Hee Sun Sim

Atypical pathogens as etiologic agents in hospitalized patients with community-acquired pneumonia in Korea: a prospective multi-center study.

Local epidemiologic data on the etiologies of patients hospitalized with community-acquired pneumonia (CAP) is needed to develop guidelines for clinical practice. This study was conducted prospectively to determine the proportion of atypical bacterial pathogens in adults patients hospitalized with CAP in Korea between October 2001 and December 2002. Microbiological diagnosis was determined by serology for antibodies to Mycoplasma pneumoniae, Chlamydia pneumoniae, and Legionella pneumophila. Nucleic acid of M. pneumoniae and C. pneumoniae in respiratory samples and Legionella antigen in urine samples were detected. The study population consisted of 126 patients (71 males, 55 females), averaging 54.6 yr (SD±17.8), whose paired sera were available. An etiologic diagnosis for atypical pathogens was made in 18 patients (14.3%): C. pneumoniae 9 (7.1%), M. pneumoniae 8 (6.3%), and L. pneumophila 3 patients (2.4%). Streptococcus preumoniae and other typical pathogens were isolated from 36 patients (28.6%). Of 126 patients, 16 (12.7%) were admitted to intensive care unit and atypical pathogens were identified in 5 patients (31.3%). Initial clinical features of patients with pneumonia due to atypical, typical or undetermined pathogens were indistinguishable. We conclude that atypical pathogens should be seriously considered in hospitalized patients with CAP, when initiating empiric treatment in Korea.

Epidemiological and genetic analysis of a sustained community-wide outbreak of hepatitis A in the Republic of Korea, 2008: A hospital-based case–control study

BACKGROUND The epidemiological shift of hepatitis A has contributed to a sustained community-wide outbreak in Korea during 2008. OBJECTIVES To assess the risk factors associated with hepatitis A virus (HAV) propagation, and to analyze the circulating genotype in the sustained community-wide outbreak. STUDY DESIGN The hospital-based case-control study was conducted in an 850-bed university hospital in Seoul from April to August, 2008. For molecular analysis of HAV isolates, a 488-bp gene fragment of the VP1 region was amplified and sequenced. RESULTS In the multivariated logistic regression model, the risk factors of HAV infection adjusted by age were contacts with hepatitis A case (OR 3.98, 95% CI: 1.36-11.66), residence with child aged <or=5 years (OR 3.43, 95% CI: 1.32-8.87), consuming uncooked lettuce (OR 3.98, 95% CI: 1.83-8.68) or carrot (OR 2.38, 95% CI: 2.38-5.09), drinking tap water (OR 3.68, 95% CI: 1.62-8.37) or portable spring water (OR 2.71, 95% CI: 1.11-6.62) supplied by water purifiers, and eating out (OR 3.87, 95% CI: 1.53-9.78). All isolates analyzed belonged to genotype IIIA. There were 42 nucleotide differences in the sequenced VP1 region among the isolates. Amino acid sequences were identical with each other. CONCLUSIONS Our study suggests that sporadically contaminated food- or water-borne sources as well as person-to-person transmission might lead a sustained community-wide HAV outbreak and pre-existing dominant genotype IA might be replaced with genotype IIIA as a major epidemic strain in Korea. Our findings urge the health authority to make public guidelines for HAV vaccination and outbreak control.

Epidemiology and Control of an Outbreak of Vancomycin-Resistant Enterococci in the Intensive Care Units

Purpose This study was aimed to describe a vancomycin-resistant enterococci (VRE) outbreak across three intensive care units (ICUs) of a Korean hospital from September 2006 to January 2007 and the subsequent control strategies. Materials and Methods We simultaneously implemented multifaceted interventions to control the outbreak, including establishing a VRE cohort ward, active rectal surveillance cultures, daily extensive cleaning of environmental surfaces and environmental cultures, antibiotic restriction, and education of hospital staff. We measured weekly VRE prevalence and rectal acquisition rates and characterized the VRE isolates by polymerase chain reaction (PCR) of the vanA gene and Sma1-pulsed-field gel electrophoresis (PFGE). Results During the outbreak, a total of 50 patients infected with VRE were identified by clinical and surveillance cultures, and 46 had vancomycin-resistant Enterococcus faecium (VREF). PFGE analysis of VREF isolates from initial two months disclosed 6 types and clusters of two major types. The outbreak was terminated 5 months after implementation of the interventions: The weekly prevalence rate decreased from 9.1/100 patients-day in September 2006 to 0.6/100 by the end of January 2007, and the rectal acquisition rates also dropped from 6.9/100 to 0/100 patients-day. Conclusion Our study suggests that an aggressive multifaceted control strategy is a rapid, effective approach for controlling a VRE outbreak.

Comparative analysis of disease severity between genotypes IA and IIIA of hepatitis A virus

Although hepatitis A is a major health problem worldwide, it has not yet been clarified whether or not viral factors affect the clinical characteristics. This study aimed to investigate if a genotype of hepatitis A virus (HAV) affects disease severity among adolescent and adult populations. Clinical data and specimens were collected from patients ≥16‐years‐of‐age with acute hepatitis A at two university hospitals in Korea during the two study periods: 1998 and 1999 (n = 45), and 2009 (n = 66). Nucleotide sequencing of the complete VP1 region of the HAV isolates was performed for phylogenetic analysis and genotyping. Clinical parameters related to disease severity were compared by HAV genotype to determine its clinical relevance. Of the 87 patients, 47 were male and the mean age was 29.8 ± 8.1 years. The genotype IIIA (93.0%, 53/57) was predominant in the year 2009, whereas IA (93.3%, 28/30) was the major genotype in 1998 and 1999. When comparing disease severity between the two HAV genotypes, the patients with genotype IIIA were older and had higher alanine aminotransferase (ALT) levels, prolonged prothrombin times and lower serum albumin levels. In a multivariate logistic regression model, higher ALT levels ≥ 1,000 IU/L (odds ratio [OR] 11.7, 95% confidence interval [CI] 2.5–54.0) and longer hospitalization (OR 22.49, 95%CI 4.6–132.5) were associated independently with genotype IIIA. In conclusion, this study indicates that HAV genotype might be one of the viral factors responsible for the disease severity of hepatitis A. J. Med. Virol. 83:1308–1314, 2011.

Epidemiological and Genetic Characterization of Methicillin-Resistant Staphylococcus aureus Isolates from the Ear Discharge of Outpatients with Chronic Otitis Media

The origin of methicillin-resistant Staphylococcus aureus (MRSA) strains from otolaryngology outpatients has not been evaluated yet in Korea. We analyzed epidemiologic and genetic characteristics of MRSA isolates from the ear discharge of 64 outpatients with chronic otitis media in a Korean University Hospital during 2004. MRSA strains were grouped as either from the initial visit (n=33) or the follow-up visit (n=31) based on the timing of isolation. Healthcare-associated risk factors were frequently present among patients of the initial visit group, especially prior visit to primary clinic (79%) and antibiotic use (73%). SCCmec typing and multilocus sequence typing results showed that two genotypes, ST5-MRSA-II and ST239-MRSA-III, were prevalent in both the initial visit (73% vs. 24%) and the follow-up visit (55% vs. 42%). Pulsed-field gel electrophoresis identified eight types, including two major types shared by both groups. We conclude that majority of MRSA strains from ear discharge of chronic otitis media belonged to nosocomial clones that might be circulating in the community. This is the first report of the genetic analysis of MRSA strains from otolaryngology practices in Korea.

Molecular analysis of a prolonged spread of Klebsiella pneumoniae co-producing DHA-1 and SHV-12 β-lactamases

The study investigated molecular mechanisms for prolonged nosocomial spread of multidrug-resistant Klebsiella pneumoniae co-producing plasmid-mediated AmpC β-lactamase DHA-1 and extended-spectrum β-lactamase SHV-12. Forty-eight clinical isolates of K. pneumonia, resistant to the extended-spectrum cepha-losporins, were collected in a 750-bed university hospital over a year. The isolates were characterized for PCR-based β-lactamase genotypes, isoelectric focusing and pulsed-field gel electrophoresis (PFGE) profiles. Resistance transfer was performed by plasmid conjugation and confirmed by a duplex-PCR and Southern hybridization. On β-lactamase typing, the strains producing only the DHA-1 enzyme (n=17) or co-producing DHA-1 and SHV-12 enzymes (n=15) were predominant. Judging from a one year-distribution of PFGE profiles, the co-producer was spread primarily with single clonal expansion of the PFGE-type A with subtypes (n=14), whereas the strains producing only DHA-1 enzyme were spread simultaneously with the PFGE-type A (n=ll) and other PFGE types (n=6). Transconjugants of the co-producers were confirmed to harbor either both blaDHA-1 and blaSHV-12 or only the blaDHA-1. In conclusion, this study indicated that the persistent nosocomial spread of multidrug-resistant K. pneumoniae strains was primarily associated with expansion of a clone harboring both the blaDHA-1 and blaSHV-12 or the blaDHA-1 only, and to a lesser extent with the horizontal transfer of the resistant plasmids. Our observations have clinical implication for the control and prevention of nosocomial dissemination of multidrug-resistant K. pneumoniae strains.

Clinical Characterization of Hepatitis A Infection Complicated with Acute Kidney Injury and Sequence Analysis of the VP1 Region

was independently associated with AKI occurrence in non-fulminant HAV infections (odds ratios=1.094, 95% confidence interval=1.011−1.183). HAV RNA was detected in 57 (86.4%) patients: 53 strains (93.0%) showed genotype IIIA and 4 strains pre- sented genotype IA. All HAV isolates from the AKI patients belonged to the genotype IIIA and shared the identical sequences with those from the non-AKI patients. Conclusion: This study indicates that higher level of C-reactive protein is associated with AKI occurrence in non-fulminant HAV infections. There were no spe- cific nucleotide or amino acid substitutions in the VP1 region associated with AKI occurrence. (Korean J Clin Microbiol 2010;13:7-13)