In the first instance, the 100X objective does not have any business touching the slide on the stage so that there would not be any reason to raise it a little in order to go back to a lower objective. At higher objectives, only the fine adjustment should be used to bring the object into focus so as to avoid the objective lens from touching the slide which can damage the objective and or break the slide on the stage.
<em>For the X100 objective to be raised in order to avoid a damage to it, it means John allowed the objective to come too close to the slide in the first place. This should not have been so.</em>
Pathogenicity is the ability to produce disease in a host organism
Microbes express their pathogenicity by means of their virulence, a term which refers to the degree of pathogenicity of the microbe
The relationship between a host and a pathogen is dynamic, since each modifies the activities and functions of the other
The outcome of such a relationship depends on the virulence of the pathogen and the relative degree of resistance or susceptibility of the host, due mainly to the effectiveness of the host defense mechanisms
Hence, general requirements for any organism to cause disease within a host are: evasion of host defenses
, gaining access to the host via a portal of entry, adherence to host tissues
