Community Acquired Infection Flashcards
What are common virulence factors and its associated bacteria?
x Diverse secretion systems
x Flagella - for movement, attachment
x Pili - adherence
x Capsule - protect against phagocytosis
• i.e. Streptococcus pneumoniae
x Endospores - metabolically dormant forms of bacteria
• i.e. Bacillus sp. & Clostridium sp.
x Biofilms - aggregates of bacteria embedded in polysaccharide matrix (AB resistance)
• i.e. Pseudomonas aeruginosa & Staphyloc. epidermidis
What are exotoxins?
Toxins that damage biological systems
Give examples of exotoxins
x Neurotoxins - act on nerves of MEP
• i.e. Tetanus OR Botulinum toxins
x Enterotoxins - act on GIT
• i.e. infectious diarrhoea - Vibrio cholera, E.coli. Shigella dysenteriae, Campylobacter jejuni
• i.e. food poisoning - Bacillus cereus, Staph, aureua
x Pyrogenic exotoxins - stimulate release of cytokines
• i.e. Staph. aureus OR Strep. pyogenes
x Tissue invasive exotoxin - enzymes that allow bacteria to TUNNEL through tissue
• i.e. Staph. aureus, Strep. pyogenes, Clostridium perfringens
x Miscellaneous exotoxins - specific to certain bacteria, function NOT well understood
• i.e. Bacillus anthracis, Corynebacterium diphtheriae
What are endotoxins?
ONLY produced by gram -VE bacteria
NOT a protein
• it is a lipid A moiety of LPS
• shed in steady amounts from living bacteria
When treating a patient with a gram -VE bacteria infection, ABs can make it worse
• bacteria lyses = releases large quantities of LPS/endotoxins = septic shock
An example of an endotoxin?
Lipid A in LPS from gram-bacteria
Define outbreak
A sudden increase in the incidence of a disease in a particular place at a particular time
Give an example of an outbreak
E-COLI OUTBREAK!
Haemolytic-uraemic syndrome
• TRIAD of acute RF, haemolytic anaemia & thrombocytopenia
Caused by EHEC - enterohaemorrhagic E.coli
Outbreak was the result of a fusion of EHEC & EAHC strains to form the EAHEC strain
Difference between Possible vs. Probable vs. Confirmed Epidermic case?
Possible Epidemic Case
• any person that have developed the symptoms AND has met a laboratory criteria (e.g. isolation of agent)
Probably Epidemic Case
• Any person that has met the above criteria AND been in an epidemic country, consumed possibly contaminated food, been in close contact w. a confirmed epidemic case
Confirmed Epidemic Case
• Any person meeting criteria for possible case AND has had strain isolated
What is used to identify outbreak strains
PCR
Explain how outbreak strains are identified giving an example
Isolated can be screened by MULTIPLEX PCR for characteristic features of the outbreak strain
• can be done of stool samples for e.g. (e-coli)
• can determine if strain is outbreak strain or not
Give an example of indentifying an outbreak strain
Example - E-coli outbreak
• unique combination of genomic features containing characteristics from BOTH EHEC & EAEC suggested the new strain EAHEC
EAEC - 2 plasmids
• pAA-type plasmid - contain aggregative adhesion fimbrial operon
• ESBL plasmid - gene encoding for extended-spectrum beta-lactamases
EHEC - prophage encoding the Shiga toxin
• characteristic of EHEC strains
Explain the Shiga/Vero Toxin
Shiga toxins have an AB5 subunit composition
• StxA is the enzymatic portion - cleaves RNA = inhibits protein synthesis & might affect gut commensal bacteria
• StxB is the pentamer that binds to HOST CELL RECEPTORS
These toxins are encoded on bacteriophages
• contribute to horizontal gene transfer SO can be given to other bacteria types in phages
What is the virulence factor of EAEC
AAF - Aggregative Adherence Fimbriae
• required for adhesion to enterocytes & stimulates IL-8 response
• also allows a biofilm formation
Can colonise the larger & small bowel = affects gut flora
How can an outbreak be identifies?
x Surveillance
x Good and timely reporting systems
x PCR
2 examples of respiratory tract infections?
(1) Legionnaire’s Disease
• Legionella pneumophilia (gram -VE)
(2) Tuberculosis
• Mycobacterium tuberculosis (gram +VE)
Facts about Legionnaire’s Disease?
Location
RoI
Virulence Factor
(i) Location
• lives in amoeba (ponds, lakes, air conditioning)
(ii) RoI
• Inhalation of AEROSOLS
• grows in alveolar macrophages
(iii) Virulence factor
• type IV secretion systems
• legionella replicates in legionella containing vacuoles (LCVs) inside cells
Facts about Tuberculosis?
RoI
Virulence Factor
(i) RoI
• droplets/inhaled
(ii) VF
• has an EXTRA LIPID LAYER & can enter a DORMANT STATE for reactivation (makes treatment more difficult)
• has MDR (multi-drug resistance)
2 examples of STIs?
(1) Chlamydia
• Chlamydia trachnomatis (gram -VE)
(2) Gonorrhoea
• Neisseria gonorrhoeae (gram -VE)
Facts about Chlamydia?
Obligate IC pathogen
• can NOT culture it outside of host cell
Most common STI in Europe
Responsible for >3% of world’s blindness
Facts about Gonorrhoea?
RoI
VF
(i) RoI
• Urogenital tract infection
• Infects NON-CILIATED epithelial cells
(ii) VF
• Pili
• Antigenic variation mechanisms - escapes detection & clearance by I.S
5 examples of Food- & waterborne diseases and zoonoses?
(1) Campylobacter
• Campylobacter sp. (mostly C.jejuni)
(2) Salmonellosis
• Salmonella sp. (gram -VE)
(3) Cholera
• Vibrio cholera (gram -VE)
(4) Listeriosis
• Listeria monocytogenes (gram +VE)
Facts about Campylobacter?
RoI
VF
Most infectious disease in EU
• small children highest risk group
(i) RoI
• via. uncooked poultry BUT does NOT cause outbreaks
(ii) VF • adhesion & invasion factors • flagella motility • type IV secretion system • toxins
Facts about salmonella?
RoI
VF
(i) RoI
• common GI infection from uncooked poultry
• DOES cause outbreaks
• small children are highest risk
(ii) VF
• Type II secretion systems encoded on pathogenicity islands (SPI)
• SPI1 = invasion & SPI2 = IC accumulation
Facts about Cholera?
RoI
VF
(i) RoI
• acute severe diarrhoeal disease
(ii) VF
• Type IV fimbria
• cholera toxin (increases cAMP = opening Cl- channels = expulsion of water from cells)
• carried on phages
Facts about Listeriosis
VF
Risk groups include immunocompromised & pregnant people
(ii) VF
• actin-based cell motility
3 examples of emerging & vector-borne diseases?
(1) Plague
• Yersina pestis (gram -VE)
(2) Q fever
• Coxiella burnetti (gram -VE)
(3) Smallpox
• A VIRUS (eradicated)
6 examples of Vaccine-preventable diseases?
(1) Diphtheria
• Clostridium diphtheriae (gram+ve)
(2) Invasive HA disease
• Haemophilus influenzae (gram-ve)
(3) Invasive meningococcal disease
• Neisseria meningitides (gram-ve)
(4) Invasive pneumococcal disease
• Streptococcus pneumoniae (gram+ve)
(5) Pertussis
• Bordetella pertussis (gram-ve)
(6) Tetanus
• Clostridium tetani (gram+ve)
Facts about vaccination and the elimination of diseases?
Note; mass vaccination reduced by >97% the incidence of 9 infectious diseases and eliminated 2 of them (poliomyelitis and smallpox)
What are the 6 broad communicable diseases in Europe?
- Respiratory Tract Infections
- STI
- Food- & waterborne diseases and zoonoses
- Emerging and vector-borne diseases
- Vaccine-preventable diseases
- Antimicrobial resistance & HAI
