Epidemiology and staphylococcal cassette chromosome mec typing of methicillin-resistant Staphylococcus aureus isolates in Taiwan: A multicenter study

Global epidemiology of asymptomatic colonisation of methicillin-resistant Staphylococcus aureus in the upper respiratory tract of young children: a systematic review and meta-analysis

OBJECTIVE

To estimate the global prevalence of asymptomatic colonisation, and determine the associated risk factors, antibiotic resistance and genotypes of methicillin-resistant Staphylococcus aureus (MRSA) in the upper respiratory tract of young children.

DESIGN

Four bibliometric databases were searched for publications between 2010 and 2022 according to the protocol registered in PROSPERO. Cross-sectional or cohort studies describing the prevalence of asymptomatic colonisation of S. aureus and MRSA in young children were included. Data extraction and analysis were carried out by two reviewers independently according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 statement. Pooled prevalence was estimated using a random effects model.

SETTING AND STUDIES

We included studies where children without respiratory tract infection or Staphylococcal infection were recruited from the community, children's institutions (ie, nurseries, kindergartens, daycare centres and preschools) and healthcare centre visits and assessed for asymptomatic colonisation with S. aureus and MRSA.

MAIN OUTCOME MEASURES

The pooled prevalence of asymptomatic colonisation of S. aureus and MRSA of young children globally.

RESULTS

In this systematic review and meta-analysis of 21 416 young children, the pooled global prevalence of asymptomatic S. aureus colonisation was 25.1% (95% CI 21.4 to 28.8) and MRSA colonisation was 3.4% (95% CI 2.8 to 4.1). The clones of MRSA strains included healthcare-associated MRSA, community-associated MRSA and livestock-associated MRSA.

CONCLUSION

This study provides evidence of increased MRSA colonisation globally among young children, underlining the critical role of asymptomatic carriers in MRSA transmission and the need for control measures.

PROSPERO REGISTRATION NUMBER

CRD 42022328385.

National surveillance of antimicrobial susceptibilities to ceftaroline, dalbavancin, telavancin, tedizolid, eravacycline, omadacycline, and other comparator antibiotics, and genetic characteristics of bacteremic Staphylococcus aureus isolates in adults: Results from the Surveillance of Multicenter Antimicrobial Resistance in Taiwan (SMART) program in 2020

Methicillin-resistant Staphylococcus aureus (MRSA) causes invasive infections and is associated with community-acquired infections (CAIs) and hospital-associated infections (HAIs). In 2020, 315 S. aureus isolates, including 145 methicillin-susceptible S. aureus (MSSA) and 170 MRSA, mainly associated with bacteremia and mostly CAIs, were collected from 16 hospitals in different regions of Taiwan. Minimum inhibitory concentrations (MICs) were determined using the Sensititre™ complete automated AST system. Staphylococcal cassette chromosome mec (SCCmec) types were analysed using multiplex polymerase chain reaction. The median age of patients infected with MRSA was significantly higher than that of patients infected with MSSA (72.5 years vs. 67.0 years, P=0.027). MIC₅₀/MIC₉₀ values of eravacycline and omadacycline were 0.06/0.12, and 0.25/0.5, respectively. Of the MRSA isolates, 4.1% presented susceptible dose-dependence to ceftaroline, most of which (85.7%) were HAI- and Panton-Valentine leukocidin (PVL)-negative. Among the MRSA isolates, 7.1% were not susceptible to telavancin and tedizolid (mainly type IV, PVL-negative, and CAI), 0.6% were not susceptible to daptomycin (type III, PVL-negative, and HAI), and 1.8% were not susceptible to quinupristin/dalfopristin (three isolates were type III, IV, and V_T, respectively, and all were PVL-negative), but all were susceptible to dalbavancin. In conclusion, patients with bacteremia caused by MRSA were older than those with bacteremia caused by MSSA, SCCmec type IV was more predominant in CAI than in HAI, and MRSA isolates not susceptible to novel anti-MRSA antimicrobials belonged to types II, III, or IV. Further studies that include comprehensive demographics and more detailed descriptions of other antimicrobial-resistant genes are urgently needed.

Discrimination of Methicillin-resistant Staphylococcus aureus by MALDI-TOF Mass Spectrometry with Machine Learning Techniques in Patients with Staphylococcus aureus Bacteremia

Early administration of proper antibiotics is considered to improve the clinical outcomes of Staphylococcus aureus bacteremia (SAB), but routine clinical antimicrobial susceptibility testing takes an additional 24 h after species identification. Recent studies elucidated matrix-assisted laser desorption/ionization time-of-flight mass spectra to discriminate methicillin-resistant strains (MRSA) or even incorporated with machine learning (ML) techniques. However, no universally applicable mass peaks were revealed, which means that the discrimination model might need to be established or calibrated by local strains’ data. Here, a clinically feasible workflow was provided. We collected mass spectra from SAB patients over an 8-month duration and preprocessed by binning with reference peaks. Machine learning models were trained and tested by samples independently of the first six months and the following two months, respectively. The ML models were optimized by genetic algorithm (GA). The accuracy, sensitivity, specificity, and AUC of the independent testing of the best model, i.e., SVM, under the optimal parameters were 87%, 75%, 95%, and 87%, respectively. In summary, almost all resistant results were truly resistant, implying that physicians might escalate antibiotics for MRSA 24 h earlier. This report presents an attainable method for clinical laboratories to build an MRSA model and boost the performance using their local data.

Role of rifampin for the treatment of bacterial infections other than mycobacteriosis

OBJECTIVES

Rifampin was initially approved for the treatment of tuberculosis. Because of its low toxicity, broad-spectrum activity, and good bioavailability, rifampin is now commonly administered as combination antimicrobial therapy for the treatment of various infections caused by organisms other than mycobacteria. This review summarizes the most recent clinical studies on the use of rifampin combinations for treating four common non-mycobacterial infections: acute bacterial meningitis, infective endocarditis and bacteraemia, pneumonia, and biofilm-related infections.

METHODS

We performed a literature search of clinical studies published in English from January 2005 to June 2016 using the PubMed database with the search terms "rifampin" with "meningitis" or "infective endocarditis and bacteraemia" or "pneumonia" or "prosthetic joint infections.

RESULTS

Current evidence to support a rifampin combination therapy as a treatment for non-mycobacterial infections was largely based on in vitro/in vivo studies and non-comparable retrospective case series. Additionally, controlled clinical trials that directly compared outcomes resulting from rifampin treatment versus treatment without rifampin were limited.

CONCLUSIONS

Rifampin combination therapy appears promising for the treatment of non-mycobacterial infections. However, further definitive clinical trials are necessary to validate its use because the risk of adverse drug-drug interactions and of the emergence of rifampin resistance during treatment may outweigh the potential benefits.

Staphylococcal chromosomal cassettes mec (SCCmec): A mobile genetic element in methicillin-resistant Staphylococcus aureus

Considered to be a potential "superbug", methicillin-resistant Staphylococcus aureus (MRSA) has been one of the major recent infectious pathogens and thus poses a challenge to hospital infection control. The mobile genetic element staphylococcal chromosomal cassette mec (SCCmec) carries both the mecA or mecC gene, encoding for a novel specific penicillin-binding protein (PBP2a), and site-specific recombinase genes ccrAB or/and ccrC. In MRSA, the acquisition of SCCmec leads to the resistance to the β-lactam antibiotics. As SCCmec plays a core role in the antimicrobial resistance characteristics, molecular epidemiology and evolution of MRSA, a thorough summary and comprehensive understanding of the prevalence and structural characteristics of SCCmec may aid in global surveillance, implementation and investigation on MRSA isolates, as well as further development of preventive and therapeutic approaches. Consequently, this review is aimed at describing the history, prevalence, types and subtypes, and current typing methods of SCCmec, with the focus on the typical structures of the SCCmec cassette.

Changing epidemiology of community-associated methicillin-resistant Staphylococcus aureus in the Asia-Pacific region

INTRODUCTION

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has become an important threat to public health in the Asia-Pacific region, which is characterized by a large population and relatively insufficient resources. Better understanding on the current status of CA-MRSA in the region is of paramount importance. Areas covered: This article reviews the published literatures on the prevalence, molecular epidemiology, colonization, and hospital spread of CA-MRSA. Expert commentary: The burden of CA-MRSA has been increasing in the past two decades. The molecular epidemiology of CA-MRSA in the Asia-Pacific region shows a marked diversity in each country. Still, some strains - multilocus sequence type (MLST) ST59, ST30, ST72, ST8, and ST772 - are unique clones that have successfully established themselves as predominant, often spreading into nosocomial settings. More coordinated and comprehensive surveillance to understand the true epidemiology of CA-MRSA in the Asia-Pacific region is urgently needed.

The association of molecular typing, vancomycin MIC, and clinical outcome for patients with methicillin-resistant Staphylococcus aureus infections

BACKGROUND/PURPOSE

There are reports of an increase in vancomycin minimum inhibitory concentration (MIC) against methicillin-resistant Staphylococcus aureus (MRSA) over time, a phenomenon referred to as "MIC creep", but some studies have conflicting results. The aim of this study is to evaluate the association of molecular typing, vancomycin MIC, and clinical outcome for patients with MRSA infections.

METHODS

Thirty-two MRSA isolates from Taichung Veterans General Hospital (TCVGH), Taichung, Taiwan during the period of 2003 to 2008 were analyzed for the association of sequence typing, vancomycin MIC, and the correlated clinical outcome for patients with MRSA infections. The vancomycin MICs of 28 additional isolates from 2014 were used for the detection of MIC creep.

RESULTS

Among the genotypes of 32 isolates, there were 17 (53.1%) isolates with ST239-SCCmecIII, seven (21.9%) isolates with ST5-SCCmecII, six (18.8%) isolates with ST59-SCCmecIV, and two (6.2%) isolates with ST59-SCCmecV_T. Two isolates had an MIC of 2 μg/mL and were identified as ST239-SCCmecIII. No statistically significant change in the distribution of MICs of all isolates was observed between 2003 and 2014 (p = 0.263). There was no significant difference in the mortality rates between two groups of patients with vancomycin MICs < 2 μg/mL and ≥ 2 μg/mL (p = > 0.99).

CONCLUSION

There was no vancomycin MIC creep in the period from 2003 to 2014 in this study. Appropriate prognostic models for assessment of the association among sequence types, vancomycin MICs, and clinical outcome warrant further investigation.