Principles of Bacteriology Flashcards
What is present in the wall of a gram + bacteria that is not present in a gram negative bacteria?
thick peptidoglycan layer
teichoic acid in wall
T/F: Spores are metabolically active.
false
How does bacterial infection cause fever?
endotoxin activates macrophages to release IL-1 and TNF, causing fever
Name 5 common zoonotic bacteria.
Borrelia burgdorferi, Brucella, Francisella tularensis, Yersinia pestis, Pasteirella multocida
Enterobaceriaceae: describe O, K, and H antigens
O - somatic, polysaccharide of endotoxin
K - capsular, related to virulence
H - flagellar, found in motile species
What kind of bacteria form spores and when?
certain gram + rods when nutrients are limited
Where is beta-lactamase in bacteria? What does it do?
periplasm of gram - bacteria
enzyme hydrolyzes beta-lactam antibiotics, conferring resistance
What molecule is specific to gram - bacterial cell membranes?
LPS
What are exotoxins and endotoxins, chemically speaking?
exotoxins tend to be polypeptides, while endotoxins are usually lipopolysaccharides
How could bacterial infection cause hypotension?
endotoxin induces macrophages to release nitric oxide -> vasodilation, hypotension
can also activate alternate complement pathway C3a, causing hypotension
Which organisms have exotoxin that acts by ADP ribosylation?
Corynebacterium diphtheriae, Escherichia coli, Vibrio cholerae, and Bordetalla pertussis
What helps organisms adhere to indwelling catheters?
glycocalyx (composed of polysaccharide)
Name the dominant normal flora on the teeth.
strep. mutans
Being in a newborn nursery is a risk factor for which two pathogens?
CMV and RSV
Name the dominant normal flora in the oropharynx.
strep. viridans
Name the dominant normal flora in the vagina.
Lactobacillus, E. coli, group B strep.
What disinfecting procedure kills spores?
autoclaving
Which pathogen is most associated with total parenteral nutrition?
Candida albicans
Where do bacteria keep their exotoxin or endotoxin genes?
exotoxin genes on plasmids or bacteriophages
endotoxin genes on bacterial chromosomes
T/F: we can vaccinate against exotoxins and endotoxins
false
we have toxoid vaccines against exotoxins for diseases like tetanus, botulism and diphtheria, but there are no vaccines against endotoxins
T/F: Spores are highly resistant to destruction by heat and chemicals.
T
Gram for gram, which is more fatal: exotoxin or endotoxin?
exotoxin
Name the dominant normal flora in the colon.
Bacteriodes fragilis > E. coli
How is catalase a virulence factor?
it degrades H2O2, an antimicrobial product of PMNs
Name the dominant normal flora of the nose.
Staph. aureus
Are vaccines available for encapsulated bacteria?
yes
What are two of the most common causes of nosocomial infections?
E. coli (UTI) and Staph. aureus (wound infection)
What are spores made of? What do they protect from?
keratin-like coat, dipicolinic acid
provide resistance to dehydration, heat and chemicals
What is the major surface antigen of gram + cell walls and which two cytokines does it induce?
teichoic acid - unique to gram + bacteria
induces TNF and IL-1
Spores have ___ acid in their core.
dipicolinic
What are the two pathogens most commonly associated with urinary catheterization?
E. coli, Proteus mirabilis
What is the most likely pathogen when a water source (water aerosols) is involved?
Legionella
Name four organisms with IgA proteases.
Strep. pneumoniae, N. meningitidis, N. gonorhoeae, H. influenzae
What pathogen is often found on respiratory therapy equipment?
Pseudomonas aeruginosa
What is the main virulence factor of encapsulated bacteria and how does it confer virulence?
polysaccharide capsule is antiphagocytic
Which has greater heat stability: endotoxin or exotoxin?
endotoxin
Name the dominant normal flora in the skin.
Staph. epidermidis
How might a bacterial infection cause disseminated intravascular coagulation?
endotoxin can activate Hageman factor which initiates coagulation cascade, causing DIC
Compare and contrast the cell walls of Gram +/-
Both have peptidoglycan (Gram+ is thicker layer)
Gram - has LPS and LOS
Gram + has Lipoteichoic acid
Compare and contrast antigenic variation and shift
Antigenic variation is the process by which bacteria alter the expression of certain genes in response to environmental stressors to promote survival and increase virulence. This process is faster than random mutation. An example of this is the changing of surface protein expression to avoid detection by host immune cells.
Antigenic shift is the exchange of genetic material between two subtypes of viruses to create progeny that is more virulent. This is commonly seen in influenza viruses.
What is a plasmid
Plasmids can contain genes for antibiotic resistance or toxins. These plasmids can be freely replicated and transmitted between bacteria.
If a bacteria is “competent” what does that mean?
3 examples
can facilitate the process of transformation (i.e., uptaking free genetic material from the environment and integrating it into the bacterial genome).
Neisseria species, Haemophilus influenzae type b, and Streptococcus pneumoniae.
Generalized vs. specialized transduction
Generalized - phage DNA not integrated into bacterial chromosome
Specialized - specifically integrated into the chromosome
Purpose of vanA gene?
Vancomycin resistance
Mostly seen in enterococcus species.
Endotoxins are made of __ found on the __ of ___
LPS on the outer cell membranes of Gram - bacteria.
MHCs bind ___ but not ___ , therefore they cannot present ___ to ___
bind peptide antigens, but not polysaccharides
therefore they cannot present endotoxins (made of polysaccharides) to TCRs (T cell receptors)
AB toxins are part of ___
how do they work?
Exotoxins
1) Component A, the active component, enters the cell and exerts a toxic effect.
2) Component B, the binding and uptake component, binds to the target cell to facilitate entry of the toxin into the cell.
Describe reassortment
what agent is best at this?
different strains of segmented viruses can combine to create a new viral subtype
Influenza - human + animal strain
