Since the first report of blaNDM-1, 16 blaNDM variants have been identified among Gram-negative bacteria worldwide. Recently, a novel blaNDM variant, blaNDM-13, was identified in the chromosome of an ST101 Escherichia coli isolate from Nepal. Here we first reported plasmid-mediated blaNDM-13 in a carbapenem-resistant E. coli ST5138 clinical isolate associated with hospital-acquired urinary tract infection from China. blaNDM-13 and blaSHV-12 coexisted on the a ~54 Kb self-transferable plasmid. Compared with NDM-1, NDM-13, NDM-3, and NDM-4 had two amino acid substitutions (D95N and M154L), one amino acid substitution (D95N) and one amino acid substitutions (M154L), respectively. Complete plasmid sequencing showed that blaNDM-13-harboring plasmid (pNDM13-DC33) was highly similar to the blaNDM-1-harboring IncX3 plasmid pNDM-HN380, a common blaNDM-harboring vector circulating in China. In accordance with the structure of pNDM-HN380, pNDM13-DC33 consists of a 33-kb backbone encoding plasmid replication (repB), stability partitioning, and transfer (tra, trb, and pil) functions, and a 21-kb antimicrobial resistance region with high GC content between umuD and mpr genes. In conclusion, the present study is the first report of a plasmid-encoded blaNDM-13 and the complete sequence of a blaNDM-13-harboring plasmid (pNDM13-DC33). blaNDM-13 maybe originate from blaNDM-1 located on a pNDM-HN380-like plasmid by sequential mutations.

A distinctive syndrome caused by hypermucoviscous Klebsiella pneumoniae (HMKP) including pyogenic liver abscess (PLA) is now becoming a globally emerging disease. In the present study, 22.8% (84/369) of K. pneumoniae clinical isolates associated with various types of invasive infections were identified as HMKP, with 45.2% associated with PLA. Multivariate regression analysis showed that male patients with 41-50 years, PLA, diabetes mellitus, and hypertension were independent risk factors for HMKP infections. K2 (42.9%, 36/84) was the most common capsular serotype among HMKP isolates, followed by K1 (23.8%, 20/84). Seventy-five percentage of K1 HMKP isolates were associated with PLA, while K2 HMKP isolates accounted for more types of invasive infections. The positive rates of iutA, mrkD, aerobactin, iroN, and rmpA among HMKP isolates were significantly higher than those among non-HMKP isolates (p < 0.05). There was a correlation between magA, ybtS, alls, and wcaG and K1 isolates. Interestingly, mrkD was exclusively detected among HMKP (32.1%, 27/84) and K2 isolates (65.9%, 27/41). All K1 and K2 HMKP and non-HMKP isolates were positive for rmpA. Aerobactin was found among 95.0 and 97.5% of K1 and K2 isolates. ST23 was found to be the most prevalent ST among 69 HMKP isolates with K1, K2, K5, K20, and K57 (27.5%, 19/69) and was only found among K1 isolates. ST65 was the second most prevalent ST (26.1%, 18/69) and was also only found among K2 isolates. ST23-K1 HMKP isolates (84.2%, 16/19) were associated with PLA, while ST65-K2 isolates were correlated with more types of infections relative to ST23-K1 isolates. PFGE results showed that the homology of 84 HMKP isolates was diverse. Only five PFGE clusters with more than 75% similarity accounted for more than three isolates. These five PFGE clusters only accounted for 35 (41.7%, 35/84) isolates. In conclusion, our study first found that hypertension and male patients with 41-50 years old were independent risk factors. The composition of ST types and PFGE clusters among K. pneumoniae K2 isolates was more diverse than K1 isolates. K1 and K2 HMKP isolates had respective specific profiles of virulence-associated genes.

Multidrug resistant (MDR) Gram-negative bacterial infections are a serious threat to human health due to the lack of effective treatments. In this study, we selected 50 Gram-negative bacterial strains, including 26 strains of Klebsiella pneumoniae and 24 strains of Escherichia coli, to explore whether resveratrol and polymyxin B have a synergistic killing effect.

Polymyxin resistance caused by the plasmid-mediated mcr-1 gene in gram-negative bacilli poses a huge threat to our health. In recent years, many regions have reported that mcr-1 and β-lactamase genes can coexist in a single strain.

Methicillin-resistant Staphylococcus aureus (MRSA) ST8 strains have spread worldwide, causing outbreaks in various regions. However, this clone has only been sporadically reported in China. Consequently, detailed information regarding the phylogeny and potential virulence of S. aureus ST8 strains in China remains unknown. In this study, we characterized six ST8 strains collected from three tertiary hospitals in China, including three MRSA (MR50, MR526, and MR254) and three MSSA (H78, H849 and H863). Whole genome sequencing and phylogenetic analysis showed that the six strains formed two separate clusters, including two (MR50 and MR526) and four (MR254, H78, H849 and H863) isolates, respectively. Among them, MR50 and MR526 harboured spa t008, SCCmec IVa, arginine catabolic mobile element, and were phylogenetically close to the epidemic USA300 strains, while other four strains belonged to spa t9101 and formed a unique branch. MR254 carried a novel hybrid SCCmec element (namely SCCmec254). Same as the USA300 prototype strain LAC, the China S. aureus ST8 strains produced weak biofilms except MR254. Among them, MR254 had significantly stronger haemolysis ability and higher α-toxin levels than others, while MR526 showed comparable haemolysis and α-toxin production levels as USA300-LAC. In mouse skin abscess model, MR254 showed particularly strong invasions, accompanied by necrosis, while MR526 exhibited similar infection levels as USA300-LAC. These data suggested that the China MRSA ST8 isolates (e.g. MR254 and MR526) were highly virulent, displaying higher or similar virulence potential as the epidemic USA300 strain. Active surveillance should be enacted to closely monitor the further spread of these hyper-virulent MRSA strains in China.

The aim of this study was to investigate the genomic epidemiology of MRSA in China to identify predominant lineages and their associated genomic and phenotypic characteristics. In this study, we conducted whole-genome sequencing on 565 MRSA isolates from 7 provinces and municipalities of China between 2014 and 2020. MRSA isolates were subjected to MLST, spa typing, SCCmec typing, analysis of virulence determinants and antimicrobial susceptibility testing. Among 565 MRSA isolates tested, clonal complex (CC) 59 (31.2%), CC5 (23.4%) and CC8 (13.63%) were the major lineages, and the clonal structure was dominated by ST59-t437-IV (14.9%), ST239-t030-III (6.4%) and ST5-t2460-II (6.0%), respectively. Of note, CC8, the predominant lineage in 2014-2015, was replaced by CC59 after 2016. Interestingly, the extension and unstable structure of the CC5 population was observed, with ST5-t311-II, ST764-t1084-II, ST5-t2460-II and ST764-t002-II existing complex competition. Further analysis revealed that virulence determinant profiles and antibiograms were closely associated with the clonal lineage. The CC59 MRSA was less resistant to most tested antimicrobials and carried fewer resistance determinants. But rifampicin resistance and mupirocin resistance were closely linked with CC8 and CC5, respectively. MRSA isolates conservatively carried multiple virulence genes involved in various functions. PVL encoding genes were more common in ST338, CC30, CC398, ST8 and CC22, while tsst-1 was associated with ST5. In conclusion, the community-associated CC59-ST59-t437-IV lineage was predominant in China, with diverse clonal isolates alternately circulating in various geographical locations. Our study highlights the need for MRSA surveillance in China to monitor changes in MRSA epidemiology.

The resistance of methicillin-resistant Staphylococcus aureus (MRSA) has augmented due to the abuse of antibiotics, bringing about difficulties in the treatment of infection especially with the formation of biofilm. Thus, it is essential to develop antimicrobials. Here we synthesized a novel small-molecule compound, which we termed SYG-180-2-2 (C21H16N2OSe), that had antibiofilm activity. The aim of this study was to demonstrate the antibiofilm effect of SYG-180-2-2 against clinical MRSA isolates at a subinhibitory concentration (4 μg/ml). In this study, it was showed that significant suppression in biofilm formation occurred with SYG-180-2-2 treatment, the inhibition ranged between 65.0 and 85.2%. Subsequently, confocal laser scanning microscopy and a bacterial biofilm metabolism activity assay further demonstrated that SYG-180-2-2 could suppress biofilm. Additionally, SYG-180-2-2 reduced bacterial adhesion and polysaccharide intercellular adhesin (PIA) production. It was found that the expression of icaA and other biofilm-related genes were downregulated as evaluated by RT-qPCR. At the same time, icaR and codY were upregulated when biofilms were treated with SYG-180-2-2. Based on the above results, we speculate that SYG-180-2-2 inhibits the formation of biofilm by affecting cell adhesion and the expression of genes related to PIA production. Above all, SYG-180-2-2 had no toxic effects on human normal alveolar epithelial cells BEAS-2B. Collectively, the small-molecule compound SYG-180-2-2 is a safe and effective antibacterial agent for inhibiting MRSA biofilm.

Mupirocin, a topical antimicrobial agent, is an important component in the eradication of methicillin-resistant Staphylococcus aureus (MRSA) colonization. The molecular characteristics of 46 mupirocin-resistant MRSA (MR-MRSA) clinical isolates were analyzed by multilocus sequence typing (MLST), staphylococcal cassette chromosome mec element (SCCmec) typing, spa typing, and analysis of virulence genes. All 26 MRSA isolates with low-level mupirocin resistance possessed a V588F mutation in ileS. Among 20 MRSA isolates with high-level resistance to mupirocin, all carried mupA; 2 isolates also possessed the V588F mutation in ileS, and 1 possessed the V631F mutation in ileS (isoleucyl-tRNA synthetase). The majority of MR-MRSA isolates were resistant to erythromycin, clindamycin, tetracycline, ciprofloxacin, and gentamicin, but the rates of resistance to rifampin and fusidic acid were 8.7% and 6.5%, respectively. Eight sequence types (STs) were found among the 46 MR-MRSA isolates, of which ST764 was the most prevalent (76.1%). The most frequent spa type identified was t1084 (52.2%). The SCCmec type most frequently found was type II (80.4%). The most common clone among low-level MR-MRSA isolates was ST764-MRSA-SCCmec type II-t1084 (23 isolates), while ST764-MRSA-SCCmec type II-t002 (9 isolates) was the most common clone among high-level MR-MRSA isolates. Additionally, all toxin genes except the seb gene were not identified among ST764 isolates. Among clonal complex 5 (CC5) isolates, immune evasion cluster (IEC)-associated genes (chp, sak, and scn) and seb were present in ST764 but absent in ST5, while sec, sel1, tsst-1, and hlb genes were identified in ST5 but absent in ST764. In conclusion, the spread of CC5 clones, especially a novel ST764-MRSA-SCCmec type II-t1084 clone with high-level resistance to mupirocin, was responsible for the increase in mupirocin resistance. These findings indicated that the emergence of the ST764 MR-MRSA clone involves a therapeutic challenge for treating serious MRSA infections. IMPORTANCE Mupirocin, a topical antibiotic that is commonly used for the nasal decolonization of MRSA and methicillin-sensitive Staphylococcus aureus in hospital settings and nursing homes, was introduced as a highly effective antibiotic against MRSA. Mupirocin acts by competitively binding isoleucyl-tRNA synthetase, thereby disrupting protein synthesis. This drug shows bacteriostatic and bactericidal activity at low and high concentrations, respectively. However, with the increase in mupirocin use, low-level and high-level resistance during nasal mupirocin treatment has been reported. In a previous study, the proportion of MRSA strains with high-level mupirocin resistance in a Canadian hospital increased from 1.6% in the first 5 years of surveillance (1995 to 1999) to 7.0% (2000 to 2004).

The 16S rRNA methylase-mediated high-level resistance to aminoglycosides has become a great concern. The purpose of the study was to investigate the occurrence of 16S rRNA methyltransferase (RMTase) genes in carbapenem-resistant Klebsiella pneumoniae (CRKP) clinical isolates associated with bloodstream infections (BSIs) in China.

Members of the Mycobacterium abscessus complex (MABC) are multidrug-resistant nontuberculous mycobacteria and increasingly cause opportunistic pulmonary infections. However, the genetic typing of MABC isolates remains largely unclear in China. Genomic analyses were conducted for 69 MABC clinical isolates obtained from patients with lower respiratory tract infections in Shanghai Pulmonary Hospital between 2014 and 2016. The draft genomes of the 69 clinical strains were assembled, with a total length of 4.5 to 5.6 Mb, a percent GC content (GC%) ranging from 63.9 to 68.1%, and 4,492 to 5,404 genes per genome. Susceptibility test shows that most isolates are resistant to many antimicrobials, including clarithromycin, but susceptible to tigecycline. Analyses revealed the presence of genes conferring resistance to antibiotics, including macrolides, aminoglycosides, rifampicin, and tetracyclines. Furthermore, 80 to 114 virulence genes were identified per genome, including those related to the invasion of macrophages, iron incorporation, and avoidance of immune clearance. Mobile genetic elements, including insertion sequences, transposons, and genomic islands, were discovered in the genomes. Phylogenetic analyses of all MABC isolates with another 41 complete MABC genomes identified three clades; 46 isolates were clustered in clade I, corresponding to M. abscessus subsp. abscessus, and 25 strains belonged to existing clonal complexes. Overall, this is the first comparative genomic analysis of MABC clinical isolates in China. These results show significant intraspecies variations in genetic determinants encoding antimicrobial resistance, virulence, and mobile elements and controversial subspecies classification using current marker gene combinations. This information will be useful in understanding the evolution, antimicrobial resistance, and pathogenesis of MABC strains and facilitating future vaccine development and drug design. IMPORTANCE Over the past decade, infections by Mycobacterium abscessus complex (MABC) isolates have been increasingly reported worldwide. MABC strains often show a high incidence in cystic fibrosis (CF) patients, whereas in Asia, these strains are frequently recovered from non-CF patients with significant genomic diversity. The present work involves analyses of the antimicrobial resistance, virulence, and phylogeny of 69 selected MABC isolates from non-CF pulmonary patients in Shanghai Pulmonary Hospital by whole-genome sequencing; it represents the first comprehensive investigation of MABC strains in China at the genomic level. These findings highlight the diversity of this group of nontuberculous mycobacteria and provide a mechanistic understanding of evolution and pathogenesis, which is valuable for the development of novel and effective antimicrobial therapies for deadly MABC infections in China.

ABSTRACTThe World Health Organization has identified high-priority target product profiles for new TB diagnostics which include rapid biomarker-based, non-sputum-based diagnostic testing, using an easily accessible sample. The Cepheid 3-gene Host Response Fingerstick Blood Prototype Test (MTB-HR) quantifies relative mRNA levels of a 3-gene signature (GBP5, DUSP3, and KLF2) from a whole-blood sample on the GeneXpert platform. The objective of the present study was to evaluate the performance of the MTB-HR to distinguish between active tuberculosis (ATB), latent Mycobacterium tuberculosis infection (LTBI), other pulmonary diseases, and healthy volunteers at a tertiary care centre. Among 653 participants enrolled in this study, 192 were diagnosed as having ATB, and the remaining 461 were classified as non-ATB, including 137 cases of LTBI, 224 cases of other pulmonary diseases, and 100 healthy volunteers. The corresponding AUCs of the MTB-HR in distinguishing untreated ATB from non-ATB, LTBI, other pulmonary diseases, and healthy volunteers were 0.814 (95% CI, 0.760-0.868, sensitivity 76.1%, specificity 71.6%), 0.739 (95% CI, 0.667-0.812, sensitivity 59.7%, specificity 78.1%), 0.825 (95% CI, 0.770-0.880, sensitivity 82.1%, specificity 65.6%), 0.892 (95% CI, 0.839-0.945, sensitivity 76.1%, specificity 88.0%), respectively. When only samples with TAT of less than 1 h were included, the AUC of the MTB-HR in distinguishing untreated ATB from non-ATB was largest, 0.920 (95% CI, 0.822-1.000, sensitivity 81.3%, specificity 87.7%). In conclusion, the MTB-HR assay shows potential as a rapid, blood-based screening and triage test for ATB, especially for untreated ATB, with the advantage of increased diagnostic yield since blood is more readily available.

CapB2 is recognized as a tyrosine kinase and is likely a vital factor in extracellular polysaccharide synthesis in Staphylococcus aureus, but its pathogenicity function and regulatory mechanism remain obscure. Here, we demonstrate that CapB2 enhances bacterial virulence in a murine model. Mice infected with the wild type SA75 strain exhibited significantly larger (P < 0.05) skin lesions from days 4 to 7 of infection than those challenged with the capB2 mutant strain. The effect on virulence was reverted by restoring the capB2 mutation to the wild type. The related components of the wild type SA75 cell wall in the capB2 mutant strain (SA75ΔcapB2) were thinner than wild type SA75 strain and the capB2 mutant complemented strain (SA75ΔcapB2-C), which was determined by the transmission electron microscopy. The survival percentages of the wild type strain SA75 and SA75ΔcapB2-C were significantly higher relative to SA75ΔcapB2. The results of qRT-PCR studies also indicated that mutations in regulatory gene sarA led to a drastic increase in capB2 gene transcription, with a 326-fold increase of growth at 6 h compared with the wild type strain, suggesting that sarA is a major negative regulator of capB2 expression. Taken together, these results demonstrate that the expression of CapB2 promotes S. aureus virulence in a mouse model of skin infection, and that capB2 gene transcription is regulated negatively by SarA.

Methicillin-resistant Staphylococcus aureus (MRSA) sequence type 45 (ST45) was rarely found in China. This study was conducted to trace the transmission and evolution of emerging MRSA ST45 strains in mainland China and explore its virulence. A total of 27 ST45 isolates were included for whole-genome sequencing and genetic characteristic analysis. Epidemiological results showed that MRSA ST45 isolates were often obtained from blood, primarily originated in Guangzhou, and carried diverse virulence and drug resistance genes. Staphylococcal cassette chromosome mec type IV (SCCmec IV) dominated in MRSA ST45 (23/27, 85.2%). ST45-SCCmec V was located on a phylogenetic clade distinct from the SCCmec IV cluster. We selected two representative isolates, MR370 (ST45-SCCmec IV) and MR387 (ST45-SCCmec V), and performed hemolysin activity, a blood killing assay, a Galleria mellonella infection model, and a mouse bacteremia model, as well as real-time fluorescence quantitative PCR. MR370 was proved to have extreme virulence in the phenotypic assays and at the mRNA level compared with ST59, ST5, and USA300 MRSA strains. MR387 was comparable to USA300-LAC on the phenotype and was verified to have higher expression of scn, chp, sak, saeR, agrA, and RNAIII than USA300-LAC. The results emphasized the extraordinary performance of MR370 and the good potential of MR387 in virulence causing bloodstream infection. Meanwhile, we conclude that China MRSA ST45 showed two different clonotypes, which may be widespread in the future. The entire study is valuable as a timely reminder and reports virulence phenotypes of China MRSA ST45 for the first time. IMPORTANCE Methicillin-resistant Staphylococcus aureus ST45 is epidemic worldwide. This study contributed to the awareness of the Chinese hyper-virulent MRSA ST45 strains and served as a timely reminder of its wide dissemination of clonotypes. Further, we provide novel insights for prevention from the perspective of bloodstream infections. ST45-SCCmec V is a clonotype deserving special attention in China, and we performed genetic and phenotypic analyses for the first time on it.

ST22 MRSA (methicillin-resistant Staphylococcus aureus) strains are only sporadically reported in China. Through the phylogenetic reconstruction of 30 ST22 strains from China and 480 ST22 strains from global sources, we found that the global ST22 strains can be divided into three clades (I, II, and III). The China ST22 strains were found primarily in clade II (IIb and IIc) and also in clade III, indicating that the China ST22-MRSA clones have different origins. The China subclade IIb strains (SCCmec Vb-t309) may evolve from the native ST22 MSSA clone, while the China IIc strains may have spread from other countries. Subclade IIc (SCCmecIVa-t309) strains exhibited particularly strong lethality and invasiveness in Galleria mellonella infection and mouse skin abscess models in comparison to USA300 and other dominant China HA-MRSA (ST5 and ST239) or CA-MRSA (ST59) strains. This study described the emergence of a highly virulent ST22 MRSA subclade and improved our insight into the molecular epidemiology of ST22 strains in China. IMPORTANCE ST22 is a successful hospital-associated MRSA lineage which first appeared in the United Kingdom as EMRSA-15. At present, ST22 MRSA clones are spreading rapidly around the world and even replaced other dominant clones in some regions. We placed the Chinese ST22 in the worldwide phylogeny of ST22, demonstrating a distinctive molecular epidemiology and to our knowledge, this is the first time that a novel clade of ST22 has been found in China. Among the 15 ST22 MRSA strains belonging to the novel clade, 14 ST22 SCCmecIVa strains from different regions carried both pvl and tst and displayed significantly higher in vitro and in vivo virulence in comparison to other clade/subclade ST22 strains as well as other common China HA-MRSA or CA-MRSA strains. The further spread of this subclade of strains could pose a serious threat to the health system in China and other regions.

The emergence of carbapenem-resistant Klebsiella pneumoniae (CRKP) strains and restricted therapeutic options pose a global threat to public health. Aminoglycosides are a wise choice, which can effectively reduce the mortality rate when combined with β-lactam drugs. However, in this study, we identified a ST15-KL112 CRKP FK3006 which not only exhibited resistance to carbapenems, but also exhibited high level resistance to aminoglycosides. In addition to the multidrug resistant phenotype, FK3006 also owned typical pathogenic characteristic, including hypermucoviscosity and hypervirulence phenotypes. According to the whole-genome sequencing, one pLVPK-like virulence plasmid, and three key resistant plasmids (bla OXA-232, bla CTX-M-15, and rmtF) were observed in FK3006. Compared to other typical ST15 CRKP, the presence of pLVPK-like virulence plasmid (p3006-2) endowed the FK3006 with high virulence features. High siderophore production, more cell invasive and more resistant to serum killing was observed in FK3006. The Galleria mellonella infection model also further confirmed the hypervirulent phenotype of FK3006 in vivo. Moreover, according to the conjugation assay, p3006-2 virulence plasmid also could be induced transfer with the help of conjugative IncFIIK p3006-11 plasmid (bla CTX-M-15). In addition to the transmissible plasmid, several insertion sequences and transposons were found around bla CTX-M-15, and rmtF to generate the mobile antimicrobial resistance island (ARI), which also make a significant contribution to the dissemination of resistant determinants. Overall, we reported the uncommon co-existence of bla OXA-232, rmtF-encoding plasmids, and pLVPK-like virulence plasmid in ST15-KL112 K. pneumoniae. The dissemination threatens of these high-risk elements in K. pneumoniae indicated that future studies are necessary to evaluate the prevalence of such isolates.

Staphylococcus aureus is the most important pathogenic bacteria in humans. As the resistance of S. aureus to existing antibiotics is increasing, there is an urgent need for new anti-infective drugs. S. aureus biofilms cause persistent infections and resist complete eradication with antibiotic therapy. The present study investigated the inhibitory effect of the novel small-molecule ZY-214-4 (C1 9H1 1BrNO4) on S. aureus biofilm formation. At a subinhibitory concentration (4 μg/ml), ZY-214-4 had no effect on the growth of S. aureus strains and also showed no cytotoxicity in human normal bronchial epithelial cells (Bease-2B). The results of a semi-quantitative biofilm test showed that ZY-214-4 prevented S. aureus biofilm formation, which was confirmed by scanning electron microscopy and confocal laser scanning microscopy. ZY-214-4 significantly suppressed the production of polysaccharide intercellular adhesion and prevented cell aggregation, and also inhibited the mRNA expression of icaA and other biofilm-related genes (eno, clfA/B, fnbB, fib, ebpS, psmα, and psmβ) in clinical S. aureus isolates. Thus, at a subinhibitory concentration, ZY-214-4 inhibits biofilm formation by preventing cell aggregation, highlighting its clinical potential for preventing or treating S. aureus infections.

The ability of Staphylococcus aureus to form biofilms is associated with high mortality and treatment costs. Established biofilms cannot be eradicated by many conventional antibiotics due to the development of antibiotic tolerance by S. aureus. Here we report the synthesis and biological characterization of novel small-molecule compounds with antibiofilm activity. Chromone 5-maleimide substitution compounds (CM3a) showed favorable antibacterial activity against S. aureus.

Mycobacterium kansasii, an important opportunistic pathogen of humans, causes serious pulmonary disease. Sixty M. kansasii isolates were collected for investigating the clinical characteristics of patients with M. kansasii infections as well as drug susceptibility and genotypes of M. kansasii. More than 90% of the patients infected with M. kansasii were from eastern China. According to the internal transcribed spacers (ITS), rpoB, hsp65, and tuf, all M. kansasii isolates were classified as molecular type I, irrespective of the disease manifestation. Sixty M. kansasii isolates from China were diverse and separated into four branches. Pairwise average nucleotide identity (ANI) values for M. kansasii isolates affiliated with different genotypes were more than 85%. The earliest isolate was isolated from Jiangsu in 1983. Of the isolates, 78.3% (47/60) were isolated since 1999. All isolates were sensitive to rifabutin. All but one isolate was sensitive to clarithromycin. Sensitivity rates to rifampin, amikacin, moxifloxacin, and linezolid were 80.0%, 90.0%, 88.3%, and 91.7%, respectively. A high rate of resistance was noted for ciprofloxacin (44 isolates, 73.3%) and ethambutol (46 isolates, 76.7%). Compared with M. tuberculosis H37Rv, 12 mutations of embCA were observed in all M. kansasii isolates. All these 60 M. kansasii isolates shared identical sequences of rpoB, inhA, katG, rrl, rrs, rpsL, gyrA, and gyrB. In conclusion, M. kansasii isolates are exhibiting greater genetic diversity globally. The resistance mechanism of M. kansasii is not necessarily related to gene mutation. IMPORTANCE M. kansasii type I is the main genotype spreading worldwide. The molecular history of the global spread of type I isolates remains largely unclear. We conducted a detailed analysis of genomic evolution of global M. kansasii isolates. Our results suggest that M. kansasii isolates exhibit greater genetic diversity globally.

In recent years, multidrug-resistant methicillin-resistant Staphylococcus aureus has become increasingly prevalent, which raised a huge challenge to antibiotic treatment of infectious diseases. The anti-virulence strategy targeting virulent factors is a promising novel therapy for S. aureus infection. The virulence mechanism of S. aureus was needed to explore deeply to develop more targets and improve the effectiveness of anti-virulence strategies.

Carbapenem-resistant Enterobacterales (CRE) infection is highly endemic in China; Klebsiella pneumoniae carbapenemase (KPC) 2-producing CRE is the most common, whereas KPC-3-producing CRE is rare. We report an outbreak of KPC-3-producing Enterobacterales infection in China. During August 2020-June 2021, 25 blaKPC-3-positive Enterobacteriale isolates were detected from 24 patients in China. Whole-genome sequencing analysis revealed that the blaKPC-3 genes were harbored by IncX8 plasmids. The outbreak involved clonal expansion of KPC-3-producing Serratia marcescens and transmission of blaKPC-3 plasmids across different species. The blaKPC-3 plasmids demonstrated high conjugation frequencies (10-3 to 10-4). A Galleria mellonella infection model showed that 2 sequence type 65 K2 K. pneumoniae strains containing blaKPC-3 plasmids were highly virulent. A ceftazidime/avibactam in vitro selection assay indicated that the KPC-3-producing strains can readily develop resistance. The spread of blaKPC-3-harboring IncX8 plasmids and these KPC-3 strains should be closely monitored in China and globally.