Basic Bacteriology Flashcards
What is the role of the clinical microbiologist?
Culture Organisms
Classification
Prediction
What are the characteristics of a prokaryote?
No organelles
Unicellular
Lacks nuclear membrane
No true nucleus
What are a family, a genus, and a species known as (These are the only ones we care about)?
General Taxonomy
What is taxonomy based on?
Macro/micro morphology
Staining
Nutrition
Physiologic/biochemical traits
Susceptibility/resistance
What has led to reclassification of some bacteria?
Genetic Relatedness
Current technology allows for further analysis of DNA/RNA
What is a phospholipid bilayer embedded with proteins that envelops the cell and regulates transport of molecules in and out of the cell?
Plasma Membrane
Hydrophilic polar heads
Hydrophobic nonpolar tails
What are the different cell appendages?
Cilia (Short)
Flagella (Long)
What is found free in the cytoplasm, attaches to the cytoplasmic membrane, and consists of RNA and proteins?
Bacterial Ribosomes
What produces the purple color of a gram positive cell wall?
Peptidoglycan Layer (Thick/Protective)
Not dissolved by alcohol
What produces the pink color of a gram negative cell wall?
Lipopolysaccharide (LPS) (Outer layer)
Thin inner Peptidoglycan layer
What are the outer membrane functions in a gram negative cell wall?
Acts as a barrier
Acts as a sieve (allows things in/out)
Provides attachment sites
What consists of a waxy layer of glycolipids and fatty acids?
Acid-Fast Cell Walls
What uses Carbolfuchsin to penetrate the cell wall by either heat (Ziehl-Neelsen) or by a detergent (Kinyoun method)?
Acid-Fast Stain
What are the basic shapes in bacterial morphology?
Cocci
Bacilli
Spirochetes
What does understanding the growth requirements of potential pathogens allow the microbiologist to do?
Select the correct media for culture and optimize the chance for isolation
What are the types of growth media?
Minimal
Enriched
Nutrient
Selective
Transport
Differential
MEN STD
What are factors that can influence microbial growth?
Temperature
Gaseous composition of atmosphere
pH
What are the growth curve phases of bacteria?
Lag Phase (Preparing to divide)
Log Phase (Numbers Increase)
Stationary (Bacteria remain constant)
Death
How can we determine cell numbers in bacterial growth?
Direct Counts
Plate Counts
Density
What does microbial metabolism consist of?
Biochemical reactions bacteria use to break down organic compounds
What are the mechanisms of gene transfer?
Transformation
Transduction
Conjugation
Restriction Enzymes
Which mechanism of gene transfer involves the uptake and incorporation of naked DNA into a bacterial cell?
Transformation
Which mechanism of gene transfer involves the transfer of bacterial genes by a bacteriophage from one cell to another?
Transduction
Which mechanism of gene transfer involves the transfer of genetic material from a donor bacterial strain to a recipient strain?
Conjugation
Which mechanism of gene transfer involves the cutting of foreign DNA at specific sequences?
Restriction Enzymes
Define pathogenicity.
Ability of an organism to produce disease in a host
What can cause an iatrogenic infection?
Medical treatment or procedures
Indwelling urinary catheters
What is Virulence?
Relative ability of a microorganism to cause disease
What is the most common mechanism for evading phagocytosis used by microorganisms?
Having a polysaccharide capsule on it’s surface
What are fimbriae (pili) and surface polysaccharides known as? What do they allow for?
Known as adhesive structures
Allow for attachment to host surface structures
What is localized invasion?
Penetration and growth in a few layers or one body area
What is dissemination?
Spreading from initial infection site to distant sites
What are poisonous substances secreted by organisms?
Toxins
What is an example of an Endotoxin and what do they cause?
Lipopolysaccharides (LPS)
Hypotension
Fever
Initiates Coagulation
What are examples of host resistance factors?
Physical Barriers (intact Skin)
Cleansing Mechanisms (tears, urine, mucus)
Low pH (stomach/Vagina)
Antimicrobial substances (fatty acids, HCl, lysozymes, immune proteins)
What is the best method for fundamental specimen collection?
Written handbook available for every patient to collect the highest quality specimen
What is the primary goal of specimen collection?
Maintain specimen near to its original state without deterioration or leakage
What specimen do we collect directly from the site of infection?
Lesions/Wounds/Abscesses
Needle aspiration
Sterile tube or anaerobe transport
What is often collected to detect bacterial pneumonia and requires the patient to deeply cough into a sterile container?
Sputum
What is the specimen of choice for gastrointestinal pathogens?
Stool
What is considered a critical weak link in the specimen management process?
Incomplete patient information
When would we like to transport specimens?
Transport within 30 min of collection
Preferably within 2 hours
How can we preserve urine? How can we preserve stool?
Urine: Boric acid
Stool: Refrigerate for 2 hours; Cary-Blair transport media if longer
Who governs the shipment of infectious substances?
Department of Transportation (DOT)
U.S. Postal Service
What is more than one specimen from the same source on the same day an example of?
An unacceptable specimen
What are the three key components of microscopy?
Magnification
Resolution
Contrast
Give the primary inoculations for fastidious and non fastidious organisms to grow.
Fastidious: Enriched media
Non-fastidious: Nonselective media
Give the primary inoculations for gram positive and gram negative.
Gram Positive: Selective media
Gram Negative: Differential media
Which isolation technique involves streaking into four quadrants?
Isolation streak
Organism concentration grading
Which isolation technique is used for urine cultures?
Quantitative Isolation
Uses loops with specific volumes
At what temperature do most cultures grow at?
Between 35C and 37C
