Infection Flashcards
What are the clinical criteria to define gastroenteritis?
3 or more loose stools in 24 hrs plus at least one of: fever vomiting pain blood/mucus stools
What are the clinical features of dysentery?
LARGE bowel inflammation (shigella or amoeba dysentery)
What are the clinical features of diarrhoea?
increased fluidity and frequency of stool
Which organism is the most common cause of gastroenteritis leading to hospital admission?
Salmonella
Which organism is the most common cause of gastroenteritis?
Campylobacter infection (chicken)
Which organism is the most common cause of travellers diarrhoea?
enterotoxigenic E.coli. cannot be differentiated in the lab
List the defences (by body and hygiene practices) that prevent developing gastroenteritis?
Age
hygiene
gastric acid
gut motility
normal flora
gut immunity
What are the two main ‘types’ of diarrhoea
inflammatory non inflammatory
What are the main features of inflammatory diarrhoea?
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
What are the main features of non inflammatory diarrhoea?
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
What are the two most common organisms causing gastroenteritis?
campylobacter and salmonella
What do you need to cover in assessment of patient with suspected gastroenteritis ?
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
Which investigations are needed in gastroenteritis?
Stool and blood culture
renal function
blood count (haemolysis)
sigmoidoscopy X-Ray
serology
What is haemolytic uraemic syndrome
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
Which medicines increase the risk of gastroenteritis?
omeprazole ranitidine
List the differential diagnosis for gastroenteritis?
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.
What is the treatment of gastroenteritis?
RAFT Rehydration
Antimicrobials
Fasting
Treatment of complications
What are the clinical features of salmonella infection?
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
What disease is a person at risk of developing after they have had salmonella infection?
- 20/75 (27%) have Irritable Bowel Syndrome symptoms at 6 months
What are the clinical features of campylobacter infection?
C jejuni principle pathogen - Incubation up to 7 days - Infection clears within 3 weeks - Severe abdo pain +/- colitic picture - Rarely invasive (immunocompromised) - <1%
What would a positive blood culture indicate in someone with campylobacter infection?
It is rarely invasive, so check for compromised immune system HIV etc.
Which diseases is a person at risk of developing after they have had a campylobacter infection?
Guillain-Barré syndrome or reactive arthritis
What are the clinical features of e.coli 0157?
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
Is there a cholera vaccine?
Yes
What does shigella cause?
disease in children (nurseries) and in travellers. Seizures and HUS may complicate
Do antibiotics shorten the length of travellers diarrhoea?
Yes Can be used in Severe community-acquired gastro-enteritis or compromised patient
What is the most common viral cause of gastroenteritis? What are its characteristics?
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.
What are the 3 parasites that can cause gastroenteritis? What are the features of each?
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)
Which antibiotics increase the risk of CDiff infection?
AVOID 4 Cs of antibiotics clindamycin, cephalosporins, co-amoxiclav and ciprofloxacin (clarithromycin)
What percentage of patients given antimicrobials get diarrhoea?
5-10%
What are the main toxins in CDiff infection?
toxins A (enterotoxin) and B (cytotoxin)
What is the treatment for C.Diff infection?
metronidazole (up to 6% resistant, poor stool concn.) - vancomycin (cost and drug resistance in gut flora) - teicoplanin/fusidic acid/ cholestyramine - surgery
What is the name of the stool test you need to order for parasites?
P C O (parasites, cysts and ova)
List risk factors for sepsis
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
What are the important warning signs for sepsis?
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
Which tests should be carried out for sepsis?
blood gas for glucose and lactate blood culture full blood count C-reactive protein urea and electrolytes creatinine clotting screen
Which blood test would indicate that a person is in sepsis and high risk? What value?
Lactate over 2
List the ‘sepsis 6’ to be carried out immediately if sepsis is suspected
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
What score is used for pneumonia? What does it stand for?
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
What is the recommended daily fluid bolus for a patient that is 70 kg?
2 litres over the space of 24 hours
What are three key things to ask about in a history when assessing for sepsis?
travel
occupation
hospitalisation
When is it classed as oliguria?
urine out put less than 0.5ml/kg/hr
In sepsis, what are the two different mediators and their effects?
- 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
For each hour in delaying antibiotics in septic shock, how much does mortality increase by?
7.6 %
What does SIRS mean?
systemic inflammatory response syndrome
(ie dont have to have infection to have SIRS)
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?
qSOFA
BP systolic under 100mmHg
altered mental status
RR over 22
a score of over 2 is considered high risk (think escalation to HDU)
What is the difference between septic shock and sepsis?
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%
Re HIV
List ways HIV can be spread
sexual
vertical
contaminated blood products
organ transplant
share needles during injecting drug misuse
Which cells does HIV attack?
Which surface glycoprotein on the virus attaches to the host?
What is a normal CD4 count?
CD4 T helper cells (lymphocytes)
gp 120
above 500
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?
Less than 200
MAINLY in T helper cells but also present in skin and brain (therefore get disease in these places)
Which factor is of interest in HIV which helps the binding of HIV to CD4?
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.
What is the definition of a healthcare acquired infection?
an infection in an inpatient setting that occurs 48 hours after admission OR within 48 hours of discharge
What is the difference between colonisation and infection?
colonisation: where there is bacteria on the skin but cause no disease
infection; bacteria that cause disease (e.g. fever)
List the factors that can increase the risk of hospita acquired infections
both from host and microbial
¨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
What are the main modes of spread for hospital acquired bacteria and list a microbe for each
¨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
List the chain of infection
¨Source of microbe (endogenous or exogenous)
¨Transmission
¨
¨Host
What is the difference between cleaning, sterilisation and disinfection?
¨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
What is the definition of an outbreak?
¨An outbreak of an infection is defined as 2 or more cases of a infection linked in time and place.
What is a serious complication of C Diff?
pseudomenbranous colitis
