Light and Phages on Tackle of Infectious Diseases

*Felipe de Paula Nogueira Cruz, Andréa Cristina Bogas and Cristina Paiva de Sousa*

## **Abstract**

There has been an important increase in the emergence of resistance in microbial population worldwide. This trajectory needs, necessarily new approaches to treat infectious diseases. The ability to detect and prevent the evolutionary trajectories of microbial resistance would be of value. Photodynamic inactivation (PDI) represents an efficient alternative treatment for diseases caused by viruses, which can cause infections well documented in various mammals. PDI can kill cells after exposure with the appropriate photosensitizer (PS), light of adequate wavelength combined with the presence of oxygen, without inducing resistance. Cytotoxic reactive species formed interaction with vital biomolecules leading to irreversible microbial inactivation. Bacteriophages can act on delivering antimicrobial agents into bacteria, which consist in a likely instrument for the treatment of infectious diseases. Non-enveloped bacteriophages are more difficult to tolerate photoinactivation than enveloped phages, which makes them an important model tool to evaluate the efficiency of PDI therapy against viruses that cause diseases in humans. Combination of photosensitizers and bacteriophage therapy can be employed to eradicate biofilms, contributing to control of infections also caused by drug-resistant bacteria.

**Keywords:** bacteriophages, biofilm, microbial resistance, photodynamic therapy, reactive oxygen species

### **1. Introduction**

Despite the remarkable progress in human medicine, infectious diseases of microbial origin are one of main global concern to public health [1] worldwide. The relative unavailability of efficient drugs the misuse and/or excessive use of antimicrobials, are some factors that make infections harder or impossible to treat, increasing the risk of spreading diseases and deaths [2]. The gap in the discovery of new antibiotics over the decades [3, 4] also contributes to the increased risk of infectious diseases.

The emergence of antibiotic-resistant "superbugs" and their rapid global spread are alarming [5]. These microorganisms are members of a group known as nosocomial ESKAPE (*Enterococcus faecium*, *Staphylococcus aureus*, *Klebsiella pneumoniae*, *Acinetobacter baumannii*, *Pseudomonas aeruginosa* and *Enterobacter* spp.), associated with major risk of mortality in immunocompromised patients [6, 7]. Other highlights in the global list of drug-resistant priority pathogens are the third generation cephalosporins (3GC) resistant *Escherichia coli*, fluoroquinolone-resistant *Neisseria gonorrhoeae*, *Streptococcus pneumoniae*, *Salmonella* spp. and *Candida auris* [8, 9].

Drug-resistant pathogens can be transmitted through the hospital environment, increasing the severity in relation to Health Care-Associated Infections (HAIs) [10], also causing an important economic impact especially in developing countries. In these countries, the infectious diseases are more prevalent, and the prevention measures requires the use of drugs that maximize costs [7]. Given this scenario, effective antibiotics and strategies to combat antimicrobial resistance, prevent the high number of deaths each year and an economic crisis worldwide become urgent [11, 12]. This chapter describes photodynamic treatment, bacteriophages utilization and the combination of both as alternative therapies for minimize the excessive exposure of patients to antibiotic and risks of multi-resistant strains development.

### **2. Photodynamic therapy: past**

The therapeutic potential of light has been used for hundreds of years by the ancient civilizations in Egypt, China, and India. Also, over 3000 years ago, light was used in conjunction with reactive chemicals to treat various conditions such as vitiligo, psoriasis, and some types of skin cancer. In China, it was introduced by Lingyan Tzu-Ming in the first century b.C., and, four centuries later, became a ritual practice in which it was based on exposing a piece of green paper containing a red dye and exposed to sunlight, then it was soaked in water and ingested right after [13, 14].

In the last few decades, Photodynamic therapy (PDT) has emerged as a promising intervention treatment for cancer therapy. However, it is widely used in the removal of small vessels and in the treatment of microbial infections [15]. Still, the first concepts of the nature of light emerged in the 17th century. Preliminary work on the properties of light, such as that of Christiaan Huygens, who used wave theory to explain the reflection and refraction of light in 1690, and, later, the discovery of the properties of electricity and magnetism, in the early 19th century [16, 17].

In fact, quantum theory started when Max Planck, in 1900 published an article that explained the spectral distribution of Blackbody Radiation, which perfectly fitted the laws of thermodynamics with the laws of electromagnetism. And in the same year, Oscar Raab was scientifically proven to have the beneficial effects of light. In his experiment, it was observed that the combination of light with the acridine dye (**Figure 1**) was lethal for Paramecium species. In the same year, the French neurologist, Jean Prime, discovered that oral eosin, used to treat patients with epilepsy, could cause dermatitis when exposed to sunlight [16, 18].

According to electrodynamic theory, light consists of an oscillating electromagnetic field that propagates as a wave through a vacuum or through a medium [16]. This means that when light propagates through space, it behaves like a wave, while when interacting with matter, it behaves like particles [16, 17, 19]. This concept was described by Einstein in 1905 based on the theories of Planck and Hertz for the explanation of the photoelectric effect (Eq. (1)). For that, Einstein assumed that light had

**Figure 1.** *Chemical structure of acridine.*

*Light and Phages on Tackle of Infectious Diseases DOI: http://dx.doi.org/10.5772/intechopen.96425*

a corpuscular nature, that is, it would be formed by small bundles of energy (quanta) called photons. Einstein also proposed the existence of a dependency relationship between the photoelectric emission and the frequency of incident radiation. For this theory to be valid, light could not be considered as a wave, but as a particle [17, 20].

Finally, in 1924, de Broglie created the hypothesis of wave-particle duality, which was soon recognized by Erwin Schrödinger who developed the wave propagation equation in matter in 1926 (Eq. (2)). Still during this period, other important scientists contributed to the establishment of quantum mechanics such as, for example, Max Born (Matrix Quantum Mechanics), Paul Dirac (Movement of sub-atomic particles), Werner Heisenberg (Uncertainty Principle) and Wolfgang Pauli (Principle of Exclusion) [20].

**Equation 1:** According to Einstein, each photon has an energy proportional to the frequency of light.

$$\mathbf{E}\_{p\text{katon}} = \hbar \mathbf{c} / \mathcal{Z} \tag{1}$$

E = de um quantum energy of light h = Planck constant = 6,63 x 10–34 J.s c = Speed of light (3 × 1010 cm/s) λ = Frequency of light (Hz)

**Equation 2:** Erwin Schrödinger allows to determine to find the wave function of a particle, from the knowledge of the potential energy to which it is submitted.

$$-\frac{\hbar^2}{2\text{m}}\nabla^2\Psi + V\Psi = \text{i}\hbar\frac{\partial\Psi}{\partial t} \tag{2}$$

ħ = Planck constant (6,63 x 10–34 J.s) squared reduced


In the same year, Policard [21] conducted a study where he detected the presence of porphyrins in high concentrations in malignant tumors. These, completely non-toxic, were able to destroy the tumor tissue in the presence of visible light and oxygen [21].

Later, in 1950 Schwartz demonstrated that the long-lasting phototoxic effect was not promoted only by hematoporphyrin. The action occurred due to an oligomeric mixture together with it. Since hematoporphyrin is eliminated quickly from the body, Schwartz enriched the oligomer mixture and this preparation was called hematoporphyrin derivative (HpD), which contains in addition to monomers, oligomers containing two to nine units of porphyrin [14, 22].

In the study conducted by Weishaupt [23], it was demonstrated that the destruction of tumor cells was due to the formation of singlet oxygen molecules.

Finally, in 1993, Photofrin ® (Axcan Pharma Inc., Canada) was approved for the treatment of superficial bladder cancer by the Canadian Health Protection Branch. Subsequently, in 1998 the Food and Drug Administration (FDA) authorized PDT in the treatment of cancer [24].
