Susceptibility to Fosfomycin and Nitrofurantoin of ESBL-PositiveEscherichia coli and Klebsiella pneumoniae Isolated From Urine of Pediatric Patients

Background@#Pediatric urinary tract infection (UTI) caused by extended-spectrum β-lactamase (ESBL)-positive gram-negative bacilli (GNB) has limited options for oral antibiotic treatment. The purpose of this study was to investigate the susceptibility of ESBLpositive Escherichia coli and Klebsiella pneumoniae isolates from pediatric urine samples to two oral antibiotics (fosfomycin and nitrofurantoin). @*Methods@#From November 2020 to April 2022, ESBL-positive E. coli and K. pneumoniae isolates from urine samples were collected at Samsung Medical Center, Seoul, Korea. Patients over 18 years of age or with malignancy were excluded. For repeated isolates from the same patient, only the first isolate was tested. Minimum inhibitory concentrations (MICs) were measured using agar (fosfomycin) or broth (nitrofurantoin) dilution methods. MIC 50 and MIC 90 were measured for fosfomycin and nitrofurantoin in both E. coli and K. pneumoniae. @*Results@#There were 117 isolates from 117 patients, with a median age of 7 months (range, 0.0–18.5 years). Among 117 isolates, 92.3% (108/117) were E. coli and 7.7% (9/117) were K. pneumoniae. Isolates from the pediatric intensive care unit (PICU) and general ward (GW) was 11.1% (13/117) and 88.9% (104/117), respectively. Among 108 E. coli isolates, MIC 50 and MIC 90 for fosfomycin were 0.5 μg/mL and 2 μg/mL, respectively. Fosfomycin susceptibility rate was 97.2% (105/108) with a breakpoint of 128 μg/mL. Fosfomycin susceptibility rate was significantly lower in PICU isolates than in GW isolates (81.8% vs. 99.0%, P = 0.027).For nitrofurantoin, both the MIC 50 and MIC 90 were 16 μg/mL. Nitrofurantoin susceptibility rate was 96.3% (104/108) with a breakpoint of 64 μg/mL based on Clinical and Laboratory Standards Institute guidelines. Among the nine K. pneumoniae isolates, the MIC 50 and MIC 90 for fosfomycin was 2 μg/mL and 32 μg/mL, respectively. MIC 50 and MIC 90 for nitrofurantoin were 64 μg/mL and 128 μg/mL, respectively. @*Conclusion@#For uncomplicated UTI caused by ESBL-positive GNB in Korean children, treatment with fosfomycin and nitrofurantoin for E. coli infections can be considered as an effective oral therapy option.

The Changes in Epidemiology of Imipenem-Resistant Acinetobacter baumannii Bacteremia in a Pediatric Intensive Care Unit for 17 Years

Background@#Acinetobacter baumannii infections cause high morbidity and mortality in intensive care unit (ICU) patients. However, there are limited data on the changes of longterm epidemiology of imipenem resistance in A. baumannii bacteremia among pediatric ICU (PICU) patients. @*Methods@#A retrospective review was performed on patients with A. baumannii bacteremia in PICU of a tertiary teaching hospital from 2000 to 2016. Antimicrobial susceptibility tests, multilocus sequence typing (MLST), and polymerase chain reaction for antimicrobial resistance genes were performed for available isolates. @*Results@#A. baumannii bacteremia occurred in 27 patients; imipenem-sensitive A. baumannii (ISAB, n = 10, 37%) and imipenem-resistant A. baumannii (IRAB, n = 17, 63%). There was a clear shift in the antibiogram of A. baumannii during the study period. From 2000 to 2003, all isolates were ISAB (n = 6). From 2005 to 2008, both IRAB (n = 5) and ISAB (n = 4) were isolated. However, from 2009, all isolates were IRAB (n = 12). Ten isolates were available for additional test and confirmed as IRAB. MLST analysis showed that among 10 isolates, sequence type 138 was predominant (n = 7). All 10 isolates were positive for OXA-23-like and OXA-51-like carbapenemase. Of 27 bacteremia patients, 11 were male (41%), the median age at bacteremia onset was 5.2 years (range, 0–18.6 years). In 33% (9/27) of patients, A. baumannii was isolated from tracheal aspirate prior to development of bacteremia (median, 8 days; range, 5–124 days). The overall case-fatality rate was 63% (17/27) within 28 days. There was no statistical difference in the case fatality rate between ISAB and IRAB groups (50% vs. 71%; P = 0.422). @*Conclusion@#IRAB bacteremia causes serious threat in patients in PICU. Proactive infection control measures and antimicrobial stewardship are crucial for managing IRAB infection in PICU.

Molecular Epidemiology of Bacillus cereus in a Pediatric Cancer Center

PURPOSE: Bacillus cereus has been reported as the cause of nosocomial infections in cancer patients. In our pediatric cancer ward, a sudden rise in the number of patients with B. cereus bacteremia was observed in 2013 to 2014. This study was performed to investigate the molecular epidemiology of increased B. cereus bacteremia cases in our center. METHODS: Pediatric cancer patients who developed B. cereus bacteremia were identified from January 2001 to June 2014. The B. cereus bacteremia in this study was defined as a case in which at least one B. cereus identified in blood cultures, regardless of true bacteremia. Available isolates were further tested by multilocus sequence typing (MLST) analysis. A retrospective chart review was performed. RESULTS: Nineteen patients developed B. cereus bacteremia during the study period. However, in 2013, a sudden increase in the number of patients with B. cereus bacteremia was observed. In addition, three patients developed B. cereus bacteremia within 1 week in July and the other three patients within 1 week in October, respectively, during emergency room renovation. However, MLST analysis revealed different sequence types without consistent patterns. Before 2013, five tested isolates were ST18, ST26, ST177, and ST147-like type, and ST219-like type. Isolates from 2013 were ST18, ST73, ST90, ST427, ST784, ST34-like type, and ST130-like type. CONCLUSIONS: MLST analyses showed variable ST distribution of B. cereus isolates. Based on this study, there was no significant evidence suggesting a true outbreak caused by a single ST among patients who developed B. cereus bacteremia.

Antibody Responses in Hematopoietic Cell Transplantation Recipients after Vaccination Against Haemophilus Influenzae Type b and Streptococcus pneumoniae / 소아감염

PURPOSE: Hematopoietic cell transplantation (HCT) recipients are vulnerable to invasive infection by Haemophilus influenzae type b (Hib) and Streptococcus pneumoniae (Sp). This study was performed to evaluate immune responses after Hib and Sp vaccination in Korean pediatric HCT recipients. METHODS: Patients were prospectively enrolled at Samsung Medical Center during 2009-2011. ELISA tests to detect anti-PRP IgG antibody and antibodies to Sp serotypes 4, 6B, 9V, 14, 18C, 19F, and 23F were performed at the Center for Vaccine Evaluation and Study, Ewha Medical Research Institute. RESULTS: Ten patients (two allogeneic, eight autologous recipients) with median age 5.4 years (range 2.7-12.2 years) were enrolled. Before Hib vaccination, 60% of patients' anti-PRP IgG titers were below 0.15 microg/mL. After vaccination, 100% of patients' anti-PRP IgG titers increased above 0.15 microg/mL (cut-off value for detection) and 1.0 microg/mL (cut-off value for seroprotection). For pneumococcus, in 2-5 year-old patients, pre-vaccination geometric mean concentrations (GMCs) of IgG for six serotypes (4, 6B, 9V, 14, 18C, and 23F) were below 0.35 microg/mL and at 5 months post-vaccination GMCs of IgG for all seven serotypes increased to above 0.35 microg/mL. In patients older than 5 years, pre-vaccination GMCs of IgG for four serotypes (4, 9V, 14, and 23F) were below 0.35 microg/mL and at 3 months post-vaccination GMCs of IgG for all seven serotypes increased to above 0.35 microg/mL. CONCLUSION: Most HCT recipients had low or no protective antibodies to Hib and Sp before vaccination, but showed good immune responses to protective levels after vaccination.

Decreased Immunoreactivities and Functions of the Chloride Transporters, KCC2 and NKCC1, in the Lateral Superior Olive Neurons of Circling Mice

OBJECTIVES: We tested the possibility of differential expression and function of the potassium-chloride (KCC2) and sodium-potassium-2 chloride (NKCC1) co-transporters in the lateral superior olive (LSO) of heterozygous (+/cir) or homozygous (cir/cir) mice. METHODS: Mice pups aged from postnatal (P) day 9 to 16 were used. Tails from mice were cut for DNA typing. For Immunohistochemical analysis, rabbit polyclonal anti-KCC2 or rabbit polyclonal anti-NKCC1 was used and the density of immunolabelings was evaluated using the NIH image program. For functional analysis, whole cell voltage clamp technique was used in brain stem slices and the changes of reversal potentials were evaluated at various membrane potentials. RESULTS: Immunohistochemical analysis revealed both KCC2 and NKCC1 immunoreactivities were more prominent in heterozygous (+/cir) than homozygous (cir/cir) mice on P day 16. In P9-P12 heterozygous (+/cir) mice, the reversal potential (Egly) of glycine-induced currents was shifted to a more negative potential by 50 microM bumetanide, a known NKCC1 blocker, and the negatively shifted Egly was restored by additional application of 1 mM furosemide, a KCC2 blocker (-58.9+/-2.6 mV to -66.0+/-1.5 mV [bumetanide], -66.0+/-1.5 mV to -59.8+/-2.8 mV [furosemide+bumetanide], n=11). However, only bumetanide was weakly, but significantly effective (-60.1+/-2.9 mV to -62.7+/-2.6 mV [bumetanide], -62.7+/-2.6 mV to -62.1+/-2.5 mV [furosemide+bumetanide], n=7) in P9-P12 homozygous (cir/cir) mice. CONCLUSION: The less prominent immunoreactivities and weak or absent responses to bumetanide or furosemide suggest impaired function or delayed development of both transporters in homozygous (cir/cir) mice.

Decreased Immunoreactivities and Functions of the Chloride Transporters, KCC2 and NKCC1, in the Lateral Superior Olive Neurons of Circling Mice

OBJECTIVES: We tested the possibility of differential expression and function of the potassium-chloride (KCC2) and sodium-potassium-2 chloride (NKCC1) co-transporters in the lateral superior olive (LSO) of heterozygous (+/cir) or homozygous (cir/cir) mice. METHODS: Mice pups aged from postnatal (P) day 9 to 16 were used. Tails from mice were cut for DNA typing. For Immunohistochemical analysis, rabbit polyclonal anti-KCC2 or rabbit polyclonal anti-NKCC1 was used and the density of immunolabelings was evaluated using the NIH image program. For functional analysis, whole cell voltage clamp technique was used in brain stem slices and the changes of reversal potentials were evaluated at various membrane potentials. RESULTS: Immunohistochemical analysis revealed both KCC2 and NKCC1 immunoreactivities were more prominent in heterozygous (+/cir) than homozygous (cir/cir) mice on P day 16. In P9-P12 heterozygous (+/cir) mice, the reversal potential (Egly) of glycine-induced currents was shifted to a more negative potential by 50 microM bumetanide, a known NKCC1 blocker, and the negatively shifted Egly was restored by additional application of 1 mM furosemide, a KCC2 blocker (-58.9+/-2.6 mV to -66.0+/-1.5 mV [bumetanide], -66.0+/-1.5 mV to -59.8+/-2.8 mV [furosemide+bumetanide], n=11). However, only bumetanide was weakly, but significantly effective (-60.1+/-2.9 mV to -62.7+/-2.6 mV [bumetanide], -62.7+/-2.6 mV to -62.1+/-2.5 mV [furosemide+bumetanide], n=7) in P9-P12 homozygous (cir/cir) mice. CONCLUSION: The less prominent immunoreactivities and weak or absent responses to bumetanide or furosemide suggest impaired function or delayed development of both transporters in homozygous (cir/cir) mice.

Effect of Dexamethasone in the Development of O1 or O4 Immunoreactive Oligodendrocyte of the Neonatal Rat / 체질인류학회지

White matter disease (WMD) study, which underlies the subsequent progress of cerebral palsy as well as cognitive impairment of premature and/or low birth weight infants, has been focused either on the hypoxia-ischemia damage or cytokine-induced brain damage related with maternal or fetal inflammation. Also, dexamethasone (DEXA) may increase the risk of neuropsychological problem including adverse cognitive and behavioral outcome in preterm infants. Thus, we hypothesized that perinatal DEXA would damage and trigger the death of developing oligodendrocytes (OL) progenitors, and subsequently disturb myelination. In this study, DEXA was administered to neonatal rats for 3 consecutive days subcutaneously between postnatal day 1 (P1) and P3. By using immunofluorescent staining of stage specific OL progenitor markers such as O4 and O1, the morphological changes of OL progenitors were examined and the apoptosis of OL progenitors were visualized by TUNEL staining. Results depicted that relative number of O1 immunoreactive (IR) cells were less to that of O4 IR cells. Multipolar O1 IR cells with short dendritic processes were observed in both control and DEXA group at P3. In the total O1 immunoreactive cells, the relative percentages of apoptosis cells were calculated at P3 as 8.7% in control, 23.0% in DEXA group. The relative percentages of apoptosis in the total O4 immunoreactive cells were measured at P3 as 3.0% in control and 13.5% in DEXA group. OL progenitors' apoptosis may contribute to the overall reduction of immature OLs in cerebral white matter. Therefore, specific stages of OL maturation could clinically be an important factor in determining the susceptibility to DEXA. To elucidate the disease mechanism of the white matter disease, further investigation may be needed whether OL progenitors' decrease by the DEXA administration affects to the myelin formation as developmental stages.

The Effect of 835 MHz Radiofrequency Radiation Exposure on the Immunohistochemical Distribution of Calbindin D28k and Calretinin in the Mouse Cerebellar Cortex / 체질인류학회지

Widespread use of mobile phones and subsequent electromagnetic field (EMF) exposure have raised crucial question of their possible biological effects on the nervous system. The study on the effect of radiofrequency(RF) radiation on the nervous system, however, did not precede enough to determine the biological hazard to brain. Until now, several studies have reported decreases in neuron number and neuronal damage in the cortex, hippocampus, and basal ganglia in the brains of animals exposed to RF radiation. However, there were few reports about the cerebellum, the main voluntary motor control center. In this regard, by using immunohistochemisty, current study intended to investigate the changes in the calbindin D28k (CB) and calretinin (CR)-immunoreactivity (IR) in the mouse cerebellar cortex after EMF exposure at 835 MHz for different exposure times and absorption rates, 1 h/day for 5 days at 1.6 W/kg, 1 h/day for 5 days at 4.0 W/kg, 5 h/day for 1 day at 1.6 W/kg, 5 h/day for 1 day at 4.0 W/kg, daily exposure for one month at 1.6 W/kg. Among groups, most prominent CB IR was observed in the Purkinje cell layer followed by molecular and granular layer. The highest CB IR was noted in 5 h/day for 1 day at 1.6 W/kg in the entire three layers while the lowest was noted in one month at 1.6 W/kg. Similarly CR IR was maximum in one month at 1.6 W/kg whilst the lowest was observed in 1 h/day for 5 days at 4.0 W/kg. EMF exposure for 5 days at 1.6 W/kg reduced CB-IR. The CR-IR was mainly localized in small cells in the granular layer, with maximum IR observed after one month exposure. Therefore, the present study suggest the possibility of alterations of calcium ion concentration, which play a role in maintaining metabolic homeostasis, in the cerebellum after long-term exposure to 835 MHz of RF radiation, which might lead to thedisruption of normal trait.

Bcl-2 Expression in the Developing Hair Follicle of Korean Fetal Scalp / 대한해부학회지

This study was intended to understand the role of the apoptosis-suppressing gene, bcl-2, in the hair follicle development. Immunohistochemistry for bcl-2 was performed using a high-throughput tissue-array technique, on Korean fetal scalp tissues at the 14 weeks, 16 weeks, 19 weeks & 24 weeks of the development. The results showed that the basal cells of epidermis were stained from 14 weeks to 24 weeks and the immunoreactive melanocytes were observed in the basal layer and suprabasal layer of epidermis as well as in the hair matrix cells and the external root sheath. At 19 weeks, the follicles at all stages of morphogenesis were observed. In the early stages, the epithelial cells of hair germ and hair peg, the mesenchymal cells surrounding them were stained. In the more advanced stage, the bcl-2 expression of follicular epithelial cells diminished to allow keratinization, hair canal formation and holocrine secretion to take place. In the bulbous hair peg stage, the hair papilla cells, the hair matrix cells, the basal cells of the primitive sebaceous gland, the primitive arrector pilli and the basal cells of the external root sheath were stained. We confirmed in the developing hair follicle that in the early stage or in the place where the cells continued to proliferate, the immature cells expressed bcl-2 to suppress cell death to overcome the susceptibility to cell death and when the differentiation was being achieved, the reduction of bcl-2 expression increased cell death to perform the tissue morphogenesis or the organ functions