Search Results (1,067)

Background/Objectives: The widespread use of antibiotics in livestock has raised concerns about commensal gut bacteria, such as lactic acid bacteria (LAB), acting as reservoirs for antimicrobial resistance. This study aimed to characterize the antibiotic resistance profiles of LAB isolated from livestock feces by combining phenotypic susceptibility testing with whole-genome sequencing (WGS) to identify antibiotic resistance genes (ARGs) and their genomic context. Methods: Four LAB strains from farm animal fecal samples were subjected to antibiotic susceptibility testing for 9 antibiotics (ampicillin, gentamicin, kanamycin, clindamycin, chloramphenicol, erythromycin, streptomycin, tetracycline, and vancomycin) using MIC determinations. WGS was performed on each isolate to detect ARGs using curated databases and to determine the chromosomal or plasmid location of these genes. Results: All four isolates exhibited phenotypic resistance to at least one antibiotic class, most frequently to aminoglycosides. However, discrepancies between phenotype and genotype were noted: resistance to aminoglycosides was common despite the absence of known aminoglycoside-resistance genes, suggesting intrinsic, uptake-related mechanisms. In contrast, one strain carried the chromosomal lsa(D) gene but remained susceptible to clindamycin. WGS revealed that all strains harbored the chromosomal van(T) gene, while one isolate carried three additional plasmid-borne ARGs—erm(B), cat(A), and tet(W)—conferring resistance to macrolide–lincosamide–streptogramin antibiotics, chloramphenicol, and tetracycline. Another strain encoded van(Y), lsa(D), and arr on its chromosome. The detection of multiple plasmid-located ARGs in a single LAB isolate highlights their potential for horizontal gene transfer. Conclusions: This study provides a detailed phenotypic and genomic insight into antibiotic resistance in gut-derived LAB from livestock. The findings highlight that commensal LAB can harbor clinically relevant ARGs—sometimes on mobile genetic elements—without always expressing corresponding resistance phenotypes. Such LAB may serve as a hidden reservoir for antibiotic resistance, raising the risk of ARG dissemination through the food chain. These results underscore the importance of vigilant monitoring and genomic screening of LAB, especially those considered for use in foods or feed, to ensure they do not contribute to the spread of antimicrobial resistance. Full article

Background: Antibiotic-loaded bone cement (ALBC) is widely used for local antibiotic delivery in joint arthroplasty to prevent and treat prosthetic joint infections (PJIs). In this study, we evaluated the efficacy of cemented Kirschner (K)-wires coated with various ALBC formulations using a Galleria mellonella infection model against multidrug-resistant (MDR) Staphylococcus aureus and Enterococcus faecalis. Methods: We tested commercially available bone cements, including gentamicin-only formulations (PALACOS R+G) and dual-antibiotic formulations, combining gentamicin with either clindamycin (COPAL G+C) or vancomycin (COPAL G+V), alongside an antibiotic-free control (PALACOS R). In vitro assays—including minimum inhibitory/bactericidal concentration (MIC/MBC) determination, antibiotic release kinetics, agar diffusion, and antibiofilm evaluations—demonstrated effective antibiotic release and significant antimicrobial activity against both planktonic and biofilm-associated bacteria. Results: In vivo, ALBC-coated K-wires were well tolerated in G. mellonella and significantly protected the larvae from S. aureus infection compared to controls. Notably, dual-antibiotic formulations provided superior protection, correlating with substantial reductions in bacterial colonisation on implant surfaces and in surrounding tissues. Conclusions: These findings support the utility of the G. mellonella model as a high-throughput, cost-effective platform for the preclinical evaluation of antimicrobial strategies to prevent and treat PJIs and further demonstrate the effectiveness of dual-loaded ALBC against multidrug-resistant bacteria. Full article

Background: To meet the urgent need for novel antibacterial agents that are active also against worrying superbugs, natural pentacyclic triterpenoids, including totally inactive betulin (BET) and betulinic acid (BA), as well as ursolic acid (UA), active on Gram-positive bacteria, have been chemically modified, achieving compounds 1–7. Methods: Triterpenoid derivatives 1–7 and all synthetic intermediates were characterized by chemometric-assisted FTIR and NMR spectroscopy, as well as by other analytical techniques, which confirmed their structure and high purity. Minimum inhibitory concentration values (MICs) of 1–7, BET, BA and UA were determined by the broth dilution method, using a selection of Gram-positive and Gram-negative clinically isolated superbugs. Results: Performed experiments evidenced that compounds 4–7 had potent antibacterial effects against Gram-positive methicillin-resistant Staphylococcus aureus and S. epidermidis (MRSA and MRSE), as well as against vancomycin-resistant Enterococcus faecalis and E. faecium (VRE). The antibacterial effects of 4–7 were due to the insertion of a triphenyl phosphonium (TPP) group and were higher than those reported so far for other BET, BA and UA derivatives, especially considering the complex pattern of resistance of the isolates used here and their clinical source. Conclusions: For the first time, by inserting TPP, a real activity (MICs 2–16 µg/mL) was conferred to inactive BET and BA (MICs > 1024 and 256 µg/mL). Moreover, the antibacterial effects of UA were improved 16- and 32-fold against MRSE and MRSA (MICs = 2 vs. 32 and 64 μg/mL). Future Perspectives: Based on these very promising microbiologic results, new experiments are currently underway with the best-performing compounds 5 and 7 (MICs = 2 μg/mL) on an enlarged number of Gram-positive isolates, to confirm their MICs. Moreover, investigations about their possible antibiofilm activity, time-killing curves and cytotoxicity on eukaryotic cells will be carried out to define their pharmacological behavior and clinical potential. Full article

Urinary tract infections (UTIs) represent one of the most frequent bacterial infections worldwide, with Escherichia coli (E. coli) and Klebsiella pneumoniae (K. pneumoniae) as the predominant uropathogens. The emergence of extended-spectrum β-lactamase (ESBL)-producing Enterobacterales has severely limited treatment options, making regional surveillance crucial. This study aimed to determine the prevalence of uropathogens, assess antimicrobial resistance patterns, and evaluate the burden of ESBL-producing organisms among patients presenting with suspected UTIs in a tertiary care hospital in Riyadh. We conducted a retrospective analysis of 19,556 urine cultures from a tertiary care hospital in Riyadh, Saudi Arabia, between January and December 2024. Of these, 2629 (13.4%) cultures showed significant bacterial growth, predominantly in females (83.2%) and in the 16–30 year age group. E. coli accounted for 65.9% of isolates, followed by K. pneumoniae (16.8%). ESBL production was detected in 28.5% of E. coli and Klebsiella isolates. ESBL producers exhibited complete resistance to third-generation cephalosporins and β-lactam/β-lactamase inhibitor combinations, whereas carbapenems, aminoglycosides, and fosfomycin maintained high efficacy. Resistance to ciprofloxacin and co-trimoxazole was widespread in both ESBL and non-ESBL isolates. Additionally, vancomycin-resistant enterococci (7%), methicillin-resistant Staphylococcus aureus (2%), and carbapenem-resistant Enterobacterales (0.9%) were found. These findings highlight the escalating burden of ESBL-associated UTIs and underscore the urgent need for strengthened antimicrobial stewardship, continuous surveillance, and optimized empirical therapy to mitigate the impact of multidrug-resistant uropathogens in clinical practice. Full article

Background/Objectives: Clostridioides difficile is an anaerobic Gram-positive bacterium and a leading cause of healthcare-associated diarrhea. In this study, C. difficile strains isolated from human patients with diarrhea and companion dogs in South Korea were compared to reveal the potential transmission between different hosts. Methods: A total of 304 C. difficile strains were isolated, including 217 human isolates and 87 dog isolates. The strains were characterized for antimicrobial susceptibility and genotypic features, including antimicrobial resistant genes and toxin genes. In addition, comparative genomic analyses were performed to investigate their genetic relatedness. Results: Although antimicrobial susceptibility test revealed no significant difference in overall resistance, human isolates had higher resistance to moxifloxacin and cefotetan, while dog isolates showed slightly higher resistance to clindamycin and ampicillin. Resistance to vancomycin (3.7%), rifampin (8.3%), and chloramphenicol (0.9%) was observed only in human isolates. Toxin genes (tcdA and tcdB) were found in 57.1% of human isolates and 43.7% of dog isolates, while binary toxin genes (cdtA and cdtB) were detected only in isolates from humans. Multilocus sequence typing (MLST) analysis identified 34 sequence types (STs) in human isolates and 16 in dog isolates. Among them, 15 STs were detected in the isolates from both origins; notably, ST203 and ST42 were the predominant taxa that were equally derived from humans and dogs. Although tcdA and tcdB have not been previously reported in ST203, they were detected in 7 out of 34 ST203 isolates. The whole genomes of 36 representative isolates belonging to ST42 and ST203 were classified according to the STs of the source origin. Conclusions: These results indicate that similar C. difficile strain populations are present in both humans and companion dogs, which is compatible with interspecies dissemination or circulation of shared strain populations, and may also reflect host adaptation. Full article

We investigated the effects of vancomycin, estradiol, ethanol, and their combinations on the growth of mono- and binary-species biofilms of Lactobacillus paracasei and Staphylococcus aureus. It was found that vancomycin at a subinhibitory concentration of 0.001 µg/mL, estradiol, and ethanol acted antagonistically in all cases. This effect was observed across all strains studied. Furthermore, the effects of the active compounds were evident at population, cellular and molecular levels, and were reflected in changes to the count of colony-forming units (CFUs), gene expression, and the physiological and biochemical characteristics of cells (e.g., lipid composition of membranes and the extracellular matrix). Therefore, at subinhibitory concentrations of vancomycin in the medium, estradiol can modulate the antibiotic’s effect on biofilms, thereby regulating deeply microbial communities. Full article

Background: Antimicrobial resistance (AMR) is a growing public health concern affecting both medicine and food safety. While Listeria monocytogenes is the primary pathogen of concern, Listeria innocua—commonly found in food and food-processing environments—may serve as a reservoir for resistance genes and a useful indicator of species for surveillance. This study aimed to assess the phenotypic antibiotic susceptibility and detect resistance-associated genes in L. innocua isolates from meat products and processing environments in Poland. Methods: A total of 51 L. innocua isolates were analyzed, originating from raw and processed meat products as well as meat-processing environments. Antimicrobial susceptibility was determined using the disc diffusion method against 18 antibiotics representing multiple classes. Phenotypic resistance was interpreted following CLSI guidelines (CLSI, 2020). Isolates exhibiting resistance or intermediate resistance were further screened for resistance-associated genes using PCR. Results: All isolates were fully susceptible to ampicillin, benzylpenicillin, chloramphenicol, gentamicin, rifampin, trimethoprim-sulfamethoxazole, and vancomycin. High susceptibility was observed for ciprofloxacin, erythromycin, meropenem, trimethoprim, and nitrofurantoin, with only sporadic intermediate responses. Moderate resistance levels were noted for streptomycin (10%) and tetracycline (12%). The lowest susceptibility was recorded for clindamycin and linezolid, with most isolates exhibiting intermediate or resistant phenotypes. Universal resistance to cefotaxime and oxacillin was found. Eighteen distinct resistance patterns were identified. PCR confirmed the presence of several resistance-associated genes, including mecA, lnuA, lnuB, cfr, optrA, and poxtA, consistent with observed phenotypes. Conclusions: This study provides the first detailed characterization of AMR in L. innocua from Polish meat and processing environments. The findings highlight its heterogeneous resistance profiles and potential role as a reservoir of clinically relevant resistance genes. Incorporating L. innocua into surveillance programs may strengthen early detection of emerging resistance and enhance food safety monitoring. Full article

Background: Biliary peritonitis is a severe intra-abdominal emergency with high mortality. Effective management requires source control and appropriate antimicrobial therapy. Methods: This review synthesizes recent literature (2016–2025), as well as established guidelines recommendations on the evolving microbiology and antimicrobial resistance patterns in biliary tract infections, as data on biliary peritonitis is scarce and relatively heterogeneous. Results: The microbiological landscape is stratified by patient history. Community-acquired infections are typically caused by Escherichia coli, Klebsiella pneumoniae, and Enterococcus spp. In contrast, healthcare-associated infections show a shift, with highly resistant pathogens such as Pseudomonas aeruginosa, and a tendency towards polymicrobial infections. The rise of multidrug-resistant (MDR) organisms, including extended-spectrum β-lactamase (ESBL)-producing Enterobacterales, Carbapenem-Resistant Enterobacterales (CRE), and Vancomycin-Resistant Enterococci (VRE), is a critical challenge limiting therapeutic options. Resistance patterns vary geographically, necessitating the use of local data. Conclusions: This review argues for a paradigm shift from severity-based guidelines to a dual-axis model incorporating resistance risk factors (prior healthcare exposure, previous biliary interventions, a history of MDR infections). We propose a risk-stratified approach to empiric antibiotic selection, emphasizing microbiological diagnostics for therapy de-escalation. Future research should focus on prospective studies, novel antibiotics, and rapid diagnostics. Full article

Migratory birds travel long distances and interact with diverse environments, making them potential reservoirs and disseminators of antimicrobial-resistant bacteria. This study investigated the species distribution of migratory birds, bacterial isolates from bird internal organs, and the corresponding antimicrobial resistance (AMR) profiles in South Korea. A total of 35 bird carcasses representing 20 species were collected from five major stopover sites on the Sinan-gun islands along the East Asian–Australasian Flyway. More than half of the sampled birds belonged to the genus Emberiza, reflecting the prevalence of small migratory passerines in coastal habitats. From these carcasses, 54 bacterial isolates belonging to 24 species were identified, including Enterococcus spp., coliforms such as Enterobacter spp. and Escherichia coli, and opportunistic pathogens including Bacillus spp., Staphylococcus spp., and Serratia spp. Antimicrobial susceptibility testing revealed that 18 isolates (33.3%) were multidrug-resistant (MDR). Enterococcus isolates displayed high resistance to tigecycline and daptomycin, and two vancomycin-resistant strains were identified. Coliform isolates were resistant to third- and fourth-generation cephalosporins, carbapenems, and colistin. The two E. coli strains exhibited concurrent carbapenem–colistin resistance, posing a significant public health concern. These findings provide the first organ-level AMR dataset for migratory birds in South Korea and highlight the potential role of small passerines as ecological sentinels of environmental contamination. The detection of MDR strains underscores the need to integrate wildlife surveillance into One Health strategies for AMR monitoring. Full article

Backgrounds/Objectives: This study aimed to quantify biofilm production and characterize the distribution of the biofilm-associated ica genes (icaA, icaD, icaB, icaC, icaR) in coagulase-negative staphylococci (CoNS) isolates, and to assess the association between these genes and antibiotic resistance profiles. Methods: A total of 121 CoNS isolates collected at Ümraniye Training and Research Hospital between 1 January and 30 August 2024 were identified by VITEK 2 Compact and MALDI-TOF MS. Biofilm production was quantified using the microtiter plate assay, and the presence of ica genes was determined by quantitative real-time PCR (qPCR). Antimicrobial susceptibility testing (AST) was performed with the VITEK 2 Compact (bioMérieux), and minimum inhibitory concentrations (MICs) were interpreted according to EUCAST criteria. Results:S. epidermidis was found to have the highest biofilm production capacity among the CoNS isolates, followed by S. haemolyticus. The icaA gene was detected in 99.17% of isolates, followed by icaR (70.24%), icaD (55.37%), and both icaB and icaC (28.92% each). The highest resistance rates were observed for oxacillin (85.8%) and erythromycin (85.1%), while all isolates remained susceptible to linezolid, daptomycin, and vancomycin. Conclusions: The high prevalence of ica genes in CoNS isolates indicates that biofilm formation plays a critical role in the pathogenesis of these species. The findings reveal that CoNS have a strong biofilm production potential, which is a decisive factor in their pathogenicity. However, the high methicillin resistance rates emerge as one of the main factors limiting the effectiveness of current treatment options. Therefore, future studies need to focus on the development of anti-biofilm approaches and alternative therapeutic strategies. Full article

Hemorrhagic septicemia (HS) is a fulminant bovine disease across Asia and Africa, yet Pasteurella multocida (P. multocida) isolated from yak is poorly reported. We isolated strain NQ01 from a fatal HS case in Xizang, China and identified it as P. multocida B:2 by morphology, Gram stain, and PCR (kmt1⁺, bcbD⁺, LPS L2). NQO1 formed smooth, non-hemolytic colonies. After Gram staining, the cells appeared as red rods with bipolar staining. Antimicrobial testing showed broad susceptibility to β-lactams, aminoglycosides, tetracyclines, fluoroquinolones, midecamycin, florfenicol, polymyxin, and vancomycin, with resistance to metronidazole, trimethoprim sulfamethoxazole, and clindamycin. Streptomycin and ofloxacin had intermediate activity. In mice, the intraperitoneal and intranasal LD₅₀ values were 40.64 CFU/mL and 9.53 × 10⁶ CFU/mL, respectively. The intranasal fatal cases were characterized by bacteremia with multifocal disseminated intravascular coagulation involving lung, liver, and spleen. The complete genome comprises a single 2.33 Mb chromosome (40.47% GC, 2115 CDS, no plasmids) with only one resistance gene (Eco_EFTu_PLV) and 28 virulence genes spanning adhesion (tadA, rcpA, ppdD, pilB, tuf/tufA, htpB, PM_RS00430, PM_RS00425, PM_RS08640), immune modulation (lpxB/C/D, msbB, manB, rfaE/F, gmhA/lpcA, kdsA, pgi, wecA, galE, bexD’, ABZJ_RS06285, ABD1_RS00310), and nutritional/metabolic factor (hgbA, hemR, hemN), plus a YadA-like factor. Phylogenetically, NQ01 clusters with regional B:2 bovine/yak isolates. Collectively, these data define NQ01 as a highly virulent, low-resistance yak isolate and a practical model for natural-route HS pathogenesis and targeted control in high-altitude pastoral settings yaks. Full article

Background/Objectives: Linezolid is a first-in-class oxazolidinone antibiotic that exhibits activity against Gram-positive pathogens, including methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci. However, its clinical use is often restricted because of hematological toxicities, particularly thrombocytopenia, in patients with renal impairment. That side effect is thought to result from the systemic accumulation of pharmacologically inactive metabolites generated by oxidative degradation and ring-opening of the morpholine, but the details remain unclear. In this study, we established a novel synthetic route for four linezolid metabolites (PNU-142618, 142300, 142586 and 173558). Methods: The four major metabolites, which are secondary or tertiary amines, were synthesized using the aniline derivatives protected with a 2-nitrobenzensulfonyl (Ns) group. Results: Application of this Ns strategy enabled selective N-alkylation, enabling efficient synthesis of the target metabolites. The desired metabolites containing a carboxylic acid group were obtained as their sodium salts. This is the first report on the synthesis of PNU-142618 and 173558. Conclusions: The established synthetic pathway provides access to four linezolid metabolites. The results facilitated the provision of compounds necessary for comprehensive pharmacokinetic and toxicological studies. Full article

Background: Small-scale food animal production is common worldwide but often underestimated as a source of antimicrobial resistance. This study aimed to determine the prevalence of MRSA and VRE-E. faecium, and ESBL-E. coli bacteria among workers and within the production environment of low-capacity slaughterhouses, as well as to analyze the antimicrobial resistance patterns of these bacteria and their ability to form biofilms. Methods: The measurements were carried out in three low-capacity slaughterhouses in Poland. Bioaerosol samples, swabs from the production environment fomite and carcasses, meat samples, and swabs from workers’ hands and nostrils were taken. The strains’ susceptibility to antibiotics was assessed using the disk diffusion method, and their biofilm-forming potential was assessed using the microplate method. Isolates were also tested for the presence of genes related to biofilm formation and resistance to antiseptics. Results: In this study, 13.8%, 20.5%, and 14.9% of the samples (n = 268) were positive for MRSA, ESBL-E. coli, and VRE-E. faecium, respectively, with the highest detection rates on pork carcasses and surfaces. MRSA and ESBL-E. coli bacteria were also detected in swabs from workers’ hands and nasal swabs, and in bioaerosol samples. Most isolates revealed multidrug resistance, including 89% of MRSA, 76% of ESBL-E. coli, and 83% of VRE-E. faecium. The majority of them were also capable of biofilm formation—81%, 65%, and 75%, respectively—emphasizing their survival capabilities in slaughterhouse environments. Conclusions: The slaughterhouse workers are regularly exposed to antibiotic-resistant bacteria such as MRSA, ESBL-E. coli, and VRE-E. faecium. To reduce these risks, it is essential for small slaughterhouses to strictly follow hygiene protocols, enhance the separation between clean and contaminated areas, improve ventilation, and ensure the use of protective measures. Full article

Milk contains wide microbial diversity, composed mainly of lactic acid bacteria (LAB), which are used as probiotics for both humans and livestock. We isolated, characterized, and evaluated LAB from indigenous Saudi Arabian camel milk to assess its probiotic potential, including antagonistic activity (against Methicillin-Resistant Staphylococcus aureus (MRSA) and Klebsiella pneumoniae), survivability in simulated gastric juice, tolerance to bile salts, cell surface hydrophobicity, auto- and co-aggregation, and antibiotic susceptibility tests. The two most promising LAB strains showed probiotic potential and were identified as Leuconostoc mesenteroides based on 16S rRNA gene sequences. These strains inhibited all pathogens tested to varying degrees and were resistant to kanamycin and vancomycin. None of the LAB cultures demonstrated hemolytic or gelatinase activity. Overall, the current data suggests that camel milk has substantial potential for introducing probiotics/LAB strains into the human food chain, making camel milk a potentially sustainable food. Full article

Antibiotic-resistant microbes represent a growing problem for modern medicine and public health. Projections indicate that deaths from such infections could reach 10 million per year by 2050. Healthcare associated infections (HAI) are among the most significant causes of mortality and morbidity in hospitals, impacting millions of patients globally. The emergence of HAI is associated with resistance to antimicrobials, rapidly worsening the patient’s condition. Antimicrobial resistance determines unresponsiveness to treatment, which can ultimately lead to severe complications such as sepsis and shock. It is estimated that one in every ten patients are susceptible to infection during their stay in hospital, with the microorganism responsible for the infection frequently proving resistant to antibiotics. Among the latter, CRE (carbapenem-resistant Enterobacteriaceae), CRAB (carbapenem-resistant Acinetobacter baumannii), CRPA (carbapenem-resistant Pseudomonas aeruginosa), vancomycin-resistant Enterococcus spp. and methicillin-resistant Staphylococcus aureus (MRSA), commonly referred to as ‘superbugs’, are a major cause of HAIs. The aim of the present study is to provide a comprehensive overview of the global epidemiology of healthcare-associated infections, with particular emphasis on their incidence, distribution over time, and correlation with the socioeconomic status of different countries. Furthermore, the review aims to evaluate the effectiveness of current preventive strategies in reducing the incidence and mortality associated with HAIs. Full article