M1: CC1: Intro to Clinical Infectious Diseases Flashcards
(38 cards)
infectious etiologies (5)
bacteria (gram+, gram-, acid-fast, intracellular, others)
viruses (RNA, DNA)
fungi (yeasts, molds, dimorphic fungi)
parasites (protozoa, helminths, ectoparasites)
prions
nomenclature:
Genus and species (applies only to _)
Organism should be in _
Genus name should (be/not be) capitalized and the species name should (be/not be) capitalized (eg. _)
Genus name can be _ (eg, _)
Disease name should be _
Spp. is _ (eg, _); (do/do not) italicize it.
bacteria, fungi, and parasites
italics
be
not be
eg, Staphylococcus aureus
abbreviated after its first mention
eg, S. aureus
in normal print
an abbreviation for species
eg, Enterococcus spp
do not
micro-organisms:
colonizers
10^12 micro-organisms per human (consists of (more/fewer) human cells)
Most organisms are colonizers of _.
They prevent _.
There are many essential functions that bacteria have, such as _ and _
fewer
gut and skin
other more pathogenic bacteria from overtaking and hurting us
fermenting carbohydrates in our intestines
producing our essential Vitamin K
micro-organisms:
opportunists
These organisms (do/do not) normally cause any harm
However, _.
For example, when inserting a plastic catheter through the skin, _ can get access into the
bloodstream and cause _.
do not
at the wrong place at the wrong time they can cause disease
Staphylococci
bacteremia
micro-organisms:
pathogens
Some organisms are always (helpful/harmful) to us such as Ebola virus.
Our immune system is constantly _
harmful
at the look-out to neutralize them
how we can identify bacteria, viruses, fungi, & parasites:
appearance
Sometimes by _ (some parasites)
mostly by looking at a _ (bacteria)
or by _ (viruses)
naked eye
Gram stain through a microscope
electron microscopy
how we can identify bacteria, viruses, fungi, & parasites:
culture
grow the bacteria and fungi on _
viruses on _
media
cell culture
how we can identify bacteria, viruses, fungi, & parasites:
antigen recognition
By using _ that attaches to proteins of a specific micro-organism
By _ through the immune response of the host; detect _ in blood serum that are directed towards specific micro-organisms
fluorescent dyes (DFA = Direct Fluorescent Antibody)
serology
IgM and IgG antibodies
how we can identify bacteria, viruses, fungi, & parasites:
biochemical properties
Mostly useful for _ & some _
Tests of _ (coagulase activity in Staphylococci)
Tests of _, e.g. lactose fermentation in E. coli
metabolically active bacteria
fungi
enzymatic activity
carbohydrate fermentation/utilization
how we can identify bacteria, viruses, fungi, & parasites:
gene detection
_ of known viral or bacterial genetic sequences (GeneXpert for Mycobacterium tuberculosis in sputum)
Bacterial gene sequences analyzed with help of the _ (16S ribosomal DNA)
PCR: primer recognition
BLAST database
how we can identify bacteria, viruses, fungi, & parasites:
protein detection
_, rapidly becoming commonplace in medical microbiology laboratories.
Matrix-Assisted Laser Desorption Ionization-Time Of Flight Mass Spectrometry (MALDI-TOF MS)
infectious differential diagnosis
A differential diagnosis is _.
First we have to decide between _ vs. _ causes of an illness.
If it is _, than we have to differentiate between _, _, _, or _organisms.
In order to perform the appropriate tests and treat the patient we often have to guess first, based on _, _, _ and _.
the list of possible diagnoses for the symptoms and signs of the patient
infectious vs. non-infectious
infectious
bacterial, viral, fungal, or parasitic
pattern recognition, exposures, incubation time and epidemiology
laboratory investigations:
The differential diagnosis can be shortened by use of appropriate investigations and the collection of specimens from the patient can allow:
1) _ to be made; the collection of specimens should ideally take place _ antimicrobials are given, since this will decrease the
chance of _
2) a prediction to which _ the organism is susceptible
precise microbiologic diagnosis
before
recovering the causative organism
antimicrobials
laboratory investigations:
caveat:
Many body sites have _
Therefore, cultures from body sites need to be interpreted in view of these _:
- The _ is covered by coagulase negative staphylococci, corynebacteria, etc
- The _, _, and _ are full of organisms
- The _ is full of organisms
their own resident bacterial flora
colononizers
skin
mouth, pharynx and vagina
gut
The resident (colonizing) human microflora can obscure investigations into clinical infectious diseases:
The human _ and _ harbor 10^9 micro-organisms representing 700 species
The isolation of colonzers occasionally associated w/ disease states is (common/uncommon) in healthy persons
mouth and pharynx
common
Disease states associated w/ colonizers:
o viridans streptococci
o HACEK group organisms
o Fusobacterium spp.
o Neisseria meningitidis
o Candida albicans (yeast)
o endocarditis
o endocarditis
o bacteremias
o meningitis
o thrush
if viridans streptococci or HACEK organisms (Haemophilus parainfluenzae, Aggregatibacter spp., Cardiobacterium hominis, Eikenella corrodens, Kingella kingae) stick to fibrin-platelet thrombi on damaged heart valves causing persistent bacteremia (positive blood cultures), then a life-threatening _ results
infective endocarditis
If Neisseria meningitidis colonizing the pharynx of a college student passes to a new host with no prior adaptive immunity to the strain, invasion past the cribriform plate, proliferation in the CSF, and resulting inflammation results in a life-threatening _
bacterial meningitis
Koch’s postulates (4)
- The microorganism must be found in abundance in all organisms suffering from the disease, but not in healthy organisms.
- The microorganism must be isolated from a diseased organism and grown in pure culture.
- The cultured microorganism should cause disease when introduced into a healthy organism.
- The microorganism must be re-isolated from the inoculated, diseased experimental host and identified as being the same as the original causative agent.
Violation of Koch’s postulate #1:
The microorganism must be found in abundance in all organisms suffering from the disease, but not in healthy organisms.
Many diseases violate postulate #1 such as Clostridium difficile or Salmonella typhi (typhoid Mary) where humans can be colonized with the micro-organism without being ill (carrier state)
Violation of Koch’s postulate #2:
The microorganism must be isolated from a diseased organism and grown in pure culture.
Viruses and prion diseases violate postulate #2
Violation of Koch’s postulate #3:
The cultured microorganism should cause disease when introduced into a healthy organism.
It can be nearly impossible to test #3 if no animal model is available (HIV)
If Koch’s postulates are not met but you want to implement a microorganism as the cause of a disease you need clinical judgment in conjunction with: (4)
- Biostatistical tests of association
- Serological surveys in human populations
- Epidemiologic studies (case-control)
- Molecular pathogenesis postulates
Microbiologic testing in clinical bacteriology practice:
Qualitative
Patient specimen placed in _ to _
Result is expressed as _
Finalizing negative results takes from _ depending on growth rate of organism
Mostly reserved for analysis of _
Maximize _ at the expense of _
Examples (2)
nutritive broth
amplify small number of organisms present
positive for a specific organism or negative
5 to 42 days
sterile body sites (blood, CSF)
sensitivity
positive predictive value (false positives from contamination are common)
blood cultures
acid fast bacillus (AFB) cultures from sputum for Mycobacterium tuberculosis
