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
Where is strep pyogenes most commonly found?
Throat and skin
Examples of disease associated with GAS
-impetigo
-cellulitis
-necrotising fasciitis
-acute streptococcal gingivitis
What is rheumatic fever?
Inflammatory condition affecting various parts of the body, usually a following complication of strep throat
What are the symptoms of bacterial sore throat
-nausea
-vomiting
-stomach ache
What are the symptoms of viral sore throat
-cough
-swelling in throat
-runny nose
What type of sore throat is more severe? Bacterial or viral?
Bacterial
Define scarlet fever
Severe form of strep throat with associated rash ( caused by strep pyogenes)
What antibiotics can be used to treat strep pyogenes infection
Pen V
Amoxicillin
Erythromycin
What are the major virulence factors associated with strep pyogenes
- M protein
- Hyaluronic acid
Which virulence factor of Strep pyogenes plays a role in evasion of the immune system?
M protein
Name the important bacteria associated with upper respiratory tract infections
- streptococcus pyogenes
- bordetella pertusis
- corynebacterium diphtheria
- haemophilus influenza
What bacteria is most commonly found in upper respiratory tract infections?
Streptococcus pyogenes
What bacteria causes whooping cough?
Bordatella pertusis
What type of bacteria is bordatella pertusis?
Small gram -ve cocci
In what group of individuals does whooping cough most often present?
Children
What are the characteristics of whooping cough?
Highly contagious
Life threatening
Severe cough lasting 2-3 weeks
What antibiotic ( and for how long) is often used to treat whooping cough?
Erythromycin for 14 days
How does bordatella pertusis present in the respiratory tract?
Attaches to ciliates epithelial cells
What promotes the attachment of bordatella pertusis to epithelial cells in the respiratory tract?
Virulent proteins
What is the key toxin associated with bordatella pertusis?
Tracheal cytotoxin (TCT)
What type of bacteria is corynebacterium diphtheria?
Gram +ve bacilli
What structures of the upper respiratory tract are effected by diphtheria?
Throat and pharynx
What is the characteristic clinical appearance of diphtheria?
Swollen neck (medical emergency)
What is the immediate treatment required to treat diphtheria?
Inoculation with diphtheria antitoxin
What antibiotics are used to treat diphtheria?
Penicillin or erythromycin
What type of bacteria is haemophilius influenza?
Gram -ve bacilli
What bacteria can cause both upper and lower respiratory tract infections?
Haemophilius influenza
What form of Haemophilius influenza is the most significant cause of mortality?
Capsule type B ( Hib)
What is the benefit of a capsule surrounding bacteria?
It protects bacteria from phagocytosis
what are the important bacteria associated with lower respiratory tract infections?
- Haemophilius influenza
- streptococcus pneumoniae
- mycobacterium tuberculosis
Acute inflammation of the lungs often caused by streptococcus pneumoniae is known as?
Pneumonia
Define lobar pneumonia
Bacteria has travelled deep into lungs and alveoli
What type of cell wall does streptococcus pneumoniae have?
Gram +ve
What bacteria does optochin identify?
Streptococcus pneumoniae
What is the importance virulence factor associated with strep pneumoniae called?
Pneumolysin
what complex capsular type of strep pneumoniae has made vaccine development difficult?
Alpha- haemolytic streptococcus
What are the three important symptoms of strep pneumoniae infection?
-abrupt onset
-high fever
-severe pain
What type of cell wall does myobacterium tuberculosis have?
Gram +ve
How does oral tuberculosis present?
As secondary lesions found at the back of the mouth
What is the importance of myobacterium tuberculosis’ ‘waxy cell wall’?
It allows survival in the atmosphere and prevents desiccation
What is the primary antibiotic used to treat tuberculosis?
Isoniazid
Isoniazid is used to treat tuberculosis, what other antibiotic can be used?
Rifampicin
What is the importance of legionella pneumphilia in dental practices?
This bacteria lives in water supplies. Highlights the importance of dental waterline management.
What is the main oral streptococci that causes dental caries?
Streptococci mutans
What strep bacteria is responsible for dental abscesses?
Strep anginosus
What type of cell wall do majority of cariogenic bacteria have?
Gram +ve
What are the main features of strep mutans, as a cariogenic bacteria?
- binds to and colonises plaque on tooth surface
- acidogenic ( producing acid at a fast rate from sugar)
- acidification ( surviving at a low pH as they can tolerate high concentrations of acid)
What bacteria has the largest number of genes associated wit sugar transport and utilisation?
Strep mutans
What surface proteins of S.mutans are important for colonisation and attachment?
Antigen I/II, Glucosyl transferase and Lucan binding protein
What surface protein of S.mutans is key for it’s attachment to biofilm?
Antigen I/II
What are the four main lactic acid producing oral microbes?
- oral streptococci
- lactobacilli spp.
- Actinomyces spp.
- Rothia denticariosa
Which pathogenic oral microbe is associated with progression of carious lesions?
Lactobacilli spp.
What bacteria has historically been reported as associated with root surface caries?
Actinomyces spp.
What cariogenic role does rothia dentocariosa have?
Colonises supra- gingival plaque
What is the ecological plaque hypothesis (put simply)?
Communities may be more or less susceptible to becoming dysbiotic (not everyone gets caries under the same circumstances)
What potential does veillonella have as a beneficial member of the oral microbiome?
High numbers of veillonella in dental plaque are thought to raise the plaque pH and reduce cariogenic its of plaque
What are the two different types of interaction that can present in dental biofilm?
Co-operative ( synergistic/ beneficial) and competitive ( antagonist/ inhibitory)
The substance released by one bacteria that kills another usually by inducing metabolic block is known as?
Bacteriocin
What is quorum sensing?
The process of cell-cell communication that allows bacteria to share information about cell density and adjust gene expression accordingly
What are the main factors that influence the biofilm environment colonised by S. mutans?
- extracellular polymeric substances
- DNA
- bacteriocins
- quorum sensing molecules
What are the main virulence factors of cariogenicity?
- adhesion
- acidogenicity
- acid tolerance
What bacteria is commonly associated with pulpitis?
Enterococcus
What bacteria are often associated with caries?
Streptococcus, lactobacilli, fusobacterium etc.
What bacteria are usually associated with periodontal conditions?
GNAB’s, anginosus group prevotella, and porphyramonas
What bacteria has resistance issues and is commonly seen in head and neck infections again and again?
Prevotella
What bacteria is commonly found to be associated with dry socket?
Treponema denticola
How would you treat dry socket with antibiotics?
Use of metronidazole
What bacteria is associated with implantitis?
Staphylococcus
Which plaque hypothesis is applicable to gingivitis?
Non-specific plaque hypothesis
Why type of bacteria (cell wall) dominate in supra and subgingival disease?
Gram +ve
What type of bacteria (cell wall) are more abundant subgingivally compared to supragingivally?
Gram -ve
What is the name of the group of gram -ve anaerobes that dominate subgingivally?
GNAB’s
Name the three most abundant bacteria sub-gingivally
- Streptococci
- Actinomyces
- Eubacterium
What did the pioneering studies of Loe investigate?
The relationship between plaque and gingivitis
What were the two key findings of the studies of loe?
- gingivitis develops with the appearance of supra-gingival dental plaque
- gingivitis resolves with loss of supra-gingival plaque
What were the four key conclusions found in the studies of loe?
- Ceasing OH leads to plaque build up and gingivitis
- OH allows for gingivitis to reverse and healthy gingivae to be restored
- Chlorohexidine could remove plaque and return gingiva to health
- With plaque accumulation, more gram -ve anaerobic bacteria was present
How many plaque hypotheses are there?
Three
The hypothesis that states: “dental caries was an infection with specific bacteria in the dental plaque, of which most were mutans streptococci.”
Specific plaque hypothesis
The plaque hypothesis that states: the idea that the accumulation of dental plaque was responsible for oral disease, with no single organism being responsible.
Non-specific plaque hypothesis
The plaque hypothesis which states: disease is a result of an imbalance in micro flora due to ecological stress.
Ecological plaque hypothesis
Which gram-ve anaerobe is largely involved in the pathogenesis of periodontitis?
Porphyramonas gingivalis
Which gram -ve facultative anaerobe is associated with localised aggressive periodontitis?
Aggregatibacter actinomycetemcomitans
What are the key characteristics of periodontal disease?
- true pockets develop
- LOA
- bone resorption
- condition becomes irreversible
What pathogens are associated with chronic periodontitis?
Porphyramonas gingivalis, fusobacterium nucleatum and spirocheates
What pathogens are associated with rapidly progressive periodontitis?
Porphyramonas gingivalis, prevotella intermedia and fusobacterium nucleatum
What did socransky do in 1998?
Assayed for presence of 40 species of bacteria through DNA-DNA hybridisation
What was the result of socransky’s study?
Produced a red and orange complex of bacteria found in deep perio pockets
What three bacteria are the most abundant in the red section of socransky’s study?
- P. Gingivalis
-T. Forsythia
-T. Denticola
Certain low-abundance microbial pathogens that can bring about inflammatory disease by turning a normally benign microbiota into a dysbiotic one, are known as?
Keystone pathogens
What are endotoxins and their main function?
Components of Gram-ve bacterial wall with their main function being structural and protective
How does nitrogen metabolism counter development of a low pH environment?
Produces ammonia (alkaline) from protein breakdown in plaque
Bacteria shown to significantly contribute to periodontitis are known as?
Periopathogens
Name the 6 key periopathogens
P. Gingivalis
T. Forsythia
Prevotella
Fusobacterium nucleatum
T. Denticola
Aggregatibacter actinomycetemcomitans
Which periopathogen is metronidazole ineffective against?
Aggregatibacter actinomycetemcomitans
Which antibiotic reduces periopathogens and red/orange complex bacteria?
Metronidazole
What antibiotic in combination with metronidazole would be more effective in the treating sub-gingival disease and why?
Amoxicillin, would allow for effective treatment against A. Actinomycetemcomitans
What are the tow therapies used to treat sub-gingival disease?
Antibitoics
Mechanical plaque removal
What pathogen depends on host cells for reproduction?
Virus
What are the two structures of viruses?
Enveloped an non-enveloped
What are virus particles composed of?
- nuclei acid genome
-protein capsid - lipid envelope ( depending on structure)
Which virus has significance in oral and cervical cancer?
Papillomavirus (HPV)
Why do RNA viruses tend to form quicker than DNA viruses and what are the implications of this?
Because RNA is more unstable. This increases chance of mutations.
What are the three main problems associated with viruses?
- latency
- chronic/persistent infection
- cancer
What does treatment for viruses include?
Anti-viral drugs
Vaccines
What is vertical transmission?
Transmission from mother to child
What herpatic virus is associated with disease of pre-school children?
Primary gingivostomatitis
How would you treat primary gingivostomatitis?
With acyclovir
Describe latency of Herpes
Latency after primary infection is where the inactive from of the virus lives in sensory nerve cells (trigeminal ganglia) and can reactivate to re-infect mucosal surfaces
How many different antibiotics can GDP’s prescribe?
14
Why is pen V a more appropriate choice of antibiotic compared to amoxicillin?
Pen V has a narrower spectrum
What are antibiotics?
Drugs used to treat or prevent infections caused by micro-organisms
Why are antibiotics used?
To control/limit the impact of bacterial disease
What is antibiotic resistance?
The ability of bacteria to escape the action of antibiotics
Define bacteriostatic
Inhibit growth of bacteria
Define bactericidal
Kill bacteria
What beta lactam narrow spectrum antibiotic is active against gram +ve bacteria
Penecillin
what are features of an ideal antibiotic?
- selective toxicity/ minimal toxicity to host
- bactericidal
- long half-life
- appropriate tissue distribution
- no adverse drug interactions/ side effects
what part of bacterial cells does antibiotics mainly target?
Cell wall and ribosomes
What are limitations of penicillins?
- patients can be allergic
- rapid excretion results in frequent dosage daily
- resistance
Can co-amoxiclav be used on its own?
No, it does not have antibiotic properties by itself, should always be paired with another antibiotic
What antibiotics target protein synthesis?
- doxycycline
- erythromycin
- clindamycin
What group of antibiotics is useful for treating infections where bacteria ‘hide’ from the host’s immune system?
Macrolides ( e.g. erythromycin)
How is metronidazole activated?
Activated in cytoplasm by reduction under anaerobic conditions ( e.g. damages DNA)
what antibiotic is active against anaerobes and some parasites?
Metronidazole
What are the 4 main antibiotics prescribed by dentists? in order of most popularly used.
- amoxycillin (67%)
- metronidazole (27%)
- Erythromycin (3%)
- Pen V (1%)
What are the two types of antibiotic resistance?
Natural and acquired
What is the subpopulation of cells that resist treatment and become antimicrobial TOLERANT by changing to a state of dormancy?
Persistor cells
What is horizontal gene transfer (HGT)?
A resistance gene can be passed within species by HGT thus spreading resistance
What should you always aim to use before antibiotics as a gdp?
Local measures
What is empiric prescribing?
Broadly targeting a condition when unsure exactly what is causing the issue
What does metronidazole interact badly with?
Alcohol
What infection do broad spectrum antibiotics increase the risk of?
C. Difficile
What can over-prescribing result in?
- drug resistance
- overgrowth/infection by other microbes
- contribute to evolution of pathogens
- reduce colonisation resistance
What are two local measures that should be considered before antibiotics are prescribed?
- extraction
- incision and drainage of pus
What bacteria can have a healthy effect on the oral cavity, by breaking down food, absorbing nutrients and fighting off other harmful bacteria?
Lactobacilli
