Theme 1: Core Microbiology Flashcards
Staphylococcus aureus is most commonly infects which tissue?
Skin and soft tissue
Esp. surgical sites
Which bacteria is most commonly associated with foreign bodies (IV catheters, prosthesis, mechanical valves)?
Staphylococcus epidermidis
Which bacteria adheres to metals and plastics using glycocalyx slime to form a biofilm?
Staphylococcus epidermidis
Where is staphylococcus epidermidis normally found?
On the skin
Group A Strep is also called ____?
streptococcus pyogenes
A patient presents with a tongue that is covered in small lesions, making it look a lot like a strawberry. What is the classical diagnosis and which pathogen is responsible?
Strawberry tongue is characteristic of scarlet fever, which is caused by streptococcus pyogenes
True or false: Group A Strep can cause skin and soft tissue infections?
True.
But it is most commonly associated with scarlet fever and necrotising fasciitis.
What is the most common cause of bacterial pneumonia?
Streptococcus pneumoniae
Which gram positive bacterial species looks like bunches of grapes?
Staphylococcus spp.
Which gram positive bacterial species forms chains?
Streptococcus spp.
Streptococcus pneumoniae is a cause of bacterial meningitis in all age groups EXCEPT ____?
neonates
True or false: Streptococcus Pneumoniae can cause otitis media?
True
Strep Pneumoniae is the most common cause of bacterial pneumonia, but can also cause other diseases such as meningitis and otitis media.
What is Group B Strep also known as?
Streptococcus agalactiae
Which pathogen is the most common cause of bacterial meningitis in neonates?
Group B strep/ streptococcus agalactiae
Also the most common cause of neonatal sepsis (neonates = <3 months)
Which gram positive bacterial pathogen is most associated with abscesses?
Streptococcus milleri.
This is actually a collective term for a group of three closely-related species of pus-forming streptococci.
The abscesses can be found in diverse places, such as teeth, lung, liver and brain.
Subacute bacterial endocarditis is associated with which group of gram positive bacteria?
Viridans streptococci
This group includes strep. oralis and strep. mitis.
They are named after the latin word for ‘green’ (viridis) because they produce a green colouration on agar plates.
Blood cultures for a patient on your ward grow streptococcus gallolyticus. What can this be a red flag symptom for?
Colonic malignancy
Strep gallolyticus is an alpha-haemolytic strep species that is found in the normal bowel flora.
Bacteraemia with this organism can be associated with colonic malignancy.
A patient presents with a non-blanching rash and is diagnosed with meningitis. Which organism is most likely responsible for their meningitis?
Neisseria meningitidis
This organism is associated with the classic presentation of a non-blanching rash.
Are the neisseria species’ gram negative or gram positive?
Gram negative
Which organism is the cause of gonorrhoea?
Neisseria gonorrhoeae
Ophthalmia neonatorum is caused by which organism(s)?
Neisseria gonorrhoeae and chlamydia trachomatis
How is ophthalmia neonatorum contracted?
The baby becomes infected during childbirth as it passes through the vaginal canal of a mother infected with neisseria gonorrhoeae or chlamydia trachomatis.
Which pathogen is associated with consuming cheese from unpasteurised milk?
Listeria monocytogenes
Which groups are most at risk of meningitis and sepsis from listeria monocytogenes?
- Pregnant
- Immunosuppressed
- Neonates
(PIN)
Is listeria monocytogenes gram negative or gram positive?
Gram positive
They would stain dark on a gram film, as their cell wall will retain the dye
Zoonosis most commonly affects animals, but can spread to humans through meat or spreading manure on food products. If a colony of the causative bacteria was to be gram-stained, what colour would it appear?
Dark as it would retain lots of the gram stain.
Zoonosis is caused by listeria monocytogenes, which is gram positive. As gram positive bacteria have a thick cell wall, they retain lots of stain and appear dark. Gram negative bacteria appear more reddish, as their thin little cell wall doesn’t retain much stain.
True or false: Listeria monocytogenes can grow in low temperatures.
True
Many of the corynebacterium species are commensals of the skin and upper respiratory tract. Which of them causes diphtheria?
Corynebacterium diphtheriae
gram+ bacilli
____ causes acne and, less commonly, device-associated or post-procedural infections.
Propionibacterium acnes
E-coli is most commonly associated with ____.
UTIs
E-coli is commensal in the bowel flora but not the urethra.
This species is also associated with
- Bacteraemia
- Hospital acquired infections (line infections, pneumonia, wound infections)
- [toxigenic strains] Severe diarrhoea and haemolytic uraemic syndrome (HUS)
Which pathogen is associated with a 3 day history of bloody diarrhoea, abdominal pain and fever?
A) E-coli
B) Giardia
C) Streptococcus pyogenes
D) Shigella
D) Shigella
Which gram negative species is known for its blue-green pigmentation?
Pseudomonas aeruginosa
Which of the following is not generally caused by pseudomonas aeruginosa?
A) Respiratory infections
B) SSTIs
C) UTIs
D) These are all caused by pseudomonas aeruginosa
D) These are all caused by pseudomonas aeruginosa
True or false: Haemophilus influenzae is commensal to the respiratory tract
True
Haemophilus influenzae is found as part of the normal respiratory tract flora
Which gram negative species is associated with pneumonia and infective exacerbation of COPD?
Haemophilus influenzae
Which gram negative species is associated with meningitis and epiglottitis?
Capsulated strains of haemophilus influenzae (e.g. Type B)
Lyme disease is caused by which organism?
Borrielia
Leptospira is associated with what disease?
Leptospirosis
Syphilis is caused by which organism?
Treponema pallidum
Clostridium spp, bacteroides, fusobacterium and prevotella are all examples of:
A) Anaerobes
B) Aerobes
A) Anaerobes
What are the four main subtypes of clostridium species? What condition does each cause?
- Clostridium difficile (diarrhoea/colitis)
- Clostridium perfringens (gas gangrene)
- Clostridium tetani (tetanus)
- Clostridium botulinum (botulism)
True or false: The organism responsible for tuberculosis can be identified with the help of gram staining
False
TB is caused by mycobacterium tuberculosis. Mycobacterium do not have a cell wall, so you cannot stain them using conventional gram stain.
Mycobacterium tuberculosis
Mycobacterium pneumoniae
Chlamydia trachomatis
What do these species have in common?
None of them have a cell wall
____ often form polybacterial infections; commonly: dental infections, lung abscesses, colonic abscesses, post-trauma SSTIs.
Anaerobes
Which species most commonly cause meningitis in these age groups:
a) Neonates (<3 months)
b) Infants
c) Teens/adults
d) Elderly
a) Neonates (<3 months): GROUP B STREP (STREP AGALACTIAE)
b) Infants: STREP PNEUMONIAE
c) Teens/adults: NEISSERIA MENINGITIDIS
d) Elderly: STREP PNEUMONIAE
Which of the following are gram negative bacteria?
A) Streptococcus pneumoniae B) Mycobacterium tuberculosis C) E-Coli D) Listeria monocytogenes E) Neisseria gonorrhoeae F) Mycoplasma pneumoniae
C) E-Coli
E) Neisseria gonorrhoeae
Explanation:
A) Streptococcus pneumoniae (G+)
B) Mycobacterium tuberculosis (no cell wall, no stain)
C) E-Coli (G-)
D) Listeria monocytogenes (G+)
E) Neisseria gonorrhoeae (G-)
F) Mycoplasma pneumoniae (no cell wall, no stain)
Which of these bacteria is common cause of skin infection?
A) Klebsiella pneumoniae B) Streptococcus pneumoniae C) Haemophilus influenzae D) Neisseria meningitidis E) Staphylococcus aureus F) Clostridium difficile
E) Staphylococcus aureus
Most common infections:
- Klebsiella pneumoniae: pneumonia
- Streptococcus pneumoniae: pneumonia
- Haemophilus influenzae: pneumonia
- Neisseria meningitidis: meningitis
- Staphylococcus aureus: SSTIs
- Clostridium difficile: Colitis
Which of the following is the most common sexually transmitted infection?
A) Chlamydia trachomatis B) Treponema pallidum C) Corynebacterium diphtheriae D) Staphylococcus aureus E) Neisseria gonorrhoeae F) Viridans streptococci
A) Chlamydia trachomatis
Which of the following can cause meningitis?
A) Neisseria meningitidis B) Streptococcus pneumoniae C) Listeria monocytogenes D) Streptococcus agalactiae E) Haemophilus influenzae F) Staphylococcus aureus
These can ALL cause meningitis
Albicans, glabrata, parapsilosis and krusei are all subtypes of which species?
Candida
Candida spp. are yeasts that can infect any organ, superficially or systemically.
Which organism is responsible for thrush?
Candida
Which groups are at greatest risk of developing oral candidosis (thrush)?
- HIV/AIDS
- Antibiotic use
- Chemo/radiotherapy for head and neck cancers
- Hospital inpatients
What should be remembered when prescribing a treatment for candida infection in pregnant women?
Oral azoles can cause teratologies in the developing foetus. Therefore, do not prescribe fluconazole or other oral azoles. Use topical preparations instead, such as clotrimazole.
Your patient recently had an in-dwelling catheter fitted. They became unwell and blood cultures have grown a candida spp. What action should be taken?
- Remove the line
- Start antifungal therapy
- Investigate the source and spread of candida - especially check heart and eyes
Which groups are at highest risk of candida endocarditis?
- IV drug users
- Patients who have had heart valve surgery
Why is candida UTI hard to treat?
Few antifungals are excreted in the urine, therefore it is difficult to get a drug to the infection site.
True or false: You can have a candida UTI but test negative for candiduria.
True
Candida oesophagitis is mainly found in patients with __1__. It causes pain/difficulty swallowing and is diagnosed by __2__ and biopsy.
- HIV
2. endoscopy
Patients undergoing leukaemia treatment are more at risk of which candida infection?
Hepatosplenic candidosis
The fungus takes advantage of the neutropenic state of the blood and lodges in the liver, spleen and [occasionally] kidney.
Abscesses, fever and deranged LFT results on presentation.
Fumigatus, niger, flavus and terreus are all subtypes of which species?
Aspergillus
A ‘halo’ or ‘air crescent’ sign on CT is indicative of which fungal disease?
Invasive pulmonary aspergillosis
Allergic bronchopulmonary aspergillosis is mediated by what? What treatment is effective?
IgE and IgG reaction to mould. Responds well to steroid and antifungal treatment.
A patient presents with the following:
- COPD
- Consolidation and cavitation seen on CT
- Sputum culture +ve for aspergillus
- Blood serum +ve for aspergillus IgG antibody
What is the likely diagnosis?
Chronic pulmonary aspergillosis (CPA)
Which class of fungi are slow-growing moulds that live in soils, on animals and on humans? What type of infection are they associated with?
Dermatophytes
Skin, nail and hair infections
The following organisms belong to which species?
Trichophyton rubrum
Trichophyton verrucosum
Trichophyton Schoenleinii
Microsporum canis
Dermatophytes
A family of slow-growing moulds that live in soil, as well as on animals and humans.
They cause skin, nail and hair infections
Give the main examples of infections caused by dermatophytes.
Tinea pedis (athletes foot) Tinea unguium (fungal nail) Tinea cruris (jock itch) Tinea corporis (ringworm) Tinea capitis (scalp ringworm) Tinea barbae (facial hair infection)
What is the cause of pityriasis versicolor?
Malassezia - a yeast fungi
Hypo- or hyperpigmented lesions on the upper trunk that are caused by a yeast are most likely to be a case of ____
Pityriasis versicolor
How is pityriasis versicolor treated?
Treat with topical antifungals (clotrimazole). If this fails, oral antifungals (fluconazole or itraconazole).
What term describes a relationship where two organisms of different species live together closely.
Symbiosis
What is the difference between protozoa and helminths?
Both are subtypes of parasite:
Protozoa are microscopic; helminths are macroscopic
Define the following:
a) Definitive host
b) Intermediate host
c) Paratenic host?
a) Definitive host: Host that harbours adult-stage parasites (i.e. a parasite that can sexually reproduce).
b) Intermediate host: Host that harbours larval or asexual stages of the parasite.
c) Paratenic host: Host which carries a viable parasite, without further development.
Which of the following causes Loeffler’s syndrome?
a) Schistosoma
b) Echinococcus
c) Cryptosporidium
d) Ascaris
Ascaris
Loeffler’s syndrome occurs when an increase in eosinophils (in response to a parasitic infection) leads to eosinophil accumulation in the lungs. This results in dry cough, dyspnoea, wheeze, haemoptysis. Eosinophilic pneumonitis can be a sequela.
What type of parasite is ascaris? Protozoa or helminth?
Ascaris is an intestinal nematode (worm) which makes it a helminth (i.e. macroscopic parasite).
How is ascariasis acquired?
Ingestion of eggs.
Each adult ascaris worm can produce 200,000 eggs per day.
Describe the ascaris life cycle
Direct life cycle: Oral-faecal.
Excreted fertilised eggs are ingested and develop in the intestines into larvae. The larvae invade the mucosa and are carried to the lungs by the blood. They then develop further and ascend the respiratory tract into the throat and are swallowed. Back in the intestine, the worms mature to adulthood.
What clinical manifestation might be seen in a patient with ascariasis?
Loeffler’s syndrome, malnutrition, malabsorption, bowel obstruction
Loeffler’s syndrome: dry cough, dyspnoea, wheeze, haemoptysis, eosinophilic pneumonitis
How is Loeffler’s syndrome diagnosed?
Sample to identify the eggs or worms
What causes schistosomiasis?
Infection by schistosoma species
Trematode (fluke) helminth
What causes swimmer’s itch and Katayama fever?
Schistosoma infection
Katayama Fever is the acute phase of schistosomiasis. There is also a chronic phase, just called chronic schistosomiasis.
Describe the life cycle of schistosoma
Simple indirect life cycle:
Infected person excretes eggs in faeces and urine. Eggs make it to water and hatch. The larvae infect snails (intermediate host) and develop into a swimming bug. Leave snail, penetrate the skin of of a bathing person (definitive host). Migrate to bloodstream, mate and produce eggs.
How might schistosomiasis manifest in the urinary bladder?
Haematuria
Fibrosis and dysfunction
Squamous cell carcinoma
How might schistosomiasis manifest in the GI tract?
Portal hypertension
Liver cirrhosis
Abdominal pain
Hepatosplenomegaly
How is schistosomiasis diagnosed?
Urine:
- Terminal stream microscopy
GI:
- Stool microscopy
- Rectal snip microscopy
General:
- Serology (only an aid, as eggs in blood do not indicate active infection)
What controls could be implemented to prevent schistosomiasis?
- Chemical treatment to kill snail intermediates
- Chemoprophylaxis
- Avoid snail waters
- Improve sanitation to prevent faeces and urine reaching water
- Education
- Community treatment programme
What disease is caused by echinococcus?
Hydatid disease
Hydatid disease is caused by which organism?
Echinococcus (tapeworm)
What type of parasite is echinococcus?
Helminth (i.e. macroscopic)
Cestode (tapeworm)
What are the usual hosts of echinococcus?
Sheep and dogs
Echinococcus are found anywhere sheep are farmed. Humans are accidental hosts
Describe the life cycle of echinococcus
Indirect life cycle.
Eggs pass from faeces of infected dogs, ingested by sheep and other farm animals. Cysts pass from intestine of sheep to their other tissues. Dogs eat these meats/organs and ingest the cysts, which then develop into adulthood.
Sheep are the intermediate host, dogs are the definitive host.
Humans can contract the cysts and would become an intermediate host, in place of the sheep.
True or false: Infection of echinococcus is normally asymptomatic.
True, infected humans can by asymptomatic for years.
However, mass effect can lead to symptoms. Also associated with secondary bacterial infections and hypersensitivity reactions. Cyst rupture (possibly due to trauma) can cause a mild to severe anaphylactic reaction.
How is hydatid disease diagnosed?
Imaging
Serology
Which site is most commonly affected by hydatid disease?
Majority of cysts migrate to liver (70%).
Some also migrate to lungs (20%) and other tissues.
What controls can be put in place to manage hydatid disease?
- Regularly worm dogs to reduce egg production
- Hand hygiene
- Safe handling and disposal of animal carcasses and products
What treatment might be used for hydatid disease?
If asymptomatic, no treatment required.
Cysts may need to be surgically removed.
Which species causes malaria?
Plasmodium
Plasmodium falciparum is commonest in the UK
What type of parasite causes malaria?
Plasmodium spp, which are a family of sporozoa from the protozoa class.
Describe the life cycle of the parasite that causes malaria
Indirect life cycle.
Female anopheles mosquito picks up plasmodium parasite when feeding and acts as a vector to take it to another host. Injects it into the new host’s blood where it travels to the liver and infects blood cells and grows to adulthood.
How does the plasmodium protozoa cause problems?
It gets into an erythrocyte and replicates until the cell ruptures.
Ruptured erythrocytes can block vessels and trigger inflammatory reactions.
Symptoms:
- Fever and rigors
- Cerebral malaria: confusion, headache, coma
- Renal failure
- Hypoglycaemia
- Pulmonary oedema
- Circulatory collapse
- Anaemia, bleeding and DIC (disseminated intravascular coagulation)
If your patient has a fever and has recently returned from travelling abroad, what assumption should you make?
Malaria
How is malaria diagnosed?
Thick and thin microscopy
Serology - detect antigen
PCR - detect malarial DNA
Which organisms cause cryptosporidiosis?
Cryptosporidium parvum and hominis
Protozoa/ Sporozoa
Describe the life cycle of cryptosporidium spp.
Direct life cycle.
Faecal-oral transmission.
Animal to human
Human to human
Water can be infected and ingested.
How does cryptosporidiosis present clinically?
7-day incubation followed by watery diarrhoea with mucus (no blood).
Cramps, bloating, fever, nausea, vomiting.
Self-limiting, 2 weeks.
How is cryptosporidiosis diagnosed?
Stool sample with acid-fast stain
Antigen detection by EIA (enzyme immunoassay)
What treatment is given to patients with cryptosporidiosis?
Symptomatic relief (rehydration, electrolyte replacement etc)
If immunocompromised:
- Paromomycin (kills parasite)
- Octreotide (reduce cramps)
- HAART activation if HIV+
Trichomoniasis is caused by which parasite?
Trichomonas vaginalis
What type of parasite is trichomonas vaginalis?
Flagellated protozoa
How is trichomonas vaginalis transmitted?
Sexual transmission
How does trichomoniasis present clinically?
Men: asymptomatic
Women: Smelly vaginal discharge, dyspareunia (painful sex), dysuria, abdominal discomfort, strawberry cervix
How is trichomoniasis diagnosed?
Microscopy of genital specimens
How is transmission of trichomonas prevented?
Barrier contraception
Giardia causes what symptoms?
1 to 3 weeks of:
- Diarrhoea
- Abdo pain
- Bloating
- Nausea/vomiting
How is giardiasis diagnosed?
Stool sample microscopy to identify cysts or trophozoites
What can be done to control giardia infection?
- Boil/filter water
- Improve hygiene and sanitation
How can malaria infection be controlled?
Insecticide sprays in homes
Larvacidal spraying on breeding pools
Filling in of breeding pools
Larvivorous species introduced to mosquito breeding areas
Insecticide-impregnated bed nets
Chemoprophylaxis
Vaccine? - possibly in the future.
What is the life cycle of a virus?
Attachment Entry Uncoating Synthesis Assembly Release
What characteristic is distinguishing of the herpes viruses?
Their ability to establish latency and then reactivate.
Which virus is responsible for the following:
a) Genital herpes
b) Cold sores
a) Genital herpes is caused by Herpes Simplex 2 (HSV-2)
b) Cold sores are caused by Herpes Simplex 1 (HSV-1)
What is the mode of transmission for herpes simplex 1 and 2?
Direct contact with vesicle fluid from HSV lesions (skin, genital, eye)
Where does herpes simplex 1 (HSV-1) establish latency?
Sensory neurons
Where does herpes simplex 2 (HSV-2) establish latency?
Sensory neurons
What clinical syndromes are associated with herpes simplex 1 and 2?
Ulcers: skin or mucous membranes - typically mouth (HSV-1) and genitals (HSV-2)
Encephalitis: majority HSV-1
Meningitis: majority HSV-2, often follows genital lesions
Neonatal herpes: contracted from mother’s genital tract at delivery
The primary infection of varicella zoster virus is known as __1__; the reactivation is known as __2__.
1) ‘chicken pox’
2) ‘herpes zoster’ or ‘shingles’
How is varicella zoster transmitted?
Respiratory droplets or contact with vesicle fluid
Where does varicella zoster establish latency?
Dorsal root ganglion
Which of the following is not associated with chicken pox?
a) Complications can include pneumonitis, encephalitis and acute cerebellar ataxia
b) Unilateral vesicles in a dermatomal distribution
c) Febrile illness with vesicular rash
d) Usually uncomplicated in children
b) Unilateral vesicles in a dermatomal distribution
Chicken pox presents as a febrile illness with a widespread vesicular rash.
Though it is usually uncomplicated (esp. children), it can result in pneumonitis, encephalitis and acute cerebellar ataxia.
A unilateral distribution of vesicles in a single dermatome is characteristic of the reactivated form, shingles (or herpes zoster).
What causes glandular fever?
Epstein Barr virus (80-90%)
Cytomegalovirus (10-20%)
These names are all synonyms of the same disease:
- glandular fever
- infectious mononucleosis
- epstein barr virus
How is epstein barr virus transmitted?
Saliva and genital secretions
“Kissing disease”
Also known as mono (infectious mononucleosis) and glandular fever
What is the usual clinical presentation of the primary disease caused by the Epstein Barr virus?
Causes infectious mononucleosis (glandular fever/EBV)
Sore throat, fever, lymphadenopathy, hepatosplenomegaly
Atypical lymphocytes on blood film (look like monocytes - mononucleosis)
Where does Epstein Barr virus establish latency?
In B cells
Turn over for a cool fact.
You are awesome. And you’re doing great. Keep going!
True or false: In the UK, % prevalence ~ age (e.g. 20% of 20 year olds, 50% of 50 year olds)
True
How is CMV transmitted?
Saliva/genital secretions
Donated blood, stem cells, organs
Where does cytomegalovirus establish latency?
In monocytes, dendritic cells, myeloid progenitors
i.e. the immune system
What is the most common primary condition associated with CMV?
Infectious mononucleosis
80-90% of cases are caused by EBV, the rest are CMV.
What symptoms might you expect a baby to born with if their mother contracted CMV while pregnant?
Congenital CMV infection:
Retinitis, deafness, microcephaly, hepatosplenomegaly
Which pathogen causes the common cold?
Rhinovirus
‘rhino’ = nose
Which common virus can infect animals as well as humans, and can spread between species?
Influenza
Which influenza strain mutates regularly?
Influenza A
What are the two important viral markers on influenza, variants of which are used to identify different strains?
H and N
e.g. H1N1 is swine flu, H3N2 is seasonal
Which virus infects 70% of children within their first year of life?
Respiratory syncytial virus (RSV)
What virus causes bronchiolitis? Describe the condition.
Bronchiolitis is caused by respiratory syncytial virus (RSV). It affects children under 2 years, due to their small lungs.
Bronchiolitis is inflammation of the smallest airways: the bronchioles.
Symptoms: cough, wheeze, hypoxia, fever.
What is the target for the HIV virus?
Helper T cells (CD4)
What symptoms commonly affect people who have recently contracted HIV (2-6 weeks ago)?
Acute seroconversion illness:
- fever
- sore throat
- lymphadenopathy
How long can the asymptomatic chronic phase of HIV last?
Usually 5-15 years
When does HIV become classified as AIDS?
AIDS
Increase in viral load and fall in CD4 count, infection by one of the AIDS-defining illnesses:
TB, pneumocystis pneumonia, cryptococcal meningitis, cerebral toxoplasmosis, Kaposi’s sarcoma.
What are the AIDS-defining illnesses?
- TB
- Pneumocystis pneumonia
- Cryptococcal meningitis
- Cerebral toxoplasmosis
- Kaposi’s sarcoma.
What are the 5 primary hepatotropic viruses?
Hep A, B, C, D and E
Hepatitis D is defective and can only survive with hep B.
Of the 5 hepatotropic viruses, which are:
a) blood borne
b) faeco-oral spread
a) blood borne: hep B, C, D
b) faeco-oral spread: hep A and E
Which age group is most affected by Hep A in endemic countries?
Children.
Hep A is an infection of childhood, more than 90% of children under the age of 5yrs have been exposed in endemic countries.
How is Hep A transmitted?
Faeco-oral
How does Hepatitis A present clinically?
Nausea, myalgia, arthralgia and fevers
then jaundice and right upper quadrant pain
Self limiting
How do different age groups present when infected with Hep A?
Children under 5 usually asymptomatic.
50% of infected adults are symptomatic
Which groups are at highest risk of contracting Hep A?
- Lower socio-economic groups
- Returning travellers
- MSM
Which hepatitis virus is associated with undercooked pork?
Hepatitis E
How is Hep E transmitted?
Faeco-oral
True or false: vast majority of patients with Hep E are symptomatic.
False. Vast majority are asymptomatic. Clinical symptoms occur in 2-5% of patients with acute HEV.
Nausea, myalgia, arthralgia and fevers
then jaundice and right upper quadrant pain – self limiting
Which groups are at high risk of severe condition if infected with hepatitis E?
Pregnant women at high risk of fulminant hepatitis, with high mortality (25%)
Also more severe in older males and those with chronic liver disease.
How is Hepatitis B transmitted?
Blood borne
Vertical, sexual and parenteral
(parenteral = blood products, organ transplant etc.)
Following infection of HBV, acute clinical hepatitis may occur.
This acute infection is either cleared, or develops into chronic infection.
How does chronic hepatitis develop further?
Chronic hepatitis –> cirrhosis –> hepatocellular carcinoma
HBV = hepatitis B virus
How is risk of developing chronic hep B related to age at infection?
Risk of chronicity is inversely related to age at infection
In the UK, 50% of IVDUs have evidence of hepatitis ____
c
How is hepatitis C transmitted?
Blood borne.
IVDU, needlestick injury, transfusion of contaminated products.
Vertical and sexual transmission are less common.
Vertical and sexual transmission is common in hepatitis ____
B
Following infection by hepatitis __?__, approximately 25% will develop acute acute clinical hepatitis. 15% will then clear the virus, but 85% will become chronically infected.
C
Which diarrhoea and vomiting virus is associated with point-source outbreaks (e.g. hospitals, cruise ships, military)?
Norovirus
True or false: Norovirus is a single-strand RNA virus
True
What is the dominant clinical symptom associated with norovirus?
Vomiting
The virus is transmitted in aerosolised vomit particles.
True or false: Rotavirus infects about 50% of children in the first 3 years of life.
False.
Rotavirus infects 80-100% in first 3 years of life.
True or false: Rotavirus is a major cause of infant mortality in the developing world?
True
Which pathogen is most commonly responsible for causing viral meningitis?
Enteroviruses
More than 50% of viral meningitis cases are enteroviruses.
True or false: Enteroviruses replicate in the gut and lead to GI symptoms.
False.
Enteroviruses replicate in the gut, but do not cause GI symptoms.
From the gut they migrate to the lymph nodes and then the blood (viraemia).
The following syndromes are common to which family of virus?
- Fever-rash syndromes (e.g. hand, foot and mouth)
- Common cold
- Meningitis
- Encephalitis
Enteroviruses
Which virus causes herpangina?
Coxsackie A (enterovirus)
Which virus causes pericarditis?
Coxsackie B (enterovirus)
By what medium is mumps transmitted?
Saliva and respiratory secretions.
Acute parotitis, orchitis and meningitis are all associated with which viral infection?
Mumps
In mumps, is acute parotitis unilateral or bilateral?
Can be both
20-30% of males with mumps will develop __1__.
This typically develops 4-5 days after __2__.
1) orchitis
2) parotitis
Which of these diseases is not associated with sensorineural deafness?
a) Mumps
b) Measles
c) Rubella
b) Measles
__?__ is highly infectious - the environment is still infectious 2 hours later.
Measles
What are the symptoms associated with primary measles infection?
Fever Coryza Cough Conjunctivitis Koplik's spots inside cheek Maculopapular rash
__1__ can occur 7-10 days after acute measles infection. It has a __2__ mortality rate and is __3__ mediated.
1) Acute post-infectious measles encephalitis
2) high mortality
3) immune mediated
__1__ can occur 7-10 years after primary measles infection. It is a progressive, degenerative and fatal disease of __2__
1) Subacute sclerosing panencephalitis (SSPE)
2) CNS
__?__ is also known as German measles.
Rubella
What symptoms are associated with primary postnatal rubella?
Mild illness with fever and maculopapular rash.
In 30% of adults: arthralgia and arthritis also occur
What symptoms are associated with congenital rubella?
Classic triad:
1) Bilateral cataracts
2) Sensorineural deafness
3) Microcephaly
Risk of malformation is highest in first 12 weeks of pregnancy.
Which is the more severe rubella syndrome?
Congenital rubella is more severe than primary postnatal rubella.
__?__ is also known as ‘slapped cheek syndrome’ or ‘Fifth disease’.
Parvovirus
How does parvovirus cause transient anaemia?
Parvovirus infects and destroys erythrocyte progenitor cells, causing transient anaemia.
What pathogen and symptoms are associated with erythema infectiosum?
Parvovirus
Fever, coryza, fiery red rash to cheeks
Parvovirus can cause dyspnoea, confusion and cardiac failure in which group of patients?
Those with high erythrocyte turnover
e.g. sickle cell, thalassemia
Parvovirus is most likely to lead to miscarriage in which stage of pregnancy?
a) last trimester
b) first 20 weeks
c) first 20 days
d) after 30 weeks
b) first 20 weeks
There is a 7-10% chance of foetal loss if mother contracts parvovirus in first 20 weeks.
What virus causes severe anaemia, oedema, ascites and heart failure in developing fetus?
Parvovirus
2-3% chance of developing hydrops fetalis:
severe fetal anaemia → oedema, ascites, heart failure
Which pathogen type contains no nucleic acid?
Prions
How do prions occur?
Gene mutation leads to changes in folding pattern of prion protein. If they become resistant to protease enzyme, the prion accumulates in cells and becomes pathogenic.
True or false: Abnormal prions can be inherited but never transmitted.
False. Prions can be inherited or transmitted.
Transmission usually occurs via consumption of infected meat products.
Which system is almost always affected by prions?
CNS
Prions lead to __?__ changes in brain tissue on histology.
spongiform
Do prion diseases have long or short incubation periods?
Long: up to 30 years
Sporadic Creutzfeldt-Jakob disease is rare. It is cause by a gene mutation and results in what symptoms?
Progressive ataxia
Depression
Dementia
Death
New variant CJD is linked to which prion disease?
Bovine spongiform encephalopathy (BSE)
nvCJD is associated with consumption of which product?
Infected beef.
Which drug is used in the treatment of giardiasis?
Metronidazole
What is the commonest cause of bacterial pneumonia?
Streptococcus pneumoniae
What is the commonest cause of bacterial meningitis and sepsis in neonates?
Streptococcus agalactiae (group B strep)
What disease is caused by treponema pallidum?
Syphilis
Which virus can trigger transient aplastic crisis in patient with haemoglobinopathies?
Parvovirus
What is the commonest cause of STIIs?
Staphylococcus Aureus
Which clostridium species is a classic cause of gas gangrene?
Clostridium perfringens
__?__ is a clinical syndrome produced by respiratory syncytial virus in children, characterised by wheeze and hypoxia
Bronchiolitis
Which organ is most commonly affected by hydatid cyst?
Liver
An infection of the heart valves often caused by viridans streptococci
Endocarditis
The type of histological change produced in the brain by prion disease
Spongiform
The cause of scalp ringworm
Tinea capitis
A sexually transmitted parasitic disease
Trichomoniasis
The virus that causes 80-90% of clinical infectious mononucleosis
Epstein Barr Virus
