• Journal of Dairy Science and Biotechnology
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• 제39권1호
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• pp.1-8
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• 2021

The surroundings of livestock farms, including dairy farms, are known to be a major source of development and transmission of antibiotic-resistant bacteria. To control antibioticresistant bacteria in the livestock breeding environment, farms have installed livestock wastewater treatment facilities to treat wastewater before discharging the final effluent in nearby rivers or streams. These facilities have been known to serve as hotspots for inter-bacterial antibiotic-resistance gene transfer and extensively antibiotic-resistant bacteria, owing to the accumulation of various antibiotic-resistant bacteria from the livestock breeding environment. This review discusses antibiotic usage in livestock farming, including dairy farms, livestock wastewater treatment plants as hotspots for antibiotic resistant bacteria, and nonenteric gram-negative bacteria from wastewater treatment plants, and previous findings in literature.

• 미생물학회지
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• 제53권4호
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• pp.316-319
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• 2017

하수처리장 방류수와 하천 중의 항생제 내성인자 분포에 대한 상관성을 분석하기 위해 방류수와 상류 하천수, 하류 하천수를 대상으로 항생제 내성유전자와 전파 관련 유전자를 조사하였다. 3개 지점에서 134~183개의 항생제 내성유전자(ARG) 및 전파 관련 유전자(MGE)가 검출되었으며, 1개의 16S rRNA 유전자에 대한 ARG 및 MGE 유전자의 상대적인 총 합이 0.063~0.422 copy로 분석되었다. ARG와 MGE의 수와 존재량은 방류수에서 가장 높게 검출된 반면, 총 세균 수는 가장 적게 검출됨으로서 하수처리 과정에서 사멸된 세균에 포함된 유전자들이 검출된 것으로 판단된다. 또한 MGE의 존재량 양상이 ARG의 존재량과 상관관계를 보임으로서 항생제 내성균들의 내성기작이 자연내성보다는 획득내성일 가능성을 제시하였다.

• 한국식품위생안전성학회지
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• 제22권2호
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• pp.116-119
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• 2007

돼지로부터 분리한 eae+Escherichia coli 67주에 대한 항생제 감수성 시험 결과, Ne에 41.8%, Li에 74.6%, DFX에 73.1%, ENR에 64.2%, Cef에 98.5%의 감수성을 나타내었다. 총 8종의 항생제에 대한 E. coli의 내성패턴을 분석하였을 때 12가지 내성 패턴을 나타내었으며, 그 중 4 제, 3 제 및 6제에 각각 26주(39%), 16 주(24%), 10주(14.9%)로 높았으며, 7종 항생제에 대해 내성을 나타내는 균주도 6주(8.9%)가 확인되었다. 본 실험에 의하면 최근에 사용되기 시작한 항생제의 경우 항생제 내성의 출현이 활발하지 않았으며, 지속적으로 노출된 항생제에 대해서는 감수성이 현저히 낮은 것으로 나타났다. Penicillin, Tetracycline, Neomycin은 본 실험에서 100%의 내성을 나타내며 돈육에서 분리되는 대장균간에 내성 전이가 활발한 것으로 추정되었다.

• Journal of Microbiology and Biotechnology
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• 제20권1호
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• pp.45-53
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• 2010

We have developed an efficient and precise method for genome manipulations in Bacillus subtilis that allows rapid alteration of a gene sequence or multiple gene sequences without altering the chromosome in any other way. In our approach, the Escherichia coli toxin gene mazF, which was used as a counter-selectable marker, was placed under the control of a xylose-inducible expression system and associated with an antibiotic resistance gene to create a "mazF-cassette". A polymerase chain reaction (PCR)-generated fragment, consisting of two homology regions joined to the mazF-cassette, was integrated into the chromosome at the target locus by homologous recombination, using positive selection for antibiotic resistance. Then, the excision of the mazF-cassette from the chromosome by a single-crossover event between two short directly repeated (DR) sequences, included in the design of the PCR products, was achieved by counter-selection of mazF. We used this method efficiently and precisely to deliver a point mutation, to inactivate a specific gene, to delete a large genomic region, and to generate the in-frame deletion with minimal polar effects in the same background.

• 대한의생명과학회지
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• 제10권2호
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• pp.153-161
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• 2004

Antibiotic resistance is often associated with the production of inner membrane proteins (for example, AcrAB/TolC efflux pump) that are capable to extrude antibiotics, detergents, dyes and organic solvents. In order to evaluate the unknown MarB function of Escherichia coli, especially focused on the function of OmpF porin, several mutants were construted by T4GT7 transduction. MarA plays a major roles in mar (multiple antibiotic resistance) phenotype with AcrAB/TolC efflux pump in E. coli K-12. Futhermore, MarA decreases OmpF porin expression via micF antisense RNA. Expression of acrAB is increased in strains containing mutation in marR, and in those carrying multicopy plasmid expressing marA. MarB protein of E. coli K-12 showed its activity at OmpF porin & TolC protein as target molecule. Some paper reported MarB positively regulates OmpF function. MarA shows mar phenotype, and MarB along with MarA show decreased MIC through OmpF function. By this experiment, MarB could decrease MIC through the OmpF porin & TolC protein as target.

• Journal of Microbiology and Biotechnology
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• 제15권3호
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• pp.491-496
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• 2005

The biosynthetic gene cluster for the aminoglycoside antibiotic kasugamycin was isolated and characterized from the kasugamycin producing strain, Streptomyces kasugaensis KACC 20262. By screening a fosmid library using kasA, the gene encoding aminotransferase, we isolated a 22 kb DNA fragment. The fragment contained seventeen complete open reading frames (ORFs); one of these ORFs, kasD, was identified as the gene for dNDP-glucose 4,6-dehydratase, which catalyzes the conversion of dNDP-glucose to 4-keto-6-deoxy-dNDP-glucose. The enzyme showed a broad spectrum of substrate specificity. In addition, ksR was overexpressed in E. coli BL21 and proved to be a self-resistance gene against kasugamycin. These findings suggest that the isolated gene cluster is highly likely responsible for the biosynthesis of kasugamycin.

• 한국식품위생안전성학회지
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• 제38권5호
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• pp.381-389
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• 2023

비브리오패혈증균은 세계에서 치사율이 50%에 달하는 가장 치명적인 수인성식품매개 병원균으로 해수에서 흔히 있으며, 특히 따뜻한 계절에 발생한다. 본 연구는 제주도의 해수, 유통 수산물, 수족관물에서 분리한 비브리오패혈증균에 대해서 RT-PCR을 이용한 독소 유전자, Vitek을 이용한 항생제 내성, PFGE를 이용한 유전적 특성을 조사하였다. 총 487개의 시료를 조사한 결과 비브리오패혈증균 46주(중복 균주 포함)가 해수에서 44주, 유통수산물에서 1주, 수족관물에서 1주 분리되었다. rtxA, viu와 같은 독소 유전자는 각각 8주(17.4%), 9주(19.6%) 검출되었고, vvhA와 같은 독소 유전자는 모든 균주에서 검출되었다. 항생제 내성 실험결과 cefoxitin 항상제에 대해서 100% 내성이 나타났다. 비브리오패혈증균 46주에 대한 PFGE 분석 결과 총 6유형이 100% 상동성을 보였고, 유사도는 81.3-98.0%로 나타났다. 수산물과 수족관물에서 분리된 비브리오패혈증균은 해수와의 상동성 결과 유사도는 불일치로 나타났고 지역과 시료 사이에는 유사성이 없었다. 독소 유전자를 가진 비브리오패혈증균에 의한 식중독 환자가 제주도에서 발생한 점을 고려해볼 때, 해수, 유통 수산물, 수족관물에서 분리한 비브리오패혈증균에 대한 모니터링이 지속되어야 할 것으로 보인다.

• 한국축산식품학회지
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• 제35권4호
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• pp.502-506
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• 2015

The aim of this study was to investigate the antimicrobial resistance profiles of and the enterotoxin gene distribution in 4 strains of Staphylococcus aureus (S10-2, S10-3, S12-2, and S13-2) isolated from 90 bulgogi samples. The S. aureus enterotoxin H gene (seh) was found in all the strains, while the S. aureus enterotoxin A gene (sea) was found only in 3 of the 4 strains. The S10-2 strain expressed a combination of enterotoxin genes - seg, seh, sei, sej, selm, and seln. The strains S10-2 and S13-2 were resistant to ampicillin and penicillin G, and all the isolated strains were resistant to tetracycline. The S10-2 strain was the only mecA-positive strain; it was also resistant to β-lactam antibiotics. Thus, genes encoding enterotoxin as well as those conferring antibiotic resistance were identified in the S. aureus strains isolated from pork bulgogi. These results represents the potential occurrence of MRSA in pork bulgogi, and the need for a monitoring system for pork bulgogi in order to prevent an outbreak of staphylococcal food poisoning.

• 대한임상검사과학회지
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• 제43권2호
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• pp.68-74
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• 2011

Pseudomonas aeruginosa is an aerobic, Gram-negative, glucose-nonfermenting bacterium, which has emerged as a serious opportunistic pathogen. Recently, outbreaks of carbapenem resistant P. aeruginosa give rise to significant therapeutic challenges for treating nosocomial infections. The genes of metallo-${\beta}$-lactamase (MBL), a powerful carbapenemase, are carried as a part of the mobile gene cassettes inserted into integrons playing an important role in rapid dissemination of antibiotic resistance genes among bacterial isolates. In this study, we investigated the prevalence of integron in imipenem resistant P. aeruginosa isolates. A total of 61 consecutive, non-duplicate, and imipenem resistant P. aeruginosa strains were isolated from a university hospital in the Chungcheong province of Korea. We employed repetitive extragenic palindromic sequence-based PCR (rep-PCR) method for the selection of clonally different P. aerusinosa strains. PCR and DNA sequencing were conducted for the detection of integrons. Twenty-one clonally different P. aeruginosa strains were isolated. Only one (P28) of the strains harbored $bla_{VIM-2}$ that was found as gene cassettes in class 1 integrons. Four of 21 carbapenem resistant P. aeruginosa strains harbored class 1 integron containing aminoglycoside resistance determinant. All of the integrons detected in the study contained more than one resistance gene cassette, which can mediate resistance to multiple antibiotics. To prevent further spreading of the multi-drug resistant P. aeruginosa, conseguent monitoring and clinical polices are required.

• 환경생물
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• 제38권2호
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• pp.289-298
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• 2020

As part of the research program "2018 Rapid screening and identification of freshwater microorganisms using MALDI-TOF/MS library" freshwater samples were collected from a branch of the Nakdong River. Almost 300 antibiotic-resistant bacterial strains were isolated from freshwater samples and subsequently identified by 16S rRNA gene sequencing. Seventeen strains among the isolates shared high 16S rRNA gene sequence similarity (>99.0%) with known species that were not previously recorded in Korea, and each of the isolates also formed a robust phylogenetic clade with the closest species. These species were phylogenetically diverse, belonging to four phyla, seven classes, 10 orders, and 13 genera. At the genus and class level, the previously unrecorded species belonged to Rhodovarius, Xanthobacter, and Shinella of the class Alphaproteobacteria; Ottowia, Simplicispira, and Zoogloea of Betaproteobacteria; Pseudomonas, Acinetobacter, and Shewanella of Gammaproteobacteria; Arcobacter of Epsilonproteobacteria; Sphingobacterium of Sphingobacteriia; Trichococcus of Bacilli; and Leucobacter of Actinobacteria. The previously unrecorded species were further characterized by examining their gram-staining, colony and cell morphology, biochemical properties, and phylogenetic position.