Assessing the discriminability of PCR-based open reading frame typing versus single-nucleotide polymorphism analysis via draft whole-genome sequencing of methicillin-resistant Staphylococcus aureus in nosocomial transmission analysis.

Phylogenetic analysis based on single-nucleotide polymorphism (SNP)-based through whole-genome sequencing is recognized as the standard method for probing nosocomial transmission. However, the application of WGS is constrained by the high cost of equipment and the need for diverse analysis tools, which limits its widespread use in clinical laboratory settings. In Japan, the prevalent use of PCR-based open reading frame typing (POT) for tracing methicillin-resistant Staphylococcus aureus (MRSA) transmission routes is attributed to its simplicity and ease of use. Although POT's discriminatory power is considered insufficient for nosocomial transmission analysis, conclusive data supporting this notion is lacking. This study assessed the discriminatory capabilities of SNP analysis and POT across 64 clinical MRSA strains. All 21 MRSA strains of ST5/SCCmec IIa, having more than 16 SNPs, demonstrated distinct clones. Conversely, two strains shared the same POT number and were identified as group A. Among the 12 MRSA strains of ST8/SCCmec IVl with over nine SNPs, five fell into POT group B, and five into POT group C. All four MRSA strains of ST8/SCCmec IVa were classified into POT group D, although they included strains with more than 30 SNPs. Among the 27 MRSA strains of ST1/SCCmec IVa, 14 were classified into POT group E. However, except for two clusters (each comprising two or three strains), all had SNP counts >10 (Fig. 1-D). SNP analysis of MRSA in CC1/SCCmec IV showed that several strains had the same number of SNPs in POT number (106-183-37), even among bacteria with >100 SNPs, indicating POT's limited use in detailed nosocomial transmission analysis.

High Incidence of Metastatic Infections in Panton-Valentine Leucocidin-Negative, Community-Acquired Methicillin-Resistant Staphylococcus aureus Bacteremia: An 11-Year Retrospective Study in Japan.

Panton-Valentine leucocidin (PVL)-negative community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) was originally disseminated in Japan and has since replaced healthcare-associated MRSA (HA-MRSA). However, the clinical characteristics of CA-MRSA bacteremia (CA-MRSAB) compared with those of HA-MRSA bacteremia (HA-MRSAB) are unknown. We aim to clarify differences and investigate associations between the clinical manifestations and virulence genes associated with plasma-biofilm formation in PVL-negative CA-MRSA. From 2011 to 2021, when CA-MRSA dramatically replaced HA-MRSA, 79 MRSA strains were collected from blood cultures and analyzed via SCCmec typing and targeted virulence gene (lukSF-PV, cna, and fnbB) detection. The incidence of metastatic infection was significantly higher in CA-MRSAB than in HA-MRSAB. PVL genes were all negative, although cna and fnbB were positive in 55.6% (20/36) and 50% (18/36) of CA-MRSA strains and 3.7% (1/27) and 7.4% (2/27) of HA-MRSA strains, respectively. cna and fnbB carriage were not associated with the development of metastatic infections in MRSAB; however, the bacteremia duration was significantly longer in CA-MRSAB harboring cna. CA-MRSAB may be more likely to cause metastatic infections than HA-MRSAB. Since CA-MRSA is dominant in Japan, suspected metastatic infection foci should be identified by computed tomography, magnetic resonance imaging, and echocardiography when treating MRSAB.

Community-acquired and healthcare-associated Staphylococcus aureus infections in a pediatric hospital in southern Brazil over 8 years: how common is MRSA?

Backgrounds: Both healthcare-associated and community-acquired methicillin-resistant Staphylococcus aureus (MRSA) infections are relevant in children. The objective of our study was to evaluate their impact in a pediatric hospital in southern Brazil. Methods: Data from patients under 18 years of age with S. aureus infections between January 2013 and December 2020 were retrospectively analyzed. Data were collected regarding infection site, infection type (community-acquired or healthcare-associated), susceptibility to oxacillin [methicillin-susceptible S. aureus (MSSA) or MRSA] and other antimicrobials. We analyzed the evolution of the susceptibility rates for the isolates over this period. Results: A total of 563 patients were included, among whom the prevalences of community- and hospital-acquired MRSA infections were 46.1% and 8.1%, respectively. No significant change occurred in these prevalences over the study period. In community-acquired infections, MSSA was significantly more associated with osteoarticular infections and MRSA was more associated with respiratory and intra-abdominal infections. In healthcare-associated infections, there was an association between MSSA and primary bloodstream infections and between MRSA, skin/soft tissue infections, and respiratory infections. Community-acquired MRSA were highly susceptible to trimethoprim-sulfamethoxazole (96.1%), clindamycin (88.4%), and doxycycline (99.0%). Conclusion: Our study draws attention to the high rates of MRSA in community-acquired staphylococcal infections in this population, indicating a need to review initial protocols for severe staphylococcal infections according to local epidemiology.

A Murine Skin Infection Model Capable of Differentiating the Dermatopathology of Community-Associated MRSA Strain USA300 from Other MRSA Strains.

USA300 is a predominant and highly virulent community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) strain that is a leading cause of skin and soft tissue infections. We established a murine intradermal infection model capable of demonstrating dermatopathological differences between USA300 and other MRSA strains. In this model, USA300 induced dermonecrosis, uniformly presenting as extensive open lesions with a histologically documented profound inflammatory cell infiltrate extending below the subcutis. In contrast, USA400 and a colonizing control strain M92 caused only localized non-ulcerated skin infections associated with a mild focal inflammatory infiltrate. It was also determined that the dermonecrosis induced by USA300 was associated with significantly increased neutrophil recruitment, inhibition of an antibacterial response, and increased production of cytokines/chemokines associated with disease severity. These results suggest that induction of severe skin lesions by USA300 is related to over-activation of neutrophils, inhibition of host antibacterial responses, and selective alteration of host cytokine/chemokine profiles.

Phenotypic and Genotypic Characterization, and Detection of PVL Encoding Gene in Methicillin Resistant Staphylococcus Aureus Strains Isolated From Patients Admitted to a Tertiary Hospital In Kuantan, Malaysia

@#Introduction: Methicillin-resistant Staphylococcus aureus is globally a major public health threat. Resistance to methicillin originates from a modified protein (PBP2a) encoded by the mecA gene. The PVL gene as an important virulence factor increases the pathogenicity of MRSA. Epidemiology and characteristics of MRSA differ in different geographical regions. This study was conducted to characterize and determine the antibiotic susceptibility profile of MRSA strains isolated from patients in Hospital Tengku Ampuan Afzan, Pahang, Malaysia and to detect the presence of the mecA and PVL genes in the isolates. Materials and methods: In this study a total of 36 isolates of MRSA have been collected during a period of three months (1stFebruary –30thApril 2018). The susceptibility pattern of the isolates to ten different commonly used antibiotics were determined and the target genes were addressed by real-time PCR experiment. Results: Based on the identifying criteria, 44.4% of the isolates were CA-MRSA, and 55.5% were HA-MRSA. Resistance to oxacillin, cefoxitin and penicillin was 100%, gentamicin 88.8%, erythromycin 33.3%, tetracycline 77.7%, trimethoprim-sulfamethoxazole 61.1%, clindamycin 13.8%, chloramphenicol 11.1%, but no resistant strain of vancomycin was detected. Most of the isolates were resistant to more than three groups of antibiotics. Realtime PCR revealed that all the isolates were mecA positive and 4 isolates were PVL-positive. PVL-positive strains were CA-MRSA and susceptible to clindamycin. Conclusion: The study confirms multi-drug resistant MRSA in the study area, and shows that resistance to methicillin is mecA mediated. PVL carrier strains were present and related to CA-MRSA strains of the isolates.

Celulitis orbitaria neonatal por Staphylococcus aureus meticilinorresistente de la comunidad / Staphylococcus aureus methicillin-resistant community acquired neonatal orbital cellulitis

La celulitis orbitaria es una patología del niño mayor y raramente compromete al período neonatal. Staphylococcus aureus (SA) es el principal agente etiológico relacionado. El diagnóstico precoz y el tratamiento adecuado mejoran el pronóstico. Se presentan tres recién nacidos con celulitis orbitaria por SA meticilinorresistente de la comunidad (SAMR-CO).

Orbital cellulitis typically occurs in older children, but it can occasionally affect infants and neonates. Staphylococcus aureus is the main pathogen isolated. Outcome depends on an adequate initial approach. We report three neonates with orbital cellulitis caused by community- associated MRSA.

Celulitis orbitaria neonatal por Staphylococcus aureus meticilinorresistente de la comunidad / Staphylococcus aureus methicillin-resistant community acquired neonatal orbital cellulitis

La celulitis orbitaria es una patología del niño mayor y raramente compromete al período neonatal. Staphylococcus aureus (SA) es el principal agente etiológico relacionado. El diagnóstico precoz y el tratamiento adecuado mejoran el pronóstico. Se presentan tres recién nacidos con celulitis orbitaria por SA meticilinorresistente de la comunidad (SAMR-CO).(AU)

Orbital cellulitis typically occurs in older children, but it can occasionally affect infants and neonates. Staphylococcus aureus is the main pathogen isolated. Outcome depends on an adequate initial approach. We report three neonates with orbital cellulitis caused by community- associated MRSA.(AU)

Community and Hospital Onset Methicillin-resistant Staphylococcus aureus in a Tertiary Care Teaching Hospital / 병원감염관리

BACKGROUND: This study evaluated the clinical characteristics and risk factors associated with community and hospital onset MRSA isolated from patients admitted to a tertiary care teaching hospital. METHODS: The study was carried out on MRSA isolated from clinical specimens of patients admitted into the wards and the intensive care unit in a 2,200-bed tertiary care teaching hospital from January 1st through December 31st, 2007. In order to identify the risk factors associated with MRSA acquisition, the medical records were reviewed. All statistics were computed using SPSS version 14.0. RESULTS: Of the 835 MRSA isolates, 179 (21.4%) were CO-MRSA and 656 (78.6%) were HO-MRSA. Of the 179 CO-MRSA isolates, 6 (3.4%) were CA-MRSA. Multiple logistic regression analysis showed that a history of using medical device or antibiotics within 1 year before the isolation of MRSA were significant risk factors for HO-MRSA, and a history of hospitalization within 1 year before the isolation of MRSA was a significant risk factor for CO-MRSA. Analysis on the antibiotics administered within 1 year before the isolation of MRSA showed that levofloxacin, macrolides, 1st generation cephalosporins, 3rd generation cephalosporins, 4th generation cephalosporins, vancomycin, metronidazole, and carbapenem were all significant risk factors for HO-MRSA and that TMP/SMX was a significant risk factor for CO-MRSA. Of the 6 (3.4%) CA-MRSA isolates, 1 (16.7%) was the pathogen responsible for soft tissue infection. No patients died from the CA-MRSA infection. CONCLUSION: MRSA isolated from clinical specimens of patients admitted into the wards and the ICU in a tertiary care teaching hospital was usually HO-MRSA, CO-MRSA and HO-MRSA usually had at least one of the risk factors associated with MRSA acquisition, and CO-MRSA was mainly HACO-MRSA.