• 한국미생물·생명공학회지
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• 제27권3호
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• pp.215-222
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• 1999

Methylotrophic actinomycetes No. 155 produced an aminoglycoside antibiotics(AG)-resistant inhibitor. We have previously reported that the inhibitor shows strong inhibition to sisomicin-resistant strain. In order to understand the functions of inhibitor and sisomicin-resistance, characterizations and purification of inhibitor were investigated. Strain No. 155 was tentatively identified as Nocardiopsis sp. based on morphological and some physiological characteristics. In the antimicrobial activity test, the addition of inhibitor to sisomicin showed a reduction effect of MIC on the test strains such as Gram(+), Gram(-) bacteria and yeasts. The combination of the inhibitor and various antibiotics revealed synergistic against E. coli K-12 and B. subtilis PCI 219. The induced intracellular proteins from sisomicin-resistant strain exhibited the sisomicin inactivation by invitro test. And the induced intracellular proteins were inactivated by addition of the inhibitor. The inhibitor compound was purified by anion exchange chromatography(Dowex-1) and HPLC using Asahipak ES-502C column. The purified inhibitor compound was detected in a single peak(above 98.5% purity) through the HPLC analysis.

• Archives of Pharmacal Research
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• 제28권8호
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• pp.897-901
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• 2005

The in vitro inhibitory activities of essential oils from Thymus magnus and T. quinquecostatus as well as their main constituents were evaluated against susceptible and resistant species of Streptococcus pneumoniae, Staphylococcus aureus, Salmonella enteritidis, and Salmonella typhimurium. Notably, the essential oil fraction of T. magnus and its main components displayed significant inhibitory action against both antibiotic-susceptible and resistant strains of S. pneumoniae, S. aureus, and S. typhimurium with minimum inhibitory concentrations (MICs) ranging from 0.125 to 8 mg/mL. The differential MIC values imply that the oil fraction and its main components exhibit distinct patterns of activity against the tested bacterial species. Moreover, the disk diffusion test revealed that the inhibitory activities of oil fraction and components were dose-dependent. Data from the checkerboard titer test confirmed synergism between the antibiotic, norfloxacin, and T. magnus oil or thymol, particularly against the resistant strains of S. aureus.

• The Plant Pathology Journal
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• 제37권5호
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• pp.489-493
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• 2021

Bacterial canker is a devastating disease of kiwifruit caused by the bacterium Pseudomonas syringe pv. actinidiae. Canker disease of kiwifruit in Korea has been controlled using streptomycin for more than two decades. Four streptomycin-resistant strains, belonging to biovar 2, which are found only in Korea, were collected between 2013 and 2014 from different orchards located in Jeju, Korea. The genetic background for streptomycin resistance among P. syringe pv. actinidiae strains were determined by examining the presence of strA-strB or aadA, which are genes frequently found in streptomycin-resistant bacteria, and a point mutation at codon 43 in the rpsL gene. All four streptomycin-resistant strains of P. syringe pv. actinidiae investigated in this study contained strA-strB as a resistant determinant. The presence of the aadA gene and a mutation in codon 43 of the rpsL gene was not identified.

• 한국동물위생학회지
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• 제43권2호
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• pp.79-88
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• 2020

The aim of this study was to investigate the prevalence of CTX-M β-lactamase and plasmid-mediated quinolone resistance (PMQR) genes, and the pattern of antibiotic resistance in cefotaxime-resistant gramnegative bacteria. A total 126 gram-negative bacteria were isolated from hospitalized dogs and cats between 2018 and 2019. The most predominant isolates were E. coli (n=41), followed by Pseudomonas aeruginosa (n=25), Proteus mirabilis (n=14), Klebsiella pneumoniae (n=9), Sphingomonas paucimobilis (n=7), and Enterobacter cloacae and Serratia marcescens (respectively, n=5). Cefotaxime-resistant isolates were identified in 26.2% (33 isolates) of 126 gram-negative bacteria. CTX-M type β-lactamase were found in 15 isolates (10 E. coli, 1 Ent, cloacae and 4 K. pneumoniae, respectively). Among the CTX-M producing gram-negative bacteria, CTX-M-1 and CTX-M-9 were detected in 10 (66.7%) and 5 (33.3%) isolates, respectively. While, CTX-M-2 and CTX-M-8 were not found. PMQR genes were detected in 12 (36.4%) isolates (4 E. coli, 2 Ent, cloacae and 6 K. pneumoniae, respectively), and the predominant PMQR gene was aac(6')-lb-cr (n=9), followed by qnrB (n=8) and qnrS (n=1) alone or in combination. qnrA and qepA were not found. Additionally, 9 (60%) of 12 PMQR positive isolates were co-existence with CTX-M-1 or CTX-M-9. CTX-M or PMQR producing isolates showed highly resistance to penicillins (100%), cephalosporins (100~66.7%), monobactams (72.2%), and non-β-lactam antibiotics (94.4~61.1%) such as quinolones, trimethoprim/sulfamethoxazole, tetracycline and gentamicin. These findings showed CTX-M-1, CTX-M-9, aac(6')-lb-cr and qnrB were highly prevalent in cefotaxime-resistant Enterobacteriaceae isolates from companion animals in our region. Moreover, PMQR genes were closely associated with CTX-M type β-lactamase.

• 한국식품과학회지
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• 제54권2호
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• pp.209-217
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• 2022

본 연구에서는 모유 유래 유산균 E. faecalis BMSE-HMP005의 다제내성 균주에 대한 항균효과 및 probiotics로써 잠재적인 가능성을 확인하였다. E. faecalis BMSE-HMP005는 다제내성 균주 20주(Enterococcus spp., Staphylococcus spp., Escherichia spp., Pseudomonas spp., Salmonella spp., Klebsiella spp., Enterobacter spp.)에서 모두 MBC가 확인되어 다제내성 균주에 대한 우수한 항균효과를 입증하였다. 또한 RP-HPLC를 이용하여 배양액 내 bacteriocin을 확인하였으며, 이에 대한 분획은 gram 양성 및 gram 음성균주에서 모두 항균력이 나타나, E. faecalis BMSE-HMP005가 생산하는 bacteriocin의 광범위한 항균 스펙트럼을 입증하였다. E. faecalis BMSE-HMP005는 발암 화합물을 유발하는 β-glucuronidase에 대한 활성과 용혈성은 나타나지 않아 안전한 것으로 판단된다. E. faecalis BMSE-HMP005는 vancomycin에 대해서는 내성을 보이나, kanamycin (>0.058), ampicillin (>0.002), erythromycin (>0.002)은 EFSA 기준의 허용범위보다 낮은 MIC가 확인되었다. 또한 인공위액(pH 2.0) 및 인공 담즙산(0.3% bile acid) 조건에서 각각 98.67%, 95.70%의 생존율을 보였다. 이와 같은 결과는 본 연구에서 분리한 모유 유래 유산균 E. faecalis BMSE-HMP005가 다제내성 균주에 대한 우수한 항균활성을 갖는 probiotics로써 잠재적인 가능성을 보여준다. 따라서 건강기능식품의 기준 및 규격에 제시된 바와 같이 Enterococcus spp.는 항생제 내성 및 독성 유전자가 없는 경우에 한하여 probiotics로 사용이 가능한 고시하고 있어 E. faecalis BMSE-HMP005의 안전성에 대한 추가적인 검증이 필요할 것으로 판단된다.

• 한국환경보건학회지
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• 제50권2호
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• pp.93-101
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• 2024

Background: As pollutants caused by non-point sources flow into rivers, river water quality monitoring for fecal pollution is becoming increasingly important. Objectives: This study was conducted to investigate the distribution of microbial communities in the Yeongsangang River water system and sewage treatment plants in Gwangju and to evaluate their antibiotic resistance. Methods: In the experiment, samples were distributed to five selective media at each point and then cultured for 18 to 24 hours. When bacteria were observed, they were sub-cultured by size and shape and identified using MALDI-TOF MS equipment. When identification was completed, 17 types of antibiotic susceptibility tests were performed using VITEK II equipment, focusing on gram-negative dominant species among the identified strains. Results: During the study period, a total of 266 strains were isolated from 39 samples. Gram-positive bacteria were 37 strains in four genera, or 13.9% of the total, and Gram-negative bacteria were 229 strains in 23 genera, or 86.1% of the total. Antibiotic susceptibility testing of 23 strains, the major dominant species, showed that one strain (4.3%) was resistant to only one antibiotic, and two strains (8.7%) were 100% susceptible to the 17 antibiotics tested. The other 20 strains (87.0%) were multidrug resistant bacteria resistant to two or more antibiotics. There were various types of multidrug resistance. Among them, penicillin and cephalosporin series showed the highest resistance. Conclusions: Based on the results of this study, it was found that the bacterial community structure changed according to regional and environmental factors, and it was judged that continuous research such as genetic analysis of antibiotic-resistant bacteria present in natural rivers is necessary.

• Journal of Microbiology and Biotechnology
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• 제18권1호
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• pp.118-123
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• 2008

A new method for antimicrobial susceptibility testing of vitro-cultured bacteria on an ordinary fluorescence spectrometer was developed. The viable bacteria reduced 3-(4,5 dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) to produce insoluble particles that displayed intense resonance scattering light. The assay showed a linear relationship between the number of viable bacteria and the intensity of resonance scattering light. Dead bacteria were unable to reduce MTT. Methicillin-resistant Staphylococcus aureus exposed to flavonoids from Marchantia convoluta showed a flavonoids concentration-dependent inhibition of the ability to reduce MTT. In the assay, less than 12 h was required to attain susceptibility results and fewer bacteria were utilized than in traditional methods. The RLS technique could, in combination with the MTT assay, be a rapid and sensitive measuring method to determine the in vitro activity of new antimicrobials.

• 한국수산과학회지
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• 제43권1호
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• pp.33-38
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• 2010

Emerging of antibiotic resistance of pathogenic bacteria is now a very serious problem in the clinics to treat the diseases, which have been easy to cure by antibiotic treatments before. Unfortunately, antibiotics developed till now are not effective any more against the resistant bacteria. Lots of efforts to discover new antibiotics having novel and unique structures and functions are really urgent and undergoing in the whole world. In this study, we tried to screen and isolate Same unique bacterial strains producing antibacterial substances from the sea water, which is the poor environment for bacteria 10 make their growing. Three bacterial strains among 916 strains isolated showed inhibition clear zone on the marine agar plate growing pathogenic bacteria including Acinetobacter baumannii, Edwardsiella tarda, Pseudomonas aeruginosa, Staphylococcus aureus, Salmonella enterica. One of them, which was identified as Bacillus sp. DH-9 from 16S rRNA gene analysis, showed especially considerable antibacterial activity against S. aureus which is notorious for methicillin resistant S. aureus (MRSA). The growth of S. aureus was totally inhibited when the supernatant of Bacillus sp. DH-9 culture was treated on.

• Journal of Microbiology and Biotechnology
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• 제29권3호
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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.

• 한국수산과학회지
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• 제55권6호
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• pp.850-857
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• 2022

Seventy-five Vibrio parahaemolyticus isolates from the surface seawater of the Geum River Estuary area, on the west coast of Korea, were analyzed for the presence of virulence genes and susceptibility to 17 different antimicrobials. All 75 isolates were examined for the presence of two virulence genes (tdh or trh) using polymerase chain reaction; Only one of the isolates possessed the tdh or trh gene. According to the results of disk diffusion susceptibility tests, all of the strains were resistant to penicillin G, 92.0% were resistant to ampicillin, 82.7% were resistant to amoxicillin, 2.7% were resistant to ciprofloxacin, 2.7% were resistant to trimethoprim, 1.3% were resistant to cephalothin, and 1.3% were resistant to erythromycin. However, all of the strains were susceptible to amikacin, cefoxitin, chloramphenicol, gentamycin, kanamycin, nalidixic acid, nitrofurantoin, rifampin, streptomycin, and tetracycline. The average minimum inhibitory concentrations for ampicillin for V. parahaemolyticus was 557.6 ㎍/mL. These results not only provide novel insight into the necessity for seawater sanitation in Geum river estuary area, but they help reduce the risk of contamination of antimicrobial-resistant bacteria.