community acquired bacterial infections Flashcards
name some virulence factors
- diverse secretion systems
- flagella (for movement, attachement)
- pili (adherence)
- capsule (protect against phagocytosis)
- endospores (metabolically dormant forms of bacteria)
- biofilms (aggregates of bacteria embedded in polysaccharide matrix - antibiotic resistant)
what are exotoxins?
toxins that damage biological system
name some different exotoxins and what they do?
- neurotoxins: act on nerves/ motor end plates e.g. tetanus
- enterotoxins: act on GIT e.g. S. Aureus
- pyrogenic exotoxins: stimulate release of cytokines e.g. S Pyogenes
- tissue invasive exotoxins: enzymes that allow bacteria to tunnel through tissue e.g. S Aureus`
what are endotoxins?
- only produced by gram -ve bacteria
- not a protein
- shed in steady amounts from living bacteria
- e.g. Lipid A in LPS from gram -ve
when treating a pt with gram -ve infection, why can ABs make them worse?
- bacteria lyses
- releases large quantities of LPS/ endotoxins
- septic shock
what is an outbreak?
sudden inc. in incidence of a disease in a particular place at a particular time
what is haemolytic-uraemic syndrome? what is it caused by?
- triad of: acute renal failure, HA, thrombocytopenia
- caused by EHEC (enterohaemorrhagic E. Coli)
- reservoir in cattle
what was the outbreak in Germany a result of?
- fusion of EHEC and EAHC strains to form EAHEC strain (entero-aggregative haemorrhagic E coli)
how can outbreaks be identified?
- possible epidemic case
- probably epidemic case
- confirmed epidemic case
define possible epidemic case
any person that has developed symptoms and has met a lab criteria
define probably epidemic case
any person that has met the above criteria and has been in epidemic country / consumed possible contaminated food / been in close contact w/ confirmed epidemic case
define confirmed epidemic case
any person meeting criteria for possible case AND has had strain isolated
how can outbreaks be identified by PCR?
- PCR showed that the isolate contained both aspects of EHEC and EAED
what does EAEC look like?
2 plasmids
- pAA-type plasmids
- ESBL plasmids
what does EHEC look like?
- prophage
- encoding shiga toxin
describe the shiga toxin structure
- AB5 subunit composition
- StxA is enzymatic portion, cleaves RNA –> inhibition of protein synthesis and might affect gut commensal bacteria
- StxB is pentamer that binds to hostt cell receptors
what are shiga toxins encoded on?
- bacteriophages
- contribute to horizontal gene transfer
- can be given to other bacteria types in phages
what can EAEC colonise?
larger and small bowel
affects gut flora
what is the EAECs virulence factor?
- aggregative adherence fimbriae (AAF)
- AAF required for adhesion to enterocytes
- stimulates IL-8 response
- AAF also allows biofilm formation
define outbreak
a greater than normal inc. in incidence of a disease with a particular infection in a given period of time or place or both
how do you identify an outbreak?
- surveillance
- good and timely reporting systems
- PCR
what are the most common communicable resp tract infections in EU?
- legionnaire’s disease
- TB
What bacteria causes Legionnaire’s? Found?
legionella pneumophila
lives in amoeba in ponds/lakes/ air conditioning
what is the route of infection and virulence factor of Legionnaire’s?
RoI: inhalation of aerosols, grows in alveolar macrophages
VF: type IV secretion systems
what bacteria causes TB? what’s the virulence factor?
Mycobacterium tuberculosis
extra lipid layer, can enter a dormant state for reactivation
what are the most common communicable STI’s in EU?
- chlamydia
- gonorrhoea
describe chlamydia
- chlamydia trachomatis
- gram -ve obligate intracellular parasite
- causes >3% of world’s blindness
describe gonorrhoea
neisseria gonorrhoeae
urogenital tract infection
infecting non-ciliated epithelial cells
what are the virulence factors of neisseria gonorrhoeae?
- pili
- antigenic variation mechanisms
what are the most common communicable food and water borne disease in EU?
- campylobacteriosis
- salmonellosis
- cholera
- listeriosis
what is campulobacteriosis? what group are at highest risk?
- campylobacter sp
- most infectious GI disease in EU
- small children highest risk group
what is the RoI of campylobacteriosis? VFs?
- infection route via uncooked poultry does not cause outbreaks
- VF: adhesion, invasion factors, flagella motility, T4 secretion systems, toxins
what cause salmonellosis? who is at highest risk?
- salmonella sp.
- common GI infection from undercooked poultry
- causes outbreaks
- highest risk in small children
what are the VF of salmonellosis?
- T3 secretion systems encoded on pathogenicity islands
- SPI1 for invasion
- SPI2 for intraceullar accumulation
what is cholera? What are the VF?
- virbrio cholera
- acute severe diarrhoeal disease
- VF: T4 fimrbia, cholera toxin, carried on phages
what does cholera toxin do?
inc. cAMP
opening of Cl- channels
expulsion of water from cells
what causes listeriosis? what is most at risk?
- listeria monocytogenes
- immunocompromised and pregnant people
what are the VF of listeriosis?
actin based cell motility
name 3 emerginf and vector borne diseases
- plague: yersia pestis
- Q fever: coxiella burnetti
- Smallpox, A virus: eradicated
what are 6 vaccine preventable diseases?
- diptheria
- invasive HA disease
- invasive meningococcal disease
- invasive pneumococcal disease
- pertissis
- tetanus
define antimicrobial
- interferes with growth and reproduction of a microbe
- antibiotics are antimicrobials
define antibacterial
agents that reduce or eliminate harmful bacteria
what are the stats about HAIs?
- 1/18 pt
- 3.2m a year
- costs around an extra 1bn/ year
what are the most frequent HAIs?
- surgical site infections
- UTIs
- pneumonia
- bacteraemias
- GI infections
what are the causes of HAIs?
- intervention: catheters, intubation, prophylactic antibiotics
- dissemination: carriers of infection from person to person
- concentration
what are the ESCAPE pathogens? what are they resistant to?
- Enterococcus faecium: vancomycin resistant
- S. Aureus: MRSA
- C. Diff: infect due to previous AB treatment
- Acinetobactor baumanii: highly drug resistant
- Pseudomonas aerugionosa: MDR
- Enterobacteriaceae: MDR
What are Cephalosporins? Target pathway? Target protein?
class of beta lactam antibiotics Pathway: inhibit peptidoglycan synthesis Protein: inhibit activity of penicillin binding proteins
what is the resistance mech to cephalosporins?
- Extended spectrum beta-lactamase (ESBL)
- ESBL enzyme cleaves cephalosporin
what are carbapenems?
same as cephalosporins
what is the mech of resistance to carbapenems?
- carbapenemase enzyme encoded on mobile genetic element
- enzyme cleaves carbapenem
what is the most frequent cause of community and HAI UTIs?
pathogenic E coli
what is the most frequent cause of bacteraemia by a gram -ve bacteria?
pathogenic E coli
what are the resistances in pathogenic E coli?
- 3rd gen cephalosporin resistance
- most resistance mediated by ESBLs
- still sensitive to carbapenems
what are the causes and risk groups for Klebiella pneumoniae?
- causes: UTIs and resp tract infection
- risk groups: immunocompromised
what are the resistances in Kelbiella pneumoniae?
- 3rd gen cephalosporins, fluoroquinolones and aminoglycosides
- CRKP: Carbapenem-Resistant pneumoniae
what are the people at risk for pseudomonas aeruginosa?
immunocompromised
what is methicillin? Target pathway? Target proteins?
- beta-lactam antibodies
- pathway: inhibit peptidoglycan synthesis
- protein: inhibit activity of penicillin binding proteins
what is the mech of methicillin resistance?
- expression of additional penicillin binding protein
- PBP2A has low affinity for methicillin, can still function in presence of antibiotic
- MRSA strians can synthesise peptidoglycan and can survive in presence of methicillin
what is the target pathway and target of Vancomycin?
Pathway: inhibit PG synthesis
Target: binds to PG precursor
what is the mech of vancomycin?
- multiple protein genes encoded on plasmid or transpoon
- results in synthesis of different PG precursor
what is VRE?
3rd most frequently identified cause of nosocomial blood stream infections
what is the resistance pathway of VRE?
- vancomycin resistance around 60%
- VRE synthesises a different peptidoglycan precursor that is not targeted by vancomycin
