**2. Bacteria**

Because of their incidence in global health, this study centered on two types of bacteria: a Gram-negative and a Gram-positive one. Details of them are provided in the next sections.

### **2.1** *Escherichia coli*

*Escherichia coli* (*E. coli*) is a Gram-negative, rod-shaped, facultative anaerobic bacterium, as shown in **Figure 1**. The cell wall consists of an outer membrane with lipopolysaccharide and peptidoglycan along with a plasma membrane. A good analogy is that this type of bacteria bears both an outer and an inner skin that offer double protection against foreign agents. Theodor Escherich first described this microorganism in 1885, making it one of the most studied bacteria in the world. *E. coli* strains colonized the gastrointestinal tract of humans and animals as a normal

**75**

*Biodegradable Chitosan Matrix Composite Reinforced with Titanium Dioxide for Biocidal…*

flora [12]. Despite this, some strains have evolved into a pathogenic *E. coli*. This bacterium acquires virulence factors through transposons, bacteriophages, plasmids, and other pathogenicity islands. One can categorize *E. coli* as a pathogen, according to the pathogenicity mechanisms and clinical symptom serogroups or through

There is a variety of foods and environmental sources for the *E. coli* to grow that are resistant to a breadth of antimicrobial drugs, usually used in medicine and agriculture. Their particular resistance to antibiotics is of great importance, because these are Gram-negative pathogens commonly found in humans. For instance, there are different sources of contamination of vegetables, such as poor water treatment and the presence of fertilizers used during cultivation. Similarly, water or food contaminated with wastes can infect animals. Another vector of contamination is via meat products as a result of improper handling and processing or lack of hygiene [13]. There are numerous serotypes in enterohemorrhagic *E. coli* (EHEC) that are frequently associated with human diseases such as O26:H11, O91:H21, O111:H8, O157:NM, and O157:H7 [12]. *E. coli* O157:H7 is the most common isolated serotype of *E. coli*. It has been frequently isolated from people in the United States, Japan, and the United Kingdom. The *E. coli* O157:H7 is also a common food-related pathogen leading to major worldwide health problems. This enterohemorrhagic pathogen

can cause different clinical symptoms ranging from diarrhea to death.

infected people or by contact with contaminated objects. Some common infections caused by *S. aureus* are:

in the lungs and accumulation of pus

*Staphylococcus aureus* (*S. aureus*) is also a common bacterium in the human body. This Gram-positive bacterium possesses a cell wall bearing only a thick peptidoglycan layer followed by a plasma membrane, as shown in **Figure 2**. It is present in the mucous membranes (nose) and in the skin [14]; 30% of healthy adults have these bacteria in the nose, and about 30% has it in the skin [15]. These percentages are increased in people who work in hospitals. *S. aureus* is spread by contact with

• Pneumonia that causes fever, shortness of breath, and cough, causing abscesses

*DOI: http://dx.doi.org/10.5772/intechopen.84397*

*Optical image of E. coli stained using Gram's method.*

virulence factors [12].

**Figure 1.**

**2.2** *Staphylococcus aureus*

*Biodegradable Chitosan Matrix Composite Reinforced with Titanium Dioxide for Biocidal… DOI: http://dx.doi.org/10.5772/intechopen.84397*

**Figure 1.** *Optical image of E. coli stained using Gram's method.*

*Renewable and Sustainable Composites*

bacterial cell death.

antibiotics, ranging from the expression of enzymes and modification of cell components all the way to the creation of efflux pumps [5]. For example, enzymes such as β-lactamase [6] could alter the chemical structure of the antibiotics, leaving them inactive. Meanwhile, cell components such as ribosomes [7] offer resistance and efflux pump work by removing antibiotics from the inside of a cell and maintaining

Furthermore, NPs work differently when it comes to dealing with bacteria; this makes any antibiotic resistance ineffective against NPs. The NP antimicrobial mechanism falls into three categories: oxidative stress induction [8], metal ion release [9], and nonoxidative [10]. These mechanisms all work toward producing

Nanoparticles, as nanostructured materials, can be defined as three-dimensional materials with dimensions in the nanoscale (1–100 nm). As many studies suggest, they offer an array of antibacterial properties against Gram-negative and Grampositive bacteria, such as *E. coli* and *S. aureus*, respectively. For example, zinc oxide (ZnO) NPs are capable of inhibiting the growth of *S. aureus*, while silver NPs

As mentioned above, there are three main mechanisms by which NPs produce apoptosis. One can summarize the entire process as follows: first, the disruption of bacterial cell membrane occurs, followed by (whenever possible) the production of reactive oxygen species (ROS), which induces the penetration of the bacterial cell to disrupt the intracellular mechanism needed by the bacteria to function properly. NPs can produce ROS by different mechanisms, but, in the scientific community,

MDR genes have proliferated to such an extent that they become a challenge for the existing resources to counteract them. Accordingly, investigations related to

Prior research demonstrated that separately chitosan and TiO2 (anatase polymorph) possess antibacterial properties under ultraviolet light irradiation. This characteristic can clean water sources, which represents one of the main vectors

Water has become a precious resource, causing the access to fresh and clean water to become a critical matter at a global scale. Nowadays, innovative methods must offer clean, fresh, and purified water. As mentioned above, in this context, chitosan and TiO2 biocomposites could be an economically viable alternative to resolve this problem by removing oils, heavy metals, and pathogen colonies.

Because of their incidence in global health, this study centered on two types of bacteria: a Gram-negative and a Gram-positive one. Details of them are provided in

*Escherichia coli* (*E. coli*) is a Gram-negative, rod-shaped, facultative anaerobic bacterium, as shown in **Figure 1**. The cell wall consists of an outer membrane with lipopolysaccharide and peptidoglycan along with a plasma membrane. A good analogy is that this type of bacteria bears both an outer and an inner skin that offer double protection against foreign agents. Theodor Escherich first described this microorganism in 1885, making it one of the most studied bacteria in the world. *E. coli* strains colonized the gastrointestinal tract of humans and animals as a normal

antibacterial materials have become mandatory to protect human lives.

a safe environment for which the bacteria can grow normally.

demonstrate antimicrobial activity against *E. coli* [11].

the photocatalytic hypothesis is most widely accepted.

used by bacteria to infect the human body.

**74**

**2. Bacteria**

the next sections.

**2.1** *Escherichia coli*

flora [12]. Despite this, some strains have evolved into a pathogenic *E. coli*. This bacterium acquires virulence factors through transposons, bacteriophages, plasmids, and other pathogenicity islands. One can categorize *E. coli* as a pathogen, according to the pathogenicity mechanisms and clinical symptom serogroups or through virulence factors [12].

There is a variety of foods and environmental sources for the *E. coli* to grow that are resistant to a breadth of antimicrobial drugs, usually used in medicine and agriculture. Their particular resistance to antibiotics is of great importance, because these are Gram-negative pathogens commonly found in humans. For instance, there are different sources of contamination of vegetables, such as poor water treatment and the presence of fertilizers used during cultivation. Similarly, water or food contaminated with wastes can infect animals. Another vector of contamination is via meat products as a result of improper handling and processing or lack of hygiene [13].

There are numerous serotypes in enterohemorrhagic *E. coli* (EHEC) that are frequently associated with human diseases such as O26:H11, O91:H21, O111:H8, O157:NM, and O157:H7 [12]. *E. coli* O157:H7 is the most common isolated serotype of *E. coli*. It has been frequently isolated from people in the United States, Japan, and the United Kingdom. The *E. coli* O157:H7 is also a common food-related pathogen leading to major worldwide health problems. This enterohemorrhagic pathogen can cause different clinical symptoms ranging from diarrhea to death.
