Bacterial Intoxications - C. perfringens

Question 1

Characteristics

Answer 1

Gram +ve rod shape anaerobe
Forms oval subterminal spores
widely distributed pathogens in nature. Common in environmetn such as soils, mammalian GI tract

Question 2

Found in diverse environments due to

Answer 2

• Relatively high tolerance to O2 compared to other anaerobes
• extremely rapid growth on wide range of substrates
• Endospore formation allows it to survive adverse environmental conditions

Question 3

C. Perfringens species

Answer 3

5 types (A-E) based on production of 4 mahor exotoxins ( alpha, beta, e , l ) & 8 minor ones

Question 4

Growth temp & optimal

Answer 4

mesophile (growth at 12 -50’C)

optimal at 43-47’C (generation time of 7.1 min at 41’C)

Question 5

Growth pH

Answer 5

Not acid tolerant (min pH 5; optimum pH for growth 6- 7.5)

Question 6

Growth aw

Answer 6

min. 0.95-­‐0.97

Question 7

Growth [salt]

Answer 7

Will not grow in presence of 6% salt

Question 8

heat resistance

Answer 8

Heat resistance of vegetative cells comparable to non- spore formers (D- value of few min at 60’C in beef)

heat resistance of spores D values of 0.31 min to 38 min at 100’C

Question 9

Diseases caused

Answer 9

• Perfringens food poisoning – common
– C. perfringens type A

• Enteric necro2cans -­ rare
– C. perfringens type C expresses toxins α and β which
damage the intestinal mucosa leading to necrosis

• Gas gangrene
– C. perfringens type A α toxin (lecithinase activity) breaks down phospholipids leading to disruption of cell membrane

Question 10

is it a common food poisoning cause

Answer 10

most common forms of food poisoning after Salmonella

spp.

Question 11

Symptoms:

Answer 11

intense abdominal cramps, diarrhoea and vomi2ng (fever and nausea are rare)

Question 12

Onset time

Answer 12

8 -22 hrs of ingesting food

• Usually self-­‐limi2ng – over within 1-­‐2 days

Question 13

infective dose

Answer 13

High infective dose 10^6 - 10^8 CFU of vegatative
C. perfringens required as not acid-­‐resistant – cells
that survive the stomach, sporulate, grow and release
enterotoxin in the small intestine

Question 14

Enterotoxin

Answer 14

35kDa protein

Not usually produced in food but in the gut
It us heat sensitive, being inactivated in saline at 60’C for 10 min
Produced in large quantities during sporulation
Disrupts mucosal membrane resulting in loss of electrolytes and diarrhoea

Question 15

Associated food

Answer 15

Meat, meat products, cooked foods re- contaminated from environment

Question 16

Common cause of outbreaks

Common occurrence

Answer 16

• C. perfringens present in raw foods, e.g. meat
• Some c. perfringens spores survive cooking process
• During cooling of cooked foods, spores germinate and rapidly grow- especially if food is held at 20- 52’C

Common occurrence in institutional feeding (schools, hospitals, prisons)

Question 17

Control measure

Answer 17

Foods should be eaten while still hot (no cooling down
period) or reheated to an internal temp of > 75°C
before serving
• No growth at refrigeration temperatures but foods
must be cooled to