Toxin-Antitoxin Systems in Pseudomonas aeruginosa

By Bentham Science Publishers

Pseudomonas aeruginosa is known as a persistent bacterial pathogen. Antibiotics are currently the most common bacterial treatment for related infections but cases of microbial resistance are on the rise. Toxin-Antitoxin Systems in Pseudomonas aeruginosa describes one of the most important antimicrobial targets in the bacterium species. The contributors have compiled comprehensive information on the subject. The reference initially acquaints the reader with key topics about P. aeruginosa infection including virulence factors, pathogenicity, epidemiology, laboratory diagnosis and antibiotic resistance. This is followed by detailed chapters on toxin-antitoxin systems which explain their role in the bacterial pathogenesis with reference to P. aeruginosa. The comprehensive information on the subject makes this an ideal reference for newcomers to the field of bacteriology and target discovery. Students of medical microbiology and medical professionals who are interested in the finer details of P. aeruginosa pathogenicity will also be equipped with sufficient information to join the discussion on this topic with fellow researchers.

• Language: English
• Publisher: Bentham Science Publishers
• Release date: May 6, 2021
• ISBN: 9781681087931

Book preview

UniversityIlamIran

An Overview of Pseudomonas aeruginosa

M. Mahmoudi¹, S. Ghafourian¹, *, B. Badakhsh²

¹ Department of Microbiology, Faculty of Medicine, Ilam University of Medical Sciences, Ilam, Iran

² Department of Gastroenterology, Faculty of Medicine, Ilam University of Medical Sciences, Ilam, Iran

Abstract

Pseudomonas aeruginosa is an absolute aerobic gram-negative bacterium that has attracted the attention of many researchers for many years. There are plenty of reasons to research on P. aeruginosa , which unfortunately has made it an invincible bacterium. Adaptation to environmental changes is one of the most important capabilities that organisms need to survive. This rule also applies to the world of bacteria. P. aeruginosa is one of the most well-known bacteria in terms of adaptation to a variety of biological environments. Besides, P. aeruginosa has a variety of hosts, including humans. It is known as an opportunistic pathogen, therefore infections caused by P. aeruginosa are highly important in immunocompromised patients and it is a major cause of mortality and morbidity in cystic fibrosis patients. Also, P. aeruginosa is the most important cause of nosocomial infections, which can seriously threaten the lives of hospitalized patients. Severe resistance to most antibiotics is one of the other reasons for its success in causing infection and survival. P. aeruginosa can produce many powerful virulent factors that create unique properties in this bacterium. In this chapter, the general characteristics of P. aeruginosa are briefly and usefully explained. So, the reader can get a good idea of this bacterium in a short glance.

Keywords: Overview, Pseudomonas aeruginosa.

---

* Corresponding author S. Ghafourian: Department of Microbiology, Faculty of Medicine, Ilam University of Medical Sciences, Iran; E-mail: [e-mail]

Among all life-threatening bacteria, the name of Pseudomonas aeruginosa (P. aeruginosa) is always shining due to its incredible capacity to stay alive and to destroy its hosts. Initially, it is best to have an overview of the general characteristics of P. aeruginosa to be much more ready for more interesting content of the present book.

P. aeruginosa is a Gram-negative bacterium [1], which is not only obligate aerobe but can also utilize other alternative electron acceptors such as nitrate and can

survive as a facultative anaerobic microorganism at the same time [2, 3]. It is rod-shaped, asprogenous, non-acid-fast and catalase-positive [4].

Besides, P. aeruginosa is a monotrichous flagellated bacterium [5], which makes it different from other fluorescent Pseudomonads (P. putida, P. florescent, etc.) [6], and versatile by one or several polar flagella [7]. Its rod measuring about 0.6 × 2 µm that can be seen as a single bacterium, in pairs and rarely in short chains (pearlescent) [8]. P. aeruginosa appears as multiple colony type that can be considered as different bacteria by non-expert individuals [9]. Generally, two kinds of the colony can be recognized on the agar media. Firstly, it appears as a large and smooth colony with a flat edge and an outstanding center called a fried egg. It is usually isolated from clinical sources. Secondly, it looks rough and outstanding, which is related to natural sources. There is another type, which looks mucous and it is usually isolated from respiratory and urinary secretions [10]. However, the colony of P. aeruginosa has grape-like or tortilla-like odor due to the production of trimethylamine [11, 12]. The optimal temperature for growth is 25°C to 37°C [13]. Also, one of the different features of P. aeruginosa , is its ability to grow at 42°C, which distinguishes it from many other fluorescent Pseudomonas species [14]. The genome size of P. aeruginosa is approximately 5.5–7 Mbp with 65–67% of G+C content [15]. It is also able to use the general source of carbon and nitrogen [16]. P. aeruginosa can use variety of organic molecules, which leads this bacterium to be very ubiquitous [17]. Almost, P. aeruginosa can tolerate hard conditions that's why it is widespread in the environments [18], so, it can be found in soil, water (even distilled water), sewage and specifically in the hospital [19, 20]. In addition, this remarkable property allows P. aeruginosa to be the pathogen for a wide range of hosts including, animals, plants, and humans [21]. In particular, this is an opportunistic and serious pathogen in abnormal host defense, severe burns and cystic fibrosis patients [6, 22, 23]. Indeed, P. aeruginosa is responsible for multiple infections, which can vary from local to systemic as well as the illness severity can be diverse from benign to life-threatening diseases [24].

Many strains of P. aeruginosa produce different kinds of pigments that some of them can dissolve in water and diffuse to the media and some of them are associated with the cell mass. The pigments are prominent to use diagnostic purposes due to its special features. For instance, the pyoverdin is a fluorescent pigment of P. aeruginosa and appears in a yellow-green color that can be seen in a low concentration of iron. In addition, the pyocyanin is the most famous characteristic pigment with the blue-green color. The color of pyocyanin is pH-dependent and it turns red in acidic environments [15]. The pyosyanin is toxic for the ciliated epithelium of the respiratory tract as well as it has a bactericidal effect on Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), Mycobacterium semegmatis [22, 23]. The phenazine-α-carboxylate and chlororaphin can also be seen in orange and green, respectively. The pyorubin can be seen in red color.

Eventually, the pyomelanin is a brown color. There are also some other pigments such as oxychlororaphin etc. [7].

Finally, it may be possible to highlight the importance of P. aeruginosa in a few lines. So, it drives its ability to distribute in the most and hard conditions in nature, having very strong and potent pathogenesis factors and be resistant to most of the antibacterial agents, which makes it one of the most resistant and recalcitrant organisms in the world of creatures.

CONSENT FOR PUBLICATION

Not applicable.

CONFLICT OF INTEREST

The authors declare no conflict of interest, financial or otherwise.

ACKNOWLEDGEMENTS

Declared none.

REFERENCES

History and Etymology

M. Mahmoudi¹, S. Ghafourian¹, *, N. Sadeghifard¹, B. Badakhsh²

¹ Department of Microbiology, Faculty of Medicine, Ilam University of Medical Sciences, Ilam,