Virulence Factor Genes and Antimicrobial Susceptibility of Staphylococcus aureus Strains Isolated from Blood and Chronic Wounds

Helicid: A novel Anti-Staphylococcus aureus adjuvant

Staphylocoagulase (Coa) plays a critical role in the pathogenicity of Staphylococcus aureus (S. aureus). The present study was undertaken to investigate the underlying mechanism which helicid (HEL) suppressed the virulence factor Coa, as well as to assess the synergistic inhibitory effects of HEL in conjunction with antibiotics, thereby establishing the potential of HEL as an antibacterial adjuvant. We employed coagulation and biofilm assays to comprehensively assess the inhibitory impact of HEL on S. aureus pathogenicity. The thermal shift assay demonstrated that HEL exerted a direct impact on the protein stability of Coa, evidenced by a 6 °C change in melting temperature (ΔTm) at a concentration of 100 μM. HEL binding to Coa proteins was further validated by molecular dynamics simulations and fluorescence quenching. Molecular docking and point mutation assays identified S23 and D112 as crucial binding sites for HEL and Coa. Furthermore, HEL has been observed to potentiate the bactericidal properties of ceftaroline fosamil (CEF-F), concurrently diminishing the resistance exhibited by S. aureus towards CEF-F, as demonstrated by antibiotic synergy tests and resistance induction assays. The combination of HEL and CEF-F effectively reduced the number of bacteria and improved the survival of both Galleria mellonella larvae and mice. Additionally, a significant decrease was observed in the levels of TNF-α, IL-6, and IFN-γ in mice broncho-alveolar lavage fluid (BALF). Ultimately, our findings confirmed that the direct binding of HEL to Coa could diminish the pathogenicity of S. aureus. Moreover, the combination with CEF-F substantially reduced the lethality associated with S. aureus-infected pneumonia and extended the efficacy of the antibiotic.

Surface-Shaving of Staphylococcus aureus Strains and Quantitative Proteomic Analysis Reveal Differences in Protein Abundance of the Surfaceome

Staphylococcus aureus is a pathogen known to cause a wide range of infections. To find new targets for identification and to understand host-pathogen interactions, many studies have focused on surface proteins. We performed bacterial-cell surface-shaving, followed by tandem mass tag for quantitative mass spectrometry proteomics, to examine the surfaceome of S. aureus. Two steps were performed, the first step including surface protein-deficient mutants of S. aureus Newman strain lacking important virulence genes (clfA and spa, important for adhesion and immune evasion and srtAsrtB, linking surface-associated virulence factors to the surface) and the second step including isolates of different clinical origin. All strains were compared to the Newman strain. In Step 1, altogether, 7880 peptides were identified, corresponding to 1290 proteins. In Step 2, 4949 peptides were identified, corresponding to 919 proteins and for each strain, approximately 20 proteins showed differential expression compared to the Newman strain. The identified surface proteins were related to host-cell-adherence and immune-system-evasion, biofilm formation, and survival under harsh conditions. The results indicate that surface-shaving of intact S. aureus bacterial strains in combination with quantitative proteomics is a useful tool to distinguish differences in protein abundance of the surfaceome, including the expression of virulence factors.

Switchable adhesive films of pullulan loaded with a deep eutectic solvent-curcumin formulation for the photodynamic treatment of drug-resistant skin infections

Antimicrobial photodynamic therapy (aPDT) is a potent tool to surpass the global rise of antimicrobial resistance; still, the effective topical administration of photosensitizers remains a challenge. Biopolymer-based adhesive films can safely extend the residence time of photosensitizers. However, their wide application is narrowed by their limited water absorption capacity and gel strength. In this study, pullulan-based films with a switchable character (from a solid film to an adhesive hydrogel) were developed. This was accomplished by the incorporation of a betaine-based deep eutectic solvent (DES) containing curcumin (4.4 μg.cm-2) into the pullulan films, which tuned the films' skin moisture absorption ability, and therefore they switch into an adhesive hydrogel capable of delivering the photosensitizer. The obtained transparent films presented higher extensibility (elongation at break up to 338.2%) than the pullulan counterparts (6.08%), when stored at 54% of relative humidity, and the corresponding hydrogels a 4-fold higher adhesiveness than commercial hydrogels. These non-cytotoxic adhesives allowed the inactivation (∼5 log reduction), down to the detection limit of the method, of multiresistant strains of Staphylococcus aureus in ex vivo skin samples. Overall, these materials are promising for aPDT in the treatment of resistant skin infections, while being easily removed from the skin.

Spectrum of Virulence Factors in Clinical Isolates of Staphylococcus aureus and Prevalence of SCCmec Types in Methicillin-Resistant Staphylococcus aureus in a Tertiary Care Center

Background  Methicillin-resistant Staphylococcus aureus (MRSA) is a widely recognized multidrug-resistant bacteria presenting a major therapeutic challenge to clinicians. Staphylococcus aureus possesses a number of pathogenicity factors that attribute to the severity of infections. This study was undertaken to investigate the common virulence genes in clinical isolates of Staphylococcus aureus , determine their antimicrobial susceptibility profile, and to characterize the staphylococcal cassette chromosome mec (SCCmec) types among MRSA in a tertiary care center. Materials and Methods  A total of 133 clinical isolates were included in this study. Susceptibility to various antibiotics was determined by disc diffusion method. Methicillin resistance was screened using cefoxitin disc; m ecA and mecC genes were detected using polymerase chain reaction (PCR). PCR was done to detect 12 virulence factors such as hla , hlb , fnbA , fnbB , sea , seb , sec , icaA , clfA , tst , pvl, and eta . SCCmec typing was done by multiplex PCR. Results  Of the 133 clinical isolates, 54 (40.6%) were MRSA. The most common virulence gene detected was hlb (61.6%), hla (39%), and fnbA (37%). SCCmec type I was the most predominant. Mortality rate of 6.7% was observed among patients with staphylococcal infections. Univariate analysis of mortality associated virulence genes did not reveal any significant association between virulence genes and mortality. Conclusion  The distribution of virulence genes is similar in both MRSA and methicillin-sensitive Staphylococcus aureus . MRSA belongs to the SCCmec types I to IV. Possession of multiple virulence factors and multidrug resistance profile makes Staphylococcus aureus a formidable pathogen in clinical settings.

Methicillin-Resistant Staphylococcusaureus Strains Isolated from Burned Patients in a Tunisian Hospital: Molecular Typing, Virulence Genes, and Antimicrobial Resistance

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the major causes of a variety of infections in hospitals and the community. Their spread poses a serious public health problem worldwide. Nevertheless, in Tunisia and other African countries, very little molecular typing data on MRSA strains is currently available. In our study, a total of 64 MRSA isolates were isolated from clinical samples collected from burned patients hospitalized in the Traumatology and Burns Center of Ben Arous in Tunisia. The identification of the collection was based on conventional methods (phenotypic and molecular characterization). The characterization of the genetic support for methicillin resistance was performed by amplification of the mecA gene by polymerase chain reaction (PCR), which revealed that 78.12% of S. aureus harbors the gene. The resistance of all the collection to different antibiotic families was studied. Indeed, the analysis of strain antibiotic susceptibility confirmed their multi-resistant phenotype, with high resistance to ciprofloxacin, gentamicin, penicillin, erythromycin, and tetracycline. The resistance to the last three antibiotics was conferred by the blaZ gene (73.43%), the erm(C) gene (1.56%), the msr(A) gene (6.25%), and tet(M) gene (7.81%), respectively. The clonal diversity of these strains was studied by molecular typing of the accessory gene regulator (agr) system, characterization of the SCCmec type, and spa-typing. The results revealed the prevalence of agr types II and III groups, the SCCmec type III and II cassettes, and the dominance of spa type t233. The characterization of the eight enterotoxins genes, the Panton-Valentine leukocidin and the toxic shock syndrome toxin, was determined by PCR. The percentage of virulence genes detected was for enterotoxins (55%), tst (71.88%), leukocidin E/D (79.69%), and pvl (1.56%) factors. Furthermore, our results revealed that the majority of the strains harbor IEC complex genes (94%) with different types. Our findings highlighted the emergence of MRSA strains with a wide variety of toxins, leukocidin associated with resistance genes, and specific genetic determinants, which could constitute a risk of their spread in hospitals and the environment and complicate infection treatment.

Screening of Staphylococcus aureus for Disinfection Evaluation and Transcriptome Analysis of High Tolerance to Chlorine-Containing Disinfectants

The nonstandard use of disinfectants can lead to the disinfectant resistance of bacteria and even increase antibiotic resistance. However, compared with the study of antibiotic resistance, studies of bacterial resistance to disinfectants are relatively few in number. In this study, we explored the standard strain screening procedure for the evaluation of disinfection efficacy. Staphylococcus aureus strains with different sources and substrates were selected from the National Pathogen Resource Center of China and screened the standard strains that could evaluate the long-term bacteriostatic effect of the chlorine-containing disinfectants through the determination of the physical properties, genome-based safety evaluation, and disinfection test evaluation. In this process, one S. aureus strain was more resistant to the long-term bacteriostasis of chlorine-containing disinfectants than the other strains. This strain and the standard strain ATCC 6538 were cultured in the medium containing a low concentration of chlorine-containing disinfectant synchronously. Then, comparative transcriptome analysis was carried out to investigate the potential mechanism of a high tolerance to chlorine-containing disinfectants. The pathway of significant differential expression is related to the oxocarboxylic acid metabolic mechanism, amino acid metabolic mechanism, and pyrimidine mechanism, which may be the molecular mechanism of S. aureus evolution to adapt to chlorine-containing disinfectants. Our study established a technical process for screening and evaluating standard strains for disinfection, which also provided a reference for studying the bacterial evolution mechanism toward chlorine tolerance.

Antimicrobial and Biofilm-Preventing Activity of l-Borneol Possessing 2(5H)-Furanone Derivative F131 against S. aureus—C. albicans Mixed Cultures

Candida albicans and Staphylococcus aureus are human pathogens that are able to form mixed biofilms on the surface of mucous membranes, implants and catheters. In biofilms, these pathogens have increased resistance to antimicrobials, leading to extreme difficulties in the treatment of mixed infections. The growing frequency of mixed infections caused by S. aureus and C. albicans requires either the development of new antimicrobials or the proposal of alternative approaches to increase the efficiency of conventional ones. Here, we show the antimicrobial, biofilm-preventing and biofilm-eradicating activity of 2(5H)-furanone derivative F131, containing an l-borneol fragment against S. aureus-C. albicans mixed biofilms. Furanone F131 is also capable of inhibiting the formation of monospecies and mixed biofilms by S. aureus and C. albicans. The minimal biofilm-prevention concentration (MBPC) of this compound was 8-16 μg/mL for S. aureus and C. albicans mono- and two-species biofilms. While the compound demonstrates slightly lower activity compared to conventional antimicrobials (gentamicin, amikacin, fluconazole, terbinafine and benzalkonium chloride), F131 also increases the antimicrobial activity of fluconazole-gentamicin and benzalkonium chloride against mixed biofilms of S. aureus-C. albicans, thus reducing MBPC of fluconazole-gentamicin by 4-16 times and benzalkonium chloride twofold. F131 does not affect the transcription of the MDR1, CDR1 and CDR2 genes, thus suggesting a low risk of micromycete resistance to this compound. Altogether, combined use of antibiotics with a F131 could be a promising option to reduce the concentration of fluconazole used in antiseptic compositions and reduce the toxic effect of benzalkonium chloride and gentamicin. This makes them an attractive starting point for the development of alternative antimicrobials for the treatment of skin infections caused by S. aureus-C. albicans mixed biofilms.