Current & Emerging Foodborne Pathogens

Question 1

Who discovered salmonella?

What animal was salmonella isolated from?

Answer 1

Smith discovered a new species of bacteria (Salmonella enterica, formerly called Salmonella choleraesuis.

It was isolated from a cow.

Question 2

When was regarded as a human pathogen?

Answer 2

1881 (in Germany)

Question 3

What is the Kauffmann and White classification scheme ?

Answer 3

The system that classifies the genus Salmonella into serotypes: O, H, I

1934

Question 4

Salmonella taxonomy

How many species are there?

What are they?

Answer 4

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

Question 5

What are the frequent serotypes of salmonella?

Answer 5

• Salmonella Enteritidis
• Salmonella Typhimurium
• Salmonella Hadar
• Salmonella Virchow

Question 6

State the serotypes of salmonella

Answer 6

• O antigen polysaccharide
• H antigen related to flagella
• Vi antigen is the capsular antigen

Question 7

True or false: Salmonella are gram negative

Answer 7

True

Question 8

Is salmonella peritrichous?

What does mean for its motility?

Answer 8

Yes

It is highly motile

Question 9

True or false: Salmonella are sporulating, facultatively anareobic bacilli

Answer 9

False.

Salmonella are non-sporulating, facultatively anaerobic bacilli

Question 10

What conditions are favourable for salmonella?

Answer 10

• 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

Question 11

What are the symptoms of salmonella

Answer 11

• 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

Question 12

What diseases are caused by salmonella when it has invaded/entered the bloodstream?

Answer 12

• Bacteraemia
• Enteric fever (typhoid)

Question 13

What pets/animals are a risk factor for salmonella?

Answer 13

Reptiles, birds, badgers

Question 14

Draw a diagram to show the routes of salmonella transmission

Answer 14

Question 15

Describe the epidemiology of salmonella

Answer 15

• 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

Question 16

Laboratory Reports of Salmonella
England & Wales 1981-1998

Answer 16

• S.enteritidis increasing in early 1980’s, 1990’s- Edwina currie caused a decrease by

Question 17

Laboratory Reports of Salmonella
England & Wales 2004 - 2013

Answer 17

Biological control mechanism introiduced between 1990-2000’s

Question 18

Why was Salmoella enteritidis more common?

What vaccine was introduced in the 1990’s to combat it?

Answer 18

• 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

Question 19

What are Lion-branded Eggs?

Answer 19

It means that the flock that laid those eggs have been vaccined against salmonella

Question 20

Other phage-types?

Answer 20

When one organism decreases another increases to fill the niche

Question 21

What are some additional problems with Typhimurium?

Answer 21

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

Question 22

What are the Defining characteristics of Campylobacter

Answer 22

• Gram-negative
• Motile
• Spirilla
• Microaerophilic

Question 23

History of Campylobacter

Answer 23

• 1906

John McFadyean

Aborting sheep

Vibrio fetus

• 1931

Vibrio jejuni

• 1946

Illinois jail

• 1973

Campylobacter

Question 24

What are the species of campylobacter?

How many species are currently described?

Answer 24

• F. Campylobacteriaceae

Campylobacter

C. fetus

• 17 species of Campylobacter currently described

Enteropathogenic group

C. jejuni, coli, lari, upsaliensis and helveticus

Question 25

Describe campylobacter physiology

Answer 25

• 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

Question 26

Hippurate Hydrolysis

Answer 26

Important test to identify Campylobacter jejuni

Hippurate–(hippuricase) produces glycine + benzoic acid

Ninhydrin – Blue colouration

Question 27

What is viable Non-Culturable (VNC)

Answer 27

• 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

Question 29

What are psychrophiles?

Answer 29

Extremophilic bacteria or archaea which are cold-loving having an optimal temperature for growth at about 15°C or lower,

Question 30

Can anything grow in a environment with an Aw< 0.6?

Answer 30

No

Question 31

What is the size of salmonella?

Answer 31

2–5 microns long by 0.5–1.5 microns wide