Ki Wook Yun

Enteroviral meningitis without pleocytosis in children

Objectives This study aims to describe the clinical characteristics of enteroviral meningitis in association with the absence of cerebrospinal fluid (CSF) pleocytosis. Design This was a retrospective analysis of databases of patients diagnosed with enteroviral meningitis by CSF reverse transcription-PCR testing. Presence of CSF non-pleocytosis at each age group was analysed by use of the two criteria. Clinical variables were compared with regard to the presence of CSF pleocytosis. Multiple logistic regression analysis was used to identify factors that were associated with CSF pleocytosis. Setting Two hospitals in South Korea, between January 2008 and August 2011. Patients 390 infants and children with enteroviral meningitis. Interventions None. Main outcome measures Proportion of enteroviral meningitis without CSF pleocytosis. Results Among the 390 patients with enteroviral meningitis, 16–18% did not have CSF pleocytosis. In particular, CSF pleocytosis was not present in 68–77% of the neonates with enteroviral meningitis, demonstrating that the proportion of CSF pleocytosis decreased significantly with age (p<0.001). In multivariate models, younger age (adjusted OR 0.981; 95% CI 0.973 to 0.989), lower peripheral white blood cell count (adjusted OR 0.843; 95% CI 0.791 to 0.899), and shorter interval between onset and lumbar puncture (adjusted OR 0.527; 95% CI 0.315 to 0.882) were associated with the absence of CSF pleocytosis in enteroviral meningitis. Conclusions This study demonstrated high proportion of non-pleocytic enteroviral meningitis in young infants and identified several clinical factors that contributed to the absence of CSF pleocytosis. We suggest that CSF enterovirus PCR testing is likely to detect more cases of enteroviral meningitis, especially in young infants.

Streptococcus pneumoniae Type Determination by Multiplex Polymerase Chain Reaction

The purpose of this study was to develop pneumococcal typing by multiplex PCR and compare it with conventional serotyping by quellung reaction. Pneumococcal strains used in this study included 77 isolates from clinical specimens collected from children at Seoul National University Childrens Hospital from 2006 to 2010. These strains were selected as they represented 26 different serotypes previously determined by quellung reaction. Molecular type was determined by 8 sequential multiplex PCR assays. Bacterial DNA extracted from cultured colonies was used as a template for PCR, and primers used in this study were based on cps operon sequences. Types 6A, 6B, 6C, and 6D were assigned based on the presence of wciNβ and/or wciP genes in 2 simplex PCRs and sequencing. All 77 isolates were successfully typed by multiplex PCR assays. Determined types were as follows: 1, 3, 4, 5, 6A, 6B, 6C, 6D, 7C, 7F, 9V, 10A, 11A, 12F, 13, 14, 15A, 15B/15C, 19A, 19F, 20, 22F, 23A, 23F, 34, 35B, and 37. The results according to the PCR assays were in complete concordance with those determined by conventional quellung reaction. The multiplex PCR assay is highly reliable and potentially reduces reliance upon conventional serotyping.

Proteinuria in a Boy with Infectious Mononucleosis, C1q Nephropathy, and Dent's Disease

C1q nephropathy is a proliferative glomerulopathy with extensive mesangial deposition of C1q. A three-year old boy presented with a nephrotic-range proteinuria during an acute phase of Epstein-Barr virus (EBV) infection, and he had a family history of Dents disease. The renal biopsy findings were compatible with C1q nephropathy. However, EBV in situ hybridization was negative. The CLCN5 gene analysis revealed an R637X hemizygous mutation, which was the same as that detected in his maternal cousin, the proband of the family. The causal relationship between EBV infection and C1q nephropathy remains to be determined. Moreover, the effects of underlying Dents disease in the process of C1q nephropathy has to be considered.

Genotype Characterization of Group B Streptococcus Isolated from Infants with Invasive Diseases in South Korea

Background: Group B streptococcus (GBS) is one of the leading causes of invasive infections in infants. This study aimed to investigate the genotypic diversity of GBS causing invasive infections in infants and to observe the prevalence of the highly virulent clone in South Korea. Methods: Invasive strains of GBS were collected prospectively from infants admitted at 4 hospitals during 1995–2015. Serotype and multilocus sequence typing were determined. All isolates underwent polymerase chain reaction amplification to detect the presence of the hypervirulent GBS adhesin (hvgA) gene. Antibiotic susceptibility testing was done by E-test, and erythromycin resistance genes were detected using polymerase chain reaction amplification. Results: Among 98 GBS isolates collected, 14 sequence types (STs) were found; ST1 (20.4%), ST17 (19.4%) and ST19 (18.4%) were the most prevalent. The dominant serotype capsule expressed by ST1 was serotype V, ST17 and ST19 were all serotype III and ST23 was serotype Ia. hvgA gene was detected in 19.4% (n = 19) of the isolates; all were ST17, serotype III. A significant temporal trend of serotype III isolates was observed; as ST17 increased (P = 0.001) in proportion, ST19 decreased (P = 0.009). Erythromycin resistance was found in 42.9% (42/98); dominant strains were ermB-positive ST1 serotype V (n = 18/20, 90%), ermB-positive ST17 serotype III (n = 10/19, 52.6%) and ermA-positive ST335 serotype III (n = 7/7, 100%). Conclusions: The predominant STs causing invasive infections in South Korea were ST1, ST19 and ST17. Among serotype III isolates, an increase in proportion of the hypervirulent ST17 strains was observed. Erythromycin resistance was significantly associated with ST1.

Antimicrobial therapy of macrolide-resistant Mycoplasma pneumoniae pneumonia in children

ABSTRACT Introduction: Mycoplasma pneumoniae is an important cause of community-acquired pneumonia in children and young adolescents. Macrolides are recommended as the first-line therapy however, macrolide resistance rates in M. pneumoniae among children have been increasing substantially. Areas covered: This review focused on clinical characteristics and treatment of macrolide-resistant M. pneumoniae pneumonia in children. Expert commentary: Antibiotic choice should be based on in vitro activity, clinical efficacy and in consideration of potential adverse events. Macrolide resistance did not contribute to the clinical severity of M. pneumoniae pneumonia, but resistance may be an aggravating factor. Antibiotics may not be required for treatment in mild cases due to the self-resolving nature of M. pneumonia infection, regardless of macrolide resistance. In contrast, antibiotic treatment of severe cases of M. pneumoniae pneumonia is complicated. The clinical benefit of tetracyclines and fluoroquinolones has been shown in terms of shortening duration of symptoms and rapid defervescence in some reports. However, due to safety concerns regarding these two alternative antibiotics, clinicians should weigh the risks and benefits when choosing treatment options. Alternative antibiotics may be considered when patients remain febrile or when chest x-rays show deterioration at least 48-72 hours after macrolide treatment.

Capsular polysaccharide gene diversity of pneumococcal serotypes 6A, 6B, 6C, and 6D.

This study was performed to better understand the genetic diversity and evolutionary relatedness of pneumococcal serotypes 6A, 6B, 6C, and 6D. Multi-locus sequence typing (MLST) was performed for 160 serogroup 6 isolates from clinical specimens collected from children between 1991 and 2010. We identified 38 sequence types (STs) comprising five clonal complexes with 12 singletons. Although most STs were confined to a single serotype, some STs were shared by two serotypes, and one ST was shared by three serotypes. Many STs of serotype 6A showed genetic relatedness with those of serotype 6C or 6D in eBURST analysis. Five capsular polysaccharide (cps) genes - wchA, wciO, wciP, wzy, and wzx - were analysed in 74 isolates from our clinical samples and in 36 isolates from GenBank. There were several profiles and clades in each serotype on the analysis of the concatenated sequences of the five cps genes. Small genetic distances between serotypes 6A and 6B and between serotypes 6C and 6D were observed while serotype 6B with an indel sequence formed a distinct clade. When comparing the individual cps genes between the serotypes, there was also a high level of similarity in the wchA and wciO gene sequences between serotype 6C and serotype 6D. On the other hand, serotypes 6A and 6D had the most highly similar wzy and wzx gene sequences. The wzy sequences of serotype 6C were nearly identical (99.6%) to those of serotype 6A clade II strains. In conclusion, we revealed the diversity of the genetic background and cps sequences in each pneumococcal serotype of serogroup 6. Pneumococcal serotype diversity might be attributable to complex serial mutation and recombination events.

The Etiology, Clinical Presentation and Long-term Outcome of Spondylodiscitis in Children.

Background: Spondylodiscitis (SD) is a rare disease in children and diagnosis can be delayed because of the scarcity in incidence and lack of awareness. The purpose of this study was to evaluate and report the microbiologic epidemiology and clinical features of pediatric SD in South Korea. Methods: This was a retrospective study of children <19 years old admitted for the treatment of SD between 2000 and 2014. Electronic medical records were reviewed for clinical parameters and etiologic agents. Results: During the 15-year period, 25 patients were diagnosed with SD. The median age was 13.8 years, and 60% were male. Back pain was the most common presenting symptom (n = 17; 68%), and only 52% (n = 13) of the patients had a history of fever (≥38.0°C). In patients younger than 3 years, irritability (n = 5; 62.5%) was the most predominant symptom. Microorganisms were isolated in 22 cases, the most common being Staphylococcus aureus (40%) and Mycobacterium tuberculosis (32%). Of the 25 patients, 64% (n = 16) had blood cultures taken, 56% (n = 14) underwent percutaneous fluoroscopy-guided biopsy, and 48% (n = 12) underwent open surgical biopsy. The positive rate for microbiologic diagnosis of each method was 18.8% (n = 3) for blood culture, 71.4% (n = 10) for percutaneous biopsy and 100% (n = 12) for surgical biopsy. Overall, 52% (n = 13) needed surgical treatment along with antibiotic therapy. Patients who needed surgery had a significant delay in diagnosis compared with those that did not (median, 60 vs. 31 days; P = 0.014). Conclusions: S. aureus and M. tuberculosis are the predominant causes of SD in children in South Korea. Obtaining tissue culture is important to confirm the bacterial etiology of the infection and appropriately guide antibiotic therapy in a community in which the endemic organisms require treatment pathways that are widely divergent.

Diversity of Pneumolysin and Pneumococcal Histidine Triad Protein D of Streptococcus pneumoniae Isolated from Invasive Diseases in Korean Children.

Pneumolysin (Ply) and pneumococcal histidine triad protein D (PhtD) are candidate proteins for a next-generation pneumococcal vaccine. We aimed to analyze the genetic diversity and antigenic heterogeneity of Ply and PhtD for 173 pneumococci isolated from invasive diseases in Korean children. Allele was designated based on the variation of amino acid sequence. Antigenicity was predicted by the amino acid hydrophobicity of the region. There were seven and 39 allele types for the ply and phtD genes, respectively. The nucleotide sequence identity was 97.2%-99.9% for ply and 91.4%-98.0% for phtD gene. Only minor variations in hydrophobicity were noted among the antigenicity plots of Ply and PhtD. Overall, the allele types of the ply and phtD genes were remarkably homogeneous, and the antigenic diversity of the corresponding proteins was very limited. The Ply and PhtD could be useful antigens for universal pneumococcal vaccines.

Clinical Characteristics and Risk Factors of Long-term Central Venous Catheter–associated Bloodstream Infections in Children

Background: Central line–associated bloodstream infections (CLABSIs) account for significant morbidity and mortality in patients with long-term central venous catheters (CVCs). This study was performed to identify the characteristics and risk factors of CLABSIs among children with long-term CVCs. Methods: A retrospective review of children who had a long-term CVC in Seoul National University Children’s Hospital between 2011 and 2015 was performed. Data on patient demographics, the isolated pathogens and the status of CVC placement were collected. Clinical variables were compared between subjects with and without CLABSIs to determine the risk factors for CLABSIs. Results: A total of 629 CVCs were inserted in 499 children during the 5-year period. The median age at insertion was 6.0 years (14 days–17.9 years), and hemato-oncologic disease was the most common underlying condition (n = 497, 79.0%). A total of 235 CLABSI episodes occurred in 155 children, with a rate of 0.93 per 1,000 catheter days. The most common pathogens were Klebsiella pneumoniae (n = 64, 27.2%), coagulase-negative staphylococci (n = 40, 17.0%) and Staphylococcus aureus (n = 28, 12.0%). In the univariate analysis, the gender, underlying disease, catheter characteristics and insertion technique did not increase the risk for CLABSI. In both the univariate and logistic regression analyses, patients with prior BSIs (odds ratio 1.66; 95% confidence interval: 1.090–2.531; P = 0.018) were more likely to have a CLABSI. Conclusions: CLABSI prevention is of particular concern for children with a prior BSI. Furthermore, the antimicrobial resistance of major pathogens should be monitored to enable the empiric selection of appropriate antibiotics in patients with long-term CVCs.

Genetic diversity of pneumococcal surface protein A in invasive pneumococcal isolates from Korean children, 1991-2016

Pneumococcal surface protein A (PspA) is an important virulence factor of pneumococci and has been investigated as a primary component of a capsular serotype-independent pneumococcal vaccine. Thus, we sought to determine the genetic diversity of PspA to explore its potential as a vaccine candidate. Among the 190 invasive pneumococcal isolates collected from Korean children between 1991 and 2016, two (1.1%) isolates were found to have no pspA by multiple polymerase chain reactions. The full length pspA genes from 185 pneumococcal isolates were sequenced. The length of pspA varied, ranging from 1,719 to 2,301 base pairs with 55.7–100% nucleotide identity. Based on the sequences of the clade-defining regions, 68.7% and 49.7% were in PspA family 2 and clade 3/family 2, respectively. PspA clade types were correlated with genotypes using multilocus sequence typing and divided into several subclades based on diversity analysis of the N-terminal α-helical regions, which showed nucleotide sequence identities of 45.7–100% and amino acid sequence identities of 23.1–100%. Putative antigenicity plots were also diverse among individual clades and subclades. The differences in antigenicity patterns were concentrated within the N-terminal 120 amino acids. In conclusion, the N-terminal α-helical domain, which is known to be the major immunogenic portion of PspA, is genetically variable and should be further evaluated for antigenic differences and cross-reactivity between various PspA types from pneumococcal isolates.