**7. Exopolysaccharides**

Major components of the biofilm matrix are the exopolysachcarides produced by the *P. aeruginosa*. These exopolysaccharides include Alginate, and *Pel* polysaccharide and *Psl* polysaccharide. The *Pel* and *Psl* are associated with the non-mucoid strain [29] and Alginate is associated with the mucoid strains [30].

#### **8. Alginate**

*P. aeruginosa* produces alginate (an exopolysaccharide). This is a capsular polysaccharide and is overproduced in mucoid strains of *P. aeruginosa*. It is a high

**19**

Psuedomonas aeruginosa*-Associated Acute and Chronic Pulmonary Infections*

alginate is not the main component of the biofilm matrix [34].

altering the expression of *Pel* polysaccharide [36].

molecular weight polymer composed of monomers of D-mannuronic acids and β-1, 4 linked L-guluronic which are not repeating. Mutations in the negative regulator *MucA* is mainly caused to isolate the alginate-producing variants from chronically infected CF lungs [31]. Bacteria prevent itself from phagocytosis by this polymer acts as a physical barrier and an adherence factor, it gets oxygen free radicals resulting in enhancement of resistance of the biofilm against the host immune defense and antimicrobial agents. The mucoid strains to remain persistent and establish chronic infections in the CF lung by the influence of alginate [32, 33]. Wozniak et al. has demonstrated that in non-mucoid *P. aeruginosa* strains (PAO1 and PA14)

The *pel* and *psl* operon are encoded polysaccharide associated in biofilm formation in PAO1, ZK2870 and PA14, the non-mucoid *P. aeruginosa* strains. The main components of the extracellular polysaccharide matrix are constituted by these

The *pel* is an operon having 7 genes (PA3058 to PA3064), which encoding *Pel* polysaccharide biosynthetic proteins. The structure of *Pel* is unknown and it is a glucose-rich matrix polysaccharide and found to be involved in maintenance of biofilms and pellicle formation in *P. aeruginosa* PA14 strain. Sozzi and Smiley reported that biofilm formation is inversely regulated by cytoplasmic protein SadB1 result in

The *psl*, is an operon consist of 15 genes (PA2231 to PA2245), which encoding the *Psl* biosynthetic machinery. It is composed of a galactose-rich and mannose-rich polysaccharide. The exact structure of *Psl* has not been clarified yet. During attachment, *Psl* is holds and anchored bacteria during biofilm formation on the surface. *Psl* was associated in differentiation and maturation of *P. aeruginosa* biofilms in nonmucoid strains [37]. In *P. aeruginosa psl* and *pel* operons expresions are controlled by intracellular level of signaling molecule c-di-GMP (bis-(3′,5′)-cyclic-dimericguanosine monophosphate), the GacS/GacA/RsmZ and the Wsp chemosensory

*P. aeruginosa* produce rhamnolipids, the biosurfactants. Enzymes of the *rhlABC* operon synthesized the rhamnolipids. Rhamnolipids are required for biofilm formation by promoting the formation of microcolony at the initial phase of the biofilm formation. These are associated with to maintain channels and void spaces in

*The ability of P. aeruginosa*, to survive in indifferent environments including aquatic or marshes or even in low O2 or in very high temperatures (42°C) [44] resulting to withstand and survive on dry surfaces for more than 16 months by this pathogen [45]. It can colonize on dialysis machines, 'in-dwelling' appliances, sinks, floors, and toilet surfaces [46]. Immuno compromised host can be infected by *P. aeruginosa* by causing various clinical conditions, such as pneumonia, cystic fibrosis (CF), urinary tract infections, complications in clinical burns, and wounds [47, 48].

mature biofilms and also involved in biofilm dispersions [41–43].

**11. Infections caused by** *P. aeruginosa*

*DOI: http://dx.doi.org/10.5772/intechopen.93504*

**9.** *Pel* **and** *Psl* **polysaccharides**

polysaccharides [35].

system [38–40].

**10. Rhamnolipids**

Psuedomonas aeruginosa*-Associated Acute and Chronic Pulmonary Infections DOI: http://dx.doi.org/10.5772/intechopen.93504*

molecular weight polymer composed of monomers of D-mannuronic acids and β-1, 4 linked L-guluronic which are not repeating. Mutations in the negative regulator *MucA* is mainly caused to isolate the alginate-producing variants from chronically infected CF lungs [31]. Bacteria prevent itself from phagocytosis by this polymer acts as a physical barrier and an adherence factor, it gets oxygen free radicals resulting in enhancement of resistance of the biofilm against the host immune defense and antimicrobial agents. The mucoid strains to remain persistent and establish chronic infections in the CF lung by the influence of alginate [32, 33]. Wozniak et al. has demonstrated that in non-mucoid *P. aeruginosa* strains (PAO1 and PA14) alginate is not the main component of the biofilm matrix [34].

### **9.** *Pel* **and** *Psl* **polysaccharides**

*Pathogenic Bacteria*

**5. Flagella**

**Figure 2.**

The bacterial flagellum is protrudes from the cell body in the form a long, thin filament that consists of the basal body, the hook and the filament. The basal body is rooted in the cytoplasmic membrane having three rings the outer membrane lipopolysaccharide (L) ring, the peptidoglycan (P) ring and the cytoplasmic membrane supra-membrane (MS) ring. The hook is exposed to the surface and is a flexible universal joint between the filament and basal body. The filament is made of polymerized flagellin monomers (up to 20,000 subunits) capped by the flagellar

The initial attachment of the bacteria needs flagella and have involvement in maturation of biofilm. Klausen et al. reported that the initial microcolony formation is occurred by clonal growth and flagella are not involved in biofilm develop-

The type IV pili are best characterized, which are composed of the Pil A subunit in a form of a helical polymer. Hahn and Solow reported that these IV pili are localized to the poles of the bacterial cells and facilitate the adhesive properties of *P. aeruginosa* [25]. Type IV pili appear to be required for biofilm formation and host colonization. Cell aggregation and formation of microcolonies are promoted by Type IV pili [26, 27]. *P. aeruginosa* having three sets of type I fimbriae (*CupA, CupB* and *CupC* fimbriae) which assembled by the chaperone usher pathway. CupA fimbriae demonstrated as important for adherence to abiotic surfaces causing biofilm formation and auto-aggregation of small colony variants (SCV) in *P. aeruginosa* [28].

Major components of the biofilm matrix are the exopolysachcarides produced by the *P. aeruginosa*. These exopolysaccharides include Alginate, and *Pel* polysaccharide and *Psl* polysaccharide. The *Pel* and *Psl* are associated with the non-mucoid strain

*P. aeruginosa* produces alginate (an exopolysaccharide). This is a capsular polysaccharide and is overproduced in mucoid strains of *P. aeruginosa*. It is a high

[29] and Alginate is associated with the mucoid strains [30].

cap, FliD, which acts as mucin adhesion [22, 23].

*Different stages of the biofilm development. Modified from [21].*

ment in *P. aeruginosa* during attachment [24].

**6. Pili and type I fimbriae**

**7. Exopolysaccharides**

**18**

**8. Alginate**

The *pel* and *psl* operon are encoded polysaccharide associated in biofilm formation in PAO1, ZK2870 and PA14, the non-mucoid *P. aeruginosa* strains. The main components of the extracellular polysaccharide matrix are constituted by these polysaccharides [35].

The *pel* is an operon having 7 genes (PA3058 to PA3064), which encoding *Pel* polysaccharide biosynthetic proteins. The structure of *Pel* is unknown and it is a glucose-rich matrix polysaccharide and found to be involved in maintenance of biofilms and pellicle formation in *P. aeruginosa* PA14 strain. Sozzi and Smiley reported that biofilm formation is inversely regulated by cytoplasmic protein SadB1 result in altering the expression of *Pel* polysaccharide [36].

The *psl*, is an operon consist of 15 genes (PA2231 to PA2245), which encoding the *Psl* biosynthetic machinery. It is composed of a galactose-rich and mannose-rich polysaccharide. The exact structure of *Psl* has not been clarified yet. During attachment, *Psl* is holds and anchored bacteria during biofilm formation on the surface. *Psl* was associated in differentiation and maturation of *P. aeruginosa* biofilms in nonmucoid strains [37]. In *P. aeruginosa psl* and *pel* operons expresions are controlled by intracellular level of signaling molecule c-di-GMP (bis-(3′,5′)-cyclic-dimericguanosine monophosphate), the GacS/GacA/RsmZ and the Wsp chemosensory system [38–40].

### **10. Rhamnolipids**

*P. aeruginosa* produce rhamnolipids, the biosurfactants. Enzymes of the *rhlABC* operon synthesized the rhamnolipids. Rhamnolipids are required for biofilm formation by promoting the formation of microcolony at the initial phase of the biofilm formation. These are associated with to maintain channels and void spaces in mature biofilms and also involved in biofilm dispersions [41–43].

#### **11. Infections caused by** *P. aeruginosa*

*The ability of P. aeruginosa*, to survive in indifferent environments including aquatic or marshes or even in low O2 or in very high temperatures (42°C) [44] resulting to withstand and survive on dry surfaces for more than 16 months by this pathogen [45]. It can colonize on dialysis machines, 'in-dwelling' appliances, sinks, floors, and toilet surfaces [46]. Immuno compromised host can be infected by *P. aeruginosa* by causing various clinical conditions, such as pneumonia, cystic fibrosis (CF), urinary tract infections, complications in clinical burns, and wounds [47, 48].


#### **Table 2.**

*Infectious diseases caused by* P. aeruginosa *[55].*

*P. aeruginosa* is a common isolate from the patients who are hospitalized for more than a week. It is associated with high rate of mortality within 24 hours, infection can results in pneumonia, septicemia and urinary tract infection.

In sever chronic infection especially in patients with cystic fibrosis (CF), *P. aeruginosa* is involved. The main cause of mortality is *P. aeruginosa* lung infection in CF patients [49]. Murray et al. reported transmissible epidemic strains of *P. aeruginosa* emerged within the CF community. In earlier reports, CF patients considered to having their own strain of *P. aeruginosa* from their environment not from other infected individuals [50]. It is known as the Liverpool epidemic strain (LES) in recent research of UK due to the most common isolate recovered from CF patients [51, 52]. *P. aeruginosa* has a major focus in research as it is reporting to transmitted from a CF patient to non-CF parents, and causing significant morbidity in infected patients. *P. aeruginosa* is considered an opportunistic pathogen and this is an unusual characteristic to infect healthy individuals. Manchester and Midlands 1, Clone C are considered as predominant epidemic strains of *P. aeruginosa* [53]*.*

*P. aeruginosa* causes two types of respiratory infections. Acute (if patient have extended periods of ventilation) and chronic (if patient suffer from cystic fibrosis). Patients with these two types of infections in hospitalized settings are likely to be infected by this pathogen. Acute murine respiratory models used to identify a number of virulence factors in mutants of *P. aeruginosa*. The detailed studied is the TTSS proteins including *ExoS*, *ExoT*, *ExoU* and *ExoY*. Main contributor towards morbidity and mortality are *ExoS*, *ExoT* and *ExoU* as observed in a murein acute respiratory model (**Table 2**) [54].

The presence or absence of components of the TTSS can be correlated in human clinical results [55]. *P. aeruginosa* excreted a blue pigment Pyocyanin having antibacterial properties against other bacterial strains. The pyocyanin production also cause significant damage to lungs in murine acute respiratory infection, which demonstrated by an intranasal infection of adult CD-1 mice [49]. Quorum-sensing systems that are *LasI, LasR* [56], and *RhlI* [57] in *P. aeruginosa* contributing to acute infections. Intranasal infection in adult female Balb/c mice, and they also analyzed bacterial loads in lungs, liver and spleen after 16–18 hours of infection.

#### **12. Cystic fibrosis**

Cystic fibrosis trans-membrane conductance regulator (CFTR) mutation caused reduced chloride ion transport result in Cystic fibrosis (CF). It is a recessive genetic disorder. CF affected the development and functioning of various organs including immune system, pancreas and intestine, resulting a low life expectancy. The tissue damage is promoted in acute or chronic infections by constant stimulation of

**21**

Psuedomonas aeruginosa*-Associated Acute and Chronic Pulmonary Infections*

immune system effectors. In young CF patient *P. aeruginosa* is an important pathogen which lasts later stages. CF lung is an enriched with the oxygen gradients and nutrient. The oxygen gradients contribute the uniqueness in development of mucus layer and excessive consumption of the epithelial cells in CF lungs. *P. aeruginosa is* adaptable to many phenotypes in these types of conditions. A single isolate genome showed 68 mutations over the period of 90 months. The pathology in the lung in acute infections is due to the presence of elastase, flagella, LPS with O-side chains

*P. aeruginosa* contributed biofilms formation, produce rough LPS (no O-side chains), lack flagella, and overproduction of alginate during chronic infections. In chronic infections typically mucoid phenotype with lesser production of pyocyanin, pyoverdine, and elastase was observed. *The antibiotic pressure* causes *P. aeruginosa* to mutate from non-mucoid form to mucoid form. Small colony variants after a continued antibiotic exposure resulted in production of mannose-rich (*psl*) or glucose- (*pel*) polysaccharides. These are hyperpiliated, which are characterized as persistent to this specific phenotype. Liverpool epidemic strain (LES) reported as

The isolates of *P. aeruginosa* form CF changed their genome to get rid form acute virulence factors [56]. The loss of *LasR* function is one of the main genetic changes observed in *P. aeruginosa* isolates from CF patients. Many other acute infection models shown that because of deficiency in quorum-sensing, *lasR* mutants are less virulent than wild-type. Bacteria used this selective pressure of genetic change in genome to escape from host immune system in acute virulence in CF airways. An effective chronic CF isolate would be one, that isolate must lose its ability to be an effective acute infection isolate. *lasR* mutants have been examined for its advantages. The *LasR* mutants can grow on selected carbon and nitrogen sources as compared to wild-type.

Immune system is acting as natural defense mechanism to prevent the invasion of pathogens. PRRs (Porcine reproductive and respiratory syndrome) stimulus received by nonspecific innate system and respond the innate effectors responses;

• by the complement system with the membrane attack complex produced by

At the infection site the inflammatory response of effectors was induced by chemokines. Permanent tissue is damaged if continued stimulation of effectors by PAMPs (Pathogen associated molecular pattern) and virulence factors was

*P. aeruginosa* is a free-living and aerobic bacillus that is isolated from soil and water in most of cases. Intrinsic resistance in *P. aeruginosa* causing high mortality due to a broad spectrum resistance of antibiotics and is able to quickly to acquire

the complement proteins or by natural killer (NK)

*DOI: http://dx.doi.org/10.5772/intechopen.93504*

*P. aeruginosa* strains by over-production of pyocyanin.

proteases, and pyocyanin.

**13. Innate immune system**

• cell death or

induced [57].

**14. Antibiotic resistance**

• Phagocytosis by macrophages

#### Psuedomonas aeruginosa*-Associated Acute and Chronic Pulmonary Infections DOI: http://dx.doi.org/10.5772/intechopen.93504*

immune system effectors. In young CF patient *P. aeruginosa* is an important pathogen which lasts later stages. CF lung is an enriched with the oxygen gradients and nutrient. The oxygen gradients contribute the uniqueness in development of mucus layer and excessive consumption of the epithelial cells in CF lungs. *P. aeruginosa is* adaptable to many phenotypes in these types of conditions. A single isolate genome showed 68 mutations over the period of 90 months. The pathology in the lung in acute infections is due to the presence of elastase, flagella, LPS with O-side chains proteases, and pyocyanin.

*P. aeruginosa* contributed biofilms formation, produce rough LPS (no O-side chains), lack flagella, and overproduction of alginate during chronic infections. In chronic infections typically mucoid phenotype with lesser production of pyocyanin, pyoverdine, and elastase was observed. *The antibiotic pressure* causes *P. aeruginosa* to mutate from non-mucoid form to mucoid form. Small colony variants after a continued antibiotic exposure resulted in production of mannose-rich (*psl*) or glucose- (*pel*) polysaccharides. These are hyperpiliated, which are characterized as persistent to this specific phenotype. Liverpool epidemic strain (LES) reported as *P. aeruginosa* strains by over-production of pyocyanin.

The isolates of *P. aeruginosa* form CF changed their genome to get rid form acute virulence factors [56]. The loss of *LasR* function is one of the main genetic changes observed in *P. aeruginosa* isolates from CF patients. Many other acute infection models shown that because of deficiency in quorum-sensing, *lasR* mutants are less virulent than wild-type. Bacteria used this selective pressure of genetic change in genome to escape from host immune system in acute virulence in CF airways. An effective chronic CF isolate would be one, that isolate must lose its ability to be an effective acute infection isolate. *lasR* mutants have been examined for its advantages. The *LasR* mutants can grow on selected carbon and nitrogen sources as compared to wild-type.

#### **13. Innate immune system**

Immune system is acting as natural defense mechanism to prevent the invasion of pathogens. PRRs (Porcine reproductive and respiratory syndrome) stimulus received by nonspecific innate system and respond the innate effectors responses;


*Pathogenic Bacteria*

**Table 2.**

**Sr. no. Disease caused by** *P. aeruginosa* 1 Respiratory tract infections (RTI)

2 Bacteremia; septicemia

3 Otitis externa

5 Eyes infections

*Infectious diseases caused by* P. aeruginosa *[55].*

*P. aeruginosa* is a common isolate from the patients who are hospitalized for more than a week. It is associated with high rate of mortality within 24 hours, infection

6 Rare conditions like meningitis, perirectal infections and specific forms of osteomyelitis

4 Skin infection; ecthyma gangrenosum, pyoderma, folliculitis, acne vulgaris

In sever chronic infection especially in patients with cystic fibrosis (CF), *P. aeruginosa* is involved. The main cause of mortality is *P. aeruginosa* lung infection in CF patients [49]. Murray et al. reported transmissible epidemic strains of *P. aeruginosa* emerged within the CF community. In earlier reports, CF patients considered to having their own strain of *P. aeruginosa* from their environment not from other infected individuals [50]. It is known as the Liverpool epidemic strain (LES) in recent research of UK due to the most common isolate recovered from CF patients [51, 52]. *P. aeruginosa* has a major focus in research as it is reporting to transmitted from a CF patient to non-CF parents, and causing significant morbidity in infected patients. *P. aeruginosa* is considered an opportunistic pathogen and this is an unusual characteristic to infect healthy individuals. Manchester and Midlands 1, Clone C are considered as predominant epidemic strains of *P. aeruginosa* [53]*. P. aeruginosa* causes two types of respiratory infections. Acute (if patient have extended periods of ventilation) and chronic (if patient suffer from cystic fibrosis). Patients with these two types of infections in hospitalized settings are likely to be infected by this pathogen. Acute murine respiratory models used to identify a number of virulence factors in mutants of *P. aeruginosa*. The detailed studied is the TTSS proteins including *ExoS*, *ExoT*, *ExoU* and *ExoY*. Main contributor towards morbidity and mortality are *ExoS*, *ExoT* and *ExoU* as observed in a murein acute

The presence or absence of components of the TTSS can be correlated in human clinical results [55]. *P. aeruginosa* excreted a blue pigment Pyocyanin having antibacterial properties against other bacterial strains. The pyocyanin production also cause significant damage to lungs in murine acute respiratory infection, which demonstrated by an intranasal infection of adult CD-1 mice [49]. Quorum-sensing systems that are *LasI, LasR* [56], and *RhlI* [57] in *P. aeruginosa* contributing to acute infections. Intranasal infection in adult female Balb/c mice, and they also analyzed

Cystic fibrosis trans-membrane conductance regulator (CFTR) mutation caused reduced chloride ion transport result in Cystic fibrosis (CF). It is a recessive genetic disorder. CF affected the development and functioning of various organs including immune system, pancreas and intestine, resulting a low life expectancy. The tissue damage is promoted in acute or chronic infections by constant stimulation of

bacterial loads in lungs, liver and spleen after 16–18 hours of infection.

can results in pneumonia, septicemia and urinary tract infection.

respiratory model (**Table 2**) [54].

**12. Cystic fibrosis**

**20**

• by the complement system with the membrane attack complex produced by the complement proteins or by natural killer (NK)

At the infection site the inflammatory response of effectors was induced by chemokines. Permanent tissue is damaged if continued stimulation of effectors by PAMPs (Pathogen associated molecular pattern) and virulence factors was induced [57].

#### **14. Antibiotic resistance**

*P. aeruginosa* is a free-living and aerobic bacillus that is isolated from soil and water in most of cases. Intrinsic resistance in *P. aeruginosa* causing high mortality due to a broad spectrum resistance of antibiotics and is able to quickly to acquire

resistance genes by horizontal gene transfer. Fluoroquinolones, gentamicin and imipenem are restricted antibiotics as effective against *P. aeruginosa* and susceptibility to these antibiotics can vary between different strains. Bacterial infections are cured traditionally with the use of antibiotics and immune system is unable to have or eradicate this use of antibiotics.

Fluoroquinolones (ciprofloxacin) prevented DNA repair and replication [58]. Aminoglycosides, Beta-lactams (imipenam but not penicillins), 3rd and 4th generation cephalosporins, and fluoroquinolones are anti-pseudomonal drugs [59].

Colistin, is a drug having lesser side-effect profile, and mainly used against multi drug resistant strains (MDR) *P. aeruginosa* strains these days. The pattern or the use of antibiotic treatment now bettered towards the treatment of specific diseases including CF. The transmission of *P. aeruginosa* reduced by separation of infected and susceptible one and use of strict hygiene procedures [60].

The unavailability of the effective therapeutic option, the treatment of infections with pseudomonas is becoming difficult to deal a very few anti-pseudomonal drugs are being considered good for the treatment of emerging resistance strain, these include aminoglycosides beta-lactams, and fluoroquinolones [61–63].

The bactericidal MoA (mechanism of action) is significant for the survival by selection pressure for the fittest one. Antibiotic resistant bacteria are selected and propagated very well in the absence of the environmental resources competitions. Specific antibiotic resistance can be void of by the use of an alternative group of antibiotic. Bacteria have established active defense mechanisms which lead to MDR species such as methicillin-resistant *Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), Acinetobacter baumannii (A. baumannii),* or *P. aeruginosa* are promoted as MDR strains and are difficult to eradicate this opportunistic pathogens [64].
