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RS Microbiology

Respiratory System Microbiology - Virology of Pharyngitis

Pharyngitis is: Inflammation of the pharynx secondary to an infectious agent
The most common cause of bacterial pharyngitis is: Group A β- hemolytic streptococci (S. pyogenes)
Pharyngitis often coexists with: Tonsillitis
Viral Causes of pharyngitis: Rhino and Coronavirus
Other causes of pharyngitis include: Adenovirus CMV Para-influenza EBV Herpes simplex type 1 virus enteroviruses such as Coxackie A virus & enterovirus71
Bacterial causes include S.pyogenes (mainly), Mycoplasma, and Arcanobacterium
Classic symptoms of pharyngitis: Fever, throat pain and dysphagia
In viral pharyngitis, fever is: Mild or absent
Viral symptoms: URI symptoms of rhinorrhea, cough, hoarseness, conjunctivitis & ulcerative lesions Conjunctivitis- in adenovirus Ulcerative lesions in herpes simplex type 1 virus and Picorona viruses or enteroviruses such as: coxsackie virus and enterovirus 71
Streptococcal symptoms: Associated headache and/or abdominal pain (especially in children) Fever and throat pain are usually acute in onset
What do you find on physical examination of the viral infections? *EBV and adeno are present with white exudate covering erythematous pharynx and tonsils & cervical adenopathy *Fatigue and myalgia
What do you find on physical examination of the bacterial infections? White exudate covering pharynx & tonsils. Tender anterior cervical adenopathy. Palatal/uvular petechiae (small reddish dots representing bleeding in mucous membranes) Scarlatiniform rash covering torso and upper arms
How are the viral and bacterial infections spread? Viral: Spread via infected saliva Bacteria: Spread via respiratory particle droplets
In viral pharyngitis, how long is the patient contagious? 3-5 days
In bacterial pharyngitis, how long is the patient contagious for? 24 hours
Differential diagnosis of pharyngitis is done by observing: pharyngeal exudates
Pharyngeal exudates are seen in: S. pyogenes, C. diphtheriae, EBV, Adenovirus and Oral Candidiasis
C. diphtheria doesn’t really form an exudate; it rather forms a: Grey-white fibrinous pseudomembrane
How is this pseudomembrane formed? Necrosis of pharyngeal cells that includes the debris & inflammatory cells
Oral Candidiasis -in immunocompromised patients- can be present with: Whitish coat or an oral thrush covering the tongue, the throat & the pharynx
Coxackie A virus is usually present with Gingivostomatitis
EBV is usually observed with: Hepatosplenomegally, rash, fatigue & Cervical lymphadenitis
In the case of a skin rash, you should think of: S. pyogenes (scarlet fever) , HIV or EBV
Conjunctivitis accompanied with pharyngitis is most likely caused by: Adenovirus
The non suppurative complications of bacterial pharyngitis: 1) Acute rheumatic fever - streptococcal-type 2 hypersensitivity 2) Acute glomerulonephritis -type 3 hypersensitivity
Infectious mononucleosis caused by: EBV
Herpangina associated with lesions that ulcerate is caused by: Coxackie A virus
Petechiae (small red dots) is more common in which infections? Bacterial
Clinical manifestations of bacterial pharyngitis: Rapid onset (starts with high fever and sore throat directly) Headache GI symptoms Sore throat, Erythma Exudates Palatine petechiae Enlarged tonsils Anterior cervical adenopathy Tender red & swollen uvula
Viral pharyngitis is characterized by: Gradual onset Rhinorrhea Cough Diarrhea Fever
Diagnosis is done by: For Strep.: Throat culture is the gold standard For Mycoplasma: we have cold agglutination test For Infectious Mononucleosis: we have CBC and spot test For viral pharyngitis: Based on clinical manifestations
Treatment is done by: *Penicillin in strep pneumonia *In viral pharyngitis, we give supportive care: Analgesics, anti pyretics, and fluids
Specific viruses involved in causing pharyngitis are: 1) Parainfleunza virus (HPIVs) 2) Respiratory Syncytial Virus (RSV) 3) Adenovirus
Characteristics of Parainfluenza virus: Negative-sense, ssRNA Enveloped 4 serotypes: 1, 2, 3, 4 Paramyxoviridae family F-protein for fusion to target cells & HN-tetramer
What is the pathogenesis of HPIVs? Secretions of high levels of inflammatory cytokines The peak duration of secretion is 7-10 days after initial exposure Increasing levels of certain chemokines, RANTES Macrophage inflammatory protein (MIP)–K detected in nasal secretion of paediatrics
4 serotypes of HPIV: Type 1 associated with acute croup and pharyngitis. Type 2 associated with acute laryngotracheobronchitis. Type 3 associated with LRTIs in children Type 4 associated with Upper Respiratory infections -least common Types 1&3 are most common.
What is croup? Laryngotracheobronchitis - the most common manifestation of HPIVs infection
In severe cases, you may need to: Give oxygen & you should start steroid therapy for a short period of time (7-10 days)
Is there a vaccine for HPIVs: No
Characteristics of RSV: ssRNA Enveloped Pneumovirus of the Paramyxovirus family Syncytial Microscopically: syncytia present as giant cells Considerable strain variation: classified into A and B Both subgroups circulate in the community at any one time.
Characteristics of RSV infection: Peak incidence: 2-5 months LRT infections (bronchiolitis & bronchopneumonia) May start as URTI 50-60% eventually end up with LRT infections May cause croup> not common. More severe in : Boys
Incubation period of RSV infection: 2-8 days
Transmission of RSV via: Ocular or nasal contact with infected secretions
Pathogenesis of RSV: Enveloped virus enters the cell Leaving the envelope with its spikes (glycoprotein) to become part of cell membrane Nearby cell receptors interact with glycoproteins fusion of the two membranes happens Giving a multinucleated giant cell
Higher levels of maternal Abs are associated with: Lower infection rates & prophylactic Abs No level of serum antibodies provides protection
What is seroconversion? The state of presence of Ab against a certain antigen or certain virus
Diagnosis of RSV is done by: Physical examination & hyperexpansion of the lungs Hyper-inflated lungs on chest x-ray & increased interstitial markings In severe cases, sample from a nasal wash or bronchoalveolar lavage & send it to a virology lab for culturing
Treatment and prevention of RSV: Adequate oxygenation Ventilatory support Observation for bacterial superinfection Antiviral drug is available: Ribavirin (aerosol) NO VACCINE available
What are the characteristics of adenoviruses? DNA virus Naked /icosahedral Antenna like projections from penton structures on the helix replication in the nucleus >100 serotypes 50-55% cause infection in humans
Proteins of adenovirus: Hexon and penton base fiber
Clinical syndromes caused by Adenovirus: Pharyngitis Pharyngoconjunctivitis Acute respiratory disease Pneumonia, Conjunctivitis Haemorrhaghic cystitis, Gastroenteritis Meningitis
Serotypes associated with pharyngitis 1,2,3,5 & 7
Serotypes associated with conjunctivitis: 3 and 7
Is there a vaccine for adenovirus? No vaccine available for the public, but vaccine for early military recruits
Created by: Ulaisl