Bacterial Pathogenesis and Antibiotic Resistance

A special issue of Pathogens (ISSN 2076-0817). This special issue belongs to the section "Bacterial Pathogens".

Deadline for manuscript submissions: 20 October 2025 | Viewed by 3757

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Guest Editor
Área de Microbiología, Departamento de Farmacia, Instituto de Ciencias Biomédicas, Facultad de Ciencias de la Salud, Universidad Cardenal Herrera—CEU, CEU Universities, Alfara del Patriarca, 46115 Valencia, Spain
Interests: antibiotic resistance; multidrug-resistant bacteria; clinical microbiology; clinical virology
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Special Issue Information

Dear Colleagues,

Bacterial pathogenesis and antibiotic resistance are critical topics in current biomedical research. In the context of growing concern about the efficacy of treatments, this Special Issue will address the molecular and cellular mechanisms underlying the ability of bacteria to cause disease, as well as the factors that facilitate the development and spread of antimicrobial resistance. Aspects such as the evolution of resistance, horizontal gene transfer, and innovative strategies to combat resistant infections through the development of alternative therapies or the design of next-generation antibiotics will be explored, with an emphasis on those that act on unconventional targets or through therapeutic synergies. In addition, the clinical implications and public health policies needed to address this growing threat will be discussed. This Special Issue invites researchers to present their original studies, reviews, and case analyses that provide a comprehensive and up-to-date view of these challenges and their possible solutions. 

Prof. Dr. María-Teresa Pérez-Gracia
Guest Editor

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Keywords

  • bacterial pathogenesis
  • antibiotic resistance
  • molecular mechanisms
  • therapeutic strategies
  • multidrug-resistant bacteria

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Published Papers (4 papers)

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Research

18 pages, 927 KB  
Article
In Vitro Investigation of the Antimicrobial Properties of Gerês Propolis in Bacteria Isolated from Companion Animals and Safety Profile Characterization Using the Galleria mellonella Model
by Rafael Rodrigues, Rui Almeida, Soraia C. V. Rodrigues, Joana Castro, Ricardo Oliveira, Nuno Mendes, Carina Almeida, Sónia Silva, Daniela Araújo and Cristina Almeida-Aguiar
Pathogens 2025, 14(8), 826; https://doi.org/10.3390/pathogens14080826 - 21 Aug 2025
Viewed by 466
Abstract
Propolis, also known as bee glue, is a natural resinous mixture produced by Western honeybees and has long been recognized for its potential therapeutic properties. Recent research has focused on its diverse bioactivities, particularly its antimicrobial effects against a broad spectrum of microorganisms, [...] Read more.
Propolis, also known as bee glue, is a natural resinous mixture produced by Western honeybees and has long been recognized for its potential therapeutic properties. Recent research has focused on its diverse bioactivities, particularly its antimicrobial effects against a broad spectrum of microorganisms, including human but also animal pathogens. However, further investigation is required to fully elucidate the pharmacological properties and potential toxicity of propolis to support its broader application. This study investigated the antimicrobial efficacy and safety of an ethanol extract of Portuguese propolis collected from the Gerês region (G23.EE). The antimicrobial activity was assessed in vitro against both Gram-positive and Gram-negative bacteria associated with infections in companion animals, using the agar dilution method. To evaluate potential toxicity, the extract was administered via injection and topical application in an in vivo Galleria mellonella larval model, with health parameters monitored over a 96 hours period. The in vitro results showed that G23.EE was more effective against Gram-positive bacteria, including Staphylococcus spp. (e.g., S. felis, S. hominis, S. simulans, and S. pseudintermedius; MIC = 0.5 mg/mL) and Enterococcus faecium (MIC = 1.5 mg/mL), than against Gram-negative bacteria, such as Escherichia coli and Klebsiella oxytoca (MIC > 8.0 mg/mL). No significant adverse effects were observed in G. mellonella larvae following injection or brushing with propolis extract concentrations up to 8.0 mg/mL. Overall, these findings suggest that Portuguese propolis from Gêres is a promising, safe, and effective natural antimicrobial agent for targeting Gram-positive bacterial infections in companion animals. Full article
(This article belongs to the Special Issue Bacterial Pathogenesis and Antibiotic Resistance)
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11 pages, 1164 KB  
Article
Optimizing Photosensitizer Delivery for Effective Photodynamic Inactivation of Klebsiella pneumoniae Under Lung Surfactant Conditions
by Fernanda Alves, Isabelle Almeida de Lima, Lorraine Gabriele Fiuza, Zoe A. Arnaut, Natalia Mayumi Inada and Vanderlei Salvador Bagnato
Pathogens 2025, 14(7), 618; https://doi.org/10.3390/pathogens14070618 - 21 Jun 2025
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Abstract
Klebsiella pneumoniae is a Gram-negative, encapsulated bacterium recognized by the World Health Organization (WHO) as a critical priority for new therapeutic strategies due to its increasing multidrug resistance (MDR). Antimicrobial photodynamic therapy (aPDT) has emerged as a promising alternative to antibiotics, exhibiting a [...] Read more.
Klebsiella pneumoniae is a Gram-negative, encapsulated bacterium recognized by the World Health Organization (WHO) as a critical priority for new therapeutic strategies due to its increasing multidrug resistance (MDR). Antimicrobial photodynamic therapy (aPDT) has emerged as a promising alternative to antibiotics, exhibiting a broad spectrum of action and multiple molecular targets, and has been proposed for the treatment of clinically relevant infections such as pneumonia. However, despite excellent in vitro photodynamic inactivation outcomes, the success of in vivo therapy still faces challenges, particularly due to the presence of lung surfactant (LS) in the alveoli. LS entraps photosensitizers, preventing these molecules from reaching microbial targets. This study investigated the potential of indocyanine green (ICG) in combination with the biocompatible polymer Gantrez™ AN-139 for the photoinactivation of K. pneumoniae. Initial in vitro experiments demonstrated that aPDT with ICG alone is effective against K. pneumoniae in a concentration- and light dose-dependent manner, achieving total eradication at 75 µg/mL of ICG and 150 J/cm2 of 808 nm light. When aPDT was performed with similar parameters in the presence of LS, no bacterial killing was observed. However, a significant synergistic effect was observed when ICG (25 µg/mL) was combined with a low concentration of Gantrez™ AN-139 (0.5% m/v) in the presence of dipalmitoylphosphatidylcholine (DPPC), the main component of LS. This formulation resulted in a substantial reduction (3.6 log10) in K. pneumoniae viability. These findings highlight the potential of Gantrez™ AN-139 as an efficient carrier to enhance the efficacy of ICG-mediated aPDT against K. pneumoniae, even in the presence of lung surfactant, a necessary step before the in vivo experiments. Full article
(This article belongs to the Special Issue Bacterial Pathogenesis and Antibiotic Resistance)
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8 pages, 4134 KB  
Communication
Genomic and Virulence Characteristics of Brucella intermedia Isolated from Hospital Wastewater in Ghana
by Runa Furuya, Satomi Takei, Yoko Tabe, Anthony Ablordey and Ryoichi Saito
Pathogens 2025, 14(6), 522; https://doi.org/10.3390/pathogens14060522 - 23 May 2025
Viewed by 1008
Abstract
Brucella intermedia, a gram-negative, non-lactose-fermenting, aerobic, rod-shaped bacterium, is found in environmental sources (e.g., soil and water). In 2020, Ochrobactrum was reclassified as Brucella. We conducted a genomic analysis of B. intermedia from hospital wastewater samples in western Ghana. A hybrid [...] Read more.
Brucella intermedia, a gram-negative, non-lactose-fermenting, aerobic, rod-shaped bacterium, is found in environmental sources (e.g., soil and water). In 2020, Ochrobactrum was reclassified as Brucella. We conducted a genomic analysis of B. intermedia from hospital wastewater samples in western Ghana. A hybrid genome assembly was constructed integrating short-read data from DNA Nanoball sequencing with long-read sequences generated by Oxford Nanopore MinION technology. Identification and antimicrobial susceptibility profiles were determined using MicroScan autoSCAN-4 based on Clinical and Laboratory Standard Institute documents. ResFinder and CARD Resistance Gene Identifier (RGI) were used to identify antimicrobial resistance (AMR) genes, and BLAST and VFDB datasets were used to identify virulence factor genes. The complete genome had two chromosomes, no plasmid, and a high average nucleotide identity value (98.05%) with B. intermedia. Resistance to trimethoprim-sulfamethoxazole was revealed, the first report in this species. CARD RGI revealed the presence of AMR genes, including ANT(9)-Ic and adeF. Local BLAST analysis revealed Cgs, a B. melitensis virulence factor. B. intermedia is an opportunistic human pathogen clinically isolated several times, suggesting the importance of accurately identifying multidrug resistance. B. intermedia may possess virulence factors similar to those of B. melitensis. Further study is needed to fully elucidate its pathogenesis. Full article
(This article belongs to the Special Issue Bacterial Pathogenesis and Antibiotic Resistance)
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11 pages, 545 KB  
Article
Prevalence and Antimicrobial Susceptibility of Salmonella in Retail Meat Collected from Different Markets in Sichuan, China
by Hang Zeng, Donghai Yang, Nanxi Huang, Yonglin Li, Jiazhen Chen, Zhongjia Yu, Jie Tang and Zhenju Jiang
Pathogens 2025, 14(3), 222; https://doi.org/10.3390/pathogens14030222 - 25 Feb 2025
Cited by 1 | Viewed by 773
Abstract
Salmonella is one of the most significant zoonotic and foodborne pathogens, and it is the leading cause of bacterial diarrhea. In this study, 156 retail meat samples were collected from three supermarkets and one local wet market in Sichuan, China, including 96 chicken [...] Read more.
Salmonella is one of the most significant zoonotic and foodborne pathogens, and it is the leading cause of bacterial diarrhea. In this study, 156 retail meat samples were collected from three supermarkets and one local wet market in Sichuan, China, including 96 chicken samples and 60 pork samples. The prevalence of Salmonella in these samples was analyzed, and 91 samples (58.33%) tested positive, with 60 (62.5%) positive chicken samples and 31 (51.67%) positive pork samples. From these positive samples, 190 Salmonella isolates were confirmed by double PCR. Subsequent serotyping identified nine serovars, with the predominant ones being S. London (58.94%), S. Typhimurium (12.58%), and S. Enteritidis (10.60%). Antibiotic susceptibility test revealed that 168 isolates (88.42%) were resistant to at least one antibiotic, and 150 isolates (78.95%) were resistant to three or more antibiotics. The highest resistance rates were observed for ampicillin (83.16%), followed by tetracycline (76.31%) and trimethoprim/sulfamethoxazole (67.37%). In the disinfectant susceptibility test, Salmonella isolates exhibited higher resistance rates to benzalkonium bromide (100%) and benzalkonium chloride (97.37%), while showing a lower resistance rate to potassium monopersulfate triple salt (33.6%). These findings highlight the high prevalence of Salmonella and its significant resistance to antibiotics and disinfectants, indicating that effective measures must be implemented to ensure the microbiological safety of retail meat. Full article
(This article belongs to the Special Issue Bacterial Pathogenesis and Antibiotic Resistance)
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