Mitochondrial genome diversity of Balamuthia mandrillaris revealed by a fatal case of granulomatous amoebic encephalitis.

Introduction: Balamuthia (B.) mandrillaris is a free-living amoeba that can cause rare yet fatal granulomatous amoebic encephalitis (GAE). However, efficacious treatment for GAE is currently unavailable, especially when genomic studies on B. mandrillaris are limited. Methods: In this study, B. mandrillaris strain KM-20 was isolated from the brain tissue of a GAE patient, and its mitochondrial genome was de novo assembled using high-coverage Nanopore long reads and Illumina short reads. Results and Discussion: Phylogenetic and comparative analyses revealed a range of diversification in the mitochondrial genome of KM-20 and nine other B. mandrillaris strains. According to the mitochondrial genome alignment, one of the most variable regions was observed in the ribosomal protein S3 (rps3), which was caused by an array of novel protein tandem repeats. The repeating units in the rps3 protein tandem region present significant copy number variations (CNVs) among B. mandrillaris strains and suggest KM-20 as the most divergent strain for its highly variable sequence and highest copy number in rps3. Moreover, mitochondrial heteroplasmy was observed in strain V039, and two genotypes of rps3 are caused by the CNVs in the tandem repeats. Taken together, the copy number and sequence variations of the protein tandem repeats enable rps3 to be a perfect target for clinical genotyping assay for B. mandrillaris. The mitochondrial genome diversity of B. mandrillaris paves the way to investigate the phylogeny and diversification of pathogenic amoebae.

Immunogenicity and Reactogenicity of mRNA BNT162b2 COVID-19 Vaccine among Thai Adolescents with Chronic Diseases.

Adolescents with underlying diseases are at risk of severe COVID-19. The immune response of BNT162b2 may be poor among immunocompromised adolescents. We aim to describe immunogenicity of mRNA BNT162b2 among adolescents who are immunocompromised or have chronic diseases. We recruited adolescents 12-18 years of age; group A impaired-immunity (post-transplantation, cancer, on immunosuppressive drugs) and group B chronic diseases. A two-dose regimen of BNT162b2 was given. Immunogenicity was determined by surrogate virus neutralization test (sVNT) and IgG against receptor-binding domain (RBD). From August to October 2021, 312 adolescents, with a median age (IQR) of 15 years (13.7-16.5), were enrolled (group A 100, group B 212). The geometric means (GMs) of sVNT (% inhibition) against Delta strain and anti-RBD IgG (BAU/mL) after the 2nd dose among group A were: post-transplantation recipients 52.9 (95% CI 37.7-74.2) and 233.6 (95% CI 79-690.6); adolescents with cancer 62.3 (95% CI 29.2-133.1) and 214.9(95% CI 34.2-1348.6); and adolescents with other immunosuppressive conditions 66.7 (95% CI 52.4-84.8) and 849.8 (95% CI 393.4-1835.8). In group B were: adolescents living with HIV 98 (95% CI 97.3-98.8) and 3240.3 (95% CI 2699-3890.2), and adolescents with other chronic disease 98.6 (95% CI 98.3-98.9) and 3818.5 (95% CI 3490.4-4177.4). At day 90, immunity declined; among impaired-immunity participants were 43.9 (95% CI 30.8-62.4) and 178.7 (95% CI 91.2-350.1) and adolescents with chronic diseases were 90.6 (95% CI 88.4-92.8) and 1037.1 (95% CI 933.3-1152.5). In conclusion, adolescents with impaired immunity had a poor response to 2-doses of BNT162b2, additional dose should be considered. Adolescents with chronic diseases had excellent response but immunity waned after 3 m, booster dose may be required.

HBV Seroprotection and Anamnestic Response to Booster Vaccination in Pediatric Cancer Survivors.

Hepatitis B is a major global health concern and can be prevented in the era of vaccination. Impaired immunological memory to primary immunization is a common chemotherapy-related complication among cancer survivors. The study aimed to determine protective immunity against hepatitis B virus (HBV) and anamnestic response to booster vaccination. In all, 107 pediatric cancer survivors previously immunized with primary hepatitis B vaccination were enrolled. A hepatitis B booster dose was administered to those with suboptimal seroprotection (anti-HBs < 10 mIU/mL) and 2 additional doses were subsequently administered at 1 and 6 months to those whose anti-HBs remained low. Clinical and serologic parameters were analyzed. Sero-protective rate against HBV (anti-HBs ≥ 10 mIU/mL) among survivors was 20.6% with geometric mean titer (GMT) of 95.7 ± 265.6 mIU/mL. Anamnestic response was 61% after a booster vaccine among those with suboptimal seroprotection and 100% after 2 additional booster doses among those whose anti-HBs remained low. GMTs among those survivors after the First and third booster vaccines were 320.0 ± 412.4 mIU/mL and 826.5 ± 343.8 mIU/mL, respectively. Age at diagnosis was a significant independent risk factor for adequate seroprotection (adjusted OR = 0.84, 95%CI: 0.71-0.99) with a P-value of .034. No associated risk factors to predict optimal anamnestic response to booster vaccination were identified. Loss of immunological memory to primary hepatitis B immunization is an inevitable complication among most pediatric cancer survivors; therefore, assessing adequate seroprotection is essentially required. For those with limited accessibility to serologic tests, completion of full 3-booster-dose series is alternative and highly recommended.

Clinical Characteristics and Predictive Factors of Invasive Fungal Disease in Pediatric Oncology Patients with Febrile Neutropenia in a Country with Limited Resources.

BACKGROUND: The most common complication among pediatric oncology patients is febrile neutropenia (FN). Invasive fungal disease (IFD) is suspected when fever persists >4-7 days after empirical antibiotics. Its clinical characteristics and predictive factors associated with IFD among pediatric oncology patients with FN were thus explored. METHODS: Pediatric oncology patients with FN between January 1, 2012 and December 31, 2016 were enrolled in this study. Clinical characteristics, including laboratory investigations, treatment modalities, and final outcomes of IFD were retrospectively reviewed and analyzed. RESULTS: In all, 73 patients with 180 episodes of confirmed diagnosis of FN were studied. Median age at diagnosis was 6.2 years, with equal sex distribution. The most common diagnosis was acute lymphoblastic leukemia (n=91, 51%), followed by acute myeloid leukemia (n=47, 26%), Burkitt's lymphoma (n=7, 4%) and neuroblastoma (n=7, 4%). Median absolute neutrophil count at FN diagnosis was 0 (0-806) cells/mm3. IFD was diagnosed for 25 (14%) episodes. Mortality rates for FN and IFD were 4% and 20%, respectively. Respiratory compromise, oxygen requirement, hypotension, prolonged hospitalization, duration of fever and neutropenia, bacteremia, bacteriuria, funguria, abnormal liver-function results, and prolonged broad-spectrum antibiotic administration were factors associated with IFD (P<0.05). Prolonged duration between initiation of fever and antifungal administration for nearly 10 days was an independent factor in prediction of IFD occurrence (P=0.014). CONCLUSION: Respiratory compromise, oxygen requirement, hypotension, prolonged hospitalization, duration of fever and neutropenia, bacteremia, bacteriuria, funguria, abnormal liver-function results and prolonged broad-spectrum antibiotic administration were factors associated with IFD. Duration between initiation of fever and antifungal administration of nearly 10 days were considered a risk factors of IFD among patients with FN. IRB REFERENCE NUMBER: IRBRTA 825/2560.

Serum Lactate: A Predictor of Septic Shock in Childhood Cancers with Febrile Neutropenia.

Early recognition and management are the key elements to prevent febrile neutropenia associated mortality. The prospective observational study aimed to investigate prognostic accuracy of serum lactate to predict septic shock within 48 hours among hemodynamically stable children with febrile neutropenia. In all, 99 pediatric oncology patients who developed febrile neutropenia were enrolled in the study. Clinical information during 48 hours and serum lactate at the time of enrollment were analyzed. Among 99 participating patients, 10 developed septic shock and 4 of those expired. No significant difference was found of patients' baseline characteristics and basic laboratory parameters between patients with and without septic shock. Serum lactate was significantly elevated among patients developing septic shock (P-value < .001) and those who expired (P-value .002). Receiver operating characteristic (ROC) curve was created to identify the best cutoff value for initial serum lactate associated with the development of septic shock within 48 hours. Baseline serum lactate more than 2.5 mmol/L showed the largest area under the ROC curve to predict the septic shock development within 48 hours (ROC area, 0.90; 95% confidence interval [CI], 0.81-0.98), with sensitivity, specificity, negative predictive value, and accuracy of 80.0%, 92.1%, 97.6%, and 90.9%, respectively. Serum lactate level determined early at the time of febrile neutropenia was an effective surrogate marker for developing septic shock within 48 hours among hemodynamically stable, pediatric oncology patients. The level more than 2.5 mmol/L was the best threshold to start preemptive aggressive hemodynamic monitoring and prompt treatment to ensure adequate tissue perfusion.

Clinical epidemiology, risk factors and treatment outcomes of extended-spectrum beta-lactamase producing Enterobacteriaceae bacteremia among children in a Tertiary Care Hospital, Bangkok, Thailand.

OBJECTIVE: Extended-spectrum beta-lactamase (ESBL) producing Enterobacteriaceae infection is an emerging problem in paediatric populations leading to increased mortality. The purpose of this study was to determine the prevalence, risk factors and clinical outcomes of ESBL-producing Enterobacteriaceae in paediatric blood stream infections (BSIs). A retrospective review of paediatric patients diagnosed with Enterobacteriaceae bacteremia was performed at Phramongkutklao Hospital from 2010 to 2017. RESULTS: Among 97 non-duplicated blood isolates, the prevalence of ESBL-producing Enterobacteriaceae was 53.6% (28.9% Escherichia coli and 25.8% Klebsiella spp. isolates). The study indicated that the prevalence of ESBL infection was higher among patients with chronic illness, especially hematologic malignancies, than among patients without underlying disease (P = 0.01). No differences were observed in the prior use of any antibiotics, the use of extended-spectrum cephalosporin, neutropaenia or the presence of an indwelling central venous catheter. Mortality in the ESBL group was significantly higher than that in the non-ESBL group, with observed mortalities of 38.9% and 13.3%, respectively (P < 0.05). In conclusion, BSIs with ESBL-producing Enterobacteriaceae tended to increase infection rates and impact survival rates among paediatric patients.