Microbiology Flashcards
What is required for diagnosis of a sore throat?
A well taken throat swab
2/3rds of sore throats are bacterial and need ABx - true/false
False - 2/3rd are viral and DO NOT need ABx
What is the most common bacteria to infect the throat?
streptococcus pyogenes (group A streps)
Clinically streptococcal throat will present as ______
Acute follicular tonsillitis
Strep throat should be treated with _____ but NOT ______
Penicillin but not amoxicillin
What ABx can be used if there is an allergy?
Clarithromycin
Strep pyogenes is a gram positive/negative coccus which forms chains/clusters and undergoes what type of haemolysis?
Gram positive
Chains
B (complete) haemolysis
name three acute complications of strep throat
Quinsy
Sinusitis/otitis media
Scarlet fever
What causes scarlet fever?
Strains of group A strep which produce a erythrogenic toxin
What is a Quinsy?
An abscess near the tonsils and below the palate
Which infection control procedures are used in a Quinsy?
Standard protection + Gloves and apron and consider if droplet precaution is necessary
Name the two most common later complications of streptococcal throat
Rheumatic fever - fever/arthritis/pancarditis (3weeks post infection)
Glomerulonephritis (1-3weeks post infection) giving haematuria.
What is thought to cause the two later complications of streptococcal throat?
Cross reacting antibodies damaging the heart tissues and the glomerulus
name the infecting organism in diphtheria.
Cornybacterium diphtheriae
State the clinical presentation of diphtheria
Severe sore throat
Grey white membrane across the pharynx
What does cornybacterium diphtheriae produce?
A cardiotoxic and neurotoxic endotoxin.
What is the grey white membrane across the pharynx? Why is it clinically important?
it is a pseudomembrane
Pseudomembrane if not diagnosed rapidly can grow across and block the airway and cause suffocation.
Diphtheria is not common in the UK - Why? Where is it common?
Vaccination programmes
Russia for example
How is diphtheria vaccine produced?
it is a cell free, purified toxin from a strain of C. diphtheriae
Treatment for diphtheria is amoxicillin and supportive treatment - true/false
False - antitoxin and supportive treatment along with penicillin or erythromycin if pen allergic
What organism causes oral thrush?
Candida albicans
Describe the clinical appearance of oral thrush
White patches on red raw mucous membranes in the throat and mouth.
What is the treatment for candida infection?
Nystatin suspension delivered topically
Acute otitis media is a middle ear infection which occurs from entry of a pathogen through the ________
eustachian tube
AOM is more common in infants and adults than in young children - true/false
False it is most common in infants and children and not very common in adults
how will AOM usually present?
It will present with ear ache
What is required for diagnosis of AOM?
Swab of pus if eardrum perforates; completely clinical if it doesn’t
What percentage of AOM will resolve without treatment and over what period of time?
80% over 4 days
Acute sinusitis is most commonly seen in patients with ______
URTI
Severe pain, tenderness over the maxillary or frontal sinuses and horrible, purulent nasal discharge is indicative of what?
Secondary bacterial infection of acute sinusitis
often no samples can be taken in acute sinusitis - true/false
True
Abx should be avoided in acute sinusitis as 80% will resolve themselves in 14days - true/false
True
When indicated, what ABx should be used for acute sinusitis?
Penicillin V first line
Doxycycline - second line in adults but NEVER in kids
What are the three most common bacterial causes of otitis externa?
- Staph aureus
- proteus spp.
- pseudomonas aeruginosa
Fungal causes of otitis external include:
- aspergillus niger
- candida albicans
management of otitis externa includes:
- Topical aural toilet
- swabbing if that doesn’t fix it
- treat based on swab results e.g. clotrimazole for fungal cause or antibiotic suitable for bacteria isolated
What age group does infectious mononucleosis affect?
Young adults mostly
How does mono present?
Fever, enlarged nodes, sore throat, pharyngitis, tonsillitis, malaise and lethargy
What is the classic triad of mono and what percentage of cases are all three present in?
- fever
- Pharyngitis
- lymphadenopathy
- 70% of cases
What other signs and symptoms can be present in mono? What is the incidence of a few of them?
- jaundice; 5%
- Rash; 5%
- hepato-splenomegaly; unknown
- palatal petechiae
No patient with suspected mononucleosis should be prescribed which ABx and why?
- NEVER amoxicillin or ampicillin
- will always give a rash in 100% of patients; often mistaken for pen. allergy
What may haematology show for patients with mononucleosis?
leucocytosis and abnormal lymphocytes on blood film
Infectious mononucleosis is caused by bacteria - true/false
False - Epstein Barr Virus
Infectious mononucleosis is protracted and self-limiting - true/false
True
Name the complications of infectious mononucleosis
- Anaemia
- thrombocytopenia
- splenic rupture
- upper airway obstruction
- increased lifetime risk of lymphoma
EBV is a member of which family?
Herpes
EBV forms a persistent infection in which cells, especially in which part of the URT?
Epithelial cells especially in the pharynx
What are the two phases of primary infection with EBV?
Primary infection before 10 - rarely causes mono
Primary infection after 10 - often causes mono
What is treatment for mono?
Supportive - bed rest and paracetamol
Avoid sport for at least one month but if they insist on returning within one month, abdo ultrasound to look for splenomegaly.
Antivirals are NOT clinically effective. Corticosteroids may be effective in complex cases
What testing should be done for infectious mononucleosis?
EBV IgM and heterophile antibody testing
Blood count and film
LFTs
What are other causes of similar illnesses?
- cytomegalovirus
- toxoplasmosis
- primary HIV infection causing seroconversion illness.
When is type I HSV normally acquired and what does it normally cause?
it is normally acquired in childhood and causes oral ulcerations.
What percentage of adults in the UK have been infective with primary HSV type I?
70%
How is HSV type I passed on?
Saliva contact
What causes primary gingivostomatitis?
Primary HSV1 infection
In pre-school children.
How does primary gingivostomatitis present?
Systemic upset
1-2 mm vesicular lesions on the lips, buccal mucosa and hard palate, ulceration. Fever and lymphadenopathy. Can last 3 weeks
How is primary gingivostomatitis treated?
Aciclovir
HSV 1 becomes inactive but never really goes away - it remains in the sensory nerve cells and can reactivate to reinfect mucosal surfaces - true/false
True
What is the cause of a cold sore?
Reactivation of HSV1 from the nerves causes active infection including suppression.
Are all HSV1 reactivations symptomatic?
No
Does acyclovir prevent HSV1 latency?
No
How is HSV infection confirmed in the lab?
- swab of lesion in viral transport medium
- DNA detected by PCR
How many people will get herpes simplex encephalitis per annum?
1/1million
What does herpes simplex encephalitis cause?
Temporal lobe necrosis
How does herpes simplex encephalitis present? What are the mortality rates for herpes simplex encephalitis?
Fever, malaise and possibly new onset gran mal seizures. Very wide mortality range - 10-90%.
What group of viruses does enterovirus belong to?
Coxsackie viruses
What is the cause of herpangina?
You would think its HSV but its actually coxsackie viruses like enterovirus.
What patient’s is herpangina likely to affect?
preschool children
What are the symptoms of herpangina?
vesicles/ulcers on the hard palate
How is herpangina diagnosed?
Clinical diagnosis or PCR of swab in viral transport medium.
What causes hand foot and mouth disease?
Coxsackie viruses.
Family outbreaks of hand, foot and mouth are common - true/false
True
how is hand foot and mouth diagnoses?
Clinical diagnosis or PCR of swab in viral transport medium.
