Shih-Cheng Chang

Lugdunin, produced by Staphylococcus lugdunensis , exhibits potent antimicrobial activity against a broad range of Gram-positive bacteria, including Staphylococcus aureus . This study aims to elucidate the mechanisms underlying the susceptibility of S. aureus to lugdunin by screening a transposon-based mutant library generated using the lugdunin-susceptible S. aureus strain HG001. We identified four S . aureus mutants with mutations in ctaA , hemY , qoxA , and guaB , which are involved in ATP and GTP synthesis, and displayed increased susceptibility to S. lugdunensis . Further tests using synthetic lugdunin confirmed that energy generation defects make S. aureus more susceptible to lugdunin. Moreover, these mutants displayed small colony variant (SCV) phenotypes, a slow-growing form of S. aureus characterized by altered metabolism, revealing the critical role of energy metabolism in S. aureus defense mechanisms. Furthermore, we observed that clinical SCV isolates exhibited greater susceptibility to lugdunin compared to their parental strains. Additionally, lugdunin treatment enhanced SCV susceptibility to commonly used antibiotics, including oxacillin and vancomycin, suggesting a synergistic effect between lugdunin and antibiotics. This study highlights the role of lugdunin in sensitizing energy-compromised S. aureus to antibiotics, presenting a promising avenue for combating SCV-related infections. IMPORTANCE: The rise of antimicrobial resistance in Staphylococcus aureus , particularly small colony variants (SCVs), poses a significant clinical challenge due to their persistence and reduced susceptibility to antibiotics. Staphylococcus lugdunensis produces lugdunin, a potent antimicrobial compound that inhibits S. aureus growth. This study reveals that energy metabolism-deficient mutants and clinical SCVs exhibit increased susceptibility to lugdunin, underscoring the role of energy metabolism in bacterial defense. Furthermore, lugdunin enhances SCV susceptibility to antibiotics oxacillin and vancomycin, suggesting a potential strategy to overcome antibiotic resistance. By elucidating the link between energy metabolism and susceptibility to antimicrobial compounds, this study highlights lugdunin as a promising candidate for combating SCV-associated infections and antibiotic-resistant S. aureus .

Chao AS, et al. J Gynecol Oncol. 2023 Sep;35(1):e5. https://doi.org/10.3802/jgo.2024.35.e5

Lugdunin produced by Staphylococcus lugdunensis has been shown to have broad inhibitory activity against Gram-positive bacteria; however, lugdunin activity among S. lugdunensis isolates and its association with different agr , SCC mec , and sequence types remain unclear. We used matrix-assisted laser desorption ionization-time-of-flight mass spectrometry to identify S. lugdunensis and collected 202 S . lugdunensis samples for further assays. Agar spot tests were performed to characterize S. lugdunensis lugdunin production and activity. Multilocus sequence typing, SCC mec, and agr genotyping were performed on S. lugdunensis . In all, 91 S taphylococcus aureus strains with varying vancomycin susceptibilities were used to examine lugdunin activity in S. lugdunensis . In total, 48 S . lugdunensis strains (23.8%) were found to be oxacillin-resistant S. lugdunensis (ORSL), whereas 154 (76.2%) were classified as oxacillin-sensitive S. lugdunensis (OSSL). Moreover, 16 (33.3%) ORSL and 35 (22.7%) OSSL strains showed antibacterial activity against S. aureus . Our data showed that most lugdunin-producing ORSL strains (14/48, 29.2%) were of ST3-SCC mec V- agr II genotypes, whereas most lugdunin-producing OSSL strains (15/154, 9.7%) were of ST3- agr II, followed by ST1- agr I (10/154, 6.5%). Our data also revealed that lugdunin exhibited weak inhibitory activity against the VISA ST239 isolate. In addition, we observed that ST239 VSSA was more resistant to lugdunin than ST5, ST59, and ST45 VSSA. Taken together, our data pioneered the epidemiology of lugdunin production in S. lugdunensis isolates and revealed its association with genotypes. However, further molecular and bioinformatics investigations are needed to elucidate the regulatory mechanisms of lugdunin production and activity. IMPORTANCE: Lugdunin is active against both methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci by dissipating their membrane potential. However, the association of lugdunin activity with the genotypes of Staphylococcus lugdunensis has not been addressed. Here, we show the high prevalence of lugdunin-producing strains among ST1 (83.3%), ST2 (66.7%), and ST3 (53.3%) S. lugdunensis . Moreover, we identified the antibacterial activity of lugdunin-producing strains against VISA and hVISA. These results shed light on the potential application of lugdunin for the treatment of drug-resistant pathogens.

Multi-drug resistant Staphylococcus haemolyticus is a frequent nosocomial invasive bacteremia pathogen in hospitals. Our previous analysis showed one of the predominant strains, ST42 originated from ST3, had only one multilocus sequence typing (MLST) variation among seven loci in SH1431; yet no significant differences in biofilm formation observed between ST42 and ST3, suggesting that other factors influence clonal lineage change. Whole genome sequencing was conducted on two isolates from ST42 and ST3 to find phenotypic and genotypic variations, and these variations were further validated in 140 clinical isolates. The fusidic acid- and tetracycline-resistant genes (fusB and tetK) were found only in CGMH-SH51 (ST42). Further investigation revealed consistent resistant genotypes in all isolates, with 46% and 70% of ST42 containing fusB and tetK, respectively. In contrast, only 23% and 4.2% ST3 contained these two genes, respectively. The phenotypic analysis also showed that ST42 isolates were highly resistant to fusidic acid (47%) and tetracycline (70%), compared with ST3 (23% and 4%, respectively). Along with drug-resistant genes, three capsule-related genes were found in higher percentage distributions in ST42 than in ST3 isolates. Our findings indicate that ST42 could become endemic in Taiwan, further constitutive surveillance is required to prevent the spread of this bacterium.

Translocase of outer mitochondrial membrane 40 (TOMM40) is located in the outer membrane of mitochondria. TOMM40 is essential for protein import into mitochondria. TOMM40 genetic variants are believed to increase the risk of Alzheimer’s disease (AD) in different populations. In this study, three exonic variants (rs772262361, rs157581, and rs11556505) and three intronic variants (rs157582, rs184017, and rs2075650) of the TOMM40 gene were identified from Taiwanese AD patients using next-generation sequencing. Associations between the three TOMM40 exonic variants and AD susceptibility were further evaluated in another AD cohort. Our results showed that rs157581 (c.339T > C, p.Phe113Leu, F113L) and rs11556505 (c.393C > T, p.Phe131Leu, F131L) were associated with an increased risk of AD. We further utilized cell models to examine the role of TOMM40 variation in mitochondrial dysfunction that causes microglial activation and neuroinflammation. When expressed in BV2 microglial cells, the AD-associated mutant (F113L) or (F131L) TOMM40 induced mitochondrial dysfunction and oxidative stress-induced activation of microglia and NLRP3 inflammasome. Pro-inflammatory TNF-α, IL-1β, and IL-6 released by mutant (F113L) or (F131L) TOMM40-activated BV2 microglial cells caused cell death of hippocampal neurons. Taiwanese AD patients carrying TOMM40 missense (F113L) or (F131L) variants displayed an increased plasma level of inflammatory cytokines IL-6, IL-18, IL-33, and COX-2. Our results provide evidence that TOMM40 exonic variants, including rs157581 (F113L) and rs11556505 (F131L), increase the AD risk of the Taiwanese population. Further studies suggest that AD-associated mutant (F113L) or (F131L) TOMM40 cause the neurotoxicity of hippocampal neurons by inducing the activation of microglia and NLRP3 inflammasome and the release of pro-inflammatory cytokines.

Methicillin-resistant Staphylococcus lugdunensis (MRSL) strains showing resistance to several common antibiotics have been reported recently. Sequence type (ST) 3 MRSL carrying SCC mec types IV, V, or Vt is the major lineage associated with health care-associated infections.

CRISPR-Cas systems have been characterized as playing several biological roles in many bacterial genomes. Moreover, CRISPR-Cas systems are useful for epidemiological, diagnostic, and evolutionary studies of pathogenic bacteria.

Background and Purpose. Obesity is a widespread and increasingly severe problem worldwide. Several single nucleotide polymorphisms (SNPs) associated with obesity have been identified, reflecting metabolic disorders between the environment, diet, and body constitution. Traditional Chinese medicine body constitution (TCMBC) plays a central role in the classification of human body constitution from the viewpoint of traditional Chinese medicine (TCM). This study aims at exploring the relations between TCMBC and obesity-related biochemistry profiles and SNPs. Methods. The adults with body mass index (BMI) more than 27 kg/m² were enrolled in the study. General personal information, physical condition, TCMBC, biochemical, and SNPs were collected for eligible subjects. The body constitution questionnaire (BCQ) was used to evaluate the relationships between TCMBC tendency, biochemical values, and obesity-related SNPs. Results. Obesity patients tended to have a yin deficiency constitution (YinDC) (n = 33, 66.0%); however, TCMBC in combination is not uncommon (30 subjects with more than two TCMBC in combination). For biochemical profiles, leptin was higher among patients with yang deficiency constitution (YangDC) (YangDC versus non-YangDC: 29.7 ± 24.8 versus 15.9 ± 9.9, ) and YinDC (YinDC versus non-YinDC: 28.8 ± 23.5 versus 14.4 ± 9.6, ). The leptin level was highest among YangDC subjects. Higher leptin was found among subjects with three-combined TCMBC than balanced TCMBC subjects who were not inclined to any of three TCMBC. For obesity-related SNPs, the adrenergic receptor beta-3 (ADRB3) gene tended to be high expression among YangDC (YangDC versus non-YangDC: 89.7% versus 71.4%, ) and uncoupling protein 1 (UCP1) tended to be high expression among phlegm-stasis constitution (PSC) (PSC versus non-PSC: 37.9% versus 9.5%, ). Conclusions. The relationships between TCMBC, leptin, and SNPs present alternative viewpoints about TCMBC and could be used as a guide to treat obese patients.