Infectious Diseases part 1 Flashcards
Through which pathways can microbes enter the host?
- Through breaches in the skin, by inhalation or digestion, or by sexual transmission.
Why skin infections caused by less virulent organisms than mucosal infections?
- Respiratory, GI/GU tracts infections caused by virulent organisms which can damage and penetrate the epithelial barrier.
- Skin infections occasionally occur by less virulent organisms that breach the skin through damaged sites.
What features provide the skin to serve as a good barrier?
- Dense, Keratinized Layer.
- Defensins and anti-microbial FA.
- Low pH (less than 5.5)
When GI Tract infections occur?
- GI tract infections usually occurs when the local defenses are weakened - low gastric acidity, antibiotics session (alters normal flora), obstructions or stalled peristalsis.
- Viruses that can enter through the GI tract are lack envelopes because the bile and digestive enzymes inactivates the enveloped viruses.
In which ways enteropathogenic bacteria causes GI diseases?
- Toxin production in food: S.aureus for example can grow in food and release enterotoxins that cause food poisoning without any bacterial growth in the gut.
- Adhesion, local proliferation and toxins production in the host: E.coli and V.cholera for example, causes the epithelial cells to secrete large volumes of fluid resulting in watery diarrhea.
- Invasion: Shigella & Salmonella for instance, invade locally and damage the lamina propria, causing ulceration, inflammation and hemorrhage - clinically manifested as bloody diarrhea.
What are the normal defenses within the GI tract?
- Low pH.
- Mucus.
- Bile detergents and lytic pancreatic enzymes.
- Defensins (anti-microbial peptides).
- Normal Flora.
- Secreted IgA.
True or false:
“the distance that microbial particles travel into the respiratory system in inversely to their size”
True - Particles bigger than 5micrometer cannot reach the alveoli.
How influenza virus evade the defenses of the respiratory tract?
- Influenza viruses possess hemagglutinin proteins that can bind sialic acid on epithelial cells. this attachment induces the host cell to engulf the virus, leading to viral replication within the host cell.
How Haemophilus influenza, Mycoplasma Pneumonia and Bordetella pertussis act to disturb the normal function of the respiratory tract?
These bacteria release toxins that paralyze the cilia.
A patients of yours is suffering from pneumonia caused by streptococcus pneumonia and another patients have the same phenotype but the tests reveal that the infecting agent is S.aureus.
additionally this 2 patients telling you that they had flu 4 weeks ago. What can it be?
Pneumonia secondary to influenza. the viral infection caused a loss of protective ciliated epithelium.
What is the common way by which bacteria invade the GU tract?
- External invading through the urethra.
- Because of anatomic differences, women are more susceptible to urinary tract invasions.
Can Urinary tract infections spread up from the bladder to the kidney?
- Yes, can be the cause of acute/ chronic pyelonephritis.
What protects the urinary tract from getting infected?
- The regular flushing of the urinary tract with urine.
- Obstruction of urinary flow or reflux can interfere normal defenses and increase susceptibility to urinary tract infections.
What are the main functions of the microbiome?
- Enables absorption of certain nutrients.
- Compete with colonization of pathogenic microbes.
- Maintaining the integrity of the epithelium and the normal functioning of the immune system.
Where is the highest diversity of the bacterial microbiome?
- In the oral cavity and in the stool.
- Intermediate in the skin.
- Least in the vagina.
