• Journal of Life Science
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• v.33 no.12
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• pp.1015-1024
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• 2023

Antibiotics have greatly contributed to the treatment and prevention of bacterial diseases in humans, animals, and fish. However, antibiotic misuse has led to the emergence and spread of multidrug-resistant bacteria. In addition to antibiotic discovery research, efforts are being made to combat such multidrug-resistant bacteria using antimicrobial agents, antioxidants, host immune enhancement, probiotics, and bacteriophages, as well as various symptomatic therapies. To discover novel bioactive compounds, it is crucial to adopt approaches that incorporate fresh ideas, new targets, innovative techniques, and untapped resources. Halophytes are plants that grow in high-salt soils and are known to adapt to salt-induced stress through unique metabolic processes that produce secondary metabolites. This study aimed to investigate the effects of extracts of halophytes native to Korea on oxidative stress and to determine whether they exert inhibitory activity against biofilms, which are major pathogenic factors of infectious bacteria. The Acinetobacter baumannii strain ATCC 17978, a representative drug-resistant bacterium, was used to measure anti-biofilm activity. The results showed that Aster spathulifolius, Carex kobomugi, Rosa rugosa, and Asparagus cochinchiensis exerted strong antioxidant and anti-biofilm effects without affecting bacterial growth itself. The halophytes used in this study are promising candidates for the development of pharmaceutical agents with antioxidant and antimicrobial properties.

• Tuberculosis and Respiratory Diseases
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• v.80 no.2
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• pp.159-168
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• 2017

Background: Streptomycin (SM) is recommended by the World Health Organization (WHO) as a part of standard regimens for retreating multidrug-resistant tuberculosis (MDR-TB) cases. The incidence of MDR-TB in retreatment cases was 19% in Thailand. To date, information on SM resistance (SMR) gene mutations correlated to the SMR of Mycobacterium tuberculosis Thai isolates is limited. In this study, the mutations in rpsL, rrs, gidB, and whiB7 were investigated and their association to SMR and the lineage of M. tuberculosis were explored. Methods: The lineages of 287 M. tuberculosis collected from 2007 to 2011 were identified by spoligotyping. Drug susceptibility profiles were evaluated by the absolute concentration method. Mutations in SMR genes of 46 SM-resistant and 55 SM-susceptible isolates were examined by DNA sequencing. Results: Three rpsL (Lys43Arg, Lys88Arg, and Lys88Thr) and two gidB (Trp45Ter and Gly69Asp) mutations were present exclusively in the SM resistant M. tuberculosis. Lys43Arg rpsL was the most predominant SMR mutations (69.6%) and prevailed among Beijing isolates (p<0.001). No SMR-related mutation in was found rrs. The combination of rpsL and gidB mutations provided 76.1% sensitivity for detecting SMR in M. tuberculosis Thai isolates. whiB7 was not responsible for SMR in SM resistant isolates lacking rpsL and rrs mutations. The significance of the three gidB mutations, 276A>C, 615A>G, and 330G>T, as lineage signatures for Beijing and EAI were underscored. This study identified 423G>A gidB as a novel sub-lineage marker for EAI6-BGD1. Conclusion: Our study suggested that the majority of SMR in M. tuberculosis Thai isolates were responsible by rpsL and gidB polymorphisms constantly providing the novel lineage specific makers.

• Tuberculosis and Respiratory Diseases
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• v.70 no.3
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• pp.251-256
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• 2011

The prevalence of multi-drug resistant tuberculosis (MDR-TB), which is resistant to isoniazid and rifampin, has been increasing in Korea. And the side effects of 2nd line anti-tuberculosis medications, including drug-induced hepatitis, are well known. Although prothionamide (PTH) is one of the most useful anti-TB medications and although TB medication-induced acute hepatitis is a severe complication, there are only a few published case reports about prothionamide induced hepatitis. In this case report, a 22 year old male was diagnosed with pulmonary MDR-TB and was administered 2nd line anti-TB mediations, including PTH. Afterwards, he had a spiking fever and his liver enzymes were more than 5 times greater than the upper limit of the normal range. He was then diagnosed with drug-induced hepatitis by liver biopsy. His symptoms and liver enzyme elevation were improved after stopping PTH. Accordingly, we report this case of an association between PTH and acute hepatitis.

• Korean Journal of Plant Resources
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• v.28 no.1
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• pp.9-15
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• 2015

Methicillin-resistant Staphylococcus aureus (MRSA) has been emerging worldwide as one of the most important hospital and community pathogens. At the same time, because of the difficulty in developing chemical synthetic drugs and because of their side-effects, scientists are making more efforts to search for new drugs from plant resources to combat clinical multidrug-resistant microbial infections. Cinnamomum camphora (C. camphora) is a plant of family Lauraceae, and grown Jeju island in South Korea that are used as a drug to treat neurasthenia, epilepsy, cystitis, pyelonephritis, digitalis, cancer, and diabetes mellitus in folk remedies. In this study, antibacterial activites of 80% ethanol extract of C. camphora leaves (CCE) were investigated in combination with antibiotics against clinical isolates of MRSA. The results showed that CCE was determined with MIC and MBC values ranging from 156 to 313 and 313 to $625{\mu}g/ml$, oxacillin from 128 to 256 and 128 to $512{\mu}g/ml$, ampicillin from 4 to 64 and 8 to $128{\mu}g/ml$. The combination of CCE with oxacillin or/and ampicillin were synergistic effect against MRSA 1, 6, 7, 8, 10, 11, 12, 13, and 15/ MRSA 1, 2, 6, and 7.

• Korean Journal of Veterinary Service
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• v.32 no.1
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• pp.49-59
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• 2009

At the present study, it was aimed to explore the states of antimicrobial resistant Salmonella spp. isolates from 3,850 pigs (2,732 ileocecocolic lymphnodes and 1,118 cecal contents) and 1,764 cattle (965 cecal lymphnodes and 799 cecal contents) slaughtered in Busan province from December 2000 to November 2001. Among 5,614 samples, 457 of Salmonella spp. were isolated from pig lymphnodes (13.5%), pig cecal contents (4.4%), cattle lymphnodes (3.5%) and cattle cecal contents (0.5%). Salmonella spp. were showed different isolation ratio, that was 10.8% in summer, 9.0% in autumn, 8.4% in spring and 5.0% in winter. As a result of serotyping, B group (65.4%) were identified as the most common in pigs and cattle, in order of $C_1$ (14.0%), $D_1$ (5.5%), $C_2$ (4.2%), $E_1$ (4.2%) and L (3.5%). 34 serotypes were found, among them, Salmonella Typhimurium (S. Typhimurium) (21.0%) was the most common serotype from pigs and cattle. The major serotypes were in order of S. Derby (15.3%), S. Schwarzengrund (14.7%), S. Typhimurium var Copenhagen (9.2%), S. Mbandaka (5.7%), S. Enteritidis (5.5%) and S. Ruiru (3.5%). The most common serotype was S. Typhimurium in pigs, and S. Ruiru in cattle. S. Ruiru was firstly isolated from pigs and cattle in Korea. In antimicrobial susceptibility test, all the isolates were demonstrated susceptibility to norfloxacin and ofloxacin. But the isolates were showed resistance other antibiotics in order of doxycycline (68.3%), tetracycline (67.8%), penicillin (54.5%) and streptomycin (52.5%). S. Typhimurium were exhibited resistance to ampicillin (34.8%), chloramphenicol (36.2%), streptomycin (94.9%), sulfamethoxazole/trimethoprim (34.8%) and tetracycline (97.8%). There were 53 strains (38.4%) which had multi drug resistant (MDR) isolates, resistant to more than 6 antimicrobial agents. The most common resistance patterns of MDR isolates were ampicillin, chloramphenicol, carbenicillin, doxycycline, nalidixic acid, penicillin, streptomycin, sulfamethoxazole/trimethoprim and tetracycline (ACCbDNaPSSuT).

• Microbiology and Biotechnology Letters
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• v.51 no.4
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• pp.500-506
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• 2023

Carbapenem-resistant Klebsiella pneumoniae (CRKP) is emerging as a worldwide public health threat. Recently, Klebsiella pneumoniae carbapenemase-2 (KPC-2)-producing sequence type (ST) 307 was identified main clone of CRKP, and dissemination of ST307 was reported in South Korea. This study examined the molecular characteristic and antimicrobial resistance pattern of 50 CRKP isolated from a tertiary hospital in Daejeon, from March 2020 to December 2021. Epidemiological relationship was analyzed by Multilocus sequence typing (MLST) and antimicrobial susceptibility test was determined using disk-diffusion method. PCR and DNA sequence analysis were performed to identify carbapenemase genes. CRKP infections were significantly more frequent in males and the patients aged ≥ 60 years. Among the 50 CRKP isolates, 46 isolates (92.0%) were multidrug-resistant (MDR), and 44 isolates (88.0%) were carbapenemase-producing K. pneumoniae (CPKP). The major carbapenemase type was KPC-2 (36 isolates, 72.0%) and New Delhi metalloenzyme-1 (NDM-1) and NDM-5 were identified in 7 isolates (14.0%) and 1 isolate (2.0%), respectively. In particular, 88.9% (32/36) of KPC-2-producing K. pneumoniae belonged to ST307, whereas 87.5% (7/8) of NDM-1,-5-producing K. pneumoniae belonged to non-ST307. These results suggest that proper infection control and effective surveillance network need to prevent not olny the spread of ST307, but also the development of non-ST307.

• Journal of Microbiology
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• v.42 no.1
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• pp.14-19
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• 2004

Salmonella enterica serovar Typhimurium DT104 (Salmonella Typhimurium DT104 or DT104) has been emerging as a common pathogen for human in Korea since 1997. In order to compare the genomic relationship and to search for the dominant strains in Korea, we conducted pulsed-field gel electrophoresis (PFGE) and IS200 fingerprinting of 25 epidemiological unrelated isolates from human and animals from Korea and cattle from America. Two Salmonella Typhimurium DT104 isolates from human in Korea and all 8 isolates from American cattle had indistinguishable patterns from the PFGE and IS200 fingerprinting but multidrug-resistant Salmonella Typhimurium isolates, including DT104, from Korean animals had diverse genetic patterns. The data suggest that a dominant DT104 strain might have circulated between Korean and American cattle and that it had a high level of clonality.

• Clinical and Experimental Pediatrics
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• v.51 no.10
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• pp.1042-1046
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• 2008

The fluoroquinolones are an important group of antibiotics widely used in the treatment of various infectious diseases in adults, as a result of an excellent spectrum of activity, good tissue penetration and convenient ways of administration. In recent decades, there has been extensive development, clinical investigation, licensure and use of fluoroquinolone antibiotics. However, the use of fluoroquinolones in children has been limited because of their potential to induce arthropathy in juvenile animals. Despite class label warnings against use in children, prescriptions for quinolone antibiotics to treat infections in children have become increasingly prevalent. The main use of fluoroquinolones in pediatrics should be, understandably, in serious life-threatening infections for which other antibiotics therapies are not effective or available. While most of the published studies failed to detect an increased rate of articular adverse effects in children treated with fluoroquinolones, an increase in the use of these compounds, particularly in community-acquired lower respiratory infections, could accelerate the emergence of multidrug-resistant (including fluoroquinolone) pneumococcal strains. This review will discus the main issues related to the use of fluoroquinolones in children, the major problems of resistance developing among these compounds, with special emphasis on the potential side effects and skilled use of these alternative potent drugs in pediatric infection.

• Microbiology and Biotechnology Letters
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• v.47 no.4
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• pp.651-661
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• 2019

Targeting the pathogen viability using drugs is associated with development of drug resistance due to selective pressure. Hence, there is an increased interest in developing agents that target bacterial virulence. In this study, the inhibitory effect of ciclopirox, an antifungal agent with iron chelation potential, on the microbial virulence factors was evaluated in 26 clinical MDR Pseudomonas aeruginosa isolates collected from Alexandria Main University Hospital, a tertiary hospital in Egypt. Treatment with 9 ㎍/ml ciclopirox inhibited the hemolytic activity in 70% isolates, reduced pyocyanin production, decreased protease secretion in 46% isolates, lowered twitching and swarming motility, and decreased biofilm formation by 1.5- to 4.5-fold. The quantitative real-time PCR analysis revealed that treatment with ciclopirox downregulated the expression levels of alkaline protease (aprA) and pyocyanin (phzA1). Ciclopirox is used to treat hematological malignancies and the systemic administration of ciclopirox is reported to have adequate oral absorption with a satisfactory drug safety profile. It is important to calculate the appropriate clinical dose and therapeutic index to reposition ciclopirox from a topical antifungal agent to a promising virulence-modifying agent agent against P. aeruginosa, a problematic Gram-negative pathogen.

• Journal of Microbiology and Biotechnology
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• v.28 no.9
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• pp.1426-1432
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• 2018

Staphylococcus aureus causes a broad variety of diseases. The spread of multidrug-resistant S. aureus highlights the need to develop new ways to combat S. aureus infections. Sortase A (SrtA) can anchor proteins containing LPXTG binding motifs to the bacteria surface and plays a key role in S. aureus infections, making it a promising antivirulence target. In the present study, we used a SrtA activity inhibition assay to discover that isovitexin, a Chinese herbal product, can inhibit SrtA activity with an $IC_{50}$ of $28.98{\mu}g/ml$. Using a fibrinogen-binding assay and a biofilm formation assay, we indirectly proved the SrtA inhibitory activity of isovitexin. Additionally, isovitexin treatment decreased the amount of staphylococcal protein A (SpA) on the surface of the cells. These data suggest that isovitexin has the potential to be an anti-infective drug against S. aureus via the inhibition of sortase activity.