salmonella

what family does salmonella belong to

Enterobacteriaceae family 

what are the genus

two species: S. bongori and S. enterica 

is it gram - or positive

gram -

shape

motile rod

growth temp

5-47°C, with an optimum at 37°C 

minimum water acitivty

0.93

type of organism

Mesophile 

Vegetative Cells (Non-Sporeformers) 

survival

can survive for extended periods at even lower Aw values 

 

Protection against gastric acid by food matrix, e.g. in fatty products 

disease

Salmonellosis (Non-Typhoidal) 

The illness caused by Salmonella is generally known as Gastro-enteritis 

symptons

abdominal pain, nausea/vomiting, and diarrhoea 

 

Sometimes: Sequelae (long-term complications) can develop, such as Reactive arthritis (affecting joints) 

incubation time

1-2 days

ilness duration

3-7 days

D/R dose response

is usually quite high, though it can sometimes be low 

seasonal trend

There is a seasonal trend- may be related to temperature 

transmission and sources

• commonly found in food of animal origin, such as meat, poultry, raw milk, eggs, and (shell)fish 

• A notable risk is from undercooking eggs 

• Salmonella can persist in food factories (e.g., as "house flora" on processing machines) and in stables where production animals like broilers are raised 

• Darkling beetles can act as a vector, bypassing cleaning efforts in broiler houses and allowing Salmonella to persist. 

• Environmental cycle is hard to break 

prevention and control

•  At the farm level: Implement national control programs, hygiene measures, separate animals from the outside, ensure Salmonella-free feed and water, and use vaccination. 

•  To limit spread of contamination: Comply with microbiological criteria, practice logistic slaughter, and use hygienic equipment design. 

•   General hygiene: Good general hygiene practices (GHP) in factories and retail, along with proper training, are essential. 

•   Food preparation: Proper heating and storage (maintaining the cold chain) at retail, catering, and by consumers are vital. 

• heating to 70 °C is best  method for reducing Salmonella, as demonstrated by the reduction of CFU/g in egg yolks with increased boiling times 

• Even after being ill and recovering person is still a carrier for several days/months. Carriers can be treated with antibiotics 

D value

D-values vary significantly between different Salmonella strains/serotypes and are influenced by the food matrix:

factors affecting D value

D-values are lower at higher temperatures (faster inactivation). 

 Low water activity (aw) and high fat content increase the D-value, meaning more heat is required for inactivation 

z value

The z-value for vegetative cells like Salmonella is typically around 5°C, meaning a 5°C increase in temperature can lead to a 1-log (90%) reduction in the D-value

mortality rate

low less than 1 percent