Molecular Epidemiology of Methicillin-Resistant Staphylococcus aureus in Hospitalized Patients in Eastern Heilongjiang Province, China

Molecular Epidemiology of Methicillin-Resistant Staphylococcus aureus among Patients Diagnosed with Surgical Site Infection at Four Hospitals in Ethiopia

Methicillin-resistant Staphylococcus aureus (MRSA) is a common cause of severe surgical site infections (SSI). The molecular epidemiology of MRSA is poorly documented in Ethiopia. This study is designed to determine the prevalence of MRSA and associated factors among patients diagnosed with SSI. A multicenter study was conducted at four hospitals in Ethiopia. A wound culture was performed among 752 SSI patients. This study isolated S. aureus and identified MRSA using standard bacteriology, Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS), and cefoxitin disk diffusion test. The genes mecA, femA, vanA, and vanB were detected through PCR tests. S. aureus was identified in 21.6% of participants, with 24.5% of these being methicillin-resistant Staphylococci and 0.6% showing vancomycin resistance. Using MALDI-TOF MS for the 40 methicillin-resistant Staphylococci, we confirmed that 31 (77.5%) were S. aureus, 6 (15%) were Mammaliicoccus sciuri, and the other 3 (2.5%) were Staphylococcus warneri, Staphylococcus epidermidis, and Staphylococcus haemolyticus. The gene mecA was detected from 27.5% (11/40) of Staphylococci through PCR. Only 36.4% (4/11) were detected in S. aureus, and no vanA or vanB genes were identified. Out of 11 mecA-gene-positive Staphylococci, 8 (72.7%) were detected in Debre Tabor Comprehensive Specialized Hospital. Methicillin-resistant staphylococcal infections were associated with the following risk factors: age ≥ 61 years, prolonged duration of hospital stay, and history of previous antibiotic use, p-values < 0.05. Hospitals should strengthen infection prevention and control strategies and start antimicrobial stewardship programs.

Molecular characterization of typing and subtyping of Staphylococcal cassette chromosome SCCmec types I to V in methicillin-resistant Staphylococcus aureus from clinical isolates from COVID-19 patients

Background and Objectives

Methicillin resistance is acquired by the bacterium due to mecA gene which codes for penicillin-binding protein (PBP2a) having low affinity for β-lactam antibiotics. mecA gene is located on a mobile genetic element called staphylococcal cassette chromosome mec (SCCmec). SCCmec genomic island comprises two site-specific recombinase genes namely ccrA and ccrB [cassette chromosome recombinase] accountable for mobility. Currently, SCCmec elements are classified into types I, II, III, IV and V based on the nature of the mec and ccr gene complexes and are further classified into subtypes according to variances in their J region DNA. SSCmec type IV has been found in community-acquired isolates with various genetic backgrounds. The present study was undertaken to categorize the types of SCCmec types and subtypes I, II, III, IVa, b, c, d, and V and PVL genes among clinical MRSA isolates from COVID-19 confirmed cases.

Materials and Methods

Based on the Microbiological and Molecular (mecA gene PCR amplification) confirmation of MRSA isolated from 500 MRSA SCCmec clinical samples, 144 cultures were selected for multiplex analysis. The multiplex PCR method developed by Zhang et al. was adapted with some experimental alterations to determine the specific type of these isolates.

Results

Of the total 500 MRSA, 144 MRSA (60 were CA-MRSA and 84 were HA-MRSA) were selected for characterization of novel multiplex PCR assay for SSCmec Types I to V in MRSA. Molecular characterization of multiplex PCR analysis revealed results compare to the phenotypic results. Of the 60 CA-MRSA; in 56 MRSA strains type IVa was found and significantly defined as CA-MRSA while 4 strains showed mixed gens subtypes. Type II, III, IA, and V were present in overall 84 HA-MRSA. Molecular subtyping was significantly correlated to define molecularly as CA-MRSA and HA-MRSA however 15 (10%) strains showed mixed genes which indicates the alarming finding of changing epidemiology of CA-MRSA and HA-MRSA as well.

Conclusion

We have all witnessed of COVID-19 pandemic, and its mortality was mostly associated with co-morbid conditions and secondary infections of MDR pathogens. Rapid detections of causative agents of these superbugs with their changing epidemiology by investing in typing and subtyping clones are obligatory. We have described an assay designed for targeting SSCmec types and subtypes I, II, III, IVa,V according to the current updated SCCmec typing system. Changing patterns of molecular epidemiology has been observed by this newly described assay.

Relationship between mortality and molecular epidemiology of methicillin-resistant Staphylococcus aureus bacteremia

Staphylococcus aureus is the primary cause of bacteremia, and methicillin-resistant S. aureus bacteremia is associated with a high mortality rate. Methicillin-resistant S. aureus clones are widespread worldwide, and molecular epidemiological studies are important. Therefore, this study aimed to determine the characteristics of patients who died due to methicillin-resistant S. aureus bacteremia and microbiological characteristics of methicillin-resistant S. aureus strains in a tertiary teaching hospital. This single-center, retrospective study included patients with methicillin-resistant S. aureus isolated from blood bacterial culture performed at Kyoto Prefectural University of Medicine Hospital, from October 2016 to May 2019. The data analyzed included patient background, clinical strain characteristics, and molecular epidemiology. Of 41 patients with methicillin-resistant S. aureus bacteremia (median age, 60 [28–70] years; 24 (59%) were men), and 7 (17%) died due to methicillin-resistant S. aureus bacteremia. The median age of those who died in the methicillin-resistant S. aureus bacteremia group was predominantly higher than that of those in the alive group (p = 0.03). The most common cause of methicillin-resistant S. aureus bacteremia was endovascular devices, which occurred in 20 (49%), 18 (53%), and 2 (29%) patients in the total, alive, and died groups, respectively. Bacteriological characteristics showed that type IV Staphylococcal Cassette Chromosome mec genotype was most frequently detected in the total (n = 34 [83%]), alive (n = 29 [85%]), and died (n = 5 [71%]) groups. In the molecular cluster analysis, CC8, ST8, staphylococcal Cassette Chromosome mec type IV, and community-acquired-methicillin-resistant S. aureus formed the largest groups. The diversity of methicillin-resistant S. aureus clones is evident, and it is possible that clones with new virulence factors may still emerge. In the future, it will be crucial to monitor the epidemiological trends of methicillin-resistant S. aureus to respond quickly to changes in pathogenic and clonal factors, to clarify the gene expression network by identifying old and new virulence factors.

Comparative Genomic Analysis Provides Insights into the Evolution and Genetic Diversity of Community-Genotype Sequence Type 72 Staphylococcus aureus Isolates

Staphylococcus aureus sequence type (ST) 72, the predominant community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) lineage in South Korea, has emerged as a major cause of bloodstream infection in hospital settings. However, relatively little information is available regarding the genomic characteristics and dissemination of ST72. Here, we characterized the whole-genome sequence of 24 ST72 isolates from China, along with 83 ST72 genomes from global sources. Of these 107 ST72 isolates, 63 were MRSA and 44 were methicillin-susceptible S. aureus (MSSA). Phylogenetic analysis revealed four distinct clades (A, B, C, and D), of which clade D contained only MSSA isolates. By characterizing the evolutionary dynamics of the ST72 lineage, we found that the MRSA from China might not have developed from the MSSA in China. Furthermore, we observed both international transmission of ST72 isolates and interregional transmission within China. The distributions of the SCCmec and spa types of isolates differed among clades. Additionally, in silico analyses revealed that the distributions of resistance genes, virulence genes, and mobile genetic elements (MGEs) also differed among isolates of the four clades. This was especially true for clade D isolates, which had the lowest level of antimicrobial resistance and had obtained specific virulence genes such as tsst-1 by acquisition of specific MGEs. Notably, ST72 MRSA isolates were more antibiotic resistant than ST72 MSSA isolates, but comparably virulent. Our findings provide insight into the potential transmission and genotypic features of ST72 clones across the globe.

IMPORTANCE Understanding the evolution and dissemination of community-genotype ST72 Staphylococcus aureus isolates is important, as isolates of this lineage have rapidly spread into hospital settings and caused serious health issues. In this study, we first carried out genome-wide analysis of 107 global ST72 isolates to characterize the evolution and genetic diversity of the ST72 lineage. We found that the MSSA lineage in China might have evolved independently from the MRSA isolates from China, and that ST72 isolates have the potential to undergo both international transmission and interregional transmission within China. The diversity of isolates correlated with distinct acquisitions of SCCmec elements, antibiotic resistance genes, virulence genes, and mobile genetic elements. The comprehensive information on the ST72 lineage emerging from this study will enable improved therapeutic approaches and rapid molecular diagnosis.