Jung Oak Kang

First report from the Asian Rotavirus Surveillance Network.

Rotavirus remains the most common cause of severe, dehydrating diarrhea among children worldwide. Several rotavirus vaccines are under development. Decisions about new vaccine introduction will require reliable data on disease impact. The Asian Rotavirus Surveillance Network, begun in 2000 to facilitate collection of these data, is a regional collaboration of 36 hospitals in nine countries or areas that conduct surveillance for rotavirus hospitalizations using a uniform World Health Organization protocol. We summarize the Networks organization and experience from August 2001 through July 2002. During this period, 45% of acute diarrheal hospitalizations among children 0–5 years were attributable to rotavirus, higher than previous estimates. Rotavirus was detected in all sites year-round. This network is a novel, regional approach to surveillance for vaccine-preventable diseases. Such a network should provide increased visibility and advocacy, enable more efficient data collection, facilitate training, and serve as the paradigm for rotavirus surveillance activities in other regions.

Further Increases in Carbapenem-, Amikacin-, and Fluoroquinolone-Resistant Isolates of Acinetobacter spp. and P. aeruginosa in Korea: KONSAR Study 2009

Purpose The increasing prevalence of antimicrobial resistant bacteria has become a serious worldwide problem. The aim of this study was to analyze antimicrobial resistance data generated in 2009 by hospitals and commercial laboratories participating in the Korean Nationwide Surveillance of Antimicrobial Resistance program. Materials and Methods Susceptibility data were collected from 24 hospitals and two commercial laboratories. In the analysis, resistance did not include intermediate susceptibility. Duplicate isolates were excluded from the analysis of hospital isolates, but not from the commercial laboratory isolates. Results Among the hospital isolates, methicillin-resistant Staphylococcus aureus, penicillin G-non-susceptible Streptococcus pneumoniae based on meningitis breakpoint, and ampicillin-resistant Enterococcus faecium remained highly prevalent. The proportion of vancomycin-resistant E. faecium gradually increased to 29%. Ceftazidime-resistant Escherichia coli and Klebsiella pneumoniae increased to 17% and 33%, respectively, and fluoroquinolone-resistant K. pneumoniae, Acinetobacter spp. and Pseudomonas aeruginosa increased to 33%, 67% and 39%, respectively. Amikacin-resistant Acinetobacter spp. increased to 48%. Imipenem-resistant Acinetobacter spp. and P. aeruginosa increased to 51% and 26%, respectively. Higher resistance rates were observed in intensive care unit (ICU) isolates than in non-ICU isolates among the isolates from hospitals. Resistance rates were higher in hospital isolates than in clinic isolates among the isolates from commercial laboratories. Conclusion Among the hospital isolates, ceftazidime-resistant K. pneumoniae and fluoroquinolone-resistant K. pneumoniae, Acinetobacter spp., and P. aeruginosa further increased. The increase in imipenem resistance was slight in P. aeruginosa, but drastic in Acinetobacter spp. The problematic antimicrobial-organism combinations were much more prevalent among ICU isolates.

Molecular Epidemiological Profile of Rotavirus in South Korea, July 2002 through June 2003: Emergence of G4P[6] and G9P[8] Strains

To determine the distribution of rotavirus strain genotypes in South Korea, rotavirus-positive stool specimens were collected from July 2002 through June 2003 at 8 hospitals in the Korean Rotavirus Strain Surveillance Network, and they were genotyped by means of reverse-transcription polymerase chain reaction. The globally uncommon G4P[6] type was the most prevalent type identified among strains (27% of strains), the newly emerging G9P[8] strain accounted for 11% of strains, and the globally common genotypes (i.e., G1P[8], G2P[4], G3P[8], and G4P[8]) constituted 55% of the strains characterized. Ninety percent of G4P[6] strains were detected in specimens obtained from neonates. Common genotypes were responsible for the rotavirus epidemic that began in January 2003 and ended in May 2003; however, an early peak in infections with the G4P[6] strain occurred from August through October 2002, and infections with this strain were detected throughout the remaining study period. G4P[6] strains were most commonly identified at 6 urban health care centers, but they were absent from 2 rural health care centers. The newly emerging strain G9P[8] represented a relatively greater proportion of strains identified at a hospital in the central region of Korea and at 2 hospitals in the southern region. The identification of novel rotavirus genotypes in this laboratory-based surveillance study underscores the importance to public health of continued strain surveillance among children for whom prevention of rotavirus infection by vaccination might be considered.

Multicentre study of the prevalence of toxigenic Clostridium difficile in Korea: results of a retrospective study 2000-2005.

The prevalence of toxigenic Clostridium difficile in Korea has been reported to be approximately 60-80%. Although the prevalence of the tcdA(-)tcdB(+) C. difficile strain was less then 5% prior to the year 2000, it has become an emerging nosocomial pathogen in Korea. Therefore, we have attempted to determine the multicentre nationwide prevalence of tcdA(+)tcdB(+) and tcdA(-)tcdB(+) C. difficile for epidemiological purposes. C. difficile strains (n=724, 30 from 2000, 80 from 2001, 74 from 2002, 76 from 2003, 179 from 2004, 285 from 2005) were obtained retrospectively from January 2000 to December 2005 from in-patients at 6 hospitals, all of whom were suspected of having C. difficile-associated disease (CDAD), colitis or pseudomembranous colitis. The numbers of participating hospitals varied yearly (1 in 2000, 2 in 2001-2003, 3 in 2004, 5 in 2005). The hospitals were located in Seoul (n=4), Kyunggi Province (n=1) and Busan (n=1), Korea. PCR assays for tcdA and tcdB genes were conducted using 724 unduplicated C. difficile isolates. The mean prevalence of tcdA(+)tcdB(+) and tcdA(-)tcdB(+) C. difficile strains over the 6 years was 51.8 % (38.4-59.3%) and 25.8%(10-56.0%), respectively. The mean prevalence of tcdA(-)tcdB(+) C. difficile strains was less than 7% until 2002, but began to increase in 2003 (13.2%) and achieved a peak in 2004 (50.3%). In 2005, the mean prevalence of tcdA(+)tcdB(+) and tcdA(-)tcdB(+) C. difficile strains was 47.7% (30.9-60.3%) and 27.0% (17.6-54.8%), respectively. This nationwide epidemiological study showed that tcdA(-)tcdB(+) C. difficile strains have already spread extensively throughout Korea, and our results provide basic data regarding the controversies currently surrounding the toxigenicity of tcdA(-)tcdB(+) C. difficile. The use of enzyme immunoassays capable of detecting both TcdA and TcdB is strongly recommended for the diagnosis of CDAD in microbiology laboratories, in order to control the spread of the tcdA(-)tcdB(+) strains of C. difficile.

Bacteriologic Comparison of Tonsil Core in Recurrent Tonsillitis and Tonsillar Hypertrophy

Objectives: Although many bacteriology studies on tonsillar diseases have been completed, all have been confined to children and were characterized by a paucity of cases. The purpose of this study was to analyze the underlying bacterial pathogens in tonsillar disease.

Changing pattern of antimicrobial resistance of Helicobacter pylori in Korean patients with peptic ulcer diseases

Background. Antibiotic resistance of Helicobacter pylori is problematic because it reduces the efficacy of eradication therapy. It has been suggested that the incidence of resistance is rising. In Korea, information on the antimicrobial resistance of H. pylori is rare. The aim of this study was to assess the prevalence of H. pylori antibiotic resistance at a single center in Korea, and the changes in its antimicrobial resistance, and to detect the mutation foci of clarithromycin-resistant strains. Methods. H. pylori isolates obtained from 224 patients with peptic ulcer disease in Korea between June 1996 and March 2000 were tested for antimicrobial resistance. The minimum inhibitory concentration (MIC) for metronidazole and clarithromycin was determined by the broth microdilution method. Isolates were considered resistant when the MIC was more than 8 μg/ml for metronidazole and more than 1 μg/ml for clarithromycin. To detect H. pylori 23S rRNA mutations, polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was performed. Sequencing was performed on the two strands of the nonrestricted amplicons. Results. Overall, resistance to metronidazole and clarithromycin was detected in 41.9% and 5.4% of patients, respectively. There was no significant difference in metronidazole and clarithromycin resistance according to age group and sex. Six strains were resistant to both metronidazole and clarithromycin. Six of nine clarithromycin-resistant isolates possessed the A2144G mutation in the gene encoding 23S rRNA. Sequencing of the three non-restricted clarithromycin-resistant strains revealed a T-to-C mutation at position 2182. Conclusions. In Korea, there was no significant increase in the prevalence of metronidazole resistance, but clarithromycin-resistant H. pylori strains had increased relatively over the 5-year period. There was an increasing tendency for the emergence of strains with dual resistance to metronidazole and clarithromycin. Many of the clarithromycin-resistant strains possessed the A2144G mutation.

Epidemiology of Clostridium difficile infections in a tertiary-care hospital in Korea.

To survey healthcare-associated Clostridium difficile infection (HA-CDI) in a 900-bed tertiary-care hospital, we prospectively investigated the epidemiology of CDI and distribution of PCR-ribotypes. From February 2009 through January 2010, all patients with HA-CDI were enrolled. Epidemiological information and prescription records for antibiotics were collected. The C. difficile isolates were characterized using reference strains and were tested for antibiotic susceptibility. During the survey, incidence of HA-CDI was 71.6 per 100 000 patient-days. In total, 140 C. difficile isolates were obtained from 166 patients with HA-CDI. The PCR-ribotyping yielded 38 distinct ribotypes. The three most frequently found ribotypes made up 56.4% of all isolates; they comprised 37 isolates (26.4%) of PCR-ribotype 018, 22 (15.7%) of toxin A-negative PCR-ribotype 017, and 20 (14.3%) of PCR-ribotype 001. Clostridium difficile PCR-ribotype 018 was present in all departments throughout the hospital during the 11 months, whereas ribotype 017 and ribotype 001 appeared mostly in the pulmonary department. Hypervirulent C. difficile PCR-ribotype 027 was detected in 1 month on two wards. The incidence of CDI in each department showed a seven-fold difference, which correlated significantly with the amount of prescribed clindamycin (R = 0.783, p 0.013) or moxifloxacin (R = 0.733, p 0.025) in the departments. The rates of resistance of the three commonest ribotypes to clindamycin and moxifloxacin were significantly higher than those of other strains (92.1% versus 38.2% and 89.5% versus 27.3%, respectively). CDI is an important nosocomially acquired infection and this study emphasizes the importance of implementing country-wide surveillance to detect and control CDI in Korea.

Interleukin-6, interleukin-8, interleukin-11, and interferon-γ levels in nasopharyngeal aspirates from wheezing children with respiratory syncytial virus or influenza A virus infection

The differences between respiratory syncytial virus (RSV) and influenza A virus (IFAV) in the pathogenesis of wheezing in young children have not been clearly defined. The aim of this study was to assess the contributions of RSV vs IFAV in the pathogenesis of upper airway inflammation in wheezy young children. We compared interleukin (IL)‐6, IL‐8, IL‐11, and interferon‐γ (IFN‐γ) levels in nasopharyngeal aspirates (NPA) from non‐asthmatic children with respiratory virus infections (RSV in 17 children and IFAV in 13 children), asthmatic children with viral infections (RSV in nine children, IFAV in 10 children), and 22 unaffected healthy children (controls). Levels of IL‐11 in NPA from asthmatic children were significantly higher than those from non‐asthmatic children with RSV infection, and RSV infection enhanced the IL‐11 production in NPA significantly compared to IFAV infection. Nasopharyngeal epithelium from children with RSV infection secreted more IL‐6 than that of children with IFAV infection. There was little difference in the IL‐8 and IFN‐γ levels between asthmatic and non‐asthmatic children with RSV or IFAV infection. In conclusion, asthma enhanced IL‐11 production in RSV infection rather than IFAV infection in early childhood. There was a trend towards greater IL‐6 production in RSV infection compared with IFAV infection.

Epidemiology and clinical characteristics of Clostridium difficile infection in a Korean tertiary hospital.

In order to investigate the incidence, clinical and microbiologic characteristics of Clostridium difficile infection (CDI) in Korea, a prospective observational study was performed. From September 2008 through January 2010, all patients whose stool was tested for toxin assay A&B and/or C. difficile culture were studied for clinical characteristics. Toxin types of the isolates from stool were tested. The mean incidence of CDI per 100,000 patient-days was 71.6 by month (range, 52.5-114.0), and the ratio of CDI to antibiotic-associated diarrhea was 0.23. Among 200 CDI patients, 37.5% (75/200) was severe CDI based on severity score. Clinical outcome of 189 CDI was as followed; 25.9% (49/189) improved without treatment, 84.3% (118/140) achieved clinical cure and attributed mortality was 0.7% (1/140) with the treatment. Recurrence rate was 21.4% (30/140) and cure without recurrence was 66.4% (93/140). The most common type of toxin was toxin A-positive/toxin B-positive strain (77.5%), toxin A-negative/toxin B-positive strains or binary toxin-producing strains comprised 15.4% or 7.1%, respectively. In conclusion, the incidence of CDI in Korea is a little higher than other reports during the non-epidemic setting. We expect that the change of epidemiology and clinical severity in CDI can be evaluated based on these results.

Metallo-β-Lactamase-Producing Pseudomonas spp. in Korea: High Prevalence of Isolates with VIM-2 Type and Emergence of Isolates with IMP-1 Type

Purpose Two Korean nationwide studies showed that metallo-β-lactamases (MBLs)-producing-Pseudomonas spp. are not rare. The aim of this study was to assess the trends of MBL-producing isolates among imipenem-resistant isolates of Pseudomonas spp. Materials and Methods Imipenem-resistant clinical isolates were collected from 23 hospitals and one commercial laboratory participating in the KONSAR program in 2005. Polymerase chain reaction (PCR) was used to detect MBL genes. Results Alleles of MBL genes were detected in 10.8% of 415 Pseudomonas aeruginosa and 66.7% of 12 P. putida isolates from 18 of 24 hospitals/laboratory. Among the 14 IMP-1-like and 39 VIM-2-like MBLs, emergence of IMP-6 was detected for the first time. Conclusion Prevalence of MBL-producing P. aeruginosa has not significantly increased, but IMP-6 emerged in P. aeruginosa.