Microbiology Flashcards
Any cell that possesses a clearly defined nucleus is known as
A Eukaryote
Cells that lack a nucleus and other organelles are known as
Prokaryotes
A type of protein that causes disease by triggering abnormal folding of usually normal healthy proteins
Prions
Define an opportunistic pathogen
An organism that causes infection when opportunity/change in natural immunity arises e.g. in an immunocompromised individual
An organism that grows in a culture by accident is known as
A contaminant
The capacity of a microbe to cause damage to the host
Virulence
Define an exogenous infection
Infective material deriving from outside the body
Define an endogenous infection
Deriving from inside the body e.g. commensal bacteria, transfer from non-sterile to sterile site
What communities of bacteria are most prevalent on gingiva
Streptococci
Actinomyces
What communities of bacteria are most prevalent on the palate
Streptococci
Actinomyces
What communities of bacteria are most prevalent on the tooth surface
VERY COMPLEX
Streptococci
Neisseria
Actinomyces
Veillonella
Fusobacterium
What communities of bacteria are most prevalent on the tongue
Streptococci
Haemophilius
Veilonella
What communities of bacteria are most prevalent on the cheek
Streptococci
Actinomyces
Haemophilius
What communities of oral bacteria are most prevalent in the gingival crevice
VERY COMPLEX
Streptococci
Actinomyces
Gram negative anaerobic cocci and rods
Gram positive anaerobic cocci and rods
What community of bacteria dominates the oral cavity?
Streptococci
Where is streptococcus mutans most commonly found in the oral cavity?
Saliva and approximal plaque
Define approximal
Where contact points meet
Where is streptococcus sanguinis most commonly found in the oral cavity?
Tongue, saliva, approximal and subgingival plaque
Where is Actinomyces spp, most commonly found in the oral cavity?
Saliva, approximal and subgingival plaque
Define virulence factor
A component of a pathogen that contributes to it’s ability to cause disease
Name five main virulence factors
- Adhesin
- Invasin
- Impedin
- Aggressin
- Modulin
What is the function of adhesin
Enables binding of an pathogen to host tissue
What is the function of invasin
Enables invasion of host tissues
What is the function of impedin
Enables pathogen to avoid host defence mechanisms
What is the function of aggressin
Causes damage to host directly
What is the function of modulin
Causes indirect damage to host (via immune system)
Explain the route of infection of oral streptococci spread that could cause endocarditis
- Strep gain access to bloodstream
- Pathogens rapidly adhere via platelet fibrin deposition
- Some species can obtain intra cellular access
- Heart function impaired
Give some examples of bacterial mechanisms to evade host defence
- immunity at mucosal surfaces
- destroy immune cells
- interfere with inflammatory response
- evade innate immunity
- overcome acquired immune responses (change antigens)
What is the defining characteristics of gram-ve bacteria?
Outer membrane and lipopolysaccharide layer
Main role of gram-ve bacteria’s outer membrane
Binds to receptors on macrophages, B cells and other cells that stimulates release of acute phase cytokines
Define Koch’s Postulates
Four criteria designed to establish a casual relationship between a microbe and a disease
Anaerobes that cannot tolerate oxygen are known as
Strict anaerobes
Anaerobes that can survive with the presence or abscence of oxygen are known as
Facultative anaerobes
Define pericoronitis
Inflammation of soft tissues surrounding the crown of a partially erupted tooth
Define dental alveolar abscess
Localised collection of pus in the alveolar bone at the apex of tooth root
What type of anaerobe is streptococci angionosus?
Facultative
What type of anaerobes is prevotella spp. ?
Strict
What type of anaerobe is fusobacterium nucleatum?
Strict
What type of cell wall does strep anginosus have?
Gram positive
What type of cell wall does prevotella spp. have?
Gram negative
What type of cell wall does fusobacterium nucleatum have?
Gram negative
What bacterial community is mainly associated with dental abscess’
Streptococci anginosus
What bacterial community is mostly associated with gingivitis/periodontitis?
Prevotella spp.
What does GNAB stand for?
Gram negative anaerobic bacteria
What is often the cause of endodontic infections?
Pulpitis and recurrent infection following root canal treatment
What bacteria is associated with primary endodontic infections?
Streptococcus
What bacteria is common in recurrent endodontic infections?
Enterococcus faecalis (gram +ve)
What type of anaerobe is enterococcus faecalis?
Facultative
What bacteria can survive in very alkaline conditions, such as in calcium hydroxide and sodium hypochlorite treatment?
Enterococcus faecalis
Define ‘dry socket’
Localised infection following extraction where socket fails to heal
What bacteria are commonly associated with implantitis?
Streptococcus aureus
Streptococcus epidermis
What bacterium are associated with pulpitis/ root canal treatment failure?
Fusobacterium
Enterococcus
What bacteria is associated with dry socket?
Fusobacterium
What bacteria is involved in the diversification of plaque, and is also found in supra and sub gingival plaque?
Actinomyces
What bacteria is associated with root surface caries?
Actinomyces
What type of Actinomyces is described as very aggressive
Actinomyces Israelii
Where can the treponema bacterial group most commonly be found in the oral cavity?
At the base of teeth
What bacterium is commonly associated with chronic perio lesions?
Treponema denticola
P. Gingivalis
What bacteria is commonly isolated from moist sites (e.g. the scalp, ears, Genito-urinary tract)
Staphylococcus
What type of cell wall does staphylococci aureus have?
Gram positive
What type of cell wall does staphylococci epidermis have?
Gram positive
Where is staphylococci aureus usually found?
In the nose
Where would staphylococcus epidermis usually be found?
In the skin and mucous membranes
Is staphylococcus aureus coagulase positive or negative?
Coagulase positive
What would coagulase positive indicate in a test?
Presence of staphylococci aureus
Coagulase is a virulence factor of staphylococcus aureus? True or false?
True
Is staphylococci epidermis coagulase positive or negative?
Coagulase negative
Is there a working vaccine available for staph aureus? Yes or no
No
What bacteria is a leading causative agent in pneumonia and other respiratory tract infections?
Staphylococcus aureus
What bacteria is associated with toxic shock syndrome?
Staphylococcus aureus
What skin infections are associated wit staph aureus?
- rash
- folliculitis
-abscess - impetigo
- scalded skin syndrome
What is a superantigen?
Class of antigens that result in excessive activation of the immune system
What is the superantigen associated with toxic shock syndrome?
TSST-1
How does TSST-1 influence toxic shock syndrome?
It is a virulence factor that has the ability to overstimulate the immune system
Name two very important virulence factors of staphylococcus aureus
- Fibrinogen binding protein
- Coagulase
What are the two main roles of coagulase?
- Promote conversion of fibrinogen to fibrin and clotting
- Assists deposition of fibrin on surface and prevents phagocytes recognising them
What does PVL stand for?
Panton- Valentine Leukocidin
What is PVL?
A cytotoxin
What cell does PVL have a specific toxicity for?
Leukocytes
What infections is PVLA mainly associated with?
Sever skin infections and necrotising pneumonia
What antibiotic is used to treat severe staph infections such as MRSA
Vancomycin
What does MRSA stand for?
Methicillin resistant staphylococcus aureus
What salivary gland infections is S. aureus usually assorted with?
Acute bacterial parotitis
What antibiotics are used to treat acute bacterial parotitis?
Co-amoxyclav
Flucloxacillin
What is another term for group A streptococci?
Streptococcus pyogenes
What’s type of cell wall does strep pyogenes have?
Gram positive
Destruction of red blood cells is known as
Haemolysis
What is the type of haemolysis with largest risk?
Beta haemolysis
What type of haemolysis does strep pyogenes undergo?
Beta haemolysis
What does GAS stand for?
Group A Streptococcus