Clonality, virulence genes, and antibiotic resistance of Staphylococcus aureus isolated from blood in Shandong, China.

Bloodstream infection (BSI) caused by Staphylococcus aureus (S. aureus) can be life-threatening and pose a great challenge to infection control and clinical treatment. However, little information exists regarding the characterization of S. aureus in BSI patients in Shandong, China. To identify the clonality, virulence genes, and antibiotic resistance of S. aureus in blood, a total of 101 nonrepetitive blood isolates were collected. The antibiotic resistance phenotypes were determined, and virulence genes were analyzed with polymerase chain reaction (PCR). Finally, the genetic relatedness was investigated with Staphylococcus chromosomal cassette mec (SCCmec) typing for methicillin-resistant S. aureus (MRSA) isolates, Staphylococcal protein A (spa), and multilocus sequence typing (MLST) for all of 101 isolates. Of the 101 S. aureus isolates, 24 MRSA isolates and 77 methicillin-susceptible S. aureus (MSSA) isolates were identified. Overall, MRSA isolates had higher resistance rates than MSSA isolates when exposed to any of the 15 antibiotics tested in this study except for trimethoprim/sulfamethoxazole. Among the 17 virulence genes tested in this study, hla, hld, and hlg could be detected in all isolates. MRSA isolates were more likely to carry seb and hlb genes, while MSSA isolates were more likely to carry seg and sei genes. Thirty-five sequence types (STs) and 49 spa types were identified, of which ST59-t437 and ST398-t571 were the most abundant. These two genotypes were also the most abundant ST-spa types in MRSA and MSSA isolates, but their abundances shifted over time, with ST398-t571 being the predominant genotype from 2016 to 2017, and ST59-t437 from 2018 to 2020. Besides, all the ST59-t437 isolates harbored hlgb gene, whereas most (88.9%) ST398-t571 did not. In addition, twenty-four MRSA isolates were subject to SCCmec typing. SCCmec IVa was the most prevalent SCCmec type, and all the ST59-t437 MRSA isolates were SCCmec IVa. We also observed 15 new STs, and some of them were MRSA. These findings provide additional observations and epidemiological data for blood S. aureus isolates, which can improve future infection-control measures and aid in potential clinical treatments in hospitals and other clinical settings.

Wang X ，Lin D ，Huang Z ，Zhang J ，Xie W ，Liu P ，Jing H ，Wang J ... -  《BMC MICROBIOLOGY》

Molecular characteristics and virulence gene profiles of Staphylococcus aureus isolates in Hainan, China.

Li X ，Huang T ，Xu K ，Li C ，Li Y ... -  《BMC INFECTIOUS DISEASES》

Multiresistant ST59-SCCmec IV-t437 clone with strong biofilm-forming capacity was identified predominantly in MRSA isolated from Chinese children.

Yang X ，Qian S ，Yao K ，Wang L ，Liu Y ，Dong F ，Song W ，Zhen J ，Zhou W ，Xu H ，Zheng H ，Li W ... -  《BMC INFECTIOUS DISEASES》

Virulence gene profiling and molecular characterization of hospital-acquired Staphylococcus aureus isolates associated with bloodstream infection.

A better understanding of virulence gene profiling and molecular characterization of Staphylococcus aureus isolates associated with bloodstream infection (BSI) may provide further insights related to clinical outcomes with these infections. We analyzed 89 S. aureus isolates including 37 MRSA isolates (41.6%) recovered from 89 adult patients with BSI from 4 hospitals in Zhejiang province, eastern China. Thirty-five (94.6%) of MRSA isolates and 4 (7.7%) of methicillin-sensitive S. aureus (MSSA) isolates were resistant to multiple antimicrobials. All isolates harbored at least 2 of 22 possible virulence genes, including sdrC (92.1%), icaA (89.9%), hla (80.9%), clf (69.7%), sea (68.5%), sdrD (67.4%), hlb (67.4%), sdrE (65.2%), sei (51.7%), seg (50.6%), and cna (50.6%). Forty-four (49.4%) of all S. aureus BSI isolates, including 23 (62.2%) of MRSA isolates, harbored ≥10 of the virulence genes evaluated in this study. Sixteen (43.2%) MRSA isolates and 5 (9.6%) MSSA isolates harbored the gene encoding Panton-Valentine leukocidin (PVL). Collective genes for pvl, sdrE, sed, seg, and sei among MRSA isolates were significantly more frequent relative to MSSA isolates (P < 0.05). A total of 22 sequence types (STs), including novel ST2184, ST2199, and ST2200, and 33 spa types, including novel spa types t9530 and t9532, were identified among S. aureus BSI isolates, among which ST188 (15.7%) and ST7 (15.7%), and t091 (12.4%) and t189 (12.4%), seldom noted for Chinese isolates previously, were major STs and spa types, respectively. In contrast to previous reports, no predominant clones were found in the present study. Among the MRSA isolates, although ST239-MRSA-SCCmecIII, predominant clone in China, still represented the most common clone, it only accounted for 18.9%. However, ST188-MRSA- SCCmecIV seldom reported before accounted for 10.8%. Among the MSSA isolates, ST7-MSSA represented the most common clone (23.1%), followed by ST188-MSSA and ST630-MSSA (9.6% each). In conclusion, simultaneous carriage of multiple virulence genes and genetically considerable diversity were common among S. aureus BSI isolates. Furthermore, MRSA isolates exhibited more frequent carriage of superantigen genes and pvl relative to MSSA isolates. Taken together, there are distinctive virulence gene profiling and molecular characteristic among S. aureus isolates associated with bloodstream infection in China.

Yu F ，Li T ，Huang X ，Xie J ，Xu Y ，Tu J ，Qin Z ，Parsons C ，Wang J ，Hu L ，Wang L ... -  《-》

Molecular characterization and virulence gene profiling of methicillin-resistant Staphylococcus aureus associated with bloodstream infections in southern China.

Methicillin-resistant Staphylococcus aureus (MRSA) causes an enormous illness burden, including skin and soft tissue infections (SSTIs), pneumonia, bloodstream infections (BSI), and sepsis. BSI are associated with significant patient morbidity and mortality worldwide. However, limited information is available on MRSA-related BSI in China. This study aimed to investigate the molecular characterization of 77 MRSA isolates recovered from hospitalized patients with BSI between 2012 and 2020 at three first-class tertiary hospitals in southern China based on multilocus sequence typing (MLST), spa typing, and staphylococcal cassette chromosome mec (SCCmec) typing. Overall, 13 clonal complexes (CCs) were identified, with CC59 and CC5 being the largest clusters, indicating high genetic diversity among BSI-causing MRSA isolates. ST59 was the most prevalent MLST type (22.1%). ST5/ST764-MRSA SCCmec II was the predominant adult MRSA clone, whereas ST59-MRSA SCCmec IV was the most common pediatric MRSA clone. ST5-t2460, ST764-t1084, and ST59-t437 were the most common types of adult MRSA isolates, whereas ST59-t437 and ST59-t172 were the predominant types of children's MRSA isolates. ST59-SCCmec IV/V represented the most common clone among community acquired-MRSA isolates. ST5/ST764-SCCmec II was the most common type of hospital-associated MRSA isolate. The most prevalent toxin-encoding genes detected were hla, hld, icaA, and clfA (96.1-100%). Forty-three (100%, 43/43) isolates harbored more than 18 of the tested virulence genes in adults and eight virulence genes (23.5%, 8/34) in children. Virulence gene analysis revealed diversity among different clones: the positivity rates for the Panton-Valentine leukocidin (PVL) gene were 55.8 and 35.3% in adult and pediatric MRSA isolates, respectively; the genes seb-sei were present in all adult strains; seb-seg-sei-seo were present in all ST5, ST59, ST15, ST45, and ST22 adult strains; and seg-sei-sem-sen-seo were present in different clones, including ST15, ST45, and ST22 adult MRSA isolates and ST25, ST30, ST546, and ST72 children's MRSA isolates. Adult MRSA isolates had significantly higher antibiotic resistance rates and virulence gene prevalence than pediatric MRSA isolates. For 8 years, this study provided epidemiological data on the molecular characteristics and virulence genes in different groups of MRSA BSI in China. Our findings may provide critical information for a better understanding of MRSA BSI.

Zhao R ，Wang X ，Wang X ，Du B ，Xu K ，Zhang F ，Jiang C ，Zhao Y ，Zhu Y ... -  《Frontiers in Microbiology》