BACKGROUND AND OBJECTIVE

The human nasal passages host major human pathogens. Recent research suggests that the microbial communities inhabiting the epithelial surfaces of the nasal passages play a key factor in maintaining a healthy microenvironment by affecting both resistance to pathogens and immunological responses. Colonization of the nasal cavity by different pathogens such as Staphylococcus aureus and Klebsiella aerogenes, is associated with a higher postoperative infection morbidity. Povidone-iodine (PVP-I) as an antiseptic has been proven to display high antibacterial, antiviral, and antifungal properties even at low concentrations, and was shown to be effective in the control of infections to limit their impact and spread. It can be used as a topical antiseptic for skin decontamination and wound management, as a nasal spray, or as a gargle. There are different methods in testing the efficacy of potential antimicrobial suspensions. This study aimed to determine the concentration of PVP-I that is most effective in nasal decolonization using microsuspension test and colorimetric minimum inhibitory concentration (MIC) determination assays, resazurin microtiter assay (REMA), and Dey-Engley (D/E) neutralizer assay. The findings of this study will contribute to knowledge regarding the intended use of PVP-I in microbial control, particularly in bacterial infections.

Several dilutions (2.0%, 1.0%, 0.5%, 0.25%, 0.1% and 0.09%) of commercially bought 10% (10 mg per 100 ml) povidone-iodine were prepared and tested against a standardized inoculum (1x105) of Staphylococcus aureus and Klebsiella aerogenes at different contacttimes (5 seconds, 10 seconds, 30 seconds, 1 minute, and 5 minutes). Microdilution suspension test was performed to determine the log reduction per variable, while REMA and D/E neutralizer assay were used to determine the MIC. A value of greater than or equal to 5 log reduction was considered effective for microdilution suspension test. Estimates of agreement statistics were used to interpret the results of the assay in which the overall percent agreement (OPA), positive percent agreement (PPA), negative percent agreement (NPA), and Cohen’s kappa statistics were calculated.

Povidone-iodine concentration of 0.25% exhibited ?5 log reduction against K. aerogenes at the minimum contact time of 5 seconds. On the other hand,  a slightly higher PVP-I concentration was required to achieve ?5 log reduction for S. aureus at 0.5% concentration and a minimum contact time of 1 minute. There was an observed concordance of the results of REMA and D/E neutralizer as MIC colorimetric indicators, which yielded an overall test percent agreement of 90.30% (95% CI: 84.73–94.36), and a strong level of agreement (? = 0.8, pCONCLUSION

Low povidone-iodine concentrations (i.e., 0.5% against S. aureus and 0.25% against K. aerogenes) were observed to have bactericidal activity of at least 5 log reduction as rapid as the minimum contact time of 5 seconds. Furthermore, D/E and REMA, as colorimetric indicators, had comparable performance (OPA = 90.30%; ? = 0.8, p
Human ; Bacteria ; Povidone-iodine ; Microbial Sensitivity Tests ; Anti-infective Agents, Local ; Enterobacter Aerogenes ; Staphylococcus Aureus

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.

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

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

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 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

OBJECTIVE: To investigate the distribution and antimicrobial susceptibility of causative microorganisms recovered from patients with intra-abdominal infections (IAIs). METHODS: A total of 2,926 bacterial and fungal strains were identified in samples collected from 1,679 patients with IAIs at the Peking Union Medical College Hospital between 2011 and 2021. Pathogenic bacteria and fungi were identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Antimicrobial susceptibility testing (AST) was performed using the VITEK 2 compact system and the Kirby-Bauer method. AST results were interpreted based on the M100-Ed31 clinical breakpoints of the Clinical and Laboratory Standards Institute. RESULTS: Of the 2,926 strains identified, 49.2%, 40.8%, and 9.5% were gram-negative bacteria, gram-positive bacteria, and fungi, respectively. Escherichia coli was the most prevalent pathogen in intensive care unit (ICU) and non-ICU patients; however, a significant decrease was observed in the isolation of E. coli between 2011 and 2021. Specifically, significant decreases were observed between 2011 and 2021 in the levels of extended-spectrum β-lactamase (ESBL)-producing E. coli (from 76.9% to 14.3%) and Klebsiella pneumoniae (from 45.8% to 4.8%). Polymicrobial infections, particularly those involving co-infection with gram-positive and gram-negative bacteria, were commonly observed in IAI patients. Moreover, Candida albicans was more commonly isolated from hospital-associated IAI samples, while Staphylococcus epidermidis had a higher ratio in community-associated IAIs. Additionally, AST results revealed that most antimicrobial agents performed better in non-ESBL-producers than in ESBL-producers, while the overall resistance rates (56.9%-76.8%) of Acinetobacter baumanmii were higher against all antimicrobial agents than those of other common gram-negative bacteria. Indeed, Enterococcus faecium, Enterococcus faecalis, S. epidermidis, and S. aureus were consistently found to be susceptible to vancomycin, teicoplanin, and linezolid. Similarly, C. albicans exhibited high susceptibility to all the tested antifungal drugs. CONCLUSION The distribution and antimicrobial susceptibility of the causative microorganisms from patients with IAIs were altered between 2011 and 2021. This finding is valuable for the implementation of evidence-based antimicrobial therapy and provides guidance for the control of hospital infections.
Humans ; Anti-Bacterial Agents ; Escherichia coli ; Gram-Negative Bacteria ; Gram-Positive Bacteria ; Retrospective Studies ; Staphylococcus aureus ; Intraabdominal Infections/epidemiology* ; Candida albicans ; Coinfection

This study investigated the application of poly(N-isopropylacrylamide)-based interpenetrating network temperature-sensitive hydrogels (notation: IPNT) as the delivery vehicle for phage endolysin Lys84 and the potential of drug-loaded hydrogels as antimicrobial materials. Interpenetrating network temperature-sensitive hydrogels were prepared by free radical polymerization of sodium alginate and N-isopropylacrylamide. Drug-loaded hydrogels (IPNT-Lys84) were obtained by dry soaking method with the endolysin Lys84 of Staphylococcus aureus phage. The physical properties of the hydrogels with and without drug loading were characterized by infrared spectroscopy, scanning electron microscopy, and differential scanning calorimetry. The swelling and deswelling of the hydrogels as well as the release of endolysin Lys84 were investigated. Moreover, the antibacterial properties of IPNT-Lys84 hydrogels at different temperatures and concentrations of the drug solution were studied. The results showed that IPNT-Lys84 hydrogel had uniform pores and a low critical solubility temperature (LCST) of 32 ℃. The equilibrium swelling of the hydrogel was 30 g/g, and the water loss rate was 88% upon deswelling. The release rate of endolysin reached more than 70% within 6 h at 37 ℃. The bactericidal rate of IPNT-Lys84 hydrogel was over 99.9%. The research results showed the feasibility of using IPNT to deliver the endolysin Lys84, and IPNT-Lys84 hydrogel might be an effective antimicrobial material against multi-drug resistant Staphylococcus aureus.
Hydrogels/chemistry* ; Bacteriophages ; Methicillin-Resistant Staphylococcus aureus ; Temperature ; Anti-Infective Agents

OBJECTIVES: To explore the molecular characteristics of Staphylococcus aureus (S. aureus) in children, and to compare the molecular characteristics of different types of strains (infection and colonization strains) so as to reveal pathogenic molecular markers of S. aureus. METHODS: A cross-sectional study design was used to conduct nasopharyngeal swab sampling from healthy children in the community and clinical samples from infected children in the hospital. Whole genome sequencing was used to detect antibiotic resistance genes and virulence genes. A random forest method to used to screen pathogenic markers. RESULTS: A total of 512 S. aureus strains were detected, including 272 infection strains and 240 colonization strains. For virulence genes, the carrying rates of enterotoxin genes (seb and sep), extracellular enzyme coding genes (splA, splB, splE and edinC), leukocytotoxin genes (lukD, lukE, lukF-PV and lukS-PV) and epidermal exfoliating genes (eta and etb) in infection strains were higher than those in colonization strains. But the carrying rates of enterotoxin genes (sec, sec3, seg, seh, sei, sel, sem, sen, seo and seu) were lower in infection strains than in colonization strains (P<0.05). For antibiotic resistance genes, the carrying rates of lnuA, lnuG, aadD, tetK and dfrG were significantly higher in infection strains than in colonization strains (P<0.05). The accuracy of cross-validation of the random forest model for screening pathogenic markers of S. aureus before and after screening was 69% and 68%, respectively, and the area under the curve was 0.75 and 0.70, respectively. The random forest model finally screened out 16 pathogenic markers (sem, etb, splE, sep, ser, mecA, lnuA, sea, blaZ, cat(pC233), blaTEm-1A, aph(3')-III, ermB, ermA, ant(9)-Ia and ant(6)-Ia). The top five variables in the variable importance ranking were sem (OR=0.40), etb (OR=3.95), splE (OR=1.68), sep (OR=3.97), and ser (OR=1.68). CONCLUSIONS The random forest model can screen out pathogenic markers of S. aureus and exhibits a superior predictive performance, providing genetic evidence for tracing highly pathogenic S. aureus and conducting precise targeted interventions.
Child ; Humans ; Staphylococcus aureus/genetics* ; Cross-Sectional Studies ; Enterotoxins/genetics* ; Staphylococcal Infections ; Whole Genome Sequencing

OBJECTIVE: To analyze the pathogenic bacterial spectrum, drug resistance, and risk factors associated with multidrug-resistant bacterial infection and mortality in patients with hematologic diseases complicated by bloodstream infections, so as to provide reference for rational drug use and improving prognosis. METHODS: Positive blood culture specimens of patients with hematologic diseases in two Class A tertiary hospitals of Shanxi province from January 2019 to December 2021 were retrospectively analyzed. Pathogen distribution, drug resistance and outcomes of patients with bloodstream infection were investigated, then the multivariate logistic analysis was performed to analyze the risk factors of multidrug-resistant bacterial infection and factors affecting prognosis. RESULTS: 203 strains of pathogens were identified, mainly Gram-negative bacteria (GNB) (69.46%, 141/203), of which Escherichia coli (E.coli) had the highest incidence (41.13%, 58/141), followed by Klebsiella pneumoniae (20.57%, 29/141) and Pseudomonas aeruginosa (12.77%, 18/141). Extended-spectrum beta-lactamase (ESBL)-producing E.coli and Klebsiella pneumoniae were 46.55% (27/58) and 37.93% (11/29), respectively. Carbapenem-resistant Gram-negative bacteria accounted for 10.64% (15/141). And Gram-positive bacteria accounted for 27.59% (56/203), Staphylococcus epidermidis, Streptococcus pneumoniae, and Staphylococcus aureus were the most frequently isolated pathogen among Gram-positive bacteria (14.29%, 12.50% and 10.71%, respectively), of which methicillin-resistant Staphylococcus aureus accounted for 33.33% (2/6), coagulase-negative staphylococci accounted for 87.50% (7/8), without vancomycin- or linezolid-resistant strain. Additionally, fungi accounted for 2.95% (6/203), all of which were Candida. Multidrug-resistant Gram-negative bacteria (MDR-GNB) accounted for 53.90% (76/141). Duration of neutropenia >14 days was a risk factor for developing MDR-GNB infection. The 30-day all-cause mortality was 10.84%. Multivariate logistic regression analysis showed that the significant independent risk factors for mortality were age≥60 years (P <0.01, OR =5.85, 95% CI: 1.80-19.07) and use of vasopressor drugs (P <0.01, OR =5.89, 95% CI: 1.83-18.94). CONCLUSION The pathogenic bacteria of bloodstream infection in patients with hematological diseases are widely distributed, and the detection rate of multidrug-resistant bacteria is high. The clinicians should choose suitable antibiotics according to the results of bacterial culture and antibiotic susceptibility test.
Humans ; Middle Aged ; Bacteremia/mortality* ; Bacteria/isolation & purification* ; Drug Resistance ; Drug Resistance, Bacterial ; Gram-Negative Bacteria ; Hematologic Diseases/complications* ; Methicillin-Resistant Staphylococcus aureus ; Retrospective Studies ; Risk Factors ; Sepsis/mortality*