Time-calibrated phylogenetic and chromosomal mobilome analyses of Staphylococcus aureus CC398 reveal geographical and host-related evolution.

An international collection of Staphylococcus aureus of clonal complex (CC) 398 from diverse hosts spanning all continents and a 30 year-period is studied based on whole-genome sequencing (WGS) data. The collection consists of publicly available genomic data from 2994 strains and 134 recently sequenced Swiss methicillin-resistant S. aureus (MRSA) CC398 strains. A time-calibrated phylogeny reveals the presence of distinct phylogroups present in Asia, North and South America and Europe. European MRSA diverged from methicillin-susceptible S. aureus (MSSA) at the beginning of the 1950s. Two major European phylogroups (EP4 and EP5), which diverged approximately 1974, are the main drivers of MRSA CC398 spread in Europe. Within EP5, an emergent MRSA lineage spreading among the European horse population (EP5-Leq) diverged approximately 1996 from the pig lineage (EP5-Lpg), and also contains human-related strains. EP5-Leq is characterized by staphylococcal cassette chromosome mec (SCCmec) IVa and spa type t011 (CC398-IVa-t011), and EP5-Lpg by CC398-SCCmecVc-t011. The lineage-specific antibiotic resistance and virulence gene patterns are mostly mediated by the acquisition of mobile genetic elements like SCCmec, S. aureus Genomic Islands (SaGIs), prophages and transposons. Different combinations of virulence factors are present on S. aureus pathogenicity islands (SaPIs), and novel antimicrobial resistance gene containing elements are associated with certain lineages expanding in Europe. This WGS-based analysis reveals the actual evolutionary trajectory and epidemiological trend of the international MRSA CC398 population considering host, temporal, geographical and molecular factors. It provides a baseline for global WGS-based One-Health studies of adaptive evolution of MRSA CC398 as well as for local outbreak investigations.

Biofilm-producing ability of methicillin-resistant Staphylococcus aureus clinically isolated in China.

BACKGROUND: Staphylococcus aureus, a commensal bacterium, colonizes the skin and mucous membranes of approximately 30% of the human population. Apart from conventional resistance mechanisms, one of the pathogenic features of S. aureus is its ability to survive in a biofilm state on both biotic and abiotic surfaces. Due to this characteristic, S. aureus is a major cause of human infections, with Methicillin-Resistant Staphylococcus aureus (MRSA) being a significant contributor to both community-acquired and hospital-acquired infections. RESULTS: Analyzing non-repetitive clinical isolates of MRSA collected from seven provinces and cities in China between 2014 and 2020, it was observed that 53.2% of the MRSA isolates exhibited varying degrees of ability to produce biofilm. The biofilm positivity rate was notably high in MRSA isolates from Guangdong, Jiangxi, and Hubei. The predominant MRSA strains collected in this study were of sequence types ST59, ST5, and ST239, with the biofilm-producing capability mainly distributed among moderate and weak biofilm producers within these ST types. Notably, certain sequence types, such as ST88, exhibited a high prevalence of strong biofilm-producing strains. The study found that SCCmec IV was the predominant type among biofilm-positive MRSA, followed by SCCmec II. Comparing strains with weak and strong biofilm production capabilities, the positive rates of the sdrD and sdrE were higher in strong biofilm producers. The genetic determinants ebp, icaA, icaB, icaC, icaD, icaR, and sdrE were associated with strong biofilm production in MRSA. Additionally, biofilm-negative MRSA isolates showed higher sensitivity rates to cefalotin (94.8%), daptomycin (94.5%), mupirocin (86.5%), teicoplanin (94.5%), fusidic acid (81.0%), and dalbavancin (94.5%) compared to biofilm-positive MRSA isolates. The biofilm positivity rate was consistently above 50% in all collected specimen types. CONCLUSIONS: MRSA strains with biofilm production capability warrant increased vigilance.

Rapid identification and subsequent contextualization of an outbreak of methicillin-resistant Staphylococcus aureus in a neonatal intensive care unit using nanopore sequencing.

Outbreaks of methicillin-resistant Staphylococcus aureus (MRSA) are well described in the neonatal intensive care unit (NICU) setting. Genomics has revolutionized the investigation of such outbreaks; however, to date, this has largely been completed retrospectively and has typically relied on short-read platforms. In 2022, our laboratory established a prospective genomic surveillance system using Oxford Nanopore Technologies sequencing for rapid outbreak detection. Herein, using this system, we describe the detection and control of an outbreak of sequence-type (ST)97 MRSA in our NICU. The outbreak was identified 13 days after the first MRSA-positive culture and at a point where there were only two known cases. Ward screening rapidly defined the extent of the outbreak, with six other infants found to be colonized. There was minimal transmission once the outbreak had been detected and appropriate infection control measures had been instituted; only two further ST97 cases were detected, along with three unrelated non-ST97 MRSA cases. To contextualize the outbreak, core-genome single-nucleotide variants were identified for phylogenetic analysis after de novo assembly of nanopore data. Comparisons with global (n=45) and national surveillance (n=35) ST97 genomes revealed the stepwise evolution of methicillin resistance within this ST97 subset. A distinct cluster comprising nine of the ten ST97-IVa genomes from the NICU was identified, with strains from 2020 to 2022 national surveillance serving as outgroups to this cluster. One ST97-IVa genome presumed to be part of the outbreak formed an outgroup and was retrospectively excluded. A second phylogeny was created using Illumina sequencing, which considerably reduced the branch lengths of the NICU isolates on the phylogenetic tree. However, the overall tree topology and conclusions were unchanged, with the exception of the NICU outbreak cluster, where differences in branch lengths were observed. This analysis demonstrated the ability of a nanopore-only prospective genomic surveillance system to rapidly identify and contextualize an outbreak of MRSA in a NICU.

Increase in methicillin-resistant Staphylococcus spp. colonization among pregnant individuals during COVID-19 pandemic.

Methicillin-resistant Staphylococcus (MRS) has been associated with neonatal infections, with colonization of the anovaginal tract being the main source of vertical transmission. The COVID-19 pandemic has altered the frequency of antibiotic usage, potentially contributing to changes in the dynamics of bacterial agents colonizing humans. Here we determined MRS colonization rates among pregnant individuals attending a single maternity in Rio de Janeiro, Brazil before (January 2019-March 2020) and during (May 2020-March 2021) the COVID-19 pandemic. Anovaginal samples (n = 806 [521 samples before and 285 during the pandemic]) were streaked onto chromogenic media. Colonies were identified by MALDI-TOF MS. Detection of mecA gene and SCCmec typing were assessed by PCR and antimicrobial susceptibility testing was done according to CLSI guidelines. After the onset of the pandemic, MRS colonization rates increased significantly (p < 0.05) from 8.6% (45) to 54.7% (156). Overall, 215 (26.6%) MRS isolates were detected, of which S. haemolyticus was the most prevalent species (MRSH, 84.2%; 181 isolates). SCCmec type V was the most frequent among MRS (63.3%; 136), and 31.6% (68) of MRS strains had a non-typeable SCCmec, due to new combinations of ccr and mecA complexes. Among MRS strains, 41.9% (90) were resistant to at least 3 different classes of antimicrobial agents, and 60% (54) of them were S. haemolyticus harboring SCCmec V. MRS colonization rates and the emergence of multidrug-resistant variants detected in this study indicate the need for continuing surveillance of this important pathogen within maternal and child populations.

Temporal trends of skin and soft tissue infections caused by methicillin-resistant Staphylococcus aureus in Gabon.

BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) is one of the leading causes of mortality due to bacterial antimicrobial resistance. While S. aureus is common in skin and soft tissue infections (SSTI) in Africa, data on MRSA rates are scarce and reports vary widely across the continent (5%-80%). In this study, we describe the proportion of MRSA causing SSTI in Lambaréné, Gabon, over an 11-year period. METHODS: We retrospectively analyzed data from 953 bacterial specimens collected from inpatients and outpatients with SSTI at the Albert Schweitzer Hospital, Lambaréné, Gabon, between 2009 and 2019. We determined temporal changes in the prevalence of MRSA and identified risk factors for SSTI with MRSA. RESULTS: 68% of all specimens with bacterial growth yielded S. aureus (n = 499/731), of which 7% (36/497) with antimicrobial susceptibility testing were identified as MRSA. Age above 18 years, admission to the surgical ward, and deep-seated infections were significantly associated with MRSA as the causative agent. After an initial decline from 7% in 2009, there was a marked increase in the proportion of MRSA among all S. aureus from SSTI from 3 to 20% between 2012 and 2019. The resistance rate to erythromycin was significantly higher in MRSA than in methicillin-susceptible S. aureus (73% vs. 10%), and clindamycin resistance was detected exclusively in MRSA isolates (8%). CONCLUSION: The increasing proportion of MRSA causing SSTI over the 11-year period contrasts with many European countries where MRSA is on decline. Continuous surveillance of MRSA lineages in the hospital and community along with antibiotic stewardship programs could address the increasing trend of MRSA.

Virulence and resistance profiling of Staphylococcus aureus isolated from subclinical bovine mastitis in the Pakistani Pothohar region.

Mastitis is considered one of the most widespread infectious disease of cattle and buffaloes, affecting dairy herds. The current study aimed to characterize the Staphylococcus aureus isolates recovered from subclinical mastitis animals in Pothohar region of the country. A total of 278 milk samples from 17 different dairy farms around two districts of the Pothohar region, Islamabad and Rawalpindi, were collected and screened for sub clinical mastitis using California Mastitis Test. Positive milk samples were processed for isolation of Staphylococcus aureus using mannitol salt agar. The recovered isolates were analyzed for their antimicrobial susceptibility and virulence genes using disc diffusion and PCR respectively. 62.2% samples were positive for subclinical mastitis and in total 70 Staphylococcus aureus isolates were recovered. 21% of these isolates were determined to be methicillin resistant, carrying the mecA gene. S. aureus isolates recovered during the study were resistant to all first line therapeutic antibiotics and in total 52% isolates were multidrug resistant. SCCmec typing revealed MRSA SCCmec types IV and V, indicating potential community-acquired MRSA (CA-MRSA) transmission. Virulence profiling revealed high prevalence of key genes associated with adhesion, toxin production, and immune evasion, such as hla, hlb, clfA, clfB and cap5. Furthermore, the Panton-Valentine leukocidin (PVL) toxin, that is often associated with recurrent skin and soft tissue infections, was present in 5.7% of isolates. In conclusion, the increased prevalence of MRSA in bovine mastitis is highlighted by this study, which also reveals a variety of virulence factors in S. aureus and emphasizes the significance of appropriate antibiotic therapy in combating this economically burdensome disease.

Severe necrotizing tracheobronchitis caused by influenza B and methicillin-resistant Staphylococcus aureus co-infection in an immunocompetent patient.

PURPOSE AND METHOD: Necrotizing tracheobronchitis is a rare clinical entity presented as a necrotic inflammation involving the mainstem trachea and distal bronchi. We reported a case of severe necrotizing tracheobronchitis caused by influenza B and methicillin-resistant Staphylococcus aureus (MRSA) co-infection in an immunocompetent patient. CASE PRESENTATION: We described a 36-year-old man with initial symptoms of cough, rigors, muscle soreness and fever. His status rapidly deteriorated two days later and he was intubated. Bronchoscopy demonstrated severe necrotizing tracheobronchitis, and CT imaging demonstrated multiple patchy and cavitation formation in both lungs. Next-generation sequencing (NGS) and bronchoalveolar lavage fluid (BALF) culture supported the co-infection of influenza B and MRSA. We also found T lymphocyte and NK lymphocyte functions were extremely suppressed during illness exacerbation. The patient was treated with antivirals and antibiotics including vancomycin. Subsequent bronchoscopy and CT scans revealed significant improvement of the airway and pulmonary lesions, and the lymphocyte functions were restored. Finally, this patient was discharged successfully. CONCLUSION: Necrotizing tracheobronchitis should be suspected in patients with rapid deterioration after influenza B infection. The timely diagnosis of co-infection and accurate antibiotics are important to effective treatment.

Characterization of resistance and virulence factors in livestock-associated methicillin-resistant Staphylococcus aureus.

The study investigated the economic concerns associated with livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) in livestock (cow), examining its connection to severe infections, antimicrobial resistance (AMR), and virulence factors. The research, conducted in Edo State, Nigeria, analyzed 400 samples (200 rectal and 200 nasal swabs) collected between March 2018 and February 2019. MRSA prevalence was identified using conventional culture-based methods and polymerase chain reaction (PCR) techniques, revealing 63.5% (n = 254) for Staphylococcus aureus and 55% (n = 220) for MRSA. Of the 76 mecA-positive MRSA isolates, 64.5% (n = 49) exhibited multidrug resistance (MDR) while the remaining were sensitive to specific antimicrobials. Key virulence genes, such as PVL (81.6%; n = 62) and tsst-1 (44.7%; n = 34), were prevalent, along with AMR genes like mecC, tetM, ermA, ermC, vanA, and vanC. Staphylococcal chromosomal cassette mec (SCCmec) typing identified different types, notably II, IVa, and IVb. Biofilm formation, a crucial virulence factor varied in strength, is associated with icaA and icaB genes (p < 0.01). The findings highlighted substantial AMR and biofilm-forming capacity within LA-MRSA isolates, emphasizing the importance of ongoing surveillance for informed treatment strategies, AMR policies, and control measures against MDR staphylococcal infections.

Nasal carriage rate, associated factors, and antimicrobial susceptibility patterns of methicillin resistance Staphylococcus aureus among pre-clinical undergraduate students at the College of Health and Medical Sciences, Haramaya University, Ethiopia.

Background: Staphylococcus aureus nasal carriage has been linked to higher rates of infection and morbidity. People with Methicillin-resistant Staphylococcus aureus can be a potential source of infection for others. University students living together in crowded conditions increase their risk of acquiring infections. The prevalence of S. aureus, particularly Methicillin-resistant Staphylococcus aureus nasal carriage, in Ethiopian university students is sparse. Objective: This study aimed to determine the nasal carriage rate, associated factors, and antimicrobial susceptibility patterns of methicillin-resistant Staphylococcus aureus among pre-clinical students at the College of Health and Medical Sciences, Haramaya University, Ethiopia, from 1 July to 30 August 2022. Methods: An institutional-based cross-sectional study was conducted among 270 randomly selected pre-clinical Health and Medical Sciences students. Data on associated factors were collected using pre-tested, structured questionnaires. A nasal swab was taken from each participant and sent to the microbiology laboratory via Amies transport media in a cold chain. There, it was cultivated using conventional techniques. The isolated colonies were found to be S. aureus, and its antimicrobial susceptibility was performed using the Kirby-Bauer disk diffusion method on Muller-Hinton agar. Methicillin-resistant Staphylococcus aureus expressing using cefoxitin based on CLSI breakpoint. Data were entered into Epi-Data version 4.4.2.1 and exported to the Statistical Package for Social Sciences (SPSS) software version 25 for analysis. Pearson's chi-square test was performed to predict the associations between variables. A p-value less than 0.05 was regarded as statistically significant. Result: Methicillin-resistant Staphylococcus aureus nasal carriage was 5.9% (95% CI: 3.09-8.7) of cases of S. aureus nasal colonization, which was found to be 12.96% (95% CI: 8.85-16.96). Methicillin-resistant Staphylococcus aureus nasal colonization was significantly associated with the history of cigarette smoking (p = 0.000), intake of khat (p = 0.042), nose-picking habit (p = 0.003), history of sharing personal goods (p = 0.021), and history of hospitalizations (p = 0.00). All of the Methicillin-resistant Staphylococcus aureus isolates were resistant to ampicillin and cefoxitin. Conclusion: Based on the findings, a considerable proportion of healthy students harbored Methicillin-resistant Staphylococcus aureus strains associated with behavioral factors. Furthermore, these isolates showed high resistance to cefoxitin and ampicillin. Hence, it is crucial to regularly test pre-clinical students to prevent endogenous infections and the spread of Methicillin-resistant Staphylococcus aureus.

Correlation between carriers of Methicillin-resistant Staphylococcus aureus and the incidence of MRSA surgical site infections in orthopedic surgery patients.

OBJECTIVE: Surgical site infection (SSI) is a devastating complication in orthopedic surgery. Methicillin-resistant Staphylococcus aureus (MRSA) is a notorious organism in SSI, especially in orthopedic patients. We aimed to understand the association between MRSA carriers and the rate of SSI caused by MRSA in orthopedic patients. PATIENTS AND METHODS: We prospectively performed a cohort investigation on patients admitted to the Department of Orthopedic between April and August 2023. Samples were taken preoperatively from the nose and post-operatively in surgical wounds. All samples were grown in MeReSa Agar and defined as positive with MRSA characteristics. Data analysis was performed using SPSS Statistics. A significant difference between groups was assessed using either the Chi-square test or Fisher's exact test. Statistical significance was set at p<0.05. RESULTS: We obtained 526 nasal swabs of patients, and 140 (26.6%) samples were positive for MRSA. Our study revealed significant associations between MRSA carriers and the following factors: history of recent hospitalization (OR: 1.81; 95% CI: 1.172-2.795; p=0.007), smoking history (OR: 1.55; 95% CI: 1.011-2.383; p=0.044), and antibiotic exposures (OR: 2.19; 95% CI: 1.305-3.703; p=0.003). Our findings showed a significant association between SSI and the following factors: history of antibiotic exposures (OR: 2.89; 95% CI: 1.264-6.566; p=0.003), blood loss volume >500 ml (OR: 2.522; 95% CI: 1.245-5.108; p=0.008) and contaminated surgical wounds (OR: 5.97; 95% CI: 2.907-12.266; p=0.001). Patients with MRSA carriers tended to have an increased risk of having an MRSA SSI with an odds ratio of 3.44 (95% CI: 1.13-10.48; p=0.047). CONCLUSIONS: Our study highlights the increased risk of MRSA carriage in patients with a history of smoking, recent hospital admission, or antibiotic exposure. Our reports also identify potential risk factors for SSI, such as previous antibiotic exposure, blood loss, and contaminated wounds. Furthermore, our research establishes an association between MRSA colonization and MRSA SSI, which emphasizes the criticality of decolonization strategies. A further prospective multicenter study is needed to elaborate on our study findings.

News sequences types of Staphylococcus aureus isolated from human pathologicals fluids in Burkina Faso.

Staphylococcus aureus is a pathogen with high epidemic potential frequently involved in nosocomials and communities infections. The pathogenicity of Staphylococcus aureus is due to both its ability to resist antibiotics and to Produce toxins. This work aims at studying the resistance and Molecular Epidemiology of Staphylococcus aureus. Antibiotic susceptibility of the 70 strains isolates of Staphylococcus aureus was determined by agar diffusion while Multiplex PCR and MLST were used to search toxin-coding genes and MRSA typing, respectively. 14.28% of isolates were multidrug resistant. Staphylococcus aureus showed high susceptibility to aminoglycoside and Macrolides familly. lukS-PV/lukF-PV and sea genes were detected in 45% and 3% of Staphylococcus aureus respectively. Ten (10) sequence types including ST5710, ST2430, ST5289, ST5786, ST6942, ST6943, ST6944, ST6945, ST6946, ST6947 have been reported. The study showed a diversity of antibiotic resistance phenotypes and a great diversity of MRSA clones causing infections.

Purulent lymphadenitis caused by ST59 community-associated Methicillin-resistant Staphylococcus aureus in an infant.

INTRODUCTION: Methicillin-resistant Staphylococcus aureus (CA-MRSA), which has the potential to produce serious infections, was a common cause of skin and soft tissue infections, acute purulent lymphadenitis was rare. CASE REPORT: The patient was a female infant with lumps, tenderness, and fever on the right side of the neck and groin. Laboratory tests suggested a bacterial infection. The diagnosis of acute purulent lymphadenitis was made based on the clinical signs and the results of a supporting exam. After three days, MRSA developed in the secretions of suppurative lymph nodes. Her mother's nasopharyngeal swab sample results revealed MRSA. The genotypes of two bacterial strains that underwent molecular analysis were identical. RESULTS: 17 days after admission, the patient showed signs of clinical recovery. CONCLUSIONS: The incident brought to light the possible spread of CA-MRSA in the Chinese population. Even without a definite path of infection, CA-MRSA should be taken into consideration when the standard treatment for children with acute purulent lymphadenitis is ineffective. Early infancy MRSA acquisition may be mostly caused by maternal-infant horizontal transmission.

Effect of silica-sprayed collection tubes on synovial fluid bacterial culture.

INTRODUCTION: Silica-sprayed tubes (SSTs) are often used to transport synovial fluid samples in equine practice. They promote the coagulation of the sample. The objective of the study is to evaluate the effect of SST on bacterial culture. MATERIALS AND METHODS: The study was divided into two parts: sterile saline (Part A) and synovial fluid (Part B). Four common bacteria associated with equine synovial sepsis were used: Streptococcus pyogenes, Escherichia coli, Staphylococcus aureus and methicillin-resistant S. aureus (MRSA). Three collection tubes were used: STT, plain (no-additives) and brain and heart infusion (BHI) broth. Bacteria were cultured in horse blood agar plates for 48 h. Outcome variables were negative culture, positive culture and total number of colony-forming units (CFUs). Statistical analysis was performed using Mann-Whitney U test, and significance was set at p < 0.05. RESULTS: The total number of agar plates read was 1557 (779 saline; 778 synovial fluid). Total negative cultures were 25/779 on saline and 3/778 on synovial fluid. In broth, maximum growth CFU was achieved after 8 h for both saline and synovial fluid for all bacteria. S. pyogenesand E. coli produced a significantly lower number of CFU when in SST compared to plain or broth after 4 h, whereas S. aureus (American Type Culture Collection [ATCC] and MRSA) only after 24 h. DISCUSSION: Silica-containing tubes reduced bacterial proliferation, whereas the use of a BHI broth provided the highest bacterial load in the sample. The use of SST may have a negative effect on bacterial proliferation in samples obtained from clinical cases.

Prevalence and molecular detection of Staphylococcus aureus resistance to antibiotics.

In Algeria, the issue of antibiotic resistance is on the rise, being the Staphylococcus aureus infection as a significant concern of hospital-acquired infections. The emergence of antibiotic resistance in this bacterium poses a worldwide challenge. The aim of this study aims to establish the incidence of S aureus strains in Algeria as well as identify phenotypic and genotypic resistance based on the "mecA" and "nuc" genes. From 2014 to 2017, a total of 185 S aureus strains were isolated from patients at a hospital in the city of Rouïba, Algiers the number of isolates was slightly higher in males at 58.06% compared to females at 41.94%, resulting in a sex ratio of 1.38. the Oxacillin and Cefoxitin DD test (1 µg oxacillin disk and 30 µg cefoxitin disk) identified 42 strains as resistant. The results indicated high resistance to lactam antibiotics, with penicillin having a 100% resistance rate. There was also significant resistance to oxacillin (51.25%) and cefoxitin (50%). This resistance was frequently associated with resistance to other antibiotic classes, such as aminoglycosides (50%) and Macrolides (28.29%). To confirm methicillin-resistant characteristics, a polymerase chain reaction (PCR) multiplex was conducted on 10 isolates (6 SARM; 4 MSSA) on a phenotypic level. Three isolates tested positive for "mecA," while 7 were negative. All strains carry the nuc gene, which is specific to S aureus. In Algeria, the incidence of S aureus resistance is slightly lower compared to other countries, but it is increasing over time. It is now more crucial than ever to restrict the proliferation of multidrug-resistant strains and reduce undue antibiotic prescriptions. To achieve this, it is vital to keep updated on the epidemiology of this bacterium and its antibiotic susceptibility. This will enable the formulation of appropriate preventive control measures to manage its progression.

Target Recognition Triggered Split DNAzyme based Colorimetric Assay for Direct and Sensitive Methicillin-Resistance Analysis of Staphylococcus aureus.

The accurate and rapid detection of methicillin-resistant Staphylococcus aureus (MRSA) holds significant clinical importance. This work presents a new method for detecting methicillin-resistant Staphylococcus aureus (S. aureus) in clinical samples. The method uses an aptamer-based colorimetric assay that combines a recognizing probe to identify the target and split DNAzyme to amplify the signal, resulting in a highly sensitive and direct analysis of methicillin-resistance. The identification of the PBP2a protein on the membrane of S. aureus in clinical samples leads to the allosterism of the recognizing probe, and thus provides a template for the proximity ligation of split DNAzyme. The proximity ligation of split DNAzyme forms an intact DNAzyme to identify the loop section in the L probe and generates a nicking site to release the loop sequence ("3" and "4" fragments). The "3" and "4" fragments forms an intact sequence to induce the catalytic hairpin assembly, exposing the G-rich section. The released the G-rich sequence of LR probe induces the formation of G-quadruplex-hemin DNAzyme as a colorimetric signal readout. The absorption intensity demonstrated a strong linear association with the logarithm of the S. aureus concentration across a wide range of 5 orders of magnitude dynamic range under the optimized experimental parameters. The limit of detection was calculated to be 23 CFU/ml and the method showed high selectivity for MRSA.

Review: the spectrum of antimicrobial resistance in bacteria isolated from wounds of patients with epidermolysis bullosa.

Purpose: Cutaneous infection in epidermolysis bullosa (EB) can cause significant morbidity, mortality, and dangerous sequelae. This review article aims to delve into the known epidemiology of EB, highlight the disease's primary causative agents and their antimicrobial resistance spectrum.Materials and methods: A thorough literature search was conducted using Medline, EMBASE, JBI and PubMed to gather data on the microbial landscape of EB wounds. The focus was on identifying the most common bacteria associated with EB infections and assessing their antimicrobial resistance profiles.Results: The analysis revealed that Staphylococcus aureus is the most frequently identified bacterium in EB wounds, with a notable prevalence of methicillin-resistant strains (MRSA). Specific studies on mupirocin resistance further indicated rising rates of mupirocin-resistant Staphylococcus aureus, with one study reporting rates as high as 16.07%. Additionally, high resistance to other antibiotics, such as levofloxacin and trimethoprim/sulfamethoxazole, was observed in MRSA isolates.Conclusions: The findings highlight the critical need for regular resistance surveillance and the prudent use of mupirocin to manage infections effectively in EB. The multi-drug resistant nature of pathogens in EB presents a significant challenge in treatment, highlighting the importance of antimicrobial stewardship. Ultimately, given the sparse literature and the rarity of large-scale studies, further longitudinal research on the antimicrobial resistance profile of bacteria isolated from EB wounds is essential.

Air dispersal of multi-drug-resistant organisms including meticillin-resistant Staphylococcus aureus, carbapenem-resistant Acinetobacter baumannii and carbapenemase-producing Enterobacterales in general wards: surveillance culture of air grilles.

BACKGROUND: The environmental surveillance of air grilles in clinical areas has not been systematically analysed. METHODS: Samples were collected from frequently touched items (N = 529), air supply (N = 295) and exhaust (N = 184) grilles in six medical and 11 surgical wards for the cultures of multi-drug-resistant organisms (MDROs): meticillin-resistant Staphylococcus aureus (MRSA), carbapenem-resistant Acinetobacter baumannii (CRAB) and carbapenemase-producing Enterobacterales (CPE), and isolates were selected for whole-genome sequencing (WGS). The contamination rates were correlated with the colonization pressures of the respective MDROs. RESULTS: From 3rd October to 21st November 2023, 9.8% (99/1008) of the samples tested positive, with MRSA (24.2%, 24/99), CRAB (59.6%, 59/99) and CPE (2.0%, 2/99), being the only detected MDROs. The contamination rate in air exhaust grilles (26.6%, 49/184) was significantly higher than in air supply grilles (5.8%, 17/295; P<0.001). The contamination rate of air exhaust grilles with any MDRO in acute medical wards (73.7%, 14/19) was significantly higher than in surgical wards (12.5%, 4/32; P<0.001). However, there was no difference in the contamination rate of air exhaust grilles between those located inside and outside the cohort cubicles for MDROs (27.1%, 13/48 vs 28.8%, 30/104; P=0.823). Nevertheless, the weekly CRAB colonization pressure showed a significant correlation with the overall environmental contamination rate (r = 0.878; 95% confidence interval (CI): 0.136-0.986; P=0.004), as well as with the contamination rate in air supply grilles (r = 0.960; 95% CI: 0.375-0.999; P<0.001) and air exhaust grilles (r = 0.850; 95% CI: 0.401-0.980; P=0.008). WGS demonstrated clonal relatedness of isolates collected from patients and air exhaust grilles. CONCLUSIONS: Air grilles may serve as MDRO reservoirs. Cohort nursing in open cubicles may not completely prevent MDRO transmission through air dispersal, prompting the consideration of future hospital design.

Dissemination of meticillin-resistant Staphylococcus aureus sequence type 8 (USA300) in Taiwan.

BACKGROUND: In Taiwan, sequence type (ST) 239 and ST59 were two major clones among meticillin-resistant Staphylococcus aureus (MRSA) clinical isolates in the past two decades. USA300 (ST8) prevailed in the Americas but not in outside areas. Recently USA300 (ST8) emerged and was increasingly identified in Taiwan; we thus conducted an island-wide study to explore the role of USA300 among MRSA isolates. METHODS: One hundred MRSA bloodstream isolates identified in 2020 from each of the six participating hospitals in Taiwan were collected and characterized. The first 10 ST8 isolates from each hospital were further analysed by whole-genome sequencing. RESULTS: Of the 590 confirmed MRSA isolates, a total of 22 pulsotypes and 21 STs were identified. The strain of pulsotype AI/ST8 was the most common lineage identified, accounting for 187 isolates (31.7%) and dominating in five of six hospitals, followed by pulsotype A/ST239 (14.7%), pulsotype C/ST59 (13.9%) and pulsotype D/ST59 (9.2%). Of the 187 pulsotype AI/ST8 isolates, 184 isolates were characterized as USA300 and clustered in three major sub-pulsotypes, accounting for 78%. Ninety per cent of the 60 ST8 isolates for whole-genome sequencing were clustered in three major clades. CONCLUSIONS: In 2020, USA300 became the most common clone of MRSA in Taiwan, accounting for >30% of MRSA bloodstream isolates island wide. Most of USA300 isolates circulating in Taiwan might have been imported on multiple occasions and evolved into at least three successful local clades. MRSA USA300 has successfully established its role in Taiwan, an area outside of the Americas.

Different sampling strategies for optimal detection of the overall genetic diversity of methicillin-resistant Staphylococcus aureus.

Surveillance schemes for methicillin-resistant Staphylococcus aureus (MRSA) are widely established at the national and international levels. Due to the simple standardization of the protocol, mainly isolates from bloodstream infections are used. However, the limitations of this simple surveillance system are well described. We conducted a comprehensive analysis of MRSA isolates in a large Slovenian region over 5 years to identify the optimal sample group for assessing the overall MRSA diversity. At the same time, this study provides to date non-available molecular characterization of Slovenian MRSA isolates. A total of 306 MRSA isolates from various sources were sequenced and phenotypically tested for resistance. The isolates exhibited significant molecular diversity, encompassing 30 multi locus sequence type (MLST) sequence types (STs), 39 ST-SCCmec genetic lineages, 49 spa types, and 29 antibiotic resistance profiles. Furthermore, the isolate pool comprised 57 resistance genes, representing 22 resistance mechanisms, and 96 virulence genes. While bloodstream isolates, commonly used in surveillance, provided insights into frequently detected clones, they overlooked majority of clones and important virulence and resistance genes. Blood culture isolates detected 21.3% spa types, 24.1% resistance phenotypes, and 28.2% MLST-SCCmec profiles. In contrast, strains from soft tissues demonstrated superior genomic diversity capture, with 65.3% spa types, 58.6% resistance phenotypes, and 71.8% MLST-SCCmec profiles. These strains also encompassed 100.0% of virulence and 82.5% of resistance genes, making them better candidates for inclusion in surveillance programs. This study highlights the limitations of relying solely on bloodstream isolates in MRSA surveillance and suggests incorporating strains from soft tissues to obtain a more comprehensive understanding of the epidemiology of MRSA.IMPORTANCEIn this study, we investigated the diversity of methicillin-resistant Staphylococcus aureus (MRSA), a bacterium that can cause infections that are difficult to treat due to its resistance to antimicrobial agents. Currently, surveillance programs for MRSA mainly rely on isolates from bloodstream infections, employing a standardized protocol. However, this study highlights the limitations of this approach and introduces a more comprehensive method. The main goal was to determine which group of samples is best suited to understand the overall diversity of MRSA and to provide, for the first time, molecular characterization of Slovenian MRSA isolates. Our results suggest that including MRSA strains from soft tissue infections rather than just blood infections provides a more accurate and comprehensive view of bacterial diversity and characteristics. This insight is valuable for improving the effectiveness of surveillance programs and for developing strategies to better manage MRSA infections.

Genomic characterization of Staphylococcus aureus isolated from patients admitted to intensive care units of a tertiary care hospital: epidemiological risk of nasal carriage of virulent clone during admission.

We conducted a molecular epidemiological study of Staphylococcus aureus using whole-genome sequence data and clinical data of isolates from nasal swabs of patients admitted to the intensive care unit (ICU) of Hiroshima University hospital. The relationship between isolate genotypes and virulence factors, particularly for isolates that caused infectious diseases during ICU admission was compared with those that did not. The nasal carriage rates of methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) in patients admitted to the ICU were 7.0% and 20.1%, respectively. The carriage rate of community-acquired (CA)-MRSA was 2.3%, accounting for 32.8% of all MRSA isolates. Whole-genome sequencing analysis of the MRSA isolates indicated that most, including CA-MRSA and healthcare-associated (HA)-MRSA, belonged to clonal complex (CC) 8 [sequence type (ST) 8] and SCCmec type IV. Furthermore, results for three disease foci (pneumonia, skin and soft tissue infection, and deep abscess) and the assessment of virulence factor genes associated with disease conditions [bacteremia, acute respiratory distress syndrome (ARDS), disseminated intravascular coagulopathy (DIC), and septic shock] suggested that nasal colonization of S. aureus clones could represent a risk for patients within the ICU. Particularly, MRSA/J and MSSA/J may be more likely to cause deep abscess infection; ST764 may cause ventilation-associated pneumonia, hospital-acquired pneumonia and subsequent bacteremia, and ARDS, and tst-1-positive isolates may cause DIC onset.IMPORTANCENasal colonization of MRSA in patients admitted to the intensive care unit (ICU) may predict the development of MRSA infections. However, no bacteriological data are available to perform risk assessments for Staphylococcus aureus infection onset. In this single-center 2-year genomic surveillance study, we analyzed all S. aureus isolates from nasal swabs of patients admitted to the ICU and those from the blood or lesions of in-patients who developed infectious diseases in the ICU. Furthermore, we identified the virulent clones responsible for causing infectious diseases in the ICU. Herein, we report several virulent clones present in the nares that are predictive of invasive infections. This information may facilitate the design of preemptive strategies to identify and eradicate virulent MRSA strains, reducing nosocomial infections within the ICU.