• Journal of Animal Science and Technology
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• v.64 no.3
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• pp.515-530
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• 2022

Sequence type (ST) 5 methicillin-resistant Staphylococcus aureus (MRSA) with staphylococcal cassette chromosome mec (SCCmec) type II (ST5-MRSA-II) and ST72-MRSA-IV represent the most significant genotypes for healthcare- (HA) and community-associated (CA) MRSA in Korea, respectively. In addition to the human-type MRSA strains, the prevalence of livestock-associated (LA) MRSA clonal lineages, such as ST541 and ST398 LA-MRSA-V in pigs and ST692 LA-MRSA-V and ST188 LA-MRSA-IV in chickens, has recently been found. In this study, clonotype-specific resistance profiles to cathelicidins derived from humans (LL-37), pigs (PMAP-36), and chickens (CATH-2) were examined using six different ST groups of MRSA strains: ST5 HA-MRSA-II, ST72 CA-MRSA-IV, ST398 LA-MRSA-V, ST541 LA-MRSA-V, ST188 LA-MRSA-IV, and ST692 LA-MRSA-V. Phenotypic characteristics often involved in cathelicidin resistance, such as net surface positive charge, carotenoid production, and hydrogen peroxide susceptibility were also determined in the MRSA strains. Human- and animal-type MRSA strains exhibited clonotype-specific resistance profiles to LL-37, PMAP-36, or CATH-2, indicating the potential role of cathelicidin resistance in the adaptation and colonization of human and animal hosts. The ST5 HA-MRSA isolates showed enhanced resistance to all three cathelicidins and hydrogen peroxide than ST72 CA-MRSA isolates by implementing increased surface positive charge and carotenoid production. In contrast, LA-MRSA strains employed mechanisms independent of surface charge regulation and carotenoid production for cathelicidin resistance. These results suggest that human- and livestock-derived MRSA strains use different strategies to counteract the bactericidal action of cathelicidins during the colonization of their respective host species.

• Pediatric Infection and Vaccine
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• v.16 no.1
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• pp.1-5
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• 2009

Methicillin-resistant Staphylococcus aureus (MRSA), a leading cause of nosocomial infections, has been increasingly recognized in communities of the United States. This article will review the clinical spectrum and treatment of MRSA infections in children in the context of recent epidemiological changes of MRSA infections. In general, community-associated (CA) MRSA most frequently causes skin and soft tissue infections and has an increased association with invasive infections, particularly pneumonia and musculoskeletal infections. Hospital-associated (HA) MRSA strains tend to be associated with bloodstream infections, pneumonia, and surgical site infections. Different from the United States, CA-MRSA infections are not common in Korea (only 5.9%); however, there are some CA-MRSA clones that are different from HA-MRSA clones in Korea and from CA-MRSA clones in other countries. The treatment of MRSA infections should be guided by antimicrobial susceptibility testing, the site of infection, and the infection severity. Vancomycin is the treatment of choice for invasive MRSA infections. Other agents such as trimethoprim-sulfamethoxazole, clindamycin, linezolid, quinupristin-dalfopristin, and daptomycin have been used for some conditions.

• Biomedical Science Letters
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• v.27 no.4
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• pp.195-207
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• 2021

Methicillin-resistant Staphylococcus aureus (MRSA) is a bacterial pathogen capable of causing human diseases, such as soft tissue infection, bacteremia, endocarditis, toxic shock syndrome, pneumonia, and sepsis. Although the incidence rate of diseases caused by MRSA has declined in recent years, these diseases still pose a clinical threat due to their consistently high morbidity and mortality rates. However, the role of virulence factors in staphylococcal infections remains incompletely understood. Methicillin resistance, which confers resistance to all β-lactam antibiotics in cellular islets, is mediated by the mecA gene in the staphylococcal cassette chromosome mec (SCCmec). Differences in SCCmec types and differences in their sizes and structures serve epidemiological purposes and are used to differentiate between hospital-associated (HA)-MRSA and community-associated (CA)-MRSA. Some virulence factors of S. aureus are also providing a distinction between HA-MRSA and CA-MRSA. These factors vary depending on the presence of toxins, adhesion, immune evasion, and other virulence determinants. In this review, we summarized an overview of MRSA such as resistance mechanisms, SCCmec types, HA- and CA-MRSA, and virulence factors that enhance pathogenicity or MRSA epidemiology, transmission, and genetic diversity.

• 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.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.

• 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.

• Pediatric Infection and Vaccine
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• v.18 no.2
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• pp.143-153
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• 2011

Purpose : It is known that carriage rates of Staphylococcus aureus (S. aureus) are highest in newborns and that the asymptomatic carriage of methicillin-resistant Staphylococcus aureus (MRSA) is associated with invasive MRSA infection with the colonizing strain. This study was carried out to investigate the carriage rates of MRSA in neonates with neonatal jaundice. Methods : We reviewed the medical records of 545 neonates admitted with neonatal jaundice to neonatal intensive care units between January 2006 and December 2010. Nasal and inguinal swab specimens had been taken from them and cultured for the isolation of S. aureus. Antimicrobial susceptibility tests had been done for such isolates to determine methicillinresistance. Results : Out of 545 neonates, 318 (58.3%) were colonized with S. aureus and 214 (39.3%) were colonized with MRSA. Results of the antibiogram analysis showed that 65.7% of MRSA isolates were likely to be community-associated (CA) MRSA. Conclusion : Based on the MRSA carriage rate of 39.3%, a surveillance program for MRSA colonization is considered necessary in neonates transferred from other clinics or hospitals. Out of MRSA isolates, 65.7% were likely to be CA-MRSA. This suggests that CA-MRSA strains were already present in obstetric clinic environments where the neonates were born. It is thought that MRSA surveillance programs in these environments are also necessary.

• Tuberculosis and Respiratory Diseases
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• v.75 no.2
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• pp.75-78
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• 2013

Methcillin-resistant Staphylococcus aureus (MRSA) has emerged as an important cause of community-acquired infections, which has been recently designated as community-associated (CA) MRSA. Panton-Valentine leukocidin (PVL)-negative multilocus sequence type 72 (ST72)-staphylococcal cassette chromosome mec (SCCmec) type IV has been reported as the predominat CA-MRSA strain in Korea and is commonly associated with skin and soft tissue infections in addition to healthcare-associated pneumonia. However, community-acquired pneumonia (CAP) for this strain has not yet been reported. We hereby report two cases of CAP caused by PVL-negative ST72-SCCmec type IV strain in patients who had no risk factors for MRSA acquisition. While CA-MRSA infections are not yet prevalent in Korea, our cases suggest that CA-MRSA should be considered in cases of severe CAP, especially for cases associated with necrotizing pneumonia.

• Pediatric Infection and Vaccine
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• v.19 no.3
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• pp.111-120
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• 2012

Purpose: The aim of this study is to investigate the colonization rate of Methicillin-resistant Staphylococcus aureus (MRSA) in neonates by different clinical characteristics, to presume the origin of MRSA acquisition, and to identify the risk factors associated with MRSA colonization. Methods: We retrospectively reviewed the medical records of 1,733 neonates admitted to Seoul Eulji hospital Neonatal Intensive Care Unit between January 2008 and December 2011. Nasal, inguinal and rectal swab specimens were obtained upon admission and each week until discharge. We classified the route of MRSA acquisition as; hospital associated (HA-MRSA) and community associated (CA-MRSA) according to the case definition. Results: Among 1,733 neonates, 415 (23.9%) were colonized with MRSA. Gestational age, birth weight, delivery type, maternal antibiotics usage before delivery, birth place and care place before admission were influencing factors in colonization of MRSA. The colonization rate was significantly high in neonates without maternal prophylactic antibiotics use before delivery than in the other group (relative risk 2.77, 95% CI 1.88-4.07; P<0.01), and outborns showed higher MRSA colonization rate compared to inborns (relative risk 2.28, 95% CI 1.17-4.42; P=0.015). Conclusion: We identified the neonatal MRSA colonization rate to be 23.9%. We estimated HA-MRSA colonization rate to be 10% (51/511) and CA-MRSA colonization rate to be 36% (309/858). We ascertained that risk factors in MRSA colonization in neonates were prophylactic use of antibiotics in mothers and the birth place.

• Pediatric Infection and Vaccine
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• v.17 no.1
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• pp.9-15
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• 2010

Purpose : This study was performed to investigate the prevalence of Staphylococcus aureus (S. aureus) nasal carriage in Korean children attending day care centers. Methods : During September and October 2009, a survey for nasal carriage of S. aureus and methicillin-resistant S. aureus (MRSA) was conducted among children attending day care centers located in Seoul with questionnaire survey for evaluation of risk factors of acquisition of MRSA was obtained from their guardians. A culture of the anterior nares swabs using enrichment broth was executed for isolating S. aureus and oxacillin susceptibility was assessed by the disk diffusion method. Results : Out of the 428 children enrolled whose mean age was 55 months old, 163 (38.1%) were colonized with S. aureus. Of the 163 isolates, 40 (24.5%) were MRSA. The nasal carriage rate of S. aureus showed an increasing trend with increase of age. Based on the answer to the questionnaire, 9.2% and 3.6% of children had a recent history of hospitalization and surgery, respectively, and approximately 40% of children had a history of prescription of antibiotics within 1 year prior to enrollment. Of the 428 subjects, 40 (9.3%) were MRSA nasal carriers. Conclusion : S. aureus and MRSA carriage rate of children attending day care center in Korea was 38.1% and 9.3%, respectively. Continued surveillance for nasal carriage rate of S. aureus and MRSA (especially community-associated MRSA) is mandatory.