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Flashcards in Community Acquired Bacterial Infections Deck (32)
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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

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?

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?


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.

1. haemophilus influenzae (not to be confused with influenza virus)
2. pertussis (bordetella pertussis)
3. 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

1. Intervention- catheters, intubation etc
2. Dissemination - there are infected people in hospital and so will spread
3. Concentration


List the common HAI bacteria

Gram +ve:
Enterococcus faecium
Staph aureus
C diff
gram -ve:
Acinetobacter baumanii
Pseudomonas aeruginosa


Give 2 enzymes involved in cleaving antibiotics leading to AB resistance

1. Extended spectrum beta lactamase (cleaves cephalosporins)- common in ecoli
2.Carbapenemase enzyme (cleaves carbapenems)
3.Altered target- methicillin normally binds to penicillin binding protein on MRSA but MRSA has evolved with PBP2A which binds to it weakly,