Community and Hospital Acquired Bacterial Infections Flashcards
COMMON BACTERIAL VIRULENCE FACTORS (8)
Flagella (movement, attachment)
Pili (important adherence factors)
Capsule (protect against phagocytosis) i.e. Streptococcus pneumoniae
Endospores (metabolically dormant forms of bacteria) heat, cold, desiccation and chemically resistant i.e. Bacillus sp. and Clostridium sp.
Biofilms (organized aggregates of bacteria embedded in polysaccharide matrix – antibiotic resistant) i.e. Pseudomonas aeruginosa and Staphylococcus epidermidis
Exotoxins Neurotoxins, enterotoxins, pyrogenic toxins, tissue invasive exotoxins, misc exotoxins
Endotoxins
What endospores
(metabolically dormant forms of bacteria)
Example of bacteria that uses this as a virulence factor: capsule
Streptococcus pneumoniae
Example of bacteria that uses this as a virulence factor: endospores
Bacillus sp. and Clostridium sp.
Example of bacteria that uses this as a virulence factor: biofilms
Pseudomonas aeruginosa and Staphylococcus epidermidis
Example of bacteria that uses this as a virulence factor: neurotoxins
tetanus
Example of bacteria that uses this as a virulence factor: enterotoxins
staph aureus and E. coli
Example of bacteria that uses this as a virulence factor: pyrogenic exotoxins
staph aureus),
Example of bacteria that uses this as a virulence factor: tissue invasive exotoxin
staph aureus)
What type of bacteria produce endotoxins
Gram -ve
What are endotoxins functionally and where are they found
- Not a protein but the lipid A moiety of LPS (on the outer lipid bilayer)
Why can treating gram -ve bacterial infection worsen the condition
when bacteria lyse they release large quantities of LPS/ Endotoxin and this can lead to Septic shock
WHAT CONSTITUTES AN OUTBREAK?
A greater-than-normal or 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
HOW CAN AN OUTBREAK BE IDENTIFIED?
Surveillance systems provide an opportunity to identify outbreaks. Good and timely reporting systems are instrumental to identify them
What can you use to identify the strain in an outbreak?
PCR
What is haemolytic uremic syndrome characterised by? (3)
A triad of acute renal failure, haemolytic anaemia and thrombocytopenia
What causes haemolytic uremic syndrome
shiga toxin producing E coli
What toxin causes haemolytic uremic syndrome
shiga toxin producing E coli
What effect does Shiga toxin have to produce haemolytic uremic syndrome
Inhibits protein synthesis and affects the commensal gut flora
What is the virulence factor for EHEC?
Shiga toxin
What is the virulence factor for EAEC?
Aggregative adherence fimbriae
What does AAF do (3)
Allows strong adhesion to enterocytes, stimulates strong IL-8 response, allows biofilm formation
8 communicable diseases in Europe?
- Respiratory tract infections
- Sexually transmitted infections, including HIV and blood-borne viruses
- Food- and waterborne diseases and zoonoses
- Emerging and vector-borne diseases
- Vaccine-preventable diseases
- Antimicrobial resistance and healthcare-associated infections
LEGIONELLA PNEUMOPHILA: Gram +ve/-ve? Found where? Enters body how? Where does it grow in the body? What does it cause? Important virulence factor?
- Gram-negative - Lives in amoeba in ponds, lakes, air conditioning units, whirlpools etc.
- Infection route = inhalation of contaminated aerosols
- In humans L. pneumophila will infect and grow in alveolar macrophages
Légionnaires’ disease (legionellosis) Legionella pneumophila (Gram -) - Important virulence factor type IV secretion system Allows bacteria to replicate in vacuoles due to secretion of virulence factors, in a LCV (legionella containing vacuole)
MYCOBACTERIUM TUBERCULOSIS: Gram +ve/-ve? Whats different about this bacterium? Found where? Important virulence factor? Time for treatment to take effect?
- Gram-positive but with a very different cell wall – extra lipid layer which makes treatment more difficult
- Difficult to treat because it has this waxy layer on the outside and it reproduces slowly which means that antibiotics have a harder time killing it.
- Treatment of infections = antibiotics takes at least 6 months
CHLAMYDIA TRACHOMATIS:
Why is it difficult to get a cure for chalmydia?
What does it cause?
Obligate intracellular pathogen – cannot culture it outside host cell
Blindness eventually
NEISSERIA GONORRHOEAE: Gram +ve/-ve? Enters body how? Where does it grow in the body? What does it cause? Important virulence factor?
- Gram- negative diplococcus
STI - Establishes infection in the urogenital tract by interacting with non-ciliated epithelial cells
- Important virulence factors and traits:
pili and antigenic variation escape detection and clearance by the immune system
CAMPYLOBACTER SPECIES (MOSTLY C. JEJUNI): Enters body how? Who does it mainly affect? What does it cause? Important virulence factor? (5)
- Infection most likely through undercooked poultry
- Small children 0-4 years – highest risk group
- Virulence factors Adhesion and Invasion factors, flagella motility, type IV Secretion system, toxin
SALMONELLA: Gram +ve/-ve? Found where? Enters body how? Important virulence factor?
Gram +ve
- Undercooked poultry, enters when ate
Type III secretion systems (injection of proteins into human cells via needle like structure) encoded on pathogenicity islands (SPI):
Salmonella enterica
VIBRIO CHOLERAE:
Gram +ve/-ve?
What does it cause?
Important virulence factor?
Gram -ve
- Cholera is an acute, severe diarrheal disease
- Without prompt rehydration, death can occur within hours of the onset of symptoms
Type IV fimbria cholera toxin carried on a phages
- Cholera toxin activates cyclase enzyme in cells which makes a small nucleotide molecule which activates a transporter that pumps Cl ions out of the cell, Na and water also then go out of the cell to compensate – diarrhoea.
LISTERIA MONOCYTOGENES: Gram +ve/-ve? Risk group? Whats special about listeria? What does it cause? Important virulence factor?
Gram +ve
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
- It can spread from cell to cell without ever leaving the cell, hijacks actin to transport itself
5 most frequent HAIs?
surgical site infections, urinary tract infections, pneumonia, bloodstream infections and gastrointestinal infections
3 factors that contribute to the acquisition of HAIs>
INTERVENTION (what is done to treat someone)
DISSEMINATION (Hospital personnel travel from one patient to another, possibly transferring pathogens from patient to patient) CONCENTRATION (Patients are very close to one another and by definition, they’re unwell)
6 common HAIs?
Enterococcus faecium Staphylococcus aureus Clostridium difficle Acinetobacter baumanii Pseudomonas aeruginosa Enterobacteriaceae (E.coli, Klebsiella pneumoniae, Enterobacter sp.)
Enterococcus faecium : Gram +ve or -ve?
+ve
Staphylococcus aureus : Gram +ve or -ve?
+ve
Clostridium difficile: Gram +ve or -ve?
+ve
Pseudomonas aeruginosa : Gram +ve or -ve?
-ve
Enterobacteriaceae (E.coli, Klebsiella pneumoniae, Enterobacter sp.): Gram +ve or -ve?
-ve
Acinetobacter baumanii: Gram +ve or -ve?
-ve
What is Acinetobacter baumanii resistant to?
High drug resistant
What is Enterococcus faecium resistant to?
Vancomycin
What is Clostridium difficile resistant to?
Can establish infection due to previous AB treatment
What is Staphylococcus aureus resistant to?
Methicillin
What is Pseudomonas aeruginosa resistant to?
Multidrug resistant (fluoroquinolone e.g.)
What is Enterobacteriaceae resistant to?
Multi drug resistant
- Most frequent cause of community and hospital acquired UTI is?
E.coli
What are E.coli resistant to
cephalosporsins via extended spectrum beta lactamase
What are cephalosporins?
Target pathway?
Target protein?
Resistance?
- Are a class of beta-lactam antibiotics
- Target pathway inhibit peptidoglycan synthesis
- Target protein inhibit the activity of penicillin binding proteins (PBPs)
- Resistance to cephalosporins Extended spectrum beta-lactamase (ESBL) encoded on a plasmid – Mobile ESBL enzyme cleaves cephalosporin
What are carbapenems?
Target pathway?
Target protein?
Resistance?
- Are a class of beta-lactam antibiotics
- Target pathway inhibit peptidoglycan synthesis
- Target protein inhibit the activity of penicillin binding proteins (PBPs)
- Resistance to carbapenems carbapenemase enzyme, blakpc, encoded on a transposon (mobile genetic element) – enzyme cleaves carbapenem
What is methicillin?
Target pathway?
Target protein?
Resistance?
- Is a beta-lactam antibiotic
- Target pathway inhibit peptidoglycan synthesis
- Target protein inhibit the activity of penicillin binding proteins (PBPs)
- Resistance to methicillin Expression of additional PBP – PBP2A has low affinity for methicillin and can still function in the presence of the antibiotic – MRSA strains can synthesize peptidoglycan and survive in the presence of methicillin
What is vancomycin?
Target pathway?
Target protein?
Resistance?
- Target pathway inhibit PG synthesis
- Target binds to PG precursor
- Resistance to vancomycin multiple proteins / genes encoded on plasmid or transposon – Results in the synthesis of a different PG precursor meaning the vancomycin can’t bind to it properly
