• Journal of Microbiology and Biotechnology
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• v.20 no.4
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• pp.712-717
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• 2010

Cytochrome P450 enzymes (P450s) are involved in the synthesis of a wide variety of valuable products and in the degradation of numerous toxic compounds. The P450 BM3 (CYP102A1) from Bacillus megaterium was the first P450 discovered to be fused to its redox partner, a mammalian-like diflavin reductase. Here, we report the development of a whole-cell biocatalyst using ice-nucleation protein (Inp) from Pseudomonas syringae to display a hemeand diflavin-containing oxidoreductase, P450 BM3 (a single, 119-kDa polypeptide with domains of both an oxygenase and a reductase) on the surface of Escherichia coli. The surface localization and functionality of the fusion protein containing P450 BM3 were verified by flow cytometry and measurement of enzymatic activities. The results of this study comprise the first report of microbial cell-surface display of a heme- and diflavin-containing enzyme. This system should allow us to select and develop oxidoreductases containing heme and/or flavins into practically useful whole-cell biocatalysts for extensive biotechnological applications, including selective synthesis of new chemicals and pharmaceuticals, bioconversion, bioremediation, live vaccine development, and biochip development.

• Journal of Pharmacopuncture
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• v.19 no.3
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• pp.225-230
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• 2016

Objectives: Mellitine, a major component of bee venom (BV, Apis mellifera), is more active against gram positive than gram negative bacteria. Moreover, BV has been reported to have multiple effects, including antibacterial, antivirus, and anti-inflammation effects, in various types of cells. In addition, wasp venom has been reported to have antibacterial properties. The aim of this study was to evaluate the antibacterial activity of BV against selected gram positive and gram negative bacterial strains of medical importance. Methods: This investigation was set up to evaluate the antibacterial activity of BV against six grams positive and gram negative bacteria, including Staphylococcus aureus (S. aureus), Salmonella typhimurium, Escherichia coli (E. coli) O157:H7, Pseudomonas aeruginosa, Burkholderia mallei and Burkholderia pseudomallei. Three concentrations of crude BV and standard antibiotic (gentamicin) disks as positive controls were tested by using the disc diffusion method. Results: BV was found to have a significant antibacterial effect against E. coli, S. aureus, and Salmonella typhyimurium in all three concentrations tested. However, BV had no noticeable effect on other tested bacteria for any of the three doses tested. Conclusion: The results of the current study indicate that BV inhibits the growth and survival of bacterial strains and that BV can be used as a complementary antimicrobial agent against pathogenic bacteria. BV lacked the effective proteins necessary for it to exhibit antibacterial activity for some specific strains while being very effective against other specific strains. Thus, one may conclude, that Apis mellifera venom may have a specific mechanism that allows it to have an antibacterial effect on certain susceptible bacteria, but that mechanism is not well understood.

• Pediatric Infection and Vaccine
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• v.22 no.3
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• pp.178-185
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• 2015

Purpose: We investigated trends in antibiotic pressure and the antibiotic susceptibility of gram negative bacteria isolated from Korean children over 10 consecutive years. Methods: From January 2004 to December 2013, the antibiotic susceptibility of Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa, and Acinetobacter baumannii blood isolates obtained from children <18 years of age was determined according to the 2009 Clinical and Laboratory Standards Institute guidelines. Antibiotic consumption data were also analyzed. Results: The prevalence of K. pneumoniae, E. coli, P. aeruginosa, and A. baumannii bacteremia was 4.6, 3.5, 3.4, and 2.2 cases/1,000 blood cultures/year, respectively. In K. pneumoniae, resistance to the third and fourth cephalosporin did not increase significantly. However, carbapenem-resistant K. pneumoniae first appeared in 2010, and the resistance rate increased to 9% between 2012 and 2013. Resistance to 3rd and 4th cephalosporin increased from 10% to 50% in E. coli, and resistance to carbapenem rose abruptly from 11% to 71% in A. baumannii (P for trend <0.01). However, such an increase of resistance was not observed in P. aeruginosa. There is a positive correlation between the resistance rate of cefepime in E. coli and the consumption of cefepime (r=0.900, P=0.037). Conclusion: The significant burden of antibiotic consumption and the high prevalence of antibiotic resistance to gram negative pathogen isolated from bacteremic children were observed. Empirical antibiotics should be wisely selected, and continued efforts to decrease the overall antibiotic pressure are mandatory, especially in highly resistant situations.

• Pediatric Infection and Vaccine
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• v.4 no.1
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• pp.79-89
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• 1997

Purpose : Neonatal bacterial meningitis is the disease which clinical manifestations are nonspecific and several neurologic complications may occur. We studied neonatal bacterial meningitis, particularly in treatment and prognosis according to causative organisms -gram positive and gram negative bacteria- to assist in treatment of neonatal bacterial meningitis. Methods : We analysed twenty-four cases retrospectively who had been admitted in NICU or pediatric ward in Chung-ang Gil hospital from Jan. 1991 to Jun. 1996, and who had proven causative organisms in culture or latex agglutination[n test in CSF. Results : 1) The ratio of male to female was 2.4: 1. The mean birth weight and gestational age in cases with gram positive bacterial meningitis were $2.91{\pm}0.79kg$ and $38.4{\pm}2.74$ weeks and those in cases with yam negative bacterial meningitis were $3.30{\pm}0.90kg$ and $37.7{\pm}3.33$weeks respectively. There was no significant difference between the two groups. 2) The perinatal predisposing factors were pematurity, mecoinium staining amnionic fluid, matemal diabetes and pregnancy-induced hypertension, etc. The clinical manifestations Were fever, seizure, poor oral intake and fontanel bulging, etc. There were eleven cases with early onset bacterial meningitis(four cases by gram positive bacteria, seven cases by gram negative bacteria), and thirteen cases with late onset bacterial meningitis(seven cases by gram positive bacteria, six cases by gram negative bacteria). There was no significant difference between the two groups in terms of onset. 3) There were eleven cases with yam positive bacterial meningitis and they were coagulase-negative staphylococci(three cases), group B streptococci(three cases), Staphylococcus aureus(two cases), Streptococcus viridans(two cases), and enterococci(one case). And there were thirteen cases with gram negative bacterial menir gitis and they were Escherichia coli(seven cases), Klevsiella pneumoniae(three cases), Pseudomonas aeruginosa(one case), Acinetobactor(one case) and Enterobacter(one case). 4) The initial CSF WBC counts in cases with yam negative bacterial meningitis were significantly higher than those in cases with gram positive bacterial meningitis but the CSF protein and glucose levels were no significant difference in the two groups statistically. 5) The number of cases with abnormal findings in brain ultrasonography was seven in gram positive bacterial meningitis and ten in gram negative bacterial meningitis. 6) There were relatively high sensitivity to penicillin derivatives, the first generation cephalosporin and vancomycin in gram positive bacteria and to the third generation cephalosporin and amikacin in gram negative bacteria. 7) The mortality rate was 20.8%(5 cases were expired or discharged hopelessly). There was no significant difference between the two groups in prognosis. Conclusions : We recommend active treatment in noenatal bacterial meningitis to improve prognosis because the prognosis is poor.

• Pediatric Infection and Vaccine
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• v.28 no.2
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• pp.82-91
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• 2021

Background: The purpose of this study was to investigate the association between antibiotic use and the antimicrobial resistance of gram-negative bacteria isolated from blood cultures in a pediatric population. Methods: From January 2014 to June 2018, the antibiotic resistance pattern of Acinetobacter baumannii, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa obtained from bacteremic patients aged ≤18 years hospitalized at Asan Medical Center Children's Hospital was analyzed and the parenteral antibiotic consumption data were retrieved. Results: During the study period, the blood culture was positive for K. pneumoniae (6.4%; 105/1,628), E. coli (5.6%; 91/1,628), P. aeruginosa (3.3%; 54/1,628), and A. baumannii (2.5%; 41/1,628), and the extended-spectrum antibiotic resistance rate of gram-negative bacteria was consistently high. The overall resistance rate of E. coli and K. pneumoniae to extendedspectrum cephalosporin was 49.3% and 54.4%, respectively. Carbapenem-resistant E. coli was first detected in 2014; its overall resistance rate to carbapenem was 5.3%. There was a linear correlation between the usage of 3rd generation cephalosporin and the resistance of A. baumannii (r²=0.96, P=0.004) and carbapenem usage and the resistance of K. pneumoniae (r²=0.79, P=0.045). Conclusions: A positive linear correlation was observed between antibiotic resistance and the corresponding antibiotic usage in 3rd generation cephalosporin resistant A. baumannii and carbapenem resistant K. pneumoniae. The judicious use of antibiotics in healthcare settings is important to minimize selection for extended-spectrum β-lactamase (ESBL) and carbapenem resistance in gram-negative bacteria.

• Pediatric Infection and Vaccine
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• v.9 no.2
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• pp.163-174
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• 2002

Background : To delineate the changes in the causative agents of neonatal sepsis and their antimicrobial susceptibilities in the neonatal intensive care unit and nursery of Hanyang University Hospital during the past 10 years. Methods : Hospital records of 15,144 patients hospitalized at the NICU and nursery of Hanyang University Hospital from 1989 to 1998 were reviewed and neonates diagnosed of neonatal sepsis were sorted and included in the study. The study period was divided into Period A(the first 5 years) and Period B(the second 5 years) to analyse causative agents and their antimicrobial susceptibilities. Results : Neonatal sepsis was diagnosed in 170 patients(1.1%{Period A 1.2%, Period B 1.0%}) among the total of 15,144 inpatients. Two hundred isolates(Period A 109 isolates, Period B 91 isolates) were identified in 186 blood cultures(Period A 99 cultures, Period B 87 cultures) from 170 patients(Period A 91 patients, Period B 79 patients). The average age at the onset of the disease, when the initial blood culture was drawn, was 12.3 days old(Period A 8.8 days, Period B 16.3 days), and the proportion of the early onset disease was 34.7% in Period A and 23.0% in Period B, indicating that neonatal sepsis developed earlier during Period A. Among the isolated organisms including Gram positive bacteria[132(66.0%)], Gram negative bacteria [60(30.0%)], and fungi[8(4.0%)], coagulase negative Staphylococcus(CNS) was the most common organism(69/34.5%), followed by Staphylococcus aureus(36/18.0%), Klebsiella pneumoniae(17/8.5%), Enterococcus(12/6.0%), Enterobacter cloacae(8/4.0%), Escherichia coli(6/3.0%), and Pseudomonas aeruginosae(5/2.5%). The isolated fungi were Candida parapsilosis, Candida albicans, and Trichosporon pullulans. CNS, S. aureus and Acinetobacter baumannii were isolated more frequently in Period A compared to Period B. Antimicrobial susceptibilities of CNS and S. aureus to methicillin and the first generation cephalo sporins were decreased in Period B compare to Period A, those to aminoglycosides were increased in Period B, and vancomycin resistant strains were not identified. K. pneumoniae, Enterococcus, E. coli, and P. aeruginosa were isolated less frequently in Period B, compared to Period A. For K. pneumoniae, antimicrobial susceptibilities to the first generation cephalosporins were low in both Periods A and B, those to tobramycin and gentamicin were increased in Period B, and those to amikacin, ceftriaxone, and trimethoprim-sulfamethoxazole were high in both Periods A and B. Antimicrobial susceptibilities of Enterococcous to ampicillin, penicillin, and the first generation cephalosporins were decreased in Period B, but vancomycin resistant strains were not identified. Conclusion : The occurrence rate of neonatal sepsis during the past 10 years in the NICU and nursery of the Hanyang University hospital was 1.1%, and the most common causitive agents were CNS and S. aureus, to which the antimicrobial susceptibilities to the first line drugs decreased in the later half of the study period with no vancomycin resistant isolates identified. Group B Streptococcus known to be the most common agent causing neonatal sepsis was not identified, and K. pneumoniae was isolated more commonly during the later half of the study period without decreased antimicrobial susceptibilities.

• Pediatric Infection and Vaccine
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• v.12 no.2
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• pp.157-165
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• 2005

Purpose : Children occupy a large proportion of burn victims. So we want to aid to pediatric burn care through the understanding of the bacterial distribution in burn wounds and antibiotic susceptibility against isolated microorganisms from burn wounds. Methods : We analysed the medical records of 213 pediatric burn patients(0~15 years), 406 samples that grew bacteria in burn wound sites. Results : Of the total 213 patients, male were 59.6% and female were 40.4%. Scalding burn was the most common(78.4%), flame burn was the second(16.4%). Pathogens were isolated in 406 samples. The most common was Pseudomonas aeruginosa(58.1%). Next were Enterococcus species, Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus species, Acinetobacter species. P. aeruginosa was resistant to trimethoprim-sulfamethoxazole in 100%, cephalothin in 98.1%, ampicillin-sulbactam in 96.2%, ampicillin in 95.3%, ceftriaxone in 95.2%, tobramycin in 93.7%, cefoperazone in 68.9%, ceftazidime in 67.7%. Enterococcus species were resistant to tetracycline in 63.9%, streptomycin in 45.5%, gentamicin in 36.1%, penicillin G in 13.7%. S. aureus was resistant to gentamicin in 89.7%, tetracycline in 86.2%, ciprofloxacin in 86.2%, penicillin G in 84.3%, oxacillin in 78.4%, erythromycin in 76.5%. Acinetobacter species were resistant to ampicillin-sulbactam in 100%, gentamicin in 85.7%, ampicillin in 83.3%, piperacillin in 61.5%. Conclusion : P. aeruginosa was highly resistant to drugs like cefoperazone in 68.9%, ceftazidime 67.7%. S. aureus was highly resistant to penicillin G in 84.3%, oxacillin in 25.9 %, but none to vancomycin in 0%, teicoplanin in 2.2%. According to the study, Acinetobacter species turned out to be multi-resistant strains, so careful attention must be paid to the choice of antibiotics.

• Pediatric Infection and Vaccine
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• v.27 no.1
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• pp.35-44
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• 2020

Purpose: This study aimed to investigate the clinical features of recurrent urinary tract infection (UTI) in children with vesicoureteral reflux (VUR) and to compare the causative uropathogen and antibiotic susceptibility between the first and recurrent UTI episodes. Methods: We retrospectively reviewed the medical records of children with VUR who had recurrent UTI. Group 1 included patients in whom the same pathogen caused the first and recurrent UTI episodes. Group 2 included patients in whom different pathogens caused the first and recurrent UTI episodes. Results: During a 13-year study period (2005-2018), 77 children with VUR experienced at least one episode of UTI. Among these, 47 patients (61.0%) had recurrent UTI. Of the children with recurrent UTI, 19 (40.4%) were in group 1 and 28 (59.6%) were in group 2. Escherichia coli was the most commonly isolated uropathogen (n=37; 39.4%) in both episodes of recurrent UTIs, followed by Klebsiella pneumoniae (n=18; 19.1%), Enterococcus faecalis (n=14; 14.9%), and Enterobacter aerogenes (n=7; 7.4%). Although the difference was not significant, the rate of resistance to the antibiotics ceftazidime, piperacillin/tazobactam, and trimethoprim-sulfamethoxazole increased in patients with the second episode of E. coli recurrence in group 1, and that to cefotaxime, ceftazidime, piperacillin/tazobactam, and meropenem increased in children with the second episode of E. aerogenes recurrence in group 1. Conclusions: When selecting empirical antibiotics for recurrent UTI in children with VUR, it is important to consider that the pathogen and antimicrobial susceptibility of the previous UTI are not always the same in recurrent UTIs.

• Pediatric Infection and Vaccine
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• v.12 no.1
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• pp.67-74
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• 2005

Purpose : The incidence of mortality associated with respiratory difficulties is decreasing nowadays contributed to the development of neonatology. However, complications associated with mechanical ventilator are increasing. This study is to determine clinical manifestations, diagnositc availability of the endotracheal tip culture in patients with Ventilator-Associated Pneumonia(VAP) in neonatal intensive care unit(NICU). Methods : A retrospective analysis of 50 neonates who were admitted to the NICU of Kangnam Sacred Heart Hospital and had given mechanical ventilator from 1 January 2000 to 30 June 2003. VAP group defined as neonates who had pneumonia with mechanical ventilation longer than 48 hours. They were classified into VAP group(n=13) and control group (n=37) and the prevalence, microorganisms cultured from the endotracheal tube tip and risk factors were investigated. Results : The prevalence of VAP was 26.0%(n=13) and the most dominant microorganism cultured in our NICU was methicillin-resistant coagulase negative staphylococcus(MR-CNS) in 4 cases. Other microorganisms were Pseudomonas, Enterobacter, methicillin-resistant Staphylococcus aureus(MRSA) and Klebsiella. Gestational age, birth weight, Apgar score, respiratory distress syndrome, retinopathy of prematurity, bronchopulmonary dysplasia, sepsis, renal failure, pulmonary hemorrhage, pneumothorax were not different significantly between two groups except intraventricular hemorrhage(P<0.001) and patent ductus arteriosus(P<0.05). Duration of hospital stay and mortality rate were also not different significantly. Conclusion : VAP occurred at a significant rate among mechanically ventilated NICU patients. Despite of limitation of encotracheal tip culture, the most common microorganism was MR-CNS. We should be aware of occurrence of VAP in NICU neonate who were with mechanical ventilator and should treat with great care.