• Clinical and Experimental Pediatrics
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• v.50 no.1
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• pp.56-64
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• 2007

Purpose : This study was performed to identify the etiologic agents and antimicrobial susceptibility patterns of organisms responsible for bloodstream infections in pediatric cancer patients for guidance in empiric antimicrobial therapy. Methods : One hundred and ninety-seven episodes of bloodstream infections that developed in 128 pediatric cancer patients were analyzed, which were identified at the Seoul National University Children's Hospital during a 4 year-period from 2002 to 2005. Results : A total of 214 pathogens was isolated, of which 64.0 percent were gram-negative, 31.3 percent were gram-positive bacteria, and 4.7 percent were fungi. The most common pathogens were Klebsiella spp. (21 percent) and Escherichia coli (16.8 percent), and coagulase-negative staphylococci (CNS, 7.9 percent) and viridans streptococci (7.5 percent) emerged as important pathogens. Neutropenic patients were more often associated with gram-negative bacteria than non-neutropenic patients (67.5 percent vs. 51.1%, P=0.018) and patients with central venous catheters were more often associated with CNS and viridans streptococci than those without. Resistance rates of gram-positive bacteria to penicillin, oxacillin and vancomycin were 83.3 percent, 48.5 percent and 0.5 percent, respectively, and those of gram-negative bacteria to cefotaxime, piperacillin/tazobactam, imipenem, gentamicin and amikacin were 24.1 percent, 17.2 percent, 6.6 percent, 21.6 percent, and 14.2 percent, respectively. Gram-negative bacteremias were more often associated with intensive care than gram-positive bacteremias (26.5 percent vs. 10.3 percent, P=0.016), and patients with catheters were more often associated with intensive care (34.4 percent vs. 10.8 percent, P<0.001) and higher fatality rate (16.7 percent vs. 4.8 percent, P=0.012) than those without. Conclusion : This study revealed that gram-negative bacteria are still a dominant organism in bloodstream infections, especially in neutropenic patients, and confirmed that gram-positive bacteria are emerging as important etiological agents in bloodstream infections of pediatric hemato-oncologic patients.

• Biomedical Science Letters
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• v.1 no.1
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• pp.55-72
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• 1995

Forty gentamicin-resistant isolates of Enterococcus faecalis were selected from various clinical materials, determined their antimicrobial susceptibility, and studied there R-plasmid characteristics and polypeptide patterns. All of the isolates were susceptible to vancomycin. The MICs($\mu$/ml) of antimicrobial agents to the isolates were as follows; the MIC of gentamicin was 128 and $\geq$2040, ampicillin 1 and 1, chlorarmphenicol 2 and 8, erythromycin 32 and 256, and vancomycin 1 and 2. E. faecalis HL-1 strain had 8 plasmid DNA elements, HL-2 and HL-3 strains had 6, HL-4 had 7, HL-5 had 4, and HL-6 had 5. The 51.7 Kb of gentamicin resistance plasmid DNA was conjugally transferred from two strains of E. faecalis HL-1 and HL-6 to S. aureus SK 982. The plasmid transfer frequency between S. aureus SK 982 and E. faecalis HL-1 or E. faecalis HL-6 was 6.3$\times10^{-4} and 3.7$\times10^{-5}$, respectively. Plasmid curing ratio after the treatment of ethidium bromide(10$\mu$/ml) to E. faecalis tarnsconjugants R-1 and R-6 were about 51% and 67%, respectively. The tetracycline gene was located in 2.15 Kb plasmid of E. faecalis HL-1, but it was not found in the E. faecalis HL-6 by Southern blot analyses. The antigenic components of E. faecalis HL-1, HL-6, R-1 and R-6 strains were analyzed by SDS-PAGE and immunoblotting. The E. faecalis strains had 7 to 16 polypeptide bands, however their major proteins were 97.8 and 26.8 Kd. At the Immunoblotting, 97.8, 95.8, 74.8, 63.5, 33.7 and 26.8 Kd polypeptides of the strains showed major antigenic activities with patient's sera infected intra-abdominally with an E. faecalis strain.

• Pediatric Infection and Vaccine
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• v.18 no.1
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• pp.31-39
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• 2011

Purpose : This study was performed for the purpose of finding causative organisms and clinical features of septic arthritis or acute osteomyelitis in children. Methods : The study involved a retrospective review of the medical records of 63 microbiologically confirmed cases of acute pyogenic arthritis and osteomyelitis. All of the cases were brought about by community-associated infections and managed at the Seoul National University Children's Hospital or Seoul National University Bundang Hospital from June 2003 to July 2009. Results : The median age of all cases was 60 months and there were 35 males and 28 females. Major involved joints included the hip joint (15 cases), knee joint (7 cases), shoulder joint (4 cases), and elbow joint (4 cases). Also, major involved bones included the femur (20 cases), tibia (13 cases), humerus (7 cases), and radius (7 cases). Staphylococcus aureus was the most commonly identified causative organism, accounting for 49 cases (77.8%). Of the 49 isolates of S. aureus, methicillin-resistant S. aureus (MRSA) accounted for 8 cases (16.3%). Group B streptococcus spp. (GBS) and Salmonella spp. accounted for 3 cases, respectively. Nafcillin or cefazolin was often prescribed as an initial empirical antibiotic. There were 9 cases that were managed by a regimen that included vancomycin as the first choice. Fifty four cases (85.7%) recovered without any complications. Methicillin-sensitive S. aureus (MSSA), responsible for 41 cases, caused chronic complications in 3 cases. Of 8 cases caused by MRSA, 1 case showed chronic complication. There were no fatal cases. Conclusion : S. aureus remains the most common organism causing acute pyogenic arthritis and osteomyelitis of childhood acquired in the community. The high prevalence of methicillin resistance among S. aureus should be considered carefully in the selection of initial empirical antibiotics.

• Clinical and Experimental Pediatrics
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• v.48 no.6
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• pp.619-623
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• 2005

Purpose : Bacteremia in immunocompromised pediatric cancer patients can lead to high morbidity and mortality, if not treated early and properly. The incidence and antibiotic sensitivities to common pathogens of bacteremia in pediatric cancer patients are liable to change, according to region and time. We investigated the causative organisms and antibiotic sensitivities of bacteremia in pediatric cancer patients to assess the adequacy of empiric antimicrobial therapy. Methods : From September 1995 to August 2003, we retrospectively evaluated 58 episodes in 39 pediatric cancer patients with bacteremia treated at the Pediatric Department of Yeungnam University Hospital. We investigated and analyzed the causative organisms and the antibiotic sensitivity test results by reviewing the records of the microbiologically proven positive blood culture results. Results : The incidence of bacteremia in pediatric cancer patients in this study was 5.7 percent (58 episodes out of 1,022 occasions of blood cultures). Gram-positive organisms were isolated more often than gram-negative organisms (63.8 percent vs 36.2 percent) in the following order : Staphylococcus epidermidis (37.9 percent), Staphylococcus aureus (17.3 percent), Escherichia coli (12 percent), Streptococcus (8.6 percent), Enterobacter (6.9 percent), Klesiella (6.9 percent), Serratia (3.5 percent), Acinetobacter (3.5 percent), Proteus (1.7 percent) and Morganella morganii (1.7 percent). In antibiotic sensitivity tests, only six of 37 isolates (16 percent) of gram positive bacteria were sensitive to penicillin and 15 of 37 isolates (40 percent) were sensitive to oxacillin. All except one Staphylococcus aureus were sensitive to vancomycin and all except one Staphylococcus epidermidis were sensitive to teicoplanin among 37 isolates of gram positive bacteria. In the case of gram negative bacteria, two of 21 isolates (10 percent) and four of 21 isolates (19 percent) were sensitive to cefotaxime and ceftazidime, respectively. Only six of 21 isolates (29 percent) were sensitive to aminoglycoside, but all 21 isolates (100 percent) were sensitive to imipenem. All seven isolates tested after the year 2000 were sensitive to meropenem. Conclusion : In conclusion, we should choose the proper antimicrobials in treating pediatric cancer patients with suspected bacteremia, reflecting the increasing episodes of gram positive bacteremia and polymicrobial resistance of gram positive and negative organisms.

• Korean Journal of Food Science and Technology
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• v.37 no.1
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• pp.134-141
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• 2005

To characterize genotypic and phenotypic traits of Staphylococcus aureus isolates (n = 86) from lettuces and raw milk, major virulence-associated genes and antibiotic susceptibility were detected using PCR-based methods and disk diffusion method, respectively. All isolates possessed coagulase gene and showed five polymorphism types [500 bp (2.4%), 580 bp (17.4%), 660 bp (61.6%), 740 bp (17.4%), and 820 bp (1.2%)] due to variable numbers of tandem repeats present within the gene. Two or three different loci of hemolysin gene family were dominant in isolates, 47 of which (55%) possessed combination of hla/hld/hlg-2 genes as the most prevalent types. Among enterotoxin-encoding genes, sea was detected from 32 isolates (37%), sed from 1 isolate (1%), and sea and sed genes were co-detected from 4 isolates (5%), whereas seb, sec, and tsst-1 genes were not detected. All isolates were susceptible to ciprofloxacin, trimethoprim/sulfamethoxazole, oxacillin, and vancomycin, 85 isolates (99%) to penicillin G, 54 isolates (63%) to chloramphenicol, 51 isolates (59%) to erythromycin, and 7 isolates (8%) to clindamycin. Among resistant isolates, seven displayed multiantibiotic-resistance against two different antibiotics.

• Journal of Life Science
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• v.18 no.8
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• pp.1083-1089
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• 2008

We investigated the molecular epidemiological characteristic of methicillin resistant Staphylococcus aureus (MRSA) strains isolated from stool samples in Busan from 2004 to 2006. Among 142 isolates of S. aureus, 49 isolates (34.5%) were confirmed as MRSA. With the antimicrobial susceptibility tests, 37 isolates (75.5%) showed multiple resistance to more than 10 antibiotics, but all isolates were sensitive to vancomycin. All of MRSA had enterotoxin A in 30.6%, B 4.1%, C 8.3%, D, C/G, A 2.0% and None 51%. PFGE of SmaI-digested chromosomal DNA was performed on 49 sporadic MRSA isolates. Restriction fragment patterns consisted of 8 to 14 fragments ranged in size from 48.5 to 630.5 kbp. We could divided the isolates into 7 groups ($I{\sim}VII$) by analyzing PFGE patterns. Group I subdivided as 2 subgroups and 17 (34.7%) strains belong to the group I. Dendrogram of PFGE patterns showed that MRSA strains in Busan were heterogeneous but we could find out minor homogeneity in hospital.

• Korean Journal of Clinical Laboratory Science
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• v.49 no.4
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• pp.420-426
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• 2017

Methicillin-resistant Staphylococcus (MRS) can be colonized in various body sites and is more frequently isolated in healthcare associated persons. This study aimed to evaluate the contamination rate of MRS in a high school environment, those living with closed life style. Staphylococcus aureus was isolated from only the hands of 2 students among a sample of 28 students, and S. aureus were susceptible to methicillin antibiotics. Coagulase negative Staphylococci (CoNS) were isolated from the hands of 26 students (26/28, 92.9%), and among them, 14 (53.8%) isolates were methicillin-resistant CoNS (MRCoNS). Among the 14 MRCoNS, S. warneri was the most common (8/14, 57%) and susceptible to most $non-{\beta}-lactam$ antibiotics, such as clindamycin, erythromycin, ciprofloxacin, tetracycline, gentamicin, and vancomycin. In a culture of 31 desks, S. aureus was not isolated but CoNS were isolated from 26 desks (26/31, 83.6%), which did not harbor the mecA gene. The other bacteria isolated from the hands and desks were Micrococcus and Bacillus spp. In conclusion, methicillin-resistant S. aureus was not isolated from the hands and desks of high school students. However, the frequency of MRCoNS harboring mecA gene were high in the hands of high school students. Therefore, to prevent and to control the transfer of infection, intensifying preventive education, such as hand washing, and active surveillance systems, such as an investigation of contamination or carrier rate of resistant bacteria are necessary.

• Journal of Korean Medicine Rehabilitation
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• v.25 no.2
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• pp.1-13
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• 2015

Objectives Methicillin-Resistant Staphylococcus aureus (MRSA) is a human pathogen and a major cause of hospital-acquired infections. New antibacterial agents that have not been compromised by bacterial resistance are needed to treat MRSA-related infections. In this study, we investigated the antimicrobial activity ofethanol extract of Haedokgeumhwa-san (HGH) which prescription is composed of korean medicine against MRSA. Methods The antibacterial activity of HGH extract was evaluated against MRSA strains by using the Disc diffusion method, broth microdilution method (minimal inhibitory concentration; MIC), checkerboard dilution test, and time-kill test; its mechanism of action was investigated by bacteriolysis, detergent or ATPase inhibitors. The checkerboard dilution test was used to examined synergistic effect of ampicillin, oxacillin, ciprofloxacin, vancomycin, gentamicin and norfloxacin in combination with HGH ethanol extract. A time-kill assay was performed a survival curve which was obtained by plotting viable colony counts depending on time on bacterial growth. Results The minimum inhibitory concentration (MIC) of ethanol extract (HGH) ranged from 1,000 to $2,000{\mu}g/mL$ against all the tested bacterial strains, respectively. We are able to confirm that HGH extract has potentially strong antibacterial activity. In the checkerboard dilution test, fractional inhibitory concentration index of HGH in combination with antibiotics indicated synergy or partial synergism against S. aureus. A time-kill study showed that the growth of the tested bacteria was considerably inhibited after 8 hr of treatment with the combination of HGH with selected antibiotics. For measurement of cell membrane permeability, HGH $250{\sim}1,000{\mu}g/mL$ along with concentration of Triton X-100 (TX) and Tris-(hydroxymethyl) aminomethane (Tris) were used. In the other hand, N,N-dicyclohexylcarbodimide (DCCD) and Sodium azide ($NaN_3$) was used as an inhibitor of ATPase. TX, Tris, DCCD and $NaN_3$ cooperation against S. aureus showed synergistic action. Accordingly, antimicrobial activity of HGH was affected by cell membrane and inhibitor of ATPase. Conclusions These results suggest that Haedokgeumhwa-san extract has antibacterial activity, and that HGH extract offers a potential as a natural antibiotic against MRSA.

• Journal of Food Hygiene and Safety
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• v.37 no.1
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• pp.21-28
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• 2022

In this study, a new lactic acid bacterium (LAB) that could produce gamma-aminobutyric acid (GABA) was isolated from Oenanthe javanica (water celery) and identified as an Enteroccoccus casseliflavus strain. Until recently, there have been many studies on the gamma-aminobutyric acid producing lactic acid bacterium, as well as on some lactic acid bacterium in Enteroococcs genus, but none on the species E. casseliflavus. Therefore, in the purpose of finding the optimal conditions for GABA production of E. casseliflavus PL05, the effects of several conditions including the type of mediums, growth temperatures, initial pH, growth time, L-mono sodium glutamate (MSG) concentration, and carbon source were tested. The study revealed that the PL05 strain grew better in the Brain Heart Infusion (BHI) medium than in the Man, Rogosa, and Sharpe (MRS) or Tryptic Soy Broth (TSB) medium. Also, similar results were obtained with GABA production conditions. As a result of analysis on the GABA production yield by concentration of MSG, a GABA substrate, the highest production was found at 7% of MSG concentration. However, since similar level of production was found at 5%, it is considered to be more efficient to use 5% MSG concentration. The analysis on the growth and GABA production yield by carbon sources showed the highest results when maltose was used. From the final test under the optimal conditions found, 140.06±0.71 mM of GABA was produced over 24 hours with the conversion rate of 78.95%. Lastly, from the sensitivity analysis on the 10 different antibiotics, including vancomycin, it was found that there were not confirmed cases of resistance.

• Pediatric Infection and Vaccine
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• v.19 no.3
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• pp.131-140
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• 2012

Purpose : This study was performed to identify the etiologic agents and antimicrobial susceptibility patterns of organisms responsible for bloodstream infections in pediatric cancer patients for guidance in empiric antimicrobial therapy. Methods : A 5-year retrospective study of pediatric hemato-oncologic patients with bacteremia in Seoul National University Children's Hospital, from 2006 to 2010 was conducted. Results : A total of 246 pathogens were isolated, of which 63.4% (n=156) were gram-negative, bacteria 34.6% (n=85) were gram-positive bacteria, and 2.0% (n=5) were fungi. The most common pathogens were Klebsiella spp. (n=61, 24.8%) followed by Escherichia coli (n=31, 12.6%), coagulase-negative staphylococci (n=23, 9.3%), and Staphylococcus aureus (n=22, 8.9 %). Resistance rates of gram-positive bacteria to penicillin, oxacillin, and vancomycin were 85.7%, 65.9%, and 9.5%, respectively. Resistance rates of gram-negative bacteria to cefotaxime, piperacillin/tazobactam, imipenem, gentamicin, and amikacin were 37.2%, 17.1%, 6.2%, 32.2%, and 13.7%, respectively. Overall fatality rate was 12.7%. Gram-negative bacteremia was more often associated with shock (48.4% vs. 11.9%, P<0.01) and had higher fatality rate than gram-positive bacteremia (12.1% vs. 3.0%, P=0.03). Neutropenic patients were more often associated with shock than non-neutropenic patients (39.6 % vs. 22.0%, P=0.04). Conclusion : This study revealed that gram-negative bacteria were still dominant organisms of bloodstream infections in children with hemato-oncologic diseases, and patients with gram-negative bacteremia showed fatal course more frequently than those with gram-positive bacteremia.