Morphological analysis of the antimicrobial action of nitric oxide on Gram-negative pathogens using atomic force microscopy

Abstract

Atomic force microscopy (AFM) was used to study the morphological changes of two Gram-negative pathogens, Pseudomonas aeruginosa and Escherichia coli, after exposure to nitric oxide (NO). The time-dependent effects of NO released from a xerogel coating and the concentration-dependent effects rendered by a small-molecule that releases NO in a bolus were examined and compared. Bacteria exhibited irregular and degraded exteriors. With NO-releasing surfaces, an increase in surface debris and disorganized adhesion patterns were observed compared to controls. Analysis of cell surface topography revealed that increasing membrane roughness correlated with higher doses of NO. At a lower total dose, NO delivered via a bolus resulted in greater membrane roughness than NO released from a surface via a sustained flux. At sub-inhibitory levels, treatment with amoxicillin, an antibiotic known to compromise the integrity of the cell wall, led to morphologies resembling those resulting from NO treatment. Our observations indicate that cell envelope deterioration is a visible consequence of NO-exposure for both Gram-negative species studied.

Copper Complex in Poly(vinyl chloride) as a Nitric Oxide-Generating Catalyst for the Control of Nitrifying Bacterial Biofilms

“…It was shown in earlier studies that a higher amount of nitric oxide released over short durations is more damaging to Gram-negative bacteria than a prolonged release of lower amounts of nitric oxide. 30 Similar findings were also reported on human fibroblasts, where the reduction in fibroblast numbers exhibited by a copper− nitrite−ascorbic acid system has a higher degree of correlation to the amount of nitric oxide generated in the quick burst (first 200 s) rather than the total amount of nitric oxide over 600 s. 19 3.4. Nitrifying Bacteria Biofilm Dispersal Studies.…”

A multi-defense strategy: Enhancing bactericidal activity of a medical grade polymer with a nitric oxide donor and surface-immobilized quaternary ammonium compound

“…On the SNAP-BPAM films, the dead cells with distorted morphologies (like that of SNAP films) were dispersed across the surface which might be due to the relatively lower hydrophobicity (C.A = 63.5° ± 0.5) of the SNAP-BPAM films’ surface as compared to SNAP films (C.A = 115° ± 0.2) resulting from the positively charged ammonium functional groups. Such distortion and irregularity in bacterial colonies can also be attributed to the deterioration of bacterial cell wall by NO as observed via Atomic Electron Microscopy and Cell Surface Topography analysis [83]. Overall, lived/dead staining experiment combined with Cell Profiler software further validated that combined NO and surface-bound quaternary ammonium can provide dual antibacterial activities and thus significantly enhance the biocidal activity as compared to the individual agent.…”

Nitric oxide release: Part III. Measurement and reporting

“…For example, polymeric device coatings capable of releasing NO in a controlled manner have been shown to decrease bacterial infection and improve tissue integration and/or blood compatibility for subcutaneous glucose sensors, 7, 39 orthopedic devices, 40, 41 and vascular stents. 42 Macromolecular NO release scaffolds are also being developed as stand-alone therapeutics against pathogens 43, 44 and cancer, 10 with much of their efficacy related to their ability to deliver large NO payloads directly to cells. Due to the assorted methods for measuring NO and the related diverse data, direct comparison across NO release scaffold types is both challenging and important.…”