• 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.

• Microbiology and Biotechnology Letters
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• v.41 no.3
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• pp.335-340
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• 2013

The antimicrobial effect of the methanol extract of Inula britannica flowers against methicillin resistant Staphylococcus aureus (MRSA) was investigated. It was confirmed that the methanol extract is mainly composed of quercetin, which has antimicrobial properties. The antimicrobial effect of the methanol extract against 3 MRSA strains was determined by the disc diffusion method. The minimal inhibitory concentrations were ranged from 0.625 mg/ml to 1.25 mg/ml, and the minimum bactericidal concentrations were 2.5 mg/ml. Time kill kinetics revealed bactericidal activities, and the morphological alterations in S. aureus ATCC 33591 treated with the extract were observed using a scanning electron microscope. The methanol extract affected the expression of the resistant genes, mecA, mecI, and mecRI in mRNA. Therefore, the methanol extract of I. britannica flowers clearly demonstrated an antimicrobial effect against MRSA and these results suggest a potential for application as a natural antimicrobial agent.

• Korean Journal of Microbiology
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• v.48 no.3
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• pp.212-215
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• 2012

The antimicrobial activity of ursolic acid (UA) and oleanolic acid (OA), both triterpenoid compounds, against methicillin-resistant Staphylococcus aureus (MRSA) is controversial. We examined the antimicrobial effects of UA and OA against 19 strains of MRSA isolated from Koreans by determining minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC). The data showed that the methicillin-sensitive strain S. aureus KCTC $1621^T$ was more resistant to UA and OA than that of the MRSA strains. The MBC values of UA and OA against MRSA had broad ranges; 4 to 32 ${\mu}g/ml$ and 16 to >256 ${\mu}g/ml$, respectively. It was difficult to understand the different antimicrobial activities of UA and OA among the MRSA strains, because UA and OA antimicrobial mechanisms are unknown. These results indicate that the antimicrobial effects of UA and OA against MRSA are dependent on resistance to UA and OA in each strain.

• Pediatric Infection and Vaccine
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• v.20 no.2
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• pp.63-70
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• 2013

Purpose : This study aimed to explore how prevalent the community-related methicillin-resistant Staphylococcus aureus (CA-MRSA) was in children with muscular-skeletal infections. Methods : We retrospectively reviewed the medical records of patients of 18 years or under who were diagnosed with suppurative arthritis or osteomyelitis and S. aureus from September 2000 through August 2012 at the CHA Bundang Medical center. Results : Thirty-one cases of suppurative arthritis or osteomyelitis were identified. The patients were between 17 days old and 18 years old with an average age of 7. Eleven cases (33.5%) of suppurative arthritis and 16 cases (51.6%) of osteomyelitis were observed. Five cases were accompanied by the two diseases. Methicillin sensitive S. aureus (MSSA) was isolated in 25 cases (80.6%) and methicillin resistant S. aureus (MRSA) was isolated in 6 cases (19.4%). Multidrug resistant strains were not observed. MRSA was not found from 2000 through 2005. All patients were treated with antibiotics and the duration of antibiotics treatment was $26.4{\pm}12.7$ days. Vancomycin was used as the initial antibiotic treatment in 4 cases (12.9%) and vancomycin was used as the definitive antibiotics in the 10 cases (32.3%). Conclusions : The result of this study showed that methicillin resistance rate of S. aureus from muscular-skeletal infections was concentrated in the latter half of the 12 year period.

• Pediatric Infection and Vaccine
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• v.16 no.2
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• pp.205-209
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• 2009

Staphylococcal toxic shock syndrome (TSS) is a severe systemic illness caused by toxins produced by Staphylococcus aureus. We report a case of staphylococcal TSS in a 16 month-old boy who presented with high fever, vomiting, skin rash, and shock after a burn injury. He was managed with intravenous vancomycin, fresh frozen plasma, and intravenous immunoglobulin. Methicillin-resistant S. aureus (MRSA) was isolated from the burn wound site and anterior nostril of the patient. In addition, the MRSA isolate was genetically characterized.

• Korean Journal of Veterinary Research
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• v.39 no.2
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• pp.376-382
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• 1999

A methicillin-resistant Staphylococcus aureus (MRSA) isolate was recovered from a 9-month-old female Shih-Tzu dog with canine distemper virus infection. We performed in vitro antimicrobial susceptibility test to determine the most effective antimicrobial drug against the isolate and thus, to emphasize its potential clinical importance in animal practices. Isolate was confirmed MRSA by oxacillin agar screening test. The isolate was fully resistant to all $\beta$-lactam antibiotics and was susceptible to glycopeptides. Of the other antibiotics, mupirocin, TMP/SMZ (trimethoprim-sulfamethoxazole), and chloramphenicol showed inhibitory effect at the concentration of 4x MIC. The MICs ranged 0.25->$128{\mu}g/ml$, and MBCs ranged 0.5->$128{\mu}g/ml$. The combined TMP/SMZ with cefamandole or novobiocin showed synergistic effect, whereas the combination of novobiocin plus cefamandole or teicoplanin resulted in antagonistic effects. Although MRSA in animals so far has been reported in the geographically limited countries, at least theoretically, it could be occurred in the future more frequently through either human or animal origin. The use of this combination may be of value in this situation. As with all antimicrobial agents, inappropriate or unnecessarily prolonged therapy may contribute to the emergence of resistance strains and loss of efficacy.

• Journal of Microbiology and Biotechnology
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• v.32 no.2
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• pp.220-227
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• 2022

The spread of antibiotic-resistant strains of Staphylococcus aureus, a gram-positive opportunistic pathogen, has increased due to the frequent use of antibiotics. Inhibition of the quorum-sensing systems of biofilm-producing strains using plant extracts represents an efficient approach for controlling infections. Torilis japonica is a medicinal herb showing various bioactivities; however, no studies have reported the anti-biofilm effects of T. japonica extracts against drug-resistant S. aureus. In this study, we evaluated the inhibitory effects of T. japonica ethanol extract (TJE) on biofilm production in methicillin-sensitive S. aureus (MSSA) KCTC 1927, methicillin-resistant S. aureus (MRSA) KCCM 40510, and MRSA KCCM 40511. Biofilm assays showed that TJE could inhibit biofilm formation in all strains. Furthermore, the hemolysis of sheep blood was found to be reduced when the strains were treated with TJE. The mRNA expression of agrA, sarA, icaA, hla, and RNAIII was evaluated using reverse transcription-polymerase chain reaction to determine the effect of TJE on the regulation of genes encoding quorum sensing-related virulence factors in MSSA and MRSA. The expression of hla reduced in a concentration-dependent manner upon treatment with TJE. Moreover, the expression levels of other genes were significantly reduced compared to those in the control group. In conclusion, TJE can suppress biofilm formation and virulence factor-related gene expression in MSSA and MRSA strains. The extract may therefore be used to develop treatments for infections caused by antibiotic-resistant S. aureus.