• Pediatric Infection and Vaccine
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• v.16 no.2
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• pp.150-161
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• 2009

Purpose : Staphylococcus aureus causes a variety of infections, ranging from benign skin infections to fatal invasive infections. Recently, methicillin-resistant S. aureus (MRSA) infections have emerged in patients who do not have established risk factors. This study was conducted to characterize S. aureus infections in children with an emphasis on communityassociated MRSA infections at a tertiary care pediatric facility during a 3-year period. Methods : Four hundred twenty-nine cases of S. aureus infections diagnosed at the Seoul National University Children's Hospital between January 2004 and December 2006 were retrospectively reviewed. The cases were classified as hospitalonset (HO) or community-onset (CO), healthcare-associated (HA), or community-associated (CA) infections. Results : Among the 206 cases <1 year of age, 72%, 7%, and 21% were HO-HA, CO-HA, and CA infections, respectively, as compared to 48%, 28%, and 24% among the 223 cases >1 year of age. The proportion of CO-HA infections among HA infections (8.6% vs. 37.1%, P<0.001) and the proportion of HA infections among the CO infections (24.5% vs. 54.3%, P <0.001) were greater in older children than in infants. Overall, 57% of the isolates were methicillin-resistant. Twenty-nine (30%) of 96 CA strains were MRSA, and the most common site of CA-MRSA infection was the skin and soft tissues (26 cases). Conclusion : The methicillin resistance rate of S. aureus from CA infections was high and CA-MRSA was most often associated with skin and soft tissue infections.

• Biomedical Science Letters
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• v.26 no.3
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• pp.230-237
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• 2020

Staphylococcus aureus (S. aureus) is known as a bacterium that can cause skin infections, respiratory system infections, and sinusitis; however, it can exist as a normal flora rather than a pathogen. Recently, methicillin-resistant S. aureus (MRSA) infections have emerged in the community as a new variant of community-associated (CA)-MRSA. In the present study, S. aureus and MRSA were isolated and cultured by collecting samples from facilities and environments where students and educational personnel have multiple contacts on university campuses; specifically, the nostrils and hands of college students were tested from July to September of 2019. The molecular properties of the isolated MRSA were analyzed, and the one MRSA strain was isolated from the university campuses. One MRSA that was isolated and cultured on campus was the mec complex group A and staphylococcal cassette chromosome (SCC) mec type II, which is a characteristic of healthcare-associated (HA)-MRSA, and SCCmec type V, which is a characteristic of CA-MRSA. This result was similar to other studies wherein the SCCmec type II was detected in SCCmec typing analysis in CA-MRSA. To confirm whether there is a new variant of CA-MRSA in the Republic of Korea, additional follow-up studies on the analysis of virulence factors of MRSA are needed by additionally separating CA-MRSA from the body parts of university students and educational personnel.

• Tuberculosis and Respiratory Diseases
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• v.72 no.3
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• pp.293-301
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• 2012

Background: Ventilator-associated pneumonia (VAP) requires prompt and appropriate treatment. Since methicillin-resistant Staphylococcus aureus (MRSA) is a frequent pathogen in VAP, rapid identification of it, is pivotal. Our aim was to evaluate the utility of quantitative polymerase chain reaction (qPCR) as a useful method for etiologic diagnoses of MRSA pneumonia. Methods: We performed qPCR for mecA, S. aureus-specific femA-SA, and S. epidermidis-specific femA-SE genes from bronchoalveolar lavage or bronchial washing samples obtained from clinically-suspected VAP. Molecular identification of MRSA was based on the presence of the mecA and femA-SA gene, with the absence of the femA-SE gene. To compensate for the experimental and clinical conditions, we spiked an internal control in the course of DNA extraction. We estimated number of colony-forming units per mL (CFU/mL) of MRSA samples through a standard curve of a serially-diluted reference MRSA strain. We compared the threshold cycle (Ct) value with the microbiologic results of MRSA. Results: We obtained the mecA gene standard curve, which showed the detection limit of the mecA gene to be 100 fg, which corresponds to a copy number of 30. We chose cut-off Ct values of 27.94 (equivalent to $1{\times}10^4$ CFU/mL) and 21.78 (equivalent to $1{\times}10^5$ CFU/mL). The sensitivity and specificity of our assay were 88.9% and 88.9% respectively, when compared with quantitative cultures. Conclusion: Our results were valuable for diagnosing and identifying pathogens involved in VAP. We believe our modified qPCR is an appropriate tool for the rapid diagnosis of clinical pathogens regarding patients in the intensive care unit.

• Biomedical Science Letters
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• v.11 no.4
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• pp.525-531
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• 2005

Staphylococcus aureus is a major cause of nosocomial infections and is one of the most commonly isolated bacterial species in the hospital and continues to be an important pathogen in both community and hospital-acquired infection. Methicillin resistant S. aureus (MRSA), which is associated with hospitals is now being isolated in the community. The purpose of this study is to investigate the carrier rate of S. aureus in the community, antibiotic resistance patterns of the organism, detection of MRSA and mecA gene in MRSA. Ninety strains $(46.4\%)$ of S. aureus were isolated from the nasal specimens of 194 elementary school students. Eighty-nine strains $(98.9\%)$ of 90 S. aureus were resistant to penicilin, 36 strains $(40.0\%)$ to erythromycin, 14 strains $(15.6\%)$ to fusidic acid, 11 strains $(12.2\%)$ to gentamycin, 9 strains $(10.0\%)$ to tobramycin, 5 strains $(5.6\%)$ to oxacillin, 4 strains $(4.4\%)$ to clindamycin, 2 strains $(2.2\%)$ to tetracycline, 1 strains $(1.1\%)$ to fosfomycin. None of $90(0\%)$ S. aureus isolates was resistant to ciprpfloxacin, trimethoprim/sulfamethoxazole, levofloxacin, linezolid, moxifloxacin, nitrofurantoin, norfloxacin, rifampicin, quinupristin/dalfopristin, teicoplanin, and vancomycin. Five strains $(5.6\%)$ of 90 S. aureus isolates were MRSA. The mecA gene was detected from five MRSA strains by PCR.

• Pediatric Infection and Vaccine
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• v.15 no.2
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• pp.152-161
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• 2008

Purpose : Staphylococcal scalded skin syndrome (4S) is uncommon, but reports of 4S are on the increase during the recent years. The purpose of this study is to determine the clinical features and associated factors of 4S during the recent 10 years. Methods : We retrospectively reviewed the medical records and microbiologic results of 63 patients (27 neonates and 36 children) from January 1998 to December 2007. Results : Since 2003, the incidence of 4S has increased. The mean age of the patients was 16.3 months and the gender ratio was 1:1. The clinical types of 4S were 38 cases of the abortive type (60%), 19 cases of the intermediate type (30%) and 6 cases of the generalized type (10%). The culture results were 36 cases of Methicillin resistant S. aureus (MRSA), 4 cases of Methicillin sensitive S. aureus and 17 cases of no growth. The patients were treated with semi-synthetic penicillin. For the 9 patients who had MRSA isolated and who didn't improve with penicillin, they were treated with vancomycin instead of penicillin. All the patients had no complications. 4S abruptly increased in 2005, and especially in neonates, due to an MRSA outbreak at a local nursery room. The associated factors of 4S in neonates were hospitalization (27 cases), including nursery infection in 2005 (18 cases) and dermatitis (1 case). There was an unknown origin for some children, and the suggested factors for their infection were community acquired infection (24 cases), atopic dermatitis (9 cases) and hospitalization (3 cases). Conclusion : 4S has recently been increasing. The major associated factors of 4S are a history of hospitalization, an outbreak in a nursery room, atopic dermatitis and community acquired infection.

• Biomedical Science Letters
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• v.27 no.4
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• pp.310-316
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• 2021

Mobile phones used by healthcare workers are not only an indicator of the contamination of healthcare associated bacteria, but can also be another source of infection. The number and time of handwashing, mobile phone operation time and disinfection were highly relation with the bacterial contamination on the surface of mobile phone. Healthcare associated bacteria isolated from the mobile phone surface were 28 MRCoNS (48.3%), 14 S. aureus (24.2%), 3 MRSA (5.2%), 5 A. baumannii (8.6%), 3 MRAB (5.2%), 3 Entrococcus spp. (5.1%), 2 Pantoea spp. (3.4%), 2 A. lowffii (3.4%), 1 E. cloacae (1.7%), 1 P. stutzeri (1.7%), and P. mirabillis (1.7%). For isolation according to department, 2 MRAB from the emergency room and 1 MRSA from intensive unit, the radiology team and the rehabilitation medical team, respectively were isolated. As a result of the relation of isolates from the department of patient contact (ER, RT, GW, CP, ICU, RMT), the bacterial isolation rate was 75% and the department of patient non-contact (MRT) was 10%.

• Journal of Microbiology and Biotechnology
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• v.32 no.6
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• pp.730-739
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• 2022

Methicillin-resistant Staphylococcus aureus (MRSA) causes severe infections and poses a global healthcare challenge. The utilization of novel molecules which confer synergistical effects to existing MRSA-directed antibiotics is one of the well-accepted strategies in lieu of de novo development of new antibiotics. Thymol is a key component of the essential oil of plants in the Thymus and Origanum genera. Despite the absence of antimicrobial potency, thymol is known to inhibit MRSA biofilm formation. However, the anti-MRSA activity of thymol analogs is not well characterized. Here, we assessed the antimicrobial activity of several thymol derivatives and found that 4-chloro-2-isopropyl-5-methylphenol (chlorothymol) has antimicrobial activity against MRSA and in addition it also prevents biofilm formation. Chlorothymol inhibited staphyloxanthin production, slowed MRSA motility, and altered bacterial cell density and size. This compound also showed a synergistic antimicrobial activity with oxacillin against highly resistant S. aureus clinical isolates and biofilms associated with these isolates. Our results demonstrate that chlorinated thymol derivatives should be considered as a new lead compound in anti-MRSA therapeutics.

• Biomedical Science Letters
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• v.16 no.2
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• pp.75-82
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• 2010

The molecular epidemiological characteristics of methicillin-resistant Staphylococcus aureus (MRSA) isolates have demonstrated their genetic diversity and evolution. A total of 137 strains of MRSA clinical isolates was collected from Korean healthcare facility in 2007. The MRSA clinical isolates were analyzed by molecular typings (SCCmec element and agr locus typing), virule nce factor gene detections {(Panton-Valentine leukocidin (PVL), enterotoxin, exfoliative toxin and toxic shock syndrome toxin-1), and amplified fragment length polymorphism (AFLP)}. The MRSA clinical isolates were classified as SCCmec type II-agr type 1 (2 strains), type II-agr type 2 (79 strains), type III-agr type 1 (24 strains), type III-agr type 2 (2 strains), type IV-agr type 1 (27 strains), type IV-agr type 2 (2 strains), and non-typable (1 strain, agr type 3). Based on SCCmec types, SCCmec type II (95.1%) and III (88.5%) indicated higher multidrug resistance rate than SCCmec type IV (10.3%) (P<0.001). The most common enterotoxin genes were seg (83.8%), sei (83.1%), and sec (80.2%). The tst gene was present in 86 out of 137 (62.8%) MRSA isolates. All MRSA isolates were negative for PVL and exfoliative toxin genes. The combinations of toxin genes were observed in particular SCCmec types; 97.6% of SCCmec type II strains carried sec, seg, sei and tst genes, 73.0% of SCCmec type III strains carried sea gene, and 89.7% of SCCmec type IV strains carried sec, seg and sei genes. Each of the SCCmec types of MRSA isolates had distinct AFLP profile. In conclusion, SCCmec type II, agr type 1 and 2 have demonstrated to be the most common types in Korea, and the results indicated that the virulence factors are closely associated with their molecular types (SCCmec and agr types).

• Tuberculosis and Respiratory Diseases
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• v.65 no.3
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• pp.198-206
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• 2008

Background: Tracheobronchial suctioning using the closed suctioning system has physiological benefits for critically ill patients. Despite these benefits, there are concerns about increased colonization of tracheobronchial tree by pathogenic organisms. The cost is another hinder to the introduction of closed suction system. The aim of this study was to evaluate the incidence of colonization and ventilator associated pneumonia and the cost-effectiveness of closed suction compared with open suction. Methods: During separated one month period, patients admitted MICU were cared by multiple-use, open suction, single-use, open suction and multiple-use, closed suction method, consecutively. Costs, colonization of tracheobronchial tree by MRSA and the incidence of ventilator-associated pneumonia (VAP) were analyzed. Results: One-hundred and six patients were enrolled. Twenty patients were treated with multiple-use, open suction, while 42 and 44 patients were cared with single-use, open catheter and multiple-use, closed catheter, respectively. Colonization by MRSA and the incidence of VAP were not different among three ways of suctioning. The overall costs per patient per day for suctioning were $10.58 for multiple-use, open suction, $28.27 for single-use, open suction and $23.76 for multiple-use, closed suction. Conclusion: Multiple-use, closed suctioning, when suction catheters were changed every 48 hrs, has the similar incidence of colonization of MRSA and occurrence of VAP and is a cost-efficient way of endotracheal suction.

• Clinical and Experimental Pediatrics
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• v.53 no.2
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• pp.173-177
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• 2010

Purpose : Methicillin-resistant Staphylococcus aureus (MRSA) is an important pathogen that causes nosocomial infection in NICU. It contributes to neonatal morbidity and mortality with variable complications. This study was conducted to identify the risk factors associated with complicated MRSA bacteremia in neonates. Methods : We reviewed the medical records of 44 neonates with positive blood culture for MRSA who were admitted to the NICU of Pusan National University Hospital from January 2002 to December 2007. We compared various factors of the complicated and uncomplicated MRSA bacteremia cases. Results : Of the 44 neonates, 31 were male and 13, female. The mean gestational age and birth weight were $33.2{\pm}4.9$ weeks and $1,859.9{\pm}962.2g$, respectively. Twenty-one of infants were treated with a mechanical ventilator during a mean of $8.8{\pm}13.8$ days. There were 13 cases of complicated and 31 cases of uncomplicated MRSA bacteremia. Between the 2 groups, we compared the following variables: gestational age, birth weight, ventilator use, umbilical catheter use and central catheter insertion, $O_2$ inhalation, first oral feeding day after birth, underlying disease, transfusion, and initial vancomycin use. The underlying disease and transfusion were the risk factors related to complicated MRSA bacteremia. Conclusion : Complicated MRSA bacteremia is related to underlying disease and transfusion. Since this was a retrospective study with a small sample size, it offered limited capacity to compare complicated and uncomplicated MRSA bacteremia. A prospective study with a larger population is needed to determine the exact characteristics of MRSA bacteremia in NICU.