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43 pages, 988 KB  
Review
Clinically Significant Carbapenemases in Gram-Negative Pathogens: Molecular Diversity and Advances in β-Lactamase Inhibitor Therapy
by Jessi M. Grossman and Dorothea K. Thompson
Antibiotics 2026, 15(4), 413; https://doi.org/10.3390/antibiotics15040413 - 18 Apr 2026
Viewed by 161
Abstract
Carbapenems comprise a class of β-lactam antibiotics with broad-spectrum hydrolytic activity and are often reserved as last-line agents for the treatment of serious multidrug-resistant (MDR) bacterial infections. Clinically important nosocomial MDR Gram-negative bacteria (GNB) include Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter [...] Read more.
Carbapenems comprise a class of β-lactam antibiotics with broad-spectrum hydrolytic activity and are often reserved as last-line agents for the treatment of serious multidrug-resistant (MDR) bacterial infections. Clinically important nosocomial MDR Gram-negative bacteria (GNB) include Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii. Carbapenem resistance among these organisms is predominantly mediated by the production of β-lactamases called carbapenemases, such as K. pneumoniae carbapenemase (KPC), New Delhi metallo-β-lactamase (NDM), imipenemase (IMP), Verona integron-encoded metallo-β-lactamase (VIM), and selected oxacillinase (OXA)-type carbapenemases. These enzymes degrade carbapenems, significantly compromising their clinical efficacy. To address escalating antimicrobial resistance, novel next-generation β-lactamase inhibitors (BLIs), partnered with established β-lactams (BLs), have been approved or are currently under development to inhibit carbapenemase activity. The present narrative review aims to synthesize the most current information on the major carbapenemases and discusses recently approved and investigational BL/BLI combination therapies in terms of their mechanisms of action, spectrum of activity, gaps in coverage, and available clinical and in vitro evidence. Development of resistance to novel BL/BLI combinations is also examined. Comparative analysis of inhibitory spectra and microbiological coverage indicates a continued need for metallo-β-lactamase inhibitors with direct pan-inhibitory activity, pathogen-specific BL/BLI regimens for carbapenem-resistant A. baumannii, and carbapenemase-targeted agents effective in the context of non-enzymatic resistance mechanisms. Treatment-emergent resistance to novel BL/BLIs and limitations in activity profiles underscore the critical need for continued innovation in pipeline development, vigilant global and local surveillance of carbapenemase epidemiology, and robust antimicrobial stewardship strategies to aid in preserving the efficacy of the antibacterial drug armamentarium. Full article
(This article belongs to the Section Novel Antimicrobial Agents)
22 pages, 6666 KB  
Article
Integrated Phenotypic, Proteomic (MALDI-TOF MS), and Genomic (WGS) Investigation of a Prolonged Hospital Outbreak of Pseudomonas aeruginosa with High Biofilm-Forming Capacity
by Sandra Pamela Cangui-Panchi, Danny Santiago Cangui-Panchi, Verónica E. Palacios, Erika Becerra, Ana L. Santamaría, Diana Muñoz, Jorge Reyes-Chacón, António Machado and Daniel Garzon-Chavez
Antibiotics 2026, 15(3), 257; https://doi.org/10.3390/antibiotics15030257 - 2 Mar 2026
Viewed by 909
Abstract
Background/Objectives: Hospital outbreaks of Pseudomonas aeruginosa are difficult to control due to the pathogen’s extensive repertoire, including its ability to form biofilms, adapt and persist in diverse environments, and develop multidrug resistance, all of which contribute to prolonged outbreaks. This study integrates [...] Read more.
Background/Objectives: Hospital outbreaks of Pseudomonas aeruginosa are difficult to control due to the pathogen’s extensive repertoire, including its ability to form biofilms, adapt and persist in diverse environments, and develop multidrug resistance, all of which contribute to prolonged outbreaks. This study integrates the phenotypic, proteomic, and genomic characterization of a nosocomial outbreak comprising 38 clinical isolates and one environmental isolate recovered from the intensive care unit (ICU) of Hospital IESS Quito Sur. Methods: Clinical data were collected, antimicrobial susceptibility was assessed by minimum inhibitory concentration (MIC), carbapenemase genes were detected by multiple PCR and immunochromatographic assays, and the biofilm formation index (BFI) was determined. In addition, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was used for species identification and clustering based on spectral similarity. Twelve representative isolates underwent whole genome sequencing (WGS) to characterize the resistome and virulome and to compare phylogenetic relationships with proteomic clustering defined by MALDI Biotyper Compass Explorer software. Results: All isolates were identified as P. aeruginosa, and phenotypic antimicrobial susceptibility classified most isolates as multidrug resistant, including 32 CRPA strains. The blaVIM gene was detected in 22 isolates, while BFI analysis showed that all isolates formed moderate to strong biofilms. Genomic analysis revealed that most isolates belonged to ST111 and ST253, and both conserved and heterogeneous resistome and virulome profiles, with a broad distribution of determinants related to biofilm formation, stress tolerance, and persistence. Comparison between MALDI-TOF MS and WGS showed predominant concordance in clustering, mainly within subclusters but disagreement at the cluster level. Conclusions: The detection of carbapenemases, biofilm-forming ability, and virulence determinants associated with prolonged persistence highlights the need for integrated molecular tools, such as MALDI-TOF MS with MALDI Biotyper Compass Explorer software, to support epidemiological surveillance and to inform strategies aimed at mitigating prolonged hospital outbreaks caused by P. aeruginosa. Full article
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15 pages, 956 KB  
Article
Genomic Insights into Carbapenem-Resistant Pseudomonas aeruginosa (CRPA): Resistome and Virulome Analysis Beyond Carbapenemases
by Marta Pantanella, Grazia Pavia, Nadia Marascio, Chiara Mazzei, Simona Gigliotti, Francesca Serapide, Alessandro Russo, Giovanni Matera and Angela Quirino
J. Clin. Med. 2026, 15(5), 1683; https://doi.org/10.3390/jcm15051683 - 24 Feb 2026
Viewed by 471
Abstract
Background: Carbapenem-resistant Pseudomonas aeruginosa (CRPA) has been added to the World Health Organization’s list as a high-priority pathogen for which new antibiotics are urgently needed. Herein, we investigated the association between resistance/virulence genes and high-risk CRPA clinical isolates by whole genome sequencing (WGS). [...] Read more.
Background: Carbapenem-resistant Pseudomonas aeruginosa (CRPA) has been added to the World Health Organization’s list as a high-priority pathogen for which new antibiotics are urgently needed. Herein, we investigated the association between resistance/virulence genes and high-risk CRPA clinical isolates by whole genome sequencing (WGS). Methods: Between 2019 and 2025, twenty-six CRPA strains from patients hospitalized in the “Renato Dulbecco” University Hospital were characterized. WGS analysis was performed using the next generation sequencing (NGS) technique. Multi-locus sequence typing (MLST) prediction was performed. Antibiotic resistance genes were detected using Antibiotic Resistance Gene-ANNOTation, Comprehensive Antibiotic Resistance Database, and ResFinder. Virulence genes were identified by the Virulence Factor Database. Results: The MLST analysis detected 14 different sequence types (ST). The 26 strains exhibited the same resistome profile: aac(3)-Ic, aphA15, catB7, catB10, cmlA, blaCARB, blaVIM-1, and tetG genes. The genes encoding enzymes involved in resistance to chloramphenicol and beta-lactams were found in all isolates using the three databases. Biofilm formation genes, metalloproteinase, chemotaxis, fimbriae, and pyoverdine were identified in all strains. Genes of the type III secretion system exoS, exoT, exoU, and exoY were found in 46.15%, 84.61%, 53.84%, and 84.61% of the strains, respectively. Conclusions: The analysis of the 26 clinical isolates showed high clonal heterogeneity, with a predominance of ST235, a high-risk clone associated with multiple resistances. Interestingly, cefiderocol resistance was carried by 4/8 isolates belonging to the ST235 strain. The surveillance based on resistome and virulome analysis could monitor the dynamic evolution of high priorityhigh-priority pathogens to guide clinical treatment and to adapt healthcare control measures, limiting their spread in the near future. Full article
(This article belongs to the Section Infectious Diseases)
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18 pages, 2334 KB  
Article
Occurrence and Genomic Characterization of ESBL-, AmpC-, and Carbapenemase-Producing Escherichia coli and Klebsiella pneumoniae Isolated from Surface Water in Southern Italy, 2023–2024
by Gaia Nobili, Annachiara Cocomazzi, Maria Grazia Basanisi, Annita Maria Damato, Rosa Coppola, Maria Grazia Cariglia, Ilenia Franconieri, Antonella Stallone, Michelina Notarangelo, Tommaso Scirocco, Valeria Bortolaia and Giovanna La Salandra
Microorganisms 2026, 14(2), 508; https://doi.org/10.3390/microorganisms14020508 - 22 Feb 2026
Cited by 1 | Viewed by 1913
Abstract
Antimicrobial resistance (AMR) is recognised as a major global public health threat, with the environment increasingly acknowledged as a key reservoir and dissemination pathway for resistant bacteria and resistance genes. In this study, 148 surface water samples were collected between 2023 and 2024 [...] Read more.
Antimicrobial resistance (AMR) is recognised as a major global public health threat, with the environment increasingly acknowledged as a key reservoir and dissemination pathway for resistant bacteria and resistance genes. In this study, 148 surface water samples were collected between 2023 and 2024 from six rivers and three canals discharging wastewater into two lake waters in Southern Italy to assess the occurrence and genomic features of extended-spectrum β-lactamase (ESBL)-, AmpC-, and carbapenemase-producing Escherichia coli and Klebsiella pneumoniae. Relevant isolates were obtained using selective culturing, and tested for antimicrobial susceptibility by broth microdilution. Major β-lactam resistance genes were detected by real-time PCR. Whole-genome sequencing (WGS) was performed on presumptive carbapenemase-producing isolates. ESBL- and/or carbapenemase-producing Enterobacterales were detected in 67.6% of samples, yielding a total of 176 non-duplicate isolates. The most prevalent gene was blaCTX-M, detected in 79.3% of positive isolates (96/121), while carbapenemase genes were detected in 20.6% (25/121) of isolates, mainly blaOXA-48 and blaVIM. WGS analysis of carbapenemase PCR-positive isolates revealed occurrence of clinically relevant high-risk clones, such as K. pneumoniae ST512/ST307 carrying blaKPC-3 and E. coli ST10 harbouring blaOXA-244. These findings highlight a potential risk to public health and underscore the importance of integrating environmental compartments into One Health surveillance frameworks for AMR. Full article
(This article belongs to the Special Issue Antibiotic Resistance in Pathogenic Bacteria)
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16 pages, 497 KB  
Article
Phenotypic and Molecular Characterization of Carbapenem-Resistant Escherichia coli Isolated from Retail Meats in Hat Yai, Thailand
by Arnon Chukamnerd, Woralop Modleahman, Pattamarat Rattanachuay, Rattanaruji Pomwised and Pharanai Sukhumungoon
Bacteria 2026, 5(1), 10; https://doi.org/10.3390/bacteria5010010 - 9 Feb 2026
Viewed by 495
Abstract
(1) Background: Carbapenem-resistant Escherichia coli (CREC) is widespread and resistant to almost all available antimicrobial agents. In this study, we aimed to assess the phenotypic and molecular characteristics of CREC isolated from retail meats in Hat Yai, Songkhla, Thailand. (2) Methods: A total [...] Read more.
(1) Background: Carbapenem-resistant Escherichia coli (CREC) is widespread and resistant to almost all available antimicrobial agents. In this study, we aimed to assess the phenotypic and molecular characteristics of CREC isolated from retail meats in Hat Yai, Songkhla, Thailand. (2) Methods: A total of 155 retail meat samples were randomly collected, and 412 presumptive carbapenem-non-susceptible isolates were screened via culturing on imipenem-containing eosin methylene blue (EMB) agar. Susceptibility to imipenem and meropenem was tested using the disk diffusion method, and carbapenemase and virulence genes in CREC isolates were detected using PCR. Phylogenetic groups and genetic relatedness of carbapenemase-positive CREC isolates were analyzed using gene markers and BOX-PCR, respectively. (3) Results: The results revealed a high prevalence of presumptive carbapenem-non-susceptible E. coli (CNSEC) isolates in beef samples. Over 89% of the CNSEC isolates from all meat types were identified as CREC. Of these, only 4.8% of the isolates from beef samples were positive for the blaNDM gene, and one was also positive for the blaVIM gene. These isolates carried only the fimH gene as a virulence factor. The blaNDM-positive CREC isolates were classified in phylogenetic Group D. (4) Conclusions: Identifying antimicrobial-resistant pathogens, particularly CREC, in food-producing animals is critical due to potential risks to public health. Full article
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14 pages, 856 KB  
Article
Phenotypic and Whole-Genome Sequencing-Based Profiling of Antimicrobial Resistance and Virulence in Pseudomonas aeruginosa Isolated from Patients with Ventilator-Associated Pneumonia and Ventilator-Associated Tracheobronchitis in a Croatian Intensive Care Unit
by Marija Cavka, Marija Kvesic Ivankovic, Ana Maravic, Mia Dzelalija, Jelena Marinovic, Ivana Goic-Barisic, Marija Tonkic and Anita Novak
Genes 2026, 17(2), 130; https://doi.org/10.3390/genes17020130 - 26 Jan 2026
Cited by 1 | Viewed by 529
Abstract
Background/Objectives: Pseudomonas aeruginosa is one of the leading causes of ventilator-associated pneumonia (VAP) and ventilator-associated tracheobronchitis (VAT), with a worldwide spread of difficult-to-treat high-risk clones. This study aimed to investigate the virulence potential and to characterize phenotypic and genotypic antimicrobial resistance (AMR) in [...] Read more.
Background/Objectives: Pseudomonas aeruginosa is one of the leading causes of ventilator-associated pneumonia (VAP) and ventilator-associated tracheobronchitis (VAT), with a worldwide spread of difficult-to-treat high-risk clones. This study aimed to investigate the virulence potential and to characterize phenotypic and genotypic antimicrobial resistance (AMR) in P. aeruginosa causing VAP/VAT in the Intensive Care Unit (ICU), University Hospital of Split, Croatia. Methods: The study included P. aeruginosa isolates obtained from ICU patients who met the criteria for VAP or VAT, between January 2023 and January 2024. Isolates were identified using MALDI-TOF MS and tested for antimicrobial susceptibility (AST). A subset of phenotypically multidrug-resistant (MDR) isolates was further analyzed using whole-genome sequencing (WGS) and multilocus sequence typing. Results: A high rate of resistance was detected to ceftazidime (23.4%), imipenem (39.6%), and meropenem (43.8%). WGS confirmed the presence of multiple AMR genes, including the blaVIM-2 gene, whose genetic environment highlights a complex MDR locus integrating multiple AMR determinants and mobile genetic elements. All tested isolates possessed genes for class C (blaPDC34, blaPDC374 or blaPDC16) and class D (blaOXA-2, blaOXA-10 or blaOXA-50) β-lactamases, fosA, aph(3′)-IIb and crpP genes. Additionally, WGS analysis revealed the presence of numerous virulence genes including those for adherence (Type IV pili and Fap protein production), motility (such as flgF), biofilm formation (e.g., algE and mucE), quorum sensing (lasI, lasR, rhlI and rhlR), exotoxin (toxA and plcH) and exoenzyme activity (exoU, exoT, exoS, exoY, pcrV, hcp1 and lasA). The isolates belonged to four different sequence types: ST235, ST446, the high-risk ST253 and the widely distributed ST395. Phylogenomic comparison demonstrated that the isolates from this study do not originate from a single clonal source, but instead represent multiple globally distributed high-risk P. aeruginosa lineages introduced into the clinical setting. Conclusions: Due to the emergence of high-risk clones with broad AMR and strong virulence potential, ineffectiveness of standard empirical therapy may be anticipated, highlighting the urgent need for new therapeutic approaches (including those targeting major virulence factors). Full article
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18 pages, 2151 KB  
Article
Silent Waterborne Carriers of Carbapenem-Resistant Gram-Negative Bacilli and Antimicrobial Resistance Genes in Rio de Janeiro’s Aquatic Ecosystems
by Laura Brandão Martins, Marcos Tavares Carneiro, Kéren Vieira-Alcântara, Thiago Pavoni Gomes Chagas and Viviane Zahner
Antibiotics 2026, 15(2), 115; https://doi.org/10.3390/antibiotics15020115 - 23 Jan 2026
Viewed by 696
Abstract
Background/Objectives: Water pollution caused by human activities disrupts ecosystems and promotes the spread of antimicrobial resistance genes (ARGs), posing a public health threat. This study investigated the presence of resistant Gram-negative bacteria and resistance genes in water from two sites occasionally exposed [...] Read more.
Background/Objectives: Water pollution caused by human activities disrupts ecosystems and promotes the spread of antimicrobial resistance genes (ARGs), posing a public health threat. This study investigated the presence of resistant Gram-negative bacteria and resistance genes in water from two sites occasionally exposed to domestic and hospital effluents, the Carioca River (CR) and Rodrigo de Freitas Lagoon (RFL), both used for recreation. Methods: Physicochemical parameters and coliform levels were measured. Bacterial isolates were identified by Matrix-Assisted Laser Desorption Ionization–Time-of-Flight Mass Spectrometry (MALDI-TOF MS) and tested for antimicrobial susceptibility using disk diffusion. The Minimum Inhibitory Concentration (MIC) was determined using the E-test® and broth microdilution methods. PCR was used to detect carbapenem resistance and other ARGs from the DNA of bacterial isolates obtained from water samples. Results: CR presented signs of environmental degradation, with low dissolved oxygen and high coliform counts. One Citrobacter braakii isolate showed resistance to all tested antimicrobials, raising concern for untreatable infections. Carbapenem-resistant isolates accounted for 49.4% of the total, harboring blaKPC (20%), blaTEM (5%), blaVIM (5%), and blaSPM (5%). The intl1 gene was found in 10% of isolates, indicating potential horizontal gene transfer. Conclusions: The findings from a one-day sampling reveal the presence of multidrug-resistant bacteria that carry antimicrobial resistance genes in polluted aquatic systems. These highlight the connection between water contamination and antimicrobial resistance. The evidence underscores the urgent need for environmental monitoring and effective management strategies to reduce public health risks. Full article
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14 pages, 1400 KB  
Article
Molecular Epidemiology of Carbapenem-Resistant Pseudomonas aeruginosa Before the COVID-19 Pandemic: Resistance Profiles and Clonality in a Tertiary-Care Hospital
by Raúl Eduardo Loredo-Puerta, Perla Niño-Moreno, Raúl Alejandro Atriano-Briano, Katy Lizbeth Martínez-Alaniz, Nubia Baltazar-Benitez, Luis Fernando Pérez-González, Mónica Lucía Acebo-Martínez, Adriana Berenice Rousset-Román and Edgar A. Turrubiartes-Martínez
Antibiotics 2026, 15(1), 102; https://doi.org/10.3390/antibiotics15010102 - 20 Jan 2026
Cited by 1 | Viewed by 870
Abstract
Background/Objectives: Pseudomonas aeruginosa is an opportunistic pathogen frequently implicated in healthcare-associated infections, particularly ventilator-associated pneumonia and other device-related infections. The global emergence of carbapenem-resistant P. aeruginosa (CRPA) represents a major clinical challenge due to its limited therapeutic options and high mortality rates. [...] Read more.
Background/Objectives: Pseudomonas aeruginosa is an opportunistic pathogen frequently implicated in healthcare-associated infections, particularly ventilator-associated pneumonia and other device-related infections. The global emergence of carbapenem-resistant P. aeruginosa (CRPA) represents a major clinical challenge due to its limited therapeutic options and high mortality rates. Methods: Relevant clinical data were obtained from medical records. Isolates were identified via 16S PCR, and antimicrobial susceptibility testing was performed using the Vitek2 Compact system following CLSI guidelines. Carbapenemase genes (blaGES, blaKPC, blaIMP, blaNDM, blaVIM) were detected via PCR. Clonal relationships were determined via RAPD-PCR, and some sequence types were assigned according to the global P. aeruginosa MLST database. Results: In this study, 40 non-duplicate CRPA isolates were collected from 35 patients in a tertiary-care hospital in Mexico. Most isolates originated from adult patients, predominantly from tracheal aspirates (32.5%) and urine cultures (25.0%). Mechanical ventilation was the most common invasive device associated with infection, and the overall mortality rate reached 14.3%. Antimicrobial susceptibility testing showed that 95% of isolates exhibited a multidrug-resistant phenotype, with high resistance rates to ciprofloxacin (70.0%) and β-lactams. Carbapenemase genes were detected in 55% of isolates, mainly blaIMP, blaGES, and blaVIM, either alone or in combination. Notably, this is the first report of ST309 (blaIMP), ST411 (blaGES + blaIMP), and ST167 (blaGESblaVIM) carrying carbapenemase genes in Mexico. Conclusions: These findings highlight the persistence and genetic diversity of CRPA circulating in hospital settings and emphasize the urgent need for strengthened genomic surveillance and infection control programs to prevent the spread of these high-risk multidrug-resistant clones. Full article
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15 pages, 1984 KB  
Article
Genetic Determinants Linked to MDR/XDR in Pseudomonas aeruginosa Strains from a Mexican Tertiary Hospital
by Liliana Nicolas-Sayago, Miguel Ángel Loyola-Cruz, Yesseny Vásquez-Martínez, Marcelo Cortez-San Martín, Laura Margarita Márquez-Valdelamar, Clemente Cruz-Cruz, Emilio Mariano Durán-Manuel, Mireya Ruíz-Valdés, Claudia Camelia Calzada-Mendoza, Araceli Rojas-Bernabé, María Concepción Tamayo-Ordóñez, Yahaira de Jesús Tamayo-Ordóñez, Julio César Castañeda-Ortega, Briceida López-Martínez, Benito Hernández-Castellanos, Daniela Moreno-Torres, Graciela Castro-Escarpulli and Juan Manuel Bello-López
Pathogens 2026, 15(1), 100; https://doi.org/10.3390/pathogens15010100 - 17 Jan 2026
Cited by 1 | Viewed by 876
Abstract
Background: Pseudomonas aeruginosa is one of the leading agents causing healthcare-associated infections (HAIs) due to its intrinsic resistance, its capacity to acquire resistance mechanisms, and its persistence in hospital environments. In Mexico, it ranks among the most frequently reported pathogens in national surveillance [...] Read more.
Background: Pseudomonas aeruginosa is one of the leading agents causing healthcare-associated infections (HAIs) due to its intrinsic resistance, its capacity to acquire resistance mechanisms, and its persistence in hospital environments. In Mexico, it ranks among the most frequently reported pathogens in national surveillance systems. The aim of this study was to characterize antimicrobial resistance profiles and the genetic determinants associated with MDR/XDR phenotypes in P. aeruginosa strains from HAIs at Hospital Juárez de México (HJM). Methods: Sixty-three strains from patients with HAIs were analyzed. Identification was confirmed by 16S rRNA gene sequencing. Antimicrobial susceptibility testing followed CLSI guidelines. MDR/XDR phenotypes were classified according to the Latin American consensus for categorizing MDR, XDR, and PDR pathogens. Screening for resistance mechanisms was carried out by PCR for the main β-lactamases circulating at HJM. Finally, mutations in the oprD gene were detected in imipenem-resistant isolates through amino acid sequence alignment. Results: Resistant phenotypes allowed the identification of MDR and XDR profiles. Only the metallo-β-lactamase blaVIM was detected. Analysis of oprD porin sequences revealed recurrent mutations (S103T, T115K, L170F, G186P, and T189V) associated with imipenem resistance. Conclusions: In P. aeruginosa, the presence of blaVIM and structural alterations in OprD confirms the multifactorial nature of carbapenem resistance. These findings underscore the need to strengthen microbiological surveillance programs and antimicrobial stewardship strategies to mitigate the impact and spread of MDR/XDR isolates. Full article
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15 pages, 1622 KB  
Article
Seasonal Surveillance of Urban Water Quality in Southern Brazil Reveals Persistent Carbapenem Resistance Genes Despite Compliance with Bacteriological Standards
by Laura Haleva, Tiane Martin de Moura, Luciana Costa Teixeira, Horst Mitteregger Júnior, Evgeni Evgeniev Gabev, Adriana Ambrosini da Silveira and Fabrício Souza Campos
Microbiol. Res. 2026, 17(1), 21; https://doi.org/10.3390/microbiolres17010021 - 15 Jan 2026
Viewed by 696
Abstract
Quality control of drinking water is essential for safeguarding public health, particularly in densely populated urban environments. Environmental microbiological monitoring can complement conventional surveillance by providing deeper insights into the dissemination of pathogens and antimicrobial resistance genes within aquatic systems. In this study, [...] Read more.
Quality control of drinking water is essential for safeguarding public health, particularly in densely populated urban environments. Environmental microbiological monitoring can complement conventional surveillance by providing deeper insights into the dissemination of pathogens and antimicrobial resistance genes within aquatic systems. In this study, we assessed the quality of wastewater and treated water from two urban water supply systems, representing the southern and northern regions of Porto Alegre, Rio Grande do Sul, Brazil, across four climatic seasons between 2024 and 2025. Fifteen water samples were analyzed, including raw water from Guaíba Lake and treated water collected from public distribution points. The Water Quality Index was calculated, microbiological indicators were quantified, and carbapenem resistance genes were detected using molecular assays. Most treated water samples complied with established bacteriological standards; however, the blaOXA-48-like gene was recurrently detected in both wastewater and treated water. No resistance genes were identified during the summer, whereas the blaVIM gene was detected exclusively in spring samples. The presence of carbapenem resistance genes in the absence of cultivable coliforms suggests the persistence of extracellular DNA or viable but non-culturable bacteria, highlighting limitations inherent to conventional microbiological monitoring. Integrating classical microbiological methods with molecular assays enables a more comprehensive assessment of water quality and strengthens evidence-based decision-making within a One Health framework. Full article
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16 pages, 1310 KB  
Article
Occurrence of Citrobacter spp.-Associated and Non-Associated Lesions in a Stranded Loggerhead Sea Turtle (Caretta caretta) from Italy
by Filippo Fratini, Rossana Schena, Sinem Arslan, Alessandro Beneforti, Ilaria Resci, Marco Salvadori, Annunziata Romano, Luisa De Martino and Francesca Paola Nocera
Pathogens 2026, 15(1), 56; https://doi.org/10.3390/pathogens15010056 - 6 Jan 2026
Viewed by 724
Abstract
The skin of turtles, particularly aquatic species, can harbor a diverse range of bacteria, including Citrobacter species, which are recognized as causative agents of Septicemic Cutaneous Ulcerative Disease. Consequently, turtles may act as reservoirs of pathogenic and multidrug-resistant bacteria, posing a potential public [...] Read more.
The skin of turtles, particularly aquatic species, can harbor a diverse range of bacteria, including Citrobacter species, which are recognized as causative agents of Septicemic Cutaneous Ulcerative Disease. Consequently, turtles may act as reservoirs of pathogenic and multidrug-resistant bacteria, posing a potential public health concern. This case-based study investigated the presence of Citrobacter spp. in a loggerhead sea turtle (Caretta caretta) housed at the Livorno Aquarium, Italy. Nine swabs were collected from skin lesions (plastron, carapace, nuchal mass), the oral cavity, and the cloaca. The isolated strains were identified by MALDI-TOF MS and tested for their susceptibility to 12 antimicrobials, belonging to eight antimicrobial classes, by the disc diffusion method. Isolates were investigated genotypically for extended-spectrum-β-lactamase (ESBL) blaCTX−M, blaTEM, blaSHV, blaPER, and metallo-β-lactamase (MBL) blaIMP, blaOXA−48, blaVIM, blaNDM, blaGES genes. Biofilm production ability was also evaluated. Fifteen Citrobacter spp. strains were recovered from the analyzed samples. Complete resistance was recorded for ampicillin, followed by high levels of resistance to imipenem, tetracycline and piperacillin-tazobactam. Worryingly, 86.7% were classified as multidrug-resistant. The most common ESBL-genotype combination was blaSHV and blaPER genes (60%), while the most frequently detected MBL gene was blaNDM (46.7%), followed by blaGES (40%). Most isolates were classified as weak biofilm producers (80%). The findings of this study demonstrate the presence of Citrobacter spp., an opportunistic pathogen, with a notable prevalence of multidrug-resistant strains carrying beta-lactamase-encoding genes, in a loggerhead sea turtle in Italy, across both lesioned and healthy anatomical sites. Full article
(This article belongs to the Special Issue Diagnosis, Immunopathogenesis and Control of Bacterial Infections)
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14 pages, 562 KB  
Article
Comparison of Commercial Lateral Flow Immunochromatography with Phenotypic and Genotypic Assays for the Detection of Carbapenemase-Producing Gram-Negative Bacteria at Tanta University Hospitals
by Marwa S. Taha, Basant Mostafa Gabr, Wafaa Abd Elaziz, Ahmed Mostafa Elgohary, Bsant S. Kasem, Reham M. Elkolaly, Hytham I. S. Elatrozy, Marwa N. Emam, Asmaa S. Essawy, Heba E. M. Sharaf Eldin, Rehab A. Mohamed, Mahmoud Z. Elkadeem, Sherif Abdelbaky and Mona Abd El-Aziz Gadallah
Microorganisms 2026, 14(1), 31; https://doi.org/10.3390/microorganisms14010031 - 22 Dec 2025
Viewed by 750
Abstract
It is crucial to identify Enterobacterales that produce carbapenemase to treat and manage hospital infections. The suggested techniques for their identification need a lengthy wait, technical knowledge, and training. Lateral flow immunoassays (LFIAs) provide a solution to these requirements. Thus, this study compared [...] Read more.
It is crucial to identify Enterobacterales that produce carbapenemase to treat and manage hospital infections. The suggested techniques for their identification need a lengthy wait, technical knowledge, and training. Lateral flow immunoassays (LFIAs) provide a solution to these requirements. Thus, this study compared LFIA with phenotypic and genotypic tests for carbapenemase-producing bacteria. Fifty clinical isolates of carbapenem-resistant superbugs were examined. KPC, VIM, NDM, IMP, and OXA-48-like enzymes were evaluated and compared with phenotypic tests and LFIA. Regarding the phenotypic characteristics, the mCIM was positive in 37/50 (74%), and the eCIM was positive in 21/50 (42%). Regarding using LFIA, 41 out of the total isolates (82%) gave a positive red line with one or more of the tested genes. The most frequently detected gene was blaNDM (27/50 (54%)), and the least detected one was blaIMP (14/50 (28%)), which was in accordance with the PCR results. While investigating the accuracy of LFIA vs. PCR, it was found that LFIA had 100% sensitivity in the detection of the blaNDM and blaOXA genes, with 85.2% and 91.4% specificity, respectively, while for the blaIMP, blaKPC, and blaVIM genes, the values were 91.7% and 92.1%, 94.1% and 90.9%, and 95.5% and 89.3%, respectively. The overall accuracy of LFIA ranged from 92 to 94%. Our comparison with molecular assays revealed remarkable agreement, so we propose that this test might be utilized as a supplementary tool. Full article
(This article belongs to the Special Issue Antimicrobial Testing (AMT), Third Edition)
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14 pages, 1352 KB  
Article
First Detection of Critical Carbapenemase Genes (NDM, OXA-48, VIM) in Avian Campylobacter spp. Isolates in Tunisia: A Zoonotic and Public Health Concern
by Manel Gharbi, Mohammed Abdo Saghir Abbas, Chadlia Hamdi, Safa Hamrouni and Abderrazak Maaroufi
Antibiotics 2025, 14(12), 1236; https://doi.org/10.3390/antibiotics14121236 - 8 Dec 2025
Cited by 1 | Viewed by 705
Abstract
Background/Objectives: The global emergence of carbapenem resistance is a major public health concern. Campylobacter jejuni and Campylobacter coli, key zoonotic agents causing human campylobacteriosis, are mainly isolated from poultry, their primary host. Their increasing resistance in animals and humans highlights the [...] Read more.
Background/Objectives: The global emergence of carbapenem resistance is a major public health concern. Campylobacter jejuni and Campylobacter coli, key zoonotic agents causing human campylobacteriosis, are mainly isolated from poultry, their primary host. Their increasing resistance in animals and humans highlights the risk of gene transfer. This study investigates the molecular mechanisms of carbapenem resistance in 287 avian Campylobacter spp. isolates from Tunisia within a One Health approach. Methods: Antibiotic susceptibility of 287 carbapenem-resistant isolates, including 147 C. jejuni and 140 C. coli, was determined according to CLSI. All isolates were screened by PCR for genes encoding the most reported carbapenemases, including VIM, IMP, NDM and OXA-48. Eleven multidrug-resistant (MDR)/carbapenem-resistant C. coli isolates were selected to determine their clonal lineage by Multilocus sequence typing (MLST). Results: All isolates were susceptible to imipenem, but resistance to meropenem and ertapenem were observed in 60.71% and 35.71% of C. coli isolates, respectively, versus 13.6% in C. jejuni for each antibiotic. The blaVIM, blaNDM and blaOXA-48 genes were detected in 15, 8, and 19 of the 20 C. jejuni isolates, respectively. However, for C. coli, 53, 12, and 15 isolates harbored blaVIM, blaNDM and blaOXA-48 genes, respectively. The eleven (MDR)/carbapenem-resistant C. coli isolates belonged to a unique ST sequence type ST13450. Conclusions: We report for the first time the emergence of blaVIM, blaNDM, and blaOXA-48 genes in Campylobacter spp. isolates of poultry origin highlighting possible horizontal transfer of these genes to pathogenic Gram-negative bacteria of the poultry’s microbiota. Full article
(This article belongs to the Special Issue Antibiotic Resistance in Bacterial Isolates of Animal Origin)
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27 pages, 4822 KB  
Article
Resistance Landscape and Clonal Dynamics of ESKAPE Pathogens in Bloodstream Infections: A Multicenter Study from Mexico
by María Dolores Alcántar-Curiel, Rayo Morfín-Otero, Ma Dolores Jarillo-Quijada, José Luis Fernández-Vázquez, Catalina Gayosso-Vázquez, María Luisa Hernández-Medel, Manuelita Zavala-Pineda, Miguel Ángel Morales-Gil, Mónica Osorio-Guzmán, María Angelina Quevedo-Ramos, Luis Fernando Pérez-González, Andrés Flores-Santos, Sergio Esparza-Ahumada, Rodrigo Escobedo-Sánchez, Roberto Rosales-Reyes, José Eduardo Toledano-Tableros, Silvia Giono-Cerezo, José Ignacio Santos-Preciado and Eduardo Rodríguez-Noriega
Pathogens 2025, 14(11), 1187; https://doi.org/10.3390/pathogens14111187 - 19 Nov 2025
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Abstract
Antimicrobial resistance in healthcare-associated infections represents one of the greatest threats to global health. The COVID-19 pandemic disrupted infection control and antimicrobial stewardship, potentially affecting the prevalence of pathogens and the development of resistance. This study aimed to investigate the prevalence, antimicrobial resistance, [...] Read more.
Antimicrobial resistance in healthcare-associated infections represents one of the greatest threats to global health. The COVID-19 pandemic disrupted infection control and antimicrobial stewardship, potentially affecting the prevalence of pathogens and the development of resistance. This study aimed to investigate the prevalence, antimicrobial resistance, and clonal dissemination of ESKAPE pathogens isolated from bloodstream infections during the second year of the COVID-19 pandemic in four tertiary-care hospitals in Mexico. A total of 926 isolates were analyzed: Staphylococcus aureus (22.4%), Klebsiella pneumoniae (22%), Acinetobacter baumannii (21.5%), Pseudomonas aeruginosa (12.5%), Enterobacter cloacae (9.4%), Enterococcus faecalis (8.4%), and Enterococcus faecium (3.8%). High rates of multidrug resistance were observed in A. baumannii (70.9% XDR) and K. pneumoniae (71% XDR plus MDR with 79% ESBL). P. aeruginosa and E. cloacae showed the highest susceptibility rates (53% and 48%, respectively) to all antimicrobials. The main β-lactamases involved in resistance were blaSHV, blaCTX-M, and blaTEM in K. pneumoniae, while the predominant carbapenemases were blaOXA-24, blaOXA-23 in A. baumannii, blaNDM in K. pneumoniae, and blaVIM in P. aeruginosa. Among Gram-positives, methicillin-resistant S. aureus accounted for 33.8% of isolates, and vancomycin resistance was higher in E. faecium (28%) than in E. faecalis (1.3%). Pulsed-field gel electrophoresis revealed endemic circulation of A. baumannii clones (Pulsotypes 1AC, 2AM), persistent for over a decade, and interhospital dissemination of S. aureus and K. pneumoniae clones. These findings underscore the epidemiological relevance of MDR ESKAPE pathogens during the COVID-19 pandemic and highlight the urgent need to optimize empirical therapy and maintain continuous genomic surveillance to enhance infection control in Mexican hospitals. Full article
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15 pages, 1865 KB  
Article
Molecular Epidemiological Surveillance of Carbapenem-Resistant Gram-Negative Bacteria in Southern Lebanon
by Anwar Al Souheil, Hadi Hussein, Ziad Jabbour, Sara Barada, Jose-Rita Gerges, Ghada Derbaj, Abdallah Kurdi, Hassan Jamil Kazma, Nour Nahouli, Ali Hasan Najem, Abdallah Medlej, Wael Zorkot, Rana El Hajj, Mahmoud I. Khalil, Ghassan M. Matar and Antoine Abou Fayad
Antibiotics 2025, 14(11), 1124; https://doi.org/10.3390/antibiotics14111124 - 7 Nov 2025
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Abstract
Introduction: Carbapenem-resistant Gram-negative bacteria (CR-GNB) are rapidly spreading pathogens that increase morbidity and mortality in hospital settings and significantly restrict available treatment options worldwide. The lack of molecular epidemiological data and the limited use of next-generation sequencing (NGS) in South Lebanon have hindered [...] Read more.
Introduction: Carbapenem-resistant Gram-negative bacteria (CR-GNB) are rapidly spreading pathogens that increase morbidity and mortality in hospital settings and significantly restrict available treatment options worldwide. The lack of molecular epidemiological data and the limited use of next-generation sequencing (NGS) in South Lebanon have hindered comprehensive surveillance efforts. This study represents the first molecular characterization of CR-GNB in this region. Methods: A total of 477 clinical Gram-negative bacterial isolates were collected from intensive care unit (ICU) patients admitted to various hospitals in South Lebanon in 2023. Of these, 131 CR-GNB were subjected to whole-genome sequencing using the Illumina MiSeq platform. K-mer-based species identification, multilocus sequence typing (MLST), antimicrobial resistance (AMR) gene profiling, and plasmid analysis were performed using multiple bioinformatic tools. Phylogenetic analysis was conducted using SaffronTree. Results: K-mer-based identification revealed that the predominant species among CR-GNB isolates were Pseudomonas spp. and Escherichia coli (26.7% each), followed by Klebsiella pneumoniae (19.8%), Acinetobacter baumannii (17.6%), Proteus mirabilis (4.6%), Enterobacter cloacae (2.3%), Achromobacter spp. (1.5%), and Citrobacter freundii (0.8%). Based on antimicrobial susceptibility testing, isolates were classified as follows: 0.8% as pan drug-resistant (PDR), 40.5% as extensively drug-resistant (XDR), and 52.7% as multidrug-resistant (MDR) and 6.1% as antimicrobial-resistant (AMR). All isolates harbored AMR genes, with the following distribution: 2% blaVIM, 5% blaNDM-1, 27% blaNDM-5, 65% blaOXA-type, and 1% blaDIM-1. Plasmid-associated AMR genes were detected in 58% of isolates; among these, 96% carried Inc-family plasmids, 57% Col plasmids, and 11% replication-associated elements (rep). Phylogenetic analysis demonstrated that certain isolates exhibited both hospital-specific and shared genetic profiles, indicating widespread dissemination across multiple healthcare facilities, as well as evidence of local emergence and ongoing transmission. Conclusions: The high prevalence of CR-GNB harboring resistance genes and plasmids underscores the urgent need for NGS-based genomic surveillance in South Lebanon. Implementing such strategies is essential for tracking resistance genes, identifying clonal outbreaks, and guiding effective infection control interventions to mitigate the spread of CR-GNB. Full article
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