30. DMD Respiratory Infections

upper - common cold, pharyngitis and tonsilitis, group A streptococcus, glandular fever, otitis and sinusitis, oral candidiais, epiglottis and laryngotracheitis, diphtheria, whooping cough

lower - bronchilits and bronchiolotis, influenza, pneumonia, tuberculosis

Risk factor for severe respiratory tract infection

"WEAKENED LUNGS"

1. Premature baby 

2. Immunocompromised

   1. steroids

   2. biological therapies that inferefere wiht immune receptors e.g target tnf --> dampen down immune respons e--> vulenrable to ifnection

   3. transplant e.g kidney transplant

3. Preceding viral damage

   • virus attracts neutrophils, attracts neutrophils (double edged sword) get lcoalised damage as well

   • bacterial superinfection ontop of

4. Chronic lung disease - cystic fibrosis, COPD, bronchiectasis, asthma

5. Ventilator association pneumonia

   1. being in ICU , big plastic tube, 

   2. esp gram-ve bacteria (e coli --> ventilator associated bacteria)

Diagnosis - of RTIs

1. Respiratory sample

   1. throat swab  --> PCR

   2. for bacteria need throat swab & sensitivity (to detect what bacteria it is)

   3. sputum 

   4. if TB need rly good specimen BAL' Lung biopsy --> 

2. Blood culture if signs of sepsis

   1. strep pneumoniae --> __ traid (check heart and brain)

   2. once it gets into bloodstream can seed in other places

   3. see if u can detect strep pneumonia in blood

3. Urine 

   1. urinary antigens for legionella/ pneumococcus

4. Serology: acute & convalescent era

   1. monospot or IgM for EBV

   2. ASOT (Group A streptococci)

      1. asot for post strep complications

   3. IgM/ IgG for Coxiella (Q fever), legionella

5. Other laboratory testing

   1. inflammatory markers: CRP, white cell count & differential

6. Imaging

   1. chest x ray

   2. CT

Upper Respiratory Tract Infections (URTIs)

Common Cold

• Mostly viral (Rhinoviruses: 100+ serotypes)

• inflammatory virus rich secretion

• inflammatory mediator

• Causes epithelial damage, cilia loss

• Transmitted - via droplets and hand contact

Pharyngitis & Tonsillitis

• inflammation of the pharynx and submucosal lymphoid swelling

• Viral (70%), bacterial (Group A Strep), fungal

• Symptoms: sore throat, ulcers on pharyngeal wall, exudates covering the tonsils

• Treat only bacterial with penicillin - gtoup A streptococci

Group A Streptococcus (GAS)

• Group A strep can be very bad pathogen if not treated propelry

• causes diverse range of skin, soft tissue & respiratory tract infections

• Infections caused by group A strep? (ICE)

  • Tonsiliits

  • Pharyngitis "strep throat"

  • Scarlet fever

  • Impetigo

    • sore blisters around mouth & nose mainly

  • Cellulitis

    • necrotising fascilitis 

• Sequelae - a serious complciation of untreated strep throat/ skin infections

  • a serious complication of inadequately/ untreated strep throat 

  • presents weeks after pharyngitis

  • autoiimune conditions

  • 2 types: Rheumatic fever (rare) & glomrulonephriits

  • 1) Rheumatic fever

    • type II hypersensitivty reaction (molecular mimicry) 

    • highest incidence in children

    • fever & affects multiple organ systems 

    • How? group A strep creates a protein that is v simialr to those on heart valve

      • results in damaged heart valves

      • presnets as heart murur

  • 2) Glomerulonephritis

    • immune complex mediated - type III hypersensitivty 

    • attach to glmerulus 

    • complement activation leads to inflammatory mediators

    • higher cindience in children

    • blood vessels in kidneys inflammed

    • blood in urine

    • THIS IS WHEN U DO ASOT TEST

• GAS (group A sterep)

  • Acute pharyngitis

  • Post streptooccal sequelae

• ★ Treatment

  • Penicllin

  • Erythromycin (if allergic to penicilin)

Glandular Fever (EBV)

• EBV

  Symptoms: sore throat, fever, lymphadenopathy, splenomegaly, excessive fatique

• Check for HIV if similar symptoms

Otitis & Sinusitis

• Complication of cold/pharyngitis

• infection of air spaces - sinuses, middle ear, mastoid

• Bacterial: S. pneumoniae, H. influenzae

• pus culture to diagnose

• Treat with Amoxicillin

Oral Candidiasis

• Due to Candida albicans after antibiotics (antibiotic reduces flora, allow C albicans to fluorish)

• diagnosis - scape culture

• Treat with nystatin, clotrimazole, fluconazole

Epiglottitis & Laryngotracheitis

• H. influenzae type B (epiglottitis), viral (croup)

• Stridor due to narrowed airway

• Treat: cefotaxime, chloramphenicol

Diphtheria

• C. diphtheriae, phage toxin

• Pseudomembrane in throat

• Treat: antitoxin + penicillin/erythromycin

• vaccine avaliable to prevent

Whooping Cough

• Bordetella pertussis, severe cough with whoop

• Complications in infants

• Treat: erythromycin, prevent with vaccine

Lower Respiratory Tract Infections (LRTIs)

Bronchitis & Bronchiolitis

• preceded by a upper RTI - influenza

• Often post-viral; H. influenzae, S. pneumoniae

• treat with tetracyclines or macrolides, flucoxacillin for S aureus

• Bronchiolitis: infants, RSV

• transmit by large droplet and by hand

• winter infection (Oct to Feb)

• Treat bronchiolitis with ribavirin (if severe)

Influenza

• Types: A H3N2, A H1N1, B, H5

• Spread by droplets/hands

• aching muscle, headache cough, fever, Complications: pneumonia

• Prevention: vaccines (inactivated/live) for not at risk people

• Treatment: neuraminidase inhibitors (oseltamivir, zanamivir) for at risk ppl

Compare influenza and common cold

• influenza

  • cause: influenza A, B, C

  • more severe, systemic

• common cold

  • cause: mainly rhinoviruses, coronavirus

  • typically mild

High-Risk Groups (Flu Complications)

• diabetes mellitus, Chronic illnesses, immunosuppression, pregnancy, elderly, BMI ≥ 40

Pneumonia

inflammation and accummulation of fluid and inflammatory cells in the alveoli, seen as consolidation on chest x ray (shadow in x ray)

Types

• Community-Acquired

• Hospital-Acquired

• Aspiration: due to inhaled gastric contents

Common Organisms

• H. influenzae, S. pneumoniae, M. pneumoniae, S. aureus, Legionella, TB

Symptoms & Investigations

• Cough, sputum, chest pain, fever

• CXR: consolidation

• Blood/sputum cultures (not saliva), urinary antigens (Legionella, pneumococcus)

Tuberculosis (TB)

• Mycobacterium tuberculosis (chronic granulomatous)

• Spread by respiratory droplets

• perisistent cough, blood in sputum, fever

• Forms granulomas → can rupture (miliary TB)

• Ziehl-Neelsen stain: acid-fast bacilli

• Slow growth (up to 6 weeks)

Treatment

• 6-month course: isoniazid, rifampicin, pyrazinamide, ethambutol

• MDR-TB: rapid resistance testing, isolation in negative-pressure rooms

BCG Vaccine

• For neonates at risk

Dental Consideration

• Defer treatment if symptomatic (perisistent cough, blood in sputum, fever) until declared non-infectious

• latent TB is not infectious

Diagnosis of Respiratory Tract Infections (RTIs)

Microbiology

• Throat swabs, sputum, BAL for culture & PCR

• Blood cultures (sepsis)

• Urine antigens (Legionella, pneumococcus)

• Serology (EBV, Coxiella, ASOT)

Other Testing

• CRP, WBC

• Imaging: CXR, CT