• The Korean Journal of Pesticide Science
• /
• v.14 no.4
• /
• pp.427-432
• /
• 2010

Rice bakanae disease caused by Fusarium fujikuroi is one of the most serious rice diseases in Korea. From 2006 to 2009, 118 F. fujikuroi isolates were collected from various regions of rice fields in Korea. Resistance assay of 118 F. fujikuroi isolates to prochloraz, tebuconazole, and benomyl, were performed using agar dilution method. To investigate inhibitory effects of the fungicides, minimum inhibitory concentration of mycelial growth (MIC) and effective concentration inhibiting mycelial growth by 50% ($EC_{50}$) for 118 isolates were calculated using Sigmaplot 8.02 (Antro, SPSS UK, Ltd). Based on the means of $EC_{50}$ values, baseline resistance values were determined as $0.5{\mu}g{\cdot}mL^{-1}$ for prochloraz, $5.0{\mu}g{\cdot}mL^{-1}$ for tebuconazole and $2.5{\mu}g{\cdot}mL^{-1}$ for benomyl. Number of resistant isolates to each fungicide was 17, 19 and 43 for prochloraz, tebuconazole and benomyl, respectively. Furthermore, 4 isolates showed the double resistance to both prochloraz and tebuconazole, 6 isolates to prochloraz and benomyl, and 11 isolates to tebuconazole and benomyl. Isolates CF366 and LF335 isolated from Gyeongbuk province were resistant to the three fungicides tested, prochloraz, tebuconazole and benomyl.

• Journal of Life Science
• /
• v.15 no.3 s.70
• /
• pp.479-485
• /
• 2005

The 994 throat swabs obtained from 688 adults and 306 children patients with respiratory diseases were examined for Mycoplasma pneumoniae infection by culture method. Antimicrobial susceptibilities of the resulting 123 M. pneumoniae isolates were evaluated by testing minimum inhibitory concentrations (MICs) of erythromycin, minocycline, tetracycline, josamycin, sparfloxacin, ofloxacin, and ciprofloxacin by a broth micro-dilution method. The erythromycin resistant strains of M. pneumoniae was determined above $1.0{\mu}g/ml$ of MIC for erythromycin. The erythromycin resistant strains of M. pneumoniae was confirmed resistant gene mutation of the portions of genes 23S rRNA (domain II and V), and ribosomal protein 14 and L22 by PCR amplified and their nucleotide sequenses were compared to those of the susceptible strain M129. The isolation rate of M. pneumoniae was $12.9\%$ (89/688) for the adults and $11.1\%$ (34/306) for the children. The $MICs_{90}$ of the M. pneumoniae isolates were $0.12{\mu}g/ml$ for minocycline, $0.25{\mu}g/ml$ for sparfloxacin, $0.5{\mu}g/ml$ for ciprofloxacin, ofloxacin, and tetracycline, respectively, and $2.0{\mu}g/ml$ for josamycin and erythromycin, respectively. The isolation rate of erythromycin resistant M. pneumoniae from patients was $49.4\%\;(44/89)$ for the adults, $47.1\%\;(16/34)$ for children, and $48.8\%\;(60/123)$ for the total. No mutation could be detected in the ribosomal protein L22 region, but all strains were mutated in the ribosomal protein L4 as two point mutation M144V. Two point mutations in domain V of 23S rRNA were selected in the presense of erythromycin resistant M. pneumoniae isolates, such as one strain was G2057C mutant, two strains were A2059C mutants, three strains were C2611G mutants, four strains were A2058C mutants, five strains were A2058T mutants, twenty strains were A2059G mutants, and twenty-five strains were A2058G mutants, respectively. These results show that erythromycin was not the most active compound against M. pneumoniae infection in Korea and clinical studies of macrolides in human patients are demanded.

• Journal of fish pathology
• /
• v.9 no.2
• /
• pp.185-193
• /
• 1996

Extensive acquirement of drug resistance to traditional antibacterial agents poses a serious problem to eel aquaculturists. To collect the basic information for new drug development in the future, we assessed the in vitro antibacterial efficacy of 14 new quinolones with 75 isolates of Edwardsiella tarda from local aquaculture tanks of Anguilla japonica. Of all tested quinolones under development or marketed for human use, DU-6859 was most potent with its $MIC_{50}$ value of $0.05{\mu}g$/ml in broth microdilution assay. The drugs whose $MIC_{50}$ values ranged from 0.2 to $0.78{\mu}g$/ml were T-3762, Bay-y3118, ciprofloxacin, norfloxacin, ofloxcin and tosufloxacin. The weakest group of drugs, with their $MIC_{50}$ being 1.56-$3.13{\mu}g$/ml, were difloxacin, sparfloxacin, fleroxacin, Q-35, amifloxacin, lomefloxacin and enoxacin. The number of resistant strains, when arbitrarily defined with their MICs of $\geq6.25{\mu}g$/ml, was : 3 to T-3762, 3 to Bay-y3118, 44 to difloxacin, 16 to sparfloxacin, 13 to ciprofloxacin, 19 to fleroxacin, 36 to Q-35). 31 to amifloxacin, 5 to norfloxacin, 13 to ofloxacin, 31 to lomefloxacin, 41 to enoxacin, 12 to tosufloxacin and 0% to DU-6859, respectively. This information can be taken into consideration for the future development of fisheries antibacterial quinolones.

• Korean Journal of Microbiology
• /
• v.42 no.3
• /
• pp.185-194
• /
• 2006

The aim of this study was to identify the bacteria isolated from endodontic lesions by cell culture and to determine the antimicrobial susceptibility of them against 8 antibiotics. The necrotic pulpal tissues were collected from 27 infected root canals, which were diagnosed as endodontic infection. Samples were collected aseptically from the infected pulpal tissue of the infected root canals using a barbed broach and a paper point. The cut barbed broaches and paper points were transferred to an eppendorf tube containing $500{\mu}l\;of\;1{\times}PBS$. The sample solution was briefly mixed and plated onto a BHI-agar plate containing 5% sheep blood. The agar plates were incubated in a $37^{\circ}C$ anaerobic chamber for 2 to 5 days. The bacteria grown on the agar plates were identified by comparison of 16S rRNA gene (rDNA) sequencing method at the species level. To test the sensitivity of the bacteria isolated from the infected root canals against 8 antibiotics, minimum inhibitory concentrations (MIC) were determined using broth dilution assay. The data showed that 101 bacterial strains were isolated and were identified. Streptococcus spp. (29.7%) and Actinomyces spp. (21.8%) were predominantly isolated. The 9 strains were excluded in antimicrobial susceptibility test because they were lost during the experiment or were not grown in broth culture. The percentage of bacteria susceptible for each antibiotic in this study was clindamycin, 87.0% (80 of 92); tetracycline, 75.0% (69 of 92); cefuroxime axetil, 75.0% (69 of 92); amoxicillin + clavulanic acid (5:1), 71.7% (66 of 92); penicillin G, 66.3% (61 of 92); erythromycin, 66.3% (61 of 92); amoxicillin, 44.6% (41 of 92); and ciprofloxacin, 31.5% (29 of 92). The susceptibility pattern of 8 antibiotics was dependent on the host of the bacteria strains rather than the kinds of bacterial species. These results indicate that antibiotic susceptibility test should be performed when antibiotics are needed for the treatment of infected root canals.

• Pediatric Infection and Vaccine
• /
• v.9 no.1
• /
• pp.79-84
• /
• 2002

Purpose : About 41% of obtained group A streptococci in the 1998 was reported as erythromycin-resistant streptococci in Seoul, Korea. The most common T serotype was T12, followed by T4 and T28. We'd like to monitor the serological changes and antibiotic sensitivity test of Streptococcus pyogenes obtained from the patients with pharyngotonsillitis and invasive diseases from 1999 through 2001. Also, it could be proposed to choose the proper antibiotic selection in the area where the rate of erythromycin-resistant streptococci is high. Methods : From Jan. 1999 to Oct. 2001, 208 isolates of group A streptococci were collected from inpatients and outpatients with pharyngotonsillitis, scarlet fever, and invasive infections in Seoul and Southern part of peninsula. All isolates were serotyped by T-agglutination, minimum inhibitory concentrations(MICs) which were determined by agar dilution methods, according to the guidelines of the National Committee for Clinical Laboratory Standards (NCCLS). Results : The most common T serotype was T12(29.8%), followed by T1(23.1%), T4 (14.9%). T1 was prominent serotype compared with previous year. T serotyping, among 25 isolates obtained from the patients with scarlet fever in Southern part of peninsula mostly, was T12, T1, and T4 in order of frequency. All the isolates tested were susceptible to penicillin, cefprozil, vancomycin, ceftriaxone, and chloramphenicol. However, 23 isolates(14.2%) was resistant to erythromycin and 18 isolates(11.1%) was resistant to clarithromycin. Serotype T12 was found to be the most resistant serotype to erythromycin and/or clarithromycin. Conclusion : High rate of erythromycin-resistant streptococci which surveyed in 1998 were reduced to 14.2% in this study. We should have to further evaluate the reason of decreased resistant strains and consider the resistant strains of streptococci in choosing the antibiotics. There was no serological characteristics according to the types of disease entities. Between the serologic distributions in Seoul and the Southern part of peninsula area are same, we could presume that the serological typing of strains obtained over the country may be not different.