Kim, Tae-jong;Kim, Jong-bae;Lee, Seong-bae;Jeon, Young-soo
Korean Journal of Veterinary Research
/
v.29
no.3
/
pp.393-405
/
1989
This study was carried out to treatment test for bovine mastitis by the determination of adenosine triphosphate (ATP) based on firefly bioluminescence. The results obtained are followed; 1. In the susceptibility test, cephalothin which looks the most effective were sensitive to Staphylococcus sp. (72.3%), Micrococcus sp. (84.2%), Streptococcus sp. (72.7%) and Gram positive bacilli (72.7%), Gram negative bacilli were sensitive to gentamicin (92.3%) and Yeast-like-fungi was the most sensitive to clotrimazole, and nystatin in order. 2. When the number of bacteria, such as Staphylococcus aureus, Candida tropicalis isolated from the mastitis milk were counted by conventional agar plating technique, and compared with the concentration of bacterial ATP, it gave a good linear relationship. The content of ATP per Staphylococcus aureus, cell was 3.1fM and Candida tropicalis showed the high level of A TP (90fM). 3. The ATP assay was applied to the determination of minimal inhibitory concentration (MIC) of various antibiotics. When Staphylococcus aureus was incubated in the presence of different concentration of tetracycline, erythromycin, kanamycin and streptomycin sulfate and the growth was monitored by the conventional agar plating technique and ATP assay, both methods shown the same results that they were 1mcg/ml, 2mcg/ml, 6.25mcg/ml and 8mcg/ml, respectively. 4. For the determination of susceptibility of sensitive and resistant Staphylococcus au reus isolated for the milk with mastitis to tetracycline, erythromycin kanamycin and streptomycin sulfate, the minimum time required for the test was determined by the assay of ATP every 30 minutes during incubation of 3 hours at $37^{\circ}C$. ATP concentration time curve calculated on both resistant and sensitive strains incubated 3 hours as the optimum time for the determination of susceptibilities of various antibiotics exemed. The ATP concentration of each test broth (antibiotic containing), expressed as a percentage of its own control brith (antibioticfree) indicated values of 30% to be indicative of each antibiotic sensitivity. Single time point ATP assay carried out on the various sensitive and resistant of Staphylococcus aureus to antibiotics examined after 3 hours at $37^{\circ}C$ correlated exactly with disc diffusion and MIC. 5. In the cure of intramammary treatment of bovine mastitis in lactating quarters, the cure rate of Staphylococcal mastitis showed to cephalexin (80%), cloxacillin and gentamicin (70%), ampicillin and oxytetracycline (60%), and Streptococcal mastitis showed to cephalexin (85%), penicillin (80%), cloxacillin and oxytetracycline (75%), and ampicillin (70%), but intramammary antimycotic drug (clotrimazol) were only a little effect about fungal mastitis.
Objectives : The purpose of our study was to evaluate penicillin as a still drug of choice for severe endodontic infection, by analyzing the antimicrobial susceptibilities from endodontic infections with swelling to figure out appropriate antibiotics as empirical treatment. Materials and methods : This study involved 18 patients who attended for emergency treatment because of facial or periapical swelling associated with root canal infections. Identification and antimicrobial susceptibility test of each pathogen were performed by Vitek2 Systems (bioM$\acute{e}$rieux, Marcy l'Etoile, France). Results : The most frequent bacteria was Streptococcus spp.(77%), and the resistance against penicillin was 35% in overall patients, followed by clindamycin and erythromycin (17%), which was much higher than previous studies. Conclusions : In our study, the higher resistance made penicillin alone not to be chosen as the first antibiotic drug for severe endodontic infections. Combinations with other drug, penicillin with wider spectrum of activity, or changing to other antibiotics was considered while remembering the increased risk of resistant microorganism.
Characteristics of the food isolates and the clinical specimens isolates of E. coli harboring virulence factor and their correlations were analyzed. The predominant serogroup were 08 and 027 in the food isolates and 06 and 018 in the clinical isolates, respectively, showing the different patterns in serogrouping between them. In the test of antibiotic susceptibility, the food isolates were resistant to cephalothin, streptomycin, tetracycline and minocycline, and the clinical isolates were resistant to ampicillin, carbenicillin, streptomycin, cephalothin, trimethoprim/sulfamethoxazole, tetracyclino and minocycline, respectively. It shows that E.coli isolated from food sources and clinical specimens might be correlated. Plasmid profile in the food and clinical isolates showed wide diversity. Especially, large sized plasmid DNA such as 60 MDa, 90 MDa and 120 MDa were observed. The plasmid DNA (60 MDa) containing a gene encoding hemolysin was found in 43% of the food isolates and 35% of the clinical isolates. To study chromosomal homology, PFGE analysis was performed, showing different restriction patterns by Xbal. This result indicates that there were no genetic correlations between the foods and the clinical isolates.
As a part of investigation for listeriosis, we attmepted iolationof Listeria spp. from commerical frozen and refrigerated foods at the supermarket level. Seven strains of Listeria spp. were isolate from 6 samples (7.15) among 84 samples of frozen foods, and ten strains of Listeria spp. were also isolated from 8 samples (7.6%)_ among 105 samples of refrigerated foods at the supermarkets in Pusan area. From a total of 189 commerical foods, the number of isolated Listeria spp. and ratio were 6 strains(3.25) of L. grayi, one strain (0.5%) of L. welshimeri, 6 strains (3.2%) of L. innocua and 4 strains (2.15) of L monocytogenes. Listeria spp. isolates except L. monocytogenes did not show $\beta$-hemolysis on blood agar and positive reaction in CAMP test with Staphyloccccus aureus. In the antibiotic susceptibility,most isolates of Listeria spp. were susceptible to 12 antibiotics such as ampicillin , cephalotin, penicillin, amikacin, gentamicin, erythromycin, kanamycin, vancomycin, tobramycin, carbenicillin , tetracycline and trimethoprim /sulfamethoxiazole. Four strains of L. monocytogenes were susceptible to ntibiotics used in this study except nitrofurantio. The serotype of 3 strains and one strain of L. monocytogenes were classified into Listeria O serotype 1 and 4, respectively.
Objectives: Cefotaxime is an antibiotic used to treat several bacterial infections. Specifically, it is used to treat pelvic inflammatory disease, meningitis, pneumonia, urinary tract infections, and sepsis. It is given by injection into either a vein or muscle. Antibacterial polymers prepared by chemical bonding and simple blending of antibacterials into polymers has attracted much interest because of their long-lasting antibacterial activity. This study attempted to review the possibility of hydrogel films as functional antibacterial materials by antimicrobial activity. Methods: In this study, CTX-PAA was synthesized by the chemical reaction of polyacrylic acid with cefotaxime by N,N'-Dicyclohexylcarbodiimide (DCC) method. Synthetic antibacterial hydrogel films were then prepared with PVA and CTX-PAA for functional application. Results: The increase in the cefotaxime content of the hydrogel films showed a similar decrease in tensile strength and elongation. The values of films impregnated with chemically bonded cefotaxime showed no significant difference. Antibacterial susceptibility was determined against Streptococcus pneumoniae and Escherichia coli using a standardized disc test. Conclusion: The synthetic antibacterial hydrogel films exhibited broad susceptibility against Streptococcus pneumoniae and Escherichia coli. Notably, the antibacterial effect of antibacterial hydrogel films against Grampositive (Streptococcus pneumoniae) was superior to that against Gram-negative (Escherichia coli).
The present study was carried out to investigate the prevalence of brucellosis in Kyungbuk area for the 3 years from 1966 to 1998. Collective milk samples were routinely screened to detect positive farms by using the milk ring test(MRT), and serum agglutination test was performed to detect sero-positive individuals in the MRT positive farms. Attempt were made to isolate the causative organismas from slaughtered sero-positive reactors and some biochemical and polymerase chain reation characters of the isolates were also made to identify the organisms. Seroprevalence to brucellosis in peoples who are close contact with infected dairy herds was also investigated. Brucellosis of dairy cattle was rare before 1997, but has been broken more frequently since early 1998. By the MRT for dairy herds, positive rate was gradually increased every year : 0.6% in 1996, 1.5% in 1997, 3.9% in 1998. Among 262 MRT-positive herds, only 21 herds(8.0%) showed positive brucellosis in serological test. The isolation rates of Brucella sp from tested materials were 51.2% in supramammary glands, 39.5% in milks, and 50.0% in pulmonary Iymphnode, respectively. Isolated strain and biotype were Brucella(B) arbortus biotype 1 in 26 heads, and were B suis biotype 1 in 2 heads. Isolated strain and vaccine strain were very similar in their colony morphology and staining. In drug susceptibility, isolated stains(B abortus) and vaccine strain(B abortus RB-51) were sensitive to ampicillin, gentamycin, kanamycin, neomycin, penicillin, streptomycin, and to tetracycline, but resistant to erythromycin. In the PCR, field strains reacted to BA and IS711 primers, and vaccine strain reacted to BA, IS711, and RB5l primers. In the plate agglutination test of 96 sera of human contacted with animals, serum antibody titer detected 1 : 100 in one person, 1 : 200 in one, and below 1 : 25 in the others.
The policies developed for the treatment of Helicobacter pylori infection in adults may not be the most suitable ones to treat children and adolescents. Methods used to treat children and adolescents in Europe and North America may not be appropriate for treating children and adolescents in Korea due to differences in epidemiological characteristics of H. pylori between regions. Moreover, the agreed standard guidelines for the treatment of H. pylori infection in children and adolescents in Korea have not been established yet. In this study, the optimal treatment strategy for H. pylori infection control in children and adolescents in Korea is discussed based on these guidelines, and recent progress on the use and misuse of antimicrobial agents is elaborated. Non-invasive as well as invasive diagnostic test and treatment strategy for H. pylori infection are not recommendable in children aged less than ten years or children with body weight under 35 kg, except in cases of clinically suspected or endoscopically identified peptic ulcers. The uncertainty, whether enough antimicrobial concentrations to eradicate H. pylori can be maintained when administered according to body weight-based dosing, and the costs and adverse effects outweighing the anticipated benefits of treatment make it difficult to decide to eradicate H. pylori in a positive noninvasive diagnostic test in this age group. However, adolescents over ten years of age or with a bodyweight of more than 35 kg can be managed aggressively as adults, because they can tolerate the adult doses of anti-H. pylori therapy. In adolescents, the prevention of future peptic ulcers and gastric cancers is expected after the eradication of H. pylori. Bismuth-based quadruple therapy (bismuth-proton pump inhibitor-amoxicillin/tetracycline-metronidazole) with maximal tolerable doses and optimal dose intervals of 14 days is recommended, because in Korea, the antibiotic susceptibility test for H. pylori is not performed at the initial diagnostic evaluation. If the first-line treatment fails, concomitant therapy plus bismuth can be attempted for 14 days as an empirical rescue therapy. Finally, the salvage therapy, if needed, must be administered after the H. pylori antibiotic susceptibility test.
Background: The efficacy of standard treatment of Helicobacter pylori (H. pylori) is declining because of antibiotic resistance. Clarithromycin resistance is also increasing in many Asian countries. The aim of this study was to determine the antibiotic susceptibility patterns of H. pylori infection and clinical association in Laos. Materials and Methods: A total of 329 Lao dyspeptic patients who underwent gastroscopy at Mahosot Hospital, Vientiane, Laos during December 2010-March 2012 were enrolled in this study. During gastroscopy, 4 biopsies were collected (2 each from the antrum and body) for CLO-test and histopathology. Only the positive CLO-test gastric tissues was stored at $-80^{\circ}C$ in a freezer until DNA was extracted and a GenoType$^{(R)}$HelicoDR test was conducted for detecting mutations in the rrl gene encoding 23S rRNA (clarithromycin resistance) and mutations in gyrA gene (fluoroquinolone resistance). Results: Of the total, 119 Lao patients (36.2%) were infected with H. pylori including 59 males (49.6%) and 60 females (50.4%) with a mean age of 46 years. Clarithromycin and fluoroquinolone resistance of H. pylori infection was demonstrated in 15 (12.6%) and 16 strains (13.4%) respectively. In clarithromycin resistance, the number of patients who had education above primary school and $BMI{\geq}25kg/m^2$ were significantly higher than those who had education below primary school and BMI<$25kg/m^2$ (23.1% vs 7.5%, P-value= 0.036 and 20.5% vs 8%, P-value= 0.048, respectively). In fluoroquinolone resistance, the number of lowland Lao was significantly higher than those of non-lowland (highland and midland) Lao ethnic groups (16.7% vs 0%, P-value= 0.039). Conclusions: H. pylori infections remain common in Laos. Clarithromycin and fluoroquinolone resistance with H. pylori infection are growing problems. Education above primary school and $BMI{\geq}25kg/m^2$ might be predictors for clarithromycin resistance and lowland Lao ethnicity might be predictors for fluoroquinolone resistance with H. pylori infection in Laos.
Staphylococcus aureus is a major cause of nosocomial infections and is one of the most commonly isolated bacterial species in the hospital and continues to be an important pathogen in both community and hospital-acquired infection. Methicillin resistant S. aureus (MRSA), which is associated with hospitals is now being isolated in the community. The purpose of this study is to investigate the carrier rate of S. aureus in the community, antibiotic resistance patterns of the organism, detection of MRSA and mecA gene in MRSA. Ninety strains $(46.4\%)$ of S. aureus were isolated from the nasal specimens of 194 elementary school students. Eighty-nine strains $(98.9\%)$ of 90 S. aureus were resistant to penicilin, 36 strains $(40.0\%)$ to erythromycin, 14 strains $(15.6\%)$ to fusidic acid, 11 strains $(12.2\%)$ to gentamycin, 9 strains $(10.0\%)$ to tobramycin, 5 strains $(5.6\%)$ to oxacillin, 4 strains $(4.4\%)$ to clindamycin, 2 strains $(2.2\%)$ to tetracycline, 1 strains $(1.1\%)$ to fosfomycin. None of $90(0\%)$ S. aureus isolates was resistant to ciprpfloxacin, trimethoprim/sulfamethoxazole, levofloxacin, linezolid, moxifloxacin, nitrofurantoin, norfloxacin, rifampicin, quinupristin/dalfopristin, teicoplanin, and vancomycin. Five strains $(5.6\%)$ of 90 S. aureus isolates were MRSA. The mecA gene was detected from five MRSA strains by PCR.
Journal of the Korean Society of Food Science and Nutrition
/
v.37
no.4
/
pp.528-533
/
2008
Staphylococcus aureus is a pathogene of major concern in livestock products. This study was conducted to test imported and domestic meat sold by retail stores for the presence S. aureus. In addition, the antibiotic susceptibility of any S. aureus found was also evaluated. The overall isolation rate of S. aureus was 20.2% (13.9% in pork and 33.8% in beef) in retail meats. The percentage of imported meats found to contain S. aureus (33.3% in pork and 40.4% in beef) was higher than that of domestic meat (13.0% in pork and 14.7% in beef). In addition, the detection rate of S. aureus was higher in raw material meat than in ready to cook packaged meat. When the antibiotic susceptibility of S. aureus isolated from the meat products was evaluated, ampicillin was found to be the highest (76.5%), followed by penicillin (75.3%), tetracycline (27.1%) and erythromycin (21.2%). Penicillin and tetracycline resistant were detected in 55.6% and 13.3% of the beef isolates, respectively, and 97.5% and 42.5% of the pork isolates, respectively. The tetracycline and erythromycin resistant plasmids of the isolated strain were transferred into S. aureus DPRMM2429 by the filter mating method and the frequencies of transfer was found to be $1.1{\times}10^{-5}{\sim}1.9{\times}10^{-9}$ and $1.2{\times}10^{-5}{\sim}4.0{\times}10^{-8}$ respectively.
본 웹사이트에 게시된 이메일 주소가 전자우편 수집 프로그램이나
그 밖의 기술적 장치를 이용하여 무단으로 수집되는 것을 거부하며,
이를 위반시 정보통신망법에 의해 형사 처벌됨을 유념하시기 바랍니다.
[게시일 2004년 10월 1일]
이용약관
제 1 장 총칙
제 1 조 (목적)
이 이용약관은 KoreaScience 홈페이지(이하 “당 사이트”)에서 제공하는 인터넷 서비스(이하 '서비스')의 가입조건 및 이용에 관한 제반 사항과 기타 필요한 사항을 구체적으로 규정함을 목적으로 합니다.
제 2 조 (용어의 정의)
① "이용자"라 함은 당 사이트에 접속하여 이 약관에 따라 당 사이트가 제공하는 서비스를 받는 회원 및 비회원을
말합니다.
② "회원"이라 함은 서비스를 이용하기 위하여 당 사이트에 개인정보를 제공하여 아이디(ID)와 비밀번호를 부여
받은 자를 말합니다.
③ "회원 아이디(ID)"라 함은 회원의 식별 및 서비스 이용을 위하여 자신이 선정한 문자 및 숫자의 조합을
말합니다.
④ "비밀번호(패스워드)"라 함은 회원이 자신의 비밀보호를 위하여 선정한 문자 및 숫자의 조합을 말합니다.
제 3 조 (이용약관의 효력 및 변경)
① 이 약관은 당 사이트에 게시하거나 기타의 방법으로 회원에게 공지함으로써 효력이 발생합니다.
② 당 사이트는 이 약관을 개정할 경우에 적용일자 및 개정사유를 명시하여 현행 약관과 함께 당 사이트의
초기화면에 그 적용일자 7일 이전부터 적용일자 전일까지 공지합니다. 다만, 회원에게 불리하게 약관내용을
변경하는 경우에는 최소한 30일 이상의 사전 유예기간을 두고 공지합니다. 이 경우 당 사이트는 개정 전
내용과 개정 후 내용을 명확하게 비교하여 이용자가 알기 쉽도록 표시합니다.
제 4 조(약관 외 준칙)
① 이 약관은 당 사이트가 제공하는 서비스에 관한 이용안내와 함께 적용됩니다.
② 이 약관에 명시되지 아니한 사항은 관계법령의 규정이 적용됩니다.
제 2 장 이용계약의 체결
제 5 조 (이용계약의 성립 등)
① 이용계약은 이용고객이 당 사이트가 정한 약관에 「동의합니다」를 선택하고, 당 사이트가 정한
온라인신청양식을 작성하여 서비스 이용을 신청한 후, 당 사이트가 이를 승낙함으로써 성립합니다.
② 제1항의 승낙은 당 사이트가 제공하는 과학기술정보검색, 맞춤정보, 서지정보 등 다른 서비스의 이용승낙을
포함합니다.
제 6 조 (회원가입)
서비스를 이용하고자 하는 고객은 당 사이트에서 정한 회원가입양식에 개인정보를 기재하여 가입을 하여야 합니다.
제 7 조 (개인정보의 보호 및 사용)
당 사이트는 관계법령이 정하는 바에 따라 회원 등록정보를 포함한 회원의 개인정보를 보호하기 위해 노력합니다. 회원 개인정보의 보호 및 사용에 대해서는 관련법령 및 당 사이트의 개인정보 보호정책이 적용됩니다.
제 8 조 (이용 신청의 승낙과 제한)
① 당 사이트는 제6조의 규정에 의한 이용신청고객에 대하여 서비스 이용을 승낙합니다.
② 당 사이트는 아래사항에 해당하는 경우에 대해서 승낙하지 아니 합니다.
- 이용계약 신청서의 내용을 허위로 기재한 경우
- 기타 규정한 제반사항을 위반하며 신청하는 경우
제 9 조 (회원 ID 부여 및 변경 등)
① 당 사이트는 이용고객에 대하여 약관에 정하는 바에 따라 자신이 선정한 회원 ID를 부여합니다.
② 회원 ID는 원칙적으로 변경이 불가하며 부득이한 사유로 인하여 변경 하고자 하는 경우에는 해당 ID를
해지하고 재가입해야 합니다.
③ 기타 회원 개인정보 관리 및 변경 등에 관한 사항은 서비스별 안내에 정하는 바에 의합니다.
제 3 장 계약 당사자의 의무
제 10 조 (KISTI의 의무)
① 당 사이트는 이용고객이 희망한 서비스 제공 개시일에 특별한 사정이 없는 한 서비스를 이용할 수 있도록
하여야 합니다.
② 당 사이트는 개인정보 보호를 위해 보안시스템을 구축하며 개인정보 보호정책을 공시하고 준수합니다.
③ 당 사이트는 회원으로부터 제기되는 의견이나 불만이 정당하다고 객관적으로 인정될 경우에는 적절한 절차를
거쳐 즉시 처리하여야 합니다. 다만, 즉시 처리가 곤란한 경우는 회원에게 그 사유와 처리일정을 통보하여야
합니다.
제 11 조 (회원의 의무)
① 이용자는 회원가입 신청 또는 회원정보 변경 시 실명으로 모든 사항을 사실에 근거하여 작성하여야 하며,
허위 또는 타인의 정보를 등록할 경우 일체의 권리를 주장할 수 없습니다.
② 당 사이트가 관계법령 및 개인정보 보호정책에 의거하여 그 책임을 지는 경우를 제외하고 회원에게 부여된
ID의 비밀번호 관리소홀, 부정사용에 의하여 발생하는 모든 결과에 대한 책임은 회원에게 있습니다.
③ 회원은 당 사이트 및 제 3자의 지적 재산권을 침해해서는 안 됩니다.
제 4 장 서비스의 이용
제 12 조 (서비스 이용 시간)
① 서비스 이용은 당 사이트의 업무상 또는 기술상 특별한 지장이 없는 한 연중무휴, 1일 24시간 운영을
원칙으로 합니다. 단, 당 사이트는 시스템 정기점검, 증설 및 교체를 위해 당 사이트가 정한 날이나 시간에
서비스를 일시 중단할 수 있으며, 예정되어 있는 작업으로 인한 서비스 일시중단은 당 사이트 홈페이지를
통해 사전에 공지합니다.
② 당 사이트는 서비스를 특정범위로 분할하여 각 범위별로 이용가능시간을 별도로 지정할 수 있습니다. 다만
이 경우 그 내용을 공지합니다.
제 13 조 (홈페이지 저작권)
① NDSL에서 제공하는 모든 저작물의 저작권은 원저작자에게 있으며, KISTI는 복제/배포/전송권을 확보하고
있습니다.
② NDSL에서 제공하는 콘텐츠를 상업적 및 기타 영리목적으로 복제/배포/전송할 경우 사전에 KISTI의 허락을
받아야 합니다.
③ NDSL에서 제공하는 콘텐츠를 보도, 비평, 교육, 연구 등을 위하여 정당한 범위 안에서 공정한 관행에
합치되게 인용할 수 있습니다.
④ NDSL에서 제공하는 콘텐츠를 무단 복제, 전송, 배포 기타 저작권법에 위반되는 방법으로 이용할 경우
저작권법 제136조에 따라 5년 이하의 징역 또는 5천만 원 이하의 벌금에 처해질 수 있습니다.
제 14 조 (유료서비스)
① 당 사이트 및 협력기관이 정한 유료서비스(원문복사 등)는 별도로 정해진 바에 따르며, 변경사항은 시행 전에
당 사이트 홈페이지를 통하여 회원에게 공지합니다.
② 유료서비스를 이용하려는 회원은 정해진 요금체계에 따라 요금을 납부해야 합니다.
제 5 장 계약 해지 및 이용 제한
제 15 조 (계약 해지)
회원이 이용계약을 해지하고자 하는 때에는 [가입해지] 메뉴를 이용해 직접 해지해야 합니다.
제 16 조 (서비스 이용제한)
① 당 사이트는 회원이 서비스 이용내용에 있어서 본 약관 제 11조 내용을 위반하거나, 다음 각 호에 해당하는
경우 서비스 이용을 제한할 수 있습니다.
- 2년 이상 서비스를 이용한 적이 없는 경우
- 기타 정상적인 서비스 운영에 방해가 될 경우
② 상기 이용제한 규정에 따라 서비스를 이용하는 회원에게 서비스 이용에 대하여 별도 공지 없이 서비스 이용의
일시정지, 이용계약 해지 할 수 있습니다.
제 17 조 (전자우편주소 수집 금지)
회원은 전자우편주소 추출기 등을 이용하여 전자우편주소를 수집 또는 제3자에게 제공할 수 없습니다.
제 6 장 손해배상 및 기타사항
제 18 조 (손해배상)
당 사이트는 무료로 제공되는 서비스와 관련하여 회원에게 어떠한 손해가 발생하더라도 당 사이트가 고의 또는 과실로 인한 손해발생을 제외하고는 이에 대하여 책임을 부담하지 아니합니다.
제 19 조 (관할 법원)
서비스 이용으로 발생한 분쟁에 대해 소송이 제기되는 경우 민사 소송법상의 관할 법원에 제기합니다.
[부 칙]
1. (시행일) 이 약관은 2016년 9월 5일부터 적용되며, 종전 약관은 본 약관으로 대체되며, 개정된 약관의 적용일 이전 가입자도 개정된 약관의 적용을 받습니다.