microbiology definitions Flashcards
define pathogens
Organism that causes or is capable of causing disease
define commensal
do they cause infection?
Organism which colonises the host but causes no disease in normal circumstances
prevent disease by reducing opportunity for bacteria to gain space and nutrients on the surfaces of the body
occasionally cause infection when host is compromised
ie. resident flora that are usually nonpathogenic
define opportunist pathogens
Microbe that only causes disease if host defences are compromised
define virulence (aka. pathogenicity)
The degree to which a given organism is pathogenic
define an asymptomatic carriage
When a pathogen is carried harmlessly at a tissue site where it causes no disease
define microbes
Organism we need a microscope to see (can’t see with naked eye)
define cocci
sphere shaped bacteria
define bacilli
rod shaped bacteria
define diplococcus
2 cocci
define strain
a bacterium that has been isolated from a patient to distinguish it from bacteria of the same species that were obtained from other patients.
Although the same species, the genome sequences are invariably different among strains due to random mutation/gene loss or acquisition of new genes.
define servoras / serotypes
are strains that have antigenic properties that differ from other strains of the same species.
define Pathovars (or pathotypes
are strains that are distinguished by possession of
particular pathogenic mechanisms rather than being based on antigenic differences between molecules on the bacterial cell surface (the serotype).
However, different serovars may exist among members of each pathovar.
define biovars/biotypes
variant bacterial strains that differ physiologically or biochemically from other strains in a particular species.
define fastidious microorganisms
have more exact nutritional requirements and are harder to grow
define infectivity
the ability to become established in host, can involve adherence and immune escape
