Pandemic clone USA300 in a Brazilian hospital: detection of an emergent lineage among methicillin-resistant Staphylococcus aureus isolates from bloodstream infections

Clonal shift and impact of azithromycin use on antimicrobial resistance of Staphylococcus aureus isolated from bloodstream infection during the COVID-19 pandemic

Staphylococcus aureus is a relevant pathogen in bloodstream infections (BSI), and the emergency of the COVID-19 pandemic increased its antimicrobial resistance. S. aureus isolates from BSI (September/2019 - March/2021) were analyzed phenotypically and molecularly, in addition to the clinical features of the patients. Of 88 S. aureus isolates recovered from 85 patients, 25 were isolated before the pandemic and 63 during it, and 16 were from patients with COVID-19. A rate of 45.5% of methicillin-resistant isolates (MRSA) were found, and 5% of them were ceftaroline susceptible dose-dependent. Daptomycin non-susceptibility was observed in 9.1% of isolates. The USA800/ST5/SCCmecIV lineage was prevalent among MRSA isolates (41.8%). Besides, 30.2% of the isolates were associated with community-associated MRSA (CA-MRSA) genotypes. There was a significant impact on the resistance rates for cefoxitin, clindamycin and erythromycin among S. aureus isolates from BSI in COVID-19 patients and association with the previous use of azithromycin by them (p < 0.05). A clonal alternation and an increase in the emergence of CA-MRSA lineages were also found, highlighting the importance of constant microbiological surveillance.

Current types of staphylococcal cassette chromosome mec (SCCmec) in clinically relevant coagulase-negative staphylococcal (CoNS) species

Coagulase-negative staphylococci (CoNS) colonize human skin and mucosal membranes, which is why they are considered harmless commensal bacteria. Two species, Staphylococcus epidermidis and Staphylococcus haemolyticus belong to the group of CoNS species and are most frequently isolated from nosocomial infections, including device-associated healthcare-associated infections (DA-HAIs) and local or systemic body-related infections (FBRIs). Methicillin resistance, initially described in Staphylococcus aureus, has also been reported in CoNS species. It is mediated by the mecA gene within the staphylococcal cassette chromosome (SCCmec). SCCmec typing, primarily using PCR-based methods, has been employed as a molecular epidemiological tool. However, the introduction of whole genome sequencing (WGS) and next-generation sequencing (NGS) has enabled the identification and verification of new SCCmec types. This review describes the current distribution of SCCmec types, subtypes, and variants among CoNS species, including S. epidermidis, S. haemolyticus, and S. capitis. The literature review focuses on recent research articles from the past decade that discuss new combinations of SCCmec in coagulase-negative Staphylococcus. The high genetic diversity and gaps in CoNS SCCmec annotation rules underscore the need for an efficient typing system. Typing SCCmec cassettes in CoNS strains is crucial to continuously updating databases and developing a unified classification system.

Emergence of methicillin-resistant Staphylococcus aureus (MRSA) RdJ clone (CC5-ST105-SCCmecII-t002) in Santa Catarina, Brazil

The emergence of highly successful genetic lineages of methicillin-resistant Staphylococcus aureus (MRSA) poses a challenge in human healthcare due to increased morbidity and mortality rates. The RdJ clone (CC5-ST105-SCCmecII-t002 lineage), previously identified in Rio de Janeiro, Brazil, was linked to bloodstream infections and features a mutation in the aur gene (encoding aureolysin). Additionally, clinical isolates derived from this clone were more effective at evading monocytic immune responses. This study aimed to detect the RdJ clone among clinical MRSA isolated in Santa Catarina (SC) and examine its antimicrobial resistance and phagocytosis evasion capabilities. Our findings revealed the RdJ clone in 20 % of MRSA isolates, all exhibiting multiresistance. RdJ clone isolates from SC did not demonstrate a decreased rate of phagocytosis compared to CC5 non-RdJ isolates. Structural analysis suggests that the aur mutation is unlikely to significantly impact aureolysin activity. Genomic analysis of one isolate unveiled a genetic variant of the RdJ clone, sharing lineage and gene distribution but lacking the aur mutation. This study enhances the understanding of the clinical and epidemiologic risks associated with the RdJ clone and the biological mechanisms underlying its spreading in SC.

ST105 Lineage of MRSA: An Emerging Implication for Bloodstream Infection in the American and European Continents

Sequence-type 5 (ST5) of methicillin-resistant Staphylococcus aureus (MRSA), harboring the staphylococcal chromosomal cassette mec type IV (SCCmecIV), was first detected in Portugal. It emerged as a significant cause of healthcare-associated (HA) infection in pediatric units and was hence named the pediatric clone. Another ST5 lineage, which carries SCCmecII, also prevailed in the USA and Japan for multiple years. More recently, another MRSA lineage, ST105-SCCmecII, part of the evolution of clonal complex 5 (CC5) MRSA, has emerged as the cause of hospital-acquired bloodstream infection outbreaks in countries including Portugal, the USA, and Brazil. This article reviews studies on the epidemiology and evolution of these newly emerging pathogens. To this end, a search of PUBMED from inception to 2024 was performed to find articles reporting the occurrence of ST105 MRSA in epidemiologic studies. A second search was performed to find studies on MRSA, CC5, ST5, and SCCmecII. A search of PUBMED from 1999 to 2024 was also performed to identify studies on the genomics and evolution of ST5, CC5, and ST105 MRSA. Further studies were identified by analyzing the references of the previously selected articles from PUBMED. Most articles on ST105 MRSA were included in this review. Only articles written in English were included. Furthermore, only studies that used a reliable genotyping method (e.g., whole genome sequencing, or MLST) to classify the CC5 lineages were selected. The quality and selection of articles were based on the consensus assessment of the three authors in independent evaluations. In conclusion, ST105-SCCmecII is an emerging MRSA in several countries, being the second/third most important CC5 lineage, with a relatively high frequency in bloodstream infections. Of concern is the increased mortality from BSI in patients older than 15 years and the higher prevalence of ST105-SCCmecII in the blood of patients older than 60 years reported in some studies.

Two novel synthetic xanthenodiones as antimicrobial, anti-adhesive and antibiofilm compounds against methicillin resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is widely recognized as a causative agent for various infections acquired in healthcare settings as well as in the community. Given the limited availability of effective antimicrobial agents to combat MRSA infections, there is an increasing need to explore alternative therapeutic strategies. This study aimed to assess the antimicrobial, anti-adhesive, anti-biofilm properties, and toxicity of 175 newly synthesized compounds, belonging to seven different classes, against MRSA. Initially, the compounds underwent screening for antimicrobial activity using the agar diffusion method. Subsequently, active compounds underwent further evaluation to determine their minimum inhibitory concentrations through microdilution. Anti-biofilm and anti-adhesive properties were assessed using the crystal violet method, while toxicity was tested using the alternative infection model Galleria mellonella. Among the tested compounds, two xanthenodiones exhibited the most promising activities, displaying bactericidal effects along with anti-adhesive and anti-biofilm properties. Moreover, the observed non-toxicity in G. mellonella larvae suggests that these compounds hold significant potential as alternative therapeutic options to address the escalating challenge of MRSA resistance in both hospital and community settings.

Atopic dermatitis pediatric patients show high rates of nasal and intestinal colonization by methicillin-resistant Staphylococcus aureus and coagulase-negative staphylococci

BACKGROUND

Atopic dermatitis (AD) patients have high rates of colonization by Staphylococcus aureus, which has been associated with worsening of the disease. This study characterized Staphylococcus spp isolates recovered from nares and feces of pediatric patients with AD in relation to antimicrobial susceptibility, staphylococcal cassette chromosome mec (SCCmec) type, presence of pvl genes and clonality. Besides, gut bacterial community profiles were compared with those of children without AD.

RESULTS

All 55 AD patients evaluated had colonization by Staphylococcus spp. Fifty-three (96.4%) patients had colonization in both clinical sites, whereas one patient each was not colonize in the nares or gut. Staphylococcus aureus was identified in the nostrils and feces of 45 (81.8%) and 39 (70.9%) patients, respectively. Methicillin-resistant Staphylococcus spp. isolates were found in 70.9% of the patients, and 24 (43.6%) had methicillin-resistant S. aureus (MRSA). S. aureus (55.6%) and S. epidermidis (26.5%) were the major species found. The prevalent lineages of S. aureus were USA800/SCCmecIV (47.6%) and USA1100/SCCmecIV (21.4%), and 61.9% of the evaluated patients had the same genotype in both sites. Additionally, gut bacterial profile of AD patients exhibits greater dissimilarity from the control group than it does among varying severities of AD.

CONCLUSIONS

High rates of nasal and intestinal colonization by S. aureus and methicillin-resistant staphylococci isolates were found in AD patients. Besides, gut bacterial profiles of AD patients were distinctly different from those of the control group, emphasizing the importance of monitoring S. aureus colonization and gut microbiome composition in AD patients.

Hospital-Related Lineage of USA300 Methicillin-Resistant Staphylococcus aureus (MRSA) to Cause Bacteremia in Iran

Staphylococcus aureus is an important pathogen that causes bloodstream infections. This study is aimed at assessing the genotypic characteristics of S. aureus strains responsible for bloodstream infections. An epidemiological study was conducted using 85 S. aureus strains isolated from bloodstream infections. Susceptibility was tested using the broth microdilution method and disk diffusion. All detected methicillin-resistant S. aureus (MRSA) isolates were confirmed by mecA PCR assays. S. aureus isolated from bacteremia were characterized using SCCmec, spa, and multilocus sequence typing methods. The prevalence of S. aureus strains responsible for bloodstream infections was 38.8%. All isolates were MRSA. Multidrug resistance (MDR) was present in 84.7% of isolates. MRSA isolated categorized within six clonal complexes including CC8 (60%), CC22 (22.4%), CC5 (5.9%), CC30 (4.7%), CC45 (4.7%), and CC59 (2.3%). The main lineages found were USA300/CC8-MRSA-IV/t008 (41.2%), followed by ST22-SCCmecIV/t790 (9.4%), ST239-SCCmecIII/t037 (7.1%), ST22-SCCmecIV/t032 (7.1%), ST239-SCCmecIII/t631 (5.9%), ST239-SCCmecIII/t860 (5.9%), ST22-SCCmecIV/t852 (5.9%), ST5-SCCmecIV/t002 (4.7%), ST45-SCCmecIV/t038 (4.7%), ST30-SCCmecIV/t318 (4.7%), ST59-SCCmecIV/t437 (2.3%), and ST225-SCCmecII/t045 (1.1%). Resistance to vancomycin amounted to 5.9% of isolates that belonged to ST239-SCCmecIII/t037 (80%) and ST8-SCCmecIV/t008 (20%). The emergence of USA300 strains in bloodstream infections in our country is a serious alarm and highlights the significant invasion of this lineage into the healthcare system. MDR patterns among these strains appear to be becoming the biggest problem in healthcare treatment.

Dissemination of methicillin-resistant Staphylococcus aureus USA300 ST8/PVL- positive in breast infections in a Brazilian region

We aimed to analyze the molecular epidemiology of 46 methicillin-resistant Staphylococcus aureus (MRSA) isolated from breast infections. The USA300 lineage carrying SCCmecIVa, arginine catabolic mobile element, t008, ST8, and Panton-Valentine leukocidin genes was predominant (93%). This is the first study that describes the spread of the USA300 methicillin-resistant Staphylococcus aureus clone in breast infections in Brazil.