Infectious diseases Flashcards
what is the difference between gram positive and negative bacteria?
Gram positive bacteria have a thick peptidoglycan cell wall that stains with crystal violet stain. Gram negative bacteria don’t have this thick peptidoglycan cell wall and don’t stain with crystal violet stain but will stain with other stains.
infection table
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what is the abx tx for MRSA?
doxycycline or vancomycin
how is this infection treated?
“treat with antibiotics as per the local antibiotic policy”
how do you take an allergy hx?
When taking an allergy history always ask what reaction patients have had to become labelled allergic. If they report diarrhoea for example, this is a side effect rather than an allergy and means if necessary (for example in life threatening sepsis) they can still receive that medication
which abx can be used to treat gram psoitive bacteria?
amoxicillin, co-amox, clarithromycin, clindamycin, doxycycline, vancomycin
which abx can be used to treat gram neg bacteria?
co-amox, genatmicin, ciprofloxacin, doxycylcline
which abx can be used to treat anaerobic bacteria?
co-amox, clindamycin, metrondiazole, doxycyline
which abx can be used to treat atypical bacteria?
clarithromycin, ciprofloxacin, doxycyline
what is the stepwise process of escalating antibiotic treatment?
Start with amoxicillin which covers streptococcus, listeria and enterococcus
Switch to co-amoxiclav to additionally cover staphylococcus, haemophilus and e. coli
Switch to tazocin to additionally cover pseudomonas
Switch to meropenem to additionally cover ESBLs
Add teicoplanin or vancomycin to cover MRSA
Add clarithromycin or doxycycline to cover atypical bacteria
what is the pathophysiology behind sepsis?
bacteria recognised by macrophages/lymphocytes - cytokines acctive other parts of immune system
- vasodilation from NO
- endothelium line more permeable - oedema
- activates coag system - thrombocytopenia, haemorrahges, DIC
- blood lactate rises due to hypoperfusion
define septic shock
hen arterial blood pressure drops and results in organ hypo-perfusion. This leads to a rise in blood lactate as the organs begin anaerobic respiration
how is septic shock measured?
Systolic blood pressure less than 90 despite fluid resuscitation
Hyperlactaemia (lactate > 4 mmol/L)
how is septic shock managed?
ICU
Iv bolus
Noradrenaline
define severe sepsis
when sepsis results in organ dysfunction
Hypoxia
Oliguria
Acute Kidney Injury
Thrombocytopenia
Coagulation dysfunction
Hypotension
Hyperlactaemia (> 2 mmol/L)
what are the risk factors for developing sepsis?
Very young or old patients (under 1 or over 75 years)
Chronic conditions such as COPD and diabetes
Chemotherapy, immunosuppressants or steroids
Surgery or recent trauma or burns
Pregnancy or peripartum
Indwelling medical devices such as catheters or central lines
what is the NEWS score?
early signs of sepsis
Temperature
Heart rate
Respiratory rate
Oxygen saturations
Blood pressure
Consciousness level
Other signs on examination:
Signs of potential sources such as cellulitis, discharge from a wound, cough or dysuria
Non-blanching rash can indicate meningococcal septicaemia
Reduced urine output
Mottled skin
Cyanosis
Arrhythmias such as new onset atrial fibrillation
what is often the first sign of sepsis?
tachypnoea
how do elderley people atypically present with sepsis?
confusion/drowsy
which pts may appear normal on observations but are acutely unwell?
neutropenia and immunosuppressed
which investigations are required for suspected sepsis?
Full blood count to assess cell count including white cells and neutrophils
U&Es to assess kidney function and for acute kidney injury
LFTs to assess liver function and for possible source of infection
CRP to assess inflammation
Clotting to assess for disseminated intravascular coagulopathy (DIC)
Blood cultures to assess for bacteraemia
Blood gas to assess lactate, pH and glucose
Additional investigations can be helpful in locating the source of the infection:
Urine dipstick and culture
Chest xray
CT scan if intra-abdominal infection or abscess is suspected
Lumbar puncture for meningitis or encephalitis
how are sepsis patients managed?
Patients should be assessed and treatment initiated within 1 hour of presenting with suspected sepsis
sepsis 6
Three Tests:
Blood lactate level
Blood cultures
Urine output
Three Treatments:
Oxygen to maintain oxygen saturations 94-98% (or 88-92% in COPD)
Empirical broad spectrum antibiotics
IV fluids
define neutropenic sepsis and some causes
sepsis in a patient with a low neutrophil count of less than 1 x 109/L.
Anti-cancer chemotherapy
Clozapine (schizophrenia)
Hydroxychloroquine (rheumatoid arthritis)
Methotrexate (rheumatoid arthritis)
Sulfasalazine (rheumatoid arthritis)
Carbimazole (hyperthyroidism)
Quinine (malaria)
Infliximab (monoclonal antibody use for immunosuppression)
Rituximab (monoclonal antibody use for immunosuppression)
how is neutropenic sepsis treated?
sepsis 6 - may gave different policy
with immediate broad spectrum antibiotics such as piperacillin with tazobactam (tazocin)
what are the two main causes of a chest infection?
Streptococcus pneumoniae (50%)
Haemophilus influenzae (20%)
what are the other causes and their associations of a chest infection?
Moraxella catarrhalis in immunocompromised patients or those with chronic pulmonary disease
Pseudomonas aeruginosa in patients with cystic fibrosis or bronchiectasis
Staphylococcus aureus in patients with cystic fibrosis
what are the 5 causes of atypical pneumonia?
“legions of psittaci MCQs”:
Legions – Legionella pneumophila
Psittaci – Chlamydia psittaci
M – Mycoplasma pneumoniae
C – Chlamydydophila pneumoniae
Qs – Q fever (coxiella burnetii)
what is the abx used in chest infection?
Amoxicillin
Alternatives:
Erythromycin / clarithromycin
Doxycycline
which abx are used to treat atypical chest infections?
clarithromycin
levofloxacin
doxycycline
what are the sx of UTI?
Dysuria (pain, stinging or burning when passing urine)
Suprapubic pain or discomfort
Frequency
Urgency
Incontinence
Confusion is commonly the only symptom in older more frail patients
what are the sx of pyelonephritis?
Fever is a more prominent feature than lower urinary tract infections.
Loin, suprapubic or back pain. This may be bilateral or unilateral.
Looking and feeling generally unwell
Vomiting
Loss of appetite
Haematuria
Renal angle tenderness on examination
how is a UTI investigated?
urine dipstick
MSU to microbiology lab for culture and sensitivity trsting
how are the results of urine dipstick interpreted?
Nitrites are a better indication of infection than leukocytes. If both are present then the patient should be treated as a UTI. If only nitrites are present then it is worth treating as a UTI however if only leukocytes are present then the patient should not be treated as a UTI unless there is clinical evidence that they have a UTI
what is the likely causative organism of UTI and some other causes?
E.coli
Klebsiella pneumoniae (gram-negative anaerobic rod)
Enterococcus
Pseudomonas aeruginosa
Staphylococcus saprophyticus
Candida albicans (fungal)
how is UTI managed?
3 days of antibiotics for a simple lower urinary tract infection in women
5-10 days of antibiotics for women that are immunosuppressed, have abnormal anatomy or impaired kidney function
7 days of antibiotics for men, pregnant women or catheter related UTIs
- Trimethoprim
- Nitrofurantoin
how are UTI’s managed in pregnancy?
increase the risk of pyelonephritis, premature rupture of membranes and pre-term labour.
7 days of antibiotics (even with asymptomatic bacteruria)
Urine for culture and sensitivities
First line: nitrofurantoin
Second line: cefalexin or amoxicillin
Nitrofurantoin is generally avoided in the third trimester as it is linked with haemolytic anaemia in the newborn.
Trimethoprim is generally considered safe in pregnancy but avoided in the first trimester or if they are on another medication that affects folic acid (such as anti-epileptics) due to the anti-folate effects.
how is pyelonephritis managed?
hospital if septic
7-10 days -
Cefalexin
Co-amoxiclav
Trimethoprim
Ciprofloxacin
define cellulitis
infection of the skin and the soft tissues underneath
from breach in skin barrier - trauma,eczema, fungal nail, ulcers
what skin changes will be seen in cellulitis?
Erythema (red discolouration)
Warm or hot to touch
Tense
Thickened
Oedematous
Bullae (fluid-filled blisters)
A golden-yellow crust can be present and indicate a staphylococcus aureus infection
what are the most common cause of cellulitis?
Staphylococcus aureus
Group A Streptococcus (mainly streptococcus pyogenes)
Group C Streptococcus (mainly Streptococcus dysgalactiae)
MRSA
how is the severity of cellulitis classified?
Eron:
Class 1 – no systemic toxicity or comorbidity
Class 2 – systemic toxicity or comorbidity
Class 3 – significant systemic toxicity or significant comorbidity
Class 4 – sepsis or life-threatening
how is cellulitis treated?
flucloxacillin
or clarithroycin, clindamycin, co-amoxiclav
in which circumstances can antibiotics be used for viral infections?
immunocompromised, several co morbidities
is tonsilitis, otitis media and rhinosinusitis more viral or bacterial
viral
what is bacterial tonsillitis most commonly caused by?
Group A Streptococcus (GAS) infections, mainly streptococcus pyogenes.
what are otitis media, tonsillitis and sinusitis most commonly caused by?
Streptococcus pneumoniae - most
Haemophilus influenzae
Morazella catarrhalis
Staphylococcus aureus
how is tonsilitis established to be a viral or bacterial infection?
centor criteria:
< 3 indicates they are unlikely to benefit from an antibiotic and antibiotics should not routinely be given. A score of ≥ 3 gives a 40 – 60 % probability of bacterial tonsillitis and it is appropriate to offer antibiotics. One point is given for each of the following:
Fever > 38ºC
Tonsillar exudates
Absence of cough
Tender anterior cervical lymph nodes (lymphadenopathy)
how is bacterial tonsilitis treated?
penicillin V for 10 days
how does otitis media present
ear pain
bulging red tympanic membrane
ear drum perforates - discharge
how is otitis media treated if it is bacterial?
amoxicillin
what are the NICE guidlines for managing sinusitis?
Symptoms for less than 10 days: No antibiotics.
No improvement after 10 days: 2 weeks of high-dose steroid nasal spray
No improvement after 10 days and likely bacterial cause: consider delayed or immediate prescription of antibiotics
Penicillin V (also called phenoxymethylpenicillin) for a 5 day course is typically first line
what are the possible intra-abdominal infections?
Acute diverticulitis
Cholecystitis (with secondary infection)
Ascending cholangitis
Appendicitis
Spontaneous bacterial peritonitis
Intra-abdominal abscess
what are the common causes of intra-abdominal infections?
Anaerobes (e.g. bacteroides and clostridium)
E. coli
Klebsiella
Enterococcus
Streptococcus
what are the commonc regimes for inta abdominal infections?
Co-amoxiclav alone
Amoxicillin plus gentamicin plus metronidazole
Ciprofloxacin plus metronidazole (penicillin allergy)
Vancomycin plus gentamicin plus metronidazole (penicillin allergy)
what is spontaneous bacterial peritonitis caused by?
liver failure
what is the first line treatment for spontaneous bacterial peritonitis?
piperacillin/tazobactam (tazocin)
how does septic arthritis present?
Hot, red, swollen and painful joint
Stiffness and reduced range of motion
Systemic symptoms such as fever, lethargy and sepsis
what is the most common causative organism of septic arthritis?
staph aureus
or
Neisseria gonorrhoea (gonococcus) in sexually active individuals
Group A Streptococcus (most commonly Streptococcus pyogenes)
Haemophilus influenza
Escherichia coli (E. coli)
what are the ddx for septic arthritis?
gout
pseudogout
reactive arthritis
haemoarthritis
how is septic arthritis managed?
aspirate = gram stain, micrscopy, culture, sensitivites
give empiral abx IV for 3-6 weeks
Flucloxacillin plus rifampicin is often first line
what is the pathophysiology of influenza?
three types: A, B and C, of which A and B are the most common. The A type has different H and N subtypes and you may hear about different strains, for example H1N1 (swine flu) and H5N1 (avian flu)
which groups of people are offered an influenza vaccine?
Aged 65
Young children
Pregnant women
Chronic health conditions such as asthma, COPD, heart failure and diabetes
Healthcare workers and carers
how does influenza present?
Fever
Coryzal symptoms
Lethargy and fatigue
Anorexia (loss of appetite)
Muscle and joint aches
Headache
Dry cough
Sore throat
how is influenza investigated?
viral nasal or throat swabs to virology lab for PCR naalysis
how is influenza managed?
public health monitor number of cases
if at risk of complications - ostelamivir within 48 hrs of sx to be effective
post exposure prophylaxis to higher risk
what are the possible complications of influenza?
Otitis media, sinusitis and bronchitis
Viral pneumonia
Secondary bacteria pneumonia
Worsening of chronic health conditions such as COPD and heart failure
Febrile convulsions (young children)
Encephalitis
what is the most common cause of gastroenteritis?
viral
what are the viral causes of gastroenteritis?
rotavirus
norovirus
adenovirus
how is e.coli spread and how does it work/
infected faeces, unwashed salads or water
produces shiga toxin - abdo cramps, bloody diarrhoea and vomit
destroys red blood cells and can lead to haemolytic uraemic syndrome (and use of abx increases risk)
what is the causes of travellers diarrhoea and how is it spread?
campylobacter
Raw or improperly cooked poultry
Untreated water
Unpasteurised milk
what is the incubation periods and symptoms of campylobacter?
Incubation is usually 2-5 days. Symptoms resolve after 3-6 days. Symptoms are:
Abdominal cramps
Diarrhoea often with blood
Vomiting
Fever
how is campylobacter treated and in which circumstances?
severe sx or HIV, HF
azithromycin