PATHOGENICITY OF MICROORGANISMS

 

Introduction:  Any microorganism that is able to infect a host and produce disease is called a pathogen.  The infection and disease do not always occur together as one may be infected without clinical signs and symptoms and we call that state asymptomatic.  It is only arise of clinical signs and symptoms of a give pathogen that we can assume the disease state.  The capacity of the organism to cause disease reflects its relative pathogenicity.  As will be discussed in this case, bacteria can be organized into three major groups basing on virulence and spectrum of disease burden.

Frank Pathogens:  When these are isolated from a patient, frank pathogens are considered to be probable agents of a disease.  This is considered basing on the vilulence factors encountered.  Such examples include the following.  Salmonella typhi, the causative organism for typhoid fever, Neisseria gonorrhoeae, the causative organism for Gonorrhoea and,  Yersinia pestis, the causative agent for plaque.

Opportunistic Pathogens:  These are isolated from patients whose defense mechanisms have been compromised, e.g. Staph. epidermidis infection.

Non-pathogens: These rarely or never cause human disease. Bacillus subtilis is an example of nonpathogenic microorganism.  Whether disease ensues as a result of a host’s encounter with a pathogen is dependent both upon the condition of the host and particular characteristics of the microorganism. The characteristics that contribute to the ability of a microbe to produce disease are referred to as virulence factors. 

RELATED;

1.  HEMOLYSINS  

2.  BACTERIOLOGY

3.  SALMONERA AND THE TYPHOID FEVER

4.  NEISSERIA GONNORHEAE

5.  MEDICAL MICROBIOLOGY

REFERENCES