Question

Describe in chronological order the events that befall a microbe once it has gained access into the body of the host.

Answer 1

1. Entry into the Host: The microbe enters the host body through a specific portal of entry such as the skin (via inoculation or abrasions), respiratory tract (inhalation), digestive tract (ingestion), or urino-genital tract. The portal of entry is crucial as certain microbes cause disease only if they enter through a specific route.
2. Release of Toxins: After successfully entering the body, the pathogen secretes chemical substances such as toxins. The potency of the toxin plays a major role in the establishment of the disease. These toxins cause physiological, morphological, and anatomical abnormalities in the host’s body.
3. Growth in the Host: With the immune defenses compromised by toxins, the pathogen begins to grow and multiply in the host tissues or fluids. The ability to invade the host tissues and multiply is termed invasiveness. This along with toxigenicity (ability to produce toxins) and infectivity (ability to establish infection) determines the virulence of the pathogen.
4. Host Defense Response: The host, however, employs active or passive resistance mechanisms to try to counter the effects of the pathogen. The defensive mechanisms of the host depend on environmental factors, genetic constitution, immune system activity, and other factors. The extent of infection and severity of the disease depends on the interplay between the pathogen’s virulence and the host’s susceptibility and defense mechanisms.