Microbiology

Question 1

How do you treat an infective endocarditis?

Answer 1

If Strep IV Benzylpenicillin and Gentamycin
If Staph IV Flycloxacillin and gentamicin

For both supportive care and consider surgery such as valve replacement

Question 2

Which organism is the commonest cause of Community Aquired Pneumonia?

Answer 2

S. Pneumoniae

Question 3

What are the symptoms of Pneumonia?

Answer 3

Fever
Productive Cough
Pleuritic Chest Pain
SOB
Systemic Features such as hypotension

Question 4

What are the clinical signs of pneumonia?

Answer 4

Abnormal Vital Signs - increased respiratory rate

Unilateral signs of consolidation (dull percussion, reduced air entry on auscultation, crackles, wheeze)

Question 5

Which investigations should be performed when pneumonia is suspected?

Answer 5

Bloods - CRP, ABG to check for respiratory failure)
Chest Z Ray - Opacity/Consolidation of Affected Lobe
Sputum Sample and blood cultures

Question 6

How do you assess severity of CAP? Why are they important?

Answer 6

CURB 65: Confusion, urea (>7mmol/L), RR (>30/min), BP (<90mmHg), ≧ Age 65
Mild: 0-1 (outpatient)
Moderate: 2 (hospital admission)
Severe: 3+ (hospital admission + ?ICU)

Question 7

How is Community Acquired Pneumonia treated?

Answer 7

O2, analgesia (pleuritic pain), IV fluids

Mild: PO amoxicillin
Moderate: PO amoxicillin + clarithromycin
Severe: IV co-amoxiclav + clarithromycin

Question 8

Give two complications of pneumonia.

Answer 8

Empyema

Lung Abscess

Question 9

What is empyema?

Answer 9

Pleural empyema is a collection of pus in the pleural cavity caused by microorganisms, usually bacteria. Often it happens in the context of a pneumonia, injury, or chest surgery. It is one of various kinds of pleural effusion.

Question 10

How is hospital acquired pneumonia defined?

Answer 10

Defined as new onset cough w/ purelent sputum,
acquired 2 days or more after admission,
CXR showing consolidation

Question 11

What are the common causes of Hospital Acquired Pneumonia?

Answer 11

Same organisms as CAP (S. Pneumonia)

But also Staph Aureus (+ MRSA), Klebsiella Pneumoniae, Pseudomonas Aeruginosa

Question 12

Which antibiotic might you use if someone has a pneumonia caused by MRSA? Why?

Answer 12

Vancomycin - It is Broad Spectrum

Question 13

What is the diagnostic criteria for Infective Endocarditis? What is required for diagnosis?

Answer 13

Duke’s Criteria
Definite Infective Endocarditis: either 2 major and 1 minor criteria / 1 major and 3 minors / 5 minors
Possible IE: 1 major and 1 minor or 3 minors

Question 14

What are the Dukes Criteria?

Answer 14

BE FEVEER
Major:
Blood Cultures Positive more than 12 hours apart
Evidence of Endocardial Involvement (ECHO)

Minor:
Fever
Echo
Evidence from Microbiology (positive blood cultures not meeting major criteria)
Evidence from immunology (Roths Spots, Oslers Nodes, Glomerulonephritis)
Risk Groups (prosthetic valve, IVDU, Valvular Disease)

Question 15

How is a gram stain performed?

Answer 15

Fixation
Crystal Violet
Iodine Treatment
Discolourisation
Counter Stain with Safranin

Question 16

How are staphylococcus and streptococcus differentiated?

Answer 16

Staph - Clusters
Strep - Chains

Test to differentiate - Catalase Positive Staph, Catalase Neg Strep

Question 17

How are the different streptococci differentiated?

Answer 17

Haemolysis on Blood Agar:
Alpha Haemolytic (Greening around colonies)
Beta Haemolytic (Clearing around colonies)

Question 18

What can be done after haemolysis to further differentiate streptococci?

Answer 18

If alpha - Optochin test - if sensitive S. Pneumoniae, if resistant S. Viridans

If Beta - Lancefield groups - for example A = S. Pyogenes

Question 19

How are the different Staphylococci differentiated?

Answer 19

Coagulase Test - if positive S. Aureus, if negative commonly s. epidermidis

Question 20

What are the two main groups of gram positive bacilli?

Answer 20

Aerobic (e.g. listeria monocytogenes) and Anaerobic (e.g. clostridium difficile)

Question 21

Are Staphylococcus and Streptococcus gram positive or gram negative?

Answer 21

Gram Positive

Question 22

What are examples of Gram Negative cocci?

Answer 22

Neisseria (N. Gonorrhoea, N. Miningitidis)

Question 23

How do you differentiate between Gram Negative Bacilli?

Answer 23

MacConkey Plate
Lactose Fermenters (Pink): E. coli, Klebsiella Pneumoniae
Non Lactose Fermenters (Pale): Oxidase Test (If negative salmonella and shigella which are differentiated by XLD)

Question 24

Which antibiotics are Beta lactams? What does this mean?

Answer 24

Beta Lactams inhibit cell wall synthesis:
Penicillins such as benzylpenicillin, flucloxacillin, amoxicillin
Cephalosporins such as cqphalexin, cefuroxime, ceftazimide
Carbapenems such as imipenem, ertapenem

Question 25

Which antibiotic inhibits folate synthesis and therefore nucleic acid synthesis?

Answer 25

Trimethoprim

Question 26

Which antibiotic inhibits DNA gyrase and therefore nucleic acid synthesis?

Answer 26

Fluroquinolones

Question 27

Which antibiotic binds to RNA polymerase and is used to treat TB?

Answer 27

Rifampicin

Question 28

Which antibiotic breaks the DNA strand?

Answer 28

Metronidazole

Question 29

Which antibiotics inhibit protein synthesis?

Answer 29

Macrolides such as clarithromycin and erythromycin | Aminoglycosides such as gentamycin

Question 30

A patients sputum sample reveals a gram positive alpha haemolytic cocci, which is sensitive to optochin. What is the likely bacteria? Name a suitable antibiotic.

Answer 30

S. Pneumoniae | Amoxicillin

Question 31

When would a staphylococcus aureus be suspected instead of streptococcus pneumoniae in a patient with pneumonia?

Answer 31

If the patient has had an influenza viral infection

Question 32

How would you treat an E. coli or Klebsiella infection for Urinary Tract Infections?

Answer 32

Trimethoprim or Nitrofurantoin

Question 33

If a UTI spread upwards and a patient complained of a loin to groin pain, what pathology would you be most worried about?

Answer 33

Pyelonephritis

Question 34

Which antibiotic would you use to treat most cellulitis caused by s. progenies or s. aureus?

Answer 34

Flucloxacillin

Question 35

How would you treat suspected sepsis?

Answer 35

15L Oxygen fluids Broad Spectrum Antibiotics

Question 36

What are the symptoms of Sepsis?

Answer 36

``` SEPSIS Pneumonic Shivering, Fever or Very Cold Extreme Pain or General Discomfort ("Worst ever") Pale or Discoloured Skin Sleepy, Difficult to Wake Up, Confused "I Feel Like I Might Die" Short of Breat ```

Question 37

A Patient presented with food poisoning and a stool sample shows a gram negative bacilli, which is non-lactose fermenting and negative to oxidase test. What is the causative organism? How is it treated?

Answer 37

Salmonella spp. Supportive treatment Encourage fluid oral intake Anti-emetic (prochlorperazine) Anti-diarrhoeals (loperamide)

Question 38

What is the incubation period for Salmonella spp. ? Main causes?

Answer 38

12-48 hours | Poultry and Eggs

Question 39

What is the incubation period for Campylobacter spp. ? Main causes?

Answer 39

24-72 hours | Meat Products

Question 40

What is the incubation period or Bacillus Cereus? Main cause?

Answer 40

1 - 6 Hours | Rice

Question 41

A patient is suspected to have infective endocarditis. Name some other findings on examination that would support this diagnosis.

Answer 41

Roth Spots Splinter Haemorrhages Osler's Nodes Janeways Lesions

Question 42

Which heart valve is most commonly affected in Intra-venous drug users with Infective Endocarditis?

Answer 42

Tricuspid Valve

Question 43

What are the predisposing factors to infective endocarditis?

Answer 43

Prosthetic Heart Valve Recent Dental Work IVDEU

Question 44

How is S. Viridans treated?

Answer 44

Amoxicillin and Gentamicin

Question 45

What antibiotics would you give somebody with suspected C. difficile?

Answer 45

Oral Vancomycin or Metronidazole

Question 46

What is the treatment for Tuberculosis? Name a side-effect for each drug.

Answer 46

Rifampicin - Stains urine pink/orange Isoniazid - polyneuropathy Pyrazinamide - arthralgia/gout Ethambutol - optic neuritis

Question 47

Which stain would you use to determine the causative organism obtained from a sputum sample when diagnosing TB?

Answer 47

Ziehl-Neelson stain

Question 48

What is the causative organism of TB?

Answer 48

Mycobacterium Tuberculosis

Question 49

How would you treat Necrotising Fasciitis?

Answer 49

Surgical Debridement | Empirical Antibiotics: IV Benzylpenicillin and Clindamycin

Question 50

What are the common causes of Meningitis?

Answer 50

Neisseria Meningitides Strep Pneumoniae Group B Streptococcus

Question 51

How does meningitis present clinically?

Answer 51

Classic Triad Headache Stiff Neck and Photophobia Fever

Question 52

How is Meningitis treated?

Answer 52

Start antibiotics immediately when suspected Cefotaxime IV If in community - IV Benzylpenicillin

Question 53

How does encephalitis present clinically?

Answer 53

``` Confusion Decreased Consciousness Fever Headache Seizures ```

Question 54

What are the common causes of encephalitis?

Answer 54

Mostly viral - Herpes Simplex, Enteroviruses

Question 55

How is encephalitis treated?

Answer 55

IV Acyclovir

Question 56

How would you treat an upper urinary tract infection (loin to groin pain)?

Answer 56

Gentamicin and Cefuroxime, Co-amoxyclav

Question 57

Name some of the high risk groups for Tuberculosis.

Answer 57

``` Immunocompromised IVDU Homeless Alcoholics Foreign Born and those with parents from High Risk Countries Viral Hepatitis B/C ```

Question 58

What are the two types of TB (in terms of presentation) how are they treated differently?

Answer 58

Pulmonary and Extra-Pulmonary - Extra Pulmonary has to be treated for 12 months rather than 6

Question 59

What are the clinical features of Tuberculosis?

Answer 59

Weight Loss, Night Sweats, Malaise, Anorexia, Fever Pulmonary TB: productive cough + haemoptysis Lymph node TB: lymphadenopathy (non-tender) CNS TB: symptoms of meningism, raised ICP (headache, vomiting, altered behaviour, altered consciousness) Bone TB: osteomyelitis Abdominal TB: ascites… Miliary TB: due to spread of bacilli to multiple sites Other extra-pulmonary forms of TB: pleural, skin, pericardial, GU…

Question 60

Which investigations should be performed when suspecting TB?

Answer 60

Chest X Ray | Microbiological Samples - sputum samples and biopsy - Ziehl Neelson staining

Question 61

What are the risk factors for septic arthritis?

Answer 61

``` Prosthetic Joint (Rare in Native Joints() Diabetes Mellitus Immunosuppression Elderly Damaged Joints ```

Question 62

What are the causes of septic arthritis?

Answer 62

In Prosthetic Joints usually Gram positive Staphylococcus In young and sexually active usually gonococcal In children Staph Aureus

Question 63

Which investigations would you perform when you suspect septic arthritis?

Answer 63

Joint Aspirate and Culture

Question 64

How do you treat septic arthritis?

Answer 64

Aspirate for pain IV Antibiotics guided by culture - long course Surgical Joint Wahsout Reduce Inflammation Physiotherapy Temporarily stop immunosuppressive drugs but double prednisolone to prevent adrenal crisis

Question 65

What must cellulitis be differentiated from before treatment?

Answer 65

Deep Vein Thrombosis

Question 66

How is cellulitis treated?

Answer 66

Penicillin V and Flucloxacillin

Question 67

Which conditions will see an increase in neutrophils? (6)

Answer 67

Bacterial Infections Inflammation (eg MI, Polyarteritis nodosa) Myeloproliferative Disorders Drugs (Steroids) Disseminated Malignancy Stress (Surgery, trauma, burns, haemorrhage, seizure)

Question 68

Which conditions will see a decrease in neutrophils? (6)

Answer 68

``` Viral Infections Drugs: Post-chemotherapy, cytotoxic agents, carbimazole, sulfonamides Severe Sepsis Neutrophil Antibodies - SLE for example Hyperslpenism Bone Marrow Failure ```

Question 69

Which conditions will see an increase in lymphocytes? (3)

Answer 69

Acute Viral Infections Chronic Infections (TB, Hepatitis, Syphilis) Leukaemias and Lymphomas

Question 70

Which conditions will see an increase in eosinophils? (4)

Answer 70

Drug Reactions (eg with erythema multiforme) Allergies: asthma, atopy Parasitic Infections Skin Disease

Question 71

When will you see an increase in monocytes? (4)

Answer 71

In the aftermath of chemo or radiotherapy Chronic Infections (eg malaria, TB) Malignant Disease Myelodysplasia

Question 72

When will you see an increase in basophils?

Answer 72

IgE mediated hypersensitvity (Type 1) Myeloproliferative disease Viral Infections