Flashcards in Micro - Pharyngitis, otitis, epiglottitis, sinusitis Deck (54)
What are the most common causes of pharyngitis?
Young children and adults most commonly viral
Older children usually strep pyogenes (group a), viruses, mycoplasma pneumoniae
What is the microbiology of corynebacterium diphtheriae?
Aerobic, non motile, non spore forming, non encapsulated, gram positive rod with clubbed ends
Grows on loeffler's medium or medium with potassium tellurite
How is corynebacterium diphtheriae transmitted?
From patient or asymptomatic carrier through nasopharyngeal secretions or skin lesions
What is a pseudo membrane produced by corynebacterium diphtheriae?
Induced by diphtheria toxin and is dirty grey colored leathery membrane covering tonsils and may extend to larynx
Should NOT be removed because of risks
What is bull neck?
Extensive pseudo membrane from corynebacterium diphtheriae involvement of pharynx associated with cervical adenopathy and severe neck swelling
Accompanying upper airway obstruction
What is the virulence factor of corynebacterium diphtheriae?
Can act locally to produce pseudo membrane or systemically to affect heart or peripheral nerves (effects depend on how much toxin absorbed)
Phage encoded AB toxin - tox gene is necessary and sufficient or disease
B interacts with receptor and A ADP ribosylates EF2 which blocks protein synthesis - one A sufficient to inactivate all EF2 in cell
How can one be immunized against diphtheria?
Antitoxin can treat along with antibiotics
DTaP vaccine - toxoid for diphtheria toxin and tetanus toxin with acellular pertussis components
How can strep be distinguished from other gram positive bacteria?
They do not have catalase - cant break down hydrogen peroxide and have negative reaction
What are the three different kinds of hemolysis by strep?
Alpha - colony surrounded by partial zone of clearing with green coloring, incomplete hemolysis (s. pneumoniae, viridans strep comprising normal oral flora)
Beta - surrounded by clear zone, complete hemolysis (s pyogenes)
Gamma or non - no hemolysis (enterococcus)
What are the lancefield groups?
Further classify beta hemolytic strep based on group specific carbohydrates
How can group a beta hemolytic strep (GABHS) be differentiated from other beta hemolytic strep?
Sensitive to bacitracin
How can GABHS (s. pyogenes) be further classified?
By m protein - cell attachment molecule
Virulence factor that correlates with certain diseases
Antibodies to m protein are protective - humoral immunity is type specific against certain strains only
What are the major virulence factors of s. pyogenes?
Adherence factors - m protein, ECM binding proteins (fibronectin), capsule
Invasion and spread
Toxicity - super antigens, exotoxins
Immune evasion - Ig binding protein, m protein, capsule, c5a peptidase
How is s. pyogenes transmitted?
Air - respiratory droplet
Food - prepared by person with open lesion
Rare transmission from fomites - bedding, clothing, etc
Most common is direct contact with saliva or nasal discharge from infected person
How does host immunity to GABHS work?
Antibodies against m protein, streptolysin o, or DNAase
Primarily opsonophagocytosis by neutrophils or PMNs
How is GABHS diagnosed?
Culture - aerobic growth, takes 1-2 days
Serology - anti streptolysin o or anti DNAase, minimum few days
Antigen detection - rapid detection of group a antigen directly from swab, minutes
Which types of strep infections cause which delayed sequelae?
Throat infection can cause either rheumatic fever or glomerulonephritis
Skin inf only causes glomerulonephritis
What are the suppurative vs. the toxin mediated diseases caused by strep?
Suppurative - pharynx, skin or soft tissue infection, other sites
Toxin mediated - scarlet fever, streptococcal TSS
What is the epidemiology of tonsillopharyngitis?
Children 5-15 yrs
Asymptomatic carriage can happen
Incubation 2-4 days
What are some key clinical features of strep?
Tonsil liar exudate
Soft palate petechiae
Can be distinguished from viruses by virus also having conjunctivitis, hoarseness, runny nose
How is strep treated?
Make sure treat only bacterial, not viral
IV penicillin if severe
I'm benzathine penicillin, one shot
Oral penicillin or amoxil for ten days
Oral macrolide or cephalosporin if allergy to penicillin
What are the general features of scarlet fever?
From organism that secretes SPE - encoded by lysogenic prophages = superantigens
mostly with pharyngitis but can happen with skin inf
What are the clinical feature of scarlet fever?
High fever and headaches
Sandpaper rash on upper trunk then spreads - palms, sole, and face spared and mouth has circumoral pallor, maculopular and blanches to touch
Pastia's lines - red lines in fold of skin around elbows, underarms, stomach and neck
Strawberry tongue progressing to raspberry tongue
May have desquamation of hands and feet
What are the three feature delayed sequelae have in common?
Evidence of preceding GABHS inf
Incubation of 7-21 days (1-5 weeks following inf)
No GABHS in damaged tissues
What is the pathogenesis of acute rheumatic fever (ARF)?
5-15 yr olds
Toxins - streptolysin o, SPE, and others cause direc injury
Cross reactive antibodies
What are the jones criteria for diagnosing ARF?
Major - carditis, polyarthritis, chorea, erythema marginatum on trunk or proximal extremities, subcutaneous nodules
Minor - clinical or lab evidence
2 major or 1 major and 2 minor with evidence of preceding GABHS inf
How can ARF be prevented?
Penicillin treatment of strep pharyngitis within 9 days
At least 10 days of therapy
For recurrent attacks - daily oral penicillin or monthly IM penicillin, prophylaxis at least 5-10 yrs or longer
What is the epidemiology and general clinical features of APSGN?
All ages, usually children
Repeat attacks rare
Clinical - dark urine, headache, back pain, edema, hypertension
What is the theory of pathogenesis of APSGN?
Immune complexes of strep antigen and host antibody within glomerulus
Anti strep antibodies directly cause injury
What is the treatment, outcome, and prevention of APSGN?
Usually resolves without damage
Occasionally permanent damage
penicillin not shown to prevent
What is acute otitis media?
Acute middle ear infection
What is otitis media with effusion (OME)?
Fluid in middle ear without signs or symptoms of AOM
Does NOT require antibiotics
TM is neutral or retracted
What is middle ear effusion (MEE)?
Fluid in middle ear - can be infected or not (AOM or OME)
How does AOM develop?
Viral URI --> Eustachian tube dysfunction --> OME --> normalize or AOM --> OME --> normalize
What is a possible complication of AOM?
TM can rupture and pus will leak out
What populations are AOM attacks most prevalent in?
Children younger than 2
Children attending daycare
What does diagnosis of AOM require?
History of acute onset of signs and symptoms
Presence of MEE
Signs and symptoms of middle ear inflammation
But really focus on appearance of TM
What are signs and symptoms of AOM?
Abrupt onset of symptoms
MEE has bulging TM with no mobility, air fluid level behind TM
Erythema of TM, distinct otalgia
What are the three bacterial pathogens responsible for most AOM (and bacterial sinusitis) and what are the chances each will resolve without antibiotics?
Strep pneumonia - 19%
H. Influenza - 48%
Moraxella catarrhalis (gram neg diplo) - 75%
What are the basics of the pneumococcus and its involvement in AOM?
Capsule protects from phagocytosis and is important virulence factor - different serotypes based on capsule
Serotype specific anti capsule antibodies protect against specific strains
Spleen principal organ that clears from blood
Can asymptomatically colonize but become symptomatic when clearance mechanisms are disrupted
What are the basics of h. Influenza and its involvement in AOM?
Gram neg coccobacilli
Not encapsulated - AOM, sinusitis, chronic bronchitis
Encapsulated, type b - meningitis, epiglottitis, pneumonia, cellulitis - protection from type b antibodies
Encapsulated type a, c-e - rarely cause disease
Why is simple observation recommended for some children with AOM rather than treatment?
Often mild and self limited
Low incidence of complications with good follow up
Could reduce antibiotic use - but start if symptoms persist or worsen
What affects spontaneous resolution of AOM?
Age dependent - greater in older children
Result of immune responses
Result of drainage via Eustachian tube
Which bacteria is responsible
What kinds of antibiotics are used to treat AOM?
Cephalosporins in penicillin allergic
H. Flu can produce bea lactamase
How can AOM be prevented?
Pneumococcal conjugate vaccine for infants - more has become due to h. Flu since this started
What is acute bacterial sinusitis?
Often preceded by viral URI
Mostly rhinovirus but also others
Anything leading to inflammation of nose and sinuses can predispose
How can we distinguish between viral URI and bacterial sinusitis to only give antibiotics for the latter?
Acute bacterial sinusitis has:
Onset with persistent symptoms lasting for more than 10 days with no improvement
Onset with severe symptoms, high fever, nasal discharge or facial pain for 3-4 days at beginning
Onset with worsening symptoms that last 5-6 days and were initially improving (doublesickening)
What are risks for antibiotic resistance in bacterial sinusitis?
Less than 2 or more than 65 YO, daycare
Prior antibiotics within last month
Prior hospitalization past 5 days
What are complications of sinusitis?
Potts puffy tumor (subperiosteal abscess and osteomyelitis of frontal bone)
Certain factors can predispose to chronic sinusitis
What is epiglottitis?
Cellulitis of epiglottis and adjacent structures
Can cause airway obstruction - medical emergency!
What population does epiglottitis occur in?
Kids between 2-6
Can happen in adults rarely
What bacteria classically causes epiglottitis?
H. Flu type b
Incidence has decreased since vaccine
What are the signs and symptoms of epiglottitis?
Difficulty swallowing or breathing (patient sits upright and forward)