Byung Wook Eun

The Association of Newly Identified Respiratory Viruses with Lower Respiratory Tract Infections in Korean Children, 2000-2005

Abstract Background. This study was performed to evaluate the associations of newly recognized viruses, namely, human metapneumovirus (hMPV), human coronavirus (HCoV)–NL63, and human bocavirus (HBoV) with lower respiratory tract infections (LRTIs) in previously healthy children. Methods. To determine the prevalences of 11 viruses—respiratory syncytial virus (RSV), adenovirus, rhinovirus, parainfluenza viruses (PIVs) 1 and 3, influenza viruses A and B, hMPV, HCoV, HCoV-NL63, and HBoV—among infants or children with LRTIs, in association with their epidemiologic characteristics, we performed multiplex reverse-transcriptase polymerase chain reaction on nasopharyngeal aspirates obtained from 515 children 5 years old with LRTIs during the period 2000–2005. Results. Viruses were identified in 312 (60.6%) of the 515 patients. RSV was detected in 122 (23.7%), HBoV in 58 (11.3%), adenovirus in 35 (6.8%), PIV-3 in 32 (6.2%), rhinovirus in 30 (5.8%), hMPV in 24 (4.7%), influenza A in 24 (4.7%), PIV-1 in 9 (1.7%), influenza B in 9 (1.7%), and HCoV-NL63 in 8 (1.6%). Coinfections with 2 viruses were observed in 36 patients (11.5%). Twenty-two patients (37.9%) infected with HBoV had a coinfection. Bronchiolitis was frequently diagnosed in patients who tested positive for RSV, PIV-3, or rhinovirus, whereas influenza A, PIV-1, and HCoV-NL63 were commonly found in patients with croup. The age distributions of patients with viral infections differed; notably, RSV was responsible for 77% of LRTIs that occurred in infants 3 months old. The number of hMPV infections peaked between February and April, whereas the number of HCoV-NL63 infections peaked between April and May. Conclusions. This study describes the features of LRTIs associated with newly identified viruses in children, compared with those associated with known viruses. Additional investigations are required to define the role of HBoV in LRTI.

Streptococcus pneumoniae serotype 19A in children, South Korea.

A single, multidrug-resistant strain was responsible for increased incidence of this serotype before introduction of the pneumococcal 7-valent conjugate vaccine.

Mycoplasma pneumoniae in Korean children: the epidemiology of pneumonia over an 18-year period

OBJECTIVES Mycoplasma pneumoniae (MP) is a major cause of community-acquired pneumonia in children. The aim of this study was to investigate the long-term epidemiology of MP pneumonia in Korean children. METHODS A retrospective analysis of a database of 2405 patients with pneumonia at the Seoul National University Childrens Hospital between 1986 and 2004 was performed. Serologic diagnosis for MP infection was made based on a 4-fold rise or single titers >/=1:640, which were measured by an indirect agglutination test. RESULTS MP pneumonia was diagnosed in 568 patients over 18 years. The mean age was 5.7 years. Children younger than 5 years of age accounted for 44% of the cases. Six outbreaks were observed at intervals of 3-4 years. The earlier epidemics up until 1996 peaked in the summer, while the later epidemics peaked in the fall or early winter. Children <5 years old were more commonly affected during large epidemics compared to endemic periods. The geometric mean antibody titers were maintained >/=1:320 up to 7 months after the onset of illness. CONCLUSIONS The results of this study revealed community outbreaks of MP pneumonia at 3-4-year intervals among Korean children. A significant proportion of young Korean children were affected by MP pneumonia, especially during large epidemics.

Comparison of polymerase chain reaction and the indirect particle agglutination antibody test for the diagnosis of Mycoplasma pneumoniae pneumonia in children during two outbreaks.

Background: Diagnosis of Mycoplasma pneumoniae pneumonia is challenging because of the lack of standardized rapid tests. Many serologic tests and polymerase chain reaction (PCR) based methods are used with different diagnostic criteria. Methods: This retrospective study was conducted to compare the diagnostic values of the indirect particle agglutination test and nested PCR of nasopharyngeal aspirates for the diagnosis of M. pneumoniae pneumonia in children. These assays were evaluated in 234 hospitalized children with community-acquired lower respiratory tract infections during 2 outbreaks of M. pneumoniae pneumonia in 2000 and 2003. Results: The cumulative PCR positive rate was 26.7% in patients with maximum antibody titers of ≤1:320 and 78.2% in those with titers of ≥1:640. Based on these data, a positive PCR, a 4-fold increase in antibody titer, or a single titer ≥1:640 were considered to indicate acute M. pneumoniae infection. Overall, 152 children were diagnosed to have M. pneumoniae pneumonia; 27 (18%) by serology only, 26 (17%) by PCR only, and 99 (65%) by both methods. Children who were diagnosed by PCR only were significantly younger (P = 0.003) and were more often immunocompromised (P = 0.019) than those that were PCR negative. Duration of cough before PCR diagnosis was shorter in cases diagnosed by PCR only than those that were PCR negative (P = 0.045). Conclusions: In conclusion, during the 2 outbreaks of M. pneumoniae infection, we found that the PCR test may be useful for the rapid diagnosis of M. pneumoniae pneumonia, particularly in young children and in immunocompromised patients and in early stage disease.

Diagnosis of pneumococcal pneumonia: Current pitfalls and the way forward

Streptococcus pneumoniae is the most common cause of community-acquired pneumonia. However, it can also asymptomatically colonize the upper respiratory tract. Because of the need to distinguish between S. pneumoniae that is simply colonizing the upper respiratory tract and S. pneumoniae that is causing pneumonia, accurate diagnosis of pneumococcal pneumonia is a challenging issue that still needs to be solved. Sputum Gram stains and culture are the first diagnostic step for identifying pneumococcal pneumonia and provide information on antibiotic susceptibility. However, these conventional methods are relatively slow and insensitive and show limited specificity. In the past decade, new diagnostic tools have been developed, particularly antigen (teichoic acid and capsular polysaccharides) and nucleic acid (ply, lytA, and Spn9802) detection assays. Use of the pneumococcal antigen detection methods along with biomarkers (C-reactive protein and procalcitonin) may enhance the specificity of diagnosis for pneumococcal pneumonia. This article provides an overview of current methods of diagnosing pneumococcal pneumonia and discusses new and future test methods that may provide the way forward for improving its diagnosis.

Prevalence and genetic structures of Streptococcus pneumoniae serotype 6D, South Korea

To determine prevalence and genetic structures of new serotype 6D strains of pneumococci, we examined isolates from diverse clinical specimens in South Korea during 1991–2008. Fourteen serotype 6D strains accounted for 10.4% of serogroup 6 pneumococci from blood, sputum, nasopharynx, and throat samples. Serotype 6D strains consisted of 3 sequence types.

Role of human coronavirus NL63 in hospitalized children with croup.

Background: Human coronavirus NL63 (HCoV-NL63) has recently been implicated as a common cause of croup in children. This study was performed to evaluate viruses associated with croup in children, with an emphasis on HCoV-NL63. Methods: Nasopharyngeal aspirates were prospectively collected from 182 children hospitalized with croup at Seoul National University Bundang Hospital from January 2005 to June 2009. Multiplex reverse-transcriptase polymerase chain reaction was conducted for detection of 11 respiratory viruses, and medical records were reviewed. Results: Viruses were identified in 147 (80.8%) of the 182 croup patients. The 3 most commonly detected viruses were parainfluenza virus type 1 (PIV1) in 44 (24.2%) patients, HCoV-NL63 in 30 (16.5%) patients, and influenza A virus in 25 (13.7%) patients. Other detected viruses were rhinovirus in 22 (12.1%) patients, PIV type 3 and respiratory syncytial virus in 15 (8.2%) patients, human bocavirus in 8 (4.4%) patients, and several others in a few patients. Coinfections with ≥2 viruses were found in 20 (11%) patients. HCoV-NL63 was identified primarily in winter, which coincides with the peak occurrence of croup. Patients with HCoV-NL63 infection were younger than those who were positive for PIV1 (median age 13 months versus 21 months, P = 0.006) and had shorter fever duration than influenza A virus infection (median 1.5 days versus 4 days, P = 0.000). Conclusions: PIV1 and HCoV-NL63 were most commonly associated with patients who were hospitalized with croup. HCoV-NL63 is prevalent in winter and is associated with younger age and with shorter fever duration.

BCG osteomyelitis caused by the BCG Tokyo strain and confirmed by molecular method

Bacille Calmette-Guérin (BCG) osteitis is a rare complication of BCG vaccination. We describe two cases of BCG osteomyelitis developed in Korean infants who were given multipuncture BCG vaccination. The cultures of bone curettage specimens grew mycobacteria. The isolates were identified as BCG Tokyo strains by the deletion of the region of difference 1 (RD1) and characterization of RD8 and RD14 using the multiplex polymerase chain reaction.

Serotype distribution and antibiotic resistance of Streptococcus pneumoniae isolated from invasive infections after optional use of the 7-valent conjugate vaccine in Korea, 2006-2010

This study examined the serotype distribution and antimicrobial resistance of pneumococcal isolates from invasive infections in children between 2006 and 2010, when the 7-valent pneumococcal conjugate vaccine (PCV7) was offered as an optional vaccine in Korea. Among 140 isolates collected from 8 centers, the common serotypes were 19A (22.9%), 19 F (12.1%), and 6B (8.6%). Between 2006 and 2010, PCV7 serotypes decreased from 62.5% to 21.4% (P = 0.002), whereas three 13-valent pneumococcal conjugate vaccine (PCV13)-specific serotypes (3, 6A, and 19A) increased from 18.8% to 42.9% (P = 0.016). Among 102 multidrug-resistant isolates, the proportion of PCV7 serotypes decreased from 65.2% to 21.7% (P = 0.001), and 3 PCV13-specific serotypes increased from 17.4% to 47.8% (P = 0.008). Optional PCV7 vaccination has influenced the proportion of PCV7 serotypes in Korea, resulting in a decrease, whereas the proportions of 3 PCV13-specific serotypes, particularly 19A, have increased.

Trends in the incidence rate of device-associated infections in intensive care units after the establishment of the Korean Nosocomial Infections Surveillance System

BACKGROUND The effectiveness of continuous nationwide surveillance on healthcare-associated infections should be investigated in each country. AIM To assess the rate of device-associated infections (DAIs) in intensive care units (ICUs) since the establishment of the Korean Nosocomial Infections Surveillance System (KONIS). METHODS Nationwide data were obtained on the incidence rate of DAI in ICUs reported to KONIS by all participating hospitals. The three major DAIs were studied: ventilator-associated pneumonia (VAP), central line-associated bloodstream infection (CABSI), and catheter-associated urinary tract infection (CAUTI). The pooled and year-wise incidence rates (cases per 1000 device-days) of these DAIs were determined for the period 2006 and 2012. In addition, data from institutions that had participated in KONIS for at least three consecutive years were analysed separately. FINDINGS The number of ICUs participating in KONIS gradually increased from 76 in 2006 to 162 in 2012. Between 2006 and 2012, the incidence rate per 1000 device-days for VAP decreased significantly from 3.48 to 1.64 (F = 11, P < 0.01), for CAUTI the rate decreased non-significantly from 1.85 to 1.26 (F = 2.02, P = 0.07), and for CABSI the rate also decreased non-significantly from 3.4 to 2.57 (F = 1.73, P = 0.12). In the 132 ICUs that had participated in KONIS for at least three consecutive years, the VAP rate significantly decreased from the first year to third year (F = 20.57, P < 0.01), but the rates of CAUTI (F = 1.06, P = 0.35) and CABSI (F = 1.39, P = 0.25) did not change significantly. CONCLUSION The decreased incidence rate of VAP in ICUs in Korea might be associated with the continuous prospective surveillance provided by KONIS.