Overview of Changes to the Clinical and Laboratory Standards Institute Performance Standards for Antimicrobial Susceptibility Testing, M100, 31st Edition

Unravelling the potential of natural chelating agents in the control of Staphylococcus aureus and Pseudomonas aeruginosa biofilms

Iron is essential for the formation, maturation and dispersal of bacterial biofilms, playing a crucial role in the physiological and metabolic functions of bacteria as well as in the regulation of virulence. Limited availability of iron can impair the formation of robust biofilms by altering cellular motility, hydrophobicity and protein composition of the bacterial surface. In this study, the antibiofilm activity of two natural iron chelating agents, kojic acid (5-hydroxy-2-hydroxymethyl-4H-pyran-4-one) and maltol (3-hydroxy-2-methyl-4-pyrone), were investigated against Staphylococcus aureus and Pseudomonas aeruginosa. In addition, the ability of these 2-hydroxy-4-pyrone derivatives in preventing and eradicating S. aureus and P. aeruginosa biofilms through the enhancement of the efficacy of two antibiotics (tobramycin and ciprofloxacin) was explored. The iron binding capacity of the kojic acid and maltol was confirmed by their affinity for iron (III) which was found to be about 90 %, comparable to the regular chelating agent ethylenediaminetetraacetic acid (EDTA, 89 %). The antibiofilm efficacy of 2-hydroxy-4-pyrone derivatives, alone and in combination with antibiotics, was evaluated by measuring the total biomass, metabolic activity, and culturability of biofilm cells. Furthermore, their impact on the membrane integrity of S. aureus biofilm cells was investigated using flow cytometry and epifluorescence microscopy with propidium iodide staining. It was also examined the ability of 2-hydroxy-4-pyrone derivatives and 2-hydroxy-4-pyrone derivate-antibiotic dual-combinations in inhibiting the production of virulence factors (total proteases, lipases, gelatinases and siderophores) by S. aureus. Regarding biofilm formation, the results showed that 2-hydroxy-4-pyrone derivatives alone reduced the metabolic activity of S. aureus biofilm cells by over 40 %. When combined with tobramycin, a 2-log (CFU cm-2) reduction in S. aureus biofilm cells was observed. Moreover, the combination of maltol and kojic acid with ciprofloxacin prevented P. aeruginosa biomass production by 60 %, compared to 36 % with ciprofloxacin alone. In pre-established S. aureus and P. aeruginosa biofilms, selected compounds reduced the metabolic activity by over 75 %, and a 3-log (CFU cm-2) reduction in the culturability of biofilm cells was noted when kojic acid and maltol were combined with antibiotics. Moreover, 2-hydroxy-4-pyrone derivatives alone and in combination with tobramycin, damaged the cell membranes of pre-established biofilms and completely inhibited total proteases production. Despite the increasing of reactive oxygen species production caused by the cellular treatment of maltol, both 2-hydroxy-4-pyrone derivatives showed good safe profile when tested in human hepatocarcinoma (HepG2) cells. The pre-treatment of HepG2 cells with both compounds was crucial to prevent the cellular damage caused by iron (III). This study demonstrates for the first time that the selected 2-hydroxy-4-pyrone derivatives significantly enhance the antibiofilm activity of tested antibiotics against S. aureus and P. aeruginosa, highlighting their potential as antibiotic adjuvants in preventing and eradicating biofilm-related infections.

Biosecurity Practices for Reducing Antimicrobial Use in Commercial Broiler Farms in Korea

Farm biosecurity is valuable for reducing the indiscriminate use of antimicrobials. However, its relationship with antimicrobial usage can be difficult to assess because of multiple factors. This study evaluated the impact of biosecurity practices on productivity, frequency of antimicrobial use, and development of antimicrobial resistance. Among factors related to biosecurity, mortality rate <2% within one week of age, survival rate >98%, and production index >350 in farms in which: bedding was not reused or only reused once, regular advice and biosecurity training was provided by poultry veterinarians, distinctions between clean and dirty areas were strictly enforced at all times, workers used farm biosecurity manuals, or disinfection guidelines were fully implemented, including cleaning before introducing new flocks and daily disinfection throughout growth, were significantly higher than those in farms without these measures (p < 0.05). The absence of biosecurity practices increased antimicrobial use to one (25.7%), two (39.2%), and three (25.7%) times (p < 0.05). In farms that implemented biosecurity practices, the antimicrobial administration was significantly increased to two times (44.2%) (p < 0.05), with only 17.4% of farms using antimicrobials three times. The prevalence of environmental Escherichia coli resistant to multiple cephalosporins and chloramphenicol, which are not used on broiler farms, was significantly reduced by biosecurity practices (p < 0.05). Our findings indicate that improved biosecurity practices decrease antimicrobial use, decrease the incidence of antimicrobial-resistant bacteria, and help to eliminate resistant bacteria in farm environments.

Fusarium oxysporum assisted green synthesis of small-sized silver nanoparticles for high antibacterial, and photocatalytic decolorization performances

BACKGROUND

Novel platforms using nanotechnology-based medicines have exponentially increased in our daily lives. The unique characteristics of metal oxide and noble metals nanoparticles make them suitable for different fields including antimicrobial agents, cosmetics, textiles, wound dressings, and anticancer drug carriers.

METHODS

This study focuses on the biosynthesis of small-sized SNPs using exo-metabolites of Fusarium oxysporum via bioprocess optimization using Plackett-Burman (PBD) and central composite designs (CCD) while evaluating their multifaceted bioactivities.

RESULTS

The successful biofabrication of smaller-sized SNPs with an average particle size of ~ 5 nm was achieved upon the bioprocess optimization. The developed SNPs exhibited significant antibacterial activity against multidrug-resistant bacterial pathogens in a concentration- and time-dependent manner. The minimum inhibitory concentrations (MICs) for SNPs were 0.078 µg/ml (Escherichia coli), 0.156 µg/ml (Pseudomonas aeruginosa), and 1.25 µg/ml (Enterococcus faecalis), while the minimum bactericidal concentrations (MBCs) were correspondingly 0.156 µg/ml, 0.312 µg/l, and 1.25 µg/ml. SNPs-treated cells displayed bacteriostatic and bactericidal effects as revealed by time-kill assay and the ultrastructure changes observed in SEM and TEM analyses. The results marked the potent antioxidant activity of SNPs against DPPH, O2•-, H2O2, and OH-radicals with IC50 values of 74.3, 96.7, 116.6, and 167.9 µg/ml, respectively. Significantly, the biosynthesized SNPs displayed cytotoxic activity on MCF-7, A549, and HepG-2 cell lines with IC50 values of 89.4, 121.4, and 138.9 µg/ml, respectively. SNPs exhibited promising photocatalytic efficiency at different concentrations and times compared with dark conditions. The highest decolorization percentage of crystal violet dye was 98.60% after 240 min at 100 µg SNPs concentration.

CONCLUSIONS

The green synthesis of SNPs by F. oxysporum exometabolites is eco-friendly, and inexpensive, with the production of small-size, and greatly stabilized nanoparticles. This study corroborated that SNPs can be highly promising enough to be applied for antibacterial and anticancer control systems, for ameliorating free radical-related disorders, and as a photocatalyst for wastewater treatment.

Methionine-driven methylation modification overcomes plasmid-mediated high-level tigecycline resistance

Tigecycline is a last-resort antibiotic to treat complicated infections caused by multidrug-resistant pathogens, while the emergence of plasmid-mediated tet(X) family severely compromises its clinical efficacy. Novel antimicrobial strategies not limited to new antibiotics in pharmaceutical pipeline are urgently needed. Herein, we reveal the metabolic disparities between tet(X)-negative and -positive E. coli, including distinct energy demand patterns under tigecycline exposure. In particular, the cysteine and methionine metabolism pathway is remarkably downregulated in tet(X)-positive bacteria. More importantly, we find that the addition of exogenous L-methionine (Met) effectively resensitizes tet(X)-positive pathogens to tigecycline. Our mechanistic analysis demonstrates that exogenous Met promotes intracellular tigecycline accumulation by upregulating bacterial proton motive force. Moreover, Met accelerates the conversion to S-adenosyl-L-methionine, an essential methyl donor, thereby enhancing 5mC methylation modification in the promoter region of tet(X4) gene and reducing its expression. Consistently, the potentiation of Met to tigecycline is abolished in tet(X4)-carrying E. coli Δdcm but restored in dcm-complementary bacteria, which encodes DNA-cytosine methyltransferase. In multiple animal models of infection, Met markedly potentiates the effectiveness of tigecycline against pathogenic E. coli and K. pneumoniae. Overall, this work highlights the therapeutic potential of Met in overcoming plasmid-mediated high-level tigecycline resistance, and provides a new paradigm to enhance antibiotic efficacy by harnessing cellular metabolic networks as well as epigenetic modifications.

Isolation and characterization of ɸEcM-vB1 bacteriophage targeting multidrug-resistant Escherichia coli

OBJECTIVES

The aim of this study is to screen for, isolate and characterize a bacteriophage designated ɸEcM-vB1 with confirmed lytic activity against multidrug-resistant (MDR) E. coli. Methods done in this research are bacteriophage isolation, purification, titer determination, bacteriophage morphology, host range determination, bacteriophage latent period and burst size determination, genomic analysis by restriction enzymes, and bacteriophage total protein content determination.

RESULTS

ɸEcM-vB1 bacteriophage exhibited high lytic activity against different MDR E. coli isolates and showed stability over wide pH and temperature range. It belongs to the Myoviridae family of the caudovirales order according to TEM. It had a latent period of 5 min and an average burst size of 271.72 pfu/cell. Genomic analysis revealed that it is susceptible to digestion by EcoRI. Ten structural proteins were detected by SDS-PAGE. ɸEcM-vB1 is considered a promising candidate for phage therapy applications.

Synergistic antibacterial effect of ginsenoside Rh2 and calcium hydroxide on Enterococcus faecalis

Treatment of root canal infections becomes more challenging due to the extremely high tolerance of Enterococcus faecalis (E. faecalis) to calcium hydroxide (Ca(OH)2). Ginsenoside is a Chinese herbal extract that has been proven to have antimicrobial properties and synergistic activities. And this study evaluated the antibacterial activity of ginsenoside Rh2 in combination with Ca(OH)2 against E. faecalis and its preliminary mechanism of action. Broth microdilution method, checkerboard dilution method, time-inhibition curve, drug resistance assays, scanning electron microscopy, and biofilm inhibition and removal assays indicated that Rh2 in combination with Ca(OH)2 exhibited potent antibacterial activity against E. faecalis. Rh2 exerted significant in vitro antibacterial activity against E. faecalis, with a minimum inhibitory concentration (MIC) of 3.125 μg/mL and minimum bactericidal concentration (MBC) of 6.25 μg/mL, and significantly enhanced the susceptibility of E. faecalis to Ca(OH)2 (FICI = 0.5). Furthermore, cell membrane permeability assays, surface hydrophobicity assays, ATPase activity assays, and intra-biofilm extracellular polysaccharides (EPS) assays revealed that Rh2 and Ca(OH)2 synergistically inhibit bacteria mainly by increasing membrane permeability. Ultimately, cytotoxicity assays showed that Rh2 exhibited only low toxicity, the half maximal inhibitory concentration (IC50) of Rh2 was 19.75 μg/mL. This study confirmed the synergistic antibacterial activities of Rh2 and Ca(OH)2 against E. faecalis. Our findings indicate that the Rh2 and Ca(OH)2 combination may be a promising alternative approach to treating root canal infections.

Extended structure-activity relationship studies of the [1,2,5]oxadiazolo[3,4-b]pyrazine-containing colistin adjuvants

Antimicrobial resistance (AMR) is a formidable global health challenge. Multidrug-resistant (MDR) Gram-negative bacterial infections are of primary concern due to diminishing treatment options and high morbidity and mortality. Colistin, a polymyxin family antibiotic, is a last-resort treatment for MDR Gram-negative infections, but its wider use has resulted in escalating resistance. In 2022, using a screening approach, we discovered that a [1,2,5]oxadiazolo[3,4-b]pyrazine (ODP)-containing compound selectively re-sensitized various MDR Gram-negative bacteria to colistin. Initial structure-activity relationship (SAR) studies confirmed that bisanilino ODP compounds are colistin adjuvants with low mammalian toxicity. Herein, we report our extended SAR studies on a wide range of ODP analogs bearing alkyl- or arylalkylamines. Specifically, we discovered two new compounds, 5q and 8g, with potent colistin-potentiating activity and low mammalian toxicity in a wide range of clinically relevant pathogens.

Application of green silver nano-particles as anti-bacterial and photo-catalytic degradation of azo dye in wastewater

Ensuring everyone enjoys healthy lifestyles and well-being at all ages, Progress has been made in increasing access to clean water and sanitation facilities and reducing the spread of epidemics and diseases. The synthesis of nano-particles (NPs) by using microalgae is a new nanobiotechnology due to the use of the biomolecular (corona) of microalgae as a capping and reducing agent for NP creation. This investigation explores the capacity of a distinct indigenous microalgal strain to synthesize silver nano-particles (AgNPs), as well as its effectiveness against multi-drug resistant (MDR) bacteria and its ability to degrade Azo dye (Methyl Red) in wastewater. An extract of Spirulina platensis was obtained from a local source to synthesize silver nano-particles (AgNPs). The synthesized AgNPs were subsequently subjected to characterization utilizing several analytical methods, namely UV-visible spectroscopy, scanning electron microscopy (SEM), X-ray diffraction, and Fourier transform infrared spectroscopy (FTIR analysis). Subsequently, the disc diffusion method assessed their anti-bacterial efficacy against multi-drug resistant (MDR) bacteria and their ability to degrade Azo dye (Methyl Red) in wastewater. The nano-particles produced through biological synthesis exhibited a prominent peak in the UV-visible spectrum at a wavelength of 430 nm. Furthermore, these nano-particles were determined to possess a crystalline nature, with an average size of 28.72 nm and a distinctive star-like shape. The synthesized silver nano-particles (AgNPs) exhibited a dose-dependent anti-bacterial effect against some clinical bacterial isolates as multi-drug resistant (MDR), including Gram- ve bacteria such as Pseudomonas aeruginosa and Escherichia coli, as well as Gram+ ve bacteria like Staphylococcus aureus and Streptococcus pneumoniae. The action can be ascribed to the unique biological and physicochemical features of AgNPs, which facilitate the disruption of bacterial cell membranes. The UV-visible analysis solution after the introduction of AgNPs indicated that the decrease in the absorbance peak of methyl red was attributed to the existence of silver nano-particles. Metal nano-particles can be synthesized using environmentally friendly processes and hold great potential for combating multi-drug resistant bacteria and degrading Azo dyes. Silver nano-particles (AgNPs) are synthesized with an extract derived from the algae Spirulina platensis, which is a sustainable and eco-friendly alternative.

Antimicrobial resistance profile, biofilm forming capacity and associated factors of multidrug resistance in Pseudomonas aeruginosa among patients admitted at Tikur Anbessa Specialized Hospital and Yekatit 12 Hospital Medical College in Addis Ababa, Ethiopia

BACKGROUND

Pseudomonas aeruginosa is one of the leading causes of nosocomial infections and the most common multidrug-resistant pathogen. This study aimed to determine antimicrobial resistance patterns, biofilm-forming capacity, and associated factors of multidrug resistance in P. aeruginosa isolates at two hospitals in Addis Ababa, Ethiopia.

METHODS

A cross-sectional study was conducted from August 2022 to August 2023 at Tikur Anbessa Specialized Hospital and Yekatit 12 Hospital Medical College. Culture and identification of P. aeruginosa were done using standard microbiological methods. An antimicrobial susceptibility test was done by Kirby-Bauer disk diffusion according to CLSI recommendations. The microtiter plate assay method was used to determine biofilm-forming capacity. SPSS version 25 was used for data analysis. Bivariate and multivariable logistic regression were used to assess factors associated with multidrug resistance in P. aeruginosa. The Spearman correlation coefficient (rs = 0.266)) was performed to evaluate the relationship between biofilm formation and drug resistance.

RESULTS

The overall prevalence of P. aeruginosa was 19.6%. High levels of resistance were observed for ciprofloxacin (51.8%), ceftazidime (50.6%), and cefepime (48.2%). The level of multidrug-resistance was 56.6%. The isolates showed better susceptibility to ceftazidime-avibactam (95.2%) and imipenem (79.5%). Overall, 95.2% of P. aeruginosa were biofilm-producing isolates, and 27.7% and 39.8% of isolates were strong and moderate biofilm producers, respectively. A positive correlation and statistically significant relationship was observed between resistance to multiple drugs and the level of biofilm formation (rs = 0.266; p-value = 0.015). Previous history of exposure to ciprofloxacin (OR, 5.1; CI, 1.12-24.7, p-value, 0.032) was identified as an independent associated factor for multidrug resistance in P. aeruginosa.

CONCLUSION

The present study indicates an association between multidrug resistance in P. aeruginosa and its biofilm formation capabilities. Additionally, over half of the isolates were resistant to multiple drugs, with prior use of ciprofloxacin linked to the development of multidrug-resistance. These findings suggest that antibiotic stewardship programs in hospital settings may be beneficial in addressing resistance.

Antimicrobial resistance of Escherichia coli in cats and their drinking water: drug resistance profiles and antimicrobial-resistant genes

BACKGROUND

Antimicrobial resistance (AMR) is a global health concern that is exacerbated by the transmission of bacteria and genetic material between humans, animals and the environment. This study investigated AMR of Escherichia coli (E. coli) isolated from cats' feces and their drinking water. The study compared the AMR of fecal and environmental E. coli isolates from pet cats.

RESULTS

A total of 104 samples (52 cat feces and 52 cat drinking water samples) was cultured for E. coli. The study compared the AMR of fecal and environmental E. coli isolates from pet cats. An analysis of carbapenemase and extended-spectrum β-lactamase (ESBL)-producing E. coli genes (blaTEM, blaSHV and blaCTX-M) and phylogroups of E. coli was also performed. E. coli was identified from all fecal (100%) and almost half of drinking water (44.2%) samples. All E. coli isolate was susceptible to amikacin or imipenem. Clindamycin showed the highest resistance rate. β-lactam was the most found with co-resistance profiles, comprising β-lactams with aminoglycosides, quinolones, sulfonamides, macrolides or carbapenems. Very strong positive correlations of bactericidal agents were found among quinolones (r > 0.8, p < 0.01). Within the group of bacteriostatic agents, moderate correlation was observed between azithromycin and sulfa-trimethoprim (r = 0.5253, p < 0.01). Carbapenemase gene was not detected in this study. Extended-spectrum β-lactamase-producing E. coli genes (blaTEM, blaSHV and blaCTX-M) were identified in E. coli isolates, with blaTEM being the most predominant. Furthermore, phylogroup B2 was the dominant segregation among the E. coli, particularly in fecal isolates.

CONCLUSIONS

This study identified AMRin E. coli isolated from cats' feces and their drinking water.  The results revealed that the phylogroup B2 was predominant, with blaTEM being the most widespread ESBL gene.

Vanillin Has Potent Antibacterial, Antioxidant, and Anti-Inflammatory Activities In Vitro and in Mouse Colitis Induced by Multidrug-Resistant Escherichia coli

A large number of cases of infectious colitis caused by multidrug-resistant (MDR) bacteria, such as Escherichia coli, can result in colon damage and severe inflammation. Vanilla, a widely utilized flavor and fragrance compound, is extensively used in various food. However, the effect of vanilla on MDR E. coli-induced infectious colitis has received less attention. In this study, the antibacterial activity of vanillin against MDR E. coli and other bacteria was determined by the microtiter broth dilution method. The antioxidant and anti-inflammatory capacity of vanillin was assessed in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells and MDR E. coli-induced mouse colitis. The results demonstrated that vanillin exhibited potent antibacterial activity against various strains of MDR E. coli, Salmonella, and Staphylococcus aureus, with a minimal inhibitory concentration (MIC) of 1.25-2.5 mg/mL and a minimum bactericidal concentration (MBC) of 5-10 mg/mL; it effectively inhibited cell division in E. coli. Vanillin also displayed remarkable antioxidant activity by suppressing the levels of malondialdehyde (MDA), superoxide dismutase (SOD), and reactive oxygen species (ROS) in LPS-stimulated RAW 264.7 cell; it significantly reduced the production of inflammatory mediators including nitroxide (NO), tumor necrosis factor α (TNF-α), interleukin 6 (IL-6), and interleukin 1β (IL-1β), while increasing interleukin 10 (IL-10). In an MDR E. coli-induced mouse colitis model, vanillin effectively inhibited inflammation by suppressing inflammatory cytokines, mitogen-activated protein kinase (MAPK), and nuclear factor κ-B (NF-κB) cell signaling pathway activation; it ameliorated changes in intestinal microflora characterized by decreased Firmicutes richness alongside increased Bacteroides richness, rebalancing the dysbiosis caused by E. coli. These findings highlight the potential pharmacological applicability of vanillin as a promising bioactive molecule for treating infectious colitis.

Sub-minimum inhibitory concentrations in ceftazidime exacerbate the formation of Acinetobacter baumannii biofilms

Associated with nosocomial infections, the environmental Gram-negative coccobacillus A. baumannii leads to various kinds of high mortality-rate infections among which pneumonias mainly in immune-compromised people from health-care facilities. A critical component of the current antibiotic resistance problem is the presence of antibiotics sub-minimum inhibitory concentrations (sub-MICs) in a variety of natural settings including drinking water, sewage water, rivers, lakes, and natural sludge. In India, third-generation cephalosporins such as ceftazidime (CAZ) count among the most often prescribed β-lactams to treat infections by A. baumannii. In this study, we showed that CAZ sub-MICs 1/reduce adhesion to lung epithelial cells and slow down the growth of the A. baumannii KSK1 strain, which nevertheless quickly resumes its growth; 2/alter the morphology of A. baumannii KSK1 planktonic cells and induce the formation of bacterial aggregates that resemble biofilms; 3/increase the in vitro formation of biofilms by A. baumannii KSK1 bacterial cells. Our findings underscore the importance of considering sub-MICs in antibiotic therapy and environmental contamination as the antibiotics sub-MICs potentially found in wastewater may contribute to the selection causing antibiotic resistance and persistence of antibiotic-resistant strains.

Advancements of paper-based sensors for antibiotic-resistant bacterial species identification

Evolution of antimicrobial-resistant bacterial species is on a rise. This review aims to explore the diverse range of paper-based platforms designed to identify antimicrobial-resistant bacterial species. It highlights the most important targets used for sensor development and examines the applications of nanosized particles used in paper-based sensors. This review also discusses the advantages, limitations, and applicability of various targets and detection techniques for sensing drug-resistant bacterial species using paper-based platforms.

Clinical and In Vitro Safety of Heyndrickxia coagulans AO 1167B: A Double-Blind, Placebo-Controlled Trial

(1) Background: Heyndrickxia coagulans, a lactic acid-producing bacterium, displays characteristics of both Lactobacillus and Bacillus genera. Clinical evidence suggests its potential health benefits. This study evaluated the safety of H. coagulans AO1167B as a candidate probiotic supplement. (2) Methods: Strain identification was confirmed through morphological, cultural, and genomic analyses, including 16S RNA and whole genome sequencing to assess antimicrobial resistance and virulence factors. Phenotypic tests, such as disk diffusion for antimicrobial resistance, and safety assays for cytotoxicity and hemolytic activity, were conducted. In a phase I, double-blind, placebo-controlled clinical trial, healthy adults were randomized into H. coagulans AO1167B and placebo groups for 60 days. Daily capsule consumption was monitored through clinical and hematological evaluations, adverse event tracking, and health surveys. (3) Results: The genome of H. coagulans AO1167B revealed no concerning features. Disk diffusion tests showed no antimicrobial resistance. The strain exhibited no cytotoxic or hemolytic activity, indicating in vitro safety. No significant differences in clinical or hematological parameters were observed between groups. The most common adverse event, gas, diminished over time. (4) Conclusions: H. coagulans AO1167B demonstrates a suitable safety profile, genetic stability, and probiotic potential for gastrointestinal health, justifying further clinical research.

Decoding the enigma: unveiling the transmission characteristics of waterfowl-associated bla NDM-5-positive Escherichia coli in select regions of China

Escherichia coli (E. coli) serves as a critical indicator microorganism for assessing the prevalence and dissemination of antibiotic resistance, notably harboring various antibiotic-resistant genes (ARGs). Among these, the emergence of the bla NDM gene represents a significant threat to public health, especially since carbapenem antibiotics are vital for treating severe infections caused by Gram-negative bacteria. This study aimed to characterize the antibiotic resistance features of bla NDM-5-positive E. coli strains isolated from waterfowl in several regions of China and elucidate the dissemination patterns of the bla NDM-5 gene. We successfully isolated 103 bla NDM-5-positive E. coli strains from 431 intestinal fecal samples obtained from waterfowl across five provincial-level units in China, with all strains exhibiting multidrug resistance (MDR). Notably, the bla NDM-5 gene was identified on plasmids, which facilitate efficient and stable horizontal gene transfer (HGT). Our adaptability assays indicated that while the bla NDM-5-positive plasmid imposed a fitness cost on the host bacteria, the NDM-5 protein was successfully induced and purified, exhibiting significant enzymatic activity. One strain, designated DY51, exhibited a minimum inhibitory concentration (MIC) for imipenem of 4 mg/L, which escalated to 512 mg/L following exposure to increasing imipenem doses. This altered strain demonstrated stable resistance to imipenem alongside improved adaptability, correlating with elevated relative expression levels of the bla NDM-5 and overexpression of efflux pumps. Collectively, this study highlights the horizontal dissemination of the bla NDM-5 plasmid among E. coli strains, confirms the associated fitness costs, and provides insights into the mechanisms underlying the stable increase in antibiotic resistance to imipenem. These findings offer a theoretical framework for understanding the dissemination dynamics of bla NDM-5 in E. coli, which is essential for developing effective strategies to combat carbapenem antibiotic resistance.

Effects of different carbapenemase and siderophore production on cefiderocol susceptibility in Klebsiella pneumoniae

The resistance mechanism of Gram-negative bacteria to the siderophore antibiotic cefiderocol is primarily attributed to carbapenemase and siderophore uptake pathways; however, specific factors and their relationships remain to be fully elucidated. Here, we constructed cefiderocol-resistant Klebsiella pneumoniae (CRKP) strains carrying different carbapenemases and knocked out siderophore genes to investigate the roles of various carbapenemases and siderophores in the development of cefiderocol resistance. Antimicrobial susceptibility testing revealed that both blaNDM and blaKPC significantly increased the minimum inhibitory concentration (MIC) of Klebsiella pneumoniae (KP) to cefiderocol, while blaOXA-48 showed a modest increase. Notably, KP expressing NDM exhibited a higher cefiderocol MIC compared to KP expressing KPC, although expression of NDM alone did not induce cefiderocol resistance. Laboratory evolutionary experiments demonstrated that combining pNDM with mutations in the siderophore uptake receptor gene cirA and pKPC with a mutation in the two-component system gene envZ led to KP reaching a high level of cefiderocol resistance. Although combining pOXA with mutations in the two-component system gene baeS did not induce cefiderocol resistance, it significantly reduced susceptibility. Moreover, siderophores could influence the development of cefiderocol resistance. Strains deficient in enterobactin exhibited increased susceptibility to cefiderocol, while deficiencies in yersiniabactin and salmochelin showed no significant alterations. In conclusion, carbapenemase gene expression facilitates cefiderocol resistance, but its presence alone is insufficient. Cefiderocol resistance in CRKP typically involves abnormal expression of certain genes and other factors, such as mutations in siderophore uptake receptor genes and two-component system genes. The enterobactin siderophore synthesis gene entB may also contribute to resistance.

Phenotypic antibiotic resistance of Mycoplasma genitalium and its variation between different macrolide resistance-associated mutations

OBJECTIVES

Mycoplasma genitalium, a sexually transmitted bacterium, faces increasing antibiotic resistance, particularly to azithromycin. However, presence of macrolide resistance-associated mutations (MRAMs) does not evidently implicate azithromycin treatment failure. This study aimed to establish an in vitro co-culture system of M. genitalium isolates and perform phenotypic susceptibility testing for different antibiotics, focusing on azithromycin to evaluate genotypic and phenotypic resistance across MRAMs.

METHODS

Urine specimens testing positive for M. genitalium via nucleic acid amplification were co-cultured with Vero cells. Phenotypic susceptibility testing was performed for eight antibiotics. Growth inhibition and MIC of M. genitalium by azithromycin were compared across different MRAMs.

RESULTS

M. genitalium was cultured from 20/40 (50.0%) positive urine samples, with phenotypic susceptibility tested in a subset. MICs ranged as follows: azithromycin (0.008->32 mg/L), levofloxacin (1-4 mg/L), moxifloxacin (<0.25-1 mg/L), sitafloxacin (<0.032-0.25 mg/L), minocycline (<0.25-1 mg/L), doxycycline (<0.125-2 mg/L), spectinomycin (<2.5->25 mg/L) and lefamulin (<0.004-0.063 mg/L). Isolates with A2058T demonstrated 24-, 7-, 15- and 12-fold increases in growth inhibition compared with A2058G at azithromycin concentrations of 4, 8, 16 and 32 mg/L, respectively (P < 0.01). MRAMs ranked from low to high impact on MIC range were as follows: wildtype (0.008-0.016), A2058T (8-32), A2059G (≥32) and A2058G (>32).

CONCLUSIONS

This study revealed that M. genitalium isolates vary in azithromycin-induced growth inhibition across MRAMs, potentially explaining differences in clinical treatment efficacy. Phenotypic susceptibility testing for other antibiotics demonstrated relatively low MICs. Future studies should incorporate clinical treatment efficacy and symptom severity to optimize treatment for M. genitalium.

Efficacy of colistin-based combinations against pandrug-resistant whole-genome-sequenced Klebsiella pneumoniae isolated from hospitalized patients in Egypt: an in vitro/vivo comparative study

BACKGROUND

Colistin resistance significantly constrains available treatment options and results in the emergence of pandrug-resistant (PDR) strains. Treating PDR infections is a major public health issue. A promising solution lies in using colistin-based combinations. Despite the availability of in vitro data evaluating these combinations, the in vivo studies remain limited.

RESULTS

Thirty colistin-resistant Klebsiella pneumoniae (ColRKp) isolates were collected from hospitalized patients. Colistin resistance was detected using broth microdilution, and antimicrobial susceptibility was tested using the Kirby-Bauer method against 18 antibiotics. Extremely high resistance levels were detected, with 17% of the isolates being PDR. Virulence profiling, assessed using Anthony capsule staining, the string test, and the crystal violet assay, indicated the predominance of non-biofilm formers and non-hypermucoid strains. The isolates were screened for mcr genes using polymerase chain reaction. Whole-genome sequencing (WGS) and bioinformatics analysis were performed to characterize the genomes of PDR isolates. No plasmid-borne mcr genes were detected, and WGS analysis revealed that PDR isolates belonged to the high-risk clones: ST14 (n = 1), ST147 (n = 2), and ST383 (n = 2). They carried genes encoding extended-spectrum β-lactamases and carbapenemases, blaCTX-M-15 and blaNDM-5, on conjugative IncHI1B/IncFIB plasmids, illustrating the convergence of virulence and resistance genes. The most common mechanism of colistin resistance involved alterations in mgrB. Furthermore, deleterious amino acid substitutions were also detected within PhoQ, PmrC, CrrB, ArnB, and ArnT. Seven colistin-containing combinations were compared using the checkerboard experiment. Synergy was observed when combining colistin with tigecycline, doxycycline, levofloxacin, ciprofloxacin, sulfamethoxazole/trimethoprim, imipenem, or meropenem. The efficacy of colistin combined with either doxycycline or levofloxacin was assessed in vitro using a resistance modulation assay, and in vivo, using a murine infection model. In vitro, doxycycline and levofloxacin reversed colistin resistance in 80% and 73.3% of the population, respectively. In vivo, the colistin + doxycycline combination demonstrated superiority over colistin + levofloxacin, rescuing 80% of infected animals, and reducing bacterial bioburden in the liver and kidneys while preserving nearly intact lung histology.

CONCLUSIONS

This study represents the first comparative in vitro and in vivo investigation of the efficacy of colistin + doxycycline and colistin + levofloxacin combinations in clinical PDR ColRKp isolates characterized at a genomic level.

Assessment of anti-MRSA activity of auranofin and florfenicol combination: a PK/PD analysis

AIMS

Methicillin-resistant Staphylococcus aureus (MRSA) is an important zoonotic pathogen with multidrug-resistant phenotypes increasingly prevalent in both human and veterinary clinics. This study evaluated the potential of auranofin (AF) as an antibiotic adjuvant to enhance the anti-MRSA activity of florfenicol (FFC) and established a pharmacokinetic/pharmacodynamic (PK/PD) model to compare the efficacy of FFC alone or in combination with AF against MRSA.

METHODS AND RESULTS

We observed an increased susceptibility and significant synergistic effects of MRSA to FFC in the presence of AF. The combination treatment of FFC and AF significantly inhibited MRSA biofilm formation and decreased the metabolic activity of mature biofilms. Importantly, AF fully restored the efficacy of FFC in both Galleria mellonella larvae and murine models. PK/PD studies demonstrated that the AUC24h/MIC targets required to achieve the bacteriostatic and bactericidal effects were significantly lower with the combination therapy compared to florfenicol monotherapy.

CONCLUSIONS

These results reveal the potential of AF as a novel adjuvant to improve the efficacy of FFC in treating MRSA invasive infections and provide valuable PK/PD insights for designing effective combination therapies.

Advances in the clinical treatment of multidrug-resistant pathogens using polymyxins

OBJECTIVES

Polymyxins are a vital class of antibiotics used to combat multidrug-resistant Gram-negative bacteria. However, their use is limited due to potential nephrotoxicity and the availability of alternative antibiotics. This review aims to examine the properties of polymyxins and the clinical advances in their use for treating infections caused by carbapenem-resistant Gram-negative bacteria (CR-GNB).

METHODS

This review analyses literature on polymyxin properties and various clinical approaches, including intravenous drip infusion, nebulized or dry powder inhalation, and ointment application. Treatment efficacy in terms of bacterial eradication, cure rate and mortality rate are reviewed and evaluated.

RESULTS

Polymyxins have been reintroduced to treat critical infections due to the increasing prevalence of CR-GNB. Clinical trials and studies have confirmed that polymyxins can effectively treat CR-GNB infections when the formulation and administration are appropriate, with acceptable levels of nephrotoxicity.

CONCLUSIONS

In the future, the development of polymyxin formulations will aim to improve their clinical effectiveness while reducing toxicity and side effects and preventing the emergence of polymyxin-resistant strains. Enhanced efficacy and minimized potential side effects can be achieved by developing new polymyxin-delivery systems that provide a smart and controlled release or customized patient administration.

Nasal carriage of MRSA among clinically affiliated undergraduate students at the College of Health and Medical Sciences, Haramaya University, Ethiopia

Medical and health science students are among the demographics most at risk from Methicillin-resistant Staphylococcus aureus (MRSA), which is a serious hazard to public health. The main reservoir for MRSA is the nasal cavity, and colonization of this area can raise the risk of infection and transmission in healthcare settings. This study aimed to assess the nasal carriage rate of MRSA among clinically affiliated students at Haramaya University, College of Health and Medicine Sciences, Ethiopia, from July to August 2022. An institution-based cross-sectional study of 250 study participants was conducted using a stratified random sampling methods. The data were collected via structured questionnaires. Nasal swabs were cultured on mannitol salt agar and blood agar at 37 °C for 24 h. Staphylococcus aureus was identified using catalase and coagulase tests. The MRSA was screened using the cefoxitin disk diffusion method on Muller Hinton agar. The data were entered and analyzed by SPSS version 25. Pearson's chi-square test was performed to predict associations between variables. A p value less than 0.05 was regarded as statistically significant. The nasal carriage rate of S. aureus was 8% (95% CI: 4.6-11.3%). The Nasal carriage rate of MRSA was 4.8% (95% CI: 2.1-7.4%). Overall, 4.8% of all the students were identified as MRSA carriers. MRSA carriage was high among medical students (33.3%). Nose-picking habit (X2 = 16.7, P = 0.001) and dormitory occupancy (X2 = 3.6, P = 0.045) were significantly associated with the MRSA rate. All the MRSA strains were resistant to penicillin and ampicillin. However, all the MRSA strains were susceptible to chloramphenicol and clindamycin. This study revealed that MRSA is a threat due to significant resistance. Nasal carriage is associated with nose picking and dorm occupancy. Encourage practices such as avoiding nose picking and maintaining personal cleanliness. Regular cleaning and disinfection of shared spaces can reduce the presence of MRSA.

Bactericidal and anti-quorum sensing activity of repurposing drug Visomitin against Staphylococcus aureus

With the growing antibiotic resistance in Staphylococcus aureus, it is imperative to develop innovative therapeutic strategies against new targets to reduce selective survival pressures and incidence of resistance. In S. aureus, interbacterial communication relies on a quorum sensing system that regulates gene expression and physiological activities. Here, we identified that Visomitin, an antioxidant small molecule, exhibited bactericidal efficacy against methicillin-resistant S. aureus and its high tolerance phenotypes like intracellular bacteria and persister cells without inducing resistance. Critically, sub-minimal inhibitory concentrations (sub-MICs) of Visomitin could serve as a potent quorum-quencher reducing virulence production (such as haemolysin and staphyloxanthin), along with inhibiting biofilm formation, self-aggregation, and colony spreading of S. aureus. These effects were probably mediated by interfering with the S. aureus accessory gene regulator quorum sensing system. In summary, our findings suggest that Visomitin shows dual antimicrobial effects, including bactericidal effects at the concentrations above MIC and quorum sensing inhibition effects at sub-MICs, which holds promise for treating MRSA-related refractory infections.

Colistin-niclosamide effervescent dry suspension combats colistin-resistant Salmonella in vitro and in vivo

The increasing incidence of bacterial infections caused by multidrug-resistant (MDR) Gram-negative bacteria has deepened the need for new effective treatments. It has been reported that niclosamide (NIC) can restore the sensitivity of Gram-negative bacteria to colistin (COL). However, NIC is practically insoluble in water and sparingly soluble in organic solvents, leading to limited therapeutic applications. This study aims to prepare a COL-NIC effervescent dry suspension (CNEDS) and evaluate its antibacterial effect against COL-resistant Salmonella both in vitro and in broiler chickens. With the sedimentation volume ratio as an index, suitable suspending agent, wetting agent, filler and effervescent agent were screened through a single-factor method. The preparation conditions were optimized using the Box-Behnken response surface method to obtain the formulation for CNEDS. The quality evaluation results showed that the successfully prepared CNEDS had a sedimentation volume ratio of 0.99, a drying weight loss of 1.3%, and a re-dispersion capability of 1-2 times, all of which met pharmacopoeial requirements. In terms of pharmacological evaluation, we first demonstrated that CNEDS substantially restored COL sensitivity against COL-resistant bacteria. Subsequently, time-killing analysis, scanning electron microscopy (SEM) and live/dead assays confirmed the antibacterial activity of CNEDS against COL-resistant bacteria. Finally, a Salmonella infection model in broiler chickens was established to further assess the therapeutic effect of CNEDS in vivo. CNEDS improved the survival rate of broiler chickens, reduced the bacterial burden on organs. These findings suggest that CNEDS effectively overcome COL resistance, indicating its potential for the treatment of COL-resistant bacterial infections in broiler chickens.

Effectiveness of combination therapy with intrathecal or intraventricular administration of polymyxin B for hospital-acquired central nervous system infections caused by carbapenem-resistant Acinetobacter baumannii: A retrospective study

OBJECTIVES

To evaluate the therapeutic regimen, efficacy and safety of intrathecal or intraventricular (ITH/IVT) administration of polymyxin B for hospital-acquired central nervous system (CNS) infections caused by carbapenem-resistant Acinetobacter baumannii (CRAB).

METHODS

A retrospective study was undertaken of patients with CNS infections caused by CRAB treated with ITH/IVT combination therapy. The primary outcome was the clinical efficacy of treatment. The secondary outcomes were the bacterial clearance rate and the safety of therapy.

RESULTS

In total, 35 patients who received ITH [n=13 (37.1%)] or IVT [n=22 (62.9%)] polymyxin B as combination therapy were included in this study. The median duration of ITH/IVT polymyxin B therapy was 9 (interquartile range 7-11) days. The overall clinical cure rate and bacterial clearance rate were 77.1% and 85.7%, respectively. No adverse effects considered to be related to ITH/IVT polymyxin B were recorded. Clinical failure was independently associated with an Acute Physiology and Chronic Health Evaluation II score ≥15 [odds ratio (OR) 1.24, 95% confidence interval (CI) 1.05-1.42; P=0.038] and a Glasgow Coma Scale score ≤8 (OR 0.69, 95% CI 0.49-0.88; P=0.029). Early administration (≤4 days of infection onset) of ITH/IVT polymyxin B therapy resulted in a significantly higher clinical cure rate (OR 0.65, 95% CI 0.49-1.12; P<0.001), and may reduce the length of treatment and adverse effects.

CONCLUSIONS

ITH/IVT administration of polymyxin B is a valid alternative for the treatment of CNS infections caused by CRAB. Early use of ITH/IVT polymyxin B can result in greater clinical success.

Prevalence of pathogens and antimicrobial resistance of isolated Staphylococcus spp. in bovine mastitis milk in South Korea, 2018-2022

Staphylococcus spp. are one of the most predominant isolates in milk samples of dairy cows with mastitis worldwide. The aims of this study were to investigate the prevalence of bacterial pathogens in bovine mastitis milk samples in South Korea and the antimicrobial resistance profiles of staphylococcal isolates. In total, 1,245 strains were isolated from 1,260 mastitis quarter milk samples (with somatic cell counts ≥ 200,000 cells/mL) from 66 dairy farms between 2018 and 2022. The bacterial genus with the highest prevalence in bovine mastitis milk samples was Staphylococcus spp. (33.9%), followed by Streptococcus spp. (11.5%). S. aureus and non-aureus staphylococci (NAS) accounted for 11.0% and 89.0% of staphylococcal isolates, respectively. S. chromogenes was the most prevalent species among the 22 NAS species detected. S. aureus showed the highest resistance rates to penicillin (25.0%) and ampicillin (20.8%), whereas NAS showed the highest resistance rates to penicillin (18.3%), tetracycline (11.4%) and erythromycin (10.1%). Sixteen multidrug-resistant (MDR) isolates were only isolated from NAS, and the most commonly detected antimicrobial resistance gene in the 16 MDR isolates was mecA (75.0%), followed by tetK (62.5%), blaZ (50.0%), ermC (50.0%), and lnuA (43.8%). In conclusion, NAS were the most common isolates from mastitis milk in South Korea and MDR isolates carried a variety of antibiotic resistance genes. Our study suggests that continuous monitoring of the distribution and antimicrobial resistance in Staphylococcus spp., particularly NAS, is needed to improve the effectiveness of management and treatment strategies in dairy farms.

Incidence, antimicrobial resistance and mortality of Klebsiella pneumoniae bacteraemia in Shanghai, China, 2018-2022

BACKGROUND

Klebsiella pneumoniae (KP) accounts for high antimicrobial resistance and mortality rates of bloodstream infections (BSIs).

OBJECTIVES

To investigate incidence, antimicrobial resistance and risk factors for mortality of KP BSIs in East China.

METHODS

A retrospective study of patients with KP BSIs was conducted in a tertiary care hospital from 2018 to 2022. Medical records of all hospitalised patients with KP BSIs were reviewed and analysed. The incidence, antimicrobial resistance and mortality of KP BSIs were evaluated. The Kaplan-Meier method was used to plot survival curves and logistic regression was used to analyse risk factors for crude 30-day mortality.

RESULTS

A total of 379 inpatients with KP BSIs were enrolled. The incidence of patients with KP BSIs was fluctuating between 4.77 and 9.40 per 100,000 patient-days. The crude 30-day mortality rate of these patients was 26.39%. Of the 379 KPisolates, 197 (51.98%) were carbapenem-resistant (CR) and 252 (66.49%) were multidrug-resistant (MDR). All isolates showed the lowest resistance to tigecycline (13.77%) and polymyxin B (14.61%). Cases with MDR/CR isolates had significantly longer length of hospital stay, higher crude 30-day mortality and medical costs than non-MDR/non-CR isolates. Age, CR phenotype, paracentesis, indwelling central venous catheter (CVC), use of carbapenems, tetracyclines, polymyxins B, and irrational empiric treatment were independently associated with crude 30-day mortality.

CONCLUSION

MDR/CR KP BSIs are associated with increased mortality, healthcare costs and prolonged hospitalisation. Patients with advanced age, CR phenotype, paracentesis, CVC, exposure to some antibiotics, and irrational empirical antibiotic treatment are at higher mortality risk.

A comprehensive evaluation of risk factors for mortality, infection and colonization associated with CRGNB in adult solid organ transplant recipients: a systematic review and meta-analysis

BACKGROUND

The burden of carbapenem-resistant gram-negative bacteria (CRGNB) among solid organ transplant (SOT) recipients has not been systematically explored. Here, we discern the risk factors associated with CRGNB infection and colonization in SOT recipients.

METHODS

This study included observational studies conducted among CRGNB-infected SOT patients, which reported risk factors associated with mortality, infection or colonization. Relevant records will be searched in PubMed, Embase and Web of Science for the period from the time of database construction to 1 March 2023.

RESULTS

A total of 23 studies with 13,511 participants were included, enabling the assessment of 27 potential risk factors. The pooled prevalence of 1-year mortality among SOT recipients with CRGNB was 44.5%. Prolonged mechanical ventilation, combined transplantation, reoperation and pre-transplantation CRGNB colonization are salient contributors to the occurrence of CRGNB infections in SOT recipients. Renal replacement therapy, post-LT CRGNB colonization, pre-LT liver disease and model for end-stage liver disease score increased the risk of infection. Re-transplantation, carbapenem use before transplantation and ureteral stent utilization increaesd risk of CRGNB colonization.

CONCLUSION

Our study demonstrated that SOT recipients with CRGNB infections had a higher mortality risk. Invasive procedure may be the main factor contribute to CRGNB infection.

Imidazolium, pyridinium and pyrazinium based ionic liquids with octyl side chains as potential antibacterial agents against multidrug resistant uropathogenic E. coli

Urinary tract infections (UTIs) are the second most prevalent infectious disease with E. coli being the most common etiological agent behind these infections, affecting more than 150 million people globally each year. In recent decades, the emergence of multi-drug resistant (MDR) pathogens has rapidly escalated. To combat antimicrobial resistance (AMR), it is important to synthesize new biologically effective alternatives like ionic liquids (ILs) to control the bacterial infection and their spread. Ionic liquids are poorly coordinated organic salts characterized by melting points typically below 100 °C. The ability of ILs to form anionic and cationic interactions contributes to their versatile chemical, physical and biological attributes. In the present study, a total of 9 previously chemically synthesized and characterized ILs were used. For exploration of their antibacterial potential against the urinary tract infections (UTIs) caused by MDR Uropathogenic E. coli (UPEC) strains, in vitro and in vivo evaluation of ILs were performed. ILs showed pronounced zone of inhibition (ZOI), minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of 29.5 mm, 3.81 μM and 5.08 μM by agar disk diffusion and broth micro-dilution methods, respectively. Scanning electron microscopy results depicted substantial morphological changes in UPEC biofilm formation ascertaining antibiofilm potential of tested ILs. Moreover, ILs showed exceptional antioxidant potential depicted by DPPH assay along with low cytotoxic effect toward mammalian cell lines (NB4), red blood cells and whole blood. Furthermore, the gene expression analysis results justified the antibacterial potential of ILs showing down-regulation of fimH, uvrY and up-regulation of csrA gene in UPEC after ILs treatment. In vivo dermal sensitivity assessment also established their non-cytotoxic behavior. In silico analysis validated these results, with the majority of the compounds exhibiting moderate to good absorption.Due to remarkable antibacterial and antioxidant potential and negligible cytoxicity, it could be inferred that ILs could serve as novel antimicrobial alternative agents in the treatment of UTIs.

In Vitro Antibacterial Activity, Molecular Docking, and ADMET Analysis of Phytochemicals from Roots of Dovyalis abyssinica

Dovyalis abyssinica is widely used in Ethiopia for treating various human ailments, yet its pharmacological properties and chemical composition remain largely unexplored. The chromatographic separation of D. abyssinica roots extract afforded five compounds, namely tremulacin (1), cochinchiside A (2), 5-methoxydurmillone (3), catechin-7-O-α-L-rhamnopyranoside (4), and stigmasterol (5), confirmed via IR, NMR, and MS spectral data. This is the first report of these compounds from this plant, except for compounds 1 and 5. The extracts and isolated compounds were tested for antibacterial activity against S. aureus, S. epidermidis, E. faecalis, E. coli, K. pneumoniae, and P. aeruginosa strains. Methanol roots extract exhibited significant antibacterial activity (MIC 0.195 mg/mL) against E. coli and P. aeruginosa. Compounds 1 and 3 showed remarkable antibacterial activity, with compound 1 (MIC 0.625 mg/mL) exhibiting antibacterial activity against S. aureus and S. epidermidis, whereas compound 3 (MIC 0.625 mg/mL) exhibited antibacterial activity against S. epidermidis and K. pneumoniae. Molecular docking analysis revealed better binding energies for compound 1 (-8.0, -9.7, and -8.0 kJ/mol) and compound 3 (-9.0, -8.7, and -8.4 kJ/mol), compared to ciprofloxacin (-8.3, -7.5, and -6.7 kJ/mol), in regard to S. aureus pyruvate kinase, S. epidermidis FtsZ, and K. pneumoniae Topoisomerase IV, respectively. ADME analysis also revealed good antibacterial candidacy of these compounds, provided that in vivo analysis is conducted for further confirmation of the results.

Clinical characteristics and mortality risk factors of premature infants with carbapenem-resistant Klebsiella pneumoniae bloodstream infection

Due to the resistance of carbapenem-resistant Klebsiella pneumoniae (CRKP) to most antibiotics, CRKP treatment is challenging, which results a high mortality rate. CRKP infection poses a significant challenge for infection management and treatment, especially among neonates and premature infants. Therefore, it is important to understand the clinical characteristics of CRKP bloodstream infection (BSI) in premature infants and identify the related risk factors for death. This study aims to explore and analyze the clinical characteristics and risk factors affecting mortality of BSI caused by CRKP in premature infants. A retrospective study was conducted in a Children's Hospital in Henan to analyze clinical data of premature infants with CRKP BSI admitted from January 2015 to December 2022. Univariate and multivariate logistic regression models were utilized to investigate risk factors affecting mortality. Receiver operating characteristic curves were employed to evaluate the predictive value of different indicators on mortality, and differences in area under the curve (AUC) were compared using Stata 17 SE. A total of 96 premature infants with CRKP BSI were enrolled, including 70 patients in the survival group and 26 in the death group. At the onset of infection, 69 (71.9%) patients exhibited persistent tachycardia (heart rate > 180 beats/min), 61 (63.5%) had fever, and 59 (61.4%) experienced apnea episodes. Concurrent meningitis (OR 9.588, 95% CI 1.401-57.613, P = 0.021), concurrent necrotizing enterocolitis (NEC) (OR 7.881, 95% CI 1.672-73.842, P = 0.032), and the maximum vasoactive-inotropic score (VIS) value within 48 h of onset (OR 1.467, 95% CI 1.021-1.782, P = 0.001) were identified as independent risk factors for mortality. The univariate analysis showed that ceftazidime-avibactam (CAZ/AVI) treatment and appropriate early antimicrobial treatment were significantly associated with survival (P < 0.05). The combined predictive AUC for mortality in premature infants with CRKP BSI using the maximum VIS value ≥ 52.5 points within 48 h of onset, concurrent NEC, and purulent meningitis was 0.931 (95% CI 0.856-1.000) with a sensitivity of 92% and specificity of 85.7%. CRKP BSI was a significant mortality risk in premature infants. It is crucial to administer proper antimicrobial therapy in order to increase survival rates of the patients. CAZ/AVI has the potential to improve outcomes in this particular population; however, further research is required to evaluate the effectiveness of specific treatment in premature infants.

Genomic characteristics of Vibrio vulnificus strains isolated from clinical and environmental sources

Vibrio vulnificus, a gram-negative pathogenic bacterium, transmitted via undercooked seafood or contaminated seawater, causes septicemia and wound infections. In this study, we analyzed 15 clinical and 11 environmental isolates. In total, 20 sequence types (STs), including eight novel STs, were identified. Antibiotic resistance gene analysis commonly detected the cyclic AMP receptor protein (CRP) in both the clinical and environmental isolates. Interestingly, clinical and environmental isolates were non-susceptible to third-generation cephalosporins, such as ceftazidime and cefotaxime, complicating the treatment of V. vulnificus infection. Multiple antibiotic resistance (MAR) index ranged from 0.1 to 0.5, with clinical isolates showing a higher mean MAR index than the environmental isolates, indicating their broader spectrum of resistance. Notable, no quantitative (124.3 vs. 126.5) and qualitative (adherence, antiphagocytosis, and chemotaxis/motility) differences in virulence factors were observed between the environmental and clinical strains. The molecular characteristics identified in this study provide insights into the virulence of V. vulnificus strains in South Korea, highlighting the need for continuous surveillance of antibiotic resistance in emerging V. vulnificus strains.

Antibiotic and Surgical Treatment of Diabetic Foot Osteomyelitis: The Histopathological Evidence

Background: Osteomyelitis is one of the most frequent infections of the diabetic foot, accounting for 20-70% of foot infections. The treatment of osteomyelitis continues to be debated, and the possibility of performing conservative surgery associated with targeted antibiotic treatment allows for reductions in the amount of bone removed, the resolution of osteomyelitis, and a reduction in the changes in the biomechanics of the foot. The objective of this study was to evaluate the outcomes of osteomyelitis treatment with a combination of antibiotic and surgical procedures based on a histopathological analysis of the infected bone and margins. Materials and Methods: We analyzed 25 diabetic patients with osteomyelitis. We treated each patient with empiric antibiotic treatment, surgical removal of the infected bone, and targeted antibiotic treatment. During the surgical procedure, we collected infected bone samples and margins for microbiological and histopathological analyses. Results: All the patients had type 2 diabetes, with a mean age of 71 ± 10 years. Antibiotic therapy was administered orally for an average duration of 21 ± 9 days, aimed at improving the microbiological outcome. Histological examinations of the resected infected bone revealed the presence of osteomyelitis in 23 (92%) patients. The healthy margin sample, surgically assessed as non-infected, was confirmed negative in 80% of cases. At a follow-up of 18 ± 7 months, we achieved complete healing in twenty patients (80%), with an average healing time of 70 ± 41 days. No recurrence of osteomyelitis was observed. Conclusions: The data from this study demonstrate that the combination of targeted antibiotic therapy and conservative surgical treatment is effective in resolving osteomyelitis without recurrence with a very long follow-up. Histological analyses allowed us to confirm the actual presence of osteomyelitis and demonstrate that clinical differentiation during surgery is effective in identifying a healthy margin.

Unveiling the Dynamics of Antimicrobial Resistance: A Year-Long Surveillance (2023) at the Largest Infectious Disease Profile Hospital in Western Romania

Background/Objectives: Antimicrobial resistance (AMR) is a critical global health threat, leading to increased morbidity, mortality, and healthcare costs. This study aimed to identify the most common bacterial pathogens and their resistance profiles from 2179 positive clinical cultures from inpatients at "Victor Babes" Hospital of Infectious Disease and Pneumoftiziology Timisoara in 2023. Methods: Samples were collected from sputum, bronchial aspiration, hemoculture, urine, wound secretions, catheter samples, and other clinical specimens. Results: Key pathogens identified included Klebsiella pneumoniae, Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Acinetobacter baumannii, with notable resistance patterns, observed K. pneumoniae exhibited high resistance rates, notably 41.41% in Quarter 1, while E. coli showed 35.93% resistance in the same period. S. aureus, particularly MRSA, remained a persistent challenge, with 169 cases recorded over the year. A. baumannii and P. aeruginosa displayed alarming levels of multi-drug resistance, especially in Quarter 3 (88.24% and 22.02%, respectively). Although there was a general decline in resistance rates by Quarter 4, critical pathogens such as S. aureus and K. pneumoniae continued to exhibit significant resistance (81.25% and 21.74%, respectively). Conclusions: The study's findings align with the broader antimicrobial resistance trends observed in Romania, where high resistance rates in K. pneumoniae, E. coli, S. aureus (MRSA), Acinetobacter, and Pseudomonas species have been widely reported, reflecting the country's ongoing struggle with multi-drug-resistant infections. Despite some reductions in resistance rates across quarters, the persistent presence of these resistant strains underscores the critical need for strengthened antimicrobial stewardship, infection control measures, and continuous surveillance to combat the growing threat of AMR in Romania and similar healthcare settings.

Effects of Heat-Killed Probiotic Strains on Biofilm Formation, Transcription of Virulence-Associated Genes, and Prevention of UTIs in Mice

Urinary tract infections (UTIs) pose a substantial healthcare challenge, exacerbated by the biofilm-forming abilities and antibiotic resistance of uropathogens. This study investigated the inhibition of biofilm formation (anti-biofilm) and dispersion of pre-established biofilm properties of 18 heat-killed probiotics and their supernatants against four antibiotic-resistant uropathogens: UPEC, Klebsiella pneumoniae (KP), Methicillin-resistant Escherichia coli (MREC), and Methicillin-resistant Staphylococcus pseudintermedius (MRSP). Supernatants from 14 probiotic strains significantly (P < 0.001) inhibited UPEC biofilm formation, reducing it by 20-80%, and also showed promise in removing existing biofilms by 10-60% (P < 0.001). Eight strains significantly (P < 0.05 to < 0.001) inhibited MREC biofilm formation, with four strains achieving 50-80% dispersion. Seventeen strains of heat-killed probiotics directly inhibited UPEC biofilm formation by 10-60% (P < 0.05 to < 0.001), but were less effective against MREC and MRSP (10-50% reduction; P < 0.05 to < 0.001) and had limited impact on KP (10% reduction; P < 0.05 to < 0.001). Notably, heat-killed probiotic like LGA, LGC, LGD, TP-8, and TP-4 showed the most significant inhibitory and dispersion of biofilm activity. RT-qPCR analysis further revealed these inactivated probiotics downregulated genes associated with pili and biofilm formation (fimA, csgA) and upregulated genes linked to quorum sensing (luxS, qseBC, sdiA). Therefore, these findings suggest that paraprobiotic treatment could inhibit the formation of pili and biofilms and promote biofilm dispersion. In an animal model, mice given paraprobiotic formulations I (16 strains) and II (a specific mixture) for 2 weeks showed reduced urinary bacterial load (P < 0.05). Paraprobiotic I notably reduced morbidity from bacteriuria (> 105 CFU/ml) by 5 to 30% within the first 5 days post-infection compared to placebo. These findings highlight the potential of specific heat-killed probiotics in combating biofilms and preventing UTIs.

Production of Polyvinyl Alcohol/Amoxicillin - Chitosan/Collagen Hybrid Bilayer Membranes for Regeneration of Gingival Tissues

Periodontal diseases, if untreated, can cause gum recession and tooth root exposure, resulting in infection and irreversible damage. Traditional treatments using autologous grafts are painful and often result in postoperative complications. Scaffolds offer a less invasive alternative, promoting cell proliferation and healing without additional surgery, thus enhancing comfort for patients and doctors. This study developed Chitosan (Chit)/Collagen (Col) film surfaces and drug-loaded Polyvinyl Alcohol (PVA)/Amoxicillin (AMX) nanofibers using solvent casting and electrospinning methods, respectively. The surfaces are characterized by scanning electron microscopy (SEM), mechanical testing, Fourier Transform Infrared Spectroscopy (FTIR), and differential scanning calorimetry (DSC). Biocompatibility and antimicrobial properties are assessed using NIH/3T3 fibroblast cells and bacterial cultures. SEM images confirmed the structural integrity of AMX-loaded 13% PVA nanofibers, while FTIR analysis validated the compositional integrity of PVA/AMX nanofibers and Chit/Col film hybrid surfaces. Cell studies showed over 90% viability for Chit/Col film + PVA/AMX nanofiber hybrid bilayer membranes, confirming their biocompatibility. The antimicrobial assessment indicated that the Chit/Col film + PVA/AMX (0.2%) nanofiber hybrid bilayer membrane exhibited superior efficacy against Streptococcus mutans. These findings suggest that this hybrid bilayer membrane can enhance cell growth, promote proliferation, and enable controlled drug release, offering significant promise for regeneration of gingival tissues.

Relative fitness of wild-type and phage-resistant pyomelanogenic P. aeruginosa and effects of combinatorial therapy on resistant formation

Bacteriophages, the natural predators of bacteria, are incredibly potent candidates to counteract antimicrobial resistance (AMR). However, the rapid development of phage-resistant mutants challenges the potential of phage therapy. Understanding the mechanisms of bacterial adaptations to phage predation is crucial for phage-based prognostic applications. Phage cocktails and combinatorial therapy, using optimized dosage patterns of antibiotics, can negate the development of phage-resistant mutations and prolong therapeutic efficacy. In this study, we describe the characterization of a novel bacteriophage and the physiology of phage-resistant mutant developed during infection. M12PA is a P. aeruginosa-infecting bacteriophage with Myoviridae morphology. We observed that prolonged exposure of P. aeruginosa to M12PA resulted in the selection of phage-resistant mutants. Among the resistant mutants, pyomelanin-producing mutants, named PA-M, were developed at a frequency of 1 in 16. Compared to the wild-type, we show that PA-M mutant is severely defective in virulence properties, with altered motility, biofilm formation, growth rate, and antibiotic resistance profile. The PA-M mutant exhibited reduced pathogenesis in an allantoic-infected chick embryo model system compared to the wild-type. Finally, we provide evidence that combinatory therapy, combining M12PA with antibiotics or other phages, significantly delayed the emergence of resistant mutants. In conclusion, our study highlights the potential of combinatory phage therapy to delay the development of phage-resistant mutants and enhance the efficacy of phage-based treatments against P. aeruginosa.

Phytogenic Synthesis of Cuprous and Cupric Oxide Nanoparticles Using Black jack Leaf Extract: Antibacterial Effects and Their Computational Docking Insights

Background: Green synthesized nanoparticles (NPs) have gained increasing popularity in recent times due to their broad spectrum of antimicrobial properties. This study aimed to develop a phytofabrication approach for producing cuprous (Cu2O) and cupric oxide (CuO) NPs using a simple, non-hazardous process and to examine their antimicrobial properties. Methods: The synthesis employed Bidens pilosa plant extract as a natural reducing and stabilizing agent, alongside copper chloride dihydrate as the precursor. The biosynthesized NPs were characterized through various techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier-transform infrared (FT-IR) spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). Results: XRD analysis confirmed that the synthesized CuO and Cu2O NPs exhibited a high degree of crystallinity, with crystal structures corresponding to monoclinic and face-centered cubic systems. SEM images revealed that the NPs displayed distinct spherical and sponge-like morphologies. EDS analysis further validated the purity of the synthesized CuO NPs. The antimicrobial activity of the CuO and Cu2O NPs was tested against various pathogenic bacterial strains, including Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Bacillus cereus, with the minimum inhibitory concentration (MIC) used to gauge their effectiveness. Conclusions: The results showed that the phytosynthesized NPs had promising antibacterial properties, particularly the Cu2O NPs, which, with a larger crystal size of 68.19 nm, demonstrated significant inhibitory effects across all tested bacterial species. These findings suggest the potential of CuO and Cu2O NPs as effective antimicrobial agents produced via green synthesis.

Changes in the epidemiology of neonatal bacteremia during the COVID-19 pandemic in Wuhan, China

OBJECTIVE

To investigate the incidence, pathogen distribution, and antibiotic susceptibility of early- and late-onset neonatal bacteremia, and to analyze pathogen trends before and during the COVID-19 pandemic.

METHODS

Between January 2016 to December 2022, we collected 879 blood and cerebrospinal fluid specimens from newborns with bacteremia. Bacterial identification used biochemical methods and MALDI-TOF, and antibiotic susceptibility was tested with the VITEK 2 system. Incidence per 1,000 admissions was calculated with Wilson's 95% confidence intervals, and categorical variables were compared using χ²-test or Fisher's exact test.

RESULTS

Early-onset bacteremia incidence was 2.6 per 1,000 admissions, and late-onset bacteremia was 26.3, with a significant decline from 70.7 to 10.5 per 1,000 admissions over the study period. Late-onset bacteremia was more common before COVID-19, while early-onset bacteremia increased during the pandemic. The top five pathogens were CoNS(39.9%), E. faecalis(17.7%), E. faecium(13.7%), E. coli(8.4%), and GBS(5.8%). During the COVID-19 pandemic, the incidence of CoNS and S. aureus infections significantly decreased. Throughout the entire study period, CoNS and S. aureus showed high resistance to penicillin G and erythromycin but were sensitive to vancomycin and linezolid. E. faecalis and E. faecium were susceptible to vancomycin, linezolid, and teicoplanin but resistant to erythromycin, tetracycline, and rifampin. MRCoNS and MRSA were detected in 72.7% and 31.0% of isolates, respectively. Resistance rates of E. faecium and E. faecalis to ampicillin decreased significantly, clindamycin resistance in GBS decreased during the pandemic.

CONCLUSION

This study highlights notable shifts in neonatal bacteraemia patterns during the COVID-19 Pandemic that were likely influenced by increased infection control and disruptions in maternal care, leading to changes in pathogen distribution and antimicrobial resistance.

Synthetic indole derivatives as an antibacterial agent inhibiting respiratory metabolism of multidrug-resistant gram-positive bacteria

The survival of modern medicine depends heavily on the effective prevention and treatment of bacterial infections, are threatened by antibacterial resistance. The increasing use of antibiotics and lack of stewardship have led to an increase in antibiotic-resistant pathogens, so the growing issue of resistance can be resolved by emphasizing chemically synthesized antibiotics. This study discovered SMJ-2, a synthetic indole derivative, is effective against all multidrug-resistant gram-positive bacteria. SMJ-2 has multiple targets of action, but the primary mechanism inhibits respiratory metabolism and membrane potential disruption. SMJ-2 was discovered to interfere with the mevalonate pathway, ultimately preventing the synthesis of farnesyl diphosphate, a precursor to the antioxidant staphyloxanthin, eventually releasing reactive oxygen species, and leading phagocytic cells to destroy pathogens. Additionally, no discernible biochemical and histopathological alterations were found in the mouse acute toxicity model. This study emphasizes mechanistic insights into SMJ-2 as a potential antibacterial with an unusual method of action.

Randomized Clinical Trials Demonstrate the Safety Assessment of Alkalihalobacillus clausii AO1125 for Use as a Probiotic in Humans

(1) Background: Alkalihalobacillus clausii AO1125 is a Gram-positive, motile, spore-forming bacterium with potential as a probiotic due to its broad-spectrum antimicrobial activity, inhibiting pathogens like Listeria monocytogenes, Staphylococcus aureus, and Clostridium difficile, as well as anti-rotavirus activity. Its resilience in gastrointestinal conditions suggests benefits for gut health. This study evaluates the safety and probiotic potential of A. clausii AO1125. (2) Methods: Genome annotation identified genes linked to probiotic traits such as stress resistance, gut colonization, immune modulation, and antimicrobial production. The genome was screened for antibiotic resistance genes using CARD, bacteriocin clusters using BAGEL4, and virulence factors via VFDB. Cytotoxicity was assessed on Vero cells and erythrocytes, and a Phase I, double-blind, placebo-controlled clinical trial was conducted with 99 healthy volunteers (50 AO1125, 49 placebo). (3) Results: Genomic analysis confirmed minimal antibiotic resistance genes and the absence of virulence factors, supporting safety. A. clausii AO1125 showed no pathogenicity, cytotoxicity, or hemolytic activity and was well-tolerated in clinical settings, with mild, transient abdominal gas as the most common adverse event. (4) Conclusions: The safety profile and genetic basis for probiotic and antimicrobial properties support A. clausii AO1125 as a promising probiotic candidate for gastrointestinal health, warranting further clinical research.

Coexistence of the blaZ gene and selected virulence determinants in multidrug-resistant Staphylococcus aureus: insights from three Nigerian tertiary hospitals

BACKGROUND AND PURPOSE

Infections caused by β-lactamase-producing strains of Staphylococcus aureus have become increasingly difficult to treat due to the expression of multiple virulence factors. This has heightened concerns about managing S. aureus-related infections. This study was conducted to characterize the blaZ gene and selected virulence determinants in β-lactam resistant S. aureus from human sources in three Nigerian tertiary hospitals.

MATERIALS AND METHODS

Three hundred and sixty samples were collected for the study. S. aureus was isolated and characterized following standard microbiological protocols and nuc gene amplification. Antibiotic susceptibility and minimum inhibitory concentration tests were performed using the disk diffusion method and E-tests, respectively. Biofilm formation and β-lactamase production were assessed using Congo red agar and nitrocefin kits, while the blaZ gene was examined using conventional PCR. Capsular polysaccharide genotyping, accessory gene regulator (agr) detection, Panton-valentine leucocidin (PVL), and PVL proteins were performed using PCR and Western blotting.

RESULTS

S. aureus was recovered from 145 samples, 50 (34.5%) of these isolates exhibited multidrug resistance, with MICs ranging from 0.125 to 1.00 µg/mL, and showed significant resistance to aminoglycosides, fluoroquinolones, and β-lactams. Of these, 31 strains produced β-lactamases, 30 of which carried the blaZ gene in combination with cap8 (80%) or cap5 (20%). Biofilm formation and PVL gene were observed in 85% of the 20 randomly selected blaZ-positive multidrug-resistant (MDR) strains. The agr2 allele was predominant, found in 70% of the selected MDR strains. No significant difference in the occurrence of the blaZ gene was found among the three clinical sources (p ≤ α0.05).

CONCLUSION

The co-occurrence of the blaZ gene with PVL, capsular polysaccharide genes, and agr alleles is associated with biofilm formation, indicating a high risk of β-lactam-resistant S. aureus infections. Our findings highlight the need for continuous molecular surveillance to enhance infection management, treatment options, and patient outcomes in the study locality. A limitation of this study is the random selection of MDR isolates, which may affect the comprehensiveness of the analyses.

Characterization of a Novel Sequence Type (ST) 6758 Klebsiella Pneumoniae and the Role of IncX3 Plasmid in the Transmission of bla NDM

Purpose

Carbapenem-resistant Klebsiella pneumoniae (CRKP) has emerged as a significant public health threat, particularly as a superbug responsible for nosocomial infections. In this study, we report a novel sequence type 6758 of K. pneumoniae harboring the bla NDM-1 gene.

Material and Methods

Antimicrobial susceptibility testing was conducted according to the guidelines of the Clinical and Laboratory Standards Institute (CLSI). The complete genome sequence of the strain was determined using the Illumina NovaSeq 6000 platform and long-read MinION sequencer. Genomic features and resistance mechanisms of the strain were further comprehensively analysed using various bioinformatics approaches.

Results

Antimicrobial susceptibility testing revealed that this strain exhibited resistance to multiple antimicrobials, including ceftazidime, ceftriaxone, cefazolin, cefepime, imipenem, meropenem, ampicillin/sulbactam, and sulfamethoxazole/trimethoprim. The genome analysis identified sixteen resistance genes. The bla NDM-1 carbapenemase gene is located on a 47,823 bp IncX3-type plasmid (pNDM-CRKP331). A total of 41 K. pneumoniae strains carrying similar IncX3-type plasmids were retrieved from the NCBI database, representing 20 sequence types (STs) across 11 countries. The most common resistance gene carried by these IncX3-type plasmids is bla NDM, and all these plasmids contain only the bla NDM gene. The bla NDM-carrying IncX3-type plasmids are widely prevalent in K. pneumoniae in China, spanning 15 STs.

Conclusion

In summary, our study reports the first genome sequence of an ST 6758 K. pneumoniae strain containing the class B β-lactamase bla NDM-1 isolated from a clinical sample. Given the global emergence of bla NDM, measures should be taken to prevent the spread of these bla NDM-carrying IncX3-type plasmids. Our findings contribute to the understanding of the transmission mechanisms of bla NDM in K. pneumoniae.

First documentation of a clinical multidrug-resistant Enterobacter chuandaensis ST2493 isolate co-harboring blaNDM-1 and two blaKPC-2 bearing plasmids

The increasing prevalence of carbapenem-resistant Enterobacter cloacae complex (CREC) poses great challenges to infection treatment in the clinical setting. In this study, we reported the emergence of carbapenemase in a rare species, Enterobacter chuandaensis, belonging to the Enterobacter cloacae complex (ECC). We elucidated the genetic characteristics of carbapenem-resistant isolate FAHZZU5885, co-harboring blaNDM-1 and blaKPC-2. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and average nucleotide identity (ANI) analysis were used to identify E. chuandaensis. S1 nuclease pulsed-field gel electrophoresis (S1-PFGE) and Southern blotting were used to clarify the number and size of the plasmids in FAHZZU5885. Antimicrobial phenotypes were identified by antimicrobial susceptibility testing (AST), and the characteristics of the strain were examined with whole-genome sequencing (WGS). The conjugation experiment and stability assay were conducted to verify the transferability and stability of the plasmid carrying carbapenemase-encoding genes. E. chuandaensis FAHZZU5885 was isolated from a perianal swab of a patient admitted to the ICU. This strain simultaneously carried blaNDM-1 and two blaKPC-2 genes. FAHZZU5885 was resistant to most of the tested antibiotics except for amikacin, tigecycline, and colistin. Two blaKPC-2 were located separately on two different plasmids, the ~ 120 kb IncFIA-IncFII plasmid and the ~ 80 kb IncR plasmid. Both plasmids shared the conserved sequence klcA-korC-ISkpn6-blaKPC-2-ISkpn27-tnpR-tnpA. The blaNDM-1-bearing plasmid had the potential to transfer and can remain stable after successive passages. In addition, the blaNDM-1 was carried on a ~ 80 kb IncFII plasmid with the conserved sequence ISAba125-blaNDM-1-ble-trpF-dsbD-cutA-groS-groL. In summary, this study marks the first report of the multidrug-resistant E. chuandaensis strain FAHZZU5885 harboring two blaKPC-2-bearing plasmids, indicating the potential for the further dissemination of carbapenemase-encoding genes in novel species. The findings contribute to enhancing our understanding of CREC strains, emphasizing the need for continued and comprehensive surveillance of this species.

Pulsed electric field at resonance frequency combat Klebsiella pneumonia biofilms

Healtcare-associated infections have increased due to the development of antimicrobial resistance (AMR) of Gram-negative pathogens (GNPs) and the development of outbreacks over the past two decades. In this work, we investigated how exposure to positive electric pulses affects the growth characteristics of Klebsiella pneumonia (K. pneumonia), a common cause of pneumonia. We explored the impact of varying exposure frequencies (0.2-2 Hz) and time (15-90 min, at resonance frequency) on bioelectric signals produced during cell division, biofilm formation, and bacterial antibiotic susceptibility. Our research found that an extremely low-frequency pulsed electric field (ELF-PEF) significantly inhibited K. pneumonia growth. Specifically, exposure to 0.8 Hz for one hour increased the antibiotic susceptibility of K. pneumonia to inhibitors of cell wall formation, proteins, β-lactamase, DNA, and other substances. We also noticed a notable decrease in K. pneumonia biofilm development exposed to ELF-PEF. Our results suggest that the interaction of K. pneumonia cells with ELF-PEF at the specified frequency and time alters cellular activity and bacterial structure. This technique may be used in the future to treat K. pneumonia infections both in vitro and in vivo.

Mobile genetic elements contributing to horizontal gene transfer of blaNDM among Escherichia coli in the community setting

OBJECTIVE

To investigate the distribution of carbapenem-resistant Enterobacterales (CRE) in the community and to describe the genomic characteristics.

METHODS

CRE screened from fecal samples in healthy people at the health examination center of a tertiary hospital in China underwent Whole genome sequencing (WGS) to analyze genotypic characteristics of CRE. The flanking DNA sequence of blaNDM-5 and mcr1.1 genes were analyzed by Gcluster software.

RESULTS

A total of 7187 fecal samples were screened, and CRE carriage was detected in 0.4 % of the sampled population. In total, 30 Escherichia coli, one Citrobacter freundii and one Klebsiella aerogene were screened. The 30 carbapenem-resistant Escherichia coli (CREC) isolates displayed slight resistance to amikacin (13.3 %) and aztreonam (20.0 %). All the CRE isolates contained blaNDM, and blaNDM-5 (84.4 %) was the most common one. B1 (n = 11) and A (n = 7) were predominant phylogroups. Furthermore, 34 distinct plasmid replicons, 67 different VFs, 22 distinct STs, 17 different FimH types, 26 O:H serotypes as well as 74 MGEs including 61 insertion sequences and 13 transposons were identified. The flanking DNA sequence analysis of blaNDM-5 and mcr1.1 genes indicates the key role of horizontal transfer of blaNDM-5 in the CRE development evidenced by diverse STs and phylogenetic tree.

CONCLUSION

E. coli was the most predominant CRE isolates in community setting, and blaNDM (blaNDM-5) was the main CHβL encoding genes. The high prevalence of ARGs was associated with high resistance to commonly used antimicrobials. Besides, the genetic diversity of these isolates suggested the key role of blaNDM horizontal transfer in the CRE development. Thus, active screening of blaNDM in communities is particularly important for the prevention and control of CRE.

Shifting Trends of Antimicrobial Resistance Patterns Among Uropathogenic Bacteria Before and During the COVID-19 Pandemic

Urinary tract infections (UTIs) represent a significant global health concern, primarily caused by uropathogenic bacteria and their rising trend of antimicrobial resistance (AMR). This study investigates the prevalence and pattern of AMR among uropathogenic bacteria during the COVID-19 pandemic, highlighting its impact on antimicrobial usage and resistance trends. This retrospective cross-sectional study, conducted at King Fahad Medical City, Riyadh, Saudi Arabia, from January 1, 2018, to December 31, 2022, analyzed 10,031 patients with positive urine cultures for resistance patterns pre-COVID-19 and during COVID-19. Bacterial identification and antimicrobial susceptibility testing were performed using the BD Phoenix system according to Clinical Laboratory Standard Institute guidelines. This study recorded an overall decrease in AMR during the pandemic among the most prevalent uropathogens (Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa); however, notable increases in AMR were observed for specific antibiotics like cefoxitin, imipenem, and colistin. resistance. The multidrug resistance (MDR) among P. aeruginosa strains significantly decreased from 22.9% pre-pandemic to 9.2% during the pandemic. The decline in AMR patterns during the COVID-19 pandemic likely resulted from altered antibiotic usage and healthcare practices, emphasizing the importance of ongoing monitoring and targeted antimicrobial management in response to changing AMR dynamics during global health emergencies.

Antibacterial gelatin/tragacanth gum films containing galbanum essential oil for in vitro scratch-healing

Natural substances and bioactive agents possess great potential in wound care based on their ability to promote healing and prevent infection. This study focused on the fabrication of antibacterial wound dressings by combining gelatin (G), tragacanth gum (TG), and galbanum essential oil (GEO) as a loaded drug. TG addition resulted in more elastic and flexible films besides enabling encapsulation of the hydrophobic GEO into the biopolymeric matrix. GEO was utilized as an antibacterial and a wound-healing enhancer for open wounds such as incisions. Field emission scanning electron microscopy (FE-SEM) analysis revealed a porous film structure after GEO incorporation. Higher GEO concentration caused reduced swelling and slower degradation. Water vapor transfer rate varied from 596 to 894 g/m2.day, making the films suitable for wound dressings. GEO release exhibited a two-phase profile with prolonged diffusion-controlled release for a higher content of GEO. The films demonstrated dose-dependent antimicrobial activity against S. aureus and E. coli strains. Effectiveness and noteworthy application of this research were approved by scratch assay on human dermal fibroblast cells, and films with 3 % GEO showed 79.42 % wound closure, which is significantly higher than the control sample (55.15 %), indicating promoted cell migration and promising wound healing properties.

First-Genome Sequence Data of an Alcaligenes nematophilus Strain EBU-23 Encoding bla Gene Implicated in Acute Childhood Gastroenteritis

Although an environmental contaminant, Alcaligenes sp. are now increasingly reported in clinical infections. Here, we present a whole-genome sequence of an extended spectrum beta-lactamase (ESBL) Alcaligenes nematophilus strain EBU-23 encoding beta-lactamase, bla gene, isolated from the stool of a hospitalized infant with acute gastroenteritis in a tertiary hospital in Nigeria. Antibiotics susceptibility test revealed that the isolate was resistant to the β-lactams, cephalosporins, and penicillin, β-lactam combination, and the fluoroquinolones. Genomic analysis exposed the presence of a class A beta-lactam hydrolase gene and multiple multidrug efflux permease which may be responsible for the beta-lactamase and multidrug resistance observed with the isolate. To the best our knowledge, we describe the first whole-genome sequence of a multidrug-resistant A. nematophilus implicated in acute childhood gastroenteritis in Nigeria.

Whole-genome sequencing-based analysis of Brucella species isolated from ruminants in various regions of Türki̇ye

BACKGROUND

Brucellosis, a zoonotic disease in Türkiye, which has significant direct and indirect impacts on the healthcare system and livestock. This study, which aimed to investigate the differences among Brucella spp. isolates originating from different regions of Türkiye, for implications for public health and veterinary medicine.

METHOD

Twenty-one isolates from ruminants and two isolates from humans obtained from various regions of Türkiye were utilized in the study. The isolates were identified and biotyped using traditional microbiological procedures, and whole-genome sequencing (WGS) was performed. This was followed by single nucleotide polymorphism (SNP)--based phylogenetic analysis and WGS-based analysis of virulence and resistance genes. Additionally, phenotypic antimicrobial resistance and phage susceptibilities were determined. The obtained data were then compared for concordance, ensuring the validity and reliability of the results.

RESULTS

Our study, employing culture methods, polymerase chain reaction (PCR), and WGS analyses, identified 11 Brucella melitensis (bv 3 (n = 9), one each bv 1 and bv 2) and 12 B. abortus (bv 3 (n = 11), bv 9 (n = 1)) isolates All B. abortus isolates were of bovine origin, while the B. melitensis isolates were from sheep (n = 7), goat (n = 1), ram (n = 1), and humans (n = 2). In the whole-genome SNP-based phylogenetic tree, all B. melitensis strains were found to be of the IIb subtype of genotype II associated with the Eastern Mediterranean lineage. Ten different genotypes were identified in the SNP analysis of the isolates, with a maximum SNP difference of 278 and a minimum SNP difference of 4 among these genotypes. According to the WGS-SNP-based phylogenetic tree of B. abortus isolates, they were grouped in clade C1. In the SNP analysis, where ten different genotypes were identified, the SNP difference among these genotypes was a maximum of 316 and a minimum of 6. In the in silico MLST analysis performed with WGS data, B. melitensis isolates were identified as ST8 and ST102 genotypes, while B. abortus isolates were identified as ST2 and ST3 genotypes. The dominant genotypes were ST8 for B. melitensis and ST2 for B. abortus, respectively. Virulence gene analysis conducted based on WGS data of the 23 B. abortus and B. melitensis isolates revealed 43 virulence gene-associated regions in all strains, irrespective of species, host, or isolation year. Although classical resistance-related genes were not detected by WGS-based antimicrobial resistance gene analysis, phenotypic resistance analysis revealed resistance to azithromycin, rifampin, and trimethoprim/sulfamethoxazole in B. abortus and B. melitensis isolates.

CONCLUSION

Both B. melitensis and B. abortus were circulating species in animals and human. The dominant genotypes were ST8 for B. melitensis and ST2 for B. abortus, respectively. All B. melitensis strains were found to be of the IIb subtype of genotype II associated with the Eastern Mediterranean lineage, while B. abortus isolates, they were grouped in clade C1. Further, a comprehensive study with a sufficient number of isolates covering all regions of Türkiye would provide more accurate information about the current epidemiological situation in the country.

A silver lining in MRSA treatment: The synergistic action of poloxamer-stabilized silver nanoparticles and methicillin against antimicrobial resistance

BACKGROUND

Increasing antibiotic resistance in bacterial infections, including drug-resistant strains like methicillin-resistant Staphylococcus aureus (MRSA), necessitates innovative therapeutic solutions. Silver nanoparticles are promising for combating infections, but toxicity concerns emphasize the importance of factors like dosage, size, shape, and surface chemistry. Hence, exploring poloxamer as a stabilizing agent to reduce its toxicity and enhance the antibacterial effect on MRSA is investigated.

METHODS

Silver nanoparticles stabilized with poloxamer (AgNPs@Pol) were synthesized through the chemical reduction method and characterized using UV-visible spectrophotometer, HR-TEM, DLS, and Zeta potential measurements. Subsequently, the antibacterial activity of AgNPs@Pol alone and in combination with methicillin against MRSA and methicillin-susceptible S. aureus (MSSA) was evaluated using the broth microdilution method.

RESULTS

AgNPs@Pol showed significant efficacy against MRSA and MSSA, achieving a 100 % reduction in colony-forming units (CFU) at 9.7 μg/ml. The minimum inhibitory concentration (MIC) against MRSA and MSSA was 8.6 μg/ml and 4.3 μg/ml, respectively. A synergistic effect was observed when AgNPs@Pol was combined with methicillin. Treatment with AgNPs@Pol increased reactive oxygen species (ROS) production in both strains, contributing to its antibacterial activity. Real-time qPCR analysis indicated the downregulation of genes involved in antimicrobial resistance and cell adhesion in both strains. Further, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay demonstrated low cytotoxicity for AgNPs@Pol against MCF-7, MG-63, and NIH-3T3 cell lines.

CONCLUSION

The developed AgNPs@Pol demonstrated extensive colloidal stability, potent antibacterial activity and synergistic effect with methicillin against MRSA and MSSA. Further studies in primary cells and in vivo models may validate its potential for clinical applications.