Infection Flashcards
list the portals of entry
- penetration
- direct contact
- ingestion
- inhalation
what does it mean if an infection is endemic
the incidence and prevalence are expected and stable
when is an infection an epidemic
there is an abrupt and unexpected increase in incidence over endemic rates
when is an infection a pandemic
it has spread beyond continental boundaries
define penetration (infection - portal of entry)
disruption to the integrity of the skin or a mucous membrane
ex. a wound
define direct contact
infection - portal of entry
infected tissue/secretations contact a mucous membrane
ex. STI’s
define ingestion (infection - portal of entry)
the pathogen enters the oral cavity and gastrointestinal tract
An infectious dose must survive low pH, enzyme activity, and peristaltic action
ex. food poisoning
who would be more at risk for becoming infected through ingestion
those with decreased gastric acidity due to medications/disease
define inhalation (infection - portal of entry)
the pathogen enters the respiratory tract
ex. meningitis, bacterial pneumonia, tuberculosis
who would be more at risk for becoming infected through inhalation
those with defective pulmonary function such as cystic fibrosis, emphysema or smoking
what are the stages of the disease course
- incubation
- prodromal
- acute
- covalescent
- resolution
describe the incubation phase of the disease course
- the pathogen begins to replicate
- no symptoms
describe the prodromal phase of the disease course
- initial appearance of symptoms
- host may experience mild fever, headache, myalgia, fatigue
describe the acute phase of the disease course
- rapid proliferation and dissemination of the pathogen
- maximum impact experienced, symptoms pronounced and more specific
- toxic by-products of microbial metabolism, cell lysis, and the immune response cause tissue damage and inflammation
describe the convalescent phase of the disease course
- containment and progressive elimination of pathogen
- repair of tissue damage
- resolution of symptoms
describe the resolution phase of the disease course
- total elimination of pathogen
- no symptoms
define subclinical
illness progresses from infection to resolution without symptoms
define insidious
the prodromal phase is longer than usual
what is a fulminant illness
an abrupt onset of symptoms with little or no prodromal stage
what are 3 lab techniques for diagnosis
- culture
- serology
- DNA & RNA sequencing
how is a culture used for diagnosis
microorganisms are propagated on an artificial growth media
- bacterial pathogen is detected due to microscopic appearance and Gram stain
- viruses require propagation of eukaryotic cells and will produce pathologic changes in the appearnace of the cell
how is serology used for diagnosis
- measures serum antibodies in the host
- tentative diagnosis can be made by measuring the antibody level against a specific pathogen
- certain antibodies are produced at different phases of infection
what are two antibodies that serology measures
IgM and IgG
how is serology used to detect congenital infections
IgM doesn’t cross the placenta but some IgG can.
Therefore IgM in a child must be from the child and indicate congenital infection, whereas IgG can’t differentiate
during acute infection, levels of the antibody IgM will do what
rise and fall
during acute infection, levels of the antibody IgG will do what
rise and remain level until or beyond resolution
what are the 2 types of DNA and RNA sequencing used for diagnosis
- DNA probe hybridization
- polymerase chain reaction
explain local manifestation
infection is specific, and reflects the site of infection (localized)
ex. rash, diarrhea, hemorrhage, pneumonia
explain systemic manifestation
nonspecific and can be shared by many infectious diseases
ex. fever, myalgia, headache, lethargy
what are the 4 mechanisms of antibiotic action
- interference with a specific step in bacterial cell wall synthesis
- inhibition of bacterial protein synthesis
- interruption of nucleic acid synthesis
- interference with normal metabolism
what is the main target of antiviral drugs
viral RNA or DNA synthesis (the virus’s replication process)
how do antiviral drugs work
they mimic nucleoside building blocks of RNA or DNA.
during viral replication, nucleosides inhibit the viral DNA polymerase = prevents replication
