**3.1 Upper respiratory tract infections**

Infectious diseases that affect the upper respiratory tract include otitis media, sinusitis, tonsillitis, adenoiditis, pharyngotonsillitis, adenoiditis and chronic

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triggering the appearance of polymicrobial biofilms [43].

rhinosinusitis [42]. In otitis media, infections may be as a result of both respiratory viruses and bacteria such as non-capsulated *Haemophilus influenza, Streptococcus pneumonia*, *Streptococcus pyogenes, Moraxella catarrhalis* and *Staphylococcus aureus*,

The most cited reason for childhood visits to physicians is otitis media with effusion (OME) and is again one of the most reasons for antibiotic therapy in children. Even though OME is regarded as a sterile inflammatory process, current data using a chinchilla model suggest that viable bacteria are present in intricate communities referred to as mucosal biofilms [44]. It is interesting to know that intracellular *Haemophilus influenzae*, *Streptococcus pneumoniae*, *Staphylococcus aureus* and *Moraxella catarrhalis in situ* are found in adenoids from children going through adenoidectomy for the treatment of hypertrophic adenoids or chronic otitis media using Fluorescence in situ hybridization [45]. *Haemophilus influenzae* and intracellular *S. pneumoniae* have also been in middle ear mucosal biopsies in children with

Biofilms were seen in the sinus tissues of 72% of patients affected by chronic

Cystic fibrosis (CF) is a protracted disease of the lower respiratory tract. The most frequent serious clinical complication in CF today is chronic endobronchial infection with *Pseudomonas aeruginosa*. *Pseudomonas aeruginosa* is a microorganism characterized by the capacity to produce large amounts of alginate and developed as a biofilm where micro-colonies of bacteria embedded in a matrix of alginate attack the lower respiratory tract [42]. Cystic fibrosis occurs as a result of a mutation in the CF transmembrane conductance regulator gene that encodes a cyclic AMP-regulated chloride ion channel. The mutation causes defective ion transport across epithelial cell surfaces in the upper airways, interfering with the removal of particles and microbial cells trapped in the overlying mucus and causing increased susceptibility to bacterial infection. Therefore, the airways of patients with CF are almost always infected with different bacterial species, but *P. aeruginosa* infection causes the greatest problem of morbidity and mortality [43]. *Pseudomonas aeruginosa* is the most common bacterial species that causes respiratory tract infection in CF patients and can be seen in about half of all cases and in up to 70% of adults [44]. Other pathogens such as *Staphylococcus aureus*, *Achromobacter xylosoxidans*, *Burkholderia cepacia* complex and *Stenotrophomonas maltophilia* have also been found to cause CF and

rhinosinusitis and the cultured organisms identified included *H. influenzae* (28%), *P. aeruginosa* (22%), *S. aureus* (50%), and fungi (22%). The presence of bacterial biofilms was linked to persistent mucosal inflammation after endoscopic sinus surgery [47]. Assessment of some chronic infections in the upper respiratory tract including recurrent tonsillitis and chronic rhinosinusitis in human clinical specimens suggests that both attachment and aggregated bacteria are present [48]. For instance, electron microscopy and culture were used to show that biofilms were associated with the mucosal epithelium of tonsils in 73% of tonsils removed for tonsillitis and 75% of those tonsils removed due to hypertrophic tonsils alone [49]. Calo *et al*. [42] found bacterial biofilms in recurrent and chronic infectious diseases of the upper respiratory tract (adenoiditis, tonsillitis, and chronic rhinosinusitis) and concluded that biofilms formation plays a role in

*DOI: http://dx.doi.org/10.5772/intechopen.89227*

chronic otitis media [46].

upper airway infections.

*3.2.1 Cystic fibrosis (CF)*

**3.2 Tissue-related infections**

are linked to biofilm formation [45].

*Combating Biofilm and Quorum Sensing: A New Strategy to Fight Infections DOI: http://dx.doi.org/10.5772/intechopen.89227*

rhinosinusitis [42]. In otitis media, infections may be as a result of both respiratory viruses and bacteria such as non-capsulated *Haemophilus influenza, Streptococcus pneumonia*, *Streptococcus pyogenes, Moraxella catarrhalis* and *Staphylococcus aureus*, triggering the appearance of polymicrobial biofilms [43].

The most cited reason for childhood visits to physicians is otitis media with effusion (OME) and is again one of the most reasons for antibiotic therapy in children. Even though OME is regarded as a sterile inflammatory process, current data using a chinchilla model suggest that viable bacteria are present in intricate communities referred to as mucosal biofilms [44]. It is interesting to know that intracellular *Haemophilus influenzae*, *Streptococcus pneumoniae*, *Staphylococcus aureus* and *Moraxella catarrhalis in situ* are found in adenoids from children going through adenoidectomy for the treatment of hypertrophic adenoids or chronic otitis media using Fluorescence in situ hybridization [45]. *Haemophilus influenzae* and intracellular *S. pneumoniae* have also been in middle ear mucosal biopsies in children with chronic otitis media [46].

Biofilms were seen in the sinus tissues of 72% of patients affected by chronic rhinosinusitis and the cultured organisms identified included *H. influenzae* (28%), *P. aeruginosa* (22%), *S. aureus* (50%), and fungi (22%). The presence of bacterial biofilms was linked to persistent mucosal inflammation after endoscopic sinus surgery [47]. Assessment of some chronic infections in the upper respiratory tract including recurrent tonsillitis and chronic rhinosinusitis in human clinical specimens suggests that both attachment and aggregated bacteria are present [48]. For instance, electron microscopy and culture were used to show that biofilms were associated with the mucosal epithelium of tonsils in 73% of tonsils removed for tonsillitis and 75% of those tonsils removed due to hypertrophic tonsils alone [49]. Calo *et al*. [42] found bacterial biofilms in recurrent and chronic infectious diseases of the upper respiratory tract (adenoiditis, tonsillitis, and chronic rhinosinusitis) and concluded that biofilms formation plays a role in upper airway infections.

### **3.2 Tissue-related infections**

### *3.2.1 Cystic fibrosis (CF)*

*Bacterial Biofilms*

**2.3 Protozoan biofilms**

**2.4 Virus involvement in biofilms**

been observed in *Cryptococcus neoformans* biofilms. Similarly, *Pneumocystis species* do not produce hyphal structures as part of their biofilms [32]. Hyphal formation is

Free-living protozoans are single celled eukaryotic organisms and are divided into amoebae, flagellates and ciliates. All the three protozoan groups have been found in fresh water biofilms. Although many different species are found in association with biofilms, their level of association differs. The protozoans *Cyclospora cayetanensis, Cryptosporidium* 

Viruses are obligatory intracellular parasites and are found in communities where cells in which they live are found. Viruses are, thus, found in biofilms com-

Many phages may produce polysaccharases or polysaccharide lyases. Some phages are also known to produce enzymes that degrade the poly-Q-glutamic acid capsule of *Bacillus* spp. [33]. Various structures including extracellular polymers and heterologous microbial cells may impede viral access to the bacterial cell surface. Phage may carry on their surfaces enzymes that degrade bacterial polysaccharides including those of biofilm structures. These enzymes are very specific and seldom act on more than a few closely related polysaccharide structures [34]. Numerous phages have been isolated which induce enzymes capable of degrading the exopolysaccharide of various Gram-negative bacterial genera. These include phage for biofilm-forming bacteria. It has been observed that the extracellular matrix of the biofilms does not

Many biofilms possess an open architecture with water-filled channels, which would allow the phage access to the biofilm interior [36]. As biofilms age and cells die and slough off, potential new viral receptor sites may become available. As bacteria excel at adapting to differing nutrient conditions, changes to the host cell surface could be expected with either loss or gain of possible phage receptors. A further factor which might influence phage retention within biofilms lies in the role of hydrophobic and electrostatic interactions. In the interaction of a coliphage with both hydrophobic and hydrophilic membranes, a critical factor in the retention of

In complex biofilms in natural environments, eukaryotic algae may also be present [38]. Under these circumstances algal cell lysis through viral action is also possible as many viruses for algal species have now been isolated and identified [39].

It is becoming progressively more accepted that biofilm formation is an important cause of morbidity in respiratory tract infections [40]. Biofilms may be involved in some respiratory infections, including ventilator-associated pneumonia, bronchiectasis, bronchitis, cystic fibrosis and upper respiratory airway infections [41].

Infectious diseases that affect the upper respiratory tract include otitis media,

sinusitis, tonsillitis, adenoiditis, pharyngotonsillitis, adenoiditis and chronic

*spp., and Toxoplasma gondii* have all been found in biofilm communities [22].

munities associated with the bacteria, fungi and protozoa they infect.

protect the bacterial cells from infection with phage T4 [35].

the phage was its iso-electric point [37].

**3.1 Upper respiratory tract infections**

**3. Biofilms in respiratory tract infections**

therefore, not a uniform feature of fungal biofilms.

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Cystic fibrosis (CF) is a protracted disease of the lower respiratory tract. The most frequent serious clinical complication in CF today is chronic endobronchial infection with *Pseudomonas aeruginosa*. *Pseudomonas aeruginosa* is a microorganism characterized by the capacity to produce large amounts of alginate and developed as a biofilm where micro-colonies of bacteria embedded in a matrix of alginate attack the lower respiratory tract [42]. Cystic fibrosis occurs as a result of a mutation in the CF transmembrane conductance regulator gene that encodes a cyclic AMP-regulated chloride ion channel. The mutation causes defective ion transport across epithelial cell surfaces in the upper airways, interfering with the removal of particles and microbial cells trapped in the overlying mucus and causing increased susceptibility to bacterial infection. Therefore, the airways of patients with CF are almost always infected with different bacterial species, but *P. aeruginosa* infection causes the greatest problem of morbidity and mortality [43]. *Pseudomonas aeruginosa* is the most common bacterial species that causes respiratory tract infection in CF patients and can be seen in about half of all cases and in up to 70% of adults [44]. Other pathogens such as *Staphylococcus aureus*, *Achromobacter xylosoxidans*, *Burkholderia cepacia* complex and *Stenotrophomonas maltophilia* have also been found to cause CF and are linked to biofilm formation [45].

### *3.2.2 Cystic fibrosis with chronic lung infections*

A major difficulty in this type of infection is contamination of lower respiratory secretions with the normal oropharyngeal flora, particularly as members of the normal flora (e.g. *Haemophilus influenzae*, *Staphylococcus aureus*, *Streptococcus pneumonia* and *Moraxella catarrhalis*) are common lung pathogens in CF [46, 47]. The incidence of bacterial lung infections in CF is high because the mucoid polysaccharidic material that accumulates on the respiratory epithelium due to the fact that impaired mucociliary removal in the bronchi of such patients favors biofilm formation. The capacity of *Pseudomonas aeruginosa* to form biofilms is believed to be the primary reason for its survival in the CF lung, despite a high inflammatory response and intensive antibiotic treatment [48]. Chronic airway infections cause an increase deterioration of lung tissue, a decline in pulmonary function and, finally, respiratory failure and death in cystic fibrosis (CF) patients [49].

### *3.2.3 Chronic obstructive pulmonary disease (COPD)*

The role of biofilms in patients with COPD has not been directly validated but has been hypothesized considering the evidence showing that the respiratory tracts of these patients are frequently colonized by pathogens. Murphy and Kirkham [50] have recently confirmed that biofilms do play a role in COPD where they identified major outer membrane proteins of Non-typeable *H. influenzae* during its growth as a biofilm. Even if direct proof of biofilm formation *in vivo* is lacking, biofilms may reasonably be considered to be involved in the vicious cycle of infection/inflammation leading to disease development in patients with COPD [51].

### *3.2.4 Non-cystic fibrosis bronchiectasis*

In bronchiectasis not due to cystic fibrosis, infections result in changes in the muscular and elastic components of the bronchial wall, which become distorted and expanded. Airways gradually become unable to clear mucus, leading to serious lung infections, which in turn cause more damage to the bronchi [52]. Recently biofilm formation has been demonstrated *in vivo* and is assumed to play a significant role in the pathophysiological cascade of the disease [53]. Bacterial biofilm formation by *Pseudomonas aeruginosa* or *Klebsiella pneumoniae* is common in bronchiectasis and could be an essential factor that makes infections in bronchiectasis obstinate. Other pathogens such as *Prevotella sp*., *Veillonella sp*. and *Neisseria sp*. have also been identified recently in patients with bronchiectasis to form biofilms [54].

### *3.2.5 Bronchitis*

Prolonged bacterial bronchitis may be caused by chronic infections of the respiratory tract. In children especially, the condition appears to be secondary to impaired mucociliary removal that produces an environment favorable for bacteria to become established, usually in the form of biofilms. The most commonly involved bacteria include *Haemophilus influenzae* (30–70%), *Moraxella catarrhalis and Streptococcus pneumonia* [55].

### *3.2.6 Diffuse pan-bronchiolitis*

Diffuse pan-bronchiolitis (DPB) is an unusual inflammatory lung disease of unknown etiology found in adult Japanese patients. With this disease, chronic

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also contributes to this matrix [60].

*Combating Biofilm and Quorum Sensing: A New Strategy to Fight Infections*

(Inflammation and congestion in the bronchioles of the lung) [56].

endobronchial infection with *Pseudomonas aeruginosa* biofilms leading to respiratory failure is common. It is a severe, progressive form of bronchiolitis

In device-related infections such as ventilator-associated pneumonia (VAP),

biofilms result in microbial persistence and reduced response to treatment. Biofilm formation within the first 24 h after intubation has been reported in 95% of endotracheal tubes [57]. Pathogens in both endotracheal tube biofilm and secretions accrued within the airways/endotracheal tubes in 56 to 70% of patients with VAP have been reported. *Pseudomonas aeruginosa* and *Acinetobacter baumannii* are the most common bacteria that colonize these

**3.4 Biofilm forming organisms associated with respiratory tract infections**

*Bordetella* and *Mycobacterium* species do play a role [59].

*3.4.1 Biofilms formed by Pseudomonas aeruginosa*

This section presents the role of biofilms in respiratory tract infections, with specific emphasis on the biofilms formed by *Pseudomonas*, *Staphylococcus*, and *Haemophilus*, the primary pathogens associated with respiratory tract infections [58] although additional important pathogens, including *Streptococcus pneumoniae*,

*Pseudomonas aeruginosa* is a recognized common pathogen in respiratory tract infections although other members of the genus *Pseudomonas* are able to form biofilms [7]. Respiratory infections caused by *P. aeruginosa* are a major globally clinical issue, especially for patients with chronic pulmonary disorders, such as those with cystic fibrosis (CF), non-CF bronchiectasis, severe chronic obstructive pulmonary disease (COPD) and ventilator-associated pneumonia [60]. This bacterium is a difficult opportunistic pathogen that readily forms biofilms on most surfaces [5]. The intricate steps of biofilm formation by *P. aeruginosa* are considered to be a developmental process. The stages of *P. aeruginosa* biofilm formation can be seen by several strategies. One easy technique is the scanning electron microscope (SEM) of *P. aeruginosa* grown on glass surfaces or tracheal explants. Biofilms form when planktonic *P. aeruginosa* bacteria get attached to a surface using adhesins such as type IV fimbriae and flagella, and begin to colonize. In this regard type IV fimbriae and flagella *P. aeruginosa* mutants are severely compromised in initiation of biofilm formation [58, 61]. Additionally, the process of surface translocation mediated by type IV fimbriae (twitching motility) is essential for initiation of biofilm formation by *P. aeruginosa* [58]. Most probable, twitching motility confers synchronized cell movement along the surface as well as cell–cell communications that lead to the formation of micro-colonies. The coordination of events for the initiation and formation of biofilms requires cell– cell interactions that are mediated by quorum sensing [62]. Following this, the micro-colonies mature into distinctive three-dimensional structures that pose the most severe scenario for clinical treatment. This structure is typically trapped in a matrix material that may be composed of protein, polysaccharide, or nucleic acid. Nonetheless, it has been proposed guluronic and mannuronic acids [63] are the major constituents of the biofilm matrix [64]. Recent data also suggest that DNA

*DOI: http://dx.doi.org/10.5772/intechopen.89227*

**3.3 Device-related infections**

devices [57].

endobronchial infection with *Pseudomonas aeruginosa* biofilms leading to respiratory failure is common. It is a severe, progressive form of bronchiolitis (Inflammation and congestion in the bronchioles of the lung) [56].
