• Tuberculosis and Respiratory Diseases
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• v.67 no.5
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• pp.409-412
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• 2009

Background: Several large outbreaks have demonstrated the threat of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) in close-contact environments, such as occurs during training and quartering of military recruits training. In South Korea, which is a hospital or healthcare-associated MRSA prevalent area, military service is compulsory for all healthy young men. We surveyed and determined the extent of CA-MRSA colonization in the upper respiratory tracts of Korean military recruits. Methods: The Korean military recruits who were enrolled in a military training facility from November 2004 to March 2005 were eligible for this study. Sputum or nasopharyngeal swap was obtained from randomly selected subjects who displayed upper respiratory tract symptoms. Results: Of the 181 participants, 32 participants (17.7%) were colonized with S. aureus, and 12 participants (6.6%) were colonized with MRSA. Among the cases that were colonized with S. aureus, 37.5% (12/32) were colonized with MRSA. Antimicrobial susceptibility testing showed resistant patterns that were suggestive of the CA-MRSA strains for all of the MRSA isolates. Conclusion: This study of Korean military recruits found a great deal of showed MRSA colonization in them, and the antimicrobial resistant profile that was suggestive of a CA-MRSA strain. Further efforts to prevent the spread of MRSA infections and careful monitoring for CA-MRSA outbreaks are warranted, especially in a high risk group such as military recruits.

• Journal of Microbiology and Biotechnology
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• v.31 no.9
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• pp.1288-1294
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• 2021

There are a growing number of reports of hospital-acquired infections caused by pathogenic bacteria, especially methicillin-resistant Staphylococcus aureus (MRSA). Many plant products are now being used as a natural means of exploring antimicrobial agents against different types of human pathogenic bacteria. In this research, we sought to isolate and identify an active molecule from Sedum takesimense that has possible antibacterial activity against various clinical isolates of MRSA. NMR analysis revealed that the structure of the HPLC-purified compound was 1,2,4,6-tetra-O-galloyl-glucose. The minimum inhibitory concentration (MIC) of different extract fractions against numerous pathogenic bacteria was determined, and the actively purified compound has potent antibacterial activity against multidrug-resistant pathogenic bacteria, i.e., MRSA and its clinical isolates. In addition, the combination of the active compound and β-lactam antibiotics (e.g., oxacillin) demonstrated synergistic action against MRSA, with a fractional inhibitory concentration (FIC) index of 0.281. The current research revealed an alternative approach to combating pathogenesis caused by multi-drug resistant bacteria using plant materials. Furthermore, using a combination approach in which the active plant-derived compound is combined with antibiotics has proved to be a successful way of destroying pathogens synergistically.

• KSBB Journal
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• v.14 no.4
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• pp.460-464
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• 1999

Methicillin-resistant Staphyloccus aureus (MRSA) has been known to be resistant to many kinds of antibiotics and causes a problem of nosnocomial infection since the third generation of cephalosporines has been introduced in the 1980s. As antibiotic sensitivity tests which have been routinely used to detect MRSA in the laboratory depend on the culture conditions such as, pH, temperature, and time, etc., it is difficult to decide in the case of borderline- or low-level of MRSA. Therefore it would be necessary to develope a new method based on the molecular biological technique to overcome these problems. In this study, we extracted DNA from S. aureus and performed polymerase chain reaction (PCR) to amplify mec A gene, encoding penicillin-binding protein 2' (PBP-2'), which is known to confer bacteria resistance to the bacteriostatic action of methicillin. The results were compares with those of minimal inhibitory concentration (MIC) test. When MIC test with oxacillin was performed on the 120 isolates of S. aureus from each patient's specimens, 64 of them were MRSA and 56 of them were methicillin-sensitive Staphylococcus aureus (MSSA). In pus specimen, more precisely, 61.9% (26/42) of MRSA was detected, and 44.2% (19/43), 60% (9/15) and 50% (10/20) of MRSA were detected in sputum, body fluid, and other specimen respectively. When 40 isolates of MRSA and MSSA were tested by PCR method and compares with the results of MIC method, different results were obtained from 1 isolate of MRSA (2.5%) and in 2 isolates of MSSA (5%) suggesting that PCR method should be performed at the same time for more accurate clinical test of MRSA.

• Pediatric Infection and Vaccine
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• v.23 no.3
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• pp.229-235
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• 2016

Infective endocarditis (IE) caused by methicillin-resistant Staphylococcus aureus (MRSA) has become a worldwide concern. We present a case of a 12-year-old child with IE of the native mitral valve due to MRSA infection after an invasive dental procedure. Based on the clinical symptoms and the presence of cerebrospinal fluid pleocytosis, the patient was initially diagnosed with presumed bacterial meningitis and treated with empiric antibiotics. On the third day of hospitalization, MRSA was cultured from the initial blood samples and vegetation was observed on the mitral valve during an echocardiogram, findings which are compatible with a diagnosis of IE. The revised guidelines for antibiotic prophylaxis for the prevention of IE advise that IE prophylaxis for dental procedures is reasonable only for patients with underlying cardiac conditions, who are at the highest risk of adverse outcomes from IE. However, in this case, the patient had no high risk factors indicative of IE prophylaxis, except for mitral valve prolapse. She had no recurrence of IE over a follow-up period of 12 months.

• Journal of Veterinary Clinics
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• v.25 no.4
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• pp.231-235
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• 2008

Various kinds of antibiotic intramammary infusions are used for treatment of bovine mastitis. As antibiotic-resistant bacteria are increased, the therapeutic rate for bovine mastitis is decreased. The goal of this research is to detect significant synergic effects of combination of antibiotics with sulbactam, $\beta$-lactamase inhibitor, on methicilin-resistant Staphylococcus aureus (MRSA). We used 5 strains of MRSA isolated from bovine mastitis with clinical and subclinical signs. All of the bacteria isolated had resistance to oxacillin and showed multi-resistant patterns in the antimicrobial susceptibility tests. Minimal bactericidal concentrations of ampicillin, amoxicillin, cephalexin, ampicillin/sulbactam(2:1), amoxicillin/sulbactam (2:1), and cephalexin/sulbactam (1:1) were measured according to broth microdilution method suggested by National Committee for Clinical Laboratory Standards (NCCLS, M31-A2) to compare the synergic effects of sulbactam combination with each antibiotic alone. Ampicillin and amoxicillin showed synergic antibacterial activity to 4 and 3 respectively in 5 strains of MRSA in combination with sulbactam. This study demonstrates that ampicillin/sulbactam and amoxicillin/sulbactam can be therapeutic choices for mastitis associated with MRSA.

• Food Science and Biotechnology
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• v.18 no.5
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• pp.1263-1272
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• 2009

Danshen (Salvia miltiorrhiza Bunge) is a traditional Korean medicine that is commonly used for the treatment of inflammatory diseases such as edema, arthritis, hepatitis, and endangitis. The several extracts of danshen were tested for antimicrobial activity against methicillin-resistant Staphylococcus aureus (MRSA) isolated in clinic by broth microdilution method, the checkerboard, and time-kill methods to evaluate the synergistic effects of the combination of the extracts with antibiotics. The chloroform ($CHCl_3$) and n-hexane (HEX) extracts [minimum inhibitory concentration (MIC), 0.0078-0.3125${\mu}g/mL$; minimum bactericidal concentration (MBC), 0.019-0.625${\mu}g/mL$] were found to have strong antibacterial activity against MRSA. Additionally, when the $CHCl_3$ and HEX extracts were co-administered with ampicillin or oxacillin, a synergistic effect against MRSA was observed. Furthermore, a time-kill study evaluating the effects of the extracts against MRSA indicated that treatment with the $CHCl_3$ extract in combination with ampicillin or oxacillin produced rapid bactericidal activity. These results suggest that danshen extracts may have potently antimicrobial activity and thus, it can be a suitable phytotherapeutic agent for treating MRSA infections.

• Korean Journal of Clinical Laboratory Science
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• v.46 no.4
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• pp.136-139
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• 2014

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the severe nosocomial infectious agents. The traditional diagnostic methods including biochemical test, antibiotic susceptibility test and PCR amplification are time consuming and require much work. The Surface enhanced Raman spectroscopy (SERS) biosensor is a rapid and powerful tool for analyzing the chemical composition within a single living cell. To identify the biochemical and genetic characterization of clinical MRSA, all isolates from patients were performed with VITEK2 gram positive (GP) bacterial identification and Antibiotic Susceptibility Testing (AST). Virulence genes of MRSA also were identified by DNA based PCR using specific primers. All isolates, which were placed on a gold coated nanochip, were analyzed by a confocal Raman microscopy system. All isolates were identified as S. aureus by biochemical tests. MRSA, which exhibited antibiotic resistance, demonstrated to be positive gene expression of both femA and mecA. Furthermore, Raman shift of S. aureus and MRSA (n=20) was perfectly distinguished by a confocal Raman microscopy system. This novel technique explained that a SERS based confocal Raman microscopy system can selectively isolate MRSA from non-MRSA. The study recommends the SERS technique as a rapid and sensitive method to detect antibiotic resistant S. aureus in a single cell level.

• Journal of Microbiology and Biotechnology
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• v.32 no.12
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• pp.1537-1546
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• 2022

Staphylococcus aureus is a cause of high mortality in humans and therefore it is necessary to prevent its transmission and reduce infections. Our goals in this research were to investigate the frequency of methicillin-resistant S. aureus (MRSA) in Taif, Saudi Arabia, and assess the relationship between the phenotypic antimicrobial sensitivity patterns and the genes responsible for resistance. In addition, we examined the antimicrobial efficiency and application of silver nanoparticles (AgNPs) against MRSA isolates. Seventy-two nasal swabs were taken from patients; MRSA was cultivated on Mannitol Salt Agar supplemented with methicillin, and 16S rRNA sequencing was conducted in addition to morphological and biochemical identification. Specific resistance genes such as ermAC, aacA-aphD, tetKM, vatABC and mecA were PCR-amplified and resistance plasmids were also investigated. The MRSA incidence was ~49 % among the 72 S. aureus isolates and all MRSA strains were resistant to oxacillin, penicillin, and cefoxitin. However, vancomycin, linezolid, teicoplanin, mupirocin, and rifampicin were effective against 100% of MRSA strains. About 61% of MRSA strains exhibited multidrug resistance and were resistant to 3-12 antimicrobial medications (MDR). Methicillin resistance gene mecA was presented in all MDR-MRSA strains. Most MDR-MRSA contained a plasmid of > 10 kb. To overcome bacterial resistance, AgNPs were applied and displayed high antimicrobial activity and synergistic effect with penicillin. Our findings may help establish programs to control bacterial spread in communities as AgNPs appeared to exert a synergistic effect with penicillin to control bacterial resistance.

• Journal of Microbiology and Biotechnology
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• v.29 no.9
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• pp.1460-1469
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• 2019

The extensive distribution of multidrug-resistant (MDR) methicillin-resistant Staphylococcus aureus (MRSA) poses a threat to healthcare worldwide. This study aimed to investigate the MDR and molecular patterns of MRSA isolates in children admitted to the two biggest tertiary care pediatric hospitals in northern and southern Vietnam. A total of 168 MRSA strains were collected to determine antibiotic susceptibility by minimum inhibitory concentration tests. Antibiotic-resistant genes, pulsed-field gel electrophoresis, staphylococcal cassette chromosome mec (SCCmec) typing, and multilocus sequence typing were used for the molecular characterization of MRSA. Among the total strains, the MDR rate (51.8%) was significantly higher in the northern hospital than in the southern hospital (73% vs. 39%, p < 0.0001). The MDR-MRSA with the highest rates were "ciprofloxacin-erythromycin-gentamicintetracyclines" (35.6%), followed by "erythromycin-tetracycline-chloramphenicol" (24.1%), and "ciprofloxacin-erythromycin-gentamicin" (19.5%), showing an accumulative total of 79.3%. The most susceptible antibiotics were rifampicin (100%) and vancomycin (100%), followed by doxycycline (94.0%), meropenem (78.0%), and cefotaxime (75.0%). The SCCmecII strains showed greater resistance to gentamicin, ciprofloxacin, tetracycline, meropenem and cephalosporins compared with the other strains. The SCCmecII strains exhibited the highest rate in the tested genes (aacA/aphD: 55.2%, ermA/B/C: 89.7%, and tetK/M: 82.8%). ST5-SCCmecII was the predominant clone in the northern hospital, whereas SCCmecIVa was more pronounced in the southern hospital. In conclusion, our results raised concerns about the predominant MDR-MRSA strains in the pediatric hospitals in Vietnam. The north-south difference in the antibiotic resistance patterns and genetic structure of MRSA suggests different MRSA origins and various uses of antimicrobial agents between the two regions.

• Microbiology and Biotechnology Letters
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• v.49 no.3
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• pp.449-457
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• 2021

The aim of the present study was to survey the frequency of inducible and constitutive phenotypes and inducible cross-resistant genes by regulating the methylation of 23S rRNA (ermA, ermB, and ermC) and macrolide efflux-related msrA gene in Staphylococcus aureus and S. epidermidis strains. A total of 172 bacterial isolates (identified based on standard tests), were examined in this study. Antibiotic susceptibility was determined by the disk diffusion method, and all isolates were evaluated with respect to inducible and constitutive phenotypes. The presence of ermA, ermB, ermC, and msrA genes was investigated by a PCR assay. The constitutive resistance phenotypes showed a higher distribution among the isolates. R phenotype was detected more among S. epidermidis isolates (46.25%). ermB, ermC, and msrA genes were detected more in methicillin-resistant S. aureus (MRSA) and methicillin-resistant S. epidermidis (MRSE) isolates that had R and HD phenotypes (>77% strains). The ermA gene had the lowest frequency among MRSA, MRSE, MSSA, and MSSE strains (<14% isolates). Distribution of inducible resistance genes in MRSA and MRSE strains, and possibly other species, leads to increased constitutive resistance to erythromycin, clindamycin, and other similar antibiotics. Therefore, it can be challenging to treat infections caused by these resistant strains.