Microbial Infection Flashcards
What does the innate immune system consist of?
Normal Microbiota, Physical barriers, chemical barriers and phagocytic cells
What is normal mircobiota and how does it offer protection?
These are the cells that live on the body. They offer protection by competing with other pathogens for colonisation sites. They may produce toxins to inhibit other micro-organisms. They may alter the pH making it an uninhabitable space for other micro-organisms.
Describe what the physical barriers are and how they offer protection
Skin - secrets sebum and fatty acids that reduce the pH and inhibit growth
Mucomuciliary clearance - Particals settle on stick mucus of respiratory tract epithelium. Debris is transported by cilia to oropharynx where it is swallowed. Low pH of stomach kills bacteria.
Flushing - i,e, of the urinary tract
Peristalsis - GI tract, prevents bacteria from becoming stationary
Describe what the chemical barriers are and how they offer protections
Mucus - antigenic structure
Antimicrobial proteins - Lysozyme, lactoferrin, Defensins
Gastric Acid
Plasma proteins - Complement, C-reactive protein (CRP), Mannose-binding lectin (MBL)
Transferrin
Name some phagocytes
Macrophages, Neutrophils
Monocytes
dendritic cells
Mast cells
Define Commensal
Micro-organsim which forms part of the hosts normal microbiota
Define pathogen
Micro-organism capable of causing an infection
Define virulence
Measure of the damage a pathogen causes to the host
What are the three types of pathogens?
Oligate - always associated with disease
Conditional - may cause disease if certain conditions are met
Opportunistic - Only infects hosts that are immunocompromised
Describe the steps on infection
Recognition, attachment and entery multiplication evasion of host defences shedding
How are infections established in healthy hosts?
- microbes attach and penetrate host body surfaces
- microbes introduces into hosts by biting arthropods
- Microbes introduced via skin wounds or animal
- Microbes introduced when host defences are down
What is tissue tropism and the factors that affect tissue tropism?
The microbes affinity for a specific tissue. Hosts can have broad tissue tropism . Factors that influence tissue tropism; Cell receptors, pH Transcription factors Local temperature Barriers
Where does the influenza virus attach?
Cilia and microvili on trachea epithelium
Where does vibrio cholerae attach?
Villi of intestinal epithelium
Where does helicobacter pylori attach?
Gastric Mucosa
What affects virulence?
Toxigenesis Antibiotic resistance Pilus formation Capsule Iron transport systems Adhesion factors Enzymes involved with breaking down host materials
Describe features of bacterial endotoxins
low toxicity, Part of Gram neg wall, lipopolysaccharides and they have a low specificity
Describe some features of bacterial exotoxins
Highly toxic, produces in both Gram pos and neg, can be converted into toxoids for vaccines
Name some important examples of antibiotic resistant diseases
Meticillin resistant staphylococcus aureus (MRSA)
Vancomysin resistant staphylococcus aureus (VRSA)
Multi-resistant mycobacterium tuberculosis
HIV
Malaria
Nam the three factors transmission relays on
Number of microorganisms spread, number required to infect host, their stability in environment
What is animal to human transmission called? Give some examples
Zoonoses, this can be via invertebrates (arthropods - malaria and yellow fever, Shellfish - hepatitis A and cholera) Via vertebrates (mammals -rabies and tape worm, Birds - salmonella)
What is fomite transmission?
Transmission via inanimate objects
What are nosocomial infections?
Infections acquired in a hospital stay
Name the types of human to human transmission
Respiratory/salivary
Fecal-oral
Venereal spread
