URTI - Respiratory Infections 2024 PDF

 Intended Student Learning outcomes o By the end of the session and reviewing the associated learning resources, the student should be able to: o List the common etiologic microbial agents responsible for upper respiratory tract infections o Describe the disease process caused by b...

 Intended Student Learning outcomes o By the end of the session and reviewing the associated learning resources, the student should be able to: o List the common etiologic microbial agents responsible for upper respiratory tract infections o Describe the disease process caused by bacterial and viral pharyngeal, laryngeal, sinus and ear infections. o Explain the pathogenic mechanisms associated with pertussis and diphtheria. o Outline the laboratory tools used for diagnosing URTI. o Outline the treatment of URTI. Common Cold (Rhinitis) mild acute upper respiratory tract infection characterized by mild “coryzal” symptoms. Aetiology: Rhinovirus: 30 – 50%: Belongs tp family Picornaviridae. Contains > 110 serotypes. Other: Coronaviruses. RSV ,Parainfluenza virus. Adenoviruses ,influenza.  Common Cold (Rhinitis) Transmission: air droplet or direct contact with infected secretion. Treatment: Clinically: the incubation period is 12- Mild self-limiting disease. 72 hours No specific antiviral drugs. Nasal congestion. Antibiotics are “NOT Nasal discharge (Rhinorrea). INDICATED” Sneezing. Sore throat. Symptomatic relief: low grade fever. (NSAID), antihistamine, dried cough. decongestants. Complication: Otitis media. sinusitis. Asthmatic exacerbation Streptococcus pyogenes: Pharyngitis Gram +ve chain forming cocci. Catalase negative. Invasive M protein: Hair like structure, attaches to the mucosal epithelial cells and Resist phagocytosis. Invasion and Spreading factors; Hyaluronidase and DNAse. Streptococcus pyogenes: Pharyngitis Strep Throat: 5 years – 15 years. Start with sore throat. Acute Pharyngitis and acute tonsillitis. Fever and Cervical lymph nodes enlargement Complications: Paratonsillar abscess (Quinsy). Retropharyngeal abscess. Post infection (Rheumatic fever). Streptococcus pyogenes: Scarlet fever Scarlet fever: Caused by Erythrogenic toxin: Super antigen. Bacteriophage encoded. Usually affects children. Accompanied by pharyngitis. Skin rash. Red “Strawberry” tongue.  Streptococcus pyogenes: Diagnosis 1. Specimen collection: Throat swab. 2. Gram Staining: gram positive cocci chain forming. (not very helpful) 3. Culture on blood agar: shows beta haemolytic colonies sensitive to Bacitracin disk. 4. Serological test: Group-A Lancefield grouping: latex agglutination or immunofluorescence. ASO , anti-DNAase and anti- hyaluronidase. Streptococcus pyogenes: Treatment Antibiotic based: Penicillin G. (the organism do not show resistance). Amoxicillin. Erythromycin , Azithromycin and clarithromycin as alternative in patients with penicillin allergy. Viral Pharyngitis: Exudative pharyngitis. Adenovirus 3,7and 14: Pharyngeal conjunctival fever: Occur as outbreaks in “prisons” “military recruits” and “schools”. EBV: infectious mononucleosis. Primary HSV. Viral Pharyngitis: Herpangina: acute febrile illness associated with small vesicular or ulcerative lesions on the posterior oropharyngeal structures (enanthem) caused by Coxsackievirus A.  Diphtheria A life threatening localized infection of the upper respiratory tract. Corynebacterium diphtheriae gram-positive rods “club Shaped” Arranged in V- or L-shaped or Chinese letters, showing Metachromatic granules. Diphtheria toxin: A-B polypeptide, Bacteriophage encoded. Inhibit protein synthesis, Results in cell death Diphtheria transmitted by droplet spread. Diphtheria is not common where immunization is used. It is found in developing countries as sporadic or epidemic.  Diphtheria Pathology: Locally: Cell death due to shut of protein synthesis by DT. destruction of upper respiratory epithelium (epithelial necrosis). Induction of acute inflammatory response. Formation of “Pseudomembrane”. Diphtheria Pathology: Pseudomembrane: Grayish, detachable Composed of: Fibrin. Leukocytes. cellular debris. Found as: Pharyngeal. Nasal. Tracheal. Laryngeal. Diphtheria Clinical finding: incubation period of 2 to 4 days. pharyngitis and tonsillitis. Pseudomembrane formation. Cervical lymphadenitis and neck Oedema (Bull Neck). Complications: Suffocation. Toxemia: Heart; myocarditis, arrhythmias and CHF. Cranial nerves: diplopia, dysphagia and dysphonia.  Diphtheria : Diagnosis Specimen: throat swab.(risky). Gram staining: not very helpful. CultureTellurite blood agar: Black colonies: reduction of K+ tellurite to tellurium (black colonies). Diphtheria : Diagnosis Toxigenicty tests: Elek’s test: toxin antitoxin precipitation test. ELISA PCR. Elek’s test Diphtheria : Treatment Notifiable disease. Ensure Clear air way and oxygenation (may use tracheostomy tube). Antitoxin: diphtheria toxin Immunoglobulins. Antibiotics: Penicllin G and Erythromycin. Diphtheria : prevention Diptheria vaccine: Toxoid. Part of triple vaccine (DTaP). 2 months 4 months and 6 moths. Booster dose at 1 year and 6 years (every ten years). Acute Epiglottitis Haemophilus influenzae type B Gram negative coccobacilli. Capsule: is formed of Polyribosyl Ribitol Phosphate (PRP). The capsule is Important for virulence(resistant to phagocytosis) Attachment of respiratory epithelium (pili and adhesins). Invasion of the respiratory epithelium. Endotoxin is toxic to the respiratory cilia. Acute epiglottitis: Inflammation of the epiglottis and surrounding tissues leading to obstruction of the airway. Mainly affect children. Sudden onset of fever, sore throat, hoarseness of voice and muffled cough. child has air hunger, inspiratory stridor. inflamed, swollen, “cherry-red epiglottis”. Haemophilus influenzae Diagnosis: Culture: providing the essential growth factors (X+V) Nutrient agar with supplemented X+V discs: Haemophilus influenzae only grows around XV disc. Other: Capsule : Quellung reaction and immunofluorescence. Haemophilus influenzae Treatment: Resistant to penicillin and ampicillin (β-lactamase production and modification of PBP) 3rd generation cephalosporins (ceftriaxone and cefotaxaeme). Laryngeotracheobronchitis: (CROUP). Inflammation and oedema of the subglottic, larynx and trachea. Subglottic obstruction. Children (6mnths-3yrs). Clinical: Aetiology: Hoarseness of voice. Parainfluenzavirus 1,2. barking cough. Other: Inspiratory Stridor. Influenza. Dysphagia Measles. (salivation). Pencil sign: RSV. subglottic narrowing Adenovirus. Pertussis (whooping cough) Highly contagious, Strictly human disease Transmission by aerosol droplet. mainly occurs in children and infants. Mortality is highest in patients 50 time/ day), end up by “whoop” and vomiting Convalescent phase : Frequency and severity of the cough will subside. PERTUSSIS Pertussis (whooping cough) Diagnosis: CBC: prominent leukocytosis with lymphocytosis >70%. Specimen: nasopharyngeal swab. Gram stain: gram negative coccobacilli. Culture: Bordet Gengou Medium: Blood agar containing glycerol. Colonies are described as “ Mercury droplet” Pertussis (whooping cough) Treatment: Erythromycin and Clarithromycin. Prevention: Vaccine: killed vaccine (combined DTP). Pertussis a cellular vaccine (PT toxoid and Fha).  Otitis Media –Inflammation of the middle ear –Common in infants and children (esp. < 3 yr) Etiology: Signs and symptoms Bacterial causes( 80%) –Otalgia Strep. pneumoniae (35%) –Fever Hem. influenzae (20–30%) Moraxella catarrhalis (10– –Irritability, lethargy, anorexia, vomiting 15%) –Hearing loss Strep. pyogenes (8–10%) Presence of fluid in the middle ear Staph. aureus (1–2%) –Tympanic membrane: discolored, Viral causes 10-20% bulging (Pus accumulation ) Treatment –Amoxicillin –Macrolides (Azithromycin ,Clarithomycin) –Second-line:Ceftriaxone –Duration of therapy: 10 days  Acute sinusitis Inflammation of paranasal sinuses (e.g. Frontal, Ethmoid , and Maxillary Sphenoid ) Etiology: BACTERIA 70% Treatment S. Pneumoniae –Mild disease H. influenzae Nasal or oral decongestants Anaerobs Saline and steam inhalation S. aureus –Moderate to severe disease (> 7 days) S. pyogenes – Amoxicillin M. catarrhalis – Beta-lactamase stable cephalosporin, Gram-negative bacteria –Macrolides or quinolone or Viruses 30 % doxycycline. – Duration of therapy: 10-14 days Signs and symptoms –Sneezing, rhinorrhea, nasal congestion and postnasal drip, aural fullness, facial pressure and headache, sore throat, cough , fever, and myalgia. Aspergillus Filamentous Ascomycetes. shows broad segmented hyphae dichotomous branching Forms Aspergillus head: rarely seen in tissues (ears and lungs) Important species: Aspergillus Flavus: Yellow- green colonies Aspergillus Fumigatus: blue - green Paranasal (sinus) Aspergillosis Types: Allergic Aspergilloma develop in patient with sinus obstruction and chronic sinusitis. Acute Invasive rapidly progressive mainly in immunocompromised Chronic invasive slowly progressive, granulomatous disease can be seen in normal healthy people commonly in maxillary sinus Treatment : Surgical excision Iitraconazole before and after surgery Zygomycosis (mucormycosis) Rhinocerebral mucormycosis. Black fungus. Rare, serious opportunistic infection caused by Rhizopus common cause of acute and rapidly fatal, invasive fungal infection in immunocompromised and diabetic patients. Treatment: Amphotericin B Posaconazole Surgical debridement Further reading Warren Levinson, Review of Medical Microbiology and Immunology, 17th Edition. Jawetz Melnick & Adelbergs, Medical Microbiology, 28th Edition. Greenwood Medical Microbiology, 18th Edition. Sherris Medical Microbiology, 7th Edition. https://asm.org/ https://www.medscape.org/infectiousdiseases