Upper Respiratory Tract Infections

Definition of pathogenesis

The development of a disease 

Definition of pathogen

Any organism OR agent that produces a disease.

(eg bacteria or a toxin produced by bacteria)

Definition of pathogenicity

The ability of a pathogen to cause disease

Definition of virulence

Intensity of disease/ degree of harm caused.

eg  different strains of E.coli some are more harmful than others due to specific virulence factors

Definition of acute infection

Sudden/rapid onset , usually short-lived. Can be mild or severe    e.g. common cold, acute appendicitis

Definition of chronic infection

Develop slowly. Long lasting and/ or recurrent

e.g. chronic hepatitis, Tuberculosis

Definition of latent infection

Appears a long time after initial infection

e.g. Herpes → Shingles, Tuberculosis

Definition of Healthcare associated infection (HCAI or HAI)

Results from direct treatment in a healthcare setting or contact with a health care setting.

e.g. Clostridioides difficile- diarrhoea,

E. coli,- UTI -catheter

Staphylococcus  aureus (MRSA)- wound infections,

Klebsiella pneumonia- ventilator associated respiratory

Pseudomonas aeruginosa –opportunistic resistant

What % of hospital treated patients get a significant HAI?

10%

Definition of opportunistic

Caused by organisms that DON’T normally infect healthy hosts. e.g. Staphylococcus aureus, Candida albicans, C. diff

Definition of primary infection

Initial infection within a patient

e.g. surgical site infection, urinary tract infection

Definition of secondary infection

Infections that follow a primary infectione.g. infections of blood stream (septicaemia), bones & joints

Definition of localised infection

Infection that remains at one body site or organ.

Definition of systemic infection

Infection that has spread to multiple organs/ sites, or spread to the blood stream.

Definition of septicaemia

Life-threatening condition arising from pathogens  in the blood

Definition of sepsis

Host response to high level of infection in the blood-

Definition of septic shock

Sepsis accompanied by low blood pressure- High risk of death

Definition of bacteremia

Bacteria present in the blood - small number not problematic

There are common bacterial infections by body site.

• Respiratory tract

• Urinary tract

How are infections in the respiratory tract and urinary tract organised?

Respiratory tract:

• Upper respiratory tract (nose, throat, ear, conjunctiva)

• Lower respirator tract (trachea, lungs)

Urinary tract

• Lower/upper

• Ascending/descending

Name common upper respiratory tract infections

• Rhinitis

• Pharyngitis and tonsillitis

• Acute otitis media

• Conjunctivitis

What is rhinitis?

Inflammation of the nasal lining

What is pharyngitis and tonsilitis?

Inflammation of the pharynx and tonsils

What pathogen usually causes rhinitis, pharyngitis, and tonsillitis?

Viral: Most common source of infection

Bacterial: Group A Streptococcus (GAS)

What causes strep throat?

Streptococcus pyogenes

What is the common cold?

• Symptoms

• Cause

• Transmission

• Treatment

The common cold is a viral infection that includes rhinitis as a symptom

• Symptoms: Runny nose, sneezing, itching, blocked nose. Generally mild and self limiting. Peak is at day 2-3, resolves within 7-10 days

• Cause: Rhinovirus 30-50% of cases, coronaviruses, adenovirus, etc

• Transmission: Highly infectious. Aerosol and contaminated hands

• Treatment: Decongestants (NOT antibiotics)

Why isn’t there a vaccine for the common cold?

Rhinovirus has over 165 serotypes, with new ones each year

What causes, the symptoms associated with, method of transmission, and treatment for pharyngitis and tonsilitis?

• Cause: 70% of cases caused by viruses (rhinovirus, coronaviruses, influenza viruses, etc)

• Symptoms: Swollen, sore throat, difficult swallowing, inflamed tonsil, fever, headache

• Transmission: Saliva

• Treatment: Self limiting. Rest, lozenges, mild pain relievers (NO antibiotics)

What is the gram status of streptococcus?

Gram positive (stains purple)

What is GAS and GBS?

GAS = Group A Streptococcus

GBS = Group B Streptococcus

What’s the difference between GAS and GBS?

They are 2 different types of bacteria from the streptococcus family, which cause different health issues.

• GAS stands for Group A Streptococcus (Streptococcus pyogenes). It commonly affects the throat and skin.

• GBS stands for Group B Streptococcus (Streptococcus agalactiae). It commonly lives in the digestive and genital tracts

What’s IGAS?

Stands for Invasive Group A Streptococcus

• GAS usually causes mild throat and skin infections, but can also cause IGAS

• IGAS = TSS and necrotizing fasciitis

Most common cause of bacterial infections?

Bacterial: GAS (streptococcus pyogenes)

What is the microbiology of streptococcus pyogenes?

• Capsular bacteria

• Outside encased in hyaluronic acid helping to evade immune system / phagocytosis and colonise tissue at the back of the throat

What are the main symptoms of bacterial pharyngitis and tonsillitis (strep throat)?

• Inflamed tonsils

• Pus

• Difficult swallowing

• Fever

• Headache

How is strep throat transmitted and how is it treated?

Spread via respiratory droplets and direct contact

Treat via antibiotics

What causes scarlet fever?

Some strains of Streptococcus pyogenes secrete a toxin (pyrogenic exotoxin). This toxin causes an immune response, causing a characteristic rash

What are the main symptoms of scarlet fever, how is it transmitted, and how is it treated?

Symptoms: Strep throat symptoms + a body rash, strawberry tongue

Transmission: Respiratory droplets, close contact, shared items

Treatment: Antibiotics

What bacterium causes Group A Streptococcus (GAS) infection?

Streptococcus pyogenes

What is iGAS?

A GAS infection that breaches barriers and becomes systemic

Name 2 examples of iGAS diseases

TSS

Necrotising fasciitis

What autoimmune complication can follow a GAS infection?

Rheumatic fever

What is rheumatic fever?

An autoimmune complication that attacks the body’s own tissues, including heart valves

What kidney complication can follow streptococcus infection?

Glomerulonephritis?

What is acute otitis media?

Ear ache

Infection of the middle ear

Inflammation and swelling (there’s a build up of fluid behind the eardrum)

50% of acute otitis media cases are viral. Cases caused by bacteria, what strains of bacteria cause them?

• Streptococcus pneumoniae

• Haemophilus influenzae

What are the symptoms of acute otitis media?

• Pain in ear

• Hearing loss

• Dizziness

• Fever

• Vomiting

• Diarrhoea

• Perforation of ear drum

• Children tug their ear

What is chronic otitis media?

Repeated infections or inflammation of the middle ear

What can chronic otitis media cause?

Can cause tissues surrounding the eustachian tube to swell up, blocking it

The air in the middle ear is absorbed into the surrounding tissues

A vacuum forms in the middle ear

Fluid accumulates

Leads to glue ear

How do you treat glue ear?

Children may get grommets fitted to help equalise the pressure

What is conjunctiva?

Loose connective tissue that covers the surface of the eyeball

What causes conjunctivitis?

1. Viral (most common)

2. Bacterial (e.g. staphylococcus sp, streptococcus sp, haemophilus sp)

3. Allergic

4. Reactive

5. STI associated

What are the symptoms of conjunctivitis?

• Redness in the white of the eye

• Increased tears

• Thick yellow discharge that crusts over the eyelashes

• Green/white discharge from eye

• Burning eyes

• Blurred vision

What’s the treatment for bacterial infections of the conjunctiva?

Topical chloramphenicol

Which bacterium can cause severe conjunctivitis in newborns?

Neisseria gonorrhoeae

What serious complication can gonococcal conjunctivitis cause?

Corneal perforation, potentially causing vision loss

Which bacterium causes inclusion conjunctivitis in adults?

Chlamydia trachomatis

What condition is specifically associated with repeated Chlamydia trachomatis eye?

Trachoma

What happens to the eye in trachoma?

Roughening of the inner eyelid surface, causing eye damage

How is trachoma spread?

Contact, touch, flies

What can untreated trachoma lead to?

Blindness

How is a chlamydia eye infection treated?

Oral and topical antibiotics

Can chlamydia eye infection cause permanent eye damage?

Yes, even after treatment. This is because repeated infection causes trachoma, which roughens the inner surface of the eye lid, damaging the eye. You can’t unroughen the inner eyelid.