Eun-Geun Kim

A rapid antimicrobial susceptibility test based on single-cell morphological analysis

An antimicrobial susceptibility test rapidly identifies bacterial response to drugs based on imaged morphology of single cells. Microbes Get in Shape for Antibiotic Testing Conventional tests that measure bacteria susceptibility to antibiotics rely on a change in occupied area. Thus, a positive change in area indicates that the bacteria is growing and is resistant to the drug, right? Not always: Bacteria can also take on different shapes, such as filaments, or swell; these changes increase the area, but the bug is still susceptible to the antibiotic. Choi et al. therefore devised an imaging-based antibiotic susceptibility test (AST) that factors in changes in morphology, to rapidly determine whether single bacteria, confined to microwells, respond to various drugs. The authors looked at four standard strains, including antibiotic-resistant pathogens such as methicillin-resistant Staphylococcus aureus (MRSA), as well as clinical samples, in response to dozens of different antibiotics used in the clinic. The single-cell morphology AST performed as well as the gold standard, culture-based broth microdilution test, with read-out in only 4 hours. Such a rapid and accurate screen could improve time-to-answer in the clinic by avoiding conventional culture methods, thus allowing for faster decision making in administering proper antibiotics to patients. A rapid antibiotic susceptibility test (AST) is desperately needed in clinical settings for fast and appropriate antibiotic administration. Traditional ASTs, which rely on cell culture, are not suitable for urgent cases of bacterial infection and antibiotic resistance owing to their relatively long test times. We describe a novel AST called single-cell morphological analysis (SCMA) that can determine antimicrobial susceptibility by automatically analyzing and categorizing morphological changes in single bacterial cells under various antimicrobial conditions. The SCMA was tested with four Clinical and Laboratory Standards Institute standard bacterial strains and 189 clinical samples, including extended-spectrum β-lactamase–positive Escherichia coli and Klebsiella pneumoniae, imipenem-resistant Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus, and vancomycin-resistant Enterococci from hospitals. The results were compared with the gold standard broth microdilution test. The SCMA results were obtained in less than 4 hours, with 91.5% categorical agreement and 6.51% minor, 2.56% major, and 1.49% very major discrepancies. Thus, SCMA provides rapid and accurate antimicrobial susceptibility data that satisfy the recommended performance of the U.S. Food and Drug Administration.

Optofluidic in situ maskless lithography of charge selective nanoporous hydrogel for DNA preconcentration.

An optofluidic maskless photopolymerization process was developed for in situ negatively charged nanoporous hydrogel [poly-AMPS (2-acrylamido-2-methyl-1-propanesulfonic acid)] fabrication. The optofluidic maskless lithography system, which combines a high power UV source and digital mirror device, enables fast polymerization of arbitrary shaped hydrogels in a microfluidic device. The poly-AMPS hydrogel structures were positioned near the intersections of two microchannels, and were used as a cation-selective filter for biological sample preconcentration. Preconcentration dynamics as well as the fabricated polymer shape were analyzed in three-dimensions using fluorescein sample and a confocal microscope. Finally, single-stranded DNA preconcentration was demonstrated for polymerase chain reaction-free signal enhancement.

Effects of an alveolar recruitment manoeuvre guided by lung ultrasound on anaesthesia-induced atelectasis in infants: a randomised, controlled trial

Atelectasis occurs in the majority of children undergoing general anaesthesia. Lung ultrasound has shown reliable sensitivity and specificity for diagnosing anaesthesia‐induced atelectasis. We assessed the effects of a recruitment manoeuvre on atelectasis using lung ultrasound in infants undergoing general anaesthesia. Forty infants, randomly allocated to either a recruitment manoeuvre group or a control group, received volume‐controlled ventilation with 5 cmH2O positive end‐expiratory pressure. Lung ultrasound examination was performed twice in each patient, the first a minute after starting mechanical ventilation of the lungs and the second at the end of surgery. Patients in the recruitment manoeuvre group received ultrasound‐guided recruitment manoeuvres after each lung ultrasound examination. The incidence of significant anaesthesia‐induced atelectasis at the second lung ultrasound examination was less in the recruitment manoeuvre group compared with the control group (25% vs. 80%; p = 0.001; odds ratio (OR) 0.083; 95% confidence interval (CI): 0.019–0.370). The median (IQR [range]) lung ultrasound scores for consolidation and B‐lines on the second examination were lower in the recruitment manoeuvre group compared with the control group; 6.0 (3.0–9.3 [0.0–14.0]) vs. 13.5 (11.0–16.5 [8.0–23.0]); p < 0.001 and 6.5 (3.0–12.0 [0.0–28.0]) vs. 15.0 (10.8–20.5 [7.0–28.0]); p < 0.001, respectively. The lung ultrasound scores for consolidation on the first and second examinations showed a negative correlation with age (r = −0.340, p = 0.008; r = −0.380, p = 0.003). We conclude that ultrasound‐guided recruitment manoeuvres with positive end‐expiratory pressure proved useful in reducing the incidence of anaesthesia‐induced atelectasis in infants, although 5 cmH2O positive end‐expiratory pressure alone was not sufficient to eliminate it. In addition, the younger the patient, the more susceptible they were to atelectasis.

The effect of 6% hydroxyethyl starch (130/0.4) on acute kidney injury in paediatric cardiac surgery: a prospective, randomised trial

We have evaluated the effect of a colloid solution on acute kidney injury in paediatric cardiac surgery. A total of 195 patients were ramdomly divided into an hydroxyethyl starch group and a control group. In the starch group, 6% hydroxyethyl starch 130/0.4 (Volulyte®) was used as the primary fluid for volume resuscitation but was limited to 30 ml.kg−1. In the control group, only crystalloid fluid was used during the peri‐operative period. The incidence of acute kidney injury, peri‐operative transfusion, clinical outcomes and laboratory data were compared. The incidence of acute kidney injury determined by Paediatric Risk, Injury, Failure, Loss, End‐stage renal disease (pRIFLE) and Acute Kidney Injury Network (AKIN) criteria were no different between the two groups (starch group 40.8% vs. control group 30.0%; p = 0.150 using pRIFLE; 19.6% vs. 21.1% respectively, p = 0.602 using AKIN). There were no differences in clinical outcomes such as mortality, major adverse events, intensive care unit stay or duration of mechanical ventilation. Clotting time as measured using rotational thromboelastometry (ROTEM) was prolonged, and clot firmness after 10 min and maximal clot firmness were shorter in the starch group compared with the control group after sternal closure. There was no difference in transfusion between the two groups. Patients with acute kidney injury had worse clinical courses than those without acute kidney injury. We conclude that intra‐operative use of 6% hydroxyethyl starch 130/0.4 up to 30 ml.kg−1 was not associated with postoperative acute kidney injury in paediatric cardiac patients.

Ultrasound assessment of gastric volume in children after drinking carbohydrate-containing fluids

BACKGROUND Gastric ultrasound is a valid tool for non-invasive assessment of the nature and volume of gastric contents in adults and children. Perioperative fasting guidelines recommend oral carbohydrates up to 2 h before elective surgery. We evaluated gastric volume in children using ultrasound before and after drinking carbohydrate fluids before surgery. METHODS Paediatric patients younger than 18 yr old undergoing elective surgery were enrolled. Initial ultrasound assessment of gastric volume was performed after fasting for 8 h. Two hours before surgery, patients were given carbohydrate drinks: 15 ml kg(-1) for patients younger than 3 yr old and 10 ml kg(-1) for those more than 3 yr old. Before induction of general anaesthesia, the gastric volume was reassessed. Parental satisfaction scores (0=totally satisfied, 10=totally dissatisfied) and complications were recorded. RESULTS Of the 86 enrolled patients, 79 completed the study; three refused to ingest the requested volume, and surgery was delayed for more than 2 h in four patients. The mean (sd) of the initial and second ultrasound measurements were 2.09 (0.97) and 1.85 (0.94) cm(2), respectively (P=0.01; mean difference 0.24 cm(2), 95% confidence interval 0.06-0.43). The median (interquartile range) satisfaction score was 2.4 (0-6). Two instances of postoperative vomiting and one instance of postoperative nausea occurred. CONCLUSIONS Carbohydrate fluids ingested 2 h before surgery reduced the gastric volume and did not cause serious complications in paediatric patients. Parents were satisfied with the preoperative carbohydrate drink. Children may benefit from drinking carbohydrate fluids up to 2 h before elective surgery. CLINICAL TRIAL REGISTRATION cris.nih.go.kr (KCT0001546).

Effect of early vs. late tracheostomy on clinical outcomes in critically ill pediatric patients

Few studies investigated the optimal timing for tracheostomy and its influence on the clinical outcomes in critically ill pediatric patients. This study evaluated the differences in clinical outcomes between early and late tracheostomy in pediatric intensive care unit (ICU) patients.

A rapid culture system uninfluenced by an inoculum effect increases reliability and convenience for drug susceptibility testing of Mycobacterium tuberculosis

The Disc Agarose Channel (DAC) system utilizes microfluidics and imaging technologies and is fully automated and capable of tracking single cell growth to produce Mycobacterium tuberculosis (MTB) drug susceptibility testing (DST) results within 3~7 days. In particular, this system can be easily used to perform DSTs without the fastidious preparation of the inoculum of MTB cells. Inoculum effect is one of the major problems that causes DST errors. The DAC system was not influenced by the inoculum effect and produced reliable DST results. In this system, the minimum inhibitory concentration (MIC) values of the first-line drugs were consistent regardless of inoculum sizes ranging from ~103 to ~108 CFU/mL. The consistent MIC results enabled us to determine the critical concentrations for 12 anti-tuberculosis drugs. Based on the determined critical concentrations, further DSTs were performed with 254 MTB clinical isolates without measuring an inoculum size. There were high agreement rates (96.3%) between the DAC system and the absolute concentration method using Löwenstein-Jensen medium. According to these results, the DAC system is the first DST system that is not affected by the inoculum effect. It can thus increase reliability and convenience for DST of MTB. We expect that this system will be a potential substitute for conventional DST systems.

Seldinger vs modified Seldinger techniques for ultrasound-guided central venous catheterisation in neonates: a randomised controlled trial

Background: Central venous catheterisation in neonates is difficult. The purpose of this study was to compare the Seldinger and modified Seldinger techniques for ultrasound‐guided internal jugular vein catheterisation in neonates. Methods: In this randomised, controlled trial, 120 neonates (≤1 month old) requiring central venous catheterisation under general anaesthesia were allocated into either the Seldinger (n=60) or the modified Seldinger (n=60) group. The primary outcome was the incidence of successful catheterisation on the first attempt. We also assessed the incidences of successful puncture on the first attempt, successful guide wire insertion on the first attempt, and successful final catheterisation. Results: The primary outcome, the incidence of successful catheterisation on the first attempt was higher in the modified Seldinger group than in the Seldinger group (83% vs 65%; relative risk=1.282; 95% confidence interval, 1.032–1.594; P=0.025). The incidence of successful guide wire insertion on the first attempt was also higher in the modified Seldinger group (95% vs 75%; relative risk=1.267; 95% confidence interval, 1.082–1.482; P=0.003). Other incidences did not differ significantly between the groups. Conclusions: For ultrasound‐guided internal jugular vein catheterisation in neonates, the modified Seldinger technique showed superiority over the Seldinger technique in terms of successful catheterisation and guide wire insertion on the first attempt. Clinical trial registration: NCT02688595.

Clinical Evaluation of QMAC-dRAST for Direct and Rapid Antimicrobial Susceptibility Test with Gram-Positive Cocci from Positive Blood Culture Bottles

QuantaMatrix Inc., Institutes of Entrepreneurial BioConvergence, Seoul National University, Department of Electrical and Computer Engineering, Seoul National University, Department of Transdisciplinary Studies, Seoul National University, Department of Laboratory Medicine, Seoul National University Hospital, Seoul National University Hospital Biomedical Research Institute, Seoul National University Hospital, Seoul, Korea

Flexion decreases the ventilation quality of the Ambu® AuraGain™ laryngeal mask in paralysed children: A prospective randomised crossover study

The influence of different head and neck positions on ventilation with the Ambu® AuraGain™ remains unevaluated in children. This study assessed the influence of different head and neck positions on ventilation with the AuraGain™ in paediatric patients.