Atomic Force Microscopy (AFM) As a Surface Mapping Tool in Microorganisms Resistant Toward Antimicrobials: A Mini-Review

Abstract

The worldwide emergence of antimicrobial resistance (AMR) in pathogenic microorganisms, including bacteria and viruses due to a plethora of reasons, such as genetic mutation and indiscriminate use of antimicrobials, is a major challenge faced by the healthcare sector today. One of the issues at hand is to effectively screen and isolate resistant strains from sensitive ones. Utilizing the distinct nanomechanical properties (e.g., elasticity, intracellular turgor pressure, and Young’s modulus) of microbes can be an intriguing way to achieve this; while atomic force microscopy (AFM), with or without modification of the tips, presents an effective way to investigate such biophysical properties of microbial surfaces or an entire microbial cell. Additionally, advanced AFM instruments, apart from being compatible with aqueous environments—as often is the case for biological samples—can measure the adhesive forces acting between AFM tips/cantilevers (conjugated to bacterium/virion, substrates, and molecules) and target cells/surfaces to develop informative force-distance curves. Moreover, such force spectroscopies provide an idea of the nature of intercellular interactions (e.g., receptor-ligand) or propensity of microbes to aggregate into densely packed layers, that is, the formation of biofilms —a property of resistant strains (e.g., Staphylococcus aureus, Pseudomonas aeruginosa ). This mini-review will revisit the use of single-cell force spectroscopy (SCFS) and single-molecule force spectroscopy (SMFS) that are emerging as powerful additions to the arsenal of researchers in the struggle against resistant microbes, identify their strengths and weakness and, finally, prioritize some future directions for research.

Bacterial adhesion to biomaterials: What regulates this attachment? A review

“…Bacterial adhesion to abiotic surfaces is of great interest to the scientific community because it marks the beginning of biofilm formation, and in that sense, atomic force microscopy (AFM) has opened the way for a detailed understanding of biofilms [ 2 ]. In addition to being compatible with aqueous solution environments, which is an important factor for medical research, and reaching a nanoscale resolution, AFM delivers high-resolution nanometric images [ 13 , 15 , 24 , 37 , 38 ], as well as quantitative measurements of the mechanical forces involved in cell adhesion, which can vary from 5 pN to 100 nN [ 12 ], making it possible to probe interactions at the molecular level between different species [ 2 , 19 , 37 ] ( Fig. 1 ).…”

“…The cantilever can have a sharp tip (standard), a colloidal tip (to deliver a more defined geometry), or a functionalized tip, to probe specific chemical interactions [ 13 ]. The adhesion is recorded in newtons and determined by the force exerted by the tip on the sample [ 24 , 37 , 40 ]. The scan can be performed in constant contact, intermittent contact, or without contact [ 24 , 40 ] ( Fig.…”

“…In addition, in force spectroscopy, the tip is approximated and retracted from the surface, and the force-distance (FD) curves this generates provide measurements of the physical properties of the sample, such as stiffness, elasticity, deformation, and adhesion [ 13 , 24 , 37 ]. FD-based images make it possible to map the spatial distribution of these properties in nanoscale [ 24 ].…”

“…FD-based images make it possible to map the spatial distribution of these properties in nanoscale [ 24 ]. Probe functionalization with ligands allows probing, for example, a single bacterial adhesin exposed in a live bacterium and a single protein in the extracellular matrix; as well as probing the interactions of force between a single cell and a substrate [ 24 , 37 ].…”

Craft of Co-encapsulation in Nanomedicine: A Struggle To Achieve Synergy through Reciprocity

“…A significant fraction of such co-encapsulated nanocarriers was developed to target bacterial strains known for drug resistance, , such as Staphylococcus aureus, Mycobacterium tuberculosis, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Chlamydia trachomatis (Table ). Especially in Mycobacterium tuberculosis, co-encapsulation of up to four antitubercular drugs, viz., isoniazid, rifampicin, pyrazinamide, and streptomycin, was achieved using liposomes .…”