Medicine Specialties B - Microbiology man and AB man summary

Question 1

What are the causative organisms of bacterial meningitis in all age groups?

Answer 1

Neonates - Group B strep, E.coli, Listeria Children - H. Influenza 10-21 - Neissiera meningitidis (meningococcal meningitis) 21+ - Streptococus pneumonia (pneumococcal meningitidis) > Neissiera 60+ - Pneumococcal > Listeria

Question 2

What are common viral causes of meningitis?

Answer 2

Enteroviruses are the commonest viral cause Eg - Echo virus, cocksackie virus Herpes simplex virus 2 and VZV

Question 3

What is the commonest cause of encephalitis? What are the features of encephalitis?

Answer 3

HSV type 1 is the most common cause Features include an insidious onset, stupor and confusion, fever and difficulty speaking

Question 4

What is given as empirical treatment for meningitis? When is dexamethasone continued?

Answer 4

IV ceftriaxone (2g bd) + IV Dexamethasone with or before first antibitoic dose for max of 4 days - only continue if pneumococcal + Amoxicillin (ampicillin) 2g 4 hourly if >60, neonate or immunocompromised

Question 5

What is given for penicillin/cephalosporin resistant pneumococcos of for patients who have recently travelled who present with meningitis?

Answer 5

IV ceftriaxone is given and IV vancomycin is added - vanc not given alone due to concerns about CSF penetration (can also use IV ceftriaxone + rifampicin IV/PO)

Question 6

What is the most common cause of fungal meningitis? What group of patients is this seen in?

Answer 6

Cryptococcus neoformans Usually associated with patients who are immunocompromised eg HIV/AIDS

Question 7

How is fungal meningitis due to cryptococcus neoformans treated?

Answer 7

CSF India Ink stain to diagnose Treat with amphotericin B + 5-flucytosine Follow up with fluconazole

Question 8

What type of bacteria is * Step pneumonia * E.coli * Group B strep * Listeria monocytogenase * Neisseria * H.influenza

Answer 8

Strep pneumonia - gram positive cocci (alpha haemolytic) Group B strep - gram positive cocci (beta haemolytic) Listeria - Gram positive bacilli E.coli - coliform - gram negative bacilli Neisseria - Gram negative (diplo)cocci H.Influenza - gram negative bacilli

Question 9

What initial tests are ordered in patients with suspected meningitis?

Answer 9

Blood cultures, LFTs, clotting screen and glucose Throat swab and bacterial culture Lumbar puncture to analyse the CSF

Question 10

What features would cause you not to order a lumbar puncture?

Answer 10

Skin infection near site of LP Signs of severe or rapidly evolving rash Respiratory or cardiac comrpomise GCS less than or equal to 12 Papilloedema - sign of raised ICP Continuous or uncontrollable seizures

Question 11

Why are papilloedema, deceased consciousness, focal neurological signs all contraindications to a LP in meningitis?

Answer 11

ALL ARE SIGNS OF A SPACE OCCUPYING LESION (SOL) As the SOL grows, ICP rises. When LP is performed in these patients, a low-pressure shunt is formed at the site of LP where CSF can escape. As the CSF pressure drops in the spinal column, CSF and brain mass may then shift towards the low-pressure outlet (the LP site). This may lead to either trans-tentorial or uncal herniation and acute neurological deterioration.

Question 12

What should be performed prior to a lumbar puncture in patients with suspected space occupying lesions?

Answer 12

CT scan should be carried out

Question 13

What colour is the CSF in bacterial vs viral meningitis?

Answer 13

Bacterial - cloudy Vital - clear

Question 14

What are the normal CSF values for WCC, RCC, protein and glucose?

Answer 14

WCC - <5/ mm3 RCC - 0-5/ mm3 Protein - 150-450 mg/L Glucose - 60-70% of Blood glucose concentration

Question 15

Normal CSF values WCC - RCC - 0-5/ mm3 Protein - 150-450 mg/L Glucose - 60-70% of Blood glucose concentration What are the values in bacterial and viral meningitis?

Answer 15

Bacterial Predominantly polymporphs on gram stain (10^1 - 10^4), high protein, low glucose, gram stain positive for bacteria Viral Predominantly lymphocytes on gram stain (10^1-10^3), normal or slghtly raised protein, glucose normal, gram stain negative for bacteria

Question 16

What organisms usually cause a brain abscess?

Answer 16

Streptococcus - usually strep milleri Also bacteriodes spp (anaerobic organisms) Staph aureus

Question 17

How are brain abscesses treated? What is empirical treatment?

Answer 17

Diagnosed via CT - ring enhancing lesions tx - IV ceftriaxone and IV metronidazole Add fluclox is suspecting staph aureus

Question 18

How is the severity of community acquired pneumonia assessed?

Answer 18

Confusion new - MSQ /= 7 Resp rate>/=30/min Blood pressure - <90 systolic or =60 diastolic 65 - age Mild/Mod = 0-2 Severe = 3-5

Question 19

What organisms are potentially causative for CAP (both mild/mod and severe)

Answer 19

Mild/mod - strep pneumonia (gram positive cocci) or haemohpilus influenza (gram negative bacilli) Severe - as above or coliforms and atypicals eg legionella, mycoplasma pneumonia, chlamydia, coxiella

Question 20

What is given for mild/mod CAP? What if pen allergic? What is the duration?

Answer 20

Mild/moderate CAP - Amoxicillin IV/PO If pen allergic - Doxycycline Oral or Clarithromycin if NBM Duration = 5 days

Question 21

What is given for severe CAP? What if pen allergic? What is the duration?

Answer 21

IV Co-amoxiclav + Doxycycline PO OR IV clairthromycin if NBM If pen allergic - IV Levofloxacin monotherapy Duration =7 days

Question 22

What should be watched for when using clarithromycin?

Answer 22

Clarithromycin Watch for prolonged QT syndrome and for interactions ie statins (could cause rhabdomyolysis - both act on CytP450 pathway)

Question 23

What organisms are causative of HAP? What is the treatment for non-severe HAP? (and if pen allergic) Duration?

Answer 23

Organisms for HAP Pneumococcus, H.influenza and coliforms, legonalla can be hospital acquired Non severe PO Amoxicillin If pen allergic then Doxycycline Duration - 5 days

Question 24

What is the treatment for severe HAP? (and if pen allergic) Duration?

Answer 24

IV amox + gent If pen allergic IV co-trimoxazole + gent Duration - 7 days

Question 25

What are the most common causes of UTIs?

Answer 25

Coliforms - gram negative bacilli * E.coli * Klebsiella * Proteus Enterococci - gram positive cocci Pseudomonas - aerobic gram negative bacilli

Question 26

How are uncomplicated female UTI treated? How are uncomplicated male UTI treated? How many days?

Answer 26

Female Nitrofurantoin or trimethoprim - 3days Male Nitrofurantoin or trimethoprim - 7days Nitrofurantoin only works in bladder

Question 27

What is the treatment for complicated UTI?

Answer 27

IV amox + gentamicin Should cover the coliforms and gram positive organisms (ie enterococcoi and gram neative bacilli) 7 days

Question 28

Some bacteria produce beta lactamase which can break down antibtioic B-lactam ring deactivating the antibitoic antimicrobial properties Which antibitoics contain a B-Lactamse inhibitor?

Answer 28

Co-amoxiclav, tazocin (piperacillin + tazobactam) and many others

Question 29

Certain bacteria are extended spectrum beta lactamases - they are resitant to beta lactam inhibitor producing antibitoics What can be given at this stage?

Answer 29

Drugs such as temocillin or carbapenems - very broad spectrum

Question 30

What are the next step after ESBL bacteria?

Answer 30

Carbapenem resistant enterobacteriaceae (CRE) or carbapenemase producing enterobacteriaceae (CPE) are the next step in antibiotic resistant bugs SUPERBGUS

Question 31

What is the difference between acute and subacute endocarditis? * Onset? * Symptoms? * Were the heart valves already damaged or not?

Answer 31

ACUTE BACTERIAL ENDOCARDITIS usually occurs over days to weeks and begins suddenly with a high fever, fast heart rate and rapid/extensive heart valve damage - IN A PATIENT WITH PREVIOUSLY NORMAL HEART VALVES SUBACUTE BACTERIAL ENDOCARDITIS usually occurs over weeks to months - mild fever, moderate tachycardia, weight loss, fatigue (shows gradual presentation) - PATIENT WITH ALREADY PRESENT VALVULAR PROBLEMS

Question 32

Name some signs of endocarditis? - usually seen in subacute BE presentations

Answer 32

Osler’s nodes - tips of toes and fingers, painful nodules Janeway lesions - palms of hands and soles of feet, painless Splinter haemorrhages - vertical red streaks in finger nails Roth spots - retinal haemorrhages with pale centers on fundoscopy

Question 33

Why does the treatment of endocarditis involve high dose, IV treatment, for prolonged doses and using bactericidal antibiotics?

Answer 33

Endocarditis is a deep seated infection and therefore high dose IV treatment is required Also it is given in high dose to penetrate vegetations, eliminate bacteria and to reduce the risk of septic emboli Bactericidal antibiotics are given to kill rather than slow bacteria

Question 34

How long are the high dose, prolonged duration course of bactericidal antibiotics given for in endocarditis?

Answer 34

Endocarditis treatment is prescribed for 4-6 weeks to ensure elimination of the bacteria

Question 35

What is the most common cause of native valve acute endocarditis? What is the most common cause of native valve subactue endocarditis?

Answer 35

The most common cause of native valve acute endocarditis is staph aureus (coagulase positive staph) The most common cause of native valve subacute staph aureus is streptococcus viridans - as well as enterocci and other streptococci causing subacute BE

Question 36

Meticulous aseptic technique is required when taking blood cultures, to reduce the risk of contamination with skin commensals, which can lead to misdiagnosis. How are cultures taken and when are antibiotics started: * In patients with suspected infective endocarditis and severe sepsis or septic shock at the time of presentation? * In patients with an indolent (also known as chronic or subacute) presentation?

Answer 36

In patients with suspected bacterial endocarditis and severe sepsis - 2 optimally filled sets of blood cultures are taken within one hour prior to commencing empirical antibiotic therapy In patients with indolent (aka chronic or subacute) presentation, 3 optimally filled sets of blood cultures are taken >/= 6 hours apart prior to commencing empirical antibiotic therapy

Question 37

How are cultures taken and when are antibiotics started: In patients with suspected infective endocarditis and severe sepsis or septic shock at the time of presentation? What is the empirical therapy for patients presenting with native valve acute endocarditis?

Answer 37

In patients presenting with suspected BE and severe sepsis or septic shock - 2 sets of blood cultures are taken within one hour prior to starting antibiotic therapy Empirical antibiotics of choice for native valve acute BE - * Needs to provide cover for main causative organism, staph aureus * Flucloxacillin IV is treatment of choice

Question 38

How are cultures taken and when are antibiotics started: In patients with an indolent (also known as chronic or subacute) presentation? What is the empirical therapy for patients presenting with native valve indolent endocarditis?

Answer 38

In patients with an indolent presentation, 3 sets of optimally filled cultures are taken >/= 6 hours apart prior to commencing antibiotics therapy Empirical therapy for patients presenting with native valve subacute endocarditis - IV amoxicillin and Gentamicin

Question 39

What are the causative organsims involved in prosthetic valve endocarditis?

Answer 39

Staph auerus, staph epidermis usually

Question 40

What is the empirical treatment for patients with prosthetic valve endocarditis and native valve if MRSA suspected?

Answer 40

Treatment would be Vancomycin and gentamicin IV, rifampicin PO Usually valve replacement would be required

Question 41

What is the treatment of choice for * Native valve acute endocarditis empirical? * Native valve subacute endocarditis empirical? * Prosthetic valve or native valve if MRSA suspected? * Staph aurues? * Enterococcus? * Staph epidermis?

Answer 41

* Native valve acute endocarditis empirical - IV Fluclox (usually staph aureus) * Native valve subacute endocarditis empirical - IV Amoxicillin and Gent (usually strep viridans) * Prosthetic valve or native valve if MRSA suspected - IV Vanc, Gent and PO Rifampicin (Usually staph aureus or epidermis) * Staph aurues - IV fluclox * Enterococcus - Amox, (Vanc -pen allergic) and Gentamicin IV * Staph epidermis - IV Vanc, Gent and Rifampicin PO

Question 42

Which bacteria are implicated in cellulitis? What is the most common bacterial cause of a diabetic foot infection?

Answer 42

Cellulitis - Staph aureus -most common Group A strep or other beta-haemolytic strep Diabetic foot infection - usually staph aureus infection

Question 43

What is the two different alpha-haemolytic strep? Name two different types of beta-haemolytic strep?

Answer 43

Alpha-haemolytic strep - Streptocccus pneumonia - surface of skin and inside of throat Streptococcus viridans - found usually in mouth Beta haemolytic strep Group A strep - strep pyogenes Group B strep - strep agalactiae Group C - H also exist

Question 44

What is the initial treatment for a cellulitis infection? (if mild and if sepsis)

Answer 44

Initial treatment is Oral flucloxacillin for 7 days If mild then IV flucloxacillin for 7 days

Question 45

If the patient with cellulitis (mild) is pen allergic or not resolving to fluclox, what can be given? If the patient with cellulitis (sepsis) is pen allergic or not resolving to fluclox, what can be given?

Answer 45

If the mild cellulitis patient is pen allergic or not resolving - Doxcycline Oral can be given for 7 days (will cover MRSA) If the severe sepsis patient is pen allergic or not resolving - switch to Vancomycin IV

Question 46

What has to be monitored when patient is taking vancomycin? Why isnt it given first line? If the monitoring of the vanc is outwith the target, what can be switched to and what is monitored then?

Answer 46

Vancomycin has to be within a therapeutic range - greater increase of nephrotoxicity if above this range If outwith the target range, can switch to Daptomycin Need to monitor CK when takingg this