Microbiology Flashcards
What is post-primary tuberculosis?
aka secondary TB.
Due to reactivation of latent M. tuberculosis or reinfection with M. tuberculosis.
What part of the lungs does post-primary TB usually affect?
Lung apices
What is the classic lesion in post-primary TB?
caseating granuloma.
by what processes does the lesion in post-primary TB heal?
fibrosis and calcification
What is a Ghon focus?
Primary lesion, usually subpleural, caused by M. tuberculosis.
Granulomatous conditions have a certain type of large cell usually found in them, what is that cell?
Langhans Giant Cells
What is the first-line treatment in tuberculosis and for how long?
RIPE
Rifampicin
Isoniazid
Pyrazinamide
Ethambutol
1st two: 6 months. 2nd two: only first 2 months.
Side effects of Rifampicin?
orange secretions
hepatotoxicity
Side effects of Isoniazid? what can you give to combat one of the side effects?
peripheral neuropathy - give B6/pyridoxine
Lowenstein-Jensen medium is a growth medium commonly used to grow what?
M tuberculosis.
Ziehl-Neelsen staining is used to detect what specific type of microorganisms?
Acid-Fast bacteria
A positive Ziehl-Neelsen stain will appear what colour?
Red stain = acid-fast bacteria
Blue stain = non-acid fast
What are the components of the CURB-65 score?
Confusion of new onset blood Urea nitrogen greater than 7mmol/l Respiratory rate greater than 30 Blood pressure lower than 90mmHg systolic or 60mmHg diastolic 65 years or older.
The CURB-65 score is used for what?
predicting mortality in community acquired pneumonia
Rusty-coloured suputum is associated with what infection?
Streptococcus Pneumonia
What microscopic appearance does Streptococcus Pneumonia have?
diplococci
What microscopic appearance does klebsiella pneumonia have?
rod
What microscopic appearance does staphylococcus have?
cocci, grape-bunch clusters
What microscopic appearance does mycobacterium cararrhalis have?
coccus
What microscopic shape does Haemophilus influenza have?
cocco-bacilli
Cold agglutinin test can be used in detecting what bacterial infection?
Mycoplasma pneumonia
What antibiotics would you prescribe for a mild-moderate Community Acquired Pneumonia with classical bacteria and for how long?
Amoxillin or a Macrolide (5-7 days)
What antibiotics would you prescribe for moderate-severe community acquired pneumonia with classical bacteria and for how long?
Clarithromycin + Co-amoxiclav/Cefuroxime (2-3 weeks)
What antibiotic would you use for atypical community acquired pneumonia?
Macrolide/tetracycline
What is 1st line antibiotic treatment for hospital acquired pneumonia?
Ciprofloxacin +/- Vancomycin
Genital ulcers in herpes can be painful or painless?
Painful
Genital ulcers in syphilis can be painful or painless?
Painless
What type of bacteria is Neisseria gonorrhoeae?
Gram negative diplococcus
Opthalmia neonatorum is caused by what organism(s)?
Neiserria gonorrhoeae or Chlamydia trachomatis
Who does opthalmia neonatorum affect and what symptoms does it produce?
It affects newborns
neonatal conjunctivitis: pain/tenderness of eyeball; conjuctival discharge; swollen eyelids.
What can people with complement deficiencies get with gonococcal infections?
Disseminated gonococcal infections –> septicaemia, rash and/or arthritis.
What does NICE recommend to prescribe for uncomplicated anogenital gonorrhoea?
Ceftriaxone 500mg IM as a single dose, plus azithromycin 1g orally.
Cephalosporins are bactericidal or bacteriostatic?
Bactericidal
Cephalosporins belong to what class of antibiotics?
B-lactams
What are the B-lactams’ mode of action?
Bacteriocidal.
B-lactams irreversibly bind to penicillin-binding proteins which prevents final crosslinking of peptidoglycan layers in cell wall synthesis.
What gram type is Chlamydia trachomatis?
Gram-negative
What colour are gram positive bacteria upon staining?
Purple (P for positive/purple)
What colour are gram negative bacteria upon staining?
Red/pink
What are the different biovars of chlamydia trachomatis and what conditions do each cause?
Biovar = a strain within a species
Serovars A, B, C: Trachoma = infection of the eyes –> blindness
Serovars D-K: CUPPP (neonatal Conjuctivitis, Urethritis, ectopic Pregnancy, Pelvic inflammatory disease, neonatal Pneumonia)
Serovars L1-3: Lymphogranuloma venereum
What is NICE first-line treatment for Chlamydia?
Azithromycin 1g single dose OR doxycycline 100mg BD for 7 days.
What is NICE treatment for Chlamydia infection in pregnant/breastfeeding women?
Azithromycin 1g single dose OR
Amoxicillin 500mg TDS for 7 days OR
Erythromycin 500mg QDS for 7 days
What organism is lymphogranuloma venereum caused by?
Chlamydia trachomatis
What site-specific signs/symptoms can lymphogranuloma venereum present with?
External sex organs: abscesses in the groin (around draining lymph nodes)
Rectal: Proctocolitis
The primary stage of lymphogranuloma venereum occurs how long after infection?
3-12 days after infection
The secondary stage of lymphogranuloma venereum occurs how long after infection?
10-30 days later or even up to six months after infection.
What sign/symptom do people get in primary lymphogranuloma venereum?
Painless genital ulcer.
What signs/symptoms can people get in secondary lymphogranuloma venereum?
unilateral painful buboes (enlarged lymph nodes)
What is first-line treatment for lymphogranuloma venereum? An alternative?
Doxycycline 100mg BD for 21 days
alternative: Erythromycin QDS for 21 days.
What organism causes syphilis?
Treponema pallidum
Treponema pallidum is what gram-type?
negative
What blood tests can we use to diagnose syphilis?
Non-treponemal tests: Venereal Disease Research Laboratory (VDRL) and Rapid Plasma Reagin
Treponemal tests:
Treponemal pallidum particle agglutination (TPHA) or Fluorescent Treponemal Antibody Absorption (FTA-Abs)
What signs may a person have with primary syphilis?
Macule –> papule –> ulcer/erosion.
1-12 weeks following transmission.
What is a chancre?
Painless solitary ulceration associated with treponema pallidum infection. Appear approximately 3 weeks after infection.
Condylomata lata are associated with what organism?
Treponema pallidum
What skin symptoms can secondary syphilis present with?
Symmetrical, reddish, non-itchy maculopapular/pustular rash on the trunk, palms and/or soles.
What non-specific symptoms can syphilis present with?
Fever
Sore throat
Weight loss
Headache
How long after initial infection does tertiary syphilis present?
YEARS, like 3-40 years later.
What three different forms of tertiary syphilis are there?
Gummatous syphilis
late neurosyphilis
cardiovascular syphilis
What form in gummatous syphilis and where?
Gummas - soft, tumour-like balls of inflammation.
Can affect skin, bone, liver but can occur anywhere.
What are Argyll Robertson pupils and what are they a sign of?
Small pupils that constrict to near objects (accomodate) but do not constrict in response to bright light.
Sign of neurosyphilis, diabetic neuropathy.
What is General Paresis?
neuropsychiatric disorder caused by chronic meningoencephalitisi leading to cerebral atrophy in neurosyphilis.
What is Tabes Dorsalis?
Demyelination of the dorsal columns in the spinal cord
What are late symptoms of neurosyphilis?
General paresis, Tabes Dorsalis, Menigovascular syphilis
What is first-line treatment for syphilis?
Benzathine benzylpenicillin
The Jarisch-Heimer reaction is classically caused by what?
Antibiotic treatment of syphilis.
How soon does a Jarisch-Heimer reaction occur and what are the signs/symptoms?
Hours after administration of antibiotics.
Fever, chills, rigor, hypotension, tachycardia, myalgia, flushing - it mimics septicaemia basically!
What organism causes chancroid? and what gram-type is it?
Haemophilus ducreyi: gram-negative.
What is a chancroid?
Painful ulcer, can be found around inguinal lymph nodes
What organism causes Granulom inguinale and what Gram-type is it?
aka Donovanosis
Klebsiella granulomatis: gram-negative.
What do we do to diagnose granuloma inguinale?
Giemsa stain
Look for Donovan bodies in tissue biopsy
What organism causes trichomoniasis?
Trichmonas vaginalis
What can you prescribe in trichomoniasis?
Metronidazole
What organism causes molluscum contagiosum?
DNA poxvirus, aka molluscum contagiosum virus.
Which organism can cause genital warts?
Human Papillomavirus 6 or 11.
Which HPV types are associated with cervical/anal/penile cancers?
16 and 18
What is Tinea?
Common fungal infection of the skin, e.g. Athelete’s foot.
What are the signs/symptoms in Tinea versicolor?
Fine-scaling of the skin
Hypopigmentation eruption on trunk/proximal extremities.
Polyenes antimycotics work by what action?
Bind to ergosterol in fungal cell membrane, reduce integrity and can cause K/Na loss.
Azole antimycotics work by what action?
Inhibit lanosterol–>ergosterol conversion in cell membrane thereby inhibiting cell growth.
How do echinocandins work?
Inhibit glucan synthesis in cell walls
Herpes Simplex Virus is ssDNA or dsDNA?
dsDNA
Which organism causes Mollaret’s Meningitis?
HSV
What is Mollaret’s meningitis?
benign recurrent aseptic meningitis >4 weeks
Signs/symptoms of Mollaret’s meningitis?
Meningism (Neck stiffness, photophobia, irritation) CSF pleocytosis (increased cell count) with large endothelial cells.
Symptom-free periods of weeks/months inbetween bouts.
Primary infection in the ocular region with HSV can manifest in what condition, the symptoms/signs of which are?
Herpetic keratitis
Blepharoconjuctivitis (swelling of lids and conjuctiva)
Lid vesicles
Define a dendritic ulcer?
A linear branching corneal ulcer.
What symptoms might a person with a dendritic ulcer complain of?
Sensation of foreign-body
Redness
Light sensitivity
Blurred vision
In what condition do dendritic ulcers usually appear?
Herpetic Keratitis
Disciform keratitis usually manifests itself how?
Disc shaped area of corneal oedema
Disciform keratitis is caused by what organism?
HSV
In which trimester of pregnancy is the foetus at greatest risk when the mother has a primary HSV infection?
3rd trimester
Which HSV is the usual suspect in viral encephalitis?
HSV-1
What are some symptoms of herpesviral encephalitis?
CCC
Confusion
Changes in personality
Consciousness reduced
as well as …
N+V, fever, focal neurology
What one test would you like to perform to confirm a diagnosis of herpesviral encephalitis? What are you looking for?
Lumbar puncture and analyse CSF.
Look for:
Lymphocytic pleiocytosis
Presence of virus - PCR
How would you treat somebody you suspect of herpesviral encephalitis?
IV acyclovir ASAP!
What are the signs/symptoms of herpes gladiatorum?
Scrum pox (painful blisters around the neck, face, chest, stomach, legs; inguinal lymphadenopathy)
Tzanck cells can be found in what infections?
‘Her Very Heavy Pearly Case’
Herpes Simplex
Varicella + Herpes Zoster
Pemphigus vulgaris
Cytomegalovirus
If indicated, what would you prescribe for chickenpox?
Aciclovir
Shingles is caused by what infection?
Herpes Zoster
What is the presentation of congenital cytomegalovirus infection?
Generalised: IUGR; Microcephaly; Chorioetinitis; Thrombocytopenia; Hepatosplenomegally; Impaired IQ.
What diseases are immunocompromised patients at risk of when exposed to CMV infection?
CHERP
CMV Colitis CMV Hepatitis CMV Esophagitis CMV Retinitis CMV Pneumonitis
What would you prescribe to an immunocompromised patient with CMV infection?
Ganciclovir
What infection causes roseola infantum?
HSV 6 and HSV 7 aka Roseola Virus
Who is most likely to develop roseola?
Children under 2 years old
What is a typical presentation in a patient with Roseola?
A few days of fever, subsides and then a red rash appears spreading to legs/neck.
What might you prescribe to a patient with Roseola?
Ganciclovir, foscarnet or cidofovir
What is the characteristic presentation of infectious mononucleosis?
Triad of:
Fever
Sore throat
Lymphadenopathy
What type of rash can a person develop in infectious mononucleosis?
Maculopapular rash
A positive monospot test indicates what?
Epstein-Barr Virus infection
The monospot test responds to the presence of what specifically?
antibodies produced in response to EBV
Which infection is associated with Kaposi’s sarcoma?
HHV-8
What does PUO stand for?
Pyrexia of Unknown Origin
What is the classical definition of PUO?
> 38.8C fever
Persisting >3 weeks
Despite >1 week of intensive investigations
What conditions are classed as ‘classical PUO’
5 categories:
1) Infections
2) Neoplasms
3) Connective Tissue Diseases
4) Miscellaneous (e.g. alcoholic hepatitis, granulomatous conditions)
5) Undiagnosed
How can you define nosocomial PUO?
Pyrexia that develops in patients that have been in hospital >24 hours
Causes of nosocomial PUOs?
Think of a patient lying on a bed post-surgery:
Surgery Immobilisation IV lines Urinary catheters Drugs
How can you define neutropaenic PUO?
Pyrexia with neutropaenia (
Causes of a neutropaenic PUO?
Chemotherapy
Haematological malignancies
What are the different classes of PUO?
1) Classical
2) Nosocomial
3) Neutropaenic
4) HIV-associated
Which organism causes Typhoid? What gram-type is it?
Salmonella typhi
Gram negative
What is Faget sign?
Fever paired with bradycardia
What skin changes can be seen in Typhoid?
Rose spots (red macules 2-4mm )
What are the symptoms of untreated Typhoid?
Fever, abdominal pain, headache, epistaxis, exhaustion.
What test do you want to perform to confirm your diagnosis of Typhoid?
Blood or stool cultures
What is first-line treatment of Typhoid?
IV fluids
Fluoroquinolones, e.g. ciprofloxacin.
Which species cause malaria?
P. Falciparum P. Vivax P. Ovale P. Malariae P. Knowlesi
On a blood film you see:
Young trophozoites alonside crescent-shaped gametocytes.
What is the cause?
P. Falciparum
A patient with P. Falciparum would show what on a blood film?
Young trophozoites (rings). Crescent-shaped gametocytes.
How can you treat P. Falciparum?
One option is using ‘Artemisinin based combination therapies’ aka ACTs.
Another option is Quinine plus tetracycline/doxycycline/clindamycin for 7 days.
You see a blood film report: ‘Schuffner’s dots’ are present. What could have caused this?
P. Vivax or P. Ovale.
In malarial investigations, what can we use a thick film for?
Detect the presence of parasites
In malarial investigations, what can we use a thin film for?
Distinguishing malarial species
What are the classic triad of symptoms in botulism?
1) bulbar palsy (CN IX, X, XI, XII) and descending paralysis
2) lack of fever
3) clear sense and mental status
Classical sources of botulinum toxin?
Honey (children) Canned food Open wound Inhalation (lab workers) Inappropriate injection
What gram-type is Clostridium Botulinum?
Gram Positive
Sources of C. Perfringens?
Reheated/poorly heated meats
Decaying vegetation
Faeces
Marine sediment
Effects of C. Perfringens infection?
Food poisoning - third most common cause of food poisoning in the UK.
Signs/symptoms of C. dificile?
>3 watery stools in 24 hour period Recent Abx exposure Abdominal pain Fever Foul odour stool
Sources of Bacillus cereus?
Poorly refrigerated cooked rice, milk or infant formula.
What is the route of transmission for E. coli?
faeco-oral route
Which enterotoxins does ETEC produce?
LT and ST enterotoxins
What are the effects of ST enterotoxin produced by ETEC?
stimulates cGMP accumulation in target cells
leads to fluid/electrolyte moving into intestinal lumen
What gram-type is E. Coli?
Negative
What gram-type is Salmonella?
Negative
What gram-type is Shigella?
Negative
Through what route does Shigella invade the host?
Through M cells within the small intestine
Common symptoms of Shigella infection?
Diarrhoea Nausea Vomiting Fever Stomach cramps
What gram-type is Yersinia enterocolitica?
Negative
What is the usual source of Yersinia enterocolitica?
Poorly cooked pork
Contaminated water, meat, milk
Symptoms of Yersinia enterocolitica?
Diarrhoea
Fever
Mimics shigella infection/appendicitis
Later, lymphadenopathy