• Journal of Microbiology and Biotechnology
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• 제24권1호
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• pp.8-12
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• 2014

Biofilm formation and antibiotic resistance are important determinants for bacterial pathogenicity. Ribonucleases control RNA degradation and there is increasing evidence that they have an important role in virulence mechanisms. In this report, we show that ribonucleases affect susceptibility against ribosome-targeting antibiotics and biofilm formation in Salmonella.

• 대한소아치과학회지
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• 제38권2호
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• pp.170-178
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• 2011

항생제 사용에 따라 구강내 세균들이 가지게 되는 내성의 발현이 문제가 될 수 있다. 어린이 치면세균막에서 치주질환의 원인균들과 흔히 사용하고 있는 항생제들에 대한 내성유전자의 출현율을 알아보고자 중합효소연쇄반응을 이용하여 조사하였다. 1. 치주질환 원인균의 출현율은 F. nucleatum 95.4%, T. forsythia 55.2% 이었으며, P. gingivalis 40.2%, A. actinomycetemcomitans 5.7%, T. denticola는 3.4% 순이었다. 2. 항생제 내성유전자의 출현율 조사에서 cephalosporin 분해효소인 cfxA는 100%에서 발견되었으며 ${\beta}$-lactam 분해효소인 $bla_{TEM}$과 tetracycline 내성유전자인 tet(M)도 100%의 출현율을 보였다. tet(Q)는 88.5%, ${\beta}$-lactam 분해효소인 $bla_{SHV}$는 29.9%, macrolide계 내성 ermF유전자는 87.4%, vancomycin 내성 vanA는 48.5%의 출현율을 보였다. Aminoglycoside에 대한 복합 내성을 보이는 aacA-aphD와 meticillin 내성유전자 mecA는 9.2%로 가장 낮은 출현율을 보였다. 3. 치주질환 원인균과 항생제 내성유전자와의 관련성 조사에서 T. forsythia와 $bla_{SHV}$간에 그리고 P. gingivalis와 vanA간 에 유의한 상관성이 있었다. 항생제 내성유전자 tet(Q)와 ermF (0.514)간에 중등도의 상관성을 나타내었으며, mecA와 vanA (0.25)간에 유의한 상관성을 나타내었다. 건강한 어린이들의 치면세균막에 다양한 치주질환 원인균들과 항생제 내성유전자들이 존재하며, 상호 관련성을 가지고 존재함을 보여주었다.

• Journal of Microbiology and Biotechnology
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• 제26권2호
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• pp.263-269
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• 2016

Temperate phages have been suggested to carry virulence factors and other lysogenic conversion genes that play important roles in pathogenicity. In this study, phage TEM123 in wild-type Staphylococcus aureus from food sources was analyzed with respect to its morphology, genome sequence, and antibiotic resistance conversion ability. Phage TEM123 from a mitomycin C-induced lysate of S. aureus was isolated from foods. Morphological analysis under a transmission electron microscope revealed that it belonged to the family Siphoviridae. The genome of phage TEM123 consisted of a double-stranded DNA of 43,786 bp with a G+C content of 34.06%. A bioinformatics analysis of the phage genome identified 43 putative open reading frames (ORFs). ORF1 encoded a protein that was nearly identical to the metallo-β-lactamase enzymes that degrade β-lactam antibiotics. After transduction to S. aureus with phage TEM123, the metallo-β-lactamase gene was confirmed in the transductant by PCR and sequencing analyses. In a β-lactam antibiotic susceptibility test, the transductant was more highly resistant to β-lactam antibiotics than S. aureus S133. Phage TEM123 might play a role in the transfer of β-lactam antibiotic resistance determinants in S. aureus. Therefore, we suggest that the prophage of S. aureus with its exotoxin is a risk factor for food safety in the food chain through lateral gene transfer.

• 한국어병학회지
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• 제36권2호
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• pp.287-292
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• 2023

This study investigated the genetic determinants of plasmid-mediated antibiotic resistance (PMAR) to quinolones and tetracycline in 106 Aeromonas strains isolated from eel (Anguilla japonica, 70 strains) and ornamental fish (36 strains) in Korea. Quinolones and tetracycline resistance phenotypes were found to be widely distributed throughout the both fish groups. However, the prevalence of qnr and tet genes was higher in ornamental fish strains than in eel strains (42.9% vs. 86.1% for qnr and 51.4% vs. 69.4% for tet). In addition, the profiling of the present genetic determinants revealed the dominance of qnrS, tetA, tetE and tetE+qnrS genes for eel strains but of tetA+qnrS qnrS and tetE+qnrS genes for ornamental fish strains. These results indicate that aquaculture and related industries could be a major threat to public health due to the possible spread of PMAR.

• Journal of Microbiology and Biotechnology
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• 제34권6호
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• pp.1276-1286
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• 2024

The environment has been identified as an origin, reservoir, and transmission route of antibiotic resistance genes (ARGs). Among diverse environments, freshwater environments have been recognized as pivotal in the transmission of ARGs between opportunistic pathogens and autochthonous bacteria such as Aeromonas spp. In this study, five environmental strains of Aeromonas spp. exhibiting multidrug resistance (MDR) were selected for whole-genome sequencing to ascertain their taxonomic assignment at the species-level and to delineate their ARG repertoires. Analyses of their genomes revealed the presence of one protein almost identical to AhQnr (A. hydrophila Qnr protein) and four novel proteins similar to AhQnr. To scrutinize the classification and taxonomic distribution of these proteins, all Aeromonas genomes deposited in the NCBI RefSeq genome database (1,222 genomes) were investigated. This revealed that these Aeromonas Qnr (AQnr) proteins are conserved intrinsic resistance determinants of the genus, exhibiting species-specific diversity. Additionally, structure prediction and analysis of contribution to quinolone resistance by AQnr proteins of the isolates, confirmed their functionality as quinolone resistance determinants. Given the origin of mobile qnr genes from aquatic bacteria and the crucial role of Aeromonas spp. in ARG dissemination in aquatic environments, a thorough understanding and strict surveillance of AQnr families prior to the clinical emergence are imperative. In this study, using comparative genome analyses and functional characterization of AQnr proteins in the genus Aeromonas, novel Aeromonas ARGs requiring surveillance has suggested.

• Journal of Veterinary Science
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• 제25권5호
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• pp.62.1-62.13
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• 2024

Importance: Antimicrobial resistance (AMR) is a serious public health threat. AMR bacteria and their resistance determinants in food can be transmitted to humans through the food chain and by direct contact and disseminate directly to the environment. Objective: This study examined the AMR characteristics and transferable R plasmids in Escherichia coli isolated from meat ducks raised in an open-house system. Methods: One hundred seventy-seven (n = 177) commensal E. coli were examined for their antimicrobial susceptibilities and horizontal resistance transfer. The plasmids were examined by PCR-based plasmid replicon typing (PBRT) and plasmid multi-locus sequence typing (pMLST). Results: The highest resistance rate was found against ampicillin (AMP, 83.0%) and tetracycline (TET, 81.9%), and most isolates exhibited multidrug resistance (MDR) (86.4%). The R plasmids were conjugally transferred when TET (n = 4), AMP (n = 3), and chloramphenicol (n = 3) were used as a selective pressure. The three isolates transferred resistance genes either in AMP or TET. The blaCTX-M1 gene resided on conjugative plasmids. Five replicon types were identified, of which Inc FrepB was most common in the donors (n = 13, 38.4%) and transconjugants (n = 16, 31.2%). Subtyping F plasmids revealed five distinct replicons combinations, including F47:A-:B- (n = 2), F29:A-:B23 (n = 1), F29:A-:B- (n = 1), F18:A-B:- (n = 1), and F4:A-:B- (n = 1). The chloramphenicol resistance was significantly correlated with the other AMR phenotypes (p < 0.05). Conclusions and Relevance: The meat ducks harbored MDR E. coli and played an important role in the environmental dissemination of AMR bacteria and its determinants. This confirms AMR as a health issue, highlighting the need for routine AMR monitoring and surveillance of meat ducks.

• 보건행정학회지
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• 제25권4호
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• pp.323-332
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• 2015

Background: Antibiotic resistance has been becoming serious challenge to human beings. Overuse of antibiotics, especially, for infants is concerned, but studies are very few for the prescribing pattern of antibiotic use for infants. This study analyzes prescribing patterns of antibiotics in outpatients of preschool children with acute respiratory tract infections in South Korea. Methods: Data are used from 2011 Health Insurance Review & Assessment Services-pediatric patients sample. Inclusion criteria is outpatient children (0 to 5 years) with top five frequent diseases. Prescription rates are analyzed by types of disease, provider, specialty, region, and ages. Binary or multinomial logit models are used to analyze determinants of providers' prescription pattern. Results: The main findings are as follows. First, distributions of prescription rates are shown as L-shape or M-shape depending on the types of disease. Second, the prescription variation is so large among providers, where providers are polarized as a group with low prescription rates and the other group with high prescription rates, though the shapes are shown diversified across types of disease. Third, prescription rates appear to be lower in pediatrics and higher in ENT (ear-nose-throat). Fourth, broad spectrum antibiotics are widely used among children. Finally, the logit analysis shows similar results with descriptive statistics, but partly different results across types of disease. Conclusion: Antibiotics for respiratory tract infections of infants are used excessively with a large variation among providers, and especially broad spectrum antibiotics are used. The prescription guideline for antibiotics should be provided for each specific disease to reduce antibiotic resistance in the future.

• The Korean journal of internal medicine
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• 제39권3호
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• pp.448-457
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• 2024

Background/Aims: Improved knowledge of local epidemiology and predicting risk factors of multidrug-resistant (MDR) bacteria are required to optimize the management of infections. This study examined local epidemiology and antibiotic resistance patterns of liver cirrhosis (LC) patients and evaluated the predictors of MDR bacteremia in Korea. Methods: This was a retrospective study including 140 LC patients diagnosed with bacteremia between January 2017 and December 2022. Local epidemiology and antibiotic resistance patterns and the determinants of MDR bacteremia were analyzed using logistic regression analysis. Results: The most frequently isolated bacteria, from the bloodstream, were Escherichia coli (n = 45, 31.7%) and Klebsiella spp. (n = 35, 24.6%). Thirty-four isolates (23.9%) were MDR, and extended-spectrum beta-lactamase E. coli (52.9%) and methicillin-resistant Staphylococcus aureus (17.6%) were the most commonly isolated MDR bacteria. When Enterococcus spp. were cultured, the majority were MDR (MDR 83.3% vs. 16.7%, p = 0.003), particularly vancomycin-susceptible Enterococcus faecium. Antibiotics administration within 30 days and/or nosocomial infection was a significant predictor of MDR bacteremia (OR: 3.40, 95% CI: 1.24-9.27, p = 0.02). MDR bacteremia was not predicted by sepsis predictors, such as positive systemic inflammatory response syndrome (SIRS) or quick Sequential Organ Failure Assessment (qSOFA). Conclusions: More than 70% of strains that can be treated with a third-generation cephalosporin have been cultured. In cirrhotic patients, antibiotic administration within 30 days and/or nosocomial infection are predictors of MDR bacteremia; therefore, empirical administration of broad-spectrum antibiotics should be considered when these risk factors are present.

• Journal of Microbiology and Biotechnology
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• 제29권6호
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• pp.962-972
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• 2019

Non-typhoidal Salmonella (NTS) is one of the most frequent causes of bacterial foodborne illnesses. Considering that the main reservoir of NTS is the intestinal tract of livestock, foods of animal origin are regarded as the main vehicles of Salmonella infection. In particular, poultry colonized with Salmonella Typhimurium (S. Typhimurium), a dominant serotype responsible for human infections, do not exhibit overt signs and symptoms, thereby posing a potential health risk to humans. In this study, comparative genomics approaches were applied to two S. Typhimurium strains, ST1539 and ST1120, isolated from a duck slaughterhouse and a pig farm, respectively, to characterize their virulence and antimicrobial resistance-associated genomic determinants. ST1539 containing a chromosome (4,905,039 bp; 4,403 CDSs) and a plasmid (93,876 bp; 96 CDSs) was phylogenetically distinct from other S. Typhimurium strains such as ST1120 and LT2. Compared to the ST1120 genome (previously deposited in GenBank; CP021909.1 and CP021910.1), ST1539 possesses more virulence determinants, including ST64B prophage, plasmid spv operon encoding virulence factors, genes encoding SseJ effector, Rck invasin, and biofilm-forming factors (bcf operon and pefAB). In accordance with the in silico prediction, ST1539 exhibited higher cytotoxicity against epithelial cells, better survival inside macrophage cells, and faster mice-killing activity than ST1120. However, ST1539 showed less resistance against antibiotics than ST1120, which may be attributed to the multiple resistanceassociated genes in the ST1120 chromosome. The accumulation of comparative genomics data on S. Typhimurium isolates from livestock would enrich our understanding of strategies Salmonella employs to adapt to diverse host animals.

• 약학회지
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• 제60권1호
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• pp.1-7
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• 2016

The aim of this study was to investigate the prevalence of quinolone resistant E. coli from retail meat and to characterize the resistant determinants. Determination of minimum inhibitory concentration, the sequence analysis of gyrA, gyrB, parC, and parE quinolone resistance determining regions (QRDR), the presences of plasmid mediated quinolone resistance (PMQR) and the expression of efflux pump genes were investigated. Of the total 277 retail meat samples, 67 coli form bacteria were isolated. 15 of 67 isolates showed nalidixic acid resistance and 7 of 15 nalidixic acid resistant isolates were also resistant to ciprofloxacin, moxifloxacin and levofloxacin. 11 of 15 nalidixic acid resistant strains were isolated from chicken, 2 of 15 were isolated from beef and 2 of 15 were isolated from pork samples. 11 of 15 nalidixic acid resistant strains have single mutation at codon 87 (D87N or D87G) in gyrA, 2 of 11 gyrA mutants have double mutations at codon 86 and 87 (L86A and L87I) in parC with mutations at codon 434+445+465 or 429 in gyrB. 2 of 15 resistant isolates harbored qnrS, a PMQR determinant. Over expression of the acrB gene, efflux pump gene (3.93~16.53 fold), was observed in 10 of 15 resistant isolates.