Relationships 2 Flashcards
What is entry?
Initial step in the infectious process
What is adhesion?
Adherence to host cells through specific interactions between molecules on the pathogen and molecules on these host cells
What are the microbial adhesion factors?
Bacterial- bacterial adhesions
-capsule, fimbrae, pili
Viral- viral adhesion
Viral capsid, viral membrane envelope
What is the function of fimbrae/pili?
Helps bacterial cells adhere to surfaces
F pili/sex pili enables conjugation/ dna transfer
What are the functions of viral caspid or membrand envelope adhesins?
Helps with adherence to specific proteins, glycoproteins or carbohydrate residues on the host cells surface
Virulence factors with similar functions to bacterial ashesins which facilitate adhesion to host cells
What natural environmen5 has microorganisms attached?
Rocks (in a stream) In roots of plants
What might Microorganisms attach to in medical environments?
- dental plaque leading to dental caries and gum disease
- Prosthetic heart valves leading to infective endocarditis, intracardiac abscess
- joint prosthesis leading to prosthetic joint infections
- internal catheters leading to catheter related infections
- medical device implants leading to blood stream infections
What might microorganisms attach to in the industrial environment?
Food and beverage industries leading to food safety problems
Water processing plants leading to water quality issues
Describe biofilm formation
Planktonic
- Attachment to surface
- Formation of mono layer and production of matrix
- Microcolony formation, multi-layer
- Mature biofilm, with characteristic “mushroom” formed of polysaccharide
What is tissue tropism?
Phenomenon by which certain host tissues preferentially support the growth and proliferation of pathogens.
Organ and tissue tropism reflects the ability of a given pathogen to infect a specific organ or a set of organs
What is colonization?
The process of infection continues with colonization, with or without damage to host tissue
What are the outcomes of colonization?
Commensalism- human microbiome, acquisition starting at birth
Infection- these microorganismmay be from exogenous or endogenous sources and have the potential to cause damage to host tissues
What are the conditions of colonization?
- Environments
2nutrient acquisition
What environmental factors contribute to colonization?
- pH( h pylori colonizers the stomach ph2-4)
- moisture (corynebacterium colonizers skin)
- temperature
- oxygen content
What factors of nutrient acquisition contribute to colonization?
Iron
- host cells
- transferrin andlactoferrin compete for iron acquisition
- pathogens
- siderphores
- breakdown of iron containing compounds
e. g. N meningitis is
- lactoferrin and transferrin receptors
- hemoglobinreceptors
What determines occurrence if disease?
Host, environment, and infectious agent
Give examples of agents
Viral/bacterial/ fungi/ reservoirs/ transmission route
What factors about host contribute to disease occurrence
Age, sex, immune status, genetic predispo, comorbidites
What factors of environment contribute to disease occurrence?
Tropical or temperate countries, sanitation levels, population density, socioeconomic status, vector exposure
Contrast infection vs disease
STI DONT EQUAL STD
infection- any situation where a microorganism gains entry, becomes established and is growing in a host, whether or not the host is yet harmed
Disease: growth of microorganism, invading pathogen or commensal results in host damage and production of specific signs
What are the bacterial virulence factors?
- Toxins.
- Flagella
- Glycocalyx
- Bacterial enzymes
What are toxins?
Bacterial proteins encoded by the bacterial chromosomal genes or extrachromosomal genes (plasmids, phages)
What are endotoxins?
Bacterial toxins secreted from the cells, which bind to specific cell receptors or structures causing a specific action on host cells or tissues
Site of action: neurotoxin, enterotoxin, cytotoxin
Give 2 examples of neurotoxins and there purpose
Clostridium botulinum and Clostrudium tetani
Botulinum toxin(Botox) in low concentrations is used for cosmetic and medical procedures
Before the advent of the DTP/. DTaP/ diphtheria and tetanus toxoids(DT), tetanus incidence rates= mortality rates
Give an example of an entertoxin and how it works
Entertoxin: cholera toxin
Enterotoxins are exotoxins
B sub unit binds to ganglioside receptor of epithelial cell
A subunit gets inside cell to activate G-protein and activate Adenylyl cyclase pathway
Causes release of water, sodium and chloride ions
What are endotoxins?
Toxic component of bacteria outer membranes
Lipopolysaccharide of gram negative bacteria. Usually has a general effect on host cells and tissues causing symptoms of inflammation and fever
The lipid component of endotoxins, lipid A, is responsible for the toxic properties of the LPS molecule
Give examples of endotox7ns
Salmonella spp: LPS—> gastroenteritis (food poisoning)
N. Meningitidis—> meningococcal meningitis or septicemia
Describe flagella as a bacterial virulence factor
Long, thin protrusions from the body
Function:
- bacterial motility
- bacterial adhesion
Describe glycocalyx (capsule/slime layer) as a bacterial virulence factor
Coating outside the cell wall of both gram positive and gram negative bacterial cells
Usually consists of polysaccharide but can also ne composed of other materials; glycoprotein etc.
Function- enhances pathogenicity by preventing phagocytosis by host immune cells
Describe bacterial enzymes as bacterial virulence factors
Bacterial proteins which can participate in catalytic reactions. These reactions may be helpful in bacterial cell invasion, host cell evasion and in some cases laboratory identification.
Invasins:
Hyaluronidase
Streptokinase
Staphylokinase
Hemolysins
Catalase
What is antigenic variation (discuss as a viral virulence factor)
Occurs mostly in certain types of enveloped viruses
Antigenic drift- a result of point mutations causing slight changes in surface glycoproteins
Antigenic shift- a major change in surface glycoproteins due to gene assortment
E.g. influenza virus
- orthomyxovirudae family
- single stranded negative sense RNA genome
- segmented genome(7-8)
