Growth Phase- and Desiccation-Dependent Acinetobacter baumannii Morphology: An Atomic Force Microscopy Investigation

Abstract

Acinetobacter baumannii has emerged as a major bacterial pathogen during the past three decades. The majority of the A. baumannii infections occur in hospitals and are caused by strains endowed with high desiccation tolerance, which represents an essential feature for the adaptation to the nosocomial environment. This work aims at investigating the desiccation response of the multidrug-resistant A. baumannii strain ACICU as a function of the bacterial growth phase and oxygen availability, by correlating bacterial survival with shape alterations. The three dimensional morphological analysis of bacteria was carried out by atomic force microscopy (AFM), following the evolution of bacterial shape descriptors, such as the area, volume, roughness of individual cell membranes, and the cell cluster roughness, which exhibited peculiar and distinctive behavior as a function of the growth conditions. AFM images of A. baumannii ACICU cells revealed a prevalence of the coccoid morphology at all growth stages, with a tendency to reduce their size in the stationary phase, accompanied by a higher survival rate to air-drying. Moreover, cells harvested from the logarithmic phase featured a larger volume and resulted to be more sensitive to desiccation compared to the cells harvested at later growth stages. In addition, oxygen deprivation caused a significant decrease in cellular size and was associated with the formation of pores in the cell membrane, accompanied by a relative reduction in culturability after desiccation. Morphological plasticity and multidrug resistance may contribute to desiccation tolerance and therefore to persistence in the hospital setting.

Biocompatibility and Antibacterial Properties of TiCu(Ag) Thin Films Produced by Physical Vapor Deposition Magnetron Sputtering

“…The P. aeruginosa bacteria were instead shallower with an average height of 230 nm and showed an elongated shape, often with flagella, having an average long-axis length of 1300 nm. The tendency of bacteria towards clustering in Ctrl samples, evident in Figure 7B, was observed for similar deposition conditions and attributed to the capillary flow induced by the evaporation of the drop deposited [39,40]. Conversely, the TiCu surfaces analyzed after bacteria detaching showed morphological features with heights below 30 nm (thus more than one order of magnitude lower than typical bacteria heights), likely to be attributed to residual of the nutrient medium used for the growth.…”

Biocompatibility and antibacterial properties of TiCu(Ag) thin films produced by physical vapor deposition magnetron sputtering

“…The P. aeruginosa bacteria were instead shallower with an average height of 230 nm and showed an elongated shape, often with flagella, having an average long-axis length of 1300 nm. The tendency of bacteria towards clustering in control samples (Figure 7B) was observed for similar deposition conditions and attributed to the capillary flow induced by the evaporation of the drop deposited [39,40]. Conversely, the TiCu surfaces analyzed after bacteria detaching showed morphological features with heights below 30 nm (thus more than one order of magnitude lower than typical bacteria heights), likely to be attributed to residual of the nutrient medium used for the growth.…”

Pixantrone Sensitizes Gram-Negative Pathogens to Rifampin

“…Glass slides were cleaned with pure ethanol before bacterial deposition. AFM measurements were performed using a Dimension ICON AFM (Bruker) ( 61 ).…”