A proof-of-concept model for the identification of the key events in the infection process with specific reference to Pseudomonas aeruginosa in corneal infections

Figures & data

Fig. 1.  Pathway-based conceptual model of the infection process. We have used the following colour code to map the different components of the epidemiological triangle, colour coding the adverse outcome (intersection) separately: orange: exposure (environment and interactions); blue: the invasion process by the microorganism; red: host defences based on time of occurrence; and green: adverse outcome (level of infection).

Table 1 Stages in infectious process and predisposing risk factors

I. Exposure
1. Environment
i. Contact lenses
a. Type of lenses
b. Case replacement frequency
c. Extensive wear
ii. Type of sterilizer → resistant agents/ probability of P. aeruginosa developing resistance
2. Host/environment
i. Hygiene
ii. Socio-economic factors
3. Agent/environment
i. Swim
ii. Swarm
iii. Biofilms on lenses
II. Internal exposure/barrier function impairment
1. Eye damage
2. Tear fluid malfunction
3. Inhibition of corneal shedding
4. Thinning of epithelia
5. Hypoxia
III. Molecular initiating event/innate immunity
1. LPS (lipopolysaccharide) – TLR4 (Toll-like receptors)
2. ExoU(not ExoS at eye strains) – TLR4, TLR2
3. Flagella – TLR5
4. Type IV pili (twitching motility)
IV. Adverse outcome pathway/adaptive immunity
1. Virulence factors
2. Quorum sensing
3. Types I–VI secretion systems
4. Cellular response (T cell)
5. Humoral response (antibody)
V. Adverse outcome (infection)
1. Resolved
2. Mild
3. Moderate
4. Severe