Clonal Diversity, Antimicrobial Susceptibility and Presence of Genes Encoding Virulence Factors in Staphylococcus aureus Strains Isolated from Cut Wound Infections

Multi-Omics Integrative Analysis to Reveal the Impacts of Shewanella algae on the Development and Lifespan of Marine Nematode Litoditis marina

Understanding how habitat bacteria affect animal development, reproduction, and aging is essential for deciphering animal biology. Our recent study showed that Shewanella algae impaired Litoditis marina development and lifespan, compared with Escherichia coli OP50 feeding; however, the underlying mechanisms remain unclear. Here, multi-omics approaches, including the transcriptome of both L. marina and bacteria, as well as the comparative bacterial metabolome, were utilized to investigate how bacterial food affects animal fitness and physiology. We found that genes related to iron ion binding and oxidoreductase activity pathways, such as agmo-1, cdo-1, haao-1, and tdo-2, were significantly upregulated in L. marina grown on S. algae, while extracellular structural components-related genes were significantly downregulated. Next, we observed that bacterial genes belonging to amino acid metabolism and ubiquinol-8 biosynthesis were repressed, while virulence genes were significantly elevated in S. algae. Furthermore, metabolomic analysis revealed that several toxic metabolites, such as puromycin, were enriched in S. algae, while many nucleotides were significantly enriched in OP50. Moreover, we found that the "two-component system" was enriched in S. algae, whereas "purine metabolism" and "one-carbon pool by folate" were significantly enriched in E. coli OP50. Collectively, our data provide new insights to decipher how diet modulates animal fitness and biology.

Prevalence of Selected Immune Evasion Genes and Clonal Diversity in Methicillin-Susceptible Staphylococcus aureus Isolated from Nasal Carriers and Outpatients with Cut Wound Infections

Staphylococcus aureus, being one of the most common human pathogens, is responsible for infections in both hospital and community settings. Its virulence is attributed to its ability to evade the immune system by producing immune evasion (IE) proteins. The aim of this study was to detect the frequency of selected IE genes (spin, sbi, sea, sak, chp, scin, sep, ecb), belonging to the immune evasion cluster (IEC), and IEC types in 86 methicillin-susceptible S. aureus (MSSA) strains isolated from unrelated outpatients. In order to determine the diversity of analyzed strains, the phylogenetic relatedness was also determined. All strains were examined for the presence of IE genes using polymerase chain reaction assay. To analyze the clonal relatedness of S. aureus, pulsed-field gel electrophoresis (PFGE) was performed. All analyzed strains harbored the scn gene, followed by sbi (95.4%), ecb (91.7%), spin (89.5%), sak (83.7%), chp (67.4%), sep (67.4%) and sea (5.8%). Seventy-three (84.9%) S. aureus strains were classified into IEC types, of which, IEC type F was most commonly observed. IEC type A was not detected. PFGE results showed no association between clonal relatedness and the presence of IE genes/IEC types. In conclusion, the abundant and so diverse repertoire of genes determining invasion in analyzed strains may prove the fact that these strains are highly advanced and adapted to evade the host immune response.

Loop-Mediated Isothermal Amplification of DNA (LAMP) as an Alternative Method for Determining Bacteria in Wound Infections

The increasing number of patients with chronic wounds requires the development of quick and accurate diagnostics methods. One of the key and challenging aspects of treating ulcers is to control wound infection. Early detection of infection is essential for the application of suitable treatment methods, such as systemic antibiotics or other antimicrobial agents. Clinically, the most frequently used method for detecting microorganisms in wounds is through a swab and culture on appropriate media. This test has major limitations, such as the long bacterial growth time and the selectivity of bacterial growth. This article presents an overview of molecular methods for detecting bacteria in wounds, including real-time polymerase chain reaction (rtPCR), quantitative polymerase chain reaction (qPCR), genotyping, next-generation sequencing (NGS), and loop-mediated isothermal amplification (LAMP). We focus on the LAMP method, which has not yet been widely used to detect bacteria in wounds, but it is an interesting alternative to conventional detection methods. LAMP does not require additional complicated equipment and provides the fastest detection time for microorganisms (approx. 30 min reaction). It also allows the use of many pairs of primers in one reaction and determination of up to 15 organisms in one sample. Isothermal amplification of DNA is currently the easiest and most economical method for microbial detection in wound infection. Direct visualization of the reaction with dyes, along with omitting DNA isolation, has increased the potential use of this method.

GehB Inactivates Lipoproteins to Delay the Healing of Acute Wounds Infected with Staphylococcus aureus

Staphylococcus aureus is one of the most prevalent bacteria found in acute wounds. S. aureus produces many virulence factors and extracellular enzymes that contribute to bacterial survival, dissemination, and pathogenicity. Lipase GehB is a glycerol ester hydrolase that hydrolyzes triglycerides to facilitate the evasion of S. aureus from host immune recognition. However, the role and mechanism of lipase GehB in skin acute wound healing after S. aureus infection remain unclear. In this study, we found that the gehB gene deletion mutant (USA300ΔgehB) stimulated significantly higher levels of pro-inflammatory cytokines in RAW264.7 and Toll-like receptor 2 (TLR2)-transfected HEK293 cells than the wild-type USA300 strain did. Recombinant GehB-His treated lipoprotein (Lpp) reduced stimulation of TLR2-dependent TNF-α production by RAW264.7 macrophages. GehB delayed the skin acute wound healing in BALB/c mice infected with S. aureus, while wound healing was similar in C57BL/6 TLR2-/- mice infected with either wild-type USA300 or USA300ΔgehB. In BALB/c mice, we also observed more bacterial survival, less leukocyte recruitment, lower IL-8 production, and adipocyte differentiation in USA300-infected skin acute wound tissues than those in USA300ΔgehB-challenged ones. Our data indicated that GehB inactivates lipoproteins to shield S. aureus from innate immune killing, resulting in delayed the healing of skin acute wounds infected with S. aureus.