Bacteria Growth and Identification Flashcards
Why is it important to understand differences between host and bacterial cells?
ecological plaque hypothesis- describes the interaction between bacteria and the environment- important for insight into disease process.
Why is pili an important structure that sits on the surface of bacteria?
The oral bacteria can use these structures to adhere to other bacteria and tooth structures- can be antiphagocytic
What can bacteria growth kinetics tell us?
After time bacteria growth is exponential, and starts with 1 (doubling time of 20 min) after 8 hours you will have 16,777,216. Bacteria under right conditions can grow massivley
What is an example of selective agar and non selective agar?
non selective- blood agar
selective- mannitol salt agar
describe different atmospheric bacterial growth conditions
Aerobic = Oxygen
Capnophilic = Carbon dioxide
Facultative = With & without oxygen
Microaerophilic = require small amounts of oxygen
Anaerobic = without oxygen
What phase does bacteria go in after a lag phase (after it has acclimatised)?
Logarithmic phase
What do the different stages in bacterial growth kinetics have a impact on?
the pharmacodynamics of antibiotics
What are features of non selective blood agras?
will grow many different bacteria
helps to provide a broad overview
following an oral swab what agar plate would you tend to swab?
selective and non selective
What is the starting point for a gram stain?
is that we try to get a pure colony of the bacteria on to the agar- when we have the colony a gram stain is attempted
what are 4 dies used to try and identify bacteria in a gram stain reaction?
crystal violet, lugols iodine, acetone (decolourise it), red dye (counter stain)
What is the importance of the gram stain reaction?
gives us an insight into some bacteria physiology linked to cell wall, this gives insight into classification and disease, and what type of antibiotic is needed
what colour do gram positive bacteria stain
purple- large and thick peptidoglycan that sticks to the stain
Gram negatrive bacteria
peptidoglycan layre is very thin, the gram stain does attach- counter stain red/pink allowing us to see
What is the difference between endotoxin and exotoxins?
exotoxins- generally proteins produced inside the cell then excreted out- both gram pos and neg
endotoxins- this comprises fragments of the bacteria cell walls- gram negavtive bacteria usually
what is another name for endotoxins?
lipopolysaccharide- causes symptoms of systemic diseases
endotoxins such as lipopolysaccharide can cause what?
sepsis
describe Gram stain shape- 1)cocci 2)strep 3)stafla 4) bacilli 5) spiral
cocci- round/ football shaped bacteria- pos and neg
strep- in chains not a direct shape but usually occurs with another such as streptococci
stafla- in clumps (not dircet) staflacocci
4- bacilli- cigar shaped rice/ rod- both neg and pos
5- spiral bacteria can cause acute ulcerative gingivitis- not good with gram stain
Describe the gram stain of pus?
helps make provisional diagnosis
gram positive in chains- helps guide a empirical antibiotic treatment
Gram positive cocci in chains are known as?
streptococci
what is a disease caused by streptococci?
dental caries
whats an example of a gram positive baciili infection?
clostridium tetinii
Give an example of gram negative cocci
neisseria meningitidis -meningitis
give an example of gram negative bacilli
black permanent anaerobe- prevotella intermedia- periodontal disease
What is a pathogen?
an organism which can invade the body and cause disease, such an organism is described as pathogenic
What are the two different types of s. aureus?
Methicillin Sensitive S. Aureus
Methicillin Resistant S. Aureus MRSA
What is meant by colonization?
the precense of micro- organisms in or on host, with growth and multiplication, but without any overt clinical expression at the time the micro organism is isolated- no antibiotics used
MRSA is transmitted easily in dental practice T or F?
true
What is meant by infection?
invasion of the body by pathogenic microbes and the reaction of the tissues to their presence and to the toxins generated by them
