• Journal of Life Science
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• v.28 no.12
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• pp.1529-1535
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• 2018

The number of antibiotic-resistant bacteria is increasing rapidly while the discovery rate of new antibiotics is in decline. A systematic study is therefore necessary to investigate which bacteria are resistant to medically important antibiotics and how high that resistance is. To that end, this study aimed to analyze which bacteria demonstrated resistance to ampicillin, one of the currently most-widely used medical antibiotics. Water samples were collected from the Changwon-Cheon that runs through Changwon City and from the pond in front of the dormitory building at Changwon University. Hundreds of ampicillin-resistant colonies were obtained and 22 morphologically distinct examples were chosen for further study. These bacteria were identified by amplifying their 16S rRNA genes and comparing those sequences with data in GenBank. The bacteria was identified as belonging to 10 families, 12 genera, and 17 species, and all were able to grow in the presence of $50{\mu}g/ml$ ampicillin while seven showed growth at ampicillin concentrations as high as 1.5 mg/ml.

• Microbiology and Biotechnology Letters
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• v.50 no.1
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• pp.89-94
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• 2022

Triclosan (TCS) is an antimicrobial agent used in various human personal care products against both gram-positive and gram-negative bacteria. The purpose of this study was to evaluate the presence of TCS-resistant bacteria in sewage water in Peshawar, Khyber Pakhtunkhwa (KPK), Pakistan, for the first time. TCS-supplemented Luria Bertani (LB) agar was used to isolate TCS-tolerant bacteria. A total of 17 TCS-resistant isolates were randomly selected from a large pool of bacteria that showed growth on TCS-supplemented LB agar. Based on gram staining and physiochemical characteristics, the isolated strains were identified as Salmonella typhi (n = 6), Escherichia coli (n = 4), Citrobacter freundii (n = 4), Proteus mirabilis (n = 1), Enterobacter cloacae (n = 1), and Pseudomonas aeruginosa (n = 1). The Triclosan mean minimum inhibitory concentrations (MICs) for the isolates of Salmonella typhi, Escherichia coli, Citrobacter freundii, Proteus mirabilis, Enterobacter cloacae, and Pseudomonas aeruginosa were 23.66 ㎍ ml^-1, 18.75 ㎍ ml^-1, 42 ㎍ ml^-1, 32 ㎍ ml^-1, 64 ㎍ ml^-1, and 128 ㎍ ml^-1, respectively. The antibiogram revealed that all isolates were resistant to penicillin G (100%) and linezolid (100%), followed by ampicillin (94%), tetracycline (76%), tazobactam (76%), sulbactam/cefoperazone (64%), polymyxin PB (58%), amikacin (29.41%), aztreonam (29.41%), imipenem (5%), and gentamicin (5%). This is the first known study regarding the isolation of TCS-tolerant bacteria from sewage water in Peshawar, KPK, Pakistan. It was concluded that all the TCS-resistant isolates were multidrug resistant (MDR) gram-negative rod-shaped bacteria, mostly belonging to the Enterobacteriaceae family.

• Journal of agricultural medicine and community health
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• v.30 no.2
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• pp.137-149
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• 2005

Objectives and Methods: This study was performed to investigate the etiologic bacterial, viral and protozoal organisms for the diarrhea from hospitals in Chungnam area from January to December in 2004. Total of 787 fecal samples were collected and examined. Results and Conclusions: In test for enteropathogenic bacteria, total of 79 cases out of 787 samples from hospitals showed positive isolation. Among 79 positive samples, 27 cases were confirmed as Salmonella spp.. 20 cases as pathogenic E. coli, 18 cases as Clostridium perfringens, 6 cases as Staphylococcus aureus, 4 cases as Shigella spp. and 4 cases as Vibrio parahaemolyticus. In test for enteropathogenic virus, 190 cases out of 787 samples from hospitals showed positive reaction. Among 190 samples, 115 cases were confirmed as rotavirus, 55 cases as norovirus, 5 case as astrovirus, 4 case as rotavirus & norovirus, 3 cases as adenovirus, 2 case as rotavirus & astrovirus. In test for enteropathogenic protozoa, 6 cases out of 787 samples from hospitals showed positive result. Among 6 samples, 5 cases were confirmed as Entamoeba histolytica and 1 cases as Giardia lamblia. When we classified the positive results by the age of the patients, the highest isolation rate was noted in a group of age under 10 and over 60 for bacterial, viral and protozoal pathogens. Especially, patient below age of 5 showed high positive rate. When we classified the positive results by the time, pageathogenic bacteria were isolated throughout the year, and the highest frequency was noted in August. On the other hand, pathogenic viruses were detected more frequently during the colder season from December to April. Antimicrobial susceptibility test for the isolated bacteria resulted as follows; Salmonella strains showed high drug resistance rates against ampicillin, chloramphenicol, tetracycline, nalidixic acid, ticarcillin. Shigella strains showed high drug resistance rates against ampicillin, trimethoprim/sulfamethoxazole, chloramphenicol, tetracycline, ampicillin/sulbactam, ticarcillin. Pathogenic E. coli strains showed high drug resistance rates against ampicillin, cephalothin, gentamicin, tetracycline, nalidixic acid, ampicillin/sulbactam, ticarcillin.

• Journal of Veterinary Clinics
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• v.21 no.1
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• pp.7-14
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• 2004

Bacteria that are resistant to several different groups of antibiotics have increased during the past few years. The importance of surveillance of antimicrobial resistance is now widely recognized. Unfortunately, this development has not been documented continuously in veterinary medicine in Korea. Therefore, the clinical prevalence and trend of antimicrobial susceptibility of aerobic isolates were investigated in this study. Total 121 isolates of aerobic bacteria were isolated from clinical specimens of dogs and cats at Veterinary Medical Teaching Hospital of Seoul National University from May 2001 to October 2002. Among them, the most common isolated species was Staphylococcus spp. (48 isolates), followed by E.coli (26 isolates), Enterococcus spp. (21 isolates), Klebsiella pneumoniae (9 isolates), Streptococcus spp. (6 isolates), Enterobacter cloacae (3 isolates), Pseudomonas aeruginosa (3 isolates), Corynebacterium xerosis (2 isolates), Chryseomonas spp. (2 isolates), and Providencia stuartii (1 isolate). The susceptibility of isolates to antibiotics was determined by the disk diffusion method. Gram-positive bacterial isolates were showed high susceptibilities to amikacin, amoxacillin/clavulanate, ceftazidime, and oxacillin, while Gram-negative bacterial isolates were showed high susceptibilities to amikacin and ceftazidime. Staphylococcus spp. were showed high susceptibilities to amikacin, amoxicillin/clavulanate, ceftazidime, cephalothin, and oxacillin. Streptococcus spp. and E.coli were showed high susceptibilities to amikacin and ceftazidime. Of the 48 staphylococci, seven Methicillin Resistant staphylococci were observed (14.6%), distributed among S. auricularis (1), S. hemolyticus (2), S. sciuri (1), S. saprophyticus (1), S. warneri (2) isolates. One strain of E.coli and one strain of Corynebacterium xerosis were resistant to all antibiotics tested. And, resistance trends between the you 2000 (from July 1999 to September 2000) and 2002 (from May 2001 to October 2002) were compared. Resistance to antibiotics was increased in both Gram-positive and Gram-negative bacterial isolates (p＜ 0.05). The resistance rates of Staphylococcus spp., E.coli and Klebsiella pneumoniae to all antibiotics tested were also increased (p＜0.05). This study investigated increasing resistance between the year 2000 and 2002 in Veterinary Medical Teaching Hospital of Seoul National University. Surveillance resistance is helpful to alert to veterinarian and select of appropriate therapy. Antimicrobial susceptibility surveillance of isolates should urgently be continued in veterinary medicine.

• Microbiology and Biotechnology Letters
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• v.17 no.6
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• pp.600-605
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• 1989

For the purpose of isolation of the Zymomonas mobilis DNA fragments showing promoter activity in Escherichia coli, a promoter screening vector, PCMT215 was constructed by transferring a promoterless chloramphenicol acetyltransferase (CAT) gene of pYEJ001 into pMT21 which contains $\beta$-lactamase gene and multiple cloning sites. A library of Z, mobilis Sau3AI DNA fragments was constructed in E. coli using the newly constructed pCMT215. Fourteen clones showing resistance to chloramphenicol ranging in concentration from 30 to 750 $\mu$g/$m\ell$ were selected. From five clones of them, the Z. mobilis DNA fragments expressing CAT gene of the recombinant plasmids were sequenced and then sites of transcriptional initiation were identified. The nucleotide sequences of the cloned DNA shared AT rich regions, poly A's or T's stretches and palindromic regions. The positions of transcriptional initiation for CAT gene occurred at more than one site spaced over by 4 to 190 base pairs on the cloned fragments in E. coli.

• Microbiology and Biotechnology Letters
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• v.39 no.2
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• pp.111-118
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• 2011

For the strain improvement of the industrial polyploid yeast strain through hybridization and protoplast fusion, a dominant selection marker other than a recessive marker such as the auxotrophic marker was required for the selection of the resulting hybrids. In the present investigation, the aureobasidin A resistant gene was tested in relation to whether it can be used as the dominant selectable marker for the isolation of hybrids of the yeast Saccharomyces. The plasmid pAUR112, carrying the gene responsible for resistance to aureobasidin A, was introduced into the haploid yeast strain K114/YIp. From the rare-mating between polyploid C6 and haploid K114/YIp carrying pAUR112, many hybrids were obtained from the agar medium containing 0.5 ${\mu}g$/ml of aureobasidin A. The hybrids exhibited characteristics derived from both of the parental strains; and the cell sizes of the hybrids were larger than those of the parental strains. These results showed that the aureobasidin A resistant gene could be successfully used as the dominant selectable marker for the isolation of yeast hybrids resulting from rare-mating.

• Journal of Veterinary Clinics
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• v.21 no.1
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• pp.15-19
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• 2004

The emergence of bacterial resistance to antibiotics during therapy is a matter of great problem in clinical medicine. This may be because many veterinarians have used inappropriate antibiotics without bacteriological culture. Therefore, the purpose of this study is to determine isolation of anaerobic bacteria as pathogens from veterinary clinical specimens as well as susceptibility pattern for choosing antibiotics. Various anaerobic bacteria were isolated from clinical specimens of dogs, cats, rabbits at Veterinary Medical Teaching Hospital of Seoul National University from May 2001 to October 2002. The total number of isolated anaerobic bacteria was 13 isolates; Bacteroides spp. (3 isolates), Fusobacterium spp. (2 isolates), Peptostreptococcus spp. (2 isolates), Porphyromonas gingivalis (2 isolates), Prevotella spp. (3 isolates), and Propionibacterium acnes (1 isolate). For evaluating the antibiotic susceptibility patterns of the isolates disk diffusion method was used. All isolates were susceptable to all tested antibiotics except only one Fusobacterium varium was resistant to norfloxacin.

• Food Science of Animal Resources
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• v.26 no.1
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• pp.106-112
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• 2006

Fifty four acid-resistant and bile-resistant isolates of lactic acid bacteria were initially isolated from the faces of Korea native cattle and Holstein using MRS agar and LAPT agar, and ten strains with superior activity against bile salt were finally selected LS1, LS15, and LL6 isolates showed survival of 66.5%, 82.6% and 80.7% against the simulated stomach liquid(pH 2.5), respectively. LL6 and LL7 isolates had the highest inhibitory activities against the pathogenic bacteria such as Salmonella typhimurium, Staphylococcus aureus, and Clostridium perfringens. By using API 50 CHL kit LS1, LS2 and LM1 isolates were identified as a L. fermentum. LL6 and LL7 isolates as a L. acidophilus, and LS3 isolate as a L. plantarum. The other four isolates belong to genus Lactobacillus. All the isolates tested were sensitive to some antibiotics such as ampicillin, amoxicillin and erythromycin, but resistant to colistin and ciprofloxacin. LB1, LL6 and LL7 isolates were resistant to gentamicin and neomycin. Especially, the LL6 isolate showed the highest resistance to both of the simulated stomach liquid and bile salt, in addition to the highest inhibitory activities against Sal. typhimurium, Staph. aureus and Cl. perfringens.

• Journal of Sensor Science and Technology
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• v.12 no.3
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• pp.103-111
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• 2003

A chromel-alumel thermoelectric flow sensor using $Si_3N_4/SiO_2/Si_3N_4$ thermal isolation membrane was fabricated. Temperature coefficient of resistance of thin film Pt-heater was about $0.00397/^{\circ}C$, and Seebeck coefficient of chromel-alumel thermocouple was about $36\;{\mu}V/K$. The sensor showed that thermoelectric voltage decreased as thermal conductivity of gas increased, and $N_2$-flow sensitivity increased as heater voltage increased or the distance between heater and thermocouple decreased. When heater voltage was about 2.5 V, $N_2$-flow sensitivity and thermal response time of the sensor were about $1.5\;mV/sccm^{1/2}$ and 0.18 sec., respectively. Linear range in flow sensitivity of the flow sensor was wider than that of Bi-Sb flow sensor.

• Journal of Microbiology and Biotechnology
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• v.27 no.7
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• pp.1249-1256
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• 2017

In our search for new sources of bioactive secondary metabolites from Streptomyces sp., the ethyl acetate extracts from endophytic Streptomyces SUK 25 afforded five active diketopiperazine (DKP) compounds. The aim of this study was to characterize the bioactive compounds isolated from endophytic Streptomyces SUK 25 and evaluate their bioactivity against multiple drug resistance (MDR) bacteria such as Enterococcus raffinosus, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumanii, Pseudomonas aeruginosa, and Enterobacter spp., and their cytotoxic activities against the human hepatoma (HepaRG) cell line. The production of secondary metabolites by this strain was optimized through Thornton's medium. Isolation, purification, and identification of the bioactive compounds were carried out using high-performance liquid chromatography, high-resolution mass liquid chromatography-mass spectrometry, Fourier transform infrared spectroscopy, and nuclear magnetic resonance, and cryopreserved HepaRG cells were selected to test the cytotoxicity. The results showed that endophytic Streptomyces SUK 25 produces four active DKP compounds and an acetamide derivative, which were elucidated as $cyclo-({\text\tiny{L}}-Val-{\text\tiny{L}}-Pro)$, $cyclo-({\text\tiny{L}}-Leu-{\text\tiny{L}}-Pro)$, $cyclo-({\text\tiny{L}}-Phe-{\text\tiny{L}}-Pro)$, $cyclo-({\text\tiny{L}}-Val-{\text\tiny{L}}-Phe)$, and N-(7-hydroxy-6-methyl-octyl)-acetamide. These active compounds exhibited activity against methicillin-resistant S. aureus ATCC 43300 and Enterococcus raffinosus, with low toxicity against human hepatoma HepaRG cells. Endophytic Streptomyces SUK 25 has the ability to produce DKP derivatives biologically active against some MDR bacteria with relatively low toxicity against HepaRG cells line.