• 한국환경농학회지
• /
• 제41권4호
• /
• pp.335-343
• /
• 2022

BACKGROUND: Antibiotics used in animal husbandry for disease prevention and treatment have resulted in the rapid progression of antibiotic resistant bacteria which can be introduced into the environment through livestock feces/manure, disseminating antibiotic resistant genes (ARGs). In this study, fecal samples were collected from the livestock farms located in Jeju Island to investigate the relationship between microbial communities and ARGs. METHODS AND RESULTS: Illumina MiSeq sequencing was applied to characterize microbial communities within each fecal sample. Using quantitative PCR (qPCR), ten ARGs encoding tetracycline resistance (tetB, tetM), sulfonamide resistance (sul1, sul2), fluoroquinolone resistance (qnrD, qnrS), fluoroquinolone and aminoglycoside resistance (aac(6')-Ib), beta-lactam resistance (bla_TEM, bla_CTX-M), macrolide resistance (ermC), a class 1 integronsintegrase gene (intI1), and a class 2 integrons-integrase gene (intI2) were quantified. The results showed that Firmicutes and Bacteroidetes were dominant in human, cow, horse, and pig groups, while Firmicutes and Actinobacteria were dominant in chicken group. Among ARGs, tetM was detected with the highest number of copies, followed by sul1 and sul2. Most of the genera belonging to Firmicutes showed positive correlations with ARGs and integron genes. There were 97, 34, 31, 25, and 22 genera in chicken, cow, pig, human, and horse respectively which showed positive correlations with ARGs and integron genes. In network analysis, we identified diversity of microbial communities which correlated with ARGs and integron genes. CONCLUSION(S): In this study, antibiotic resistance patterns in human and livestock fecal samples were identified. The abundance of ARGs and integron genes detected in the samples were associated with the amount of antibiotics commonly used for human and livestocks. We found diverse microbial communities associated with antibiotics resistance genes in different hosts, suggesting that antibiotics resistance can disseminate across environments through various routes. Identifying the routes of ARG dissemination in the environment would be the first step to overcome the challenge of antibiotic resistance in the future.

• 대한수의학회지
• /
• 제49권3호
• /
• pp.195-200
• /
• 2009

Avian pathogenic Escherichia coli (APEC) is an important bacterial pathogen of chickens and causes colibacillosis such as airsacculitis, perihepatitis, omphalitis, peritonitis, salpingitis, and pericarditis. As the transfer of antibiotic resistance from animal to humans can be possible, surveillance on antibiotic resistance of APEC is very important. A total 34 APEC isolates from diseased chickens during the period from 2007 to 2009 were obtained. The susceptibility of the isolates to 13 antibiotics was determined by disc diffusion assay. Resistance to erythromycin was found in 97.1% of APEC isolated, followed by resistance to tetracycline (85.3%), doxycycline (82.3%), ampicillin (73.5%), sulfisoxazole (67.6%), enrofloxacin (67.6%), ciprofloxacin (64.7%), norfloxacin (61.7%) trimethoprim/sulfamethoxazole (52.9%), gentamycin (26.5%), amoxicillin (8.8%), colistin (5.9%), and amikacin (2.9%). The blaTEM genes were detected in 25 (100%) of the 25 ampicillin-resistant APEC isolates. Among the 29 tetracycline-resistant APEC isolates, tetA and tetB genes were detected in 18 (62.1%) and 9 (31%) isolates, respectively. Twenty six (76.5%) isolates were multiresistant to at least 6 antibiotics and seven (20.1%) isolates were multiresistant to at least 10 antibiotics. This results indicated that multiple antibiotic-resistant APEC is widespread in chicken flocks in Korea.

• 한국미생물·생명공학회지
• /
• 제48권3호
• /
• pp.389-398
• /
• 2020

The prevalence of carbapenem-resistant Enterobacteriaceae (CRE) is increasing globally, resulting in high mortality rates. Although CRE is a relatively recent problem in Korea (the first case was not diagnosed until 2010), it is responsible for serious morbidities at an alarming rate. In this study, we carried out a molecular genetic analysis to determine the incidence of CRE and carbapenemase-producing Enterobacteriaceae (CPE) at a general hospital in Korea between August 2017 and August 2019. Forty strains of CPE were isolated from various clinical specimens and analyzed via antimicrobial susceptibility testing, polymerase chain reaction to detect β-lactamase genes, deoxyribonucleic acid sequencing, multilocus sequence typing, curing testing, and conjugal transfer of plasmids. The results demonstrated that all 40 isolates were multidrug-resistant. The fluoroquinolone susceptibility test showed that 75% of the Enterobacteriaceae isolates were resistant to ciprofloxacin, whereas 72.5% were resistant to trimethoprim-sulfamethoxazole. Further, conjugation accounted for 57.5% of all resistant plasmid transfer events, which is 4.3-fold higher than that observed in 2010 by Frost et al. Finally, the high detection rate of transposon Tn4401 was associated with the rapid diffusion and evolution of CPE. Our results highlight the rapid emergence of extensively drugresistant strains in Korea and emphasize the need for employing urgent control measures and protocols at the national level.

• Journal of Microbiology
• /
• 제35권3호
• /
• pp.206-212
• /
• 1997

Heliobacillus mobilis is a strictly anaerobic Gram-positive bacterium which contains a primitive Photosystem I-type reaction center. The membrane-bound cytochrome $C_{553}$ from the heliobacterium suggested to be the immediate electron donor to the photooxidized pigment (P798+) has been isolated and characterized. The heme protein was visualized as a major component with an apparent molecular size of 17kDa in TMBZ-staining analysis of the membrane preparation and showed characteristic $\alpha$ (552.5 nm), $\beta$ (522nm), and Soret absorption (416 nm) peaks of a typical reduced c-type cytochrome in the partially purified sample. The internal 43 amino acid sequence of the electron donor was obtained by chemical agent and protease treatments followed by N-terminal sequencing of the resulting fragments. The internal sequence carries lots of lysine residues and a Cys-X-X-Cys-His sequence motif which are the characteristics of typical c-type cytochromes. The analysis of the sequence by FAST or FASTA program, however, did not show any significant similarity to other known heme proteins.

• Journal of Microbiology and Biotechnology
• /
• 제11권4호
• /
• pp.636-643
• /
• 2001

Bacillus sp. AIR-5, a strain from soil, produced an extracellular maltopentaose-forming amylase from amylose and soluble starch. This bacterium produced 8.9 g/l of maltopentaose from 40 g/l of soluble starch in a batch fermentation and the maltopentaose made up 90 % of the maltooligosaccharides produced (from maltose to maltoheptaose). The culture supernatant was concentrated using a 30 K molecular weight cut-off membrane and purified by DEAE-Cellulose and Sephadex G-150 column chromatographies. The purified protein showed one band on a native-PAGE and its molecular mass was estimated as 250 kDa. The 250-kDa protein was composed of tetramers of a 63-kDa protein. the isoelectric point of the purified protein was pH 6.9, and the optimum temperature for the enzyme activity was $45^{\circ}C$. The enzyme was quickly inactivated above $55^{\circ}C$, and showed a maximum activity at pH 8.5 and over 90% stability between a pH of 6 to 10. The putative N-terminal amino acid sequence of AIR-5 amylase, ATINNGTLMQYFEWYVPNDG, showed a 96% sequence similarity with that of BLA, a general liquefying amylase.

• Journal of Periodontal and Implant Science
• /
• 제45권6호
• /
• pp.223-228
• /
• 2015

Purpose: The goal of this study was to characterize the patterns of antimicrobial resistance and virulence genes in samples of Staphylococcus aureus (S. aureus) isolated from periodontitis patients. Methods: From July 2015 to August 2015, oral saliva was collected from a total of 112 patients diagnosed with periodontitis, including 80 outpatients in dental hospitals and 32 patients in dental clinics located in Seoul and Cheonan. The samples were subjected to a susceptibility test to evaluate the prevalence of antimicrobial resistance, and the pathogenic factors and antimicrobial resistance factors in the DNA of S. aureus were analyzed using polymerase chain reaction. Results: A susceptibility test against 15 antimicrobial agents showed that 88% of cultures were resistant to ampicillin, 88% to penicillin, and 2% to oxacillin. Resistance to at least two drugs was observed in 90% of cultures, and the most common pattern of multidrug resistance was to ampicillin and penicillin. Enterotoxins were detected in 65.9% of samples. The cell hemolysin gene hld was detected in 100% of cultures and hla was detected in 97.6% of samples. All strains resistant to penicillin and ampicillin had the blaZ gene. The aph(3')IIIa gene, which encodes an aminoglycoside modifying enzyme, was detected in 46.3% of samples. Conclusions: In the treatment of oral S. aureus infections, it is important to identify the pathogenic genes and the extent of antimicrobial resistance. Furthermore, it is necessary to study patterns of antimicrobial resistance and cross-infection in the context of periodontological specialties in which antimicrobials are frequently used, such as maxillofacial surgery, where the frequency of antimicrobial use for minor procedures such as implant placement is increasing.

• 대한의생명과학회지
• /
• 제18권3호
• /
• pp.299-306
• /
• 2012

Recently, the prevalence of 16S rRNA methylase conferring high-level resistance to aminoglycosides has been increasing in Gram-negative bacilli globally. We determined the prevalence and genotype of these methylase-producing bacteria, and characterized the co-resistance to ${\beta}$-lactam antibiotics and quinolone in Gram-negative clinical isolates collected in 2010 at a hospital in Korea. Among 65 amikacin-resistant isolates screened from 864 Gram-negative bacilli (GNB), 16S rRNA methylase genes were detected from 49 isolates, including Acinetobacter baumannii (43), Klebsiella pneumoniae (2), Proteus mirabilis (2) and Serratia marcescens (1), Empedobacter brevis (1). All of the 16S rRNA methylase genotype was armA and no variant sequences of amplified PCR products for armA were noted. The 16S rRNA methylase producing bacteria showed much higher resistance to aminoglycoside for Enterobacteriaceae and glucose non-fermenting (NF)-GNB and to imipenem for glucose NF-GNB, than the non-producing isolates. All of the 16S rRNA methylase producing Enterobacteriaceae had the extended-spectrum-${\beta}$-lactamase. In addition, two K. pneumoniae concurrently produced both plasmid-mediated AmpC ${\beta}$-lactamase and qnrB gene. All of the amikacin-resistant A. baumannii (43) co-harbored armA 16S rRNA methylase and $bla_{OXA-23}$ carbapenemase. In conclusion, 16S rRNA methylase producing bacteria were very prevalent among GNB in South Korea, and were commonly associated with co-resistance, including carbapenem and quinolone.

• Journal of Microbiology and Biotechnology
• /
• 제26권9호
• /
• pp.1643-1649
• /
• 2016

The aims of this study were to characterize the molecular epidemiological profiles of CTX-M-producing uropathogenic Escherichia coli isolates from a tertiary hospital in Daejeon, Korea, and to investigate the genetic diversity and compare the prevalence of sequence types (STs) in different areas. Extended spectrum β-lactamase-producing E. coli strains isolated from urine were analyzed for CTX-M, integrons, and insertion sequence common regions (ISCRs) by PCR and sequencing. Multilocus sequence typing (MLST), pulsed-field gel electrophoresis (PFGE), phylogenetic analysis, and rep-PCR were also used for molecular typing of the isolates. Of 80 CTX-M producers, 31 and 46 expressed CTX-M-15 and CTX-M-14, respectively. MLST analysis indicated that the most prevalent ST was ST131 (n = 34, 42.5%), followed by ST38 (n = 22, 27.5%), ST405 (n = 8, 10.0%), and ST69 (n = 6, 7.5%). Most CTX-M producers harbored class 1 integrons. ST131 strains belonged to phylogenetic group B2 and showed identical rep-PCR patterns, whereas ST69, ST38, and ST405 strains belonged to phylogenetic group D; the ST38 and ST405 strains displayed the same rep-PCR pattern, respectively. ST131 and ST38 isolates showed 21 and 19 distinct types, respectively, by PFGE. In Daejeon, D-ST38 CTX-M-14 producers were relatively more prevalent than in other countries and Korean cities. Our results indicate that CTX-M-producing E. coli isolates belonged mostly to ST131 or ST38 and were more related to hospital-onset than to community-onset infections and that the bla_CTX-M gene may vary according to the ST.

• Journal of Microbiology and Biotechnology
• /
• 제20권6호
• /
• pp.1042-1052
• /
• 2010

Forty-seven Salmonella Typhimurium (33 zoonotic, 14 clinical) strains were tested for antimicrobial resistance using the standard disk diffusion method. The presence of relevant resistance genes and class 1 integrons were investigated by using PCR. Pulsed-field gel electrophoresis (PFGE) and plasmid profiling were carried out to determine the genomic diversity of Salmonella Typhimurium. Approximately 57.4% of the S. Typhimurium strains were multidrug resistant (MDR) and showed high resistance rates to tetracycline (70.2%), sulfonamides (57.4%), streptomycin (53.1%), ampicillin (29.7%), nalidixic acid (27.6%), kanamycin (23.4%), chloramphenicol (21.2%), and trimethoprim (19.1%). Resistance towards cephalosporins was noted for cephalothin (27.6%), cephradine (21.2%), amoxicillin clavulanic acid (17.0%), and cephalexin (17.0%). Resistance genes, $bla_{TEM}$, strA, aadA, sul1, sul2, tetA, tetB, and tetC, were detected among the drug-resistant strains. Thirtythree strains (70.2%) carried class 1 integrons, which were grouped in 9 different profiles. DNA sequencing identified sat, aadA, pse-1, and dfrA genes in variable regions on class 1 integrons. Thirty-five strains (74.4%) were subtyped to 22 different plasmid profiles, each with 1-6 plasmids (2.0 to 95 kb). PFGE subtyped the 47 strains into 39 profiles. In conclusion, high rates of multidrug resistance were found among the Malaysian Salmonella Typhimurium strains. The emergence of multidrug-resistant Salmonella Typhimurium to cephalosporin antibiotics was also observed. The strains were very diverse and no persistent clone was observed. The emergence of MDR Salmonella Typhimurium is a worldwide problem, and this report provides information for the better understanding of the prevalence and epidemiology of MDR S. Typhimurium in Malaysia.

• 한국미생물·생명공학회지
• /
• 제32권2호
• /
• pp.101-109
• /
• 2004

Streptomyces avermitilis가 생산하는 이차대사산물인 avermectin $B_{la}$ (AVM $B_{la}$ /)의 생산성을 향상시키고자, 고생산성 균주를 융합파트너로 이용하여 원형질체 융합에 필요한 기본 실험조건을 확립하였고, 대량 선별시스템을 이용하여 다양한 융합균주들을 선별하였다. 특별한 표지인자가 없는 경우에도 원형질체 융합에 의해 유전자재조합체들을 선별할 수 있는 방법을 개발하였다. 즉 고생산성 균주의 원형질체(L-isoleucine유사체인 O-methylthreoiune또는 azaleucine에 대한 저항성 변이주의 원형질체를 치사율이 약 95%정도 되도록 UV나 NTG로 각 원형질체를 돌연변이시킨 후, 융합을 시도하여 재생된 변이주를 원형질 융합된 유전자재조합체로 간주하는 방법을 고안하였다. 돌연변이원으로 UV를 이용할 경우 대부분의 유전자재조합 균주들의 AVM $B_{la}$ 생산성이 융합 모균주들에 비해 높게 나타났으며, 주목할 만하게도 최고 3배 정도 향상된, 거의 산업용 균주의 생산성을 갖는 균주들을 선별할 수 있었다.