 1988

During the period from August through October, 1988, 50 isolates of Edwardsiella tarda were isolated from 6 diseased cultured Channa argus in Dunchi island and Myung-ghi, near Pusan in Korea were examined by studying their biochemical and antibiotical reactions. The ill animals moved slowly and irregular-formed swimming at the surface of the corner. The symthoms were necrosis with hemorrhage on the body surface, head, gill region, and mouth. Some fish were observed dropsy of the belly. The bacteria grew slowly on Double Salmonella-Shigella agar, 24h, at $37^{\circ}C$ to form relatively small size (2mm diameter), smoothed and convexed form with transient or black in center of the colonis. They gave negative reactions to Voges-Proskauer, Simmon's citrate, urea, KCN (in growth), gelatin, arginine dehydrolase, phenylalanine deaminase and many sugars. The isolates showed positive reactions to $H_2S$ (in KIA agar), indol, Methyl-Red, motility, lysine and ornithine decarboxylase, and gas from glucose. 8 drugs tested as chloramphenicol, colistin, gentamicin, kanamycin, lincomycin, nalidixic acid spectinomycin, and tetracycline. All cultures were resistant to colistin, lincomycin and spectinomycin respectibly, but sensitive to kanamycin and nalidixic acid. Three strains showed resistance to chloramphenicol and 2 isolates among them were resistant to two drugs(gentamicin and tetracycline), coincidentally.

• Journal of fish pathology
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• v.28 no.1
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• pp.17-26
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• 2015

The purpose of this study is to explore the possibility of essential oils and flavonoids improving the performance of antibiotics, proving a higher efficacy in the presence of natural substances against Edwardsiella tarda and Streptococcus iniae. Increased efficacy was observed in several cases: both essential oils and flavonoids increased antibacterial efficacy of oxytetracycline and flumequine against E. tarda by 2-fold; essential oils and flavonoids increased antibacterial efficacy of nalidixic acid against E. tarda by 4-fold; flavonoids increased antibacterial efficacy of josamycin against S. iniae by 4-fold. The results obtained in this study suggest that essential oils and flavonoids might be especially useful in increasing the antimicrobial activity of nalidixic acid and josamycin against E. tarda and S. iniae in fish. Natural compounds examined in this study could also be useful to help decrease the overuse of antibiotics in fish.

• Journal of Microbiology and Biotechnology
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• v.29 no.3
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• pp.465-472
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• 2019

Several reports describe antimicrobial-resistance transfer among children and the community in outbreak situations, but transfer between a child and a caregiver has not been examined in child care facilities under normal circumstances. We investigated the transfer of antimicrobial-resistance genes, resistant bacteria, or both among healthy children and teachers. From 2007 to 2009, 104 Escherichia coli isolates were obtained from four teachers and 38 children in a child care center. Twenty-six cephem-resistant isolates were obtained from children in 2007 and 2008. In 2009, cephem-resistant isolates were detected in children as well as a teacher. Nalidixic acid-resistant isolates from the same teacher for 3 years showed low similarity (<50%) to each other. However, an isolate from a teacher in 2007 and another from a child in 2008 showed high similarity (87%). Pulsed-field gel electrophoresis revealed 100% similarity for four isolates in 2007 and one isolate in 2008, and also similarity among seven isolates carrying the virulence gene (CNF1). This study yielded the following findings: (1) a gene for extended-spectrum ${\beta}$-lactamase was transferred from a child to other children and a teacher; (2) a nalidixic acid-resistant isolate was transferred from a teacher to a child; and (3) a virulent bacterium was transferred between children.