Oral Micro Flashcards
Why is the mouth a good habitat for normal flora?
Moisture, warmth, and nutrients.
Are aerobes or anareobes more common as normal flora?
Anaerobes. The aerobes do come in and colonize first. Then anaerobes come in.
Dental Plaque
A well organized multi-species biofilm attached to the tooth surface.
Tartar
AKA calculus.
Calcified deposits on the teeth formed by the continuous presence of plaque. Rough surface provides an ideal place for new plaque to attach.
Biofilm
A community of mixed microorganisms encased within an exoplysaccharide matrix attached to a solid surface.
The ability to form a biofilm is a virulence factor that makes it harder for antibiotics and immune cells to get to organisms.
What factors affect plaque composition?
Location of the surface, age of person, and diet.
The formation of dental plaque is a systematic process.
A pellicle of salivary glycoproteins coats a clean tooth within hours.
The pellicle is colonized by gram positives (1st being Strep. mutans). The streptococci produce glucosyl transferases which convert sucrose to stick glucans. Streptococci contain glucan binding proteins to adhere to glucans.
Secondary colonizers adhere to gram positive within 1-3 days.
Tertiaries come inn within 5 days, inclding Aggregatibacter.
Dental Caries
AKA cavities.
An endogenous disease caused by opportunistic normal flora.
What is the shape and hemolysis of dental caries?
Gram positive alpha hemolytic (green on blood agar) cocci.
Strep. mutans.
What allows Strep. mutans to erode enamel?
It produces acid, which causes pain, tooth decay, and possibly tooth loss.
What is the most common chronic childhood disease in the U.S.?
Dental caries.
A patient presents with swollen, red, tender gums that bleed after brushing and flossing. He also complains of bad breath. What is the diagnosis?
Gingivitis.
A patient presents with swollen, red, tender gums that bleed after brushing and flossing with a loss of bone surrounding the teeth. What is the causitive agent?
Aggregatibacter actinomycetemcomitans, which is part of the normal flora.
Teeth can become loose.
What diseases are affected by oral infections?
Heart disease, diabetes, premature birth in pregnant patients.
What is the mechanism of oral infections causing systemic problems?
Bacteria in the mouth can use open blood vessels to get into the bloodstream (bacteremia) and can then bind to platelets using specific proteins and form clots. The clots can block vessels and cause heart attack.
Bacteria surround themselves with platelets and use them as protection against the body’s immune system.
What is Subacute Bacterial Endocarditis?
An infection of the lining of the heart or heart valves.
How does Subacute Bacterial Endocarditis occur?
Bacteria from the mouth enter the bloodstream, possible during dental procedures or from bleeding gums (gingivitis).
Travel to the heart and adhere to valves, forming a biofilm (Vegetation). They adhere best to artifical, abnormal, or damaged heart valves.
Over time, bacteria damage valves.
Clinical symptoms develop slowly; mitral valve is most commonly affected and a newly dx heart murmur is indicative.
Antibiotic Prophylaxis
Preventing transient bactermia will prevent the sequence of SBE even if a predisposing valvular lesion is present.
In case of bleeding, it prevents bacteria from adhering to valves.
A patient presents with persistent fever, fatigue, night sweats. On exam, you find an enlarged spleen, a newly diagnosed heart murmur, splinter hemorrhages under the nails, and painful osler nodes on fingers/toes. What is the diagnosis?
Subacute bacterial endocarditis.
How do you treat bacterial endocarditis if the valve has a biofim?
Removal and replacement of heart valves.
Your SBE patient’s lab work returns and says that the causative agent is alpha hemolytic on blood agar, gram +, and optichin resistant. What is it?
Strep. mutans.
Your SBE patient’s lab work returns and says that the causative agent is a gram negative rod that can grow with or without oxygen and prefers carbon dioxide. What is it?
Aggregatibacter.
Fastidious (hard to grow) and slow growing.
A patient presents to the urgent care clinic while you are doing rotations with a supprative abscess that makes their jaw appear lumpy. You aspirate the abscess and see fine grains of sand under the microscope. What are the characteristics of this causative agent?
Gram + branching rods that resemble hyphae of fungi. Anaerobic, non-spore forming.
Actinomyces israelii.
Can also have a “molar tooth” like appearance when grown on agar.
What is the name of the disease called “lumpy jaw”?
Cervicofacial actinomycosis.
A cancer patient presents to the PCP complaining of loss of taste, pain on swallowing, and a cottony feeling in the mouth. On examination, you find creamy white plaques on the buccal mucosa and tongue. You scrape the lesion to diagnose. What are the characteristics of the causative agent?
Oval yeast that produces hyphae.
Candida albicans.
What tests are there for oral thrush (Candidiasis)?
KOH prep will destroy everything except fungi.
It will gram stain positive (purple).
What populations are at risk for developing Candidiasis in the mouth?
Infants without a fully developed immune system People with dentures Diabetics People on long-term antibiotics People on Chemotherapy AIDs patients
A patient presents to the dermatologist with several clear vesicles with a red base. You perform a tzanck smear to be sure, but what is your initial diagnosis? What are the characteristics of this organism?
HSV-1 infection.
DS DNA enveloped virus.
Once you are infected, you’re infected for life. The virus lies latent in the trigeminal ganglion and can be reactivated.
Cowdry Type A intranucular inclusion bodies and syncytia (multi-nucleated giant cells) are diagnostic.
What are some triggers of HSV recurrence?
UV-B radiation (sun) Fever Stress Menstruation Spicy, acidic fodos Any immunisuppression
What does a Tzanck smear of HSV-1 show?
Cowdry type A inclusion bodies and giant multi-nucleated cells (syncytia).
A three year old patient who spends his days at daycare presents with mild fever, sore throat, and malaise. He also has lesions on his oral cavity, palms, and soles of the feet. His mother is concerned, but you assure her that the infection is self-limiting. What are the characteristics of the causative agent? How is it transmitted?
SS+ stranded RNA, naked virus (Coxsackie A16).
Transmission: nose and throat secretions, blister fluid, stool.
