Week 8 Microbes Flashcards
5 stages of infection
- Incubation period
- Prodromal Period (not all illness have this period)
- Specific Illness Period
- Decline
- Convalescence
5 Factors affecting incubation period
- Microbial inoculum (dose)
- Route of inoculation
- Rate of replication of microbe
- Host susceptibility
- Host immune response
What is latent infection?
After convalescence
Microorganism remains in patient’s body, when immune system of host declines -> maybe reactivation
2 Types of microbes generally
- Pathogens
2. Non-pathogens - do not cause disease
2 Immunities
- Innate immunity - at birth, no memory
2. Acquired immunity - organism-specific
6 Basic steps of pathogenesis of infection
- Encounter
- Entry
- Spread - local and beyond
- Multiplication
- Damage
- Outcome
What is virulence factor?
Micorbial factors that enhance the organism’s ability to colonize, invade and multiply inside host
The chain of infection
- Infectious agent
- Reservoir
- Exit Portal
- Transmission
- Entry Portals
- Susceptible Host
Major routes of transmission
- Inhalation
- Ingestion
- Contact - direct/indirect
- Bites/cuts/wounds
- Iatrogenic - involves blood transfusion/transplantation
3 Types of bacteria according to staining properties
- Gram-positive bacteria (violet/dark blue)
- Gram-negative bacteria (red/pink)
- Cell wall-deficient bacteria
Common diseases caused by Gram-negative bacteria
- Urinary tract infection
- GI tract infection
- Sexually-transmitted diseases
- Zoonoses
4 types of bacteria morphologically
- Cocci - spherical
- Bacilli - rod-shaped
- Spirochaetes - curved
- Cell wall-deficient
Important component of bacterial cell wall
only present in bacteria
Peptidoglycan
Function: give structural integrity in bacterial cell
Difference between Gram-positive and Gram-negative bacterial cell wall
Gram-positive bacteria: thick peptidoglycan layer
Gram-negative bacteria: thin peptidoglycan layer -> lipid outer membrane (less permeable to antibiotics)
4 types of bacteria according to oxygen requirement
- Strictly aerobic
- Facultatively anaerobic
- Microaerophilic
- Strictly anaerobic
4 Pathogenic mechanisms of bacteria
- Invasion
- Toxin
- Immunopathology
- Oncogenesis
6 Infectious agents
- Helminths
- Protozoa
- Fungi
- Bacteria
- Virus
- Prion
5 Mechanisms of action of antibacterial agents
- Peptidoglycan Synthesis
- Protein Synthesis
- Nucleic acid Synthesis
- Folate Synthesis
- Cell membrane integrity
What is viraemia?
Presence of virus in blood
Virus replication cycle
- Attachment
- Penetration
- Uncoating
- Viral protein synthesis
- Viral nucleic acid replication
- Virus assembly
- Viral release
3 Pathogenic mechanisms of virus
- Cytolysis
- Immunopathology
- Oncogenesis - induction of tumours
2 General ways of viral diagnosis
- Detect the virus
2. Detect the host antibody response
What is prion?
Infectious protein
Medically important groups of parasites
- Protozoa
- Helminths: nematodes, trematodes, cestodes
- Arthropods
Life cycle of parasites
- Agent: parasite itself
- Vector: for transmission
- Intermediate host: harbours asexual stage
Definitive host: harbours sexual stage (mature)
Microorganism causing malaria
Protozoa: Plasmodium spp. (genus)
What are relapse and recrudescence?
Relapse:
recurrence of symptoms after complete initial clearing of parasitaemia
Recrudescence:
recurrence of symptoms after initial parasitaemia is reduced to a very low level (not completely cleared)
Vector for natural transmission of malaria
Female Anopheles mosquitoes
