Microbes & Pathogenicity

Microbes & Pathogenicity

A microbe is a small tiny microorganism which can be seen only under a microscope. The organism capable of causing disease in man kind are called as Pathogen. The mankind in this case who is getting affected by these pathogens is called as host. The ability of the harmful microbes to cause disease is called as Pathogenicity. If the host is compromised in some way either by weekend immunity or breach to body’s natural defense mechanism, the opportunistic pathogen may infect such host and cause the disease. Virulence is a degree of measuring the pathogenicity of a microbe.

There are many variables to consider in a host-pathogen interaction, which is a dynamic relationship. The virulence of the pathogen is important, but so is the number of microbes that enters to the host, the location of entry, the overall health of the host, and the state of the host’s defences. Exposure to a pathogen does not ensure that disease will occur, since a host might be able to fight off the infection before disease signs/symptoms develop.

A pathogen from the reservoir can enter the host by suitable mode of transmissions like direct contact, droplet transmission, indirect contact, airborne or fecal-oral transmission or even by Vector borne transmission. Once as the pathogen enters the host by suitable portal, it is the virulence factor of them which can infect the host to cause the disease. The virulence factors arise from the physical structure and chemical substances they can produce. These factors are commonly found on microbes’ chromosome or plasmid DNA which contains pathogenicity islands.

After entry microbes will adhere to specific host tissues and with colonisation, they increase their nos to invade more sites in host body. Once as the invasion sites by microbes increases in host body the typical disease symptoms start getting developed in host body. During this stage the virulent microbes continues to release the chemicals, especially enzymes like collagenase, or leucocidins which works strongly to reduce the immunity of the host body. Now as the onset of disease progresses faster microbes may enter blood stream to cause bacteraemia that ultimately leads septicaemia and septic shock that can be fatal.