Current & Emerging Foodborne Pathogens Flashcards
Who discovered salmonella?
What animal was salmonella isolated from?
Smith discovered a new species of bacteria (Salmonella enterica, formerly called Salmonella choleraesuis.
It was isolated from a cow.
When was regarded as a human pathogen?
1881 (in Germany)
What is the Kauffmann and White classification scheme ?
The system that classifies the genus Salmonella into serotypes: O, H, I
1934
Salmonella taxonomy
How many species are there?
What are they?
Currently accepted taxonomical position
2 species
Salmonella enterica
6 subspecies
- Salmonella enterica subsp. enterica
- Salmonella enterica subsp. salamae
- Salmonella enterica subsp. arizonae
- Salmonella enterica subsp. diarizonae
- Salmonella enterica subsp. hautenae
- Salmonella enterica subsp. Indica
Salmonella bongori
What are the frequent serotypes of salmonella?
- Salmonella Enteritidis
- Salmonella Typhimurium
- Salmonella Hadar
- Salmonella Virchow
State the serotypes of salmonella
- O antigen polysaccharide
- H antigen related to flagella
- Vi antigen is the capsular antigen
True or false: Salmonella are gram negative
True
Is salmonella peritrichous?
What does mean for its motility?
Yes
It is highly motile
True or false: Salmonella are sporulating, facultatively anareobic bacilli
False.
Salmonella are non-sporulating, facultatively anaerobic bacilli
What conditions are favourable for salmonella?
- Temp 7 – 48°C (mesophile/neutrophile) should be inhibited by refigerated
- pH 4 – 8
- Aw >0.93 (Ability of the organism to grow when water is restricted)
Pure water has a Aw of 1.
Water activity of the environment<0.93 salmonella can’t grow anymore
What are the symptoms of salmonella
- Gastroenteritis
- Non-invasive, prevents water absorption> diarrhoea
- Headache, nausea, mild vomiting, profuse diarrhoea
- Incubation 8 – 48h (7d)
- Infective dose 106 – 109 (<102) More you are exposed to, the more severe your symptoms will be
What diseases are caused by salmonella when it has invaded/entered the bloodstream?
- Bacteraemia
- Enteric fever (typhoid)
What pets/animals are a risk factor for salmonella?
Reptiles, birds, badgers
Draw a diagram to show the routes of salmonella transmission
Describe the epidemiology of salmonella
- Decreasing incidence untill the 1940s
- Increasing incidence in the 1960s, early 80s (Commonplace eating of poultry)
- Decreasing incidence in the 1997
- Seasonal variation- higher in the summer months
Laboratory Reports of Salmonella
England & Wales 1981-1998
- S.enteritidis increasing in early 1980’s, 1990’s- Edwina currie caused a decrease by
Laboratory Reports of Salmonella
England & Wales 2004 - 2013
Biological control mechanism introiduced between 1990-2000’s
Why was Salmoella enteritidis more common?
What vaccine was introduced in the 1990’s to combat it?
- Salmonella Enteritidis PT4 could infect the ovaries of chickens, so when the chicken laid the egg, salmonella was on the inside (associated with the yolk membrane) proteced
- Salenvac vaccine
What are Lion-branded Eggs?
It means that the flock that laid those eggs have been vaccined against salmonella
Other phage-types?
When one organism decreases another increases to fill the niche
What are some additional problems with Typhimurium?
Salmonella Typhimurium DT104 (definitive type 104)
Resitance to (ACSSuT) Ampicillin, chloramphenicol, streptomycin, sulphonmides, tetrocycline (sometime rofampacin)
- Increasing trimethoprim resistant
- Reported resistance to quinolones
- Chromosomally integrated resistance
What are the Defining characteristics of Campylobacter
- Gram-negative
- Motile
- Spirilla
- Microaerophilic
History of Campylobacter
- 1906
John McFadyean
Aborting sheep
Vibrio fetus
- 1931
Vibrio jejuni
- 1946
Illinois jail
- 1973
Campylobacter
What are the species of campylobacter?
How many species are currently described?
- F. Campylobacteriaceae
Campylobacter
C. fetus
- 17 species of Campylobacter currently described
Enteropathogenic group
C. jejuni, coli, lari, upsaliensis and helveticus
Describe campylobacter physiology
- Microaerophilic
5% O2 : 10% CO2 : 85% N2
Gram –ve
Oxidase-positive
Catalase-positive
Urease-negative
- Polar flagellum
- Aw >0.98
- Thermophilic
37 & 42 °C
Not 25 °C
VNC
Hippurate Hydrolysis
Important test to identify Campylobacter jejuni
Hippurate–(hippuricase) produces glycine + benzoic acid
Ninhydrin – Blue colouration
What is viable Non-Culturable (VNC)
- Spiral to coccoid morphology
Atmospheric oxygen levels
Environmental stress
VNC
- Infectivity is controversial
Difficulty in proving absence of spiral forms
- Role of VNC in Campylobacter survival, transmission unclear
What are psychrophiles?
Extremophilic bacteria or archaea which are cold-loving having an optimal temperature for growth at about 15°C or lower,
Can anything grow in a environment with an Aw< 0.6?
No
What is the size of salmonella?
2–5 microns long by 0.5–1.5 microns wide
