Biomedical subjects

Dong Hyeon Shin

Publications and source records attributed to Dong Hyeon Shin.

12 recordsLinked to original sources

PubMed2006

High-level vancomycin-resistant Staphylococcus aureus isolates associated with a polymicrobial biofilm.

Glycopeptides such as vancomycin are the treatment of choice for infections due to methicillin-resistant Staphylococcus aureus. This study describes the identification of high-level vancomycin-resistant S. aureus (VRSA) isolates in a polymicrobial biofilm within an indwelling nephrostomy tube in a patient in New York. S. aureus, Enterococcus faecalis, Enterococcus faecium, Micrococcus species, Morganella morganii, and Pseudomonas aeruginosa were isolated from the biofilm. For VRSA isolates, vancomycin MICs ranged from 32 to >128 microg/ml. VRSA isolates were also resistant to aminoglycosides, fluoroquinolones, macrolides, penicillin, and tetracycline but remained susceptible to chloramphenicol, linezolid, rifampin, and trimethoprim-sulfamethoxazole. The vanA gene was localized to a plasmid of approximately 100 kb in VRSA and E. faecium isolates from the biofilm. Plasmid analysis revealed that the VRSA isolate acquired the 100-kb E. faecium plasmid, which was then maintained without integration into the MRSA plasmid. The tetracycline resistance genes tet(U) and tet(S), not previously detected in S. aureus isolates, were identified in the VRSA isolates. Additional resistance elements in the VRSA isolate included a multiresistance gene cluster, ermB-aadE-sat4-aphA-3, msrA (macrolide efflux), and the bifunctional aminoglycoside resistance gene aac(6')-aph(2")-Ia. Multiple combinations of resistance genes among the various isolates of staphylococci and enterococci, including vanA, tet(S), and tet(U), illustrate the dynamic nature of gene acquisition and loss within and between bacterial species throughout the course of infection. The potential for interspecies transfer of antimicrobial resistance genes, including resistance to vancomycin, may be enhanced by the microenvironment of a biofilm.

Acetamides↗

PubMed2006

Antimicrobial susceptibility and clonal relatedness between community- and hospital-acquired methicillin-resistant Staphylococcus aureus from blood cultures.

We compared the antimicrobial resistance and clonal relationships among the community-acquired (CA) and hospital-acquired (HA) methicillin-resistant Staphylococcus aureus (MRSA) strains that were isolated from blood cultures in a university hospital over a 4-year period. A total of 131 MRSA isolates, including 28 CA-MRSA and 103 HA-MRSA strains, were identified; antimicrobial susceptibility testing indicated that the CA-MRSA isolates were more susceptible to erythromycin (21% vs 6%; P=0.02), clindamycin (46% vs 12%; P=0.01), ciprofloxacin (43% vs 11%; P=0.01), and gentamicin (43% vs 6%; P=0.01) than were the HA-MRSA isolates. Pulsed-field gel electrophoresis (PFGE) typing and antimicrobial resistance profiles separated the 20 CA-MRSA isolates into 14 and 10 different patterns, respectively, and the 53 HA-MRSA isolates were separated into 24 and 7 different patterns, respectively. Twenty-one (40%) of the 53 HA-MRSA isolates belonged to two predominant PFGE types, and most of them showed multi-drug resistant patterns. Four (20%) of the 20 CA-MRSA and 10 (19%) of the 53 HA-MRSA isolates fell into two common PFGE patterns, and each of them showed the same multi-drug resistant pattern. This study suggests that, although the CA-MRSA blood isolates showed diverse PFGE and antimicrobial resistance patterns, some of these isolates may have originated from the HA-MRSA strains.

Anti-Bacterial Agents↗

PubMed2005

Vibrio vulnificus endophthalmitis occurring after ingestion of raw seafood.

Ocular Vibrio vulnificus infections are quite rare, and all previously reported cases have been associated with exposure to seafood and seawater. Here, we report a case of endogenous endophthalmitis caused by V. vulnificus, occurring after the ingestion of raw seafood. This case was not associated with any cutaneous or other severe systemic manifestations.

Anti-Bacterial Agents↗

PubMed2004

Genetic relatedness among Candida tropicalis isolates from sporadic cases of fungemia in two university hospitals in Korea.

OBJECTIVE: To compare the epidemiology and genetic relatedness of Candida tropicalis isolates causing bloodstream infection (BSI) in two hospitals. SETTING: Two tertiary-care hospitals in Korea. METHODS: A retrospective molecular epidemiologic analysis using pulsed-field gel electrophoresis (PFGE) was performed with 49 C. tropicalis isolates from sporadic cases of BSI. The isolates were collected from 27 patients at Chonnam National University Hospital (CUH) during a 6-year period and 22 patients at Asan Medical Center (AMC) during a 2-year period. RESULTS: Based on the PFGE patterns, the average similarity value (S AB) for the 27 isolates from CUH was 0.84 +/- 0.08, which was significantly higher than that for the 22 isolates from AMC (0.78 +/- 0.06; P < .001). Of the 49 strains from patients at the 2 hospitals, 9 isolates were placed into 3 subtypes with S AB values of 1.0, which indicated that they were identical. All 9 of these strains were isolated from CUH patients, and each type strain was isolated sporadically during a period ranging from 4 months to 3 years. On comparison of the clinical characteristics of the patients of the 2 hospitals, the CUH strains were isolated more frequently from non-neutropenic patients and patients with central venous catheter-related fungemia; cases from CUH had a better outcome than those from AMC (P < .05). CONCLUSIONS: These data show that the clinical and epidemiologic characteristics of C. tropicalis fungemia may differ markedly among hospitals and that some cases of C. tropicalis fungemia may be caused by endemic strains within a hospital.

Adult↗

PubMed2004

Microevolution of Candida albicans strains during catheter-related candidemia.

We examined microevolution in a series of Candida albicans strains isolated from patients with catheter-related candidemia. Sixty-one isolates (29 from blood, 18 from catheters, 10 from urine, and 4 from other sites) were obtained from 15 patients who were admitted to the same hospital over a 3-year period. Isolates were analyzed by using Southern hybridization with the C1 fragment of Ca3 as a probe (C1 fingerprinting) and pulsed-field gel electrophoresis (PFGE). PFGE typing consisted of electrophoretic karyotyping (EK) and restriction endonuclease analysis of genomic DNA (REAG) by using SfiI (REAG-S) and BssHII (REAG-B). When catheter isolates were compared with blood isolates from the same patient, catheter isolates from 5 of 14 patients (36%) exhibited minor band differences (microevolution) relative to blood isolates in either C1 fingerprinting (n = 4), REAG-S (n = 3), or REAG-B (n = 5) profiles, although they had identical EK patterns. However, the other sequential isolates from each patient, which had identical EK patterns, showed the same REAG and C1 fingerprinting patterns. Both fingerprinting methods revealed that two distinct genotypes were shared by isolates from seven patients in a neonatal intensive care unit, suggesting two nosocomial clusters. Except for two catheter isolates from the index patients of each cluster, no consecutive isolates collected from each of the two clusters showed any microevolution during the 2- or 7-month cluster periods. The findings suggest that in catheter-related candidemia, some C. albicans strains undergo microevolution during catheter colonization.

Biological Evolution↗

PubMed2004

Pacemaker lead endocarditis caused by Achromobacter xylosoxidans.

We report the case of a 35-yr-old patient who presented with high fever and chills. He had undergone a patch closure of the ventricular septal defect 18 yr before. One year later, a VVI pacemaker was implanted via the right subclavian vein because of complete heart block. Nine years after that, a new VVI pacemaker with another right ventricular electrode was inserted controlaterally and the old pacing lead was abandoned. Trans-thoracic and trans-esophageal echocardiogram identified the pacemaker lead in the right ventricle (RV) attaching hyperechoic materials and also a fluttering round hyperechoic mass with a stalk in the RV outflow tract. Cultures in blood and pus from pacemaker lead grew Achromobacter xylosoxidans. A diagnosis of pacemaker lead endocarditis due to Achromobacter xylosoxidans was made. In this regards, the best treatment is an immediate removal of the entire pacing system and antimicrobial therapy.

Achromobacter denitrificans↗

PubMed2003

Pichia ohmeri fungemia associated with phlebitis: successful treatment with amphotericin B.

We report a case of fungemia caused by the yeast-form fungus Pichia ohmeriin a 59-year-old hospitalized patient. P. ohmeri was found in all of the patient's blood cultures collected on days 52, 57, 59, and 64 of his hospital stay. Intermittent fever developed on the 52nd hospital day and persisted for about 10 days. The patient had previously received intensive antimicrobial therapy for a ventriculoperitoneal shunt infection and subsequent nosocomial pneumonia. Although a central venous catheter was not used in the patient, he suffered from tender swelling of the right leg due to peripheral phlebitis at the site of insertion of a peripheral venous catheter (which had already been removed at the onset of fever), the same site from which P. ohmeri was isolated. The fungemia and phlebitis cleared following 14-day amphotericin B therapy. This case shows that P. ohmeri can be a nosocomial bloodstream pathogen associated with phlebitis.

Amphotericin B↗

PubMed2003

Characterization and pathogenic significance of Vibrio vulnificus antigens preferentially expressed in septicemic patients.

Many important virulence genes of pathogenic bacteria are preferentially expressed in vivo. We used the recently developed in vivo-induced antigen technology (IVIAT) to identify Vibrio vulnificus genes induced in vivo. An expression library of V. vulnificus was screened by colony blot analysis by using pooled convalescent-phase serum that had been thoroughly adsorbed with in vitro-expressed V. vulnificus whole cells and lysates. Twelve clones were selected, and the sequences of the insert DNAs were analyzed. The DNA sequences showed homologies with genes encoding proteins of diverse functions: these functions included chemotaxis (a methyl-accepting chemotaxis protein), signaling (a GGDEF-containing protein and a putative serine/threonine kinase), biosynthesis and metabolism (PyrH, PurH, and IlvC), secretion (TatB and plasmid Achromobacter secretion [PAS] factor), transcriptional activation (IlvY and HlyU), and the activity of a putative lipoprotein (YaeC). In addition, one identified open reading frame encoded a hypothetical protein. Isogenic mutants of the 12 in vivo-expressed (ive) genes were constructed and tested for cytotoxicity. Cytotoxic activity of the mutant strains, as measured by lactate dehydrogenase release from HeLa cells, was nearly abolished in pyrH, purH, and hlyU mutants. The intraperitoneal 50% lethal dose in mice increased by ca. 10- to 50-fold in these three mutants. PyrH and PurH seem to be essential for in vivo growth. HlyU appears to be one of the master regulators of in vivo virulence expression. The successful identification of ive genes responsible for the in vivo bacterial virulence, as done in the present study, demonstrates the usefulness of IVIAT for the detection of new virulence genes.

Animals↗

PubMed2003

Recently occurring adult tetanus in Korea: emphasis on immunization and awareness of tetanus.

Since a nationwide childhood vaccination with tetanus toxoid, tetanus has become a rare disease in Korea. However, we recently experienced 17 cases of adult tetanus in a university hospital during a 21-month period. Seventy percent of the patients were female, and the mean age was 63 yr (range, 29-87). The majority (88.2%) of the patients did not get primary vaccinations for tetanus and decennial tetanus-diphtheria toxoid booster. Most patients (88.2%), who sustained acute injury, did not seek medical care for their wounds or did not receive the prophylaxis for tetanus. Tetanus was found most frequently among farmers. Tetanus was diagnosed initially only in 53% of patients. The case-fatality ratio was 23.5%. These cases show that recently occurring tetanus in Korea is a disease, affecting the elderly and the female who may have a lower immunity against tetanus, and the farmers who are likely to be exposed to Clostridium tetani. In addition, diagnosis of tetanus is often delayed in area where cases are seen infrequently. Therefore, improved education among patients and physicians, emphasis of anti-tetanus immunization and awareness of tetanus respectively, may be essential for the prevention of disease and the reduction of its mortality.

Adult↗

PubMed2002

Proinflammatory cytokine profile in Vibrio vulnificus septicemic patients' sera.

Vibrio vulnificus causes a fulminant and frequently fatal septicemia in susceptible hosts. The present study was designed to evaluate the proinflammatory cytokine profile in V. vulnificus septicemia patients' sera and the effect of doxycycline therapy on the levels of proinflammatory cytokines. Levels of proinflammatory cytokines, tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta and IL-6, were measured in the sera of V. vulnificus septicemic patients and normal healthy volunteers using colorimetric sandwich ELISA. The mean values of TNF-alpha, IL-1beta and IL-6 in the sera of V. vulnificus patients (n=33) increased by 210-, 232- and 40-fold in comparison with those of normal healthy volunteers (n=5), but only the IL-6 level showed a statistically significant difference (P<0.05) between the two groups. Sera from the cases for which doxycycline treatment histories were obvious were designated 'before-treatment' (TX). All the others were included in the after-TX group. In the before-TX group (n=5), the levels of TNF-alpha and IL-1beta significantly increased (P<0.05) in comparison with the after-TX group (n=5). IL-6 levels in the two groups showed no difference. In conclusion, the levels of the well known proinflammatory cytokines TNF-alpha, IL-1beta and IL-6 increased in the V. vulnificus septicemic patients' sera, and the levels of TNF-alpha and IL-1beta decreased significantly after doxycycline treatment. These data indicate that proinflammatory cytokines might play a critical role in V. vulnificus septicemia like in other endotoxemic shocks. The use of doxycycline as an effective bactericidal agent and as an effective modulator of proinflammatory cytokines is supported.

Anti-Bacterial Agents↗

PubMed2002

Biofilm production by isolates of Candida species recovered from nonneutropenic patients: comparison of bloodstream isolates with isolates from other sources.

Biofilm production has been implicated as a potential virulence factor of some Candida species responsible for catheter-related fungemia in patients receiving parenteral nutrition. We therefore compared clinical bloodstream isolates representing seven different Candida species to each other and to those from other anatomical sites for the capacity to form biofilms in glucose-containing medium. Potential associations between the capacity to form biofilms and the clinical characteristics of fungemia were also analyzed. Isolates included the following from nonneutropenic patients: 101 bloodstream isolates (35 C. parapsilosis, 30 C. albicans, 18 C. tropicalis, 8 C. glabrata, and 10 other Candida species isolates) and 259 clinical isolates from other body sites (116 C. albicans, 53 C. glabrata, 43 C. tropicalis, 17 C. parapsilosis, and 30 other Candida species isolates). Organisms were grown in Sabouraud dextrose broth (SDB) containing a final concentration of 8% glucose to induce biofilm formation, as published previously. Biofilm production was determined by both visual and spectrophotometric methods. In this medium, biofilm production by C. albicans isolates was significantly less frequent (8%) than that by non-C. albicans Candida species (61%; P < 0.0001). The overall proportion of non-C. albicans Candida species isolates from the blood that produced biofilms was significantly higher than that of non-C. albicans Candida isolates obtained from other sites (79% versus 52%; P = 0.0001). Bloodstream isolates of C. parapsilosis alone were significantly more likely to be biofilm positive than were C. parapsilosis isolates from other sites (86% versus 47%; P = 0.0032). Non-C. albicans Candida species, including C. parapsilosis, were more likely to be biofilm positive if isolates were derived from patients whose candidemia was central venous catheter (CVC) related (95%; P < 0.0001) and was associated with the use of total parenteral nutrition (TPN) (94%; P < 0.005). These data suggest that the capacity of Candida species isolates to produce biofilms in vitro in glucose-containing SDB may be a reflection of the pathogenic potential of these isolates to cause CVC-related fungemia in patients receiving TPN.

Biofilms↗

PubMed2002

A case of maternal tetanus in Korea.

Tetanus is uncommon in Korea due to the introduction of vaccination programs and advances in public health. A case of maternal tetanus occurred on the 9 day postpartum in a 29-yr-old woman, who had not received a 10-yr-booster of tetanus-diphtheria toxoid after receiving the primary series of tetanus-toxoid-containing vaccine. There has hitherto been no reports on maternal tetanus in Korea. This case illustrates that tetanus remains a medical problem, principally among non- and under-immunized adults. The only way to fully prevent this disease is to ensure adequate immunization in all adults.

Adult↗