Alahmar, A. J., N. M. Elhosseiny, R. R. Mahmoud, and A. S. Attia, "Transcriptional regulator NtrC modulates nitrogen assimilation, virulence, and the extracellular glutamine synthetase activity in Acinetobacter baumannii.", PloS one, vol. 21, issue 1, pp. e0341569, 2026. Abstract

Acinetobacter baumannii is a growing threat characterized by worrisome antibiotic resistance. A deeper understanding of its resistance and virulence mechanisms is essential for developing new and effective treatments. Herein, we explore the role of the two-component (NtrB-NtrC) signal transduction system and two distinct glutamine synthetases (GlnA-1 and GlnA-2) in the nitrogen assimilation, stress response, and virulence in A. baumannii. Under nitrogen-limited conditions, the ntrC mutant showed significantly defective growth kinetics when ammonium was the sole source of nitrogen, whereas the glnA2 mutant exhibited an obvious growth defect when putrescine was the sole source of nitrogen. Moreover, under nitrogen limitation, the glnA1 and glnA2 expression increased by approximately twofold and ninefold, respectively. An enzymatic activity assay demonstrated that the A. baumannii extracellular glutamine synthetase activity is dependent on the type II secretion system (T2SS), confirming our previous results from a T2SS secretome study. Interestingly, this activity is also regulated by NtrC. An infection model using Galleria mellonella revealed that the ntrC mutant was significantly less virulent than both the wild-type and glnA2 mutant strains. These results provide new insights into the nitrogen regulatory network and its contribution to the A. baumannii virulence, underscoring NtrC as a promising target for future antimicrobial strategies.

Alahmar, A. J., N. M. Elhosseiny, R. R. Mahmoud, and A. S. Attia, "Transcriptional regulator NtrC modulates nitrogen assimilation, virulence, and the extracellular glutamine synthetase activity in Acinetobacter baumannii.", PloS one, vol. 21, issue 1, pp. e0341569, 2026. Abstract

Acinetobacter baumannii is a growing threat characterized by worrisome antibiotic resistance. A deeper understanding of its resistance and virulence mechanisms is essential for developing new and effective treatments. Herein, we explore the role of the two-component (NtrB-NtrC) signal transduction system and two distinct glutamine synthetases (GlnA-1 and GlnA-2) in the nitrogen assimilation, stress response, and virulence in A. baumannii. Under nitrogen-limited conditions, the ntrC mutant showed significantly defective growth kinetics when ammonium was the sole source of nitrogen, whereas the glnA2 mutant exhibited an obvious growth defect when putrescine was the sole source of nitrogen. Moreover, under nitrogen limitation, the glnA1 and glnA2 expression increased by approximately twofold and ninefold, respectively. An enzymatic activity assay demonstrated that the A. baumannii extracellular glutamine synthetase activity is dependent on the type II secretion system (T2SS), confirming our previous results from a T2SS secretome study. Interestingly, this activity is also regulated by NtrC. An infection model using Galleria mellonella revealed that the ntrC mutant was significantly less virulent than both the wild-type and glnA2 mutant strains. These results provide new insights into the nitrogen regulatory network and its contribution to the A. baumannii virulence, underscoring NtrC as a promising target for future antimicrobial strategies.

Kamal, R. M., A. M. El-Halawany, M. S. Hifnawy, A. M. Otify, W. G. Fahmy, N. M. Elhosseiny, A. S. Attia, B. M. Eltanany, L. Pont, F. Benavente, et al., "Targeting Acinetobacter baumannii lipase by coniferous species through metabolomics supported approach.", Scientific reports, vol. 15, issue 1, pp. 32649, 2025. Abstract

The opportunistic pathogen Acinetobacter baumannii is a particularly problematic nosocomial threat worldwide, leading to high morbidity and mortality rates due to its multiple resistance mechanisms, including the production of lipolytic enzymes. Herein, the aerial parts of three coniferous plants, Pinus canariensis C. Sm. (PC), Cupressus lusitanica Mill. (CL), and Cupressus arizonica Greene. (CA), were extracted and fractionated. Among these, the CA extract followed by CL and then PC, exhibited the highest inhibition of bacterial lipase activity, with half-maximal inhibitory concentration (IC) values of 1117 ± 87, 1278 ± 62, and 1926 ± 104 µg/mL, respectively. The methylene chloride fractions of CA and CL extracts exhibited the highest inhibition of bacterial lipase activity, with IC (940 ± 25 µg/mL and 1103 ± 155 µg/mL), respectively. The metabolite profile of the three extracts, along with their most active fractions, were determined using liquid chromatography-quadrupole-time-of-flight tandem mass spectrometry (LC-QTOF-MS/MS). Interestingly, the metabolite profiles of CL extracts were established here for the first time. A total of 99 secondary metabolites from diverse classes were identified across all samples. Among these, four metabolites were isolated: 3,5-di-p-coumaroylquinic acid, epicatechin, cupressuflavone, and rutin. The biflavonoid cupressuflavone showed the lowest IC value (3812 ± 450 µg/mL). Additionally, partial least squares was applied to assess the key metabolites contributing to the differentiation of the studied bioactivity. Consequently, this study provides novel insights into the bioactivity potential of coniferous plants, demonstrating their value as a natural source of antivirulence agents against the A. baumannii lipase enzyme.

Abuelkhir, A. A., M. Omara, Y. I. Nagy, A. E. Gouda, A. S. Attia, A. S. Mayhoub, and M. Hagras, "Position switch of phenylthiazoles: novel compounds with promising anti-MRSA USA300 ", Medicinal Chemistry Research , vol. 33, pp. 1178–1194, 2024. position_switch_of_phenylthiazoles_novel_compound-final_version.pdf
Mahdally, N. H., A. E. M. Salih, R. A. El-Shiekh, A. M. Sayed, N. M. Elhosseiny, M. O. N. A. T. KASHEF, M. Yaseen, W. Mackay, A. E. M. Halawany, M. E. Rateb, et al., "Exploring the antimicrobial activity of Origanum majorana L. against the highly virulent multidrug-resistant Acinetobacter baumannii AB5075: UPLC-HRMS profiling with in vitro and in silico studies", Future Journal of Pharmaceutical Sciences , vol. 10, issue 1, pp. 71, 2024.
Abuelkhir, A. A., Y. I. Nagy, T. Gamal, A. M. Abdelhalim, A. S. Attia, A. S. Mayhoub, and M. M. Elsebaie, "Small Molecule Alkynyl-Phenylaminoguanidines: A New Weapon Against Multi-Drug Resistant Bacteria", ChemistrySelect, vol. 10, issue 4, pp. e202404320, 2025.
Rizk, S. S., D. M. Moustafa, S. A. Elbanna, H. T. Nour El-Din, and A. S. Attia, "Nanobodies in the fight against infectious diseases: repurposing nature's tiny weapons.", World Journal of Microbiology & Biotechnology, vol. 40, issue 7, pp. 209, 2024. Abstractnanobodies_final_version.pdf

Nanobodies are the smallest known antigen-binding molecules to date. Their small size, good tissue penetration, high stability and solubility, ease of expression, refolding ability, and negligible immunogenicity in the human body have granted them excellence over conventional antibodies. Those exceptional attributes of nanobodies make them promising candidates for various applications in biotechnology, medicine, protein engineering, structural biology, food, and agriculture. This review presents an overview of their structure, development methods, advantages, possible challenges, and applications with special emphasis on infectious diseases-related ones. A showcase of how nanobodies can be harnessed for applications including neutralization of viruses and combating antibiotic-resistant bacteria is detailed. Overall, the impact of nanobodies in vaccine design, rapid diagnostics, and targeted therapies, besides exploring their role in deciphering microbial structures and virulence mechanisms are highlighted. Indeed, nanobodies are reshaping the future of infectious disease prevention and treatment.

Nour El-Din, H. T., M. M. Elsebaie, N. S. Abutaleb, A. M. Kotb, A. S. Attia, M. N. Seleem, and A. S. Mayhoub, "Expanding the structure-activity relationships of alkynyl diphenylurea scaffold as promising antibacterial agents.", RSC medicinal chemistry, vol. 14, issue 2, pp. 367-377, 2023. Abstract

With the continuous and alarming threat of exhausting the current antimicrobial arsenals, efforts are urgently needed to develop new effective ones. In this study, the antibacterial efficacy of a set of structurally related acetylenic-diphenylurea derivatives carrying the aminoguanidine moiety was tested against a panel of multidrug-resistant Gram-positive clinical isolates. Compound 18 was identified with a superior bacteriological profile than the lead compound I. Compound 18 demonstrated an excellent antibacterial profile : low MIC values, extended post-antibiotic effect, refractory ability to resistance development upon extended repeated exposure, and high tolerability towards mammalian cells. Finally, when assessed in a MRSA skin infection animal model, compound 18 showed considerable healing and less inflammation, decrease in the bacterial loads in skin lesions, and it surpassed fusidic acid in controlling the systemic dissemination of . Collectively, compound 18 represents a promising lead anti-MRSA agent that merits further investigation for the development of new anti-staphylococcal therapeutics.

Sabry, M. M., A. M. El-Halawany, W. G. Fahmy, B. M. Eltanany, L. Pont, F. Benavente, A. S. Attia, F. F. Sherbiny, and R. M. Ibrahim, "Evidence on the inhibitory effect of Brassica plants against Acinetobacter baumannii lipases: phytochemical analysis, in vitro, and molecular docking studies.", BMC complementary medicine and therapies, vol. 24, issue 1, pp. 164, 2024. Abstract

BACKGROUND: Infections caused by Acinetobacter baumannii are becoming a rising public health problem due to its high degree of acquired and intrinsic resistance mechanisms. Bacterial lipases penetrate and damage host tissues, resulting in multiple infections. Because there are very few effective inhibitors of bacterial lipases, new alternatives for treating A. baumannii infections are urgently needed. In recent years, Brassica vegetables have received a lot of attention since their phytochemical compounds have been directly linked to diverse antimicrobial actions by inhibiting the growth of various Gram-positive and Gram-negative bacteria, yeast, and fungi. Despite their longstanding antibacterial history, there is currently a lack of scientific evidence to support their role in the management of infections caused by the nosocomial bacterium, A. baumannii. This study aimed to address this gap in knowledge by examining the antibacterial and lipase inhibitory effects of six commonly consumed Brassica greens, Chinese cabbage (CC), curly and Tuscan kale (CK and TK), red and green Pak choi (RP and GP), and Brussels sprouts (BR), against A. baumannii in relation to their chemical profiles.

METHODS: The secondary metabolites of the six extracts were identified using LC-QTOF-MS/MS analysis, and they were subsequently correlated with the lipase inhibitory activity using multivariate data analysis and molecular docking.

RESULTS: In total, 99 metabolites from various chemical classes were identified in the extracts. Hierarchical cluster analysis (HCA) and principal component analysis (PCA) revealed the chemical similarities and variabilities among the specimens, with glucosinolates and phenolic compounds being the major metabolites. RP and GP showed the highest antibacterial activity against A. baumannii, followed by CK. Additionally, four species showed a significant effect on the bacterial growth curves and demonstrated relevant inhibition of A. baumannii lipolytic activity. CK showed the greatest inhibition (26%), followed by RP (21%), GP (21%), and TK (15%). Orthogonal partial least squares-discriminant analysis (OPLS-DA) pinpointed 9 metabolites positively correlated with the observed bioactivities. Further, the biomarkers displayed good binding affinities towards lipase active sites ranging from -70.61 to -30.91 kcal/mol, compared to orlistat.

CONCLUSION: This study emphasizes the significance of Brassica vegetables as a novel natural source of potential inhibitors of lipase from A. baumannii.

Mahdally, N. H., R. A. ElShiekh, B. Thissera, A. Eltaher, A. Osama, M. Mokhtar, N. M. Elhosseiny, M. O. N. A. T. KASHEF, S. Magdeldin, A. M. El Halawany, et al., "Dihydrophenazine: A multifunctional new weapon that kills multidrug-resistant Acinetobacter baumannii and restores carbapenem and oxidative stress susceptibilities.", Journal of applied microbiology, 2024. Abstract

AIMS: The current work aims to fully characterize a new antimicrobial agent against Acinetobacter baumannii, which continues to represent a growing threat to healthcare settings worldwide. With minimal treatment options due to the extensive spread of resistance to almost all the available antimicrobials, the hunt for new antimicrobial agents is a high priority.

METHODS AND RESULTS: An Egyptian soil-derived bacterium strain NHM-077B proved to be a promising source for a new antimicrobial agent. Bio-guided fractionation of the culture supernatants of NHM-077B followed by chemical structure elucidation identified the active antimicrobial agent as 1-hydroxy phenazine. Chemical synthesis yielded more derivatives, including dihydrophenazine (DHP), which proved to be the most potent against A. baumannii, yet it exhibited a safe cytotoxicity profile against human skin fibroblasts. Proteomics analysis of the cells treated with DHP revealed multiple proteins with altered expression that could be correlated to the observed phenotypes and potential mechanism of the antimicrobial action of DHP. DHP is a multi-pronged agent that affects membrane integrity, increases susceptibility to oxidative stress, interferes with amino acids/protein synthesis, and modulates virulence-related proteins. Interestingly, DHP in sub-inhibitory concentrations re-sensitizes the highly virulent carbapenem-resistant A. baumannii strain AB5075 to carbapenems providing great hope in regaining some of the benefits of this important class of antibiotics.

CONCLUSIONS: This work underscores the potential of DHP as a promising new agent with multifunctional roles as both a classical and non-conventional antimicrobial agent that is urgently needed.