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IntroductionThe escalating prevalence of bacterial resistance, particularly multidrug-resistant bacteria like Acinetobacter baumannii, has become a significant global public health concern. The CRISPR-Cas system, a crucial defense mechanism in bacteria against foreign genetic elements, provides a competitive advantage. Type I-Fb and Type I-Fa are two subtypes of CRISPR-Cas systems that were found in A. baumannii, and the I-Fb CRISPR-Cas system regulates antibiotic resistance in A. baumannii. However, it is noteworthy that a majority of clinical isolates of A. baumannii lack or have incomplete CRISPR-Cas systems and most of them are multidrug-resistant. In light of this, our study aimed to examine the impact of antibiotic pressure on the fitness cost of the I-Fb CRISPR-Cas system in A. baumannii.Methods and ResultsIn the study, we conducted in vitro competition experiments to investigate the influence of sub-minimum inhibitory concentration (sub-MIC) on the CRISPR-Cas systems’ fitness cost in A. baumannii. We found that the fitness cost of the CRISPR-Cas system was increased under sub-MIC conditions. The expression of CRISPR-Cas-related genes was decreased, while the conjugation frequency was increased in AB43 under sub-MIC conditions. Through metabolomic analysis, we identified that sub-MIC conditions primarily affected energy metabolism pathways. In particular, we observed increased carbon metabolism, nitrogen metabolism, and intracellular ATP. Notably, the CRISPR-Cas system demonstrated resistance to the efflux pump-mediated resistance. Furthermore, the expression of efflux pump-related genes was increased under sub-MIC conditions.ConclusionOur findings suggest that the I-Fb CRISPR-Cas system confers a significant competitive advantage in A. baumanni. However, under sub-MIC conditions, its function and the ability to inhibit the energy required for efflux pumps are reduced, resulting in an increased fitness cost and loss of competitive advantage.

Summary: Biofilm formation plays a significant role in antibiotic resistance, necessitating the search for alternative therapies against biofilm-associated infections. This study demonstrates that 20 μg/mL tryptanthrin can hinder biofilm formation above 50% in various A. baumannii strains. Tryptanthrin impacts various stages of biofilm formation, including the inhibition of surface motility and eDNA release in A. baumannii, as well as an increase in its sensitivity to H202. RT-qPCR analysis reveals that tryptanthrin significantly decreases the expression of the following genes: abaI (19.07%), abaR (33.47%), bfmR (43.41%), csuA/B (64.16%), csuE (50.20%), ompA (67.93%), and katE (72.53%), which are related to biofilm formation and quorum sensing. Furthermore, tryptanthrin is relatively safe and can reduce the virulence of A. baumannii in a Galleria mellonella infection model. Overall, our study demonstrates the potential of tryptanthrin in controlling biofilm formation and virulence of A. baumannii by disrupting different stages of biofilm formation and intercellular signaling communication.

Non‐compressible wounds are a major source of high mortality in trauma victims. Here the authors report on the creation of xerogels impregnated with liquid adhesives which can rapidly absorb fluids promoting blood clotting while forming adhesions to tissue and demonstrate the xerogel in ex vivo and in vivo models.

ABSTRACT The rapid development of methicillin-resistant Staphylococcus aureus (MRSA) drug resistance and the formation of biofilms seriously challenge the clinical application of classic antibiotics. Extracts of the traditional herb Chenopodium ambrosioides L. were found to have strong antibiofilm activity against MRSA, but their mechanism of action remains poorly understood. This study was designed to investigate the antibacterial and antibiofilm activities against MRSA of flavonoids identified from C. ambrosioides L. in combination with classic antibiotics, including ceftazidime, erythromycin, levofloxacin, penicillin G, and vancomycin. Liquid chromatography-mass spectrometry (LC-MS) was used to analyze the nonvolatile chemical compositions. Reverse transcription (RT)-PCR was used to investigate potential multitargets of flavonoids based on global transcriptional responses of virulence and antibiotic resistance. A synergistic antibacterial and biofilm-inhibiting activity of the alcoholic extract of the ear of C. ambrosioides L. in combination with penicillin G was observed against MRSA, which proved to be closely related to the interaction of the main components of kaempferol rhamnosides with quercetin. In regard to the mechanism, the increased sensitivity of MRSA to penicillin G was shown to be related to the downregulation of penicillinase with SarA as a potential drug target, while the antibiofilm activity was mainly related to downregulation of various virulence factors involved in the initial and mature stages of biofilm development, with SarA and/or σB as drug targets. This study provides a theoretical basis for further exploration of the medicinal activity of kaempferol rhamnosides and quercetin and their application in combination with penicillin G against MRSA biofilm infection. IMPORTANCE In this study, the synergistic antibacterial and antibiofilm effects of the traditional herb C. ambrosioides L. and the classic antibiotic penicillin G on MRSA provide a potential strategy to deal with the rapid development of MRSA antibiotic resistance. This study also provides a theoretical basis for further optimizing the combined effect of kaempferol rhamnosides, quercetin, and penicillin G and exploring anti-MRSA biofilm infection research with SarA and σB as drug targets.

Abstract Biological tissues hinge on blood perfusion and mechanical toughness to function. Injectable hydrogels that possess both high permeability and toughness have profound impacts on regenerative medicine but remain a long‐standing challenge. To address this issue, injectable, pore‐forming double‐network hydrogels are fabricated by orchestrating stepwise gelation and phase separation processes. The interconnected pores of the resulting hydrogels enable direct medium perfusion through organ‐sized matrices. The hydrogels are amenable to cell encapsulation and delivery while promoting cell proliferation and spreading. They are also pore insensitive, tough, and fatigue resistant. When tested in biomimetic perfusion bioreactors, the hydrogels maintain physical integrity under prolonged, high‐frequency biomechanical stimulations (>6000 000 cycles at 120 Hz). The excellent biomechanical performance suggests the great potential of the new injectable hydrogel technology for repairing mechanically dynamic tissues, such as vocal folds, and other applications, such as tissue engineering, biofabrication, organs‐on‐chips, drug delivery, and disease modeling.

The CRISPR-Cas system is a bacterial and archaea adaptive immune system and is a newly recognized mechanism for controlling antibiotic resistance gene transfer. Acinetobacter baumannii (A. baumannii) is an important organism responsible for a variety of nosocomial infections. A. baumannii infections have become problematic worldwide because of the resistance of A. baumannii to multiple antibiotics. Thus, it is clinically significant to explore the relationship between the CRISPR-Cas system and drug resistance in A. baumannii. This study aimed to analyze the genomic characteristics of the A. baumannii strain AB3 containing the type I-Fb CRISPR-Cas system, which was isolated from a tertiary care hospital in China, and to investigate the relationship between the CRISPR-Cas system and antibiotic resistance in this strain. The whole-genome sequencing (WGS) of the AB43 strain was performed using Illumina and PacBio sequencing. The complete genome of AB43 consisted of a 3,854,806 bp chromosome and a 104,309 bp plasmid. The specific characteristics of the CRISPR-Cas system in AB43 are described as follows: (1) The strain AB43 carries a complete type I-Fb CRISPR-Cas system; (2) Homology analysis confirmed that the cas genes in AB43 share high sequence similarity with the same subtype cas genes; (3) A total of 28 of 105 A. baumannii AB43 CRISPR spacers matched genes in the bacteriophage genome database and the plasmid database, implying that the CRISPR-Cas system in AB43 provides immunity against invasive bacteriophage and plasmids; (4) None of the CRISPR spacers in A. baumannii AB43 were matched with antimicrobial resistance genes in the NCBI database. In addition, we analyzed the presence of antibiotic resistance genes and insertion sequences in the AB43 strain and found that the number of antibiotic resistance genes was not lower than in the “no CRISPR-Cas system” strain. This study supports the idea that the CRISPR-Cas system may inhibit drug-resistance gene expression via endogenous gene regulation, except to the published mechanism that the CRISPR-Cas system efficiently limits the acquisition of antibiotic resistance genes that make bacteria sensitive to antibiotics.

To verify the size and emergence time of new permeability pathways (NPPs) in malaria parasites, the permeability of the Plasmodium falciparum-infected erythrocytes was tested with different particle sizes of nanomaterials by flow cytometry assay. The results confirmed the permeability of the host cell membrane increases with parasite maturation for the stage-development evolution of NPPs, and especially found that a particle size of about 50 nm had higher efficiency. As a kind of the novel nanomaterials, nitrogen-doped carbon dots (NCDs) showed no toxicity, specificity binding ability to the malaria parasites, and could label live elder blood-stage P. falciparum through NPPs, indicating the potential application in cell imaging. NPPs and some nanomaterials such as NCDs deserve more attention and exploration for the elimination and prevention of malaria.

Hydrogel adhesion that can be easily modulated in magnitude, space, and time is desirable in many emerging applications ranging from tissue engineering and soft robotics to wearable devices. In synthetic materials, these complex adhesion behaviors are often achieved individually with mechanisms and apparatus that are difficult to integrate. Here, we report a universal strategy to embody multifaceted adhesion programmability in synthetic hydrogels. By designing the surface network topology of a hydrogel, supramolecular linkages that result in contrasting adhesion behaviors are formed on the hydrogel interface. The incorporation of different topological linkages leads to dynamically tunable adhesion with high-resolution spatial programmability without alteration of bulk mechanics and chemistry. Further, the association of linkages enables stable and tunable adhesion kinetics that can be tailored to suit different applications. We rationalize the physics of polymer chain slippage, rupture, and diffusion at play in the emergence of the programmable behaviors. With the understanding, we design and fabricate various soft devices such as smart wound patches, fluidic channels, drug-eluting devices, and reconfigurable soft robotics. Our study presents a simple and robust platform in which adhesion controllability in multiple aspects can be easily integrated into a single design of a hydrogel network. [ABSTRACT FROM AUTHOR]