Chapter 6 Flashcards
What are prokaryotes?
Class of unicellular life
What are the two domains of prokaryotes?
Archaebacteria and Eubacteria.
What is the difference between eukaryotic and prokaryotic cells?
Prokaryotic cells lack a distinct nucleus and cytoplasmic organelles.
Eukaryotic cells have a membrane-bound nucleus and other distinct organelles.
What is the bacterial cell wall composed of?
Peptidoglycans = polymeric compound not found in eukaryotes.
What is the purpose of the bacterial cell wall?
Provide mechanical support to the cell in the face of osmotic pressure. Prevents bacteria from collapsing or exploding.
Purpose of bacterial flagella?
Provide motility
What are fimbriae and pili and what do they do?
Hair-like projections that allow bacteria to adhere to surfaces and form a conduit for genetic exchange between cells.
Purpose of glycocalyx?
Protect bacteria from phagocytosis.
How do bacteria reproduce?
Simple cell fission (binary fission).
What are plasmids?
Extra-chromosomal DNA circlets, that contain genes that are capable of being transmitted to other bacterial cells.
What affects bacterial growth rate/ cell division?
Nutrient availability, temperature, pH, osmolarity.
What are endospores?
Produced when growth conditions are unfavourable. Are highly durable under harsh environmental conditions.
What happens to endospores when conditions are permissive?
Grow into vegetative bacterial cells>
How are bacteria differentiated?
- Stain
- Shape
- Special features
Stain
Gram stain (gram-negative or positive) = chemistry and structure of bacterial cell wall
Cell Shape
As they appear under microscope
-Cocci
-Diplococci
-Streptococci
-Staphylococci
-Bacilli
-Vibrio
-Spirochete
Special Features
Pathogenicity and antibiotic resistance
What does virulence depend on?
Ability to resist phagocytotic attack.
What does tissue injury depend on in pathogenic bacteria?
-Number of bacteria present
-Virulence, particularly the type of toxins it contains or produces
-Site of infestation
-Resistance of tissue
Bacterial Toxins importance in health care?
Both types produced by a range different bacteria and diffuse into blood and other fluids. Act at sites distal from the site of bacterial proliferation.
Gram-Positive Cocci
Staphylococci
-S. aureus
-S. epidermidis
Streptococci
-S. pyogenes
-S. agalactiae
-Viridans group of streptococci
-S. pneumoniae
What are some general characteristics of staphylococci?
-Common inhabitant = skin and mucous membranes
-Spherical cells arranged in irregular clusters (grapes)
-Lack spores and flagella
-May have capsules
Staphylococcus Aureus Characteristics
-Found widely in body (skin and nasopharynx)
-One of the most resistant of non-spore producing bacteria
What can S. Aureus cause?
Boils (furuncle), impetigo, wound infections, pneumonia, osteomyelitis (systemic), endocarditis.
Clinical scenarios for S. Aureus
-Infections around stitches
-In-dwelling catheters
-Prosthetic devices or foreign bodies where there are breaks in skin
S. aureus virulence factors (enzymes)
-Coagulase = enzyme that coagulates blood
-Hyaluronidase = digests CT
-Staphylokinase = digests blood clots
-DNase = digests DNA
-Lipases = digests oil; enhances colonization on skin
S. aureus virulence (toxins)
-Hemolysin = lyses cells (RBC)
-Leukocidin = lyse neutrophils and macrophages
-Enterotoxin = induce GI distress (food poisoning)
-Exfoliative toxin = separates epidermis from dermis (eyes or umbilicus of newborn)
-Toxic shock syndrome toxin (TSST) = induces fever, vomiting, shock, systemic organ damage (occurs in women with menstrual tampons)
S. epidermidis
Commonly found on body surfaces (skin vagina and gut) and is a commensal organism. Most common nosocomial infection.
Streptococci General Characteristics
-Gram positive, spherical, found in bead-like chains.
-Non-spore forming and nonmotile
-Can form capsules
-Species divided according to virulence
