This document discusses the pathogenicity of bacteria by focusing on two main qualities: invasiveness and toxigenicity. It defines invasiveness as a bacteria's ability to spread and invade host cells and tissues, often using enzymes. Toxigenicity refers to a bacteria's ability to produce toxins, specifically endotoxins which are part of the bacterial cell wall, and exotoxins, which are secreted proteins that can damage distant tissues. Overall, the document examines the mechanisms that allow bacteria to cause disease in hosts.

1. PATHOGENICITY OF BACTERIA
INVASIVENESS AND TOXIGENICITY
BY
NAME-NIYAT DIPANKAR PANDA GUIDED BY;
M.Sc Zoology, 1st Year Dr. Sunita Satapathy
SCHOOL OF APPLIED SCIENCES
REGD NO.-220705180016

2. CONTENTS-
INTRODUCTION
HOST-PATHOGEN INTERACTION
MECHANISM OF BACTERIAL PATHOGENESIS
INVASIVENESS
TOXIGENICITY
REFERENCES
ACKNOWLEDGEMENT

3. INTRODUCTION-
 A microbe that is capable of causing disease is referred to as a pathogen and the organism
being infected is called a host.
 The ability to cause disease is referred to as pathogenicity, with pathogens varying in their
ability.
 The measurement of pathogenicity is called virulence, with highly virulent pathogens being
more likely to cause disease in a host.
 Determinants of virulence of a pathogen are any of its genetic or biochemical or structural
features that enable it to produce disease in host.
 Characteristics of bacteria that are pathogens include transmissibility, adherence to host cells,
persistence, invasion to host cells and tissues, toxigenicity, and the ability to evade or survive
the hosts immune system.

4. HOST-PATHOGEN INTERACTION-
 There are many variables to take into account in a host-pathogen interaction, which is a
dynamic relationship that is constantly changing.
 The virulence of the pathogen is important, but so is the number of microbes that gained
entry to the host, the location of entry, the overall health of the host, and the state of hosts
defences.
 Exposure to a pathogen does not ensure that disease will occur, since a host might be able to
fight off the interaction before disease signs/symptoms develop.
Fig 1: Host-pathogen interaction

5. Two broad qualities of pathogenic bacteria
underline the means by which they cause
disease; they are-
i. Invasiveness
ii. Toxigenicity
Invasiveness-
 It refers to the ability of the pathogen to
spread to other locations in the host, by
invading host cells or tissue.
 It is typically at this point when disease or
obvious signs/symptoms of illness will occur.
 While physical structures can still play a role
in invasion, most bacterial pathogens
produce a wide array of chemicals, specially
enzymes that effect the host’s cells and
tissue.
 Enzymes such as collagenase, which allows
the pathogen to spread by braking down the
collagen found in connective tissue or
leukocidins which destroy the host’s white
blood cells, decreasing resistance.
Fig2: Bacterial Invasion

6. Toxigenicity-
 Toxigenicity refers to an organism’s ability to make toxins.
 Bacteria may produce two types of toxins called endotoxins and exotoxins.
Fig 3: Endotoxins and Exotoxins
Endotoxins-
 They are the lipopolysaccharides present on gram –ve bacterial cell wall
 The lipid A portion of the lipopolysaccharide is responsible for endotoxin activity.
 They are the integral part of the bacteria and are released as bacteria lyse.
 Endotoxin mediated toxicity include: Fever, activation of complement, thrombocytopenia,
decreased peripheral circulation and perfusion of organs, shock and death.
 Endotoxins can also cause a weakening of the blood-brain barrier and allow more bacteria
from the bloodstream to cross it.

7. Exotoxins:
 Exotoxins are heat-sensitive soluble proteins that are released into the surrounding
environment by a living organism.
 Exotoxins are most commonly produced by gram-positive bacteria.
 These incredibly potent substances can spread throughout the host’s body, causing damage
distant from the original site of infection.
 Exotoxins are associated with specific diseases, with the toxin genes often carried on
plasmids or by prophages.
 There are many different bacteria that produce exotoxins, causing diseases such as botulism,
tetanus and diptheria.

8. REFERENCES-
Eisenstein, T.K., Actor, P. and Friedman, H.(1993) Host Defences to Intracellular Pathogens,
Plenum Publishing Co:115-123
Finlay, B.B. and Falkow, S(1989) Common themes in microbial pathogenicity, Microbial
Rev:210

9. ACKNOWLEDGEMENTS-
• My subject teacher: Dr. Sunita Satapathy
• Dr. Yashaswi Nayak, HoD and Dean SoAS
• All the faculty members of Department of Zoology, School of Applied Science,
CUTM
• Family and Friends