Community Acquired Bacterial Infections NEW Flashcards
Define virulence factor.
Molecules produced by pathogens that contribute to the pathogenicity of the organism
List some common bacterial virulence factors and include their function.
Flagella – movement and attachment
Pili – adherence factors
Capsule – protects against phagocytosis
Endospores – metabolically dormant forms of bacteria – they are heat, cold, desiccation and chemical resistant
Biofilms – organised aggregates of bacteria embedded in a polysaccharide matrix – antibiotic resistant
Give examples of bacteria that can form possess biofilms
Biofilms
Pseudomonas aeruginosa
Staphylococcus epidermidis
What are exotoxins?
A toxin released by a living bacterial cell into its surrounding
What are the five different types of exotoxin? Briefly describe what they do
Neurotoxins - act on nerves or motor endplate to cause paralysis
Enterotoxins - act on the GI tract to cause diarrhea and vomiting
Pyrogenic exotoxins - stimulate release of cytokines to cause rash, fever and toxic shock
Tissue invasive toxins - allow bacteria to destroy and tunnel through tissue
Miscellaneous exotoxin - specific to becterium/function not well understood
What is an endotoxin?
This is the lipid A part of lipopolysaccharide (LPS) that is found on the outer membrane of Gram-negative cells
Gram negative bacteria shed this all the time
NOTE: so ONLY Gram-negative cells can produce endotoxins
Why can treating patients with Gram-negative infection sometimes worsen their condition?
Antibiotics can cause lysis of the bacteria meaning that the endotoxins are released into the circulation in large quantities
This can trigger an immune response that leads to SEPTIC SHOCK
Define outbreak
A greater than normal or greater than expected number of individuals infected or diagnosed with a particular infection in a given time period, or a particular place, or both
How can an outbreak be identified?
Surveillance
Good and timely reporting systems are necessary
What type of bacterium is Legionella pneumophila and what is the route of infection?
Gram negative
It is transmitted through inhalation of contaminated aerosols and will infect and grow in alveolar macrophages NB human infection is the dead end
Name 2 respiratory tract community acquired bacterial infections
Legionella pneumophilia gram-
Mycobacterium tuberculosis gram +
What is the secretion system which is an important virulence factor for L. pneumophila?
Type IV secretion system
What feature of Mycobacterium tuberculosis makes it more difficult to treat?
It has a mycolic acid outer membrane – this prevents normal antibiotics from getting into the cell
Incredibly slow growing
State three bacterial sexually transmitted diseases including the species of bacteria that cause the diseases.
Chlamydia - Chlamydia trachomatis gram -
Syphilis –Treponema pallidum (dunno what gram)
Gonorrhoea –Neisseria gonorrhoeae gram -
What is a major consequence of Chlamydia in the developing world?
Blindness (due to eye infection)
How does Neisseria gonorrhoeae route of infection
urogenital:It interacts with non-ciliated epithelial cells in the urogenital tract
What are the important virulence factors of Neisseria gonorrhoeae?
Pili
Antigenic variation escapes detection and clearance by the immune system
Name 2 common GI bacterial infections?
Campylobacter jejuni
vibrio cholerae
Salmonella sp.
NOTE: Salmonella sp. can cause outbreaks whereas Campylobactertends to be sporadic cases
What is the route of infection of Campylobacter and Salmonella?
food- Ingestion of undercooked poultry
What are the important virulence factors of Vibrio cholerae?
Cholera toxin
Type IV fimbria
Explain how cholera toxin works.
It has A and B subunits
A is the active toxin
B allows entry of the toxin into the epithelial cell
The A subunit activates adenylate cyclase, thus increasing the production of cAMP
The cAMP then binds to CFTR (cystic fibrosis transmembrane receptor) and causes Cl- efflux
Water follows the ion movement so you get massive movement of water into the lumen of the intestine
What cells do listeria monocytogenes target?
They can enter non-phagocytic cells and cross tight barriers (e.g. BBB and maternal-foetal barrier)
Name some bacterial vector-borne diseases and the becteria that cause them
Q fever (Coxiella burnetti; Gram –)
Plague (Yersinia pestis; Gram-)
List some vaccine-preventable diseases.
- haemophilus influenzae (not to be confused with influenza virus)
- pertussis (bordetella pertussis)
- tetanus (clostridium tetani)
Give 2 examples of bacteria that produce neurotoxins
Tetanus or Botulinum toxins
Give examples of bacteria that produce the 2 sub-groups of enterotoxins
1) Infectious diarrhea
i. e. Vibrio cholera, Escherichia coli, Shigella dysenteriae and Campylobacter jejuni
2) Food poisoning i.e. Bacillus cereus or Staphylcoccus aureus
Give 2 examples of bacteria that produce pyrogenic exotoxins
Staphylcoccus aureus or Streptococcus pyogenes
What are the 6 catagories of 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
Differentiate antimicrobial, antibacterial and antibiotic
antimicrobial- interferes with growth and reproduction
antibacterial- reduce/eliminates bacteria
antibiotic is a type of antimicrobial
Explain why patients are at risk of HAI
- Intervention- catheters, intubation etc
- Dissemination - there are infected people in hospital and so will spread
- Concentration
List the common HAI bacteria
ESCAPE
Gram +ve: Enterococcus faecium Staph aureus C diff gram -ve: Acinetobacter baumanii Pseudomonas aeruginosa enterobacteriaceae
Give 2 enzymes involved in cleaving antibiotics leading to AB resistance
- Extended spectrum beta lactamase (cleaves cephalosporins)- common in ecoli
- Carbapenemase enzyme (cleaves carbapenems)
- Altered target- methicillin normally binds to penicillin binding protein on MRSA but MRSA has evolved with PBP2A which binds to it weakly,
