BACKGROUND AND OBJECTIVE

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the leading causes of hospital and community-acquired infections, showing antimicrobial resistance (AMR), which is an increasing public health concern. One of the commonly-used methods to evaluate resistance include the Kirby-Bauer disk diffusion method. However, this test is found to be time-consuming, lacking in terms of mechanization and automation, alongside its non-applicability to certain antibiotics such as vancomycin. Thus, the Clinical Laboratory Standards Institute (CLSI) recommends using the broth microdilution method in the evaluation of antibacterial activities against S. aureus. A rapid laboratory identification of MRSA is important in the treatment of patients. Therefore, this study aims to optimize and evaluate the effectiveness of a rapid microplate assay using resazurin dye as a colorimetric indicator in determining antibacterial activity against clinical isolates of MRSA and methicillin-susceptible S. aureus (MSSA).

Clinical isolates of MRSA and MSSA were obtained from the Philippine General Hospital (PGH) Microbiology Section, and American Type Culture Collection (ATCC) controls of both strains (ATCC 25923 and ATCC 43300) were acquired. These were then subjected to identification and confirmation procedures. A standardization of bacterial inoculum was performed by comparing its 24-hr growth in Mueller Hinton Broth to 0.5 McFarland Standard. The resazurin microplate assay (REMA) was set-up using two-fold serial dilution of control antibiotics such as oxacillin, vancomycin, and cefoxitin. Each plate was inoculated with standardized bacterial growth of controls and clinical isolates. To determine the time needed for the reduction of the resazurin dye, a qualitative assessment was conducted by comparing the reaction time between a 6.75 mg/mL dye with a 0.01 mg/mL dye. The plates were also subjected to different incubation times and dye concentrations, and the optical densities of the plates were compared using a microplate reader.

Results showed that there were no significant differences between the optical densities of the wells of those incubated for 5 hours and for 24 hours (p >0.05). Furthermore, there was a significant reduction in the reaction time of the dye (from 18 hours to 1 hour) when the dye concentration was reduced from 6.75 mg/mL to 0.01 mg/mL. The optimized REMA showed a significant difference between the minimum inhibitory concentrations (MICs) of the different antibiotics against the control and isolate strains of MRSA and MSSA, showing a W of -2.98 (pCONCLUSION

Based on the results presented, the researchers determined the optimal condition for the resazurin microtiter assay, which was 0.01 g/mL concentration of resazurin dye, at a 5-hour incubation period. This study has shown that an optimized REMA is an efficient and fast method to determine the antimicrobial activities of oxacillin, cefoxitin, and vancomycin against MRSA and MSSA.

Objective:Multi-drug resistant bacterial infection（MRSA） complications occurring in cochlear implant recipients is rare and of serious consequence. This paper aimed to summarize the treatment experience of a patient with MRSA infection after cochlear implantation. A patient with nasopharyngeal malignant tumor after radiotherapy developed to severe sensorineural deafness. She suffered MRSA infection nine days after cochlear implantation. Since the wound failed to heal after weeks of topical and systemic sensitive antibiotic therapy, the patient underwent surgery for wound debridement. The stimulator-receiver and the electrode of the implant was removed, negative pressure wound therapy was applied, and systemic anti-infection treatment with sensitive antibiotics for weeks, the patients recovered and was discharged from hospital 69 days after infection.
Humans ; Cochlear Implantation/adverse effects* ; Female ; Drug Resistance, Multiple, Bacterial ; Staphylococcal Infections/therapy* ; Methicillin-Resistant Staphylococcus aureus ; Cochlear Implants ; Anti-Bacterial Agents/therapeutic use* ; Postoperative Complications ; Middle Aged

Atopic dermatitis (AD) is a prevalent inflammatory skin disorder in which patients experience recurrent eczematous lesions and intense itching. The colonization of Staphylococcus aureus (S. aureus) is correlated with the severity of the disease, but its role in AD development remains elusive. Using single-cell RNA sequencing, we uncovered that keratinocytes activate a distinct immune response characterized by induction of Il24 when exposed to methicillin-resistant S. aureus (MRSA). Further experiments using animal models showed that the administration of recombinant IL-24 protein worsened AD-like pathology. Genetic ablation of Il24 or the receptor Il20rb in keratinocytes alleviated allergic inflammation and atopic march. Mechanistically, IL-24 acted through its heterodimeric receptors on keratinocytes and augmented the production of IL-33, which in turn aggravated type 2 immunity and AD-like skin conditions. Overall, these findings establish IL-24 as a critical factor for onset and progression of AD and a compelling therapeutic target.
Dermatitis, Atopic/genetics* ; Interleukins/metabolism* ; Animals ; Methicillin-Resistant Staphylococcus aureus/immunology* ; Mice ; Keratinocytes/microbiology* ; Humans ; Interleukin-33/immunology* ; Inflammation/microbiology* ; Staphylococcal Infections/microbiology* ; Disease Models, Animal ; Hypersensitivity/microbiology* ; Mice, Inbred C57BL

Given the increasing concern regarding antibacterial resistance, the antimicrobial properties of naphthoquinones have recently attracted significant attention. While 1,4-naphthoquinone and its derivatives have been extensively studied, the antibacterial properties of 5,8-dihydroxy-1,4-naphthoquinone derivatives remain relatively unexplored. This study presents a comprehensive in vitro and in vivo analysis of the antibacterial activity of 35 naturally sourced and chemically synthesized derivatives of 5,8-dihydroxy-1,4-naphthoquinone. Kirby-Bauer antibiotic testing identified three compounds with activity against methicillin-resistant Staphylococcus aureus (MRSA), with one compound (PNP-02) demonstrating activity comparable to vancomycin in minimum inhibitory concentration, minimum bactericidal concentration (MBC), and time-kill assays. Microscopic and biochemical analyses revealed that PNP-02 adversely affects the cell wall and cell membrane of MRSA. Mechanistic investigations, including proteomic sequencing analyses, Western blotting, and RT-qPCR assays, indicated that PNP-02 compromises cell membrane integrity by inhibiting arginine biosynthesis and pyrimidine metabolism pathways, thereby increasing membrane permeability and inducing bacterial death. In an in vivo mouse model of skin wound healing, PNP-02 exhibited antibacterial efficacy similar to vancomycin. The compound demonstrated low toxicity to cultured human cells and in hemolysis assays and remained stable during serum incubation. These findings suggest that PNP-02 possesses promising bioactivity against MRSA and represents a potential novel antibacterial agent.
Methicillin-Resistant Staphylococcus aureus/genetics* ; Anti-Bacterial Agents/chemistry* ; Naphthoquinones/administration & dosage* ; Animals ; Microbial Sensitivity Tests ; Mice ; Humans ; Staphylococcal Infections/microbiology* ; Molecular Structure

Background and Objective: Methicillin-resistant Staphylococcus aureus (MRSA) is one of the leading causes of hospital and community-acquired infections, showing antimicrobial resistance (AMR), which is an increasing public health concern. One of the commonly-used methods to evaluate resistance include the Kirby-Bauer disk diffusion method. However, this test is found to be time-consuming, lacking in terms of mechanization and automation, alongside its non-applicability to certain antibiotics such as vancomycin. Thus, the Clinical Laboratory Standards Institute (CLSI) recommends using the broth microdilution method in the evaluation of antibacterial activities against S. aureus. A rapid laboratory identification of MRSA is important in the treatment of patients. Therefore, this study aims to optimize and evaluate the effectiveness of a rapid microplate assay using resazurin dye as a colorimetric indicator in determining antibacterial activity against clinical isolates of MRSA and methicillin-susceptible S. aureus (MSSA). Methods: Clinical isolates of MRSA and MSSA were obtained from the Philippine General Hospital (PGH) Microbiology Section, and American Type Culture Collection (ATCC) controls of both strains (ATCC 25923 and ATCC 43300) were acquired. These were then subjected to identification and confirmation procedures. A standardization of bacterial inoculum was performed by comparing its 24-hr growth in Mueller Hinton Broth to 0.5 McFarland Standard. The resazurin microplate assay (REMA) was set-up using two-fold serial dilution of control antibiotics such as oxacillin, vancomycin, and cefoxitin. Each plate was inoculated with standardized bacterial growth of controls and clinical isolates. To determine the time needed for the reduction of the resazurin dye, a qualitative assessment was conducted by comparing the reaction time between a 6.75 mg/mL dye with a 0.01 mg/mL dye. The plates were also subjected to different incubation times and dye concentrations, and the optical densities of the plates were compared using a microplate reader. Results: Results showed that there were no significant differences between the optical densities of the wells of those incubated for 5 hours and for 24 hours (p >0.05). Furthermore, there was a significant reduction in the reaction time of the dye (from 18 hours to 1 hour) when the dye concentration was reduced from 6.75 mg/mL to 0.01 mg/mL. The optimized REMA showed a significant difference between the minimum inhibitory concentrations (MICs) of the different antibiotics against the control and isolate strains of MRSA and MSSA, showing a W of -2.98 (p <0.05) using the Wilcoxon Rank-Sum non-parametric test. Furthermore, the REMA has shown better illustration of anti-MRSA and anti-MSSA activities as compared to the Kirby Bauer disk diffusion method. Conclusion Based on the results presented, the researchers determined the optimal condition for the resazurin microtiter assay, which was 0.01 g/mL concentration of resazurin dye, at a 5-hour incubation period. This study has shown that an optimized REMA is an efficient and fast method to determine the antimicrobial activities of oxacillin, cefoxitin, and vancomycin against MRSA and MSSA.
Methicillin Resistant Staphylococcus aureus

Background: Ardisia serrata (Aunasin) is an endemic Philippine plant of the family Primulaceae, with several studiesshowing the genus Ardisia as having potential antibacterial, antiangiogenic, cytotoxic, and antipyretic properties. Objective: This study aims to determine the antibacterial and antibiofilm-forming activity of Ardisia serrata ethanolic and aqueous extracts on Escherichia coli, Methicillin-Sensitive Staphylococcus aureus (MSSA), and Methicillin-Resistant Staphylococcus aureus (MRSA). Methods: This is an experimental study testing the activity against bacterial strains of E. coli, MSSA, and MRSA using ethanolic and aqueous extracts of A. serrata leaves. Microtiter susceptibility and biofilm inhibition assays were done with two-fold dilutions of the extract against the selected strains using spectrophotometry with optical density (OD) at 600 nm and 595 nm, respectively, to quantify bacterial growth and biofilm inhibition. The bacterial susceptibility and biofilm inhibition activity was reported as percent inhibition (PI). Minimum inhibitory concentration (MIC), and minimum biofilm inhibition concentration (MBIC) values were obtained using logarithmic regression of the PI values. Results: A. serrata ethanolic extracts showed weak growth inhibitory activity against MSSA and MRSA with minimum inhibitory concentration (MIC) values of 2.6192 and 3.2988 mg/mL, respectively, but no biofilm inhibition activity was noted, while the aqueous extracts exhibited negligible biofilm inhibition activity against MSSA and MRSA with minimum biofilm inhibition concentration (MBIC) values of 13.5972 and 8964.82 mg/mL, respectively, and with no growth inhibition activity. Both ethanolic and aqueous extracts showed no growth inhibition and biofilm inhibition activities against E. coli. Conclusion Staphylococcus aureus is susceptible to the bioactivity of the leaf extracts of A. serrata and has potential to be used as an antibacterial in the treatment of infectious diseases.
Methicillin-resistant Staphylococcus aureus ; Escherichia coli ; natural product ; biological products

Objective: To determine the point prevalence of, and risk factors associated with MRSA carriage among resident physicians of surgical departments at the Ospital ng Maynila Medical Center. Methods: Design: Cross-sectional Study. Setting: Tertiary Government Training Hospital. Participants:51 resident physicians from different surgical departments (general surgery, obstetrics and gynecology, ophthalmology, otorhinolaryngology – head and neck surgery and dermatology) underwent nasal and pharyngeal swabs with microbial culture and sensitivity testing to identify MRSA carriers. Fisher Exact Test and logistic regression were utilized to determine associations between MRSA carriage and various risk factors including frequency of hand washing and departmental affiliation. Results: Overall prevalence rate of MRSA carriage was 9.8%. Otorhinolaryngology residents had the highest combined prevalence of MRSA of 42.9%, significantly higher compared to other departments and were used as a reference in logistic regression analyses. Notably, handwashing only once daily was associated with a 20-fold increase in the risk of MRSA carriage (OR 20.5, 95% CI: 1.82 to 230, p = .014). Other departments did not demonstrate statistically significant differences in MRSA carriage rates. Conclusions Otorhinolaryngology resident physicians had the highest combined prevalence of MRSA and nasal MRSA was found only in otorhinolaryngology residents. The surgical subspecialty and frequency of handwashing of the healthcare worker were identified as important risk factors to develop MRSA carriage. Targeted interventions (including enhanced infection control protocols and regular screening) are needed especially in high-risk departments.
Methicillin-Resistant Staphylococcus aureus ; Surgical Wound Infection

To understand the clinical characteristics of Staphylococcus aureus bloodstream infection and the main risk factors affecting clinical prognosis, providing a reference for clinical prevention and control of Staphylococcus aureus bloodstream infection. In this study, the clinical data of 152 patients with Staphylococcus aureus bloodstream infection admitted to Guangdong Provincial People's Hospital from January 2019 to December 2021 were retrospectively analyzed by reviewing the electronic medical record system, including underlying diseases, clinical characteristics, risk factors, and bacterial resistance. Statistical methods such as Chi-Squared Test and t Test were used to analyze the related risk factors that may affect the clinical characteristics and prognosis of patients with Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infection, then the variables with P<0.05 in univariate analysis were included in the multivariate logistic regression model to analyze the independent risk factors of poor prognosis. The results showed among 152 patients with Staphylococcus aureus bloodstream infection, 50 patients (32.89%) were infected with MRSA. In comparison, 102 patients (67.11%) were infected with methicillin-sensitive Staphylococcus aureus (MSSA). Except for rifampicin, the resistance rate of MRSA to commonly used antibiotics was all higher than that of MSSA, and the difference was statistically significant (Chi-square values were 8.272, 11.972, 4.998, 4.776, respectively;all P-values are less than 0.05). Strains resistant to vancomycin, linezolid, and quinupristin/dalfopristin were not found. In the MRSA group, indwelling catheter and drainage tube, carbapenems, and β-lactamase inhibitor treatment were significantly higher than the MSSA group. The difference was statistically significant (P<0.05). The incidence of poor prognosis of bloodstream infection in the MRSA group was higher than that in the MSSA group (34.00% vs 13.73%), and the difference was statistically significant (χ²=8.495, P<0.05). No independent risk factors associated with poor prognosis were found in the included patients with MRSA bloodstream infection.Multivariate Logistic regression model analysis showed that solid malignant tumors (OR=13.576, 95%CI: 3.352-54.977, P<0.05), mechanical ventilation (OR=7.468, 95%CI: 1.398-39.884, P<0.05) were the most important independent risk factors for poor prognosis in patients with Staphylococcus aureus bloodstream infection. In summary, the poor prognosis rate of MRSA bloodstream infection is higher than that of MSSA. The clinical evaluation of related risk factors should be strengthened, targeted prevention and control interventions should be taken to improve the prognosis of patients with Staphylococcus aureus bloodstream infection, and the use of antibiotics should be rational and standardized, to control bacterial infection and drug resistance effectively .
Humans ; Methicillin-Resistant Staphylococcus aureus ; Staphylococcus aureus ; Retrospective Studies ; Prognosis ; Staphylococcal Infections/microbiology* ; Anti-Bacterial Agents/pharmacology* ; Methicillin/therapeutic use* ; Sepsis

Humans ; Bacteremia ; Cross Infection ; Methicillin-Resistant Staphylococcus aureus ; Retrospective Studies ; Sepsis ; Staphylococcal Infections/epidemiology* ; Staphylococcus aureus ; Tertiary Care Centers ; China

Objective: To understand the distribution and antimicrobial resistance of common bacteria from children aged 0-14 years from China Antimicrobial Resistance Surveillance System. Methods: Bacterial resistance data of 2 575 040 strains from children aged 0-14 years were extracted from the national bacterial resistance surveillance reports from October 2018 to September 2022 and resistance changes were further analyzed by comparing with all data in each year. Results: The total number of bacteria isolated from children in 2018-2022 ranged from 415 306-588 016 strains, accounted for 15.9% (514 193/3 234 372), 16.2% (572 107/3 528 471), 12.8% (415 306/3 249 123), 13.0% (485 418/3 743 027), and 12.2% (588 016/4 828 509), respectively. The proportions of gram-positive bacteria among children were 45.4% (233 456/514 193), 44.5% (254 869/572 107), 44.7% (185 756/415 306), 42.6% (206 903/485 418), and 41.7% (245 044/588 016), respectively. The top five isolates of gram-positive bacteria were Staphylococcus aureus (36.0%-38.8%), Streptococcus pneumoniae (27.1%-31.7%), Staphylococcus epidermidis (7.3%-9.3%), Enterococcus faecium (4.0%-4.8%), and Enterococcus faecium (2.5%-3.6%), and the top five isolates of gram-negative bacteria were Escherichia coli (21.8%-26.2%), Haemophilus influenzae (14.4%-26.4%), Klebsiella pneumoniae (10.1%-14.7%), Moraxella catarrhalis (7.3%-11.9%), and Pseudomonas aeruginosa (5.5%-6.8%). The bacteria from children aged 0-14 years commonly isolated from sputum samples (48.8%-57.0%). The prevalence of methicillin-resistant S. aureus was 28.7%-30.1%. The detection rates of vancomycin-resistant E. faecalis or E. faecium were 0.1%-0.3%. The proportions of non-cerebrospinal fluid-derived penicillin-resistant S. pneumoniae were 0.7%-1.6%. The prevalence of cefotaxime and (or) ceftriaxone-resistant E. coli and K. pneumoniae decreased were 43.7%-50.0% and 31.8%-42.7%, respectively. The resistant rates of E. coli to imipenem and meropenem were 1.2%-1.9% and 1.2%-2.0%, respectively, and the resistant rates of K. pneumoniae to imipenem and meropenem were 7.3%-10.1% and 8.2%-12.2%, respectively. About 6.6%-10.2% and 5.3%-9.6% of the P. aeruginosa isolates showed resistant to imipenem and meropenem, respectively, while 17.2%-24.0% and 19.0%-29.4% of the Acinetobacter baumannii isolates were resistant to imipenem and meropenem, respectively. Conclusions: There is no significant change in the composition of common clinical pathogens in children aged 0-14 years from 2018 to 2022. The prevalence of some resistant bacteria such as methicillin-resistant S. aureus and carbapenem-resistant Enterobacterales is decreasing. However, it is necessary to pay attention to antimicrobial resistance of bacteria from children and long-term monitoring of the prevalence of resistant bacteria should be conducted.
Child ; Humans ; Anti-Bacterial Agents/therapeutic use* ; Meropenem ; Methicillin-Resistant Staphylococcus aureus ; Escherichia coli ; Microbial Sensitivity Tests ; Bacteria ; Gram-Positive Bacteria ; Staphylococcal Infections/drug therapy* ; Klebsiella pneumoniae ; Imipenem ; Drug Resistance, Bacterial