bacterial infections Flashcards
community acquired infections: define an outbreak of infectious disease and explain how outbreaks are identified; list bacterial pathogens that cause community acquired infection, explain the routes and types of infection caused, and list important bacterial virulence factors
components of bacterial cell
ribosomes, DNA, cell wall, cytoplasm, cell membrane; capsule, flagellum, pili
common virulence factors
diverse secretion systems, flagella (move, attach), pili (adhere), capsule (protect vs phagocytosis), endospores (dormant bacteria which are temperature, dessication and chemical resistant), biofilms (organised aggregates which cause antibiotic resistant), endotoxins, exotoxins
bacteria with capsule
Step. pneumoniae
2 bacteria with endospores
Bacillus sp., Clostridium sp.
2 bacteria with biofilms
Pseudomonas aeruginosa, Staph. epidermidis
5 types of exotoxins and what they act on/stimulate/allow
neurotoxins (act on nerves or motor endplate), enterotoxins (act on GI tract), pyrogenic exotoxins (stimulate release of cytokines), tissue invasive exotoxin (allow bacteria to destroy and tunnel through tissue), miscellaneous exotoxin (specific/not well understood)
examples of bacteria producing neurotoxins
Tetanus, Botulinum
examples of bacteria producing enterotoxins (infectious diarrhoea)
V. cholera, E. coli
examples of bacteria producing enterotoxins (food poisoning)
B. cereus, Staphy. aureus
examples of bacteria producing pyrogenic toxins
Staph. aureus, Strep. pyogenes
what do bacteria which cause tissue invasive exotoxin contain
enzymes that destroy DNA, collagen, fibrin, RBC, WBC etc.
examples of bacteria causing tissue invasive exotoxin
Staph. aureus, Strep. pyogenes
example of bacteria causing miscellaneous exotoxin
B. anthracis
what is an endotoxin
lipid A component of LPS (not protein) in gram -ve bacteria
gram +ve vs gram -ve
gram +ve has thick peptidoglycan layer, gram -ve has thin peptidoglycan layer and another layer of LPS
why can treating patient with gram -ve infection with antibiotics sometimes worsen condition
bacteria lyse, releasing large quantities of LPS and endotoxin, causing septic shock
5 things which are determined following an outbreak
causative agent, illness, source, time frame, scale
what can be used to detect outbreak strain
PCR (isolates can be screened by multiplex PCR for characteristic features of outbreak strain; can be done on stool samples); can then compare outbreak strain with known strains (determine what toxins have transferred to strain via bacteriophage)
describe Shiga toxin structure
have an AB5 subunit composition, with toxin (StxA) which can block protein synthesis in eukaryotic cells
what determines what a bacteria acts on in body
strains and virulence factor
define outbreak
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 provides an opportunity to identify outbreaks; good and timely reporting systems are instrumental to identify outbreaks
6 types of communicable diseases in Europe
respiratory tract infections, sexually transmitted infections, food and waterborne diseases and zoonoses, emerging and vector-borne diseases, vaccine-preventable diseases, antimicrobial resistance and healthcare-associated infections
examples of respiratory tract infections
influenza (virus), TB (gram +ve), SARS (virus), avian influenza (virus), Legionnaire’s disease (gram -ve)
infection route of Legionella pneumophilia (causes Legionnaire’s disease)
inhalation of contaminated aerosols
where does Legionella pneumophilia grow in humans (causes Legionnaire’s disease)
alveolar macrophages
describe Legionella pneumophilia (causes Legionnaire’s disease) type IV secretion system
secretion of effector proteins by type IV secretion system allow bacteria to replicate in Legionella containing vacuole (LCV)
why is treatment of TB (mycobacterium tuberculosis) more difficult
very different cell wall with extra lipid layer
describe latent TB
can enter dormant state, as evidence of infection but no clinical signs and symptoms of active disease
examples of sexually transmitted infections
HIV/AIDS (virus), syphilis (Treponema pallidum; gram -ve), Hep B and C (viral), gonorrhoea (Neisseria gonorrohoeae; gram -ve), Chlamydia trachomatis (gram -ve)
describe Chlamydia trachomatis (gram -ve)
obligate IC pathogen, either causing STI or eye infection (causing blindness)
describe Neisseria gonorrohoeae (gram -ve)
diplococcus; interacts with non-ciliated epithelial cells to establish infection in urogenital tract; has pili and antigenic variation to escape detection and clearance by immune system
examples of food and waterborne diseases and zoonoses
anthrax, botulism, campylobacteriosis, cholera, infection with vero/shiga toxin producing E. coli, salmonellosis
describe campylobacteriosis
small children are high risk group; due to undercooked poultry; adhesion and invasion factors, flagella motility, type IV secretion system, toxin
describe Salmonella sp.
undercooked poultry, highest infection rate in small children; type III secretion system encoded on pathogenicity islands
describe V. cholerae
acute, severe diarrheal disease needing prompt rehydration; type IV fimbria, cholera toxin carried on a phages
describe how cholera toxin causes diarrhoea
AB5 toxin, with A subunit being enzymatic and makes cell produce signalling molecule which activates CFPR channel, pumping out Cl- and causing diarrhoea
describe Listeria monocytogenes
risk group immunocompromised, elderly, pregnant and foetus; can enter non-phagocytic cells and cross tight barriers e.g. intestinal, foetal
examples of emerging and vector-borne diseases
malaria, plague (Yersinia pestis - gram -ve), Q fever (Coxiella burnetti, gram -ve), SARS, smallpox, VHF, West Nile fever, yellow fever
examples of bacterial vaccine preventable diseases
diptheria (gram +ve), invasive haemophilus influenzae disease (gram -ve), invasive meningococcal disease (gram -ve), invasive pneumococcal disease (gram +ve), pertussis (gram -ve), tetanus (gram +ve)
