Interactions can be symbiotic = close & often long-term interaction between two different species (mutualistic / commensal / parasitic)
Commensal = symbiotic relationship between two different species where one derives some benefit & the other is unaffected
Colonisation = when a microbe grows on or in another organism without causing any disease
Infection = the invasion & multiplication of microbes in an area of the body where they are not normally present, which usually leads to disease - may cause no Sx and be sub-clinical or may cause varying degrees of Sx and be clinically apparent
Extremes of age
Stress & starvation
Compromised barriers to infection
• Physical (anatomical)
• Biochemical (physiological)
Immunocompromised host
• Primary immunodeficiency (from birth)
• Secondary immunodeficiency (acquired after birth)
• Immunosuppression (iatrogenic from immune suppressing treatment)