Microbiology- bacteria Flashcards
What is the meaning of the word opportunistic pathogen?
only cause disease in compromised host, sometimes part of Normal Flora
What is the meaning of the word , virulence? How does LD 50 link in?
the quantitative ability of a microbe to cause disease
LD 50 stands for lethal dose 50 and indicates the dose of the organism required to kill 50% of the host under experimental conditions
What are Archaea bacteria?
live in extreme environments
not associated with disease in humans
What is the Type of DNA is found in bacteria?
Either a single circular chromosome or a plasmids (smaller circular DNA)
How do bacteria divide?
Binary fission
List 6 key features of bacteria? How do they help it be pathological
- No mitochondria (euk has)
- 70s ribosomes (euk,80s)
- Flagella- motility
- pili/fimbriae- adherence
- capsules- evade immune responce
- spores (resistant to physical and chemical agents)
- cell wall- protects against osmotic and mechanical shock. Adheres to host surfaces. protects against host immune system
What are the two main types of bacterial cell walls?
Gram positive
Gram negative
What is the difference between gram positive and gram negative bacteria?
Gram positive
- Thick peptidoglycan
- Techoic acid
- No outer membrane
Gram negative
- Thin peptidoglycan
- porins
- protein/lipids
- outer membrane
What are the different shapes of bacteria? And which type of bacteria (positive or negative) do these shapes coincide with?
Cocci- Gram positive
Rod- positive and negtaive
Curved- Gram negative
What are the different shapes of bacteria? And which type of bacteria (positive or negative) do these shapes coincide with?
Cocci- Gram positive
Rod- positive and negative
Curved- Gram negative
What colour are gram negative and gram positive bacteria after staining?
Gram negative- Pink
Gram positive- purple- thick cell wall holds stain
How are gram positive cocci divided then further subdivided?
Catalase test-
Staphylococci are catalase positive
Streptococci are catalase negative
Staphylococci divided into- coagulase positive or negative
Streptococci divided into- beta-haemolytic, alpha-haemolytic and non-haemolytic
How are gram positive cocci divided then further subdivided?
Catalase test-
Staphylococci are catalase positive
Streptococci are catalase negative
Staphylococci divided into- coagulase positive or negative
Streptococci divided into- beta-haemolytic-
alpha-haemolytic and non-haemolytic
When grown in blood agar beta heamolytic will leave a zone of red cell lysis around each colony
Which bacteria causes scarlet fever? What are hall mark symptoms?
Streptococcus pyogenes
Strawberry tongue (rash)
Fever
Which bacteria causes Erysipelas?What are hall mark symptoms?
Streptococcus pyogenes
infection of upper dermis; skin rash on legs, toes, face, arms and fingers.
Fever, chills, fatigue, headaches
Which bacteria causes Cellulitis?What are hall mark symptoms?
Streptococcus pyogenes/Staphylococcus aureus
spreading infection of the soft tissues
red, hot, swollen and painful- extreme sepsis
Which bacteria causes Carbuncle?What are hall mark symptoms?
Staphylococcus aureus
Cluster of boils
fever, general illness
Which bacteria causes impetigo?What are hall mark symptoms?
caused by Staphylococci and or Streptococci
Skin infection
Name 2 conditions caused by Staphylococcal enterotoxins
Acute staphylococcal enterocolitis
Staphylococcal “scalded skin” syndrome- upper skin layer lesions and high fever
What causes Toxic Shock Syndrome? List some symptoms
Staphylococcal Superantigens
High fever, low Bp, coma
Which bacteria causes chancre?What are hall mark symptoms?
Treponema pallidum
superficial skin lesion formed during syphilis
How is Protozoa classified?
Motility pseudopodia flagella cilia sporazoa (gliding)
What is Plasmodium species (malaria) classified as?
Apicomplexa (SPOROZOA)
Protozoa disease
What is Giardia (diarrhea, malabsorption) and Leishmania (leishmaniasis) classified as?
FLAGELLATES
Protozoa disease
What are the key features of fungi?
- can be unicellular (yeasts) or multicellular (molds and mushrooms)
- characteristics of plant life, but they are unable to perform photosynthesis
- Cell wall- chitin
- 80S ribose
membrane bound organelles
multiple linear, chromosomes
some haploid, some diploid
genes contain introns & exons DNA associated with histones
How does mold grow and reproduce?
grow as filaments (hyphae) which form a mesh (mycelium)
Reproduce by forming spores which can cause infections
How does yeast divide?
divide by budding
Describe the main characteristic features of Helminths – parasitic worms
multicellular eukaryotic organisms lacking backbones, notochords, or exoskeletons.
intestinal parasites
They are divided into TREMATODES (flat non-segmented worms,flukes) Schistosomiasis disease
CESTODES (flat segmented worms, tapeworms)
NEMATODES (roundworms & filaria).
What is the meaning of the term normal microbiota and where can you find it?
Meaning- microbiota that establishes perminant colonies in or on the body without causing disease
Locations- nose, somch, mouth, lungs, skin, gut vagina ureter
What is commensal bacteria?
Living in a relationship in which one organism derives food or other benefits from another organism without hurting or helping it.
What is the difference between Eukaryotes
and Prokaryotes? Which organisms fit into each category?
Prokaryotes- Contain DNA and RNA but no nuclear membrane and unicellular
- Bacteria and archaea
Eukaryotes- Possess DNA and RNA and DNA is enclosed in a nuclear membrane
- Human cells. fungi, algae, helmonths, arthropods
How can Beta-haemolytic streptococci be further divided?
Groups A-G exist
depending on lance field antigen
How is Staphylococcus epidermis and aureus differentiated
Using mannitol salt agar
Epidermis keeps agar pink
Aureus turns it yellow
What causes Gas gangrene ? List some symptoms
- Clostridium perfringens
- Septic shock, organ failure
