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

OBJECTIVE

To determine the prevalence of rectal colonization with carbapenem-resistant organisms (CRO) among PGH neonatal intensive care unit (NICU) patients.

A prospective single-center observational study conducted over a 1-month period included all NICU 3 and cohort area patients admitted on April 24, 2024. Rectal swabs were collected for multidrug-resistant organism (MDRO) screening and repeated weekly for 1 month while admitted. Swabs were inoculated on chromogenic media, and isolates were identified and tested for antimicrobial sensitivity by disk diffusion. Clinical characteristics and outcomes were collected for 30 days from initial MDRO screening. Descriptive statistics were used to summarize the data.

The point prevalence of CRO colonization was 37% (14 of 38) at initial screening. There were 14 incident colonizations, hence the 4-week period prevalence of CRO colonization was 72.5% (29 of 40). The patients were mostly very preterm, very low birth weight neonates, majority were tested within the first 2 weeks of life, and half were exposed to meropenem at initial screening. Nosocomial infection developed in 29% and 64%, and 30-day mortality rate was 8% and 21% among initially non-CRO-colonized and CRO-colonized patients respectively. Despite high CRO colonization, no culture-proven CRO infection was observed. Surveillance screening documented persistent CRO colonization in 37%, but no decolonization. Escherichia coli, Klebsiella spp. and Serratia spp. were the most common colonizers.

The high prevalence of rectal CRO colonization in the NICU emphasizes the burden of antimicrobial resistance, but despite the high CRO colonization, no CRO infection was documented from the limited sample and study period.

BACKGROUND AND OBJECTIVE

Antimicrobial resistance (AMR) is a leading global public health concern as it resulted in more difficult-to-treat infections and fatalities. In the Philippines, drug-resistant E. coli, including multidrug-resistant (MDR), extended-spectrum beta-lactamase (ESBL)-producing, carbapenemase-producing carbapenem-resistant (CP-CR) E. coli, have been isolated from common food animals, increasing the risk of cross-contamination between humans, animals, and the environment. However, there is a lack of data on the distribution of E. coli in chicken meat in public wet markets. This study aims to describe the AMR profile of E. coli in raw chicken meat from retail stalls in a selected wet market in Manila City.

This quantitative descriptive study characterized the AMR profile of E. coli isolated from 25 raw chicken meat samples from a wet market in Manila City. Antimicrobial susceptibility was determined through disk diffusion method against 23 antimicrobial agents in 16 antimicrobial classes. MDR E. coli were identified based on the resistance patterns. ESBL- and carbapenemase-producing capacities of the bacteria were tested through double disk synergy test and modified carbapenem inactivation method, respectively.

Twenty-four out of 25 (96%) chicken samples contained E. coli isolates. Of these, 23 (96%) were classified as MDR. High resistance rates were observed against ampicillin (92%), tetracycline (88%), trimethoprim-sulfamethoxazole (83%), chloramphenicol (79%), ampicillin-sulbactam (75%), amoxicillin-clavulanic acid (67%), fosfomycin (67%), and streptomycin (54%). The majority of the E. coli isolates were still susceptible to a wide range of selected antimicrobial agents, including carbapenems (100%), ceftriaxone (100%), cefepime (100%), cefuroxime (96%), cefotaxime (96%), ceftazidime (96%), piperacillin-tazobactam (96%), aztreonam (96%), cefoxitin (92%), and nitrofurantoin (83%), among others. Meanwhile, none of the 24 isolated E. coli samples were classified as ESBL- and CP-CR E. coli.

Among the 25 chicken samples, 24 E. coli colonies were isolated that exhibited 0% to 92% resistance rates against selected antimicrobial agents. Most isolates were classified as MDR, but none were considered ESBLand CP-CR E. coli. This study suggests that chickens in wet markets can potentially serve as reservoir hosts for drugresistance genes, which could transfer to other bacteria and contaminate humans, animals, and the environment within the food production and supply chain. These findings emphasize the need for AMR surveillance and strategies to combat AMR in the Philippines through the One Health approach.

INTRODUCTION

Burn wound infection is a significant risk factor in the morbidity and mortality of burn wound patients. Previous studies in our institution showed bacterial colonization in burn patients seen beyond 24 hours post-injury. The microbiological profile of burn wounds seen within 24 hours, including the presence and risk factors for wound colonization, has not been determined in our Burn Center.

To identify the presence and risk factors for burn wound colonization in burn patients seen less than 24 hours after injury and determine the microbiological profile and antibiotic susceptibility patterns in colonized burn wounds.

One hundred eighty-nine burn patients who were seen at and admitted to the UP Philippine General Hospital ATR Burn Center within 24 hours of the burn injury from June 2021 until July 2023 were included in the study. Demographic and clinical data were collected upon admission. A total of 635 swab samples were collected from 189 patients and were sent for identification of aerobic organisms by standard culture methods and antibiotic sensitivity tests using the Kirby-Bauer disc diffusion method. Association of patient characteristics (area of injury, time received post-injury, previous hospital care, place of injury, percent burn injury, etiology, mode of transport, and type of dressing prior to admission) were determined using Chi square test of independence.

Out of 189 burn patients seen within 24 hours after injury included in the study, 58.73% (n = 111) of patients, and 49.29% (n = 313) of swabs showed bacterial colonization. Burn wound colonization was associated with area of injury/body region (χ2 5 = 16.29, p = .0061), time received post-injury (χ2 3 = 24.62, p < 0.0001, post hoc Fisher’s test for 6-12 hours vs. within the first 6 hours: p < 0.0001), place of burn injury (χ2 2 = 18.17, p = 0.0001, post hoc Fisher’s test work vs. home: p = 0.0006, work vs. outdoors: p = 0.0015), percent burn injury (χ2 4 = 21.40, p = 0.0003, post hoc Fisher’s test 25-49% vs. 0-9%: p = 0.004, 50-75% vs. 0-9%: p = 0.002), and etiology of burn injury (χ2 2 = 37.05, p < 0.0001, post hoc Fisher’s test scald vs. flame: p = 0.0012, electrical vs. flame: p < .0001). From 313 positive samples, 357 isolates were identified. Staphylococcus (58.8%) was the most common organism isolated. It was noted that out of the total isolates, 15 (4.2%) were identified to be methicillin-resistant S. aureus (MRSA) while 5 isolates (1.4%) were methicillin-resistant S. epidermidis (MRSE). Streptococcus (10.4%) and Acinetobacter (6.2%) were the second and third most common organisms, respectively. Other groups identified were Aeromonas, Bacillus, Enterobacter, Pseudomonas, Klebsiella, and diphtheroids. Frequency of bacterial isolates differed across body regions, time received post-injury, percent burn injury, and etiology of burn injury. Resistance to one antibiotic was observed in 36.84%, 6.25%, and 63.64% of Staphylococcus, Streptococcus, and Acinetobacter isolates tested, respectively. Resistance to more than 1 antibiotic was observed in 48.68% of Staphylococcus isolates and 50.0% of Streptococcus isolates tested. Among the 51 S. aureus isolates, 29.1% were methicillin-resistant S. aureus (MRSA).

In burn patients seen within 24 hours after injury, about half of burn wounds and more than half of patients showed the presence of microbial growth. Potential risk factors for positive microbial growth in a burn wound during this timeframe were area of injury/ body region, place of injury, time received post-injury, percent TBSA burn, and etiology of burn injury. The most common isolate was Staphylococcus spp. More than half of Staphylococcus isolates showed antibiotic resistance, with a significant number showing multidrug resistance. More than a quarter of S. aureus isolates were methicillin-resistant S. aureus (MRSA). These results suggest that bacterial isolates can colonize burn wounds even within 24 hours post-injury and may exhibit antibiotic resistance.

OBJECTIVE: To investigate the mechanism of autophagy in regulating bacterial translocation in intestinal infection caused by hypervirulent Klebsiella pneumonia (hvKp) and explore the method of reducing translocation infection of intestinal bacteria. METHODS: Fifty C57BL/6J mice were divided into gavage group (n = 40) and control group (CO group, n = 10). The gavage group was orally administered with 200 μL/d of hvKp (colony count of 10⁹ CFU/mL) continuously for 5 days to establish a hvKp intestinal infection model. CO group was given an equal amount of normal saline. After the experiment, the mice were anesthetized with lsofluraneand euthanized with cervical dislocation under anesthesia. Peripheral venous blood of mice was collected to detect bacterial translocation by 16S rDNA sequencing, then divided into translocation group (BT+ group) and non-translocation group (BT- group). Hematoxylin-eosin (HE) staining was used to evaluate intestinal morphology. The ultrastructural changes of intestinal tissues were observed by electron microscope. The levels of intestinal oxidative stress indicators such as superoxide dismutase (SOD), malondialdehyde (MDA) and glutathione peroxidase (GPx) were measured. Translocation was detected by in situ hybridization. The expression of tight junction protein microtubule-associated protein 1 light chain 3-II (LC3-II) and autophagy protein Beclin-1 were measured by Western blotting. The mRNA expression of tight junction proteins ZO-1 and Claudin-2 were detected by reverse transcription-polymerase chain reaction (RT-PCR). The expression of autophagy protein and tight junction protein were observed by immunofluorescence. RESULTS: Two out of 40 mice in the gavage group died after developing aspiration pneumonia. All mice in the CO group survived. The 16S rDNA sequencing results showed that no bacteria were detected in the peripheral blood of the CO group, but bacteria were detected in the peripheral blood of 18 mice in the gavage group, with a bacterial translocation rate of 47.4%. The BT- and BT+ groups showed intestinal mucosal tissue damage, with severe damage in the BT+ group. Compared with the CO group, the level of MDA in the BT- and BT+ groups were significantly increased, while the activities of SOD and GPx were significantly decreased. Compared with the BT- group, the MDA level in the BT+ group further increased, while the SOD and GPx activities further decreased [MDA (mmol/mg): 2.98±0.11 vs. 2.48±0.11, SOD (U/mg): 62.40±5.45 vs. 73.40±4.08, GPx (U/mg): 254.72±10.80 vs. 303.55±8.57, all P < 0.01]. The results of in situ hybridization detection showed that after continuous gastric lavage for 5 days, displaced hvKp was detected in the intestinal mucosal lamina propria and liver tissue of the BT+ group. Compared with the CO group, the protein expressions of LC3-II and Beclin-1 in the BT- and BT+ groups were significantly increased. The protein expressions of LC3-II and Beclin-1 in the BT+ group were obviously lower than those in the BT- group (LC3-II/β-actin: 0.38±0.04 vs. 0.70±0.09, Beclin-1/β-actin: 0.62±0.05 vs. 0.86±0.05, both P < 0.01), and there were autophagosomes in the intestinal mucosa. These results indicated that intestinal mucosal autophagy was activated after hvKp continuous gavage. Compared with CO group, the mRNA expressions of ZO-1 and Claudin-2 in the BT- and BT+ groups were significantly decreased. Compared with the BT- group, the mRNA expressions of ZO-1 and Claudin-2 in the BT+ group was further reduced [ZO-1 mRNA (2^-ΔΔCT): 0.78±0.06 vs. 0.88±0.06, Claudin-2 mRNA (2^-ΔΔCT): 0.40±0.04 vs. 0.70±0.06, both P < 0.01]. The immunofluorescence results showed that the fluorescence intensity of LC3-II, Beclin-1, ZO-1, and Claudin-2 in the BT+ group was significantly lower than that in the BT- group. CONCLUSION HvKp can activate intestinal mucosal autophagy and reduce the damage to intestinal mucosal barrier function by down-regulating oxidative stress level, reduce the occurrence of bacterial translocation.
Animals ; Oxidative Stress ; Mice, Inbred C57BL ; Autophagy ; Intestinal Mucosa/microbiology* ; Bacterial Translocation ; Mice ; Klebsiella Infections/microbiology* ; Superoxide Dismutase/metabolism* ; Beclin-1

OBJECTIVE: To develop and validate a predictive model for the risk of bloodstream infection (BSI) caused by carbapenem-resistant Klebsiella pneumoniae (CRKP). METHODS: A literature search was conducted in PubMed, Cochrane Library, and Embase databases from inception to July 2022 to identify studies reporting statistically significant risk factors for CRKP-BSI. Relative risks (RR) were extracted and pooled. Based on factor weights, a risk-scoring model was established. For external validation, hospitalized CRKP-infected patients from January 2016 to January 2022 at Shanghai First People's Hospital were included. Clinical data were used to calculate individual risk scores. The predictive accuracy was assessed using receiver operator characteristic curve (ROC curve). Patients were stratified into low-to-intermediate-risk and high-risk groups based on the optimal cut-off, and CRKP BSI incidence was compared between groups. RESULTS: The literatures related to the risk factors of CRKP-BSI published from database inception to July 2022 was retrieved and screened from PubMed, Cochrane Library, and Embase. Fourteen risk factors were included in the scoring model: cardiovascular disease, severe neutropenia or immunosuppression, intensive care unit (ICU) stay history, prior hospitalization, carbapenem exposure, aminoglycoside exposure, antifungal exposure, endotracheal intubation or tracheostomy, mechanical ventilation, hemodialysis, central venous catheter, indwelling urinary catheter, CRKP colonization, and Klebsiella pneumoniae positivity at non infection sites. The total score ranged from 0 to 173.5 points. In the validation cohort of 230 CRKP-infected patients, 41 developed CRKP BSI. The model yielded an area under the curve (AUC) of 0.783 (95%CI was 0.689-0.876). The optimal cut off was 81.25 points, with sensitivity of 75.6% and specificity of 81.0%. Based on this cut off, 163 patients were categorized as low-to-intermediate risk and 67 patients as high risk. The incidence of CRKP BSI in the high-risk group was significantly higher than in the low-to-intermediate-risk group [64.2% (43/67) vs. 4.9% (8/163); RR = 13.175 (95%CI was 5.920-29.319), P < 0.001]. CONCLUSIONS The model, based on 14 routinely available clinical parameters, demonstrated good performance in predicting CRKP BSI risk and may assist clinicians in early identification of high risk patients.
Humans ; Klebsiella pneumoniae/drug effects* ; Klebsiella Infections/microbiology* ; Carbapenems/pharmacology* ; Risk Factors ; Bacteremia/microbiology* ; ROC Curve ; Carbapenem-Resistant Enterobacteriaceae

Salmonellosis represents a global epidemic, and the emergence of extensively drug-resistant (XDR) Salmonella and its sustained transmission worldwide constitutes a significant public health concern. Flagellum-mediated motility serves as a crucial virulence trait of Salmonella that guides the pathogen toward the epithelial surface, enhancing gut colonization. Artemisia argyit essential oil, a traditional herb extract, demonstrates efficacy in treating inflammation-related symptoms and diseases; however, its effects on flagellum assembly and expression mechanisms in anti-Salmonella activity remain inadequately explored. This study aimed to elucidate the mechanism by which Artemisia argyit essential oil addresses Salmonella infections. Network pharmacological analysis revealed that Traditional Chinese Medicine (TCM) Artemisia argyit exhibited anti-Salmonella infection potential and inhibited flagellum-dependent motility. The application of Artemisia argyit essential oil induced notable motility defects through the downregulation of flagellar and fimbriae expression. Moreover, it significantly reduced Salmonella-infected cell damage by interfering with flagellum-mediated Salmonella colonization. In vivo studies demonstrated that Artemisia argyit essential oil administration effectively alleviated Salmonella infection symptoms by reducing bacterial loads, inhibiting interleukin-1 beta (IL-1β), IL-6, and tumor necrosis factor-alpha (TNF-α) production, and diminishing pathological injury. Gas chromatography-mass spectrometry (GC-MS) analysis identified forty-three compounds in Artemisia argyit essential oil, with their corresponding targets and active ingredients predicted. Investigation of an in vivo model of Salmonella infection using the active ingredient demonstrated that alpha-cedrene ameliorated Salmonella infection. These findings suggest the potential application of Artemisia argyit essential oil in controlling Salmonella, the predominant food-borne pathogen.
Artemisia/chemistry* ; Oils, Volatile/chemistry* ; Animals ; Flagella/drug effects* ; Salmonella Infections/microbiology* ; Humans ; Mice ; Anti-Bacterial Agents/pharmacology* ; Salmonella/pathogenicity*

OBJECTIVES: Calcium silicate (CSO) is modified to give it photothermal antibacterial properties. Its application potential in tooth mineralization and oral antibacterial is evaluated. METHODS: Based on defect-engineering modification strategy, a series of CSO-T samples (CSO-300, CSO-400, CSO-500, CSO-600) was obtained by introducing oxygen vacancy into CSO through thermal reduction using sodium borohydride. The samples were tested using scanning electron microscopy (SEM), X-ray diffraction, X-ray photoelectron spectroscopy, ultraviolet near-infrared absorption spectroscopy, and infrared thermography. The powder samples with the best photothermal performance and the most suitable material concentration (CSO-500, 500 μg/mL) were selected for subsequent experiments. High resolution transmission electron microscopy was used to analyze the microstructure and morphology of the sample, and MTT assay and Calcein AM/PI live/dead cell staining were used to evaluate the toxicity and compatibility of the sample to human oral keratinocytes. Escherichia coli and Staphylococcus aureus were selected for photothermal antibacterial experiments to evaluate their in vitro antibacterial performance. SEM, energy dispersive spectrometer, and micro Vickers hardness tester were used to evaluate the ability of materials to induce in vitro remineralization of detached teeth. RESULTS: Oxygen vacancies changed the crystal type and lattice spacing of CaSiO₃, broadened the light-absorption range, and gave it a good photothermal conversion ability in response to near infrared. Invitro experiments showed that the modified CaSiO₃ could promote the formation of hydroxyapatite on the tooth surface, thereby promoting the remineralization of teeth and improving the teeth hardness. Moreover, it had photothermal antibacterial properties and no cytotoxicity. CONCLUSIONS Defect-modified black calcium silicate has multiple functions, such as promoting tooth remineralization and photothermal bacteriostatic. When combined with the infrared luminescent toothbrush, it can simply and effectively treat tooth enamel erosion and oral bacteriostatic diseases caused by the excessive consumption of carbonated beverages and other daily bad living habits. This combination is expected to achieve the synergic treatment effect of tooth remineralization and oral bacteriostatic through daily cleaning is expected.
Calcium Compounds/pharmacology* ; Silicates/pharmacology* ; Humans ; Staphylococcus aureus/drug effects* ; Tooth Remineralization ; Escherichia coli/drug effects* ; Anti-Bacterial Agents/pharmacology* ; Keratinocytes/drug effects* ; Microscopy, Electron, Scanning

L-citrulline is a nonprotein amino acid that plays an important role in human health and has great market demand. Although microbial cell factories have been widely used for biosynthesis, there are still challenges such as genetic instability and low efficiency in the biosynthesis of L-citrulline. In this study, an efficient, plasmid-free, non-inducible L-citrulline-producing strain of Escherichia coli BL21(DE3) was engineered by combined strategies. Firstly, a chassis strain capable of synthesizing L-citrulline was constructed by block of L-citrulline degradation and removal of feedback inhibition, with the L-citrulline titer of 0.43 g/L. Secondly, a push-pull-restrain strategy was employed to enhance the L-citrulline biosynthesis, which realized the L-citrulline titer of 6.0 g/L. Thirdly, the NADPH synthesis and L-citrulline transport were strengthened to promote the synthesis efficiency, which achieved the L-citrulline titer of 11.6 g/L. Finally, fed-batch fermentation was performed with the engineered strain in a 3 L fermenter, in which the L-citrulline titer reached 44.9 g/L. This study lays the foundation for the industrial production of L-citrulline and provides insights for the modification of other amino acid metabolic networks.
Citrulline/biosynthesis* ; Escherichia coli/genetics* ; Metabolic Engineering/methods* ; Fermentation ; NADP/biosynthesis*

O-acetyl-L-homoserine (OAH) is a promising platform compound for the production of L-methionine and other valuable compounds, while its low yield and low conversion rate limit the industrial application. To solve these problems, we constructed a strain for high OAH production with the previously constructed L-homoserine producer Escherichia coli HS33 as the chassis by systematic metabolic engineering. Firstly, PEP accumulation, pyruvate utilization, and OAH synthesis pathway (overexpressing aspB, aspA, and thrA^C1034T) were enhanced to obtain an initial strain accumulating 13.37 g/L OAH. Subsequently, the co-factor synthesis genes were integrated to supply reducing power and energy, which increased the yield to 15.79 g/L. The OAH yield of the engineered strain OAH28 was further increased to 17.49 g/L by strengthening the acetic acid reuse pathway, improving the supply of acetyl-CoA, and regulating the expression of MetX from different sources. Finally, in a 5 L fermenter, OAH28 achieved an OAH titer of 47.12 g/L, with a glucose conversion rate of 32% and productivity of 0.59 g/(L·h). The results lay a foundation for increasing the OAH production by metabolic engineering and give insights into the industrial production of OAH.
Metabolic Engineering/methods* ; Escherichia coli/genetics* ; Homoserine/biosynthesis* ; Fermentation