• The Journal of the Korean Society for Microbiology
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• v.21 no.3
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• pp.381-385
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• 1986

Twenty strains of penicillin(PC)-resistant Staphylococcus aureus ($MIC{\geqq}32U/ml$) were chosen randomly from recent isolates and submitted to the present experiment to see what effect the combined antibiotic action of moxalactam(MX) and fosfomycin(FM) would bring about on the cells, using MS-2 system. 1. The conventional agar dilution method and the rapid automatic MS-2 system were used in measuring the MICs of MX and FM against each strain and the comparison of the data obtained revealed no significant difference between the two methods in the titer and distribution of the MICs. 2. The automatic MS-2 system was, therefore, used alone in determining the combined growth inhibitory effect of MX and FM because of its more rapidness, and the obtained results were that most of the PC-resistant strains(16 out of 20, 80%) were synergistically inhibited by the two antibiotic combination while additive effect was observed in the remaining 4 strains(20%). 3. Thus, it is suggested that the growth of PC-resistant staphylococcal cells may be synergistically inhibited by MX and FM combination and the efficiency of two antibiotic action as well as MIC of single antibiotic may be more rapidly determined by the MS-2 system than by the conventional method.

• Journal of Life Science
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• v.10 no.3
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• pp.262-272
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• 2000

As a part of investigation for basic epidemiology of diarrheogenic disease, we attempted isolation of Escherichia coli from patients with diarrhea. Seven hundred and twenty-one strains of E. coli were isolated from 1,239 patients with diarrhea. Seasonal distribution of patient with diarrhea was shown the most high at August (18.2%). Age group distribution of patient was shown the most high at children (54.6%, 2 to 10 years old). The serotypes of 721 E. coli isolates were in order of serotype O44 (16.8%), O153 (8.6%), O1 (7.5%), O166(5.7%), O8 and O86a (4.7%), and O125 (4.6%). The supernates cultured 36 strains among 721 E. coli isolates were indicated cytotoxicity against monolayered Vero cells. All of the isolates were susceptible to amikacin. The isolates were resistant in order of novobiocin (99.0%), moxalactam (97.1%), carbenicillin (96.1%), tetracycline (90.4%), ampicillin (85.9%), gentamicin (84.0%), streptomycin (78.4%), cephalothin (46.6%) and polymyxin B (4.2%). In the antibiotic resistant patterns, 125 kinds of multiple resistance patterns of E. coli isolates were detected. The highest resistant pattern was ampicillin-carbenicillin-chloramphenicol-cephalothin-erythro-mycin- gentamicin-moxalactam-novobiocin-penicillin G-streptomycin-tobramycin-tetracycline-tri methoprim type (24.3%).

• The Journal of the Korean Society for Microbiology
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• v.21 no.3
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• pp.375-380
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• 1986

Thirty-one strains of Pseudomonas aeruginosa were submitted to the synergistic activity test of amikacin(AK) and gentamicin(GM) combined with moxalactam(MX), ceftizoxime(CTZ) or cefoperazone(CFZ). The minimal inhibitory concentrations(MICs) of each drug and drugs combined in various ratios were measured by checkerboard dilution method. The synergism was determined through analysing the MIC distribution curve on isobologram and calculating the fractional inhibitory concentration index(FICI). MICs of GM, AK, MX, CFZ and CTZ against the 31 tested strains were distributed from $12.5{\mu}g/ml$ to $800{\mu}g/ml$, from $0.8{\mu}g/ml$ to $25{\mu}g/ml$, from $3.1{\mu}g/ml$ to $50{\mu}g/ml$, from $3.1{\mu}g/ml$ to $400{\mu}g/ml$, and from $12.5{\mu}g/ml$ to $100{\mu}g/ml$, respectively. The rate synergism of each drug combination by means of FICl was 45.5% in GM-MX, 36.4% in GM-CFZ, 63.6% in GM-CTZ, 48.6% in AK-MX, 35.3% in AK-CFZ, and 35.7% in AK-CTZ combination. Thus, it is suggested that Pseudomonas aeruginosa may effectively be inhibited by various aminoglycoside and cephalosporin combinations.

• The Journal of the Korean Society for Microbiology
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• v.22 no.3
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• pp.251-258
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• 1987

A total of 58 strains of Enterobacter species isolated from clinical specimens at Kyungpook National University Hospital in Taegu and Yonsei University Hospital in Seoul were tested for the molecular characterization to investigate the nosocomial infection through the study of R plasmids which might spread among Gram negative organisms regardless of their originated strains. All strains resistant to ampicillin, cefoxitin and cephalothin but susceptible to moxalactam were subjected to the further test for the determination of in detail MIC value against 23 drugs of common use including beta-lactam antibiotics and R plasmid profile analysis. The reistance frequency of strains against carbenicillin (53.4%) was similar to those against chloramphenicol, tobramycin, and sulfisomidine. Though the MIC values of resistance criteria against ceftazidime, aztreonam, imipenem, and norfloxacine in NCCLS manual were not available but MIC ranges of strains tested were very low. There were differences in patterns and frequencies of resistance between the strains isolated in Seoul and Taegu isolates. Seoul isolates showed a tendency of higher multiplicity of resistance than those of Taegu isolates. The resistances against cefoxitin, cephalothin, cefoperazone, cefotaxime, nalidixic acid, and rifampin were not conferred to the conjugally transferable R plasmid. The approximate molecular size of conjugally transferable R plasmids ranged 30 to 151 megadalton, and one or 2 to 3 R plasmids were identified in each transconjugants.

• The Journal of the Korean Society for Microbiology
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• v.22 no.3
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• pp.241-250
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• 1987

A total 64 strains of Escherichia coli including 38 strains of urinary tract infection and 26 strains from other clincal sources were studied for several properties related to the virulence markers of organisms. Urinary isolates(76.3%) showed higher frequency of mannose resistant hemagglutination(MRHA) wi th human erythrocytes(A type, $Rh^+$) than the strains of control group isolated from other sources(34.6%). Seventeen strains(44.4%) of urinary isolates and 2 strains(7.7%) of control group showed hemolysis on blood agar plate. There was no significant difference in MIC's of 23 drugs between both groups of urinary isolates and control group. But they showed high frequency of resistance to ampicillin, carbenicillin, piperacillin, kanamycin, and trimethoprim, but were very susceptible to cefotaxime, moxalactam, ceftizidime, imipenem, and norfloxacine. Fourteen strains(36.8%) of urinary isolates and 10 strains(38.5%) of control group showed conjugally transferable resistance conferred to R plasmids. The urinary isolates carried one or more to 6(mean 3.4) plasmids of approximate molecular weight ranged 3.1 to 94 megadalton(Mdal) and strains of control group carried 2 to 5(mean 3.8) plasm ids of size ranged 3.6 to 130 Mdal. The size of conjugally transferable R plasmid identified with transconjugants ranged 32 to 130 Mdal.

• The Journal of the Korean Society for Microbiology
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• v.21 no.1
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• pp.1-16
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• 1986

Fifty-one strains of Pseudomonas aeruginosa were isolated from various clinical specimens. Among them, 26 (51%) strains were gentamicin-resistant (Gm') and 25 (49%) were susceptible to gentamicin (Gm'). The frequencies of resistant strains to piperacillin (Pi), cefotaxime, moxalactam, cefoperazone (Cz), and amikacin (Ak) ranged from 21.6 to 31.4%, and $MIC_{50}$ of these drugs were lower than the critical concentrations of susceptibility and resistance. Thirty (58.8%) strains were multiply resistant to 12 or more drugs. All Gm' strains were multiply resistant to 12 or more drugs and one was resistant to all 18 drugs tested, while only four Gm' strains were multiply resistant to 12 drugs and the multiplicity of resistance of the other Gm' strains were less than 10 drugs. Resistance to Gm appeared to have a significant correlation with the resistance to tobramycin (Tb), Ak, Pi, and Cz. All Gm' strains were resistant to Tb and about 38.4 to 46.1% of them were resistant to Ak, Pi, and Cz. The incorporation of $Ca^{++}$ and $Mg^{++}$ ions in Mueller-Hinton agar (MHA) did not influence the MICs of Gm, Tb, carbenicillin (Cb), Pi, and Cz as compared with the results obtained in MHA without these ions. Gm strains were studied on the combined effect of beta-lactam antibiotics and aminoglycosides by the methods of checkerboard and modified paper strip diffusion. Most Gm' strains showed significant synergistic effects by the FIC index between Ak and three beta-lactam antibiotics; Cb, Pi, and Cz, but these results did not in agreement the results obtained through the method of modified paper strip diffusion test. In order to know the nature of the drug resistance of P. aernginosa, the plasmid profile analysis was studied. Agarose gel electrophoresis of lysates processed by the method of Kado and Liu showed one or more plasmids in 22 (43.1%) strains. A group of 19 strains showed at least one band of plasmid and three strains two bands. The range of the molecular weight of plasmids was 3.8 to 243 Mdal. All strains carrying large plasmids larger than 200 Mdal were isolated from wound specimens. Three Gm' strains also harboured the plasm ids of 13 to 203 Mdal.

• The Journal of the Korean Society for Microbiology
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• v.22 no.3
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• pp.283-294
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• 1987

One hundred and fifty-seven strains of staphylococci isolated from various clinical specimens and 80 of Gram-negative bacilli from urine of patients with urological diseases were tested for resistance to antimicrobial drugs by microdilution broth method. Among staphylococci, 50 to 89% of the strains were resistant to gentamicin(Gm), kanamycin(Km), erythromycin(Em), nalidixic acid(Na), and tetracycline. Ninety per cent MIC was lowest in ciprofloxacin(Cp), followed by vancomycin(Vc), trimethoprim(Tp), enoxacin(Ex), and norfloxacin(Nf) with the values of two ${\mu}g/ml$ or lower. Twenty-seven strains were resistant to methicillin(MR), with 24 strains of Staphylococcus aureus and 3 of S. epidermidis. All strains of MR S. aureus were resistant to oxacillin, rifampin(Rf), Gm, Km, Em, Na, and Tc, and no strain was resistant to Vc and Tp. Almost all staphylococci isolated from urine were S. epidermidis and sensitive to most drugs tested without MR strain. Among Gram-negative bacilli from urine, Escherichia coli(43 strains) was most frequently isolated, and followed by Klebsiella spp.(11), Proteus spp.(10), Serratia spp.(10), and Pseudomonas aeruginosa(6) in the decreasing order. The majority of E. coli and Serratia spp. were resistant to chloramphenicol(Cm), Tc, streptomycin, sulfisomidine(Su), ampicillin(Ap), Km, and carbenicillin(Cb), and 50 and 90% MICs of these drugs were also high. In Klebsiella spp., 54% or more were resistant to Cm, Su, Ap, cephalothin, and Cb. Proteus spp. were susceptible to most drugs tested, but Pseudomonas were resistant to nearly all drugs tested except Rf, amikacin, and moxalactam(Mx). All Gram-negative bacilli tested were found to be susceptible to Mx. New quinolone carboxylic acid compounds, such as Nf, Ex, and Cp showed very high antimicrobial activities against the majority of organisms tested except Pseudomonas, and 50 and 90% MICs of Nf and Ex were always equal or 2 to 4 times higher than Cp. Organisms multiply resistant to drugs were noted in almost all isolates tested. Twenty-seven strains of staphylococci were multiply resistant to 11 or more drugs, and 6 of Klebsiella spp. to 8 to 11 drugs. The most frequent multiplicity of durg resistance were 7 and 8, 12, and 13 in E. coli, Serratia spp., and Pseudomonas, respectively. No strain was resistant to more than 5 drugs in Proteus spp..