Epidemiology and Clinical Micro Flashcards
General Terms
Epidemiology
science that evaluates occurrence, determinants, distribution and control of health and disease in a defined human population
General Terms
epidemiologist
one who practices epidemiology
General Info
Who was the first epidemiologist?
John Snow
Epidemiology Terms
sporadic disease
occurs occasionally and at irregular intervals
- bacterial meningitis
Epidemiology Terms
endemic disease
maintains a relatively steady low-level frequency at a moderately regular interval
- common cold
Epidemiology Terms
hyperendemic disease
gradually increase in frequency above endemic level but not to epidemic level
- common cold during the winter
Epidemiology Terms
outbreak
sudden, unexpected occurrence of disease in a limited segment of population
- listeria outbreaks
Epidemiology Terms
epidemic
outbreak affecting many people at once with sudden increase in occurrence above expected number
- ebola
Epidemiology Terms
pandemic
increase in disease occurrence within a large population over at least two countries around the world
- COVID, H1N1 flu
Measuring Disease Frequency
incidence
measure of number of diseased individuals during a defined period compared to total healthy population
Measuring Disease Frequency
prevalence
total number of individuals infected at any one time compared to the total healthy population
- depends on both incidence rate and duration of illness
Measuring Disease Frequency
morbidity rate
number of new cases in a specific time period per unit of population
Measuring Disease Frequency
mortality rate
relationship between number of deaths from a disease compared to the total number of cases of the disease
Types of Epidemics
communicable diseases
an infectious disease that can be transmitted from person to person
T/F: All infectious disease are communicable.
FALSE – not all infectious disease are communicable
- rabies: animal to person
Types of Epidemics
What are the two types of epidemics?
- common source
- propagated
Types of Epidemics
common source
- noncommunicable
- peaks within a short timeframe (1-2 weeks) and is followed by a rapid decline in the number of infected individuals
Types of Epidemics
propagated
- communicable
- slow, prolonged rise in infected individuals followed by a gradual decline
- results from the introduction of a single infected individual into the population which spreads the infection until many individuals are infected
Epidemiology Terms
herd immunity
resistance of a population to infection and pathogen spread because of immunity of large percentage of the population
In herd immunity, increasing the number of susceptible individuals can cause an ?? disease that can become an ??.
- endemic
- epidemic
What are the reasons for increases in emerging and reemerging infectious diseases?
- world population growth, urbanization
- inadequate public infrastructures
- increased international travel, mass migrations
- climate changes
- habitat disruption
- microbial evolution and development of resistance
Terms
HAI
hospital-acquired infections
HAIs
nosocomial infections
infection acquired by a patient while in the hospital or at another clinical care facility
HAIs
What percent of patients will get an HAI according to the CDC?
5-10%
HAIs
What are HAIs typically caused by?
antibiotic-resistant bacteria
- most are members of normal microflora
HAIs
What are the most common HAIs in decreasing prevalance?
- UTIs
- all others
- surgical site infections
- bloodstream infection
- pneumonia
Sources of HAIs
endogenous pathogen examples
- brought into hospital by patient
- patient is colonized after admission
Sources of HAIs
exogenous pathogen example
- microbiota other than the patient’s
- may come from hospital staff, other patients, and visitors, food, plants, and flowers, computer keyboards, intravenous and respiratory therapy equipment, and water systems
Clinical Microbiology
What are the 2 goals of clinical microbiology?
- rapid and accurate identifaction of pathogens from clincal specimens
- antimicrobial susceptibility testing of the organisms
What are some examples of patient specimen evaluation?
- rapid tests and immunoassays
- molecular testing
- biochemical testing
- culture
- microscopy
Specimen collection
What things should be considered for specimen collecting methods?
- represent the diseased area
- quantity should be adequate
- collection to avoid contamination
- proper container, promptly sent to laboratory
- obtain specimen before antimicrobial treatment
Identification of Microorganisms from Specimens
Direct indentification methods:
- growth and biochemical characteristics
- microscopy
- molecular methods
- bacteriophage typing
- immunologic tests
Identification of Microorganisms from Specimens
Indirect identification methods:
- serology
- immunofluorescence
- PCR
Identification of Bacteria
How are most bacteria identified?
- culturing involves use of numerous kinds of growth media; can provide preliminary information about biochemical nature of bacterium
- additional biochemical tests used following isolation
Identification of Bacteria
What are some bacteria that are not routinely cultured?
rickettsias, chlamydiae, and mycoplasmas
Identification of Bacteria
How are rickettsias, chlamydia, and mycoplasmas identified?
- special stains
- immunologic tests
- molecular methods (PCR)
Identification of Bacteria
What is a common tool for bacteria identification?
dichotomous key
- gram-positive and gram-negative have separate charts
Identification of Bacteria
What are rapid methods for identification of bacteria?
- API 20E system
- automated/robotic systems for culture-independent identification
Identification of Bacteria
API 20E system
minaturization of biochemical tests to run 20 tests at once
Identification of Fungi
What is typical way to identify fungi?
- culture; days to weeks to grow
Identification of Fungi
What are types of medias fungi can be grown on?
- antibiotic agar
- caffeine agar
- cornmeal agar
- malt agar
- malt extract agar
- SAB
- SAB + chloramphnical + cycloheximide
Identification of Fungi
What are fungi cultures evaluated for?
- growth rate
- appearance of growth on at least one selective and one nonselective agar medium
- colongy morphology, color, and dimorphism
Microscopy
What types of specimen can be examined?
- wet-mount
- heat-fixed
- chemically fixed
Microscopy
Choice of microscopy depends on possible pathogen,
bright-field or phase-contrast for morphological identification
Microscopy
non-specific stains
- gram stain and acid-fast stain for bacteria
- calcofluor white for fungi
Microscopy
Direct immunofluorescence
- detects antigen
- if pathogen is present in specimen, then it will fluoresce after processing
- used to detect bateria, viruses, and fungi
Microscopy
indirect immunfluorescence
- detects patient antibodies to specific pathogens
- if antibodies are present in patient serum, then it will fluoresce after processing
- most commonly used for detecting viruses
Molecular Methods
What are the benefits of molecular identification methods?
accurate, routine, and sensitive
- comparison of proteins
- nucleic acid-based detection methods
Molecular Methods
What are molecular methods widely used?
- nucleic acid probes; DNA hybridization
- PCR and real-time PCR
- Ribotypiing (16s rRNA analysis)
- multilocus sequence typing (MLST)
Ribotyping
Ribotyping is based on high level of ?? gene conservation among bacteria.
16S rRNA
Ribotyping
What is ribotyping used for?
used to identify bacterial genera
Ribotyping
rRNA ?? are amplified by PCR.
encoding genes or fragments
Ribotyping
The ?? of the amplified DNA is determined and compared with those in the Nationals Center for Biotechnology (NCBI).
nucleotide sequence
Immunological Techniques
immunological techniques
detection of antigens or antibodies in specimens
- especially useful when cultural methods are unavailable or impractical or antimicrobial therapy has been started
Immunological Techniques
What are the advantages of immunological systems techniques?
- easy to use
- gives relatively rapid reaction endpoints
- sensitive and specific
Immunological Techniques
What are the caveats?
- lack of antibody does not always indicate lack of infection
- immunosuppressed patients may not respond to pathogen
Serotyping
serology
identification or measurement of antibodies directed against a specific microbe in the patient’s serum
Serotyping
What is the advantage?
can be used to differentiate serovars or serotypes of microbes that differ in antigenic compostion of a structure or product
Agglutination
agglutination
visible clumps or aggregates of cells or particles
- rapid plasma reagin test: diagnostic for syphilis
- latex agglutination tests
Agglutination
Viral hemagglutination test uses antibodies cross-linked to ??.
RBCs and surface antigens
Agglutination
What are thing can agglutination tests measure?
antibody titer
Complement Fixation
Complement fixation involves…
binding of complement to an antigen-antibody complex
Complement Fixation
What are complement fixation tests the basis for?
diagnostic tests that determine if antibodies to an antigen are present in a patient’s serum
Complement Fixation
In regards to sensitivity, complement fixations are…
very sensitive, measure extremely small amounts of antibody
ELISA
one of the most widely used serological tests
direct ELISA
test can be used to detect antigens in a sample
indirect ELISA
test can be used to detect antibodies in a sample
How are ELISAs visualized?
addition of chromogen
Immunoblotting (Western Blotting) Procedure
- proteins separated by electrophoresis, transferred to nitrocellulose or polyvinyl difluoride sheets
- protein bands visualized with enzyme-tagged antibodies
