Microbiology Quiz on Respiratory Pathogens

Internal Medicine Topics

• Increased blood cholesterol was noted as a potential concern (17).
• History of heart problems, hernia, or asthma was also noted (18).

Respiratory Infections

• Respiratory infections are a subject of study.

Respiratory Tract Outline

• Anatomy is a key component.
• Upper respiratory tract infections are discussed.
• Lower respiratory tract infections are also discussed.

Respiratory Anatomy

• Nasal cavity, including sinuses, is detailed.
• Pharynx, nasal conchae, nose, tongue, hyoid bone, trachea, bronchus, right lung, left lung diaphragm, bronchioles and alveoli and capillary network are featured.

Upper Respiratory Tract Anatomy

• The nose and nasal cavity, paranasal sinuses, pharynx, larynx are components.
• These comprise the conducting portion of the respiratory system.
• Air is transported to the alveoli.
• No gas exchange occurs here.
• Important: Patients with upper respiratory tract infections are not hypoxic.
• Diagnosing pharyngitis or bronchitis when hypoxic is incorrect; look for other causes (mostly lower respiratory tract infections).

Upper Respiratory Tract Structures

• Sphenoidal sinus,
• Superior meatus,
• Middle meatus,
• Pharyngeal tonsil,
• Opening of the pharyngotympanic (auditory) tube,
• Nasopharynx,
• Posterior nasal aperture,
• Uvula,
• Palatine tonsil,
• Fauces,
• Oropharynx,
• Laryngopharynx,
• Vestibular fold,
• Vocal fold,
• Esophagus,
• Frontal sinus,
• Cribriform plate of the ethmoid bone,
• Superior concha,
• Middle concha,
• Inferior concha,
• Vestibule,
• Inferior meatus,
• Nostril,
• Hard palate,
• Soft palate,
• Tongue,
• Lingual tonsil,
• Epiglottis,
• Hyoid bone,
• Thyroid cartilage,
• Laryngeal cartilages,
• Cricoid cartilage,
• Thyroid gland,
• Trachea.

Paranasal Sinuses

• Frontal,
• Ethmoidal,
• Sphenoidal,
• Maxillary

Respiratory System Functions

• Oxygen supply and carbon dioxide removal.
• Air filtration (mucosal membrane, cilia).
• Sound production.
• Smell detection.
• Water and heat release.
• pH regulation (lungs compensate quickly for acid-base disorders, unlike the kidneys which take 3-5 days).

Upper Respiratory Tract Infections

• Acute tonsillitis,
• Acute pharyngitis,
• Acute otitis media,
• Acute sinusitis,
• Common cold,
• Acute laryngitis,
• Otitis externa,
• Acute epiglottitis, are common types.

Upper Respiratory Tract Infections (Viral)

• Rhinovirus is the most common cause in adults.
• Parainfluenzae and RSV are common in children.
• The infection involves the upper respiratory tract, starting in the nasal cavity, and spreading throughout the airways.
• Often self-limiting, resolvng without specific treatment.
• Secondary bacterial infections can occur.

Pathophysiology of URIs

• Direct invasion of the mucosa lining the upper airway.
• Viruses are the most common cause.
• Bacterial infections can complicate viral URIs.
• Inoculation occurs when secretions touch exposed surfaces or inhaled from infected individuals.

Terminology

• Rhinitis: Nasal mucosa inflammation.
• Rhinosinusitis/Sinusitis: Inflammation of nares and paranasal sinuses.
• Pharyngitis: Pharynx inflammation.
• The pharynx, hypopharynx, uvula, and tonsils are involved.
• Diagnoses are made clinically due to inability to directly visualize these structures.

Epiglottitis and other upper airway inflammations

• Epiglottitis (Supraglottitis ): Inflammation of the superior portion of the larynx and supraglottic area.
• Laryngitis: Inflammation of the larynx.
• Laryngotracheitis: Inflammation of the larynx, trachea, and subglottic area.
• Tracheitis: Inflammation of the trachea and subglottic area.
• These are significant because they can cause upper airway obstruction.

Causative Organisms

• Children (<3 years): >100% viral infection
• Children (5-15 years): 15-30% GABHS (group A beta-hemolytic Streptococcus)
• Adults: ≈10% GABHS
• Most common streptococcus bacterium.

Streptococcal Infections—Signs and Symptoms

• Sore throat is a key symptom.
• Anterior cervical lymphadenopathy is frequent.
• Fever is often present (≥ 38 °C), especially if bacterial.
• Difficulty swallowing is typical.
• Headache and fatigue occurs.
• Muscle pain, nausea, and vomiting
• Tonsillar hyperemia and exudates, soft palate petechiae, and absence of coughing and nasal discharge are common presentations that distinguish bacterial from viral infection.
• Absence of hoarseness occurs because the infection occurs in the tonsil area.

Viral vs. Bacterial tonsillitis/pharyngitis

• Viral tonsillitis/pharyngitis may also have rhinitis, hoarseness, conjunctivitis, and cough.
• Oral vesicles or ulcers might be present in viral infections.
• Bacterial infections in the upper respiratory tract (tonsils and pharynx) are localized.
• Viral infections tend to be more widespread.

Exudates

• GABHS
• Presence of white discharge indicates a need for antibiotics.

Lymphadenopathy

• GABHS or other infections (Epstein-Barr virus, adenovirus, human herpesvirus type 6, tularemia, HIV) can create lymphadenopathy
• Important to note lymphadenopathy as a symptom for diagnosis purposes

Laboratory Diagnostic Tests for Tonsillitis/Pharyngitis

• Throat swabs are helpful.
• Rapid antigen tests.
• Antistreptolysin titer tests for streptococcal infections.
• White blood cell counts.
• Peripheral smears.

Tonsillitis and Pharyngitis due to Streptococci

• Supurative complications (abscess, neck stiffness, photophobia).
• Sinusitis, otitis, and mastoiditis are potential complications.
• Cavernous sinus thrombosis and toxic shock syndrome can arise.
• Cervical lymphadenitis is noted.
• Septic arthritis and osteomyelitis are severe possibilities.
• Repeat infections may occur.
• Nonsupurative complications
  • Acute rheumatic fever.
  • Acute glomerulonephritis.

Antibiotics for GABHS

• Oral: Penicillin V or Cefuroxime. Dosing and duration for children and adults are detailed.
• Parenteral: Benzathine penicillin is an injection method of treatment.
• Consider alternative antibiotics for penicillin allergy.

Acute Otitis Media

• S. pneumonia(30%), H. influenzae (20%), and M. catarrhalis (15%) are the common causes. Other bacteria include S. pyogenes (3%) and S. aureus (2%).
• No growth is present in 10-30% of cases.
• Treatments are typically empirical because accurately identifying the cause proves difficult.
• Chronic otitis media is complex.
• Requires culture identification to determine the correct treatment.

Acute Otitis Media (Symptoms)

• Symptoms are reviewed, including otalgia, ear pain, hearing loss, ear drainage, fatigue, fever, irritability and tinnitus/vertigo.

Acute Otitis Media (Frequency)

• 85% of children up to 3 years will experience at least one episode of acute otitis media.
• 50% experience at least two episodes.
• Most cases resolve spontaneously.
• Antibiotics are rarely necessary.

Acute Rhinitis/Sinusitis

• Acute sinusitis is commonly caused by S. pneumoniae (41%), H. influenzae (35%), M. catarrhalis (8%).
• Other causes include streptococcal pyogenes, S. aureus, rhinovirus, parainfluenzae.
• Chronic sinusitis is different.
• Caused by anaerobic bacteria (Bacteroides, Fusobacterium), S. aureus, streptococcal pyogenes, Gram-negative bacteria, and fungal organisms.
• Symptoms last for more than three months.

Acute Bronchitis

• Typically viral in origin.
• Rhinovirus, parainfluenzae, RSV, and flu are common causes.
• Chest pain, expectoration, fever, dyspnea, wheezing, and fatigue are symptoms.
• Adenovirus may cause bronchitis and gastrointestinal issues.
• Coughs can last for up to three weeks after other symptoms resolve.

Secondary Bacterial Infections in Bronchitis

• Secondary bacterial infections are rare (5-10% of bronchitis cases).
• H. influenzae, S. pneumoniae, and S. aureus are common bacterial causes of secondary infections.

Bronchitis Diagnosis

• Usually clinical.
• Chest X-rays are typically normal.
• Antibiotics are typically not needed.
• Use if secondary bacterial infection is present and tested as such.

Pneumonia

• Inflammation of alveoli of lung parenchyma with consolidation and exudation.
• Symptoms include cough (at first dry, later with sputum), pleuritic chest pain, and purulent sputum production; Fever.

Community-Acquired Pneumonia

• An infection of the lung parenchyma in non-hospitalized or long-term care facility residents.
• Common causes include S. pneumoniae (60-70% of CAP cases), H. influenzae, Moraxella, K. pneumoniae (Friedlander's bacillus), chlamydia pneumonia, and S. aureus.

Nosocomial Pneumonia

• Hospital-acquired pneumonia that arises 48 to 72 hours after endotracheal intubation.
• Risk factors include mechanical ventilation.
• Bacterial causes are varied. More frequent use of anaerobes, enterobacteriaceae, gram-negative rods, acinetobacter, or pseudomonas species and MRSA.

Streptococcus pneumoniae

• Gram-positive diplococci.
• Often causes CAP.
• “Typical” symptoms include malaise, shaking chills, fever, rusty sputum, pleuritic chest pain, cough.
• Lobar infiltrate on chest x-ray.
• 25% develop bacteremia.

Atypical Pneumonia

• Caused by atypical microorganisms (mycoplasma, chlamydia, legionella).
• Usually less severe symptoms than typical pneumonia.
• Usually non-productive cough without consolidation.
• Often occurs at the initial stages.
• Distinguishing features include time of onset or presence of extra-pulmonary symptoms (e.g. anemia, rashes, headache, sore throat).

Other Bacterial Pneumonia

• Causative bacteria such as anaerobes, klebsiella, morexella catarrhalis, and Staph are possible causes.
• Often associated with aspiration pneumonia, skin disease, and IVDU.

Viral Pneumonia

• Common in children (viral causes most common).
• RSV, influenza, and parainfluenzae infections are common causes in all ages; with flu being most common in adults.
• Secondary bacterial infections can occur (post-influenza pneumonia).
• Common bacterial causes are S. pneumo and staph aureus.

Investigations for Pneumonia

• Blood cultures, respiratory specimens (for viruses, chlamydia, mycoplasma), urine tests for legionella and pneumococcal antigen testing, sputum culture with gram stain, bronchoalveolar lavage, and pleural fluid analysis.

Infiltrate Patterns

• Lobar, patchy, or interstitial patterns on chest X-ray.
• Certain patterns are strongly indicative of specific diseases.

COVID-19

• Novel coronavirus causing a global pandemic.
• Symptoms include fever, dry cough, tiredness, aches, pains, sore throat, diarrhea, conjunctivitis, headache, loss of taste or smell which often occurs without accompanying nasal congestion and runny nose, rash on skin, or discoloration of fingers or toes.
• Serious symptoms can be rapid deterioration, shortness of breath, chest pain, pressure, or speech and movement loss.
• Laboratory features such as lymphopenia and elevated D-dimer may occur with Covid19 pneumonia.

Pneumonia Management

• Based on patient characteristics, including comorbidities and whether they have been previously hospitalized or are immunocompromised.
• Choice of antibiotic can depend on various factors.

Pneumonia Prevention

• Smoking cessation.
• Influenza vaccination per ACIP recommendations, including inactivated vaccine for people over 50 and those at risk for influenza complications, and intranasal live, attenuated vaccine for people 5–49 years old without chronic underlying disease.
• Pneumococcal vaccination for those at high risk.