Microbiology Flashcards
What is colonisation?
The presence of a microbe in the human body without an inflammatory response.
What is infection?
Inflammation due to a microbe
What is bacteraemia?
The presence of viable bacteria in the blood.
What is sepsis?
The systemic inflammatory response to infection.
What bug types do phagocytes target?
Bacteria
Fungi
What bug types do T lymphocytes target?
Viruses
Fungi
Protozoa
What bug types do antibodies and B lymphocytes target?
Bacteria
Viruses
What bug types do eosinophils target?
Worms
Protozoa
Fungi
What bug types do mast cells target?
Worms
What bug types do complement target?
Bacteria
What tests can be done to diagnose infection?
Laboratory features
- microbiology
- WCC
- CRP
- platelets, clotting
Microbiology: Blood, stool, urine, wound, tissue cultures
Microscopy: stool, urine, CSF, sputum
Serology
Antigen detection
PCR
What are the most common sources of bacteraemia in the community and where do they originate from?
- E.coli (urine, abdomen)
- S.pneumoniae (respiratory)
- S.aureus (usually MSSA- skin)
What are the most common sources of bacteraemia in hospital and where do they originate from?
- E.coli ( catheter related or abdomen)
- S.aureus (usually MRSA- line or wound related)
- CNS (line/prosthesis related)
- Enterococci (urine, wound, line)
- Klebsiella (urine, wound)
- Pseudomonas spp,.
What symptoms are common with antibiotics?
Nausea, vomiting, diarrhoea
- All antibiotics disrupt the gut bacterial flora
- May affect absorption of oral contraceptives
What can gentamicin cause?
Renal and VIII (vestibulocochlear nerve) damage.
What can ciprofloxacin cause?
Tendonitis, (especially if alongside corticosteroid) avoid use in pregnant or breast feeding women.
What must patient avoid when taking metronidazole?
Avoid alcohol since metronidazole interacts with alcohol.
What is a URTI?
Inflammation of the upper respiratory tract (above the larynx).
Can be viral or bacterial.
Not always confined to a single structure.
What is sinusitis?
Inflammation of paranasal sinuses
What is rhinitis?
Inflammation of nose
What is pharyngitis?
Inflammation of pharynx, tonsils, uvula
What is epiglottitis?
Inflammation of epiglottis and superior larynx
What is laryngitis?
Inflammation of larynx
Most causative organisms of community acquired pneumonia?
Streptococcus pneumoniae (70%)
Atypical/viruses (20%)
Haemophilus influenzae (5%)
Staphylococcus aureus (4%)
Other bacteria (1%)
What are the risk factors for community acquired pneumonia?
Increasing age
Immunocompromised patients
Smoking
What are the clinical features of an acute COPD exacerbation?
Productive cough or acute chest illness
Breathlessness
Wheezing
Increased sputum purulence
Often follows a viral infection or fall in temperature and increase in humidity (i.e. Winter).
What is the difference between chronic bronchitis and emphysema?
Chronic bronchitis = reversible
Emphysema = irreversible
Chronic bronchitis is inflammation and excess mucus build up in the bronchioles.
Emphysema is when the alveolar membranes break down resulting in impaired gas diffusion.
What is “sore throat”?
Describes the symptom of pain at the back of the mouth.
Clinical features of sore throat?
Sore throat (symptom): Pain at the back of the mouth
Acute pharyngitis: inflammation of the part of the throat behind the soft palate (oropharynx)
Tonsillitis: inflammation of the tonsils
Aetiology of sore throat in primary care?
Caused by a viral or bacterial infection
- Non-infectious causes are uncommon
Common causes of sore throat in primary care are usually not life-threatening and include common cold, influenza, streptococcal infection.
Common complications of acute sore throat?
Otitis media (most common)
Peritonsillar abscess (quinsy)
Parapharyngeal abscess
Lemierre Syndrome (Suppurative thrombophlebitis of jugular vein)
When should patient with acute sore throat be immediately referred to secondary care?
REFER immediately: Stridor, breathing difficulty, clinical dehydration, systemically unwell
What is acute otitis media?
An upper respiratory infection involving the middle ear by extension of infection up the Eustachian tube
Predominantly disease of infants and children due to shorter Eustachian tube.
Presents with earache
What is the cause of acute otitis media?
Often viral with bacterial secondary infection
Most common bacteria: Haemophilus influenzae, Streptococcus pneumoniae and Streptococcus pyogenes.
How is acute otitis media diagnosed?
Swab of pus if eardrum perforates – otherwise samples can’t be obtained
How is acute otitis media treated?
80% resolve in 4 days without antibiotics.
First line – amoxicillin
Second line – erythromycin
What is acute sinusitis?
An inflammation of the sinuses
Treatment for acute sinusitis?
Similar organisms as in otitis media
Treatment
Av. length illness 2.5 weeks.
antibiotics for severe/deteriorating cases of >10 days duration.
1ST LINE phenoxymethylpenicillin
2ND LINE doxycycline – NOT IN CHILDREN!!!
Typical organisms in bacterial conjunctivitis?
Staph aureus
Strep pneumoniae
Haemophilus influenzae (especially in children)
Is chloramphenicol useful in bacterial conjunctivitis?
Yes
Chloramphenicol is effective against strep, staph, haemophilus but not pseudomonas.
When is chloramphenicol avoided in bacterial conjunctivitis?
Avoid chloramphenicol if history of aplastic anaemia or allergy
Be aware of chloramphenicol allergy if worsening symptoms
Grey baby is if too high dose of chloramphenicol is used, neonate cannot process the drug as liver is immature and can cause hypotension
Main organisms leading to viral conjunctivitis?
Adenovirus
Herpes simplex
Herpes zoster
What is orbital cellulitis?
A serious infection that involves the muscle and fat located within the orbit.
It is also sometimes referred to as postseptal cellulitis.
Orbital cellulitis vs preseptal cellulitis?
With preseptal cellulitis there is swelling, redness, and tenderness of the eyelids and surrounding area.
The eye itself is not affected.
Whereas in orbital cellulitis there are the features of preseptal cellulitis along with eye pain, decreased eye movement, vision changes and proptosis (abnormal eye protrusion).
Features of orbital cellulitis?
Painful – especially on eye movements
Proptosis
Often associated with paranasal sinusitis
Pyrexial
Sight threatening
Cared for by ENT and Ophthalmology
CT scan to identify orbital abscesses
Three main bacterial STI’s and their causative organisms?
Chlamydia trachomatis (chlamydia)
- Can lead to lymphogranuloma venereum. Painful lymph nodes around site.
Neisseria gonorrhoeae (gonorrhoea)
- Gram -ve diplococci
Treponema pallidum (syphilis)
- Spirochete bacteria
Three main viral STI’s and their causative organisms?
Human papilloma virus (genital warts) - specifically HPV types 6 and 11.
Herpes simplex (genital herpes)
Hepatitis and HIV
Three main parasitic STI’s?
Trichomonas vaginalis
Phthirus pubis (pubic lice or “crabs”)
Scabies
What is the typical presentation for a genital candida infection in female?
Intensely itchy vaginal white discharge.
How is genital candida infection diagnosed?
CLINICAL DIAGNOSIS - based on signs and symptoms.
High vaginal swab for culture – the majority of cases are caused by C. albicans
Treatment for genital candida infection?
Topical clotrimazole pessary
or cream, (available OTC/over the counter)
Oral fluconazole
Features of acute bacterial prostatitis?
Symptoms of UTI, but may have lower abdominal pain/back/perineal/penile pain and tender prostate on examination
What causes acute bacterial prostatitis?
Same organisms as UTI (E. coli & other coliforms, Enterococcus sp., but check for STI in patients <35years (gonorrhoea, chlamydia)
Diagnosis of acute bacterial prostatitis?
Clinical signs + MSSU for C&S (+/- first pass urine for chlamydia/gonorrhoea tests)
Treatment of acute bacterial prostatitis?
Ciprofloxacin for 28 days (altered depending on culture result).
Trimethoprim (28d) if high C. diff risk
How do the normal vaginal bacteria help defend against pathogens?
The normal vaginal flora contains hydrogen peroxide–producing lactobacilli such asLactobacillus
crispatusandLactobacillus jensenii
These probably help “defend” the vagina against a number of pathogens (an example of innate immunity).
What is the normal vaginal pH?
Normal vaginal pH is 4 to 4.5 (elevated in BV- Bacterial Vaginosis)
Features of pubic lice (phthirus pubis)?
Acquired by close genital skin contact
Lice bite skin and feed on blood, which causes itching in pubic area
Female louse lays eggs on hair next to skin
Males on average live for 22 days, female for 17 days
Treatment of pubic lice (phthirus pubis)?
Malathion lotion
