• Korean Journal of Clinical Laboratory Science
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• v.49 no.4
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• pp.427-434
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• 2017

Species that belong to the Acinetobacter calcoaceticus-baumannii (Acb) complex are major causes of hospital-acquired infections. They are important opportunistic pathogens. These species are usually multidrug resistant (MDR), and the therapeutic options to treat the infections caused by these species are limited. In the present study, we investigated fluoroquinolone resistance mechanisms in 53 ciprofloxacin resistant Acinetobacter species isolates in Chungcheong, Korea. Antimicrobial susceptibilities were determined using the disk-diffusion method. Detections of genes and identification of mutations associated with fluoroquinolone resistance were carried out using PCR and DNA sequencing. In our study, 47 out of 53 ciprofloxacin resistant Acinetobacter isolates harbored sense mutations at the 83rd residue (serine to leucine) in the gyrA gene as well as at the 80th residue (serine to leucine) in the parC gene. Among the 47 isolates harboring sense mutations in gyrA and parC gene, 44 isolates were A. baumannii and 3 isolates were A. pittii. Plasmid-mediated quinolone resistance (PMQR) determinants were detected in isolates in our study. Among the 46 ciprofloxacin resistant A. baumannii isolates, 41 showed type A, B, or F banding patterns on their REP-PCR profiles. This result suggests that clonal relation and horizontal spreading of the bacterial isolates have been around hospitals in Chungcheong area. To prevent colonization and disseminations of fluoroquinolone resistance Acb complex isolates, continuous investigation and monitoring of antimicrobial resistant determinants of MDR isolates are needed.

• Korean Journal of Clinical Laboratory Science
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• v.38 no.1
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• pp.26-33
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• 2006

Recently, the rapid increase in extended-spectrum ${\beta}$-lactamase (ESBL) producing clinical isolates has become a serious problem. In this study, the epidemiologic features and molecular characteristics of ESBL among clinical isolates of Escherichia coli and Klebsiella pneumoniae, antibiotic susceptibility testing, genotype of the ESBL and patterns of chromosomal DNA from PFGE (pulsed field gel electrophoresis) were observed. A total of 53 ESBL-producing clinical isolates (30 of E. coli and 23 of Klebsiella pneumoniae) were collected from two university hospitals in the period of June to July in 2002 and 2003 respectively. The antibiotic resistance frequency of those 53 strains was tested by the disk agar diffusion method with the result that all the strains were resistant to cephalothin. To other antibiotics, the resistance rates of E. coli (30 isolates) were in order of ceftazidime (90.0%), cefotaxime and aztreonam (respectively 83.3%). Also, the resistance rates of K. pneumoniae (23 isolates) were in order of aztreonam (78.3%), ceftazidime (73.9%) and cefotaxime (65.3%). Also the sensitivity of ceftazidime-clavulanic acid were 100% in E. coli and 95.7% in K. pneumoniae. And the sensitivity of cefotaxime-clavulanic acid was 96.7% in E. coli and 91.3% in K. pneumoniae. The types of the ESBL genes were determined by using polymerase chain reaction (PCR). Among the 30 isolates of ESBL-producing E. coli, 6 (20.0%) have SHV only, 5 (16.7%) have TEM only and, 18 (60.0%) have both of TEM and SHV. Among the 23 isolates of ESBL-producing K. pneumoniae, 7 (30.4%) have SHV only, 2 (8.7%) have TEM only, and 14 (60.9%) have both of TEM and SHV. These results show that 52 strains, with only one exception, were confirmed as either TEM or SHV. The patterns of Xba I-digested chromosomal DNA of ESBL-producing E. coli and K. pneumoniae isolates were analyzed by PFGE. PFGE patterns of E. coli and K. pneumoniae were multiclonal, but many strains were grouped into a few types. Therefore, it seems that there were clonal outbreaks or possible horizontal spread. In conclusion, the TEM and SHV ${\beta}$-lactamase are most widely spread in E. coli and K. pneumoniae in Korea. As these types are usually carried by plasmids, the spread of these ${\beta}$-lactamase genes could compromise the future usefulness of third generation cephalosporins for the treatment of infections caused by E. coli and K. pneumoniae.

• Journal of Food Hygiene and Safety
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• v.22 no.1
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• pp.45-51
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• 2007

The Collected 70 samples from 5 sandwich shops were analysed for the pathogenic bacteria such as Escherichia coli O157:H7, Salmonella spp., Listeria monocytogenes, and Staphylococcus aureus. As a result of Listeria monocytogenes and Saphylococcus aureus were detected in 1 sample, 11 samples, respectively. However, Escherichia coli O157:H7 and Salmonella spp. were not detected in anywhere. The antibiotics test of isolated bacteria was pelformed by the disk diffusion method from NCCLS. The resistance rate of Listeria monocytogenes isolates was confirmed 38.5% to 10 species such as Am, B, P, and Va for antibiotics of 26 species. MRSA was determinated 4 strains in S. aureus isolates. The resistance pattern of Staphylococcus aureus isolates were confirmed 36.4% to P Am OX B K E CXM, 18.2% to P Am B K E CXM B, 9.1% to P Am B K, 27.3% to P Am B, and 9.1% to Te B Nb. Therefore, continuous surveillance and monitoring for antibiotic resistance strains are demanded for prevention of increases in multiple antibiotic resistance strains.

• Journal of dental hygiene science
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• v.18 no.2
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• pp.76-84
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• 2018

Wet wipes are being increasingly used because of their convenience. Particularly, oral wet wipes are useful for regular cleaning of a baby's mouth after birth. Therefore, the consumption of oral wet wipes has increased over the past few years and a variety of products are commercially available. However, product information on safety is not sufficiently provided and still raises doubts regarding adverse effects. To confirm the safety of wet wipes as an oral hygiene item and provide information for their use, we investigated the cytotoxicity of oral wet wipes and verified the underlying mechanism. The anti-bacterial effect of oral wet wipes was analyzed using the disk diffusion method. The cytotoxic effects of oral wet wipes were observed based on morphological changes using microscopy and determined using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay in gingival epithelial cells and gingival fibroblasts. Evaluation of apoptosis by oral wet wipes was explored using propidium iodide flow cytometric analysis and a terminal deoxynucleotidyl transferase (TdT)-mediated deoxyuridine triphosphate (dUTP) nick-end labeling (TUNEL) assay. Apoptosis-related molecules were also analyzed using western blotting. Five types of oral wet wipes were tested, and two products from Fisher-Price and Dr. Kennedy revealed strong cytotoxic effects on gingiva epithelial cells and gingiva fibroblasts, although they also showed intense anti-bacterial effects on oral bacteria. Cell cycle arrest in the G2/M phase and apoptosis were observed based on treatment of extracts from Fisher-Price and Dr. KENNEDY. Relatively high TUNEL levels, reduction of proliferating cell nuclear antigen and cyclin-dependent kinase 4 expression, and fragmentation of poly (ADP-ribose) polymerase were also elucidated. These results suggest that commercial oral wet wipes could exert cytotoxic influences on oral tissue, although there are anti-bacterial effects, and careful attention is required, especially for infants and toddlers.

• Microbiology and Biotechnology Letters
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• v.38 no.3
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• pp.315-321
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• 2010

Malassezia furfur is an important causal factor for seborrheic dermatitis. Nowadays, the drugs available to treat this fungal infection are few. Several studies have documented the biological activity of essential oils. However, its antifungal properties are not completely understood, especially its anti-Malassezia activity. The aim of this study were to evaluate the effect of the plant essential oils on the growth of M. furfur using disk diffusion method and analyze by Gas chromatography-mass spectrometry (GC-MS) most active essential oils. In first screening, the 17 plant essential oils have possesses inhibitory activity against M. furfur at 2 mg/mL. Among the plant essential oils, oil of Citrus auranifoli was most active against M. furfur and its activity showed dose dependency. This anti-malassezial activity was high than that of itraconazole at 2 mg/mL. Oil of Citrus auranifolia also was phytochemically examined by GC-MS analysis, its main constituents were identified as limonene, ${\gamma}$-terpinene and terpinolene. It can be concluded that essential oils of Citrus auranifolia may have interesting applications to control fungal-derived diseases.

• Microbiology and Biotechnology Letters
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• v.43 no.4
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• pp.396-400
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• 2015

Enterobacteriaceae is one of the major families responsible for public health threats. Due to the emergence of pathogens with antibiotic resistance, great concern has been raised regarding the prevalence of antibiotic resistant bacteria in natural environments. Therefore, the diversity of Gram negative Enterobacteriaceae was investigated in water samples collected from five streams in Korea using the cultivation method. Profiling of multi-drug resistance was conducted with isolates via disk diffusion assay. The results indicated that the Gram negative Enterobacteriaceae consisted of the following genus; Citrobacter, Enterobacter, Escherichia, Klebsiella, Kluyvera, Pantoea, Plesiomonas, Raoultella, Shigella and Enterobacter. These latter strains represented 49% of identified isolates. In addition, 78.3% of the identified genus exhibited resistance against more than seven out of thirteen tested antibiotics, suggesting a high prevalence of multi-drug resistant bacteria in natural environments.

• Korean Journal of Clinical Laboratory Science
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• v.50 no.4
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• pp.422-430
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• 2018

The inappropriate and widespread use of quinolones in humans and animals may cause accelerated emergence and spread of antimicrobial-resistant determinants. In this study, we investigated quinolone resistance mechanisms in a total of 65 nalidixic acid-resistant E. coli isolated from swine rectal swabs (N=40) and clinical specimens (N=25). Antimicrobial susceptibilities were determined by the disk diffusion method. PCR and DNA sequencing were performed for investigations of genes and mutations associated with quinolone resistance. In our study, 62 of 65 nalidixic acid-resistant E. coli harbored mutations in gyrA, parC, and/or parE genes; of the 65 isolates, 62 (95.4%) had mutations in the gyrA gene, 35 (53.8%) had mutations in the parC gene, 7 (10.8%) had mutations in the parE gene. The 35 isolates harbored mutations in two genes, gyrA and parC. Plasmid-mediated quinolone resistance (PMQR) determinants were investigated in the 65 isolates. Thirteen of 65 nalidixic acid-resistant E. coli contained the qnrS gene and 10 of those isolates had mutations in the gyrA, parC, and/or parE genes. We confirmed that an important mechanism of quinolone resistance in E. coli isolated from human and swine involves chromosomal mutations in the gyrA, parC, and/or parE genes with increasing use of quinolone for treatment or additives.

• Korean Journal of Clinical Laboratory Science
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• v.50 no.4
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• pp.406-413
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• 2018

The emergence of carbapenem resistance among Pseudomonas aeruginosa has become an increasing problem worldwide. In particular, $metallo-{\beta}-lactamases$ (MBLs) are responsible for the high-level resistance to carbapenem. Sequence type 235 (ST235) has been found internationally in a multidrug-resistant clone and is involved in the dissemination of genes encoding IMP-6 and VIM-2. This study examined the prevalence of MBLs and the epidemiological relationship in carbapenem-resistant P. aeruginosa (CRPA) isolates obtained from a tertiary hospital in Daejeon, Korea, between March 2008 and June 2014. The antimicrobial susceptibilities were determined using the disk-diffusion method and PCR and DNA sequencing were used to identify the MBL genes. In addition, an epidemiological relationship was investigated by multilocus sequence typing (MLST). Among the 110 CRPA isolates, 32 isolates (29.1%) were MBL-producers; the major type was IMP-6 (29 isolates, 90.6%). VIM-2 was identified in 3 isolates (9.4%) of ST357. IMP-6-producing isolates were multidrug-resistant (MDR) and belonged to ST235. ST235 (55 isolates, 50.0%) was the clone most frequently detected and has gradually emerged during a seven-year period. To prevent the spread of MDR ST235 P. aeruginosa isolates, the current widespread use of carbapenems needs to be curtailed, and novel continuous monitoring strategies should be developed as soon as possible.

• Korean Journal of Clinical Laboratory Science
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• v.51 no.3
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• pp.301-308
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• 2019

The emergence and spread of multidrug resistant (MDR) Pseudomonas aeruginosa is a critical problem worldwide. The pathogenesis of P. aeruginosa is due partly to the production of several cell-associated and extracellular virulence factors. This study examined the distribution of virulence factors and antimicrobial resistance patterns of carbapenem-resistant P. aeruginosa (CRPA) isolated from a tertiary hospital in Daejeon, Korea. Antimicrobial susceptibility testing was performed using the disk diffusion method, and PCR and DNA sequencing were performed to determine for the presence of virulence genes. In addition, the sequence type (ST) of MDR P. aeruginosa was investigated by multilocus sequence typing (MLST). Among 32 CRPA isolates, 14 (43.8%) were MDR and the major ST was ST235 (10 isolates, 71.4%). All isolates were positive for the presence of virulence genes and the most prevalent virulence genes were toxA, plcN, and phzM (100%). All isolates carried at least eight or more different virulence genes and nine (28.1%) isolates had 15 virulence genes. The presence of the exoU gene was detected in 71.4% of the MDR P. aeruginosa isolates. These results indicate that the presence of the exoU gene can be a predictive marker for the persistence of MDR P. aeruginosa isolates.

• Korean Journal of Clinical Laboratory Science
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• v.54 no.4
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• pp.265-272
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• 2022

The emergence and dissemination of carbapenemase-producing Enterobacteriaceae (CPE), particularly the Klebsiella pneumoniae carbapenemase-2 (KPC-2) producing Klebsiella pneumoniae, has been rapidly increasing worldwide and is becoming a serious public health threat. Since the epidemiology and characteristics of these KPC-2-producing K. pneumoniae vary according to the region and period under consideration, this study investigated the prevalence of carbapenemases and the epidemiological relationship of 78 carbapenem-resistant K. pneumoniae (CRKP) isolated from a tertiary hospital in Daejeon, from March 2017 to December 2020. The antimicrobial susceptibility tests were identified using the disk-diffusion method. PCR and DNA sequencing were used to determine the carbapenemase genes. In addition, molecular epidemiology was performed by multilocus sequence typing (MLST). Among the 78 CRKP isolates, 35 isolates (44.9%) were carbapenemase-producing K. pneumoniae (CPKP) and the major carbapenemase type was KPC-2 (30 isolates, 85.7%). The New Delhi metallo-enzyme-1 (NDM-1) and NDM-5 were identified in 4 isolates (11.4%) and 1 isolate (2.9%), respectively. Multilocus sequence typing (MLST) analysis showed 10 sequence types (STs) and the most prevalent ST was ST307 (51.4%, 18/35). All the ST307 isolates were KPC-2-producing K. pneumoniae and were multidrug-resistant (MDR). In addition, ST307 has gradually emerged during a four-year period. These findings indicate that continuous monitoring and proper infection control are needed to prevent the spread of KPC-2-producing K. pneumoniae ST307.