Lecture 2 Revision Flashcards
Survival starts at introduction
UV can kill pathogens and indicators
Soil:
Moisture
Surface/injected
High/low organic matter
Predators
Dry/wet
Frozen/cold/warm
Plants/bare
pH
Water:
Ground/surface
Predators
Mixed/stagnate
High/low nutrients
High/low sediments
Frozen/cold/warm
pH
Bacterial pathogen survival
Campylobacter - up to 6 days
Clostridium difficile - 5 months
E. coli - 1.5 hours-16 months
Neisseria gonorrhoeae - 1-3 days
Vibrio cholerae - 1-7 days
Virus survival
Adenovirus - 7 days - 3 months
Astrovirus - 14 days
Coronavirus - 3 hours
HIV - >7 days
Influenza 1-2 days
Rotavirus - 6-60 days
Pathogen survival in water
E. coli - 91 days at 8 degrees
Campylobacter spp. - 4-28 days at 4 degrees
Salmonella spp. - 152 days at 18-20 degrees
Yersinia enterocolitica - 64 weeks at 4 degrees
Mycobacterium avian subspecies - 20 degrees for > 3 years
Pathogen survival in soil
E. coli:
56 days at 25 degrees
99 days at 6.5-19.6 degrees
Salmonella:
42 days at 22 degrees
63 days at 5 degrees
Y. enterocoliticia - 7 days at 5 degrees
Campylobacter spp. 20 days at 6 OR 37 degrees
Survival of O157:H7 E. coli in manure
Non aerated ovine manure - >1 year
Aerated ovine manure - 4 months
Aerated bovine manure - 47 days
Bovine manure at 20 degrees - 100 days
Manure can contain up to 10^10 bacteria per gram
Amoeba resistant bacteria
- Some microorganisms resistant to protists and exit free-living amoebae undamaged after internalisation
- Classed as amoeba resistant bacteria, and some pathogenic
Explain Amoebae and bacterial association
- Amoebae are a diverse group in protozoa
- Ubiquitous (soil, water, biofilms)
- Abundance and diversity depend on temperature, pH, season, moisture, precipitation, and nutrients
- Feed on bacteria, fungi, and algae by phagocytosis and digestion in phagolysosomes
- 20% of clinical and environmental Acanthamoebae harbour bacteria
- Some amoebae pathogenic and bacteria they contain
2 stages of amoeba life cycle
Trophozoite - metabolically active stage, feed on bacteria, and multiply by binary fission
Cysts - Two layers - ectocyst and endocyst
Third layer mesocyst present in some species
Provide resistance to adverse conditions e.g. disinfection, osmotic pressure, temp etc
Excyst when environmental conditions become favourable
Bacterial association with Amoeba
Common amoeba host is Acanthamoeba e.g. Chlamydia pneumoniae, E. coli O157, Mycobacterium avian subspecies paratuberculosis
Legionella pneumophila - Many species of amoebae
What bacteria do Acanthamoeba harbour
alpha, beta, gamma, and deltaproteobactera
Chlamydiae
Flavobacteria
Firmicutes
Actinobacteria
Genus Legionella
Legionella pneumophila
Legionella longbeachae
Legionella micdadei
Legionella anisa
etc
57 species
Facts surrounding Legionella pneumophila
- Gram negative
- Non-sporulating
- Rod-shaped (coccobacillus)
- y-proteobacteria
- Acid fast and pleomorphic
What disease does Legionella pneumophila cause?
Legionnaires’ disease
Transmitted by inhalation of infected aerosols
Self-limited, febrile respiratory illness in healthy people - flu-like, no pneumonia rarely fatal (Pontiac fever)
Severe pneumonia with systemic complications in immunocompromised and old people (Legionnaire’s disease)
People at risk: smokers, men, immunocompromised
Mortality rate of Legionella pneumophila
10-20%
Up to 50% in nosocomial infections
Ecology of Legionella pneumophila
- Aquatic reservoir:
natural environments: lakes/rivers
artificial environments: showers, taps, AC, cooling towers
Resistant to high temperature (up to 50 degrees)
Extra and intracellular bacterium - free living or within free living amoebae
1976 outbreak
56th Legionnaires’ convention in Philadelphia
182 cases - 34 deaths from severe pneumonia
Led to identification of new bacterium from pneumonia patients
Same organism isolated from AC systems
Ubiquitous but never described before:
- Stains poorly for visualisation
- Nutrient demanding - not isolated on common microbiological media - need iron salts, cysteine
- First culture in 1977
Why is it a new pathogen
Invade and survive in protozoa as well as human as intracellular parasites
Barrow-in-Furness - 7 fatalities and 180 ill at council owned arts and leisure facility
Edinburgh, 2012 - 2 dead and >100 infected due to chimney
Stoke-on-Trent, 2013 - 2 dead and 21 infected due to spa tub on display
Epidemiology of Legionella
24 species at least once isolated from humans
L. pneumophila - 91% of cases
L. longbeachae - 5% of cases, 30% in Aus/NZ, 50% in S. Aus
Epidemiology of Legionella pneumophila
15 serogroups
Legionella pneumophila sg1:
88.6% caused this serogroup
More virulent in humans
