Bacterial diseases Flashcards
What are the two sources of human bacterial infection?
- Intrinsic = non-sterile sites (e.g. skin, mouth, nasal cavity, large intestine, lower genital tract)
- Extrinsic = expected (e.g. newborn infant and maternal microbiota) and unexpected
Give some examples of bacteria and viruses that use the upper respiratory tract as a portal of entry
VIRUSES:
- Influenza measles
- Varicella (chicken pox)
BACTERIA:
- Streptococcus pneumoniae
- Streptococcus pyogenes
- Neisseria meningitidis
State some consequences of infection via the upper respiratory tract
- Spread to adjacent tissues (e.g. middle ear infection, brain abscess, meningitis)
- Lower respiratory tract infection (e.g. bronchitis, pneumonia)
- Spread to bloodstream (e.g. bacteraemia)
- Upper respiratory tract infection (e.g. pharyngitis, tonsillitis, sinusitis)
- Sepsis
Give some examples of extrinsic bacteria that can infect via the urogenital tract.
- Chlamydia
- Syphillis
- Neisseria gonorrheae
Give some examples of intrinsic bacteria that can infect via the urogenital tract.
- E. coli
- Klebsiella
- Candida/yeast
State some consequences of infection via the urogenital tract
- Urinary tract infection (e.g. cystitis)
- Genital tract infection (e.g. pelvic inflammatory disease)
- Pregnancy-related infection (e.g. Neonatal group B strep infection)
- Spread to bloodstream (e.g. bacteraemia)
- Sepsis
Give examples of bacteria that can infect via broken skin
- Staphylococcus aureus
- Streptococcus pyogenes
State some consequences of infection via broken skin
- Abscess formation
- Bacteraemia
- Necrotic infection/gangrene
- Sepsis
Give some examples of bacteria and viruses that infect via the gastrointestinal tract
BACTERIA:
- E. coli
- Shigella
- Salmonella enterica (food poisoning)
- Listeria
VIRUSES:
- Hep A
- Norovirus
- Hep E
What are some consequences of infection via the gastrointestinal tract?
- Diarrhoeal illnesses
- Bacteraemic/systemic infections (e.g. typhoid)
- Toxin-mediated disease (D&V)
What two main factors affect pathogenicity?
Infectivity
Virulence
What is pathogenicity?
Ability to cause disease
What is infectivity?
The ability of a pathogen to establish infection:
- Transmission to host
- Ability to colonise host
- Tropism - find unique niche (in or outside cells)
- Replicate
- Immune
- Evasion at site of colonisation or niche
What is virulence?
The ability of a pathogen to cause disease:
- Toxin production
- Enzymes that degrade host molecules
- Interruption of normal host processes
- Complete immune evasion
Define infectious dose
Number of bacteria needed to cause infection
