Bacterial infections Flashcards
define outbreak
a sudden increase in the incidence of a disease in a
particular place at a particular time
eg:
Haemolytic- uraemic syndrome (type of E.coli infection)
triad of acute renal failure, haemolytic anaemia and thrombocytopenia.
The outbreak was the result of a fusion the EHEC and the EAHC strains to form the EAHEC strain
explain how outbreaks are identified
Identification of an outbreak:
oSurveillance.
oGood and timely reporting systems.
oPCR
define community acquired infections
An infection acquired in the community. In contrast to a nosocomial (hospital-acquired) infection
name the pathogens that cause food and waterborne diseases and zoonoses and their virulence factors
Campylobacteriosis–Campylobacter jejuni (Gram-)
causes gastroenteritis
Virulence factors:
flagella motility, Type IV secretion systems, toxins
Salmonellosis–Salmonella sp. (gram-ve):
virulence factors:
Type III secretion systems encoded on pathogenicity islands.
both result from undercooked poultry but salmonella causes outbreaks unlike c. jejuni
Cholera – Vibrio cholera (gram-ve):
Virulence factors:
-Type IV fimbria, cholera toxin (increased cAMP–>opening of Cl- channels and expulsion of water from cells), carried on phages.
Listeriosis – Listeria monocytogenes (gram+ve):
Virulence factors:
uses actin polymerisation and depolymerisation to allow intracellular motility.
name the pathogens that cause emerging and vector borne diseases and their virulence factors
Plague– Yersina pestis (Gram -), vector: rodents / fleas
Q fever–Coxiella burnetti (gram-ve). vector: cattle/ domestic animals
name the pathogens that cause vaccine preventable diseases and their virulence factors
Diphtheria – Clostridium diphtheriae (gram+ve).
Invasive HA disease- Haemophilus influenzae (gram-ve).
Invasive meningococcal disease– Neisseria meningitides (gram-ve).
Invasive pneumococcal disease– Streptococcus pneumoniae (gram+ve)
Pertussis– Bordetella pertussis (gram-ve).
Tetanus–Clostridium tetani (gram+ve).
name the pathogens that cause respiratory tract infections and their virulence factors
Legionnaire’s disease–Legionella pneumophila (Gram-)
-virulence factor: Type IV secretion system, legionella replicates in the legionella containing vacuoles (LCVs) in cells.
Tuberculosis— mycobacterium tuberculosis (Gram+)
-Virulence factor: extra lipid layer containing mycelia acid, and can enter dormant state.
Influenza
what are the main types of bac. virulence factors
-Secretion systems (type IV, III) - allows them to get proteins from the cytoplasm of their cells into host cells ie secretion of effector proteins.
-Flagella (for movement, attachment.)
-Pili (for adherence)
-Capsule (S. pneumoniae) (protect against phagocytosis)
-Endospores (Clostriduim sp., Bacillus sp.) (metabolically dormant forms of bacteria)
-Exotoxins:
o neurotoxins (Tetanus and botulinum toxin)-
o enterotoxins (
* infectious diarrhoea:V.cholera, C.jejuni,
S. dysenteriae, E.coli;
* food poisoning: S.aureus, B. cereus)-
o pyrogenic exotoxins (streptococcal ToxicSS) (stimulate release of cytokines)
o shiga toxin (E.coli) inhibits protein synthesis
-Endotoxins only gram -ve (septic shock, Lipid A in LPS from gram-ve bacteria only .)
what are the main types of bac. virulence factors
-Secretion systems (type IV, III) - allows them to get proteins from the cytoplasm of their cells into host cells ie secretion of effector proteins.
-Flagella (for movement, attachment.)
-Pili (for adherence)
-Capsule (S. pneumoniae) (protect against phagocytosis)
-Endospores (Clostriduim sp., Bacillus sp.) (metabolically dormant forms of bacteria)
-Exotoxins:
o neurotoxins (Tetanus and botulinum toxin)-
o enterotoxins (
* infectious diarrhoea:V.cholera, C.jejuni,
S. dysenteriae, E.coli;
* food poisoning: S.aureus, B. cereus)-
o pyrogenic exotoxins (streptococcal ToxicSS) (stimulate release of cytokines)
o shiga toxin (E.coli) inhibits protein synthesis
-Endotoxins only gram -ve (septic shock, Lipid A in LPS from gram-ve bacteria only .)
what are the main types of bac. virulence factors
- Secretion systems (type IV, III) - allows them to get proteins from the cytoplasm of their cells into host cells ie secretion of effector proteins.
- Flagella (for movement, attachment.)
- Pili (for adherence)
- Capsule (S. pneumoniae) (protect against phagocytosis)
- Biofilms (organized aggregates of bacteria embedded in polysaccharide matrix – antibiotic resistant)
i. e. Pseudomonas aeruginosa
i. e. Staphylococcus epidermidis - Endospores (Clostriduim sp., Bacillus sp.) (metabolically dormant forms of bacteria)
-Exotoxins:
o neurotoxins (Tetanus and botulinum toxin)-
o enterotoxins (
* infectious diarrhoea:V.cholera, C.jejuni,
S. dysenteriae, E.coli;
* food poisoning: S.aureus, B. cereus)-
o pyrogenic exotoxins (streptococcal ToxicSS),
S.aureus, S.pyogenes (stimulate release of cytokines)
o shiga toxin (E.coli) inhibits protein synthesis
o Tissue invasive exotoxin (allow bacteria to destroy
and tunnel through tissue)
-Endotoxins only gram -ve (septic shock, Lipid A in LPS from gram-ve bacteria only .)
what are the common HAIs
remember ESCAPE where ESC are Gram + and APE are Gram -
Enterococcus faecium (vancomycin resistance)
Staphylococcus aureus (methicillin resistant - MRSA)
Clostridium difficile (opportunistic: can establish infection
because of previous AB)
Acinetobacter baumanii (highly drug resistant)
Pseudomonas aeruginosa (multi drug resistant)
Enterobacter sp. (not all Gram negative)
-E.coli, K. pneumoniae (multidrug resistant)
commonest cause of hospital acquired UTI’s
pathogenic E.coli
what does Klebsiella pneumoniae cause and what is it resistant to
UTIs, respiratory infections
resistant to: 3rd Gen cephalosporins, fluoroquinolones and aminoglycosides
what does Pseudomonas aeruginosa cause and what is it resistant to
pneumonia, UTIs, GI and skin infections
High proportions of strains are resistant to several antimicrobials
In ½ of EU countries resistance to carbapenems is above 10%
how does MRSA become resistant to methicillin
Resistance is achieved through expression of additional penicillin binding protein (PBP2A) – this has a low affinity for methicillin and thus can still function in the presence of the antibiotic
