Clinical Conditions Flashcards
What is cellulitis?
Inflammation of subcutaneous connective tissue.
How may a patient present with cellulitis?
Rubor and tumor of affected tissues. Low grade fever. High WBC and CRP. They may have an open wound, apparent on examination.
What are the main bacterial causes of cellulitis?
Staphylococcus Aureus or Streptococcus pyogenes (both gram positive)
How would a patient with cellulitis be treated?
Flucoxacillin (a Beta-lactam which is given via IV or orally)
How would you decide which antibiotic to use in a patient with cellulitis, which was caused by a staph infection?
Flucoxacillin (resistant to staphylococcal B-lactamase) and B-lactamse combinations (Co-amoxiclav with tazocin) can be used. If the staph is flucoxacillin resistant (e.g. MRSA), then we use glycopeptides (e.g. vancomycin).
For a patient with cellulitis, why might there be no blood culture growth after 48 hours?
Cellulitis is the bacterial infection of the subcutaneous connective tissue. At this point the infection has not disseminated into the blood (there will be no septicaemia).
What condition presents similarly to cellulitis in its early stages?
Necrotising fasciitis (an example of toxic shock syndrome).
How could you differentiate cellulitis and the other infection that initially mimics its presentation?
With necrotising fasciitis, the patient has severe, constant pain out of proportion to the physical signs. The inflammation will also have poorly-defined outer margins.
What is the most common cause of necrotising fascitiis?
Group A ß-haemolytic streptococci - normally Strep. pyogenes (gram positive)
On what basis are streptococci divided into Þ and ß-haemolytic?
They produce haemolysin which breaks down haemoglobin.
ß-haemolytic streps break down the haemoglobin completely. This means in an agar plate there are clear circles around the bacteria.
This is in contrast to Þ-haemolytic streps which only break down the haemoglobin partially. A green colour is left behind due to the presence of biliverdin (released due to the partial haem catabolism). Strep viridans is an Þ-haemolytic strep.
Patients with necrotising fasciitis can develop toxic shock syndrome. What should be done to treat these patients who go on to develop sepsis? (Hint: Sepsis Six)
High flow O2
Microscopy, cultures and antibiotic sensitivity
IV fluid resuscitation
Antibiotic of choice
Measure serum lactate
Measure urine output accurately
How would you treat necrotising fasciitis through surgical intervention?
A doctor must undertake an initial fasciotomy to assess deep tissues. Depending on the extent of the damage amputation may be necessary.
How would you treat necrotising fascitiis caused by a streptoccocal infection?
Beta-lactams & glycopeptides are active against streps (gram positive cocci). If the disease is toxin-mediated we should give high dose human immunoglobulin and give antibiotics that prevent protein synthesis e.g. clindamycin (a lincosamide, similar to macrolides)
The empiric treatment is tazocin + clindamycin
If group A streptococci identified benzylpenicillin replaces tazocin. High dose immunoglobulin is considered.
How can adenovirus be categorised?
It is a DNA non-enveloped virus.
What are some of the symptoms of an infection caused by adenovirus?
Sore throat with a blocked nose (nasal congestion) Fever. Coughs are common. Occasionally a patient may develop conjunctivitis (a red eye).
How is adenovirus usually spread?
Inhalation.
What is SIRS? How does this differ from Sepsis?
It is systemic inflammatory response syndrome (SIRS). It is diagnosed when a person has 2 or more of the following: Temperature >38°C; HR >90/min RR >20/min (or pCO2 <4.3kPa); WBC <4 or >12 x109/L
Sepsis is where there is SIRS AND there is a documented or presumed infection.
When does sepsis become severe sepsis? What is septic shock?
Severe sepsis is sepsis with organ dysfunction or hypoperfusion (hypotension = decreased urine output)
Septic shock is severe sepsis with persistently low BP DESPITE IV fluid resuscitation
How can sepsis lead to a reduction in blood pressure? (Hint: BP = TPR * CO)
There is a release of endotoxins which result in severe vasodilation. This serves to decrease TPR.
Why would a septic patient become tachycardic?
Decreased TPR means there will be a lower venous return. Thus venous pressure falls… HR increases (baroreceptor response to fall in BP). SV decreases however so CO stays the same.
E. Coli can be a causative pathogen of sepsis. Classify E. Coli.
Gram negative bacilli.
Pneumonia can result in SIRS. What organisms may cause this infection?
Classical: Streptococcus pneumoniae (gram positive cocci), Haemophilus influenzae (gram negative coccobacilli - very short rods which look like cocci), Moraxella Catarhallis (gram negative cocci). Atypical: Mycobacterium, Legionella pneumophila (gram negative bacilli), Chlamydia (gram negative, pneumoniae)
How would you treat pneumonia?
Specific treatments such as antibiotics are given.
If typical, amoxicillin (possibly with clavulanic acid to cover ß-lactamase inhibitors); if atypical, doxycycline or clarithromycin is often used.
Supportive treatment e.g. ventilation and fluids are given if required.
C. Diff. is an example of a hospital acquired infection. Classify C. Diff.
Gram positive bacilli. It is an opportunistic pathogen.
Infection will normally present as gastroenteritis.
