Atomic Force Microscopy Analysis of the Acinetobacter baumannii Bacteriophage AP22 Lytic Cycle

Abstract

Background Acinetobacter baumannii is known for its ability to develop resistance to the major groups of antibiotics, form biofilms, and survive for long periods in hospital environments. The prevalence of infections caused by multidrug-resistant A. baumannii is a significant problem for the modern health care system, and application of lytic bacteriophages for controlling this pathogen may become a solution.Methodology/Principal FindingsIn this study, using atomic force microscopy (AFM) and microbiological assessment we have investigated A. baumannii bacteriophage AP22, which has been recently described. AFM has revealed the morphology of bacteriophage AP22, adsorbed on the surfaces of mica, graphite and host bacterial cells. Besides, morphological changes of bacteriophage AP22-infected A. baumannii cells were characterized at different stages of the lytic cycle, from phage adsorption to the cell lysis. The phage latent period, estimated from AFM was in good agreement with that obtained by microbiological methods (40 min). Bacteriophage AP22, whose head diameter is 62±1 nm and tail length is 88±9 nm, was shown to disperse A. baumannii aggregates and adsorb to the bacterial surface right from the first minute of their mutual incubation at 37°C.Conclusions/SignificanceHigh rate of bacteriophage AP22 specific adsorption and its ability to disperse bacterial aggregates make this phage very promising for biomedical antimicrobial applications. Complementing microbiological results with AFM data, we demonstrate an effective approach, which allows not only comparing independently obtained characteristics of the lytic cycle but also visualizing the infection process.

Antibiotic-induced modifications of the stiffness of bacterial membranes

“…In fact, most papers focus only on the morphological modifications induced by antibiotics, imaging in very-high detail the dehydrated membranes of the bacteria (Cui et al, 2012;Dubrovin et al, 2012;Hyldgaard et al, 2012). The few groups that investigate the stiffness of the living bacteria have, up to now, prepared samples using bacteria exposed to different environmental conditions and have only compared the average stiffness values of Journal of Microbiological Methods 93 (2013) [80][81][82][83][84] Abbreviations: PDMS, polydimethylsiloxane; PBS, phosphate buffered saline; LB, lysogeny broth; APTES, 3-aminopropyltriethoxysilane; FD, force distance; FV, force volume.…”

Surface topological differences of phage infected uropathogenic Escherichia coli (UPEC) strains, revealed by atomic force microscopy

“…Many researchers are using AFM for studying different morphologies of phages and their effect on the infected host. The interaction of Acinetobacter baumannii with its lytic phage was detected and observed by Dubrovin et al (2012). They also reported that the phage has high adsorption rate and ability to disperse bacterial aggregates of A. baumannii , which is a nosocomial pathogen.…”

Bacteriophage ZCSE2 is a Potent Antimicrobial against Salmonella enterica Serovars: Ultrastructure, Genomics and Efficacy

“…3.9. ZCSE2 Characterization and Imaging Bacterial Lysis with AFM Atomic force microscopy imaging was carried out on a HOPG hydrophobic surface that maintains the water content to prevent damage over the course of the experiment [14,15]. Typically, the AFM examination was performed over 1-2 h incubation at 20 to 25 • C after dispensing bacteria and phages on the HOPG surface.…”

“…The 3D image presented in Figure 6a shows cells in the process of infection and phage-mediated lysis. Figure 6b shows an AFM phase image collected simultaneously, where the color contrast in the AFM phase differentiates the lysis event at the surface of the bacterium [14]. Lysis is associated with the emergence of ZCSE2 phage, as indicated in the circle in Figure 6a.…”