Microbiology/Infection Flashcards
Staphylococcus Aureus appears as what on a gram stain? What do we usually use to treat it?
Coagulase +ve ,Gram +ve, cocci.
Flucloxacillin.
Enterococcus appears as what on gram stain?
Gram +ve anaerobic cocci
Name some gram +ve rods
ABCDL (anthrax, bacillus, clostridium, diptheria, listeria)
Neisseria meningitidis and Neisseria gonorrhoea are what on gram stain?
Gram -ve diplococci
Name the most common gram -ve rod
E.coli
What antibiotics is pseudomonas often resistant to?
ampicillin, sulphonamides, tetracyclines, chloramphenicol and first- and second-generation cephalosporins.
Haemophilus influenza is what on gram stain?
Gram -ve coccobacilli
What is a +ve ASO titre indicative of?
recent strep infection (e.g., rheumatic fever)
Neutrophil count <0.5 x 10^9 AND fever >38.5 or 2 readings >38 is indicative of what? How should it be managed?
Neutropenic sepsis.
Mx: pip-taz
Parvovirus B19 causes what childhood associated illness? What are the sx?
Slapcheek (erythema infectiosum).
- prodrome: fever, coryza, diarrhoea
- followed by lace-like rash on the trunk and bright red rash on cheeks
How does parvovirus B19 present in adults?
Arthralgia and paraesthesia
Until what point is a child with slapped cheek (PB19) infective?
Until rash appears
What are the most common causes of otitis media?
Strep pneumonia, moraxella catarrhalis, haemophilus influenza.
When is the infectious period of measles? How is it transmitted? How does it present?
4-5 days after initial infection - spread by respiratory droplets.
- Koplik spots (white spots) on inside of cheek
- High fever
- Sore eyes (conjunctivitis)
- Coryza
- Rash appears 2-5 days after sx onset
What is a common complication of measles?
Otitis media.
Paromyxovirus causes which childhood associated illness? How does it present? How is it diagnosed? For how long should a patient be isolated?
Mumps.
- unilateral or bilateral parotitis
- fever
- potential sensorineural hearing loss
Measure salivary IgM mumps antibodies.
5 days post onset of parotid sx.
What is a known complication of mumps that happens to 20-23% males and can result in infertility in extreme cases?
Orchitis
Which complication of mumps causes N+V and a pain radiating from the epigastrium to the back?
Pancreatitis
What causes whooping cough? How does it gram stain? How does it present? How is it managed?
Bordetella pertussis - gram -ve coccobacilli
- flu-like sx
- barking cough (associated with vomiting, cyanosis, and syncope)
If sx persist past 21 days prescribe macrolide (clarithromycin).
Having whooping cough increases long-term risk of developing which respiratory pathology?
Bronchiectasis
Bacillus cereus gastroenteritis is associated with which food? How long is the onset?
Vomiting/diarrhoea associated with eating rice, onset is usually within 6 hours of consumption.
What is ‘traveller’s diarrhoea’? How long is the onset?
E.coli gastroenteritis (watery diarrhoea, abdominal cramps).
Onset within 12-48 hours.
What is Threadworm? How is it managed?
Itchy bottom worse at night (when the females lay eggs).
Parasitic infection of large bowel.
Mx: oral mebendazole and hygiene measures.
How does an Entamoeba Histolytica infection present? What is it associated with?
Parasitic amoebozoa infection causing:
- Bloody diarrhoea
- RUQ pain (liver abcess)
- swinging fevers and sweats
Associated with travel to endemic areas (India), MSM, and faecal oral transmission.
Bloody diarrhoea or constipation, abdo pain, rash of rose coloured spots, presenting within 24-48 hour incubation period after returning from Asia is what?
Salmonella typhi
How is Typhoid managed?
Azithromycin or ceftriaxone.
What is the most concerning complication of Typhoid? Why does this occur?
Intestinal perforation.
Due to necrosis of bowel wall after ulceration.
Diarrhoea (bloody or not) and abdo pain presenting within 48-72 hour incubation period is what?
Campylobacter
What is the most common cause of D+V in children?
Rotavirus: vomiting, diarrhoea, decreased oral intake, lethargy, etc.
D+V illness can lead to what type of acidosis?
Raised anion gap metabolic acidosis.
What is the most common cause of gas gangrene? How does this present? What type of kidney injury does this cause? Why?
Clostridium perfringens releases alpha and theta toxins - swelling, discolouration, blistering, subcutaneous emphysema around surgical site/incision. As well as pyrexia, tachycardia, hypotension.
Acute tubular necrosis: microvascular thrombosis and necrosis lead to localised gas production and rhabdomyolysis (ATN) leading to renal failure, RBC haemolysis, sepsis, and shock.
What is the most common cause of bacterial septic arthritis of prosthetics? What do you see if you aspirate?
Staph A (gram +ve cocci in grape-like clusters).
Aspirate = WCC >10000mm3 and neutrophils >90%, synovial fluid has a yellow appearance.
What most commonly caused HAP?
Pseudomonas or MRSA.
What is most commonly given for a Hospital Acquired Pneumonia?
Piperacillin-tazobactam
Someone presenting with muscle aches, headaches, non-bloody diarrhoea, fatigue and hepatosplenomegaly with a recent travel history should raise suspicions for what? What investigations should you perform?
Malaria - diagnose with thick (parasite density) and thin blood (species identification) films.
How might an infection of tropheryma whipplei present? How is it diagnosed and managed?
Systemic features: joint pain, diarrhoea, abdo pain, weight loss, etc often in male farmers.
Duodenal biopsy - periodic acid-schiff (PAS) positive macrophages. Managed with a year long course of co-trimoxazole.
What is the presentation of scarlet fever? How is it managed?
Strep throat - coryza, fever, cervical lymphadenopathy - followed by a rash on chest, abdo, and cheeks and strawberry tongue 12-48 hours later.
Manage with phenoxymethylpenicillin.
What is the most common cause of bacterial meningitis? How does this gram satin?
Neisseria meningitidis - gram -ve intracellular diplicocci
What will be seen on LP for bacterial meningitis?
Cloudy/purulent appearance, Increased protein, low glucose, increased white cells predominantly leukocytes.
What is 1st line for bacterial meningitis in primary care?
IM benpen and transfer to secondary care
What is first line for bacterial meningitis in secondary care?
IV ceftriaxone + amoxicillin (in age extremities only to cover for listeria too)
What is waterhouse-friedrichson syndrome? How does it present?
Adrenal failure (due to bleeding of glands) secondary to meningococcal sepsis and DIC.
HoTN, altered mental status, multi-organ dysfunction.
Often fatal.
What might be seen on LP for viral meningitis?
normal glucose, raised protein, white cells predominantly lymphocytes
Where are Hepatitis A, B, C, and E transmitted from?
A - faeco-oral route poor food hygiene (shellfish and water)
B - IVDU, sex workers, MSM
C - IV or nasal DUs, HIV infection, organs transplants and blood transfusions
E - endemic areas (East and South Asia),faeco-oral transmission e.g., contaminated water
What causes typhoid fever? What are the sx?
Salmonella typhia:
- headache,
- fatigue,
- aches/pains,
- cough,
- maculopapular ‘rose spots’ rash that blanches under pressure,
- GIT sx,
- hepatosplenomegaly
How do you diagnose typhoid fever? How do you manage it? What is a common complication?
Bone marrow/blood/stool culture to detect bacteria OR widal test (to check for antibodies).
IV ceftriaxone - cipro/azithromycin if resistant.
Cx: GI ulceration and perforation.
What causes Lyme disease? How is it transmitted?
Borreliosis, transmitted through ixodes tick.
What are the sx of Lyme disease? How is it managed? What is the complication on the nervous system?
- Erythema migrans
- fever
- myalgia
2-3 weeks of doxycycline.
Neuroborreliosis - pain and weakness due to affect on PNS, can occur 4-6 weeks later.
What is the classic presentation of schistosomiasis? How is it managed?
- Swimmer’s itch
- Eosinophilia
- Uticaria
- hepatosplenomegaly
- Systemic features (2-8 weeks after infection, known as Katameya fever)
Mx: praziquantel - if developed into katameya fever then give in combo with corticosteroids
What is brucellosis? What are the symptoms? How is it transmitted? How is it managed?
Gram -ve aerobic, intracellular bacillus.
Unspecific sx:
- fever
- myalgia
- sweats
- headaches
- fatigue
Transmitted through unpasteurised milk and livestock to humans.
Mx: dual therapy doxycycline and streptomycin for 2-3 weeks.
What causes scarlet fever? How does it present? How is it managed?
group A strep, presents with flu-like sx followed by sandpaper rash and strawberry tongue 48 hours after prodrome.
Manage with phenoxymethylpenicillin.
What causes glandular fever?
EBV
What are the most common culprits for neutropenic sepsis?
gram -ve bowel infections and gram +ve line infections
In who might you see a fungal chest infection? What is usually the culprit? How do you diagnose this?
Immunocompromised pts who are neutropenic for a long period of time (e.g., AML pts) may present with signs of a chest infection but no signs of CXR and are unresponsive to abx.
In this case think aspergillus
Needs high res CT chest.
Which viruses pose an increased risk to the immunocompromised?
- shingles (can be Multidermatomal)
- purulent varicella
- CMV (can be an issue with stem cell transplants)
- EBV reactivation
- hepatitis
What pneumonia affects immunocompromised only? What sign is seen on CXR?
PCP - batwing hilar shading.
Splenectomy pts are at increased risk when it comes to what type of organisms?
Encapsulated e.g., haemophilus and Neisseria
What virus causes chicken pox/shingles? How does it present?
Varicella-zoster (HHV3) - febrile syndrome with maculopapular rash starting on head and trunk which spreads, papules become vesicles and then crust.
What virus causes cold sores?
HSV1
What is the underlying cause of eczema Herpeticum? How does it present? How is it managed?
HSV infection of eczema causing monomorphic blisters and erosions alongside general malaise.
Mx: acyclovir
What is Impetigo most commonly caused by? What is classically seen?
Staph aureus - golden crusting
At what point is someone with impetigo no longer infectious? How is it managed?
Once wounds have crusted or 48 hours after commencing abx.
Non-bullous: topical fusidic acid
Bullous: systemic abx
What is the incubation period for Hep A? How do you manage it? How long does it take to resolve?
2-6 week incubation period.
Supportive management.
6 months.
What is Black water fever?
Malaria leading to intravascular haemolysis and AKI causing passage of dark coloured urine.
What causes Leprosy? How is it spread?
Mycobacterium leprae - spread in endemic countries (India, Indonesia, Brazil) by animals (squirrels, armadillos) and through respiratory route/nasal discharge.
What are the two types of leprosy?
- Multibacillary (lepromatous) - poor Th1 response causes more manifestations
- Paucibacillary (tuberculoid) - robust Th1 response means milder sx
What are the symptoms of Leprosy?
- Skin: Coppery, hypopigmented lesions (<5 for paucibacillary and >5 in multibacillary)
- Face: Nasal destruction and ear swellings
- Peripheral neuropathy
- Thickening of nerves (medial, radial, ulnar, common peroneal, posterior tibial, greater auricular)
How does EBV present? How can we test for it?
- Sore throat, exudative tonsils, fatigue, lymphadenopathy, hepatosplenomegaly.
- Monospot test: +ve heterophile antibodies in 2nd week of illness (may have false -ve in the 1st week). Can also do EBV serology SECOND line if monospot is negative but there is high clinical suspicion or if pt is immunocompromised and doesn’t produce abs.
What is 1st line for Coagulase negative staphylococcus?
Vancomycin
What is the management of Malaria?
Artemisinin and lumefantrine PO for uncomplicated malaria. IV Artesunate for more severe cases (very high fever)
For how long should pts with EBV be told to avoid heavy lifting./contact sports? Why?
3 weeks due to risk of splenic rupture.
If MRSA is identified on the skin of pre-op patient how would you manage this?
- Mupirocin nasal spray
- Chlorhexidine wash
How do you manage infections of MRSA?
Vancomycin
A high risk individual exposed to chicken pox with no previous exposure or vaccine should be offered what?
7 days of oral acyclovir
