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year 3 > Infection > Flashcards

Infection Flashcards

1
Q

What are the clinical criteria to define gastroenteritis?

A

3 or more loose stools in 24 hrs plus at least one of: fever vomiting pain blood/mucus stools

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2
Q

What are the clinical features of dysentery?

A

LARGE bowel inflammation (shigella or amoeba dysentery)

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3
Q

What are the clinical features of diarrhoea?

A

increased fluidity and frequency of stool

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4
Q

Which organism is the most common cause of gastroenteritis leading to hospital admission?

A

Salmonella

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5
Q

Which organism is the most common cause of gastroenteritis?

A

Campylobacter infection (chicken)

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6
Q

Which organism is the most common cause of travellers diarrhoea?

A

enterotoxigenic E.coli. cannot be differentiated in the lab

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7
Q

List the defences (by body and hygiene practices) that prevent developing gastroenteritis?

A

Age

hygiene

gastric acid

gut motility

normal flora

gut immunity

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8
Q

What are the two main ‘types’ of diarrhoea

A

inflammatory non inflammatory

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9
Q

What are the main features of inflammatory diarrhoea?

A

Usually Bacterial infection e.g. shigella dysentery

• pain and fever,

bloody stools (tissue damage and destruction due to immune response)

  • typically caused by bacteria and parasites
  • fluid replacement is still main treatment
  • antibiotics CAN be used
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10
Q

What are the main features of non inflammatory diarrhoea?

A

Usually caused by toxins e.g. vibrio cholerae toxin

  • cholera toxin increases cAMP levels and Cl- secretion (water follows)
  • frequent watery stools with little abdo pain
  • rehydration mainstay of therapy
  • vast volumes of fluid loss
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11
Q

What are the two most common organisms causing gastroenteritis?

A

campylobacter and salmonella

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12
Q

What do you need to cover in assessment of patient with suspected gastroenteritis ?

A

Symptoms - duration diarrhoea, frequency and “quality” of stool, other symptoms

  • Risk - food, occupation, travel, antimicrobials, contacts, institution
  • Examination of hydration, SIRS: - Pulse, fever, skin turgor, urine flow, patient appearance, muscle cramps
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13
Q

Which investigations are needed in gastroenteritis?

A

Stool and blood culture

renal function

blood count (haemolysis)

sigmoidoscopy X-Ray

serology

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14
Q

What is haemolytic uraemic syndrome

A

characterised by a triad of

1) haemolytic anaemia (anaemia caused by destruction of red blood cells)
2) acute kidney failure (uraemia)
3) and a low platelet count (thrombocytopaenia) It predominantly, but not exclusively, affects children

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15
Q

Which medicines increase the risk of gastroenteritis?

A

omeprazole ranitidine

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16
Q

List the differential diagnosis for gastroenteritis?

A

Over 2 week history = inflammatory bowel disease

Spurious diarrhoea (overflow diarrhoea)

Carcinoma (bowel obstruction)

Diarrhoea and fever can occur with infection outside the gut. IE in pneumonia.

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17
Q

What is the treatment of gastroenteritis?

A

RAFT Rehydration

Antimicrobials

Fasting

Treatment of complications

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18
Q

What are the clinical features of salmonella infection?

A

Salmonella (non-typhoidal) - Symptom onset usually <48h after exposure and diarrhoea usually lasts <10 days - <5% have positive blood cultures - Extra-intestinal manifestations uncommon but potentially fatal consensus view on antibiotic treatment - 20% have persistently positive stools at 20/52

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19
Q

What disease is a person at risk of developing after they have had salmonella infection?

A
  • 20/75 (27%) have Irritable Bowel Syndrome symptoms at 6 months
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20
Q

What are the clinical features of campylobacter infection?

A

C jejuni principle pathogen - Incubation up to 7 days - Infection clears within 3 weeks - Severe abdo pain +/- colitic picture - Rarely invasive (immunocompromised) - <1%

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21
Q

What would a positive blood culture indicate in someone with campylobacter infection?

A

It is rarely invasive, so check for compromised immune system HIV etc.

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22
Q

Which diseases is a person at risk of developing after they have had a campylobacter infection?

A

Guillain-Barré syndrome or reactive arthritis

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23
Q

What are the clinical features of e.coli 0157?

A

Ecoli stays in the gut but the TOXIN gets into the blood - Enterohaemorrhagic E. coli - Cattle reservoir - Excretion over three weeks after symptoms - Increasing incidence - Produce a shiga-like toxin (SLT) - 5-9 days between onset of diarrhoea and HUS - HUS largely (not exclusively) a complication in children and elderly

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24
Q

Is there a cholera vaccine?

A

Yes

25
Q

What does shigella cause?

A

disease in children (nurseries) and in travellers. Seizures and HUS may complicate

26
Q

Do antibiotics shorten the length of travellers diarrhoea?

A

Yes Can be used in Severe community-acquired gastro-enteritis or compromised patient

27
Q

What is the most common viral cause of gastroenteritis? What are its characteristics?

A

Rotavirus >800,000 deaths in children under 5y - Faecal-oral transmission - Infects mature enterocytes of villous body and tip (not crypts) with cell death and lactose intolerance.

28
Q

What are the 3 parasites that can cause gastroenteritis? What are the features of each?

A

Cryptosporidiosis - Water-borne outbreaks - 3-6% of diarrhoea in developed countries - Cattle the principal reservoir - Self-limiting, but often protracted illness, in non-compromised patients.

  • Giardia - present in surface water - asymptomatic cyst carriers - treatment by metronidazole, tinidazole
  • Entamoeba histolytica - Microscopy only 50% sensitive - May mimic ulcerative colitis - Treat symptomatic disease with 10/7 metronidazole and furamide for cyst carriage (asympto-matic disease)
29
Q

Which antibiotics increase the risk of CDiff infection?

A

AVOID 4 Cs of antibiotics clindamycin, cephalosporins, co-amoxiclav and ciprofloxacin (clarithromycin)

30
Q

What percentage of patients given antimicrobials get diarrhoea?

A

5-10%

31
Q

What are the main toxins in CDiff infection?

A

toxins A (enterotoxin) and B (cytotoxin)

32
Q

What is the treatment for C.Diff infection?

A

metronidazole (up to 6% resistant, poor stool concn.) - vancomycin (cost and drug resistance in gut flora) - teicoplanin/fusidic acid/ cholestyramine - surgery

33
Q

What is the name of the stool test you need to order for parasites?

A

P C O (parasites, cysts and ova)

34
Q

List risk factors for sepsis

A

The very young (under 1 year) and older people (over 75 years) or very frail people. • Recent trauma or surgery or invasive procedure (within the last 6 weeks). • Impaired immunity due to illness (for example, diabetes) or drugs (for example, people receiving long term steroids, chemotherapy or immunosuppressants). • Indwelling lines, catheters, intravenous drug misusers, any breach of skin integrity (for example, any cuts, burns, blisters or skin infections). If at risk of neutropenic sepsis – refer to secondary or tertiary care Additional risk factors for women who are pregnant or who have been pregnant, given birth, had a termination or miscarriage within the past 6 weeks: • gestational diabetes, diabetes or other comorbidities • needed invasive procedure such as caesarean section, forceps delivery, removal of retained products of conception • prolonged rupture of membranes • close contact with someone with group A streptococcal infection • continued vaginal bleeding or an offensive vaginal discharge

35
Q

What are the important warning signs for sepsis?

A

Behaviour: objective evidence of new altered mental state · Heart rate: more than 130 beats per minute · Respiratory rate: ▫ 25 breaths per minute or more OR ▫ new need for 40% oxygen or more to maintain saturation more than 92% (or more than 88% in known chronic obstructive pulmonary disease) · Systolic blood pressure: ▫ 90 mmHg or less OR ▫ more than 40 mmHg below normal · Not passed urine in previous 18 hours, or for catheterised patients passed less than 0.5 ml/kg of urine per hour · Mottled or ashen appearance · Cyanosis of skin, lips or tongue Non-blanching rash of skin

36
Q

Which tests should be carried out for sepsis?

A

blood gas for glucose and lactate blood culture full blood count C-reactive protein urea and electrolytes creatinine clotting screen

37
Q

Which blood test would indicate that a person is in sepsis and high risk? What value?

A

Lactate over 2

38
Q

List the ‘sepsis 6’ to be carried out immediately if sepsis is suspected

A

Take 3 Blood cultures (x 2 sets) Blood lactate Measure urine output Give 3 Oxygen aim sats 94-98% IV Antibiotics IV fluid challenge or 2 A 2 B 2 C Air enriched with O2 Antibiotics Blood culture Blood gas with lactate Catheter Crystaloid bolus

39
Q

What score is used for pneumonia? What does it stand for?

A

CURB 65 Confusion (newly disorientated in time, place, person) Urea raised over 7mmol/L RR over 30 Blood pressure systolic less than 90 mmHg and diastolic less than 60 mmHg 65 - aged 65 or more score 0-1 treat at home score 2 or more - treat in hospital

40
Q

What is the recommended daily fluid bolus for a patient that is 70 kg?

A

2 litres over the space of 24 hours

41
Q

What are three key things to ask about in a history when assessing for sepsis?

A

travel

occupation

hospitalisation

42
Q

When is it classed as oliguria?

A

urine out put less than 0.5ml/kg/hr

43
Q

In sepsis, what are the two different mediators and their effects?

A
  • Pro-inflammatory mediators – causes inflammatory response that characterises sepsis
  • Compensatory anti-inflammatory reaction – can cause immunoparalysis
  • Pro-inflammatory mediators
  • Promote endothelial cell – leukocyte adhesion
  • Release of arachidonic acid metabolites
  • Complement activation
  • Vasodilatation of blood vessels by NO
  • Increase coagulation by release of tissue factors and membrane coagulants
  • Cause hyperthermia
  • Anti-inflammatory mediators
  • Inhibit TNF alpha
  • Augment acute phase reaction
  • Inhibit activation of coagulation system
  • Provide negative feedback mechanisms to pro-inflammatory mediators
44
Q

For each hour in delaying antibiotics in septic shock, how much does mortality increase by?

A

7.6 %

45
Q

What does SIRS mean?

A

systemic inflammatory response syndrome

(ie dont have to have infection to have SIRS)

46
Q

What criteria is used to assess whether a patient is at high risk of mortality with sepsis?

What is contained in it?

What score is considered high risk?

A

qSOFA

BP systolic under 100mmHg

altered mental status

RR over 22

a score of over 2 is considered high risk (think escalation to HDU)

47
Q

What is the difference between septic shock and sepsis?

A

Sepsis is defined as life-threatening organ dysfunction caused by dysregulated host response to infection

  • Organ dysfunction can be identified as an acute change in total SOFA score >2 points consequent to the infection
  • SOFA score >2 reflects an overall mortality risk of approximately 10% in a general hospital population with suspected infection

Septic shock can be identified with a clinical construct of sepsis with persisting hypotension requiring vasopressors to maintain MAP >65mmHg and having a serum lactate of >2mmol/l despite adequate volume resuscitation

•Patients with septic shock have a hospital mortality of 40%

48
Q

Re HIV

List ways HIV can be spread

A

sexual

vertical

contaminated blood products

organ transplant

share needles during injecting drug misuse

49
Q

Which cells does HIV attack?

Which surface glycoprotein on the virus attaches to the host?

What is a normal CD4 count?

A

CD4 T helper cells (lymphocytes)

gp 120

above 500

50
Q

What does the CD4 count need to fall to in order for the infected person with HIV to become symptomatic?

Where are CD4 receptors present in the body?

A

Less than 200

MAINLY in T helper cells but also present in skin and brain (therefore get disease in these places)

51
Q

Which factor is of interest in HIV which helps the binding of HIV to CD4?

A

CCR5

Patients with a mutation of both CCR-5 alleles appear to be very resistant to HIV infection. HIV-infected patients who have a single CCR-5 allele mutant appear to have a slower rate of HIV disease progression compared to others.

52
Q

What is the definition of a healthcare acquired infection?

A

an infection in an inpatient setting that occurs 48 hours after admission OR within 48 hours of discharge

53
Q

What is the difference between colonisation and infection?

A

colonisation: where there is bacteria on the skin but cause no disease

infection; bacteria that cause disease (e.g. fever)

54
Q

List the factors that can increase the risk of hospita acquired infections

both from host and microbial

A

¨Devices: PVC, CVC, Urinary catheter, Ventilation

¨Antibiotics

¨Break in skin surface

¨Foreign body

¨Immunosuppression

¨?Gastric acid suppression

¨Age extremes

¨Overcrowding

¨lack of hand hygeine

microbial

Increased:

§Resistance

§Virulence

§Transmissability

§Increased survival ability

§Ability to evade host defences

55
Q

What are the main modes of spread for hospital acquired bacteria and list a microbe for each

A

¨Direct contact

e.g. Staphylococcus aureus, coliforms

¨Respiratory/Droplet

e.g. Neisseria meningitidis, Mycobacteria tuberculosis

¨Faecal-Oral

e.g. Clostridium difficile, Salmonella sp.

¨Penetrating Injury

e.g. Group A streptococcus, Bloodborne viruses

56
Q

List the chain of infection

A

¨Source of microbe (endogenous or exogenous)

¨Transmission

¨

¨Host

57
Q

What is the difference between cleaning, sterilisation and disinfection?

A

¨cleaning

Physical removal of organic material and decrease in microbial load

disinfection

¨Large reduction in microbe numbers - spores may remain

sterilisation

¨Removal/Destruction of ALL microbes and spores

58
Q

What is the definition of an outbreak?

A

¨An outbreak of an infection is defined as 2 or more cases of a infection linked in time and place.

59
Q

What is a serious complication of C Diff?

A

pseudomenbranous colitis

year 3 (3 decks)

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