Reduction of Panton-Valentine Leukocidin Production in the Staphylococcal Strain USA300 After In Vitro Ascorbic Acid and Nicotinamide Treatment.

Background Panton-Valentine leukocidin (PVL) is one of the most important determinants of virulence in Staphylococcus aureus. It is associated with a propensity for complicating skin and soft tissue infections and necrotizing pneumonia. This study aims to quantitively examine the effect of ascorbic acid and nicotinamide on PVL production in the reference strain USA300. Methodology Sandwich enzyme-linked immunosorbent assay (ELISA) was used to quantitively measure the production of PVL via the commercial LukS sandwich ELISA kit (IBT Bio-services, MD, USA). Results Incubating USA300 with subinhibitory concentrations of antioxidants resulted in a statistically significant eight-fold reduction in PVL production at 1.25 mg/mL and 30 mg/mL for ascorbic acid and nicotinamide, respectively. Although the mechanism by which antioxidants inhibit PVL production is yet to be elucidated, we suggest that it can be due to interrupting PVL gene expression. Conclusions Ascorbic acid and nicotinamide have the potential to be toxin-suppressing agents that may be effective in supporting the bactericidal effect of antibiotics to improve the outcome of PVL-associated infections; however, further extensive research is required.

Multidrug-Resistant Staphylococcus aureus Isolates in a Tertiary Care Hospital, Kingdom of Bahrain.

BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) is a ubiquitous pathogen associated with a wide spectrum of human infections. In recent decades, MRSA infections have been increasingly reported in individuals without established risk factors, infecting immunocompetent members of the community. This emergence is attributed to the production of various virulence factors, notably Panton-Valentine leukocidin (PVL). OBJECTIVE: The aim of this study was to better understand the prevalence, antibiotic resistance profiles, and molecular characteristics of S. aureus and MRSA in a tertiary care hospital in the Kingdom of Bahrain. MATERIALS AND METHODS: This cross-sectional study was carried out in a tertiary hospital for a one-year period, from December 2020 to December 2021. A total of 161 consecutive S. aureus isolates were collected. Antibiotic susceptibility was tested using BD Phoenix™ automated identification and susceptibility testing system. Molecular analysis was conducted via conventional PCR and conventional multiplex PCR for SCCmec typing. RESULTS: In this study, 161 S. aureus isolates were investigated, 60% (n=97) were characterized as MRSA, of which, 12% (n=12) were healthcare-associated methicillin-resistant Staphylococcus aureus (HA-MRSA) while 88% (n=85) were community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA). No statistically significant difference (P>0.05) in antibiotic resistance trends between HA-MRSA and CA-MRSA was detected. Multidrug resistance (MDR) amounted to 19% (n=30) of all S. aureus isolates, 14% (n=9) of methicillin-susceptible Staphylococcus aureus (MSSA) isolates, and 22% (n=21) of MRSA isolates. SCCmec typing demonstrated a high prevalence of type IV (61%, n=59), followed by type V (32%, n=31), then type II (4%, n=4), and type III (3%, n=3). The PVL prevalence was 39% (n=25) in MSSA and 62% (n=60) in MRSA, 33% (n=4) in HA-MRSA, and 66% (n=56) in CA-MRSA. CONCLUSION: This study demonstrated the emergence of PVL-producing CA-MRSA in a tertiary care hospital, as well as the detection of PVL-producing MDR strains. This development prompts serious measures to be taken in order to sustain a healthy clinical environment.

Synergistic antimicrobial effect of ascorbic acid and nicotinamide with rifampicin and vancomycin against SCCmec type IV methicillin-resistant Staphylococcus aureus (MRSA).

Background. Methicillin-resistant Staphylococcus aureus (MRSA) is a pathogenic bacteria involved in a wide spectrum of human diseases. Many virulence factors promote this widespread propagation. One important factor is acquiring antibiotic resistance genes, which leads to a reduction in the availability and efficacy of therapy options. Recently, research has suggested that the remarkable antimicrobial effect of antioxidants against superbugs such as MRSA shows synergistic effects when accompanied by antimicrobial therapy. This paper aims to examine the synergistic effects of ascorbic acid and nicotinamide with a panel of antibiotics used in antimicrobial therapy against MRSA. Material and Methods. Two SCCmec type IV MRSA reference strains (EMRSA-15 and USA300) and 10 MRSA clinical isolates feature in this paper. SCCmec typing was conducted on the 10 clinical isolates via multiplex PCR after identification. Synergy experiments on antioxidants and antibiotics were evaluated via checkerboard assay. The minimum inhibitory concentration (MIC) of each agent was determined in accordance with the Clinical and Laboratory Standards Institute (CLSI) M100 guidelines through twofold microdilution assay. Results and Discussion. Synergy (FIC <0.5) was demonstrated for ascorbic acid (1/2 to 1/4 MIC) with rifampicin (1/2 to 1/8 MIC), and also ascorbic acid (1/2 to 1/16 MIC) when associated with vancomycin (1/2 MIC). Similarly, nicotinamide (1/2 to 1/16 MIC) showed a synergistic effect when paired with low concentrations of rifampicin (1/2 to 1/16 MIC), and also (at 1/4 to 1/16 MIC) with vancomycin (1/2 MIC). All reduced MICs due to synergistic combinations demonstrated statistical significance (P<0.05). Conclusion. The synergistic activity demonstrated in associating antioxidants with antibiotics shows promise in managing superbugs. However, more research is required to better understand the mechanism of the synergy and for utilization in clinical care.

The Effect of Ascorbic Acid and Nicotinamide on Panton-Valentine Leukocidin Cytotoxicity: An Ex Vivo Study.

Background: Panton−Valentine Leukocidin sustains a strong cytotoxic activity, targeting immune cells and, consequently, perforating the plasma membrane and inducing cell death. The present study is aimed to examine the individual effect of ascorbic acid and nicotinamide on PVL cytotoxicity ex vivo, as well as their effect on granulocytes viability when treated with PVL. Materials and Methods: The PVL cytotoxicity assay was performed in triplicates using the commercial Cytotoxicity Detection Kit PLUS (LDH). LDH release was measured to determine cell damage and cell viability was measured via flow cytometry. Results and discussion: A clear reduction in PVL cytotoxicity was demonstrated (p < 0.001). Treatment with ascorbic acid at 5 mg/mL has shown a 3-fold reduction in PVL cytotoxicity; likewise, nicotinamide illustrated a 4-fold reduction in PVL cytotoxicity. Moreover, granulocytes' viability after PVL treatment was maintained when incubated with 5 mg/mL of ascorbic acid and nicotinamide. Conclusions: our findings illustrated that ascorbic acid and nicotinamide exhibit an inhibitory effect on PVL cytotoxicity and promote cell viability, as the cytotoxic effect of the toxin is postulated to be neutralized by antioxidant incubation. Further investigations are needed to assess whether these antioxidants may be viable options in PVL cytotoxicity attenuation in PVL-associated diseases.

Updates on Measles Incidence and Eradication: Emphasis on the Immunological Aspects of Measles Infection.

Measles is an RNA virus infectious disease mainly seen in children. Despite the availability of an effective vaccine against measles, it remains a health issue in children. Although it is a self-limiting disease, it becomes severe in undernourished and immune-compromised individuals. Measles infection is associated with secondary infections by opportunistic bacteria due to the immunosuppressive effects of the measles virus. Recent reports highlight that measles infection erases the already existing immune memory of various pathogens. This review covers the incidence, pathogenesis, measles variants, clinical presentations, secondary infections, elimination of measles virus on a global scale, and especially the immune responses related to measles infection.