Microbiology 3: Community acquired and hospital acquired bacterial infections Flashcards
List the important virulence factors
1) Diverse secretion systems
2) Flagella (movement, attachment)
3) Pili (important adherence factors)
4) Capsule (protect against phagocytosis)
- Streptococcus pneumoniae
5) Endospores (metabolically dormant forms of bacteria)
- heat, cold, desiccation and chemical resistant
- Bacillus sp. and Clostridium sp.
6) Biofilms (organized aggregates of bacteria embedded
in polysaccharide matrix – antibiotic resistant)
- Pseudomonas aeruginosa
- Staphylococcus epidermidis
6) Exotoxins
7) Endotoxins
What are the different types of exotoxins?
1) Neurotoxins (act on nerves or motor endplate to cause paralysis)
- Tetanus or Botulinum toxins
2) Enterotoxins (act on the GI tract)
1) Infectious diarrhea
- Vibrio cholera, Escherichia coli, Shigella dysenteriae
and Campylobacter jejuni
2) Food poisoning
- Bacillus cereus or Staphylcoccus aureus
3) Pyrogenic exotoxins (stimulate release of cytokines)
- Staphylcoccus aureus or Streptococcus pyogenes
4) Tissue invasive exotoxin (allow bacteria to destroy and tunnel through tissue)
- enzymes that destroy DNA, collagin, fibrin, NAD,
- red or white blood cells
- Staphylococcus aureus, Streptococcus pyogenes, Clostridium perfringens
5) Miscellaneous exotoxin (specific to a certain bacterium and/or function not well understood)
- Bacillus anthracis and Corynebacterium diphtheriae
Describe endotoxins
Gram +ve vs Gram -ve bacteria
- Only produced by Gram-negative bacteria
- Not a protein: lipid A moiety of lipopolysaccaride
- Shed in steady amounts from living bacteria
Treating a patient who has a Gram-negative infection with antibiotics can sometimes worsen condition.
When bacteria lyse they release large quantities of LPS/ Endotoxin–> Septic shock
Define septic shock
Sepsis that results in dangerous drops in blood pressure and organ dysfunction is called septic shock. It is also referred to as endotoxin shock because endotoxin often triggers the immune response that results in sepsis and shock. But you should remember that also different effectors molecules in Gram-positive bacteria or even fungi can trigger this adverse immune response – so the term septic shock is inclusive
Define an outbreak of infectious disease
Is a greater than normal or than greater than expected number of individuals infected or
diagnosed with a particular infection in a given period of time, or a particular place, or both
E.g unusual time and number
Read examples -ABS/Slides. you don’t need to know in detail
Things to know: To define an outbreak, you must know the cause, characteristics, scale, time-frame, source, illness, involvement of different strains, symptoms to look for etc
• Once you know the genome of the bacterium, you can use PCR to detect the outbreak strain in stool samples etc
How can an outbreak be identiifed?
- Surveillance systems provide an opportunity to identify outbreaks – report to a central system to identify the spread
- Good and timely reporting systems are instrumental to identify outbreaks
List 6 communicable diseases in Europe?
1) Respiratory tract infections
2) Sexually transmitted infections, including HIV and blood-borne viruses
3) Food- and waterborne diseases and zoonoses
4) Emerging and vector-borne diseases
5) Vaccine-preventable diseases
6) Antimicrobial resistance and healthcare-associated infections
Describe 3 types of respiratory tract infections, what bacteria cause it and explain the route of infection
Influenza (animal, avian)
Legionnaires’ disease - Legionella pneumophilia (gram -ve)
- Lives in amoeba in ponds, lakes, air conditioning units, whirlpools,…
- Infection route: inhalation of contaminated aerosols
- In humans L. pneumophila will infect and grow in aveolar macrophages
- Human infection is “dead end” for bacteria
- Important virulence factor type IV secretion system: which allows secretion of effector proteins to the cytoplasm of host cells, which allows legionella to replicate in a legionella containing vacuole within the host cell.
Tuberculosis - Mycobacterium tuberculosis (gram +ve)
- very different cell wall: extra lipid layer makes treatment more difficult
- M. tuberculosis can enter a dormant state. Latent TB - evidence of infection by immunological tests but no clinical signs and symptoms of active disease
- A mixture of active and latent TB makes it difficult to treat.
- Treatment of infections: with antibiotics BUT TAKES at least 6 months. 72% success rate of treatment of new cases. Treatment success rate for second infection is 54%. Multi drug resistant (MDR) treatment success rate in is 32%.
List 5 types of Sexually transmitted infections, including HIV and blood-borne viruses and describe two of them.
- Chlamydia trachomatis infection (Gram -ve)
- Gonorrhoea (Neisseria gonorrhoeae) (Gram -ve)
- Hepatitis B virus infection
- Hepatitis C virus infection
- HIV/AIDS
- Syphilis (Treponema pallidum) (Gram -ve)
Chlamydia trachomatis:
- obligate intracellular pathogen cannot culture it outside host cell
- Most frequent STI in Europe –> 410.000 cases/year. Infection likely higher due to underreporting
- Other parts of the world –> Eye infection:
84 million people infected and about 8 million visually impaired. It is responsible for more than 3% of the world’s blindness.
Neisseria gonorrhoeae
- Gram- negative diplococcus
- Establishes infection in the urogenital tract by interacting with non-ciliated epithelical cells
- Important virulence factors and traits:
1) pili and antigenic variation escape detection
and clearance by the immune system
List and describe 4 types of food- and waterborne diseases and zoonoses.
Campylobacter sp.
- Most commonly reported infectious GI disease in the EU
- Usually sporadic cases and not outbreaks
- Small children 0-4 years – highest risk group
- Infection most likely through undercooked poultry
Virulence factor:
- Adhesion and Invasion factors,
- Flagella motility,
- Type IV Secretion system, Toxin
Salmonella sp.
- One of the most common GI infections in the EU
- Undercooked poltry
- Outbreaks
- Highest infection rate in small children (0-4 years)
- Important virulence determinant: Type III secretion systems (encoded on pathogenicity islands
(SPI)) There are two islands
SPI1: is required for invasion
SPI2: intracellular accumulation
Vibrio cholerae
- Cholera is an acute, severe diarrheal disease
- Without prompt rehydration, death can occur
within hours of the onset of symptoms
- Latest epidemic in Haiti
- Oct 2010 – ongoing
- As of 2018 > 800.000 cases with ca. 10.000 death
- Important virulence factor:
1) type IV fimbria
2) cholera toxin carried on a phages
- This type IV fimbria (TCP phage) serves not only as a colonization factor, but also as a receptor for the CTX phage encoding cholera toxin
- Both bacteriophages can integrate into the bacterial genome and form episomal
replication intermediates, and this is dependent on secretin (which is encoded within the bacterial genome
- This is another example of one phage strain infecting the other
- Cholera toxin: makes the cell produce cyclic AMP, which activates transporters leading to efflux of chloride ions with water movement following
- Newer strains have more virulence factors
Listeria monocytogenes
- Risk group immuno-compromised, elderly, pregnant and their fetus
- Listeria can enter non-phagocytic cells and cross three tight barriers
Intestinal barrier, Blood / brain barrier and Materno / fetal barrier
- Research on Listeria has allowed us to understanding the concepts in cell biology such as actin based cell mobility. See cell motility tutorial.
List 3 emerging and vector-borne diseases
Plague (Yersinia pestis; Gram -ve)
Q fever (Coxiella burnetti; Gram -ve)
Small pox - eradicated
List 6 vaccine preventable diseases
- Diphtheria (Clostridium diphtheriae Gram +ve)
Invasive Haemophilus influenzae disease (Gram -ve)
Invasive meningococcal disease (Neisseria meningitidis Gram -ve)
Invasive pneumococcal disease (IPD) (Streptococcus pneumoniae Gram +ve)
Pertussis (Bordetella pertussis Gram -ve)
Tetanus (Clostridium tetani Gram +ve)
Define antimicrobial
interferes with growth & reproduction of a ‘microbe’
Define antibacterial
commonly used to describe agents to reduce or eliminate harmful bacteria
Define antibiotic
Type of antimicrobial used as medicine for humans, animals originally referred to naturally occurring compounds
