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Keywords = vancomycin-resistant enterococcus

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19 pages, 1817 KB  
Article
Urinary Tract Infections in a Single-Center Bulgarian Hospital: Trends in Etiology, Antibiotic Resistance, and the Impact of the COVID-19 Pandemic (2017–2022)
by Milena Yancheva Rupcheva, Kostadin Kostadinov, Yordan Kalchev, Petya Gardzheva, Eli Hristozova, Zoya Rachkovska, Gergana Lengerova, Andreana Angelova, Marianna Murdjeva and Michael M. Petrov
Antibiotics 2025, 14(10), 982; https://doi.org/10.3390/antibiotics14100982 - 30 Sep 2025
Viewed by 470
Abstract
Background: Urinary tract infections (UTIs) are among the most common hospital- and community-acquired infections, creating a substantial healthcare burden due to recurrence, complications, and rising antimicrobial resistance. Accurate diagnosis and timely antimicrobial therapy are essential. This study aimed to identify trends in [...] Read more.
Background: Urinary tract infections (UTIs) are among the most common hospital- and community-acquired infections, creating a substantial healthcare burden due to recurrence, complications, and rising antimicrobial resistance. Accurate diagnosis and timely antimicrobial therapy are essential. This study aimed to identify trends in the etiology, treatment, and resistance patterns of UTIs through a retrospective analysis of urine isolates processed at the Laboratory of Microbiology at University Hospital St. George in Plovdiv, the largest tertiary care and reference microbiology center in Bulgaria, between 2017 and 2022. Materials and Methods: A retrospective single-center study was performed at the hospital’s Microbiology Laboratory. During the study period, 74,417 urine samples from 25,087 hospitalized patients were screened with the HB&L UROQUATTRO system. Positive specimens were cultured on blood agar, Eosin-Methylene Blue, and chromogenic media. Identification was performed using biochemical assays, MALDI-TOF MS, and the Vitek 2 Compact system. Antimicrobial susceptibility testing included disk diffusion, MIC determination, broth microdilution (for colistin), and Vitek 2 Compact, interpreted according to EUCAST standards. Descriptive analysis and temporal resistance trends were evaluated with regression models, and interrupted time-series analysis was applied to assess COVID-19-related effects. Results: Out of 10,177 isolates, Gram-negative bacteria predominated (73%), with Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis as the leading pathogens. Among Gram-positives, Enterococcus faecalis was the most frequent. In the post-COVID-19 period, ESBL production increased in E. coli (34–38%), K. pneumoniae (66–77%), and P. mirabilis (13.5–24%). Carbapenem resistance rose in K. pneumoniae (to 40.6%) and P. aeruginosa (to 24%), while none was detected in E. coli. Colistin resistance increased in K. pneumoniae but remained absent in E. coli and P. aeruginosa. High-level aminoglycoside resistance in E. faecalis was stable (~70%), and vancomycin resistance in E. faecium rose from 4.6% to 8.9%. Conclusions: Both community- and hospital-acquired UTIs in Southeastern Bulgaria are increasingly linked to multidrug-resistant pathogens, particularly ESBL-producing and carbapenem-resistant Enterobacterales. Findings from the region’s largest referral center highlight the urgent need for continuous surveillance, rational antibiotic use, and novel therapeutic approaches. Full article
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21 pages, 5613 KB  
Article
ESKAPE Pathogens in Bloodstream Infections: Dynamics of Antimicrobial Resistance from 2018 to 2024—A Single-Center Observational Study in Poland
by Aneta Guzek, Dariusz Tomaszewski, Zbigniew Rybicki, Wiesław Piechota, Katarzyna Mackiewicz, Monika Konior and Anna Olczak-Pieńkowska
J. Clin. Med. 2025, 14(19), 6932; https://doi.org/10.3390/jcm14196932 - 30 Sep 2025
Viewed by 384
Abstract
Background/Objectives: Modern healthcare faces a growing burden of antimicrobial resistance, prominently driven by ESKAPE pathogens. These organisms—Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.—are the leading causes of healthcare-associated infections, associated [...] Read more.
Background/Objectives: Modern healthcare faces a growing burden of antimicrobial resistance, prominently driven by ESKAPE pathogens. These organisms—Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.—are the leading causes of healthcare-associated infections, associated with limited therapeutic options and increased morbidity. Continuous surveillance is crucial for informing empirical therapy and guiding stewardship. Methods: We perform a single-center, seven-year retrospective study (2018–2024) at a 1000-bed tertiary hospital in Warsaw, Poland. Bloodstream isolates of ESKAPE pathogens were identified according to the EUCAST guidelines. Data were analyzed by pathogen, ward, and year of isolation. Results: From 2483 positive blood cultures, 3724 ESKAPE pathogens were recovered. S. aureus and K. pneumoniae predominated, particularly in the Intensive Care Unit and Hematology ward. Resistance analysis revealed persistently high vancomycin resistance in E. faecium, variable but notable methicillin resistance in S. aureus, and frequent ESBL production in K. pneumoniae with an alarming rise in carbapenemase-producing strains, including dual NDM + OXA-48 co-producers. A. baumannii exhibited near-universal multidrug resistance. P. aeruginosa demonstrated lower resistance rates with preserved colistin susceptibility, while Enterobacter spp. remained fully carbapenem-susceptible. Linezolid retained activity against E. faecium, while colistin remained effective against A. baumannii and P. aeruginosa. Modern β-lactam/β-lactamase inhibitor combinations were active against K. pneumoniae. Conclusions: Our findings underscore the critical role of ESKAPE pathogens in bloodstream infections and highlight divergent resistance patterns across species. The emergence of carbapenemase-producing K. pneumoniae and the persistence of multidrug-resistant A. baumannii are of particular concern. Sustained surveillance, robust antimicrobial stewardship, and tailored infection control strategies remained essential to curb the evolving resistance threat in tertiary care settings. Full article
(This article belongs to the Section Infectious Diseases)
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21 pages, 1658 KB  
Article
Vancomycin-Resistant Enterococcus Colonisation in the Patients of a Regional Spinal Cord Injury Unit in Northwest England, United Kingdom: Our Experience with Non-Isolation of VRE Colonised Patients
by Vaidyanathan Subramanian, Bakulesh Madhusudan Soni, Gareth Derick Cummings, Sandra Croston, Kim Lucey, Ruth Hilton and Rachel Hincks
Microorganisms 2025, 13(10), 2257; https://doi.org/10.3390/microorganisms13102257 - 26 Sep 2025
Viewed by 309
Abstract
We reviewed vancomycin-resistant Enterococcus (VRE) colonisation of inpatients of a spinal cord injury centre. The centre consists of one single occupancy en suite room and ten multi-occupancy rooms where two to six patients stay in a cubicle. These patients share bathroom and toilet [...] Read more.
We reviewed vancomycin-resistant Enterococcus (VRE) colonisation of inpatients of a spinal cord injury centre. The centre consists of one single occupancy en suite room and ten multi-occupancy rooms where two to six patients stay in a cubicle. These patients share bathroom and toilet facilities. Active screening for VRE is performed by taking rectal swabs on admission of patients to the spinal unit. The patients, who are colonised with VRE, are not isolated due to constraints in resources. During a twelve-month period (April 2024 to April 2025), 33 patients tested positive for VRE. In April 2025, 17 of 40 in-patients tested positive for VRE. During the last six 12-month periods from 2019, the number of patients testing positive for VRE has shown an upward trend from 18 during 2019–2020 to 33 during 2024–2025. No patient developed systemic infection with VRE (blood stream infection, endocarditis, meningitis, intra-abdominal sepsis, infection of a spinal implant or baclofen pump) during the study period. Twelve patients underwent implantation of a baclofen pump during 2024–2025. No patient developed VRE infection from the implant. We believe that non-isolation of patients colonised with VRE may be a pragmatic approach in a resource-poor healthcare facility. It is possible that non-isolation could have contributed to an increase in the number of patients who became colonised with VRE. Attention should be paid to infection prevention measures including hand washing and environmental cleaning to prevent the spread of VRE colonisation of inpatients and VRE infection of at-risk patients, e.g., immune-compromised individuals. Full article
(This article belongs to the Special Issue Research on Relevant Clinical Infections: 2nd Edition)
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16 pages, 581 KB  
Article
Antimicrobial Resistance in Chicken Meat: Comparing Salmonella, Escherichia coli, and Enterococcus from Conventional and Antibiotic-Free Productions
by Camila Koutsodontis Cerqueira-Cézar, Aryele Nunes da Cruz Encide Sampaio, Evelyn Fernanda Flores Caron, Thaisy Tino Dellaqua, Lucas Franco Miranda Ribeiro, Leonardo Ereno Tadielo, José Carlos de Figueiredo Pantoja, Gustavo Guimarães Fernandes Viana, Gabriel Augusto Marques Rossi, Carlo Spanu, Fábio Sossai Possebon and Juliano Gonçalves Pereira
Microorganisms 2025, 13(10), 2227; https://doi.org/10.3390/microorganisms13102227 - 23 Sep 2025
Viewed by 570
Abstract
Chicken meat production is a critical component of the global protein supply, significantly influenced by rearing advancements, including the use of antimicrobial agents. However, the pervasive use of antibiotics has raised concerns regarding the occurrence of antimicrobial resistance (AMR). This study examined the [...] Read more.
Chicken meat production is a critical component of the global protein supply, significantly influenced by rearing advancements, including the use of antimicrobial agents. However, the pervasive use of antibiotics has raised concerns regarding the occurrence of antimicrobial resistance (AMR). This study examined the prevalence and AMR profiles of Salmonella spp., Escherichia coli, and Enterococcus spp. in chicken meat from conventional and antibiotic-free (ABF) production chains. A total of 284 samples were analyzed for Salmonella spp. and E. coli, while 164 samples were tested for Enterococcus spp. From that, 143 were from conventional production chains and 141 were from ABF chains. The results indicated a 10.9% prevalence of Salmonella spp., 22.1% for E. coli, and 93.9% for Enterococcus spp. Regarding production chains, the conventional chain had 18.2% of the isolates for Salmonella spp., 20.3% for E. coli, and 91.6% for Enterococcus spp., while the ABF chain had 3.5% of the isolates for Salmonella spp., 24.1% for E. coli, and 96.3% for Enterococcus spp. In terms of AMR, 86.1% of the Salmonella spp. isolates that underwent the disk diffusion test were resistant to at least one antibiotic tested, 95.1% of E. coli, and 88.4% of Enterococcus spp. Notably, carbapenem resistance was detected in Salmonella spp., with 2.3% of isolates being resistant to imipenem, while resistance to vancomycin and linezolid was detected in Enterococcus spp., all of which are critically important antimicrobials. Comparisons between these production chains revealed significant differences in antibiotic resistance patterns in Salmonella spp. for two antibiotics, amoxicillin/clavulanic acid and nitrofurantoin, while no differences were observed in E. coli. For Enterococcus spp., resistance varied for three antibiotics: streptomycin, penicillin, and tetracycline. For all other antibiotics tested, the resistance profiles were consistent across both conventional and ABF production chains. Multidrug resistance (MDR) was observed in 90.7% of Salmonella spp. isolates, 42.9% of E. coli isolates, and 12.0% of Enterococcus spp. isolates. Statistically significant differences were noted in MDR prevalence between production chains, with conventional production systems exhibiting higher levels of MDR isolates compared to ABF systems. These findings underscore the need for targeted AMR control strategies that consider the complexity of resistance dynamics across production systems. Full article
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20 pages, 2163 KB  
Article
Characterization of Antimicrobial Resistance Patterns and Resistance Genes of Enterococci from Broiler Chicken Litter
by Tam T. Tran, Niamh Caffrey, Haskirat Grewal, Yuyu Wang, Rashed Cassis, Chunu Mainali, Sheryl Gow, Agnes Agunos, Sylvia Checkley and Karen Liljebjelke
Poultry 2025, 4(3), 42; https://doi.org/10.3390/poultry4030042 - 12 Sep 2025
Viewed by 546
Abstract
Enterococci, commonly found in the normal intestinal flora of humans and animals, have emerged as an important human pathogen. A total of 184 isolates (88 isolates in 2015 and 96 isolates in 2016) were collected from 46 flocks. Two predominant enterococcus species were [...] Read more.
Enterococci, commonly found in the normal intestinal flora of humans and animals, have emerged as an important human pathogen. A total of 184 isolates (88 isolates in 2015 and 96 isolates in 2016) were collected from 46 flocks. Two predominant enterococcus species were identified: Enterococcus faecalis (59%) and Enterococcus faecium (~39%). Resistance to penicillin was significantly decreased in the overall enterococci community, while it remained unchanged in the multi-class drug resistant (MDR) community. We identified the emeA and efrAB genes, which encode efflux pump systems, in 93% (26/28) of the MDR isolates with (intermediate) resistance to levofloxacin. The ermB gene was present in all MDR strains with resistance to erythromycin. The lsa gene was detected in 87% (84/97) of the MDR isolates with resistance to quinupristin/dalfopristin. About 82.2% of MDR strains in 2015 and 100% of MDR strains in 2016 carried the insertion sequence IS256, which is known to be associated with AMR genes, conferring resistance to erythromycin, gentamicin and vancomycin in enterococci. These results support the need for monitoring AMR in Gram-positive bacteria in poultry production, specifically in broiler chicken farms, to complement current AMR data, and develop a timely intervention framework. Full article
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15 pages, 2061 KB  
Article
Isolation and Characterization of Vancomycin-Resistant Enterococcus faecium from Cattle: Antimicrobial Resistance, Virulence Genes, and Pathogenicity
by Mengyuan Cao, Fang Cao, Chenyu Wang, Xueqi Yan, Feng Dong, Shilei Zhang, Shaymaa Abousaad, Lin Yang, Ayman M. Abouzeid, Yongjie Wang and Yayin Qi
Vet. Sci. 2025, 12(9), 880; https://doi.org/10.3390/vetsci12090880 - 12 Sep 2025
Viewed by 514
Abstract
This study aimed to investigate the antimicrobial resistance, virulence gene profile, and pathogenicity of Enterococcus faecium isolated from a large-scale cattle farm in Xinjiang, China, to provide a scientific basis for the prevention and control of E. faecium infections in the region. Nineteen [...] Read more.
This study aimed to investigate the antimicrobial resistance, virulence gene profile, and pathogenicity of Enterococcus faecium isolated from a large-scale cattle farm in Xinjiang, China, to provide a scientific basis for the prevention and control of E. faecium infections in the region. Nineteen rectal swabs were aseptically collected from diarrheic calves for bacterial isolation. Isolates were identified through morphological observation, biochemical characterization, and PCR amplification. Homology analysis was conducted using 16S rRNA gene sequencing. Antimicrobial susceptibility was evaluated by the disk diffusion method, and key virulence genes were detected using PCR. Pathogenicity was assessed through intraperitoneal inoculation of mice, followed by histopathological examination. Three isolates were identified as E. faecium, consistent with morphological and molecular results. Biochemical tests indicated that the strains could metabolize sucrose, maltose, lactose, melibiose, and raffinose, but not sorbitol. Phylogenetic analysis revealed that isolates SCQ3 and SCQ4 shared 99.3% homology with E. faecium strain MF678878.1, while SCQ11 showed 91% similarity to strain JP2. Antimicrobial susceptibility testing indicated that SCQ11 was resistant to vancomycin. PCR analysis identified the presence of multiple virulence genes, including psaA, hyp, asal, sprE, nuc, cbh, srtA, hyl, scm, and agg. In vivo pathogenicity testing demonstrated that the vancomycin-resistant strain exhibited strong virulence in mice, with gross lesions observed in the liver, spleen, and intestines. Histopathological examination confirmed varying degrees of tissue damage, particularly in the liver and spleen. All three E. faecium isolates exhibited multidrug resistance, with one strain showing vancomycin resistance and harboring a high number of virulent genes. This strain demonstrated significant pathogenicity in vivo. These findings highlight the potential public health threat posed by multidrug-resistant E. faecium in livestock and provide essential data for regional prevention and control strategies. Full article
(This article belongs to the Section Veterinary Microbiology, Parasitology and Immunology)
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15 pages, 1789 KB  
Article
Genomic Epidemiology of Vancomycin-Resistant Enterococcus faecium Isolates with Full and Truncated vanA Operons from Russian Hospitals
by Anna Slavokhotova, Andrey Shelenkov, Yulia Mikhaylova, Lyudmila Petrova, Vitaly Gusarov, Mikhail Zamyatin and Vasiliy Akimkin
Antibiotics 2025, 14(9), 858; https://doi.org/10.3390/antibiotics14090858 - 25 Aug 2025
Viewed by 678
Abstract
Background: Vancomycin-resistant Enterococcus faecium (VREfm), particularly vanA-positive strains, represents a growing threat in hospital settings worldwide. These bacteria are able to survive under severe environmental conditions, including high temperatures and saline concentrations. High genome plasticity and advanced ability of inheriting antimicrobial [...] Read more.
Background: Vancomycin-resistant Enterococcus faecium (VREfm), particularly vanA-positive strains, represents a growing threat in hospital settings worldwide. These bacteria are able to survive under severe environmental conditions, including high temperatures and saline concentrations. High genome plasticity and advanced ability of inheriting antimicrobial resistance determinants defined the success of E. faecium as a hospital pathogen. Methods: This study presents the whole genomic characterization of vanA-positive VREfm isolates, analyzing 10 clinical isolates collected from three tertiary care hospitals in Moscow, Russia. Several typing approaches, including two MLST schemes and cgMLST profiles, were used to elucidate the relationship between the isolates. Phylogenetic analysis placed the isolates in context with global VREfm populations, demonstrating both local clonal expansion and possible international connections. Phenotypic and genomic antimicrobial resistance profiles were obtained, as well as data regarding the repertoire of virulence factors and plasmid content. Results: Whole genome sequencing revealed that all isolates belonged to the clinically significant CC17 lineage, specifically sequence types ST80 and ST552. Notably, two isolates possessed truncated Tn1546-type transposons lacking vanY and vanZ genes, representing a potentially emerging variant of the vanA operon in Russian clinical settings. A plasmid carrying a truncated vanA operon was reconstructed using long-read sequencing. Conclusions: The study highlights the utility of genomic investigation for tracking resistance mechanisms and strain dissemination, providing crucial baseline data for epidemiological surveillance of infections caused by VREfm in Russia. These findings emphasize the need for continued genomic monitoring to understand the evolution and spread of antimicrobial resistance in clinically important enterococcal lineages. Full article
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30 pages, 1627 KB  
Review
Linezolid in the Focus of Antimicrobial Resistance of Enterococcus Species: A Global Overview of Genomic Studies
by Slavil Peykov, Boris Kirov and Tanya Strateva
Int. J. Mol. Sci. 2025, 26(17), 8207; https://doi.org/10.3390/ijms26178207 - 24 Aug 2025
Viewed by 1814
Abstract
Linezolid (LNZ) is a synthetic oxazolidinone antibiotic that inhibits bacterial protein synthesis through binding to ribosomal RNA, also preventing the assembly of the initiation complex during translation. It is one of the last-line therapeutic options for serious infections caused by problematic Gram-positive pathogens, [...] Read more.
Linezolid (LNZ) is a synthetic oxazolidinone antibiotic that inhibits bacterial protein synthesis through binding to ribosomal RNA, also preventing the assembly of the initiation complex during translation. It is one of the last-line therapeutic options for serious infections caused by problematic Gram-positive pathogens, including vancomycin-resistant and multidrug-resistant Enterococcus species. Data from recent large-scale studies show a 2.5-fold increase in the prevalence of clinical LNZ-resistant enterococci (LRE) over the past decade with a global detection rate of 1.1% for LNZ-resistant E. faecium (LREfm) and 2.2% for LNZ-resistant E. faecalis (LREfs). Most reported cases have originated from China, followed by South Korea and the United States. LREfm typically belongs to the high-risk clonal complex 17, whereas LREfs demonstrates a heterogeneous population structure. Mutations in the 23S rRNA and ribosomal proteins, as well as acquired resistance genes such as cfr, optrA, and poxtA are involved in the development of LNZ resistance among enterococci. Whole-genome sequencing (WGS) has been recognized as a gold standard for identifying the underlying molecular mechanisms. It exposes that numerous LRE isolates possess multiple LNZ resistance determinants and mutations, further complicating the treatment strategies. The present review article summarizes all known mutational and non-mutational LNZ resistance mechanisms and presents a global overview of WGS-based studies with emphasis on resistome analysis of clinical LREfs and LREfm isolates published in the literature during the period 2014–2025. Full article
(This article belongs to the Special Issue Drug Treatment for Bacterial Infections)
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15 pages, 680 KB  
Article
Does Bovine Raw Milk Represent a Potential Risk for Vancomycin-Resistant Enterococci (VRE) Transmission to Humans?
by Elisa Massella, Simone Russo, Anita Filippi, Chiara Anna Garbarino, Matteo Ricchi, Patrizia Bassi, Elena Toschi, Camilla Torreggiani, Giovanni Pupillo, Gianluca Rugna, Valentina Carta, Cristina Bertasio, Andrea Di Cesare, Tomasa Sbaffi, Giulia Borgomaneiro and Andrea Luppi
Antibiotics 2025, 14(8), 814; https://doi.org/10.3390/antibiotics14080814 - 8 Aug 2025
Viewed by 662
Abstract
Background/Objectives: Vancomycin-resistant enterococci (VRE) are significant nosocomial pathogens worldwide, potentially transmitted by food-producing animals and related products. This study investigates the epidemiological role of bovine raw milk in the transmission of VRE to humans. Methods: Bulk milk samples were screened for [...] Read more.
Background/Objectives: Vancomycin-resistant enterococci (VRE) are significant nosocomial pathogens worldwide, potentially transmitted by food-producing animals and related products. This study investigates the epidemiological role of bovine raw milk in the transmission of VRE to humans. Methods: Bulk milk samples were screened for van gene presence using a multiplex PCR. Mastitogenic enterococci isolated from individual milk samples were tested for antimicrobial susceptibility using the broth microdilution method. Strains not susceptible to vancomycin were whole genome sequenced. Results: Overall, vanC genes were detected in 299/1026 (29.14%) bulk milk samples. Specifically, vanC1 was found in 204 samples (19.88%) and vanC2/3 in 57 samples (5.56%), with both detected simultaneously in 38 samples (3.70%). Clinically significant vanA and vanB genes were not identified. A total of 163 mastitogenic Enterococcus strains were isolated from individual milk samples. Eight different Enterococcus species were detected, with E. faecium (104/163, 63.80%) and E. faecalis (34/163, 20.86%) being the most common. Multidrug resistance was observed in 106/163 (65.03%) isolates. The most common resistance frequencies were to ciprofloxacin and erythromycin (102/163, 62.58% both), followed by quinupristin/dalfopristin (93/163, 57.06%), linezolid (65/163, 39.88%), tetracycline (58/163, 35.58%), daptomycin (46/163, 28.22%), chloramphenicol (33/163, 20.25%), ampicillin, tigecycline, and high-dosage gentamycin (8/163, 4.91% all). Resistance to teicoplanin was not observed. Two vancomycin non-susceptible strains were identified: one vanC2/3 E. casseliflavus and one vanC1 E. gallinarum. Whole genome sequencing confirmed the presence of the complete vanC gene cluster and several virulence genes in both strains. Conclusions: Our findings suggest that while raw milk is unlikely to be a source of vancomycin resistance genes of highest clinical importance (vanA or vanB), it may contribute to the spread of vanC enterococci, which are increasingly associated with human infections. Full article
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12 pages, 806 KB  
Proceeding Paper
Enterococcus faecalis Biofilm: A Clinical and Environmental Hazard
by Bindu Sadanandan and Kavyasree Marabanahalli Yogendraiah
Med. Sci. Forum 2025, 35(1), 5; https://doi.org/10.3390/msf2025035005 - 5 Aug 2025
Viewed by 1920
Abstract
This review explores the biofilm architecture and drug resistance of Enterococcus faecalis in clinical and environmental settings. The biofilm in E. faecalis is a heterogeneous, three-dimensional, mushroom-like or multilayered structure, characteristically forming diplococci or short chains interspersed with water channels for nutrient exchange [...] Read more.
This review explores the biofilm architecture and drug resistance of Enterococcus faecalis in clinical and environmental settings. The biofilm in E. faecalis is a heterogeneous, three-dimensional, mushroom-like or multilayered structure, characteristically forming diplococci or short chains interspersed with water channels for nutrient exchange and waste removal. Exopolysaccharides, proteins, lipids, and extracellular DNA create a protective matrix. Persister cells within the biofilm contribute to antibiotic resistance and survival. The heterogeneous architecture of the E. faecalis biofilm contains both dense clusters and loosely packed regions that vary in thickness, ranging from 10 to 100 µm, depending on the environmental conditions. The pathogenicity of the E. faecalis biofilm is mediated through complex interactions between genes and virulence factors such as DNA release, cytolysin, pili, secreted antigen A, and microbial surface components that recognize adhesive matrix molecules, often involving a key protein called enterococcal surface protein (Esp). Clinically, it is implicated in a range of nosocomial infections, including urinary tract infections, endocarditis, and surgical wound infections. The biofilm serves as a nidus for bacterial dissemination and as a reservoir for antimicrobial resistance. The effectiveness of first-line antibiotics (ampicillin, vancomycin, and aminoglycosides) is diminished due to reduced penetration, altered metabolism, increased tolerance, and intrinsic and acquired resistance. Alternative strategies for biofilm disruption, such as combination therapy (ampicillin with aminoglycosides), as well as newer approaches, including antimicrobial peptides, quorum-sensing inhibitors, and biofilm-disrupting agents (DNase or dispersin B), are also being explored to improve treatment outcomes. Environmentally, E. faecalis biofilms contribute to contamination in water systems, food production facilities, and healthcare environments. They persist in harsh conditions, facilitating the spread of multidrug-resistant strains and increasing the risk of transmission to humans and animals. Therefore, understanding the biofilm architecture and drug resistance is essential for developing effective strategies to mitigate their clinical and environmental impact. Full article
(This article belongs to the Proceedings of The 4th International Electronic Conference on Antibiotics)
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18 pages, 1942 KB  
Article
Surveillance and Characterization of Vancomycin-Resistant and Vancomycin-Variable Enterococci in a Hospital Setting
by Claudia Rotondo, Valentina Antonelli, Alberto Rossi, Silvia D’Arezzo, Marina Selleri, Michele Properzi, Silvia Turco, Giovanni Chillemi, Valentina Dimartino, Carolina Venditti, Sara Guerci, Paola Gallì, Carla Nisii, Alessia Arcangeli, Emanuela Caraffa, Stefania Cicalini and Carla Fontana
Antibiotics 2025, 14(8), 795; https://doi.org/10.3390/antibiotics14080795 - 4 Aug 2025
Viewed by 982
Abstract
Background/Objectives: Enterococci, particularly Enterococcus faecalis and Enterococcus faecium, are Gram-positive cocci that can cause severe infections in hospitalized patients. The rise of vancomycin-resistant enterococci (VRE) and vancomycin-variable enterococci (VVE) poses significant challenges in healthcare settings due to their resistance to multiple [...] Read more.
Background/Objectives: Enterococci, particularly Enterococcus faecalis and Enterococcus faecium, are Gram-positive cocci that can cause severe infections in hospitalized patients. The rise of vancomycin-resistant enterococci (VRE) and vancomycin-variable enterococci (VVE) poses significant challenges in healthcare settings due to their resistance to multiple antibiotics. Methods: We conducted a point prevalence survey (PPS) to assess the prevalence of VRE and VVE colonization in hospitalized patients. Rectal swabs were collected from 160 patients and analyzed using molecular assays (MAs) and culture. Whole-genome sequencing (WGS) and core-genome multilocus sequence typing (cgMLST) were performed to identify the genetic diversity. Results: Of the 160 rectal swabs collected, 54 (33.7%) tested positive for the vanA and/or vanB genes. Culture-based methods identified 47 positive samples (29.3%); of these, 44 isolates were identified as E. faecium and 3 as E. faecalis. Based on the resistance profiles, 35 isolates (74.5%) were classified as VRE, while 12 (25.5%) were classified as VVE. WGS and cgMLST analyses identified seven clusters of E. faecium, with sequence type (ST) 80 being the most prevalent. Various resistance genes and virulence factors were identified, and this study also highlighted intra- and inter-ward transmission of VRE strains. Conclusions: Our findings underscore the potential for virulence and resistance of both the VRE and VVE strains, and they highlight the importance of effective infection control measures to prevent their spread. VVE in particular should be carefully monitored as they often escape detection. Integrating molecular data with clinical information will hopefully enhance our ability to predict and prevent future VRE infections. Full article
(This article belongs to the Special Issue Hospital-Associated Infectious Diseases and Antibiotic Therapy)
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27 pages, 4093 KB  
Article
Antimicrobial Resistance in Commensal Bacteria from Large-Scale Chicken Flocks in the Dél-Alföld Region of Hungary
by Ádám Kerek, Ábel Szabó, Franciska Barnácz, Bence Csirmaz, László Kovács and Ákos Jerzsele
Vet. Sci. 2025, 12(8), 691; https://doi.org/10.3390/vetsci12080691 - 24 Jul 2025
Cited by 1 | Viewed by 1443
Abstract
Background: Antimicrobial resistance (AMR) is increasingly acknowledged as a critical global challenge, posing serious risks to human and animal health and potentially disrupting poultry production systems. Commensal bacteria such as Staphylococcus spp., Enterococcus spp., and Escherichia coli may serve as important reservoirs [...] Read more.
Background: Antimicrobial resistance (AMR) is increasingly acknowledged as a critical global challenge, posing serious risks to human and animal health and potentially disrupting poultry production systems. Commensal bacteria such as Staphylococcus spp., Enterococcus spp., and Escherichia coli may serve as important reservoirs and vectors of resistance genes. Objectives: This study aimed to assess the AMR profiles of bacterial strains isolated from industrial chicken farms in the Dél-Alföld region of Hungary, providing region-specific insights into resistance dynamics. Methods: A total of 145 isolates, including Staphylococcus spp., Enterococcus spp., and E. coli isolates, were subjected to minimum inhibitory concentration (MIC) testing against 15 antimicrobial agents, following Clinical and Laboratory Standards Institute (CLSI) guidelines. Advanced multivariate statistics, machine learning algorithms, and network-based approaches were employed to analyze resistance patterns and co-resistance associations. Results Multidrug resistance (MDR) was identified in 43.9% of Staphylococcus spp. isolates, 28.8% of Enterococcus spp. isolates, and 75.6% of E. coli isolates. High levels of resistance to florfenicol, enrofloxacin, and potentiated sulfonamides were observed, whereas susceptibility to critical antimicrobials such as imipenem and vancomycin remained largely preserved. Discussion: Our findings underscore the necessity of implementing region-specific AMR monitoring programs and strengthening multidisciplinary collaboration within the “One Health” framework with proper animal hygiene and biosecurity measures to limit the spread of antimicrobial resistance and protect both animal and human health. Full article
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15 pages, 636 KB  
Article
High Prevalence of Multidrug-Resistant Bacterial Colonization Among Patients and Healthcare Workers in a Rural Ethiopian Hospital
by Elena Hidalgo, Teresa Alvaredo-Carrillo, Josefina-Marina Gil-Belda, Clara Portela-Pino, Clara Bares-Moreno, Sara Jareño-Moreno, Paula de la Fuente, Lucía Platero and Ramón Pérez-Tanoira
Antibiotics 2025, 14(7), 717; https://doi.org/10.3390/antibiotics14070717 - 17 Jul 2025
Viewed by 949
Abstract
Background/Objectives: Multidrug-resistant (MDR) bacterial colonization poses a significant risk for subsequent infections, especially within hospital environments. Healthcare workers can inadvertently transmit these MDR bacteria to vulnerable patients, exacerbating the problem. This study aimed to determine the colonization rates of MDR bacteria among patients [...] Read more.
Background/Objectives: Multidrug-resistant (MDR) bacterial colonization poses a significant risk for subsequent infections, especially within hospital environments. Healthcare workers can inadvertently transmit these MDR bacteria to vulnerable patients, exacerbating the problem. This study aimed to determine the colonization rates of MDR bacteria among patients and healthcare workers in a rural Ethiopian hospital with limited resources. Methods: Between 26 May and 6 June 2024, nasal, rectal, vagino-rectal exudate, and stool samples were collected from patients (n = 78) and healthcare workers (n = 11) at Gambo General Hospital (Oromia Region, Ethiopia). Samples were cultured on chromogenic media selective for methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus spp. (VRE), and carbapenemase-producing Enterobacteriaceae (CPE). Bacterial identification was performed using MALDI-TOF mass spectrometry (Bruker), antimicrobial susceptibility testing using the MicroScan WalkAway system (Beckman Coulter), and genotypic characterization with the MDR Direct Flow Chip kit (Vitro). Results: MRSA nasal colonization was detected in 43.3% of patients (13/30; 95% CI: 27.4–60.8%) and 27.3% of healthcare workers (3/11; 95% CI: 6.0–61.0%) (p = 0.73). Rectal (or stool) colonization by MDR bacteria was significantly higher in pediatric patients (85.0%, 17/20; 95% CI: 62.1–96.8%) than in adults (14.3%, 4/28; 95% CI: 5.7–31.5%) (p < 0.001). Notably, a high proportion of pediatric patients harbored Escherichia coli strains co-producing NDM carbapenemase and CTX-M ESBL, and VRE strains were also predominantly isolated in this group. Conclusions: This study reveals a concerningly high prevalence of MRSA and MDR Enterobacteriaceae, especially among children at Gambo Hospital. The VRE prevalence was also substantially elevated compared to other studies. These findings underscore the urgent need for strengthened infection control measures and antimicrobial stewardship programs within the hospital setting. Full article
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11 pages, 1010 KB  
Case Report
A Puerperal Patient with Leukopenia During Vancomycin Administration: A Case Report and Review of the Literature
by Lidija Tulic, Katarina Ivanovic, Ivan Tulic, Svetlana Vrzic-Petronijevic, Stefan Ivanovic, Danijela Bratic and Miloš Petronijevic
Int. J. Mol. Sci. 2025, 26(14), 6584; https://doi.org/10.3390/ijms26146584 - 9 Jul 2025
Cited by 1 | Viewed by 858
Abstract
Antibiotic therapy is essential for managing bacterial infections, but rare yet serious hematological complications such as leukopenia and agranulocytosis may occur. These conditions, although uncommon, require timely diagnosis and intervention, particularly in vulnerable populations such as postpartum patients. This case report describes a [...] Read more.
Antibiotic therapy is essential for managing bacterial infections, but rare yet serious hematological complications such as leukopenia and agranulocytosis may occur. These conditions, although uncommon, require timely diagnosis and intervention, particularly in vulnerable populations such as postpartum patients. This case report describes a 31-year-old puerperal woman who developed agranulocytosis after extended antibiotic treatment for a presumed multidrug-resistant infection. Initially treated with ceftriaxone and metronidazole, her therapy was later escalated to include ciprofloxacin, amoxicillin–clavulanic acid, and vancomycin. Enterococcus spp. and Staphylococcus aureus were isolated from multiple sites, although no systemic infection was confirmed. Bone marrow findings were consistent with agranulocytosis in the recovery phase. Despite improvements in infection markers, her leukocyte count progressively declined, reaching a nadir of 1.61 × 109/L on the 19th day of therapy. Granulocyte-colony stimulating factor (G-CSF) therapy was initiated, resulting in hematological recovery. The patient was discharged with normal inflammatory markers and leukocyte counts. This case highlights the importance of diagnostic precision, rational antibiotic use, and timely hematologic assessment during prolonged antimicrobial treatment. Full article
(This article belongs to the Special Issue Drug Treatment for Bacterial Infections)
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16 pages, 301 KB  
Article
Molecular Characterization of Vancomycin-Resistant Enterococcus spp. from Clinical Samples and Identification of a Novel Sequence Type in Mexico
by Raúl Alejandro Atriano Briano, Nallely S. Badillo-Larios, Perla Niño-Moreno, Luis Fernando Pérez-González and Edgar A. Turrubiartes-Martínez
Antibiotics 2025, 14(7), 663; https://doi.org/10.3390/antibiotics14070663 - 30 Jun 2025
Viewed by 1002
Abstract
Background:Enterococcus spp. is the third leading cause of healthcare-associated infections in the American continent, often because of the virulence factors that protect the bacterium against host defenses and facilitate tissue attachment and genetic material exchange. In addition, vancomycin, considered a last-resort treatment, [...] Read more.
Background:Enterococcus spp. is the third leading cause of healthcare-associated infections in the American continent, often because of the virulence factors that protect the bacterium against host defenses and facilitate tissue attachment and genetic material exchange. In addition, vancomycin, considered a last-resort treatment, has shown reduced efficacy in Enterococcus spp. strains. However, the relationship between bacterial resistance and virulence factors remains unclear. This study intends to evaluate the prevalence of glycopeptide-resistant genotypes and virulence factors in Enterococcus spp. strains. Methods: Over six months, 159 Enterococcus spp. strains causing nosocomial infections were analyzed. Multiplex PCR was performed to identify species, glycopeptide-resistant genotypes, and 12 virulence factors. Results: The most abundant species identified were Enterococcus faecalis and E. faecium. Vancomycin resistance was observed in 10.7% of the isolates, and the vanA genotype was present in 47% of resistant samples. The main virulence factors detected were acm (54%), which is related to cell adhesion; gel E (66%), a metalloproteinase linked to tissue damage; and the sex pheromones cpd (64%) and ccf (84%), which are involved in horizontal gene transfer. A significant association was found between the prevalence of acm, ccf, and cpd in VRE isolates, indicating the potential dissemination of genes to emerging strains via horizontal gene transfer. In addition, a new E. faecium, which displayed five virulence factors and harbored the vanA sequence type, was identified and registered as ST2700. Conclusions:Enterococcus faecalis and E. faecium are clinically critical due to multidrug resistance and virulence factors like acm, which aids host colonization. Genes ccf and cpd promote resistance spread via horizontal transfer, while the emerging ST2700 strain requires urgent monitoring to curb its virulent, drug-resistant spread. Full article
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