Upper Respiratory Tract Infections

Upper respiratory tract (URT)

Nasal cavity, Pharynx, Epiglottis, Larynx

Lower respiratory tract (LRT)

Trachea, Bronchi, Bronchioles

what area of respiratory tract has highest density of microbes

Oropharynx

Respiratory tract infections

continuum for infectiour agents, prefeered location for infections, infection start in URT and spread to LRT, Rhinovirus perferes temp of URT (rarely goes to LRT)

Respiratory tract infections restricted to surface

Common cold, Streptococci, Influenza, Chlamydia trachomatis (conjunctivitis), Diphtheria, Candida albicans (thrush), Pertussis, Gonoherra?

Respiratory tract infection types

Resticted to surface (localized) or Spread through body (systemic)

Respiratory tract infections that spread through body

Measles, mumps, rubella, EBV, CMV, Chlamydia psittaci (psittacosis), Cryptococcosis, Q-fever

how respiratory tract infection spread through body

Starts at upper respiratory tract (URT), travels through lymphatic system, replication occurs in MALT, travel back to URT to spread, impact other organs (livers/ Kidney/ pancreas)

Professional invaders requirement - respiratory invader type

Adhesion to mucosa, ability to interfere with cilia, resist destruction in alveolar macrophages, damage local tissue

Secondary invader requirement - respiratory invader type

damaged respiratory virus, local defences impaired, chronic bronchitis/ foreign body/ tumou, depressed immune response, depressed resistance

Respiratory invader types

Professional - infect health respiratory tract, Secondary - infect when defences impaired

Mycobacterium leprae

cause leprosy, localized but can spread (systemic) if immunocompromised

Walking pneumonia causes

Mycoplasma pneumoniae + Legionella

SARS-CoV-2

Systemic infection, initially infects the respiratory tract, cause severe systemic inflammation, multi-organ dysfunction, vascular damage

Rhinitis

Common cold, >50% rhinovirus and coronavirus, rhinorrhea (runny nose) - induce flow of virus rich fluid, transmitted through aerosol/contaminated hands, self limiting - stays mostly in URT bc likes temperature, No vaccine bc antigenically diverse group (>200 types/subtypes)

Pharyngitis and Tonsilitis

70% caused by viruses (adV/ CMV/ EBV), 30% bacterial (S. pyogenes)

Cytomegalovirus Infection (CMV)

largest human herpes virus, multinucleated cell formation/ intranuclear inclusions, Host - Humans, Transmission through fluids (saliva/urine/blood/semen/cervical secretions), localizes in epithelial cells(salivary glands/kidney/cervix/testes) for persisent infection (shedding), no vaccines

CMV infection steps

initial infection asymptomatic → local lymphoid tissue → lymph nodes and spleen (circulating lymphocytes and monocytes) → localized in epithelial cells

clearing CMV infection

specific Ab and CMI response activates but doesn’t entirely clear, infection controlled by CMI mechanisms, infected cell can be reactivated if CMI impaired

CMV IR evasion

poor target for Tc cells, interferes with transport of MHC-1 molecules to cell surface (like adV), Induces expression of Fc receptors on cell surface

CMV symptoms

Spectrum, adult - fever type (fever/ lethargy/ abnormal lymphocytes/ mononucleosis), primary infection during pregnancy spreads through placenta - intellectual developmental disorder in babies

Epstein-Barr Virus (EBV)

DNA, Human host, transmitted via saliva (kissing disease), bimodal distrubtion in developing countries (1-6yrs + 14-20yrs), 95% of canadian adult have

EBV mechansim/clinical features

immunologically mediated, replicate in epithelial and B-lymphocytes (attaches C3d receptor=CD21), shed in saliva, spread to B lymphocytes in local lymphoid tissues, T lymphocytes attack infected B cells

EBV symptoms

naturally infected infants/yound child - no clinical disease, Young adults have mononuclosis/glandular fever (4-7 weeks after), fever, sore throat, petechiae on hard palate, lymphadenopathy, splenomegaly, Hepatitis, Caused by Cytokine release, infected B cell produce autoantibodies, no antivirals

Cancer associated with EBV

Burkitt’s lymphoma (Africa/Papua New Guinea) - Malaria weakens T cell control, Nasopharyngeal carcinoma (China/ SE Asia) - EBV DNA in tumors/ ingested nitrosamines (preserved fish)

Bacteria causing pharyngitis/tonsillitis

Streptococcus pyogenes, Group C + G beta hemolytic strptococci, Corynebacterium haemolyticum (+rash), Mycoplasma pneumoniae (+penemonia/bronchitis), Corynbacterium ulcerans, Neisseria gonorrhoea (+ disseminated disease)

Bacterial Pharyngitis symptoms

Sore red throat, difficulty swallowing, sudden fever -scarlet or rheumatic dependingvirulence genes, malaise, loss of appetite, Rheumatic heart disease (M protein), Acute Glomerunephritis

Scarlet fever

sandpapery rash (start Neck and Chest), red strawberry tongue, headache, chills, muscle ache

Rheumatic fever

Fever, joint pain (knee/ ankles/ elbow/ wrists), joint swelling, possible cardiac problems (chest pain/ shortness of breath)

Acute Glomerunephritis

Impact Kidney, Anti-Strep ab → cirulating immune complex, activation complement and coagulation system, inflammation and blood in urine, type 3 hypersensitivity?

Parotitis

Inflamattion of parotid glands (largest salivary), caused by mumps

Mumps

transmitted Airborne droplets and close contacts, recovery in 1 week if child, lifelong immunity, vaccine - live attenuated (MMRV), systemic - use lymphoid system to spread, complication if young adults - Meningitis/ Encephalitis/ Pancreatitis/ Hearing loss/ Sterile if male

Otitis Media

infection of middle ear, 50% viral (adV/RSV) and 50% bacterial (S. pneumoniae/ H. influenzae/ S. pyogenes/ M. catarrhalis/ S. aureus), in pre school age bc more likely to spread contaminated fingers into ear, impact cleansing function of ciliated epithrlium, cause damage to tympanic membrane

Otitis Media symptoms

early signs nonlocalized, Fever, irritability, ear pain, changes in hearing, purulent discharge

Otitis Externa

Outer ear, Pathogen distinct from media, bacterial flora (Staphylococcus aureaus/ Candida albicans/ Pseudomonas aeruginosa - opportunistic), Antibiotic ear drops → penicillin (or Azoles for Candida bc microeuk)

Acute Sinusitis

Mucus lined cavities, start viral butcause secondary, aetiology similar otitis media, facial pain and local tenderness, prolonged respiratory tract infection, purulent nasal discharge, fever (50% of patients), Maxillary - Headache and ‘upper teeth’ pain, complications - orbital cellulitis/ osteomyelitis/ meningitis/ brain abscess

Epiglottitis

Edema and inflammation, blocks airways, caused by H. influenzae, vaccine against reduce 80-90% or antibiotic treatment

Oral candidiasis

changes in oral flora, Antibiotic treatment unbalances normal, Candida albicans

Candida albicans

microeukaryote, cause thrush, kept at low copy numbers by other bacteria

Caries

Streptococcus mutants, biofilm that produces acid - dissolves tooth enamel, more common in caucasians bc high sugar diet

Periodontal disease

Actinomyces viscosus/ Actinobacillus/ Bacteroides spp., in gingival crevice, gingivitis, gums recede over time (w/ age), impact gums and teeth, diet and oral hygiene play significant role