Search Results (866)

Streptococcus dysgalactiae subsp. equisimilis (SDSE) is an emerging cause of invasive disease, yet contemporary genomic data from Canada remain scarce. We investigated 56 cases of invasive SDSE infection identified between 2018 and 2022 in two major tertiary care teaching hospitals in Toronto, Ontario, and characterized 49 corresponding isolates by whole-genome sequencing. Nearly three-quarters of infections were caused by the globally expanding ST20 emm type stG62647 lineage. Patients infected with this lineage were significantly older than those infected with non-ST20 lineages across both bloodstream and non-blood infections. Core-genome phylogenetic analysis revealed a highly clonal ST20 cluster, although two isolates had divergent emm types suggesting recombination at the emm locus. Non-ST20 lineages were numerically smaller and genetically more heterogeneous, including distinct sublineages within ST3 and ST34. All isolates were susceptible to β-lactams and vancomycin. Resistance to tetracycline, erythromycin, and clindamycin was detected in a subset of isolates and was associated with genes tetM, tetO, ermA, ermB, and msrD. Several antimicrobial resistance determinants were located on mobile genetic elements, including integrative and conjugative elements. Our findings provide a contemporary genomic view of invasive SDSE in Toronto, highlighting the dominance of the ST20 stG62647 lineage in agreement with recent global observations. Full article

Robust genetic tools are a prerequisite for causal, perturbation-based tests of redox physiology in acetogens. Here we establish practical genetic entry points for Sporomusa sphaeroides DSM 2875 under strictly anaerobic handling. We first attempted genome editing via double-crossover allelic exchange targeting pyrF using a non-replicative pUC19-based knockout construct and 5-fluoroorotic acid counterselection. Diagnostic PCR identified ΔpyrF candidates with the expected size shifts, demonstrating that homologous recombination is technically feasible in DSM 2875; however, the ΔpyrF genotype exhibited severe growth defects and could not be stably maintained over repeated passages, indicating a key limitation of a pyrF-based workflow under our current conditions. We then evaluated multiple E. coli–anaerobe shuttle plasmids for introduction and maintenance. Among the tested vectors, pJIR751 reproducibly yielded erythromycin-resistant transformants after prolonged incubation and supported serial passaging on selective media. Plasmid retention was confirmed by diagnostic PCR from liquid cultures in all tested isolates. Importantly, this maintainable plasmid platform enables genetically grounded perturbation-and-rescue experiments under electrode- or Fe⁰-assisted conditions, allowing mechanistic hypotheses in bioelectrochemical acetogenesis to be tested causally rather than inferred from phenotypes alone. Together, these results define current practical boundaries for S. sphaeroides genetics and establish pJIR751 as a practical foundation for downstream genetic manipulation in bioelectrochemical studies. Full article

The widespread occurrence of macrolide antibiotics (MLs) in aquatic environments poses potential ecological risks; however, the interactive effects of MLs, especially combined MLs on microalgae and their removal mechanisms, remain poorly understood. This study investigated the removal efficiency, physiological–biochemical responses, and molecular mechanisms of Chlorella pyrenoidosa under single and combined exposure to erythromycin (ERY) and roxithromycin (ROX) over 14 days. The results demonstrated that antibiotic removal efficiency was concentration-dependent and higher in low-concentration treatment. The removal rates of ERY (0.15 mg/L) and ROX (0.02 mg/L) reached 100% and 66.86%, respectively. Notably, in the combined low-concentration group, the presence of ROX promoted the degradation of ERY, with the removal being 11.06–14.77% higher than in single treatment. Conversely, in high-concentration combined treatments (1.63 mg/L ERY + 0.5 mg/L ROX), the removal of ERY was inhibited and the removal of ROX was comparable with the corresponding single treatment. High-concentration treatment groups and combined-treatment groups significantly inhibited microalgae growth and total chlorophyll content, modified the chlorophyll composition, and induced severe oxidative stress. Correlation analysis revealed that antibiotic removal was positively correlated with cell density, chlorophyll content, CAT, CYP450, and GST activities while negatively correlated with SOD, ROS, and MDA. Transcriptomic analysis revealed significant disruption of xenobiotic metabolism pathways, photosynthesis-related processes, and DNA replication/mismatch repair pathways. Key genes involved in stress signaling (e.g., MKK3, MPK3), detoxification (e.g., CYP97, GSTP), and photosynthesis (e.g., HemL) were differentially regulated, providing molecular evidence for the observed physiological responses and removal behaviors. These findings provide valuable insights for the ecological risk assessment of antibiotic mixtures and the development of microalgae-based wastewater treatment technologies. Full article

Mycoplasma pneumoniae is a significant pathogen responsible for community-acquired respiratory infections in children and adolescents, with the rising prevalence of macrolide-resistant M. pneumoniae (MRMP), particularly in Asia, presenting critical treatment challenges. Our previous study inferred that a macrolide efflux pump may contribute to macrolide resistance in M. pneumoniae in addition to the common point mutations in 23S rRNA gene. This study aimed to define the specific pump and confirm its role. Through comparative genomic analysis, we identified a candidate gene, MPN_080, encoding an ABC transporter permease, which was further characterized using phylogenetic analysis, AlphaFold-based structural modeling, and biochemical assays. Overexpression of MPN_080 from an erythromycin-resistant isolate in the erythromycin-sensitive M129 resulted in a significant increase in minimum inhibitory concentrations (MICs) from <0.125 µg/mL to 1 µg/mL, while similar overexpression of MPN_080 derived from M129 did not affect MICs. Notably, this resistance mechanism operates independently of M. pneumoniae virulence factors, as evidenced by unaltered colonization capacity in NCI-H292 cells and consistent immune response patterns across both strains. Our findings establish MPN_080 as a novel determinant of macrolide resistance functioning associated with enhanced ATPase activity. These insights into non-classical resistance mechanisms may guide future diagnostic and therapeutic strategies against MRMP. Full article

Background/Objectives: Methicillin-resistant Staphylococcus aureus (MRSA) causes hospital- and community-acquired infections. MRSA is a highly diverse strain that includes several epidemic clones, including CC45. A previous study conducted among MRSA isolates in Kuwait identified CC45 in two isolates in the early 2000s. This study provides an update on the prevalence and molecular characteristics of CC45 among MRSA isolates in Kuwait hospitals, during 2016–2022. Methods: A total of 13,276 MRSA isolates were collected during 2016–2022 and typed using antibiogram, DNA microarray, Staphylococcal protein A (spa) typing, pulsed-field gel electrophoresis (PFGE), and multi-locus sequence typing (MLST). Results: CC45 was detected in 87 (0.65%) of the 13,276 MRSA isolates. The isolates were resistant to fusidic acid (n = 71), erythromycin (n = 16), and inducible clindamycin resistance (n = 15). Twenty-one isolates were resistant to multiple antibiotics. Spa typing identified 19 types, with t362 (n = 35) and t132 (n = 27) as the dominant types. DNA microarray identified seven genotypes with CC45-MRSA-[IV + fus] (n = 36) and CC45-MRSA-[VI + fus] (n = 30) as the dominant types. MLST identified six sequence types (STs): ST7119, ST508, ST45, ST46, ST9548, and ST10699. PFGE clustered the isolates into two major types, A and B, with type A being the major type (n = 83), mostly consisting of CC45-MRSA-[IV + fus] isolates. The CC45-MRSA-[IV + fus] and CC45-MRSA-[VI + fus] genotypes were detected throughout the study period (2016–2022), whereas the other genotypes were detected less frequently. Conclusions: The CC45-MRSA circulating in Kuwait hospitals comprises genetically diverse isolates that may have originated from different sources. The emergence of multidrug resistance among the isolates poses challenges for therapy and infection prevention. Full article

Background: Inducible macrolide–lincosamide–streptogramin B (iMLSB) resistance is well defined in Gram-positive aerobes but remains poorly characterized in anaerobes, where standardized detection strategies are lacking. Following withdrawal of EUCAST guidance to infer clindamycin resistance from erythromycin resistance in Peptostreptococcus and Bacteroides spp. because of inconsistent species-specific performance, a diagnostic gap persists. Methods: We therefore assessed the accuracy of the D-test for detecting iMLSB resistance in anaerobes by correlating phenotypic results with whole-genome sequencing data. Fifty clinical anaerobic isolates, including Finegoldia magna, Peptostreptococcus anaerobius, and Bacteroides spp., were included in the analysis. Antimicrobial susceptibility testing was performed using gradient diffusion to determine minimum inhibitory concentrations of erythromycin and clindamycin, complemented by D-test analysis for phenotypic detection of inducible resistance. Whole-genome sequencing was undertaken to identify erm genes encoding ribosomal methyltransferases associated with the iMLSB phenotype. Results: Among the 50 isolates, erm genes were detected in 16 strains (32.0%). The prevalence of erm positivity was highest among Gram-positive cocci (50%), followed by Gram-positive rods (35.3%) and Gram-negative rods (11.8%). Five erm-positive isolates exhibited a characteristic D-shaped growth pattern, with high erythromycin MICs (>256 mg/L) and low clindamycin MICs (≤2 mg/L), consistent with an inducible iMLSB phenotype, whereas the remaining eleven demonstrated constitutive resistance. Conclusions: The D-test accurately identified inducible iMLSB resistance among Gram-positive anaerobic cocci and, if confirmed in larger studies, could form the basis of an accessible and pragmatic screening strategy for this subgroup. Integration of molecular analyses seems essential for the evidence-based refinement of diagnostic algorithms, particularly in the absence of robust, species-specific guidance. Full article

Hafnia alvei, which belongs to the Enterobacteriaceae family, has been occasionally documented in animal infections but is still not well characterized in the context of bovine mastitis. This research examined the prevalence and antimicrobial resistance characteristics of H. alvei in dairy cows suffering from subclinical mastitis in South Africa’s Free State Province. In the Thabo Mofutsanyana District, a total of 174 milk samples were obtained from cows on six different dairy farms. The California Mastitis Test (CMT) was used to screen for subclinical mastitis, and somatic cell count was used to confirm it. Standard culture methods were used for bacterial isolation, and presumptive Enterobacteriaceae isolates were identified through matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Out of the 174 samples, 84 (48.2%) tested positive for CMT, and 68 (39.1%) met the SCC criteria for subclinical mastitis at a cow level, while 96/336 (28.5%) were infected at a quarter level. Of the 100 presumptive Enterobacteriaceae isolates, 33 (33.0%) were identified as H. alvei (p = 0.0034). Antimicrobial susceptibility testing showed that 50% of the isolates were resistant to penicillin, followed by tetracycline and erythromycin with 25% and 10%, respectively. Furthermore, the results showed that 17 (51.5%) isolates exhibited multidrug-resistant profiles. The results suggest that H. alvei could be a contaminant in raw milk associated with bovine subclinical mastitis in this area, necessitating additional epidemiological research that includes healthy matched controls. Full article

Antimicrobial resistance (AMR) emerges and circulates across interconnected human, animal, food, and environmental reservoirs; however, food fermentation systems remain underexplored as indicators of local AMR pressure, even though artisanal dairy fermentations may function as natural sentinels of AMR. In this study, we used an artisanal dairy fermentation chain as a One Health model to investigate whether environmentally exposed lactobacilli can reflect stage-associated shifts in resistance. A total of 1.085 isolates representing 16 Lactobacillus species were recovered from the same artisanal dairy matrix at two fermentation stages: day 5 (“Tyrovolia”; n = 518) and day 30 (“Kopanisti”; n = 567). Susceptibility to 14 antibiotics was evaluated by broth micro-dilution, and L. acidophilus was further screened for selected resistance genes. Overall resistance increased significantly from 69.88% (362/518) at day 5 to 77.25% (438/567) at day 30 (p = 0.0059), while multidrug resistance rose from 37.57% to 60.73% of resistant isolates (p < 0.001). Across the 224 species–antibiotic combinations examined, 129 (57.58%) showed an increased upper MIC limit at day 30, and resistance increased significantly for 9 of the 14 antibiotics tested, with the largest rises observed for metronidazole (RR = 7.67), chloramphenicol (RR = 5.74), quinupristin/dalfopristin (RR = 4.11), vancomycin (RR = 2.78), and trimethoprim (RR = 2.43). In contrast, erythromycin and oxytetracycline resistance declined significantly at the ripened stage. In L. acidophilus, 21 resistance genes were detected in 14/70 day-5 isolates and 19 genes in 13/71 day-30 isolates, but marked genotype–phenotype discordance was observed, including matrix-dependent expression patterns for tetM, ermB, and blaTEM. Collectively, these findings show that environmentally exposed artisanal dairy fermentations can enrich resistance phenotypes and may serve as sensitive sentinels of AMR dynamics at the human–animal–environment interface. Full article

Group B Streptococcus (GBS) remains a major cause of early- and late-onset neonatal sepsis worldwide, despite the widespread use of intrapartum antibiotic prophylaxis (IAP). β-lactam antibiotics, including penicillin G and ampicillin, remain the cornerstone of both GBS prophylaxis and neonatal treatment, supported by sustained susceptibility, favorable pharmacokinetics, and extensive clinical experience. However, increasing global resistance to macrolides and lincosamides has markedly reduced the reliability of clindamycin and erythromycin, which are commonly used as second-line agents in women with severe penicillin allergy. This narrative review summarizes current evidence on antibiotic strategies for the prevention and treatment of neonatal GBS disease, with a particular focus on antimicrobial resistance patterns and their clinical implications. Available surveillance data demonstrate substantial geographic variability in resistance but consistently low resistance to β-lactams and vancomycin. These trends have expanded the role of vancomycin in IAP for women with high-risk β-lactam allergy and in neonatal treatment when first-line agents are contraindicated. Alternative agents such as linezolid and teicoplanin exhibit activity against GBS, but their use remains limited by sparse neonatal data and pharmacokinetic variability. Ongoing antimicrobial surveillance, susceptibility-guided therapy, and stewardship initiatives are essential to preserve effective GBS prevention and treatment strategies. Full article

Hybrid nanomaterials that integrate surface functionality, colloidal stability, and efficient electron-transfer pathways are highly attractive for improving electrochemical sensing performance. Herein, we report the fabrication and evaluation of polyethyleneimine-functionalized gallium nitride nanoparticles (GaN) decorated with gold nanoparticles (GaN-PEI-Au) as a tunable electrode modifier for enhanced differential pulse voltammetry (DPV) detection of erythromycin. Branched polyethyleneimine was employed as a multifunctional interfacial layer to stabilize GaN dispersions, introduce amine-rich surface chemistry, and enable in situ gold nanoparticle formation at the GaN-PEI. The optimized GaN-PEI-Au material exhibited high colloidal stability, a characteristic Au localized surface plasmon resonance in the ~520–525 nm range, and well-defined Au nanoparticles attached to the GaN surface. When applied as an electrode coating, GaN-PEI-Au significantly enhanced the erythromycin oxidation response compared to bare Au and GaN-PEI interfaces, consistent with synergistic increases in electroactive surface area and interfacial charge-transfer efficiency. Under optimized DPV conditions, GaN-PEI-Au-modified electrodes enabled quantitative erythromycin determination with a linear range of 5 nM–2 µM (R² = 0.990), sensitivity of 1.32 × 10⁻³ µA nM⁻¹, and a limit of detection of 52.5 nM, while maintaining stable baseline behavior during repeated scans. The reported GaN-PEI-Au nanocomposites represent a robust platform for sensitive electrochemical detection of pharmaceutical compounds. Full article

Background/Objectives: The aim of this study was to clarify the antimicrobial susceptibility and distribution characteristics of Mycoplasma pneumoniae (M. pneumoniae, MP) collected from children in Beijing, China, from 2017 to 2025. Methods: A total of 197 MP isolates were analyzed. Mutations in macrolide-resistant loci of MP strains were detected via real-time fluorescent quantitative polymerase chain reactions. We used the broth microdilution method to determine the minimum inhibitory concentrations (MICs) of erythromycin, azithromycin, tetracycline, levofloxacin, and moxifloxacin against these isolates. The distribution characteristics of MIC values were further analyzed according to the isolates’ collection year, epidemic phase (low epidemic phase, epidemic initiation phase, ultra-low epidemic phase, outbreak phase, and epidemic recovery phase), and the corresponding patient age group (<3 years, 3–6 years, and ≥6 years). Results: All 197 isolates were found to be resistant to erythromycin and azithromycin, with a resistance rate of 100%. In contrast, the strains remained susceptible to tetracycline, levofloxacin and moxifloxacin. The highest resistance rate was 100% for macrolides. The MIC₉₀ values were 1024 μg/mL for erythromycin, 256 μg/mL for azithromycin, 0.5 μg/mL for tetracycline, 1 μg/mL for levofloxacin, and 0.125 μg/mL for moxifloxacin, respectively. Distinct differences in MIC distributions of erythromycin and azithromycin were observed across collection years, epidemic phases, and age groups. Conclusions: The resistance of MP to macrolides in children is closely associated with the epidemic intensity and age of the patient. Erythromycin is no longer suitable as an empirical therapy for MP infections during epidemic periods, whereas azithromycin can be cautiously administered in young children according to age stratification and MIC detection results. Meanwhile, it is imperative to strengthen the prevention and control of cluster MP infections during epidemic phases to reduce the transmission of drug-resistant MP strains. Full article

Listeria innocua is a bacterium frequently detected in food and food production plants (FPPs). Understanding the heterogeneity of L. innocua food isolates is essential for predicting potential food safety threats and developing preventive and control measures. This study aimed to characterize L. innocua isolated from raw drinking milk by investigating the genomic features related to virulence, antimicrobial resistance, and persistence using whole-genome sequencing (WGS), along with phenotypic antimicrobial susceptibility testing using the disk diffusion method. All ten isolates analyzed in this study belonged to sequence type (ST) 492 and were distantly related to the reference strain. A total of 80 virulence-associated genes were identified, including the complete Listeria Pathogenicity Islands-3 (LIPI-3) and LIPI-4 clusters typically found in virulent L. monocytogenes clones, as well as 66 additional genes involved in adhesion, invasion, motility, post-translational modification, regulation, immune modulation, and stress survival. Stress survival islet 2 (SSI-2) and genes encoding the Clp protease complex (clpC, clpE, clpP), which support both persistence and virulence, were also detected, whereas LIPI-1 and internalin genes were not detected. The antimicrobial resistance determinants included fosX, lin, norB, sul, and three multidrug efflux pumps (lde, mdrL and mdrM). Mobile genetic elements (plasmids, prophages, or transposons) were not detected. All isolates were phenotypically susceptible to benzylpenicillin, ampicillin, meropenem, erythromycin, and trimethoprim–sulfamethoxazole. These findings underscore the importance of ongoing genomic surveillance of L. innocua in food environments and highlight the need to assess the potential risk posed by specific lineages, such as ST492, to food safety. Full article

Background: Ribociclib, initially approved for HR+/HER2− advanced breast cancer (ABC) at a 600 mg dose, was recently approved for HR+/HER2− early breast cancer (EBC) at a 400 mg dose based on the NATALEE trial. Differences in dose and patient population warrant reassessment of ribociclib drug–drug interactions (DDIs) and the impact of hepatic or renal impairment (HI/RI) in EBC patients to guide co-medication management and subpopulation dose recommendations. Methods: Physiologically-based pharmacokinetic (PBPK) modeling based on a healthy volunteer population was conducted to assess ribociclib DDIs with CYP3A4 substrates/modulators in patients with EBC. Subgroup analysis from NATALEE assessed HI/RI impact on ribociclib PK in EBC patients. Existing data from ABC/advanced cancer patients and non-cancer subjects were also integrated to inform dose recommendations for EBC subpopulations. Results: PBPK modeling predicted that ritonavir or erythromycin (strong and moderate CYP3A4 inhibitors) would increase ribociclib steady-state area under the concentration–time curve (AUC) by 1.84-fold or show no meaningful impact, respectively. Steady-state ribociclib AUC was estimated to decrease by 83% and 74% with rifampicin and efavirenz, strong and moderate CYP3A4 inducers, respectively. Ribociclib was estimated to increase CYP3A4 substrate midazolam exposure by 280%. Mild HI or mild/moderate RI did not show an apparent impact on ribociclib PK. Conclusions: Using relevant data and methodology for EBC patients, this analysis informed the approved ribociclib label of no dose adjustment for EBC patients with concomitant use of a moderate CYP3A inhibitor, any degree of HI, or mild/moderate RI, and a reduced 200 mg dose for patients with concomitant use of a strong CYP3A inhibitor or severe RI. Full article

Natural products such as polyketides are a fertile target for drug discovery. Methodologies relating to discovery, metabolism, synthesis and biosynthesis of polyketides have evolved considerably since they were first studied in the early 20th century. The antibiotic erythromycin, produced by the Streptomyces erythreus bacteria, was the first of the macrolide natural products to be discovered in 1952. The biosynthesis of erythromycin is catalysed by a large multifunctional enzyme, which constructs the polyketide intermediate that is acted upon by tailoring enzymes to produce the final construct. It is during this process that molecular diversity is generated, and commercial samples of erythromycin tend to be mixtures of co-metabolites. To fully identify these compounds, a full fragmentation scheme of the main component (erythromycin A) is required, which is absent from the literature. In this study, accurate-mass sequential mass spectrometry is used to propose a fragmentation scheme which is then used to assign structures to eight co-metabolites including the identification of a previously unpublished form of erythromycin. This clearly demonstrates the successful application of the methodology. Full article

Background: Ureaplasma spp. and Mycoplasma hominis are urogenital pathogens that may be missed by routine culture, particularly in patients with genitourinary symptoms in whom conventional methods fail to identify an etiologic agent. Limited routine implementation of targeted diagnostics and antimicrobial susceptibility testing (AST) for these organisms may contribute to diagnostic uncertainty and treatment failure. Methods: Seventy-five midstream urine samples submitted for suspected urinary tract infection and positive for Ureaplasma spp. according to a q-PCR urinary panel (Bioeksen, İstanbul, Türkiye) were tested the same day with MYCOPLASMA IST3 (bioMérieux, Marcy-l’Étoile, France) to assess growth and antimicrobial susceptibility. Results: q-PCR detected U. parvum in 54/75 (72%), U. urealyticum in 15/75 (20%), and both species in 6/75 (8%); M. hominis was not included in the PCR panel. MYCOPLASMA IST3 showed growth in 70/75 samples (positive percent agreement, 93.33%), while 5/75 (discordance, 6.66%) showed no growth. Among culture-positive samples, 57/70 (81.42%) yielded Ureaplasma spp. alone, and 13/70 (18.58%) yielded Ureaplasma spp. together with M. hominis. Resistance to levofloxacin and tetracycline was observed in 15.7% and 12.9% of Ureaplasma spp. isolates, respectively; resistance to moxifloxacin, erythromycin, and telithromycin was observed in 2.9% of isolates for each agent. In M. hominis isolates, no resistance to levofloxacin, moxifloxacin, or tetracycline was observed, whereas clindamycin resistance was observed in 7.7% of isolates. Conclusions: In addition to intrinsic resistance, acquired antimicrobial resistance in Ureaplasma and Mycoplasma species appears to be increasing; therefore, treatment decisions should be guided by AST whenever feasible. Clinical laboratories should implement appropriate diagnostic methods for these organisms and perform susceptibility testing when indicated to support clinical decision making and optimize antimicrobial selection. Full article