Polio, Diphtheria and whooping cough

Question 1

Vaccinations

Answer 1

• All three are preventable by vaccination : 6-in-1 vaccine including polio, whooping cough, diphtheria, tetanus, Haemophilus influenzae B (HiB) and hepatitis B.

Question 2

Diphtheria causes
Causative organism detection

Answer 2

Corynebacterium diphtheriae:Gram-positive bacillus, aerobic, non-spore forming, non-encapsulated bacterium.

Question 3

Four biovars of C.diphtheria

Answer 3

Biovar: variant prokaryotic strains
mitis - 77% of cases
intermedius
gravis
belfanti

77% of cases of diphtheria is caused by C. diphtheriae biovar mitis.

Question 4

C. diphtheriae

Answer 4

• Can cause respiratory and cutaneous forms of disease
  -Transmission often by droplets but can occur via cutaneous lesions/ contact with infected animals. unpasturised diary products

Question 5

C. diphtheriae Symptoms/ incubation/ basic pathology

Answer 5

Incubation period: 2-5 days
- Symptoms: Sore throat, fever
-Produces toxin causing cell necrosis triggering inflammatory response
Pathogenesis: Aggregates of dead epithelial cells, fibrin, bacteria, neutorphils cause pseudomembrane patches on tonsils that can spread to whole soft palate.
- Larynx can become blocked cuasing asphyxiation
- Most deaths caused by toxin spread via bloodstream causing mycarditis

Question 6

C. diphtheriae Diagnosis

Answer 6

Predominantly Culture based via normal blood agar/ tellurite containing agar: Hoyles agar: Partially selective and differential to toxicgenic C. diphtheriae stains. Contains Tellurite: inhibits range of gram negative and positive bacteria. Tellurite reduction produces distinctive grey-black colonies.

MALDI-ToF mass spec used for further identification. Reference lab confirmatory tests: qPCR (targets A-subunit of diptheria toxin), Elek immunoprecipitation. Handled at an ACDP (Advisory Committee on Dangerous Pathogens) cat 3 lab despite being a ACDP cat 2 organism (due to severity pf disease it causes and potential consequences of mishandling)

Question 7

C.diphtheriae diagnosis: Hoyle agar

Answer 7

-C. Diptheriae Stained (throat/wound/nasal swab/ respiratory secretions) using Alberts stain used for staining the solutin granules. when stained with blue dye they appear red ( metachromatic).

Hoyles agar: Partially selective and differential to toxicgenic C. diphtheriae stains. Contains Tellurite: inhibits range of gram negative and positive bacteria. Tellurite reduction produces distinctive grey-black colonies.

Question 8

C. diphtheriae Treatment

Answer 8

Treatment: Focus on removal of the toxin - diptheria anti-toxin. Organism treated using penicillin / erythromycin
Prevention: Diptheria toxoid vaccine is a formulin treated (denatured) toxin from C.diphtheriase alongside aluminium salt adjuvant to induce antitoxin immunity.

Question 9

Polio (Poliomyelitis)

Answer 9

• caused by poliovirus:

single-stranded positive-sense RNA virus. Transmission: occurs via the mouth Pathogenesis: replicated in the pharynx and GI tract. May spread via lymphoid tissues and bloodstream to central nervous system. Replication can spread amongst neurons can cause loss of motor neurons causing flaccid paralysis. Poliovirus shed (released via feces) from patients for several weeks ( spread).

Question 10

Post- polio syndrome

Answer 10

Can occur 15-40 years later
New or worse weakness, muscle pain, paralysis
- Not infectious
- Possibly due to failure of motor neurones generated during recovery from initial infection

Question 11

Polio diagnosis

Answer 11

Confirmed in specialised reference lab: Enterovirus PCR on stool (as virus is shed in faeces). CSF samples and throat or nasopharyngeal aspirates (NPA). Biochemistry/microscopy/viral culture of CSF samples. Viral culture of throat swabs. Tests can be on stool samples from household contacts.

Question 12

Polio treatment

Answer 12

No treatment: only symptoms are treatable: splits to relieve leg spasms and prevent deformity, physiotherapy and surgical correction of deformaities.
Vaccine preventable.

Question 13

Treatment of polio symptoms: Iron lung

Answer 13

Patient in large cylinder with airtight rubber collar around the neck with pump used to move air in and out of the cabinet to move the chest and force it to “breathe’.
-body of the patient, apart from the head, held in the cabinet with only mirrors to see around the room., patient can only talk when the cabinet forces breath out.
- small number of patients (~10) still dependent on the iron lungs today , still in them decades later with only short breaks.

Question 14

Whooping cough

Answer 14

Causative organism: Bordetella pertussis: small Gram-negative, aerobic, encapsulted non-motile bacilli.

Pathogenesis: Produces virulence factors infecting respiratory mucosa. 1-2 week incubation period: patient asymtpomatic but infectious. Illness can last for months.

Question 15

Whooping cough: B. pertussis virulence factors

Answer 15

filamentous hemagglutinin

pertussis toxin - impairs phagocyte function and interferes with B and T cell function making host more susceptible to secondary infections.

tracheal cytotoxin - stops cilia beating and induces IL-1 production and fever.

lethal toxin - causes local inflammation and tissue death.

lipopolysaccharide - resutls in fever in the host

Question 16

Whooping cough: Disease stages and main characteristics

Answer 16

Catarrhal stage: most infective stage, symptoms include sore throat, mild cough and malaise. Paroxysmal stage: rapid, violent and uncontrolled coughing fits followed by a inspiratory gasp (“whoop”). Convalescent stage: gradual improvement in cough frequency and severity

Question 17

Whooping cough diagnosis

Answer 17

NPA and/or nasopharyngeal swabs taken for patients with coughs less than 21 days and cultured on charcoal or blood agar. Colonies are small, bisected pearl type. Diagnosed via clinical presentation: “whoop” after coughing, cough induced vomiting and paroxysmal cough. Serological tests for toxin antigen on children older than 16 years with coughing for more than 14 days, or PCR which is more sensitive