Food spoilage by Bacteria, fungi and protozoa

1. Food spoilage:
Dr. Aswartha Harinath Reddy M.Sc, Ph.D
Department of Life Sciences
Srikrishnadevaraya University
Anantapur –A.P. India

2.  Spoilage is the process in which food deteriorates, it is not edible
to humans or its quality of edibility becomes reduced.
 Various bacteria and fungi can be responsible for the spoilage of
food.

3. Clostridium tetani.
 Tetanus caused by Clostridium tetani.
 Gram-positive, rod-shaped bacteria.
 Spore-forming (Terminal endospore),
anaerobic.
 Found in soil, especially in the
intestinal tracts and feces of various
animals.
 Strictly fermentative mode of
metabolism.

4.  Not pathogenic to humans and animals by invasive infection but
by the production of a potent protein toxin.
 Tetanus toxin or tetanospasmin.
 The toxin has a specific affinity for nervous tissue, it is
referred to as a neurotoxin.
 The toxin has no known useful function to C. tetani.
Pathogenicity:

5.  Tetanus, commonly called lockjaw, is a serious bacterial
disease that affects muscles and nerves.

6.  The tetanus toxin protein has a molecular weight of 150kDa.
 It is translated from the tetX gene as one protein which is
subsequently cleaved into two parts: a 100kDa heavy or
Beta-chain and a 50kDa light or Alpha-chain.
 The chains are connected by a disulfide bond.

7.  Initially binds to peripheral nerve terminals, Transported within the
axon and reaches the central nervous system.
 Blocks the release of inhibitory neurotransmitters (glycine and
gamma-amino butyric acid) across the synaptic cleft, which is
required to check the nervous impulse.
 Stiffness of your neck muscles and lock jaw is common symptoms.

9. Clostridium perfringens
 Clostridium perfringens is a Gram-positive, rod-shaped,
anaerobic, spore-forming pathogenic bacterium of the genus
Clostridium.
 C. perfringens is the third most common cause of food poisoning
bacteria.

10.  Infections due to C. perfringens show evidence of tissue
necrosis, inflammation and gas gangrene also known as
clostridial myonecrosis.
 The toxin involved in gas gangrene is known as α-toxin.

11.  α-toxin (enterotoxin) inserts into the plasma membrane of cells,
producing gaps in the membrane that disrupt normal cellular
function.
 The clostridium perfringens enterotoxin (CPE) is heat-stable
(inactivated at 74 °C (165 °F)).

12. Brucellosis:

13. Brucellosis:
 Brucellosis caused by Brucella species are small, gram-negative,
non motile, nonspore-forming, rod-shaped bacteria.
 They function as facultative intracellular parasites, causing
chronic disease, which usually persists for life.
 Brucellosis is a highly contagious zoonosis caused by ingestion of
unpasteurized milk or uncooked meat.

14.  Four species infect humans: Brucella abortus, B. canis,
B. melitensis
 B. melitensis is the most virulent infects goats and cows.
 Brucellosis induces inconstant fevers, sweating, weakness,
anaemia, headaches, depression, and muscular and body pain.

15.  The organism does not have classic virulence factors (eg,
exotoxins or endotoxins).
 Replication of the bacterium takes place in the endoplasmic
reticulum without causing lysis of the host cell.

16.  Brucella spp invades and persists in the host via inhibition of
programmed cell death.
 Brucella spp also appear capable of disrupting the host immune
response by inhibition of TNF-alpha synthesis.
 Inactivate cytotoxic function of natural killer cells in animal
body.

17. Bacillus cereus

18.  Bacillus cereus is a Gram-positive, rod-shaped, aerobic,
facultative anaerobic, motile, commonly found in soil and food.
 Bacillus, can produce protective endospores.
 Its virulence factors include cereolysin and phospholipase C
hemolysin BL (Hbl) and cytotoxin K (CytK).

19.  B. cereus is responsible for a minority of foodborne illnesses
(2–5%), causing severe nausea, vomiting, and diarrhea.
 Bacillus foodborne illnesses occur due to survival of the
bacterial endospores when food is improperly cooked.
 The hemolysin, phospholipase C and cytotoxin K (CytK). are
pore-forming enterotoxins are all produced in the small
intestine of the host.

20. Escherichia coli (E. coli):
 Escherichia coli is a gram-negative, facultative anaerobic, rod-
shaped, bacteria.
 Escherichia coli (E. coli) are bacteria that live in human and
animal intestines producing vitamin K.
 Most E. coli strains are harmless, but some serotypes can cause
serious food poisoning.

21.  Shiga toxin-producing strains of E. coli are responsible for most
food-related infections.
 The toxin has two subunits—designated Alpha (mol. wt. 32000
D) and Beta (mol. wt. 7700 D).
 The Beta subunit is a pentamer that binds to specific glycolipids
on the host cell.
 Following this, the A subunit is internalised and then binds to the
ribosome, disrupting protein synthesis.

22. The main symptoms of an E. coli intestinal infection are:
 Bloody diarrhea.
 Stomach pain.
 Nausea and vomiting.

23. THANK YOU