• Biomedical Science Letters
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• v.13 no.2
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• pp.141-148
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• 2007

We determined the sequences of the quinolone resistance-determining region (QRDR) of gyrA and gyrB for 21 clinical strains of Enterobacteriaceae resistant to ciprofloxacin, norfloxacin and levofloxacin. The clinical strains were isolated from the specimens of three general hospitals in Busan. In the present study, we found mutations in type II topoisomerase (DNA gyrase) genes for all strains. We confirmed that some genera of Enterobacteriaceae of clinical specimen exhibited decreased sensitivity to fluroquinolone due to changes in Ser-83$\rightarrow$Leu and Asp-87$\rightarrow$Asn types on gyrA and alterations in Glu-465$\rightarrow$Arg and Ser-492$\rightarrow$Asn type on gyrB. All the twenty-one strains had a missense mutation in gyrA (codon 83 and 87). Three of them had an additional mutation in gyrB (codon 465 or 492), but one of them had an additional mutation in gyrB (codon 426, 427, 491, 495 and 496). The strains which had two mutations in type II topoisomerase genes (gyrA and gyrB) were significantly more resistant to fluoroquinolones than those with a single mutation in gyrA (mean MICs of ciprofloxacin: $\geq8\mu$g/ml, mean MICs of levofloxacin: $\geq16\mu$g/ml). Interestingly, the examination of silent nucleotide changes n the gyrA and gyrB genes revealed six different patterns of DNA polymorphism, respectively. Fifteen strains of the twenty-one strains bearing the gyrase A mutation shared the same polymorphism and eleven strains of the twenty-one strains bearing the gyrase B mutation shared the same polymorphism.

• Biomedical Science Letters
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• v.7 no.2
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• pp.85-89
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• 2001

Many Staphylococcus aureus strains produce enterotoxins causing food poisoning. Staphylococcal enterotoxins are classified by serological criteria into five major groups - subtype A to E. It is difficult, time-consuming, and expensive to detect staphylococcal enterotoxins in the clinical laboratory. In this study, we fried to detect the enterotoxin genes of Staphylococcus aureus strains isolated from clinical specimens and Kimbap - rice rolled in a sheet of laver - using multiplex PCR technique. A total of 77 strains of Staphylococcus aureus from clinical specimens and 78 strains from Kimbap were isolated. Among clinical isolates of S. aureus, 60 strains (78.0%) were identified as producing enterotoxins. A total offs strains (91.6%) in the 60 staphylococcal enterotoxin producing strains were enterotoxin subtype C. In case of kimbap: 43 (55.1%) strains were detected to produce enterotoxins and 39 (90.6%) enterotoxin producing strains were subtype A.

• Korean Journal of Clinical Laboratory Science
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• v.37 no.3
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• pp.155-163
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• 2005

The purpose of this study is to investigate the carrier rate of S. aureus in the community, antibiotic susceptibility patterns of the organism, detection of MRSA and mecA gene in MRSA. Identification and antibiotic resistance patterns of S. aureus and MRSA were done by MicroScan Panels. MRSA strain was confirmed by disk diffusion method using oxacillin disk. The mecA gene in MRSA was detected by PCR. Eighty-four strains (27.4%) of S. aureus were isolated from the nasal specimens of 307 university students in Busan in 2004. Sixty-eight strains (81.9%) of 83 S. aureus were resistant to penicllin, 16 strains(19.3%) to erythromycin, 15 strains (18.1%) to gentamicin, 12 strains (14.5%) to tetracycline, 6 strains (7.2%) to chloramphenicol, 3 strains (3.6%) to ofloxacin, 2 strains (2.4%) to cefepime, clindamycin, imipenem, meropenem, norfloxacin, respectively. One strain (1.2%) was resistant to ciprofloxacin, cefazolin, cefotaxime, cefuroxime, and oxacillin. And all the strains (100%) of 84 S. aureus were susceptible to amoxicilin/K clavulanate, ticarcillin/K clavulanate, trimethoprim/sulfamethoxazole, rifampin, syncroid, teicoplanin, and vancomycin. One strain of 84 S. aureus isolates was methicillin-resistant Staphylococcus aureus (MRSA). The mecA gene was detected from the MRSA strain.

• Korean Journal of Clinical Laboratory Science
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• v.41 no.4
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• pp.158-166
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• 2009

On the basis of morphological characteristics, of total 128 strains of from sputum of tuberculos inpatient were identified as A. fumigatus (61 strains), A. niger (37), A. flavus (26), A. versicolor (1), A. nidulans (1), A. clavatus (1) and Neosartorya fennelliae (1). These strains were re-identified according to recent Aspergillus classification system which is mainly based on molecular characteristics. The strains were grouped by randomly amplified polymorphic DNA (RAPD) techniques. The representative strains from each group were sequenced with partial ${\beta}$-tubulin gene and compared with those of reference strains in the Aspergillus and were identified by the sequence. The identification was confirmed by morphology examination. As the results, they are reidentified as A. fumigatus (58), A. niger (11), A. tubingensis (26), A. flavus (27), A. sydowii (3), A. nidulans (1), A. clavatus (1) and Neosatorya fennelliae (1). This is the first report of A. tubuingensis in clinical field in Korea.

• Biomedical Science Letters
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• v.16 no.2
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• pp.75-82
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• 2010

The molecular epidemiological characteristics of methicillin-resistant Staphylococcus aureus (MRSA) isolates have demonstrated their genetic diversity and evolution. A total of 137 strains of MRSA clinical isolates was collected from Korean healthcare facility in 2007. The MRSA clinical isolates were analyzed by molecular typings (SCCmec element and agr locus typing), virule nce factor gene detections {(Panton-Valentine leukocidin (PVL), enterotoxin, exfoliative toxin and toxic shock syndrome toxin-1), and amplified fragment length polymorphism (AFLP)}. The MRSA clinical isolates were classified as SCCmec type II-agr type 1 (2 strains), type II-agr type 2 (79 strains), type III-agr type 1 (24 strains), type III-agr type 2 (2 strains), type IV-agr type 1 (27 strains), type IV-agr type 2 (2 strains), and non-typable (1 strain, agr type 3). Based on SCCmec types, SCCmec type II (95.1%) and III (88.5%) indicated higher multidrug resistance rate than SCCmec type IV (10.3%) (P<0.001). The most common enterotoxin genes were seg (83.8%), sei (83.1%), and sec (80.2%). The tst gene was present in 86 out of 137 (62.8%) MRSA isolates. All MRSA isolates were negative for PVL and exfoliative toxin genes. The combinations of toxin genes were observed in particular SCCmec types; 97.6% of SCCmec type II strains carried sec, seg, sei and tst genes, 73.0% of SCCmec type III strains carried sea gene, and 89.7% of SCCmec type IV strains carried sec, seg and sei genes. Each of the SCCmec types of MRSA isolates had distinct AFLP profile. In conclusion, SCCmec type II, agr type 1 and 2 have demonstrated to be the most common types in Korea, and the results indicated that the virulence factors are closely associated with their molecular types (SCCmec and agr types).

• International Journal of Oral Biology
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• v.38 no.1
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• pp.21-27
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• 2013

Anginosus group streptococci (AGS) were classified based on the nucleotide sequences of the 16S rRNA gene (16S rDNA) and comprised Streptococcus anginosus, Streptococcus intermedius, and Streptococcus constellatus. It is known that AGS is a causative factor of oral and systematic diseases. The purpose of this study was to discriminate the 56 clinical strains of AGS isolated from Korean oral cavities using phylogenetic analysis of 16S rDNA and species-specific PCR at the species-level. The 16S rDNA of clinical strains of AGS was sequenced using the dideoxy chain termination method and analyzed using MEGA version 5 software. PCR was performed to identify the clinical strains using species-specific primers described in previous studies and S. intermedius-specific PCR primers developed in our laboratory. The resulting phylogenetic data showed that the 16S rDNA sequences can delineate the S. anginosus, S. intermedius, and S. constellatus strains even though the 16S rDNA sequence similarity between S. intermedius and S. constellatus is above 98%. The PCR data showed that each species-specific PCR primer pair could discriminate between clinical strains at the species-level through phylogenetic analysis of 16S rDNA nucleotide sequences. These results suggest that phylogenetic analysis of 16S rDNA and PCR are useful tools for discriminating between AGS strains at the species-level.

• The Journal of the Korean Society for Microbiology
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• v.34 no.6
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• pp.513-518
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• 1999

A total of 113 Vibrio sp. strains were examined for plasmid content which were subjected to digestion with restriction enzymes. About the 55% Vibrio spp. have the plasmid more than one. Most of these plasmid various derivatives ranged from $2.4\;kb{\sim}23\;kb$, especially two strains of V. mimicus and one strain of V. furnissii carried one high-molecular weight plasmid (molecular weight ranging between $70\;kb{\sim}100\;kb$). Results of restriction analysis for plasmid of this three strains were by no means the rule. For detection of tdh and ctx gene, the virulence factor involved in the pathogenesis, we carried out the TDH and CT assay, PCR amplification, and hybridization. A total 11 strains were produced TDH, involved in 9 strains of V. parahaemolyticus and 1 strain of V. alginolyticus from clinical isolates and 1 strains of V. mimicus from environmental isolates. In the experiments of tdh gene detection, in all, 3 strains of V. parahaemolyticus from clinical isolates and 2 strains from environmental isolates could be successfully amplified in 400 bp by PCR. The PCR results were consistent with DNA hybridization tests. In the experiments of CT assay, in all, 3 strains of V. cholerae from clinical isolate and 1 strain of V. cholerae from environmental isolates were observed CT-producing. These CT-producing strains amplified in 302 bp by PCR for the detection of ctx gene. All CT-producing strains hybridized with digoxigenin-labeled DNA probe, while CT-negative strains did not hybridize. Also hybridization tests results for detection of ctx gene consistent with PCR.

• Biomedical Science Letters
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• v.11 no.4
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• pp.525-531
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• 2005

Staphylococcus aureus is a major cause of nosocomial infections and is one of the most commonly isolated bacterial species in the hospital and continues to be an important pathogen in both community and hospital-acquired infection. Methicillin resistant S. aureus (MRSA), which is associated with hospitals is now being isolated in the community. The purpose of this study is to investigate the carrier rate of S. aureus in the community, antibiotic resistance patterns of the organism, detection of MRSA and mecA gene in MRSA. Ninety strains $(46.4\%)$ of S. aureus were isolated from the nasal specimens of 194 elementary school students. Eighty-nine strains $(98.9\%)$ of 90 S. aureus were resistant to penicilin, 36 strains $(40.0\%)$ to erythromycin, 14 strains $(15.6\%)$ to fusidic acid, 11 strains $(12.2\%)$ to gentamycin, 9 strains $(10.0\%)$ to tobramycin, 5 strains $(5.6\%)$ to oxacillin, 4 strains $(4.4\%)$ to clindamycin, 2 strains $(2.2\%)$ to tetracycline, 1 strains $(1.1\%)$ to fosfomycin. None of $90(0\%)$ S. aureus isolates was resistant to ciprpfloxacin, trimethoprim/sulfamethoxazole, levofloxacin, linezolid, moxifloxacin, nitrofurantoin, norfloxacin, rifampicin, quinupristin/dalfopristin, teicoplanin, and vancomycin. Five strains $(5.6\%)$ of 90 S. aureus isolates were MRSA. The mecA gene was detected from five MRSA strains by PCR.

• Korean Journal of Veterinary Research
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• v.61 no.2
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• pp.12.1-12.9
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• 2021

The mosquito-borne pathogen Zika virus may result in neurological disorders such as Guillain-Barré syndrome and microcephaly. The virus is classified as a member of the Flaviviridae family and its wide spread in multiple continents is a significant threat to public health. So, there is a need to develop animal models to examine the pathogenesis of the disease and to develop vaccines. To examine the clinical profile during Zika virus infection, we infected neonatal and adult wild-type mice (C57BL/6 and Balb/c) and compared the clinical signs of African-lineage strain (MR766) and Asian-lineage strain (PRVABC59, MEX2-81) of Zika virus. Consistent with previous reports, eight-week-old female Balb/c mice infected with these viral strains showed no changes in body weight, survival rate, and neurologic signs, but demonstrated increases in the weights of spleens and hearts. However, one-day-old neonates showed significantly lower survival rate and body weight with the African-lineage strain than the Asian-lineage strain. These results confirmed the pathogenic differences between Zika virus strains. We also evaluated the clinical responses in neonatal and adult mice of different strains. Our findings suggest that these are useful mouse models for characterization of Zika virus for vaccine development.

• Korean Journal of Clinical Laboratory Science
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• v.37 no.3
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• pp.149-154
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• 2005

Fifty-one extended-spectrum-${\beta}$-lactamase(ESBL) producing Klebsiella pneumoniae strains were isolated from national university hospitals. All K. pneumoniae strains showed resistance to broad-spectrum antibiotic and most of them presented resistance to amikacin, gentamicin and ciprofloxacin. The results of amplified polymorphic DNA (RAPD) pattern for randomly isolated fifty-one strains were as follows; both twenty-one strains from Chungnam National University hospital and ten strains from Chungbuk National University hospital showed RAPD type Ia and Ib. However, twenty strains isolated from Gyeongsang National University hospital belonged to RAPD type IIa and IIb. All isolates were divided into four molecular types and showed high level of genetic diversity. These results suggested that RAPD analysis provided a rapid and simple method for analysing genotypes of ESBL.