Microbiology session Flashcards
What is the most common route of infection for meningitis and what is an example of this?
The ears e.g. otitis media
What is meningitis?
An infection of the meninges (the protective layers that surround the brain).
Usually inflammation in the context of infection.
Apart from the ears, what are other routes of infection for meningitis?
Nasopharynx
Parameningeal e.g. sinusitis
Haematogenous e.g. infective endocarditis
What is acute pyogenic meningitis?
Pyogenic means it forms pus so bacterial meningitis
What is aseptic meningitis?
Aseptic meningitis is the umbrella term for meningitis that comes back negative on culture.
Usually includes: viral and non-infectious meningitis.
What are the main triad of symptoms for meningitis?
Fever
Neck stiffness
Headache
What other symptoms can be associated with meningitis?
Photophobia
Vomiting
Altered consciousness
Sudden onset
What are the 2 signs that may be seen in meningitis?
Kernig’s sign
Brudzinski’s sign
What is Kernig’s sign?
Knee is flexed to 90 degrees
Hip is flexed to 90 degrees
Extension of the knee is painful or limited in extension
What is Brudzinski’s sign?
When lying down, passive flexion of the neck elicits flexion of the hips and knees.
What are features of meningococcal speticaemia?
Non-blanching, petechial rash
Purpuric
What is the pathology of pyogenic meninigitis?
The pia-arachnoid layer is congested with a thick layer of suppurative exudate (pus) that covers the leptomeninges (inner 2 meninges)
What is the organism for bacterial (pyogenic) meningitis in neonates?
Listeria monocytogenes
Group B strep
What is the organism for bacterial (pyogenic) meningitis in unvaccinated kids?
H.influenzae
What is the organism for bacterial (pyogenic) meningitis in ages 10-21?
Neisseria meningitidis
What is the organism for bacterial (pyogenic) meningitis in ages 21-64?
Strep. pneumoniae
What is the organism for bacterial (pyogenic) meningitis in ages 65+?
Strep. pneumoniae
What is the organism for bacterial (pyogenic) meningitis in immunocomprimised?
Listeria.monocytogenes
What is the organism for bacterial (pyogenic) meningitis with head trauma?
Staph.aureus
What is the organism for bacterial (pyogenic) meningitis with cribriform plate fracture?
Strep.pneumoniae
What complications can occur from bacterial meningitis?
Sensorineural hearing loss
Limb loss
Blindness
Cerebral palsy
What is the most common type of aseptic meningitis?
Viral meningitis
What are risk factors for viral meningitis?
Late summer/autumn
Travel
What are the viruses that can cause viral meningitis?
enterovirus
coxsackie
mumps
HSV
VZV
How is viral meningitis diagnosed?
stool PCR + culture
throat swab
LP PCR
HIV
What is typical treatment for viral meningitis?
Supportive treatment (the cause is usually enterovirus which includes ECHO virus which is self-limiting hence the reason why it is supportive treatment).
What are the risk factors for fungal meningitis?
Immunocompromised, HIV
What is the underlying causative organism for fungal meningitis?
Cryptococcus neoformans (an encapsulated yeast)
What are non-infectious causes of meningitis?
Behcet’s syndrome
Contrast
Carcinoma
Sarcoidosis
Vasculitis
Dural venous sinus thrombosis
Migraine
Drugs eg NSAID, sulfas, IVIg, co-trim
What is the characteristic CSF feature that would point to fungal meningitis?
Indian ink stain
Treatment for fungal meningitis?
IV amphotericin B or flucytosine
Can a lumbar puncture be bacteria -ve if the patient has already been given antibiotics?
Yes
When is a lumbar puncture contraindicated?
Lumbar puncture contraindicated if patient has raised ICP (intracranial pressure).
This is because it could cause shunting
When should a CT be carried out instead of a lumbar puncture for interpreting meningitis?
Papilloedema
GCS <13
Hx of CNS disease
Seizure /focal neuro deficit
Stroke
Immunocompromised
Treatment for bacterial meningitis?
Antibiotic + steroid
(particularly: ceftriaxone and dexamethasone)
Which steroid is usually given in bacterial meningitis?
Dexamethasone
When is dexamethasone started after administering antibiotics?
Immediately or 15 mins after starting antibiotics.
Why is dexamethasone given for bacterial meningitis?
Reduce cerebral oedema
What are contraindications to dexamethasone in bacterial meningitis?
Immunocompromised
Septic shock
Meningococcal (N. meningitidis)
Listeria
Antibiotics used for bacterial meningitis?
1st IV ceftriaxone
Pen allergy: IV chloramphenicol + vanc
Listeria: IV amoxicillin
Travel: IV vancomycin
Treatment for viral meningitis?
Usually supportive
Treatment for fungal meningitis?
IV amphotericin B or flucytosine
What is encephalitis?
An infection of the brain parenchyma
What is the aetiology (cause) of encephalitis?
VZV (varicella zoster virus)
HSV - in older patients
What is the typical onset for encephalitis?
Insidious onset (10 days)
What are the symptoms of encephalitis?
Psychosis & confusion
Seizures
Fever
Neck stiffness
Photophobia
Headache
Partial paralysis
Speech disturbance
What are the main investigations for encephalitis?
LP PCR, EEG, MRI
What is the typical MRI appearance for encephalitis?
Bright white (hyperdense), Bilateral temporal lobe involvement.
Treatment for encephalitis?
IV aciclovir
What is Guillian Barre syndrome?
Post infection (up to 4 weeks), acute autoimmune demyelinating neuropathy.
What is the aetiology of Guillian Barré syndrome?
Previous food poisoning
Campylobacter
CMV
EBV
Underlying pathology of Guillian Barre syndrome?
B cells secrete antibodies that attack pathogens, however the antigen on pathogens matches those on the myelin sheath
What are the signs of Guillian Barre syndrome?
Progressive paralysis
Ascending weakness
Pain
Investigations for Guillian Barre syndrome?
nerve conduction studies, LP, FEV1/FVC ratio (spirometry)
Complications of Guillian Barre syndrome?
Respiratory failure
Cardiac arrhythmia
What is treatment for Guillian Barre syndrome?
Ig infusion
Plasma exchange
What is Botulism?
A rare but serious illness caused by a toxin that attacks the body’s nerves.
Who does botulism typically affect?
PWID (people who inject drugs)
What is the pathogen responsible for botulism?
Clostridium botulinum
What are the typical sources for botulism?
Soil
Food
Contaminated wounds
What is the underlying pathology of botulism?
Exotoxin acts on motor neuron terminals to block vesicle docking in presynaptic membrane, irreversibly inhibiting Ach release.
What are the signs of botulism?
Rapid onset weakness w/out sensory loss
Ascending paralysis
What are the leptomeninges?
Arachnoid and pia mater
What age group is mostly affected by chlamydia?
20-24 years old
Female more common than male
What is the pathogen for chlamydia?
Chlamydia trachomatis
Gram -ve intracellular anaerobe, doesn’t stain
What is the incubation period for chlamydia trachomatis?
7-21 days
Chlamydia is usually asymptomatic however what are some of the symptoms that it can still present with?
Vaginal: milky discharge, dyspareunia, dysuria
Penile: dysuria, cloudy discharge, testicular pain
Ano-rectal: procto-colitis + itch, discharge, bleeding
LGV: ulcers, gross unilateral lymphadenopathy
How is chlamydia diagnosed?
NAAT
Vaginal: endocervical swab before speculum intro
Penile: first void urine or urethral swab
± anal or oral swabs depending on exposure
Complications of chlamydia?
PID (pelvic inflammatory disease)
Reactive arthritis
Fitz Hugh Curtis
Antibiotics used for chlamydia treatment?
1st doxycycline 7d
2nd/preg: azithromycin
LGV doxycycline 3w
Treatment advice for chlamydia patient?
Partner notification
Abstain from sex for 7d
If pregnant, test for cure
What age group is mainly affected by gonorrhoea?
15-49 y/o, M > F
What is the pathogen for gonorrhoea and what type of bacteria is it?
gm -ve diplococci
Neisseria gonnorrhoeae
Average incubation for gonorrhoea?
2-5 days
Gonorrhoea is often symptomatic, what symptoms can it present with?
Vaginal: cervicitis, spotting, dysuria, discharge
Penile: yellow-green discharge, epididymo-orchitis, dysuria
Ano-rectal: tenesmus (recurrent inclination to clear the bowels), discharge, bleeding, proctitis
What tests can be used for gonorrhoea?
NAAT
PCR w/ chocolate agar
Vaginal: endocervical swab before speculum intro
Penile: first void urine or urethral swab
± anal or oral swabs depending on exposure
What are the complications of gonorrhoea?
PID (pelvic inflammatory disease)
Bartholin’s abscess
Endometritis (endometrial inflammation)
Epididymo-orchitis
What are the antibiotic treatments for gonorrhoea?
1st single dose ceftriaxone IM
Allergy: cefixime + azithromycin
Sensitive: ciprofloxacin
What treatment advice is given to patients with gonorrhoea?
Partner notification
Abstain from sex for 7d
Test for cure after 2-3 w
What age group and people are usually affected by syphilis?
20-29 y/o, MSM (men sex with men)
What is the causative pathogen of syphilis?
treponema pallidum which is a gm -ve spirochete
What is the average incubation period for syphilis?
10-90 days (21 on average)
Typical symptoms for stage 1 syphilis?
Single, painless primary chancre ± lymphadenopathy
Typical symptoms of stage 2 syphilis?
condyloma lata, fever, pharyngitis, lymphadenopathy
Condyloma lata = raised growth on the skin resembling a wart, typically in genital region. Transmissible by contact.
Typical symptoms of stage 3 syphilis?
Granulomas, behaviour change, sight/hearing loss
What tests can be used to diagnose syphilis?
- Treponemal IgG and IgM
- Confirmatory test
- Treponema pallidum assay
Dark field microscopy - microscopy with dark field background.
Treatment for syphilis?
One off benzylpenicillin double gluteal injection
Once every 3 weeks if tertiary syph
What is the underlying pathology of bacterial vaginosis (BV)?
Occurs due to a High Ph and reduced number of lactobacilli (natural bacteria)
Causative bacteria for BV?
Anaerobic bacteria:
- Gardenerella vaginalis
- Mycoplasma
Symptoms of BV?
Fishy odour
Thin White/grey discharge
Itching/ irritation and pain
How is BV diagnosed?
Vaginal swab /microscopy
Will show the presence of clue cells
ALSO TEST FOR STIS to exclude that as a diagnosis
Treatment for BV?
Metronidazole
Who is mostly affected by HIV?
MSM (men sex with men)
Black african
PWID (people who inject drugs)
Prisoners
What is the underlying pathogen causing HIV?
RNA retrovirus targeting CD4
What are symptoms of HIV?
Primary: flu-like ± macpap rash 2-4 weeks post-infection
Seborrheic dermatitis
Worsening psoriasis
Diarrhoea
Lymphadenopathy
Opportunistic infections
How is HIV diagnosed?
HIV antibodies 45 d post-exposure
What is the treatment for HIV?
HAART: 3 drugs w/ at least 2 antiviral classes
If HIV is undetectable. It is also untransmittable. True/false?
True
What type of pneumonia can occur due to HIV?
Fungal pneumonia cause by Pneumocystis jirovecii
What is CD4 count?
A laboratory test that measures the number of CD4 T-cells.
A low CD4 count means that HIV has weakened your immune system.
CD4 of less than 200 indicates AIDS and involves risks of having more serious infections.
At what CD4 count does pneumocytis jirovecii occur?
CD4 count<200
Symptoms of HIV-related pneumonia?
SOB (shortness of breath)
Cough
Diagnosis of HIV-related pneumonia?
Bronchoscopy + lavage (washing out of body cavity with water or medication).
What skin complications can occur due to HIV?
HSV
HPV
VZV
Cerebral toxoplasmosis can also occur due to HIV, what features does this have?
Cerebral abscess + chorioretinitis
What CMV features can occur due to HIV?
Retinitis
Colitis
Oesophagitis
How often is pre-exposure prophylaxis given for HIV?
On a daily basis
Who is given pre-exposure prophylaxis for HIV?
High risk individuals
When is post-exposure prophylaxis given for HIV?
Within 72 hrs of contact
Taken for 4 weeks
Who is given post-exposure prophylaxis for HIV?
Individual had intercourse with a HIV-positive person
What is done during pregnancy to prevent the baby from having HIV?
HAART during pregnancy
Vaginal delivery only if viral load is 0
Baby gets 2 weeks PEP
Cannot breastfeed
What is PID (pelvic inflammatory disease)?
Inflammation and infection of the pelvic organs.
What are the potential causes of pelvic inflammatory disease?
Often caused by STI:
- 1st chlamydia
- Severe gonorrhea
- Mycoplasma
- Gardnerella vaginalis
What increased the risk of PID?
If the patient has a coil fitted
What are the symptoms of PID?
Pelvic/lower abdominal pain
Purulent vaginal discharge
Post-coital or intermenstrual bleeding
Dyspareunia
Dysuria
Examination features of PID?
Pelvic tenderness
Cervical excitation
Inflamed discharge
Complications of PID?
Tubal infertility
Chronic pelvic pain
Ectopic pregnancy
Sepsis
Investigations for PID?
Test for all STI’s
Treatment of PID?
Ceftriaxone → covers gonorrhoea
Doxycycline → chlamydia + mycoplasma
Metronidazole → anaerobes
IV treatment if pregnant or septic
What is the most common cause of Fitz-Hugh-Curtis syndrome?
Chlamydia infection
What is the underlying pathology of Fitz-Hugh-Curtis syndrome?
Inflammation + infection of the liver capsule, leading to adhesions between the liver and peritoneum
Symptoms of Fitz-Hugh-Curtis syndrome?
RUQ pain
Referred pain to right shoulder tip
Investigation for Fitz-Hugh-Curtis?
Laparoscopy to visualise adhesions
Treatment for Fitz-Hugh-Curtis?
Adhesiolysis (a minimally-invasive surgical procedure that breaks up adhesions (scar tissue) and treats the affected area with steroids and other medications).
What is a commensal?
Organism present in body that doesn’t produce inflammatory response
What is an infection?
Presence of an organism with inflammatory response
What is bacteraemia?
Presence of organism in the blood
What is sepsis?
Infection causing dysregulated host response
What is septic shock?
Infection, dysregulated host response and evidence of end organ damage
Who is at increased risk of sepsis?
Immunocompromised
Pregnant
Elderly
Baby
Symptoms of sepsis?
Pain
SOB (shortness of breath)
Symptoms specific to source of infection
Examination features of sepsis?
Tachycardia
Clammy or sweaty
Fever
How is sepsis diagnosed?
NEWS scoring system
Find source
- Blood cultures
- Sputum/stool/urine cultures
- PCR
What should be done within the first hour of suspected sepsis?
Sepsis 6
Give 3, take 3
What are the components of the sepsis 6 (BUFALO)?
Mnemonic (BUFALO):
Blood tests
Urine output
Fluids
Antibiotics
Lactate
Oxygen
What antibiotics are given for sepsis?
Amoxicillin + metronidazole + gentamycin
Vancomycin + metronidazole + gentamycin if penicillin allergy
What NEWS score would raise suspicion of sepsis?
NEWS>5
What are the components of the NEWS score?
RR
SaO2
Systolic BP
HR
AVPU
Temperature
Treatment of bacterial meningitis?
Dexamethasone (steroid) and ceftriaxone (antibiotic)
Treatment for severe community acquired pneumonia?
co-amoxiclav + doxycycline
Treatment for severe hospital acquired pneumonia?
Amoxicillin + gentamycin
Treatment for c.difficile infection?
Oral vancomycin
What is chancre vs chancroid?
Chancres typically appear as painless, firm, round ulcers with a clean base and raised borders.
Chancroids typically appear as painful, soft ulcers or sores with irregular borders and a base covered with grey or yellow pus.
