Infectious Disease Flashcards
Respiratory infections Skin infections UTIs Intra-abdominal infection + hepatitis Gastroenteritis Meningitis Endocarditis Immunocompromise
What are the sepsis 6?
Give 3: IV fluids, Abx, O2 Take 3: Blood cultures, urine output, lactate
What are the sepsis red flags?
RR >25
HR >130
BP <90 (or 40 below normal)
Temperature >38
Acutely altered mental state
Ashen/mottled appearance
Lactate >2
Anuric in last 18h/<0.5ml/kg/hr
What is the Centor score used for?
Score >=3 –> 50% of bacterial URTI –> give penicillin
What are the Centor criteria?
Can’t cough
Exudate on tonsils
Nodes enlarged
Temperature
What are the symptoms of pneumonia?
Fever
Breathlessness
Cough +/- purulent sputum/haemoptysis
Pleuritic pain (may radiate to flank DDx UTI) Confusion (esp in elderly, may be hypothermic, AMTS<8)
Malaise
Anorexia
What are the clinical signs of pneumonia?
Pyrexia
Tachycardia
Hypotension
Tachypnoea
Consolidation (CXR, bronchial breathing, dull to percussion, crackles, increased fremitus)
Cyanosis
How do you CURB-65 score?
1 point each for:
- Confusion (AMTS <8)
- Urea >7 (due to dehydration)
- RR >30
- BP <90
- Age >65
How does CURB-65 influence management?
Indicator of mortality
0-1: PO home treatment
2: PO hospital treatment
3+: IV hospital treatment, consider ITU
Also consider: O2 sats, comorbidities, multilobar; underscores in young patients
How do you investigate pneumonia?
Bloods: CRP, FBC, U+Es, LFTs
Orifices: Urine dip (pneumococcal/legionella antigens), sputum if ?TB, swab for ?flu
X-rays: CXR + repeat in 6w
E: N/A
S: Consider atypical organisms if not improving with Abx
Who is at risk of influenza infection?
Extremes of age
Renal (dialysis pts)
Liver (cirrhosis)
Heart (IHD)
Diabetes, immunocompromised
Neuro patients (e.g. MS)
What are the common causes of CAP?
Streptococcus pneumoniae (rust-coloured)
Haemophilus influenzae
What is a HAP?
Pneumonia >48h after hospital admission
What are the common causative agents of a HAP?
Staph aureus
G-ve enterobacteria
Klebsiella
Pseudomonas
What are the common atypical agents?
Mycoplasma pneumoniae
Legionella
Chlamydia
Viral (flu commonly complicates MRSA pneumonia)
What are common causes of aspiration pneumonia?
Stroke, myasthenia, bulbar palsies, reduced consciousness
- Klebsiella (currant jelly)
- Other anaerobes
- Strep pneumo
What are the causative agents of pneumonia in the immunocompromised?
Pneumocytis jirovecii
Aspergillus
Mycobacteria
Mycoplasma
Klebsiella
S. aureus,
S. pneumo
What are the common causes of pneumonia in neonates?
Group B strep, E. Coli (from vaginal canal)
What are the common causes of pneumonia in infants?
Chlamydia, S pneumoniae
What are the common causes of pneumonia in young adults?
Mycoplasma pneumoniae Chlamydia S pneumo
What are the common causes of pneumonia in the elderly?
S pneumo H influenzae
What makes you suspect IECOPD?
Increasing breathlessness/O2 requirement
Fevers
Change in volume/colour of sputum
Changes on CXR/crackles
Common cause of pneumonia in bronchiectasis/CF
Pseudomonas
Causes bilateral cavitating lesions on CXR
Staphylococcal (common post-influenza)
Cavitating pneumonia of upper lobes
Klebsiella (rare)
Flu-like symptoms followed by dry cough
Mycoplasma/Legionella
Reticular-nodular shadowing/patchy consolidation on CXR
Mycoplasma
Organism causing bi-basal consolidations on CXR
Legionella
Results with Legionella
Hyponatraemia, lymphopaenia, deranged LFTs, haematuria, early confusion
Biphasic illness: pharyngitis, hoarseness, otitis –> pneumonia
Chlamydia
Infective complications of pneumonia
Septicaemia
Empyema
Lung abscess
Endocarditis/myocarditis
Non-infective complications of pneumonia
Hypotension
Respiratory failure (commonly Type 1)
AF (treat w/ digoxin)
Jaundice (esp from Abx)
Common cause of bacterial tonsilitis in children?
Group A strep: scarlet fever (toxin) –> rheumatic fever (autoimmune) –> endocarditis risk/valvular disease
What layer of skin is affected in impetigo?
Epidermis
What is the appearance of impetigo?
Vesicles with honey-coloured crust (often on face of child)
Common causative agents of impetigo?
Staph aureus, Strep pyogenes
What is the appearance of eysipelas?
Painful, erythematous, RAISED + REGULAR border. well demarcated
What is the appearance of cellulitis?
Painful, erythematous, FLAT + IRREGULAR border, diffuse. May have lymphangitis track.
What layer of the skin is affected in erysipelas?
Superficial dermis
What layer of the skin is affected in cellulitis?
Deep dermis
What are the common causative agents of erysipelas and cellulitis?
Strep. pyogenes, Strep. agalactiae > S. aureus
What is the appearance of folliculitis?
Localised inflamed papules (no abx treatment necessary)
What is the appearance of a skin abscess?
Raised, tender nodule
Central purulence, initially firm then moveable
What agent commonly causes skin abscesses?
S. aureus
What are the early signs of necrotising fasciitis?
Pain out of proportion to patient appearance
Erythema spreading rapidly (hours-days),
flat + not sharply demarcated
What are necrotising fasciitis ‘red flags’?
Diabetes/cardiovascular comorbidity
Anaesthesia
Purplish/dusky appearance
Bullae/putrid discharge
Gas gangrene
What are the common causative agents of necrotising fasciitis?
Monomicrobial: S. pyogenes, C. perfringens (gas gangrene)
Polymicrobial: After abdominal surgery/perineal infection –> enteric bacteria/anaerobes
What are the common causative agents of UTIs?
E. Coli and other G-ve rods (e.g. Proteus)
Pseudomonas, Klebsiella for HAIs/CA-UTIs
What is the difference between complicated and uncomplicated UTI?
Uncomplicated: Normal renal structure/f(x)
Complicated: Structural/functional abnormality e.g. renal transplant, stones, catheter, obstruction
What are the risk factors for UTIs?
Bacterial inoculation: Sexual activity, urinary incontinence, faecal incontinence, constipation
Reduced urine flow: Obstruction, dehydration
Bacterial growth: Diabetes, immnosupression, pregnancy, stones, catheter
What are the infective causes of sterile pyuria?
Inadequately/recently treated UTI
TB/chlamydia/other STI
Appendicitis, prostatitis
What are the features of renal TB?
Sterile pyuria
Suprapubic pain
Loin pain
Night sweats/fevers/weight loss
Visible haematuria
What are the symptoms of cystitis?
Fever
Dysuria
Suprapubic pain
Frequency
Urgency
Haematuria
Polyuria
What are the symptoms of acute pyelonephritis?
Fever
Rigor
Loin pain (check tenderness, progresses rapidly!)
Vomiting
What are the symptoms of prostatitis?
Fever
Nausea
Perineal pain
Swollen/tender prostate on PR
When do you treat asymptomatic bacteriuria?
Pregnancy
Infants <1yo
Renal transplant patients
Remember 1/3 no UTI, 1/3 diff bacteria, 1/3 UTI
What are the noninfective causes of sterile pyuria?
Recent catheter
Drugs e.g. steroids
PKD
Renal tract tumour
Tubulointerstitial nephritis
SLE
Stones
Pregnancy
How do you investigate a UTI?
Bloods: (systemically unwell) FBC, U+E, CRP, blood culture (low Sn)
Orifices: Urinalysis (-ve nitrites + leukocytes = 92% NPV);?urine culture
X: USS if complicated UTI, recurrent UTI, pyelonephritis, failure to respond to treatment
What are the indications for a MSU culture?
Pregnancy
Elderly
Immunocompromised/diabetic
Recurrent/failed treatment
What are the symptoms of epididymo-orchitis?
Erythema, oedema, urinary symptoms, fever, pain
Exclude testicular torsion!
What are the symptoms of pelvic inflammatory disease?
Vaginal discharge, pelvic pain, possible abdominal/cervical tenderness
Risk: multiple sexual partners, unprotected intercourse, prev. PID
What is the treatment of CA-UTI, pyelonephritis, prostatitis?
Co-amoxiclav
What is the treatment of uncomplicated UTI?
Nitrofurantoin (concentrates in urine, 3-day for women and 7-day for men)
What is the treatment of of mild CAP (CURB <2)?
Amoxicillin
What is the treatment of severe CAP?
Amoxicillin + clarithromycin
What is the treatment of septic CAP?
Co-amox + clarithromycin
What organisms are asplenic patients most at risk from?
Encapsulated bacteria:
- Strep pneumo
- H. influenzae
- N. meningiditis
- Staphylococci
What organisms commonly cause neutropaenic sepsis?
G-ve gut organisms (mucosal translocation):
- E. Coli, anaerobes, pseudomonas (lines)
>
G+ve:
- Enterococci, streptococci (nasopharynx)
>
Fungi:
- Aspergillus (gram hyphae, halo sign), Candida
What organism commonly causes infections in burns patients?
Pseudomonas
Symptoms of empyema
Recurrent fever
Chest tenderness
Effusion on CXR
Symptoms of a lung abscess
swinging fever
cavitating lesion on CXR (may be fluid filled)
purulent sputum cough
What is gastroenteritis?
Diarrhoea +/- vomiting due to enteric infection
What is the difference between diarrhoea and dysentery?
Diarrhoea: >3 episodes of semi-liquid stool per day
Dysentery: infectious gastroenteritis with bloody diarrhoea
What are the common causes of dysentery?
2S, 2C, 2E:
- Shigella, Salmonella
- Campylobacter, C. diff
- Enterohaemmorhagic E. Coli, Entamoebic histolytica (amoebic dysentery)
- Yersinia
What are the viral causes (50-60% of all gastroenteritis) of gastroenteritis?
Norovirus
Rotavirus
What is the epidemiology of norovirus?
Causes epidemic outbreaks in institutions
What is the epidemiology and symptoms of rotavirus?
Commonest cause of diarrhoea in children (universal infection by 5yo)
1-3d incubation, 3-8d gastroenteritis, fever, abdominal pain.
What is the most common cause of traveller’s diarrhoea and what is the timecourse?
Enterotoxicogenic E. Coli
Incubation 1-3d
Usually <1 week (3-4d) watery diarrhoea.
What is the epidemiology and symptoms for Campylobacter gastroenteritis?
Most common cause of dysentery.
Undercooked meat.
Dysentery, pain, fever, headache.
What is the epidemiology, incubation, symptoms for Salmonella gastroenteritis?
Comes from undercooked eggs, poultry, meat.
Incubation 12-36h. Diarrhoea, cramps, fever.
What do you suspect in persistent (>14d) traveller’s diarrhoea?
Giardia (Esp with upper GI symptoms: bloating, flatulence due to villous atrophy)
Entamoeba histolytica
Shigella
Malaria
HIV
What is the epidemiology, incubation, symptoms of EHEC?
Shiga-toxin producing E. Coli ‘Petting zoo illness’ in children. ?meningism
Incubation 3-8d
When would you suspect and how would you confirm C. diff infection?
Recent broad-spectrum abx in hospitalised pt
Watery diarrhoea, pseudomembranous colitis, ileus, toxic megacolon, neutrophilia.
Confirm with glutamate dehydrogenase or toxin immunoassay
What are the common causes of toxin-mediated gastroenteritis?
Staph aureus: Sudden onset diarrhoea <6h after exposure to dairy, custard
Bacillus cereus: Vomiting (<6h) or diarrhoea (<16h) from leftover food, rice.
What are the penicillin B-lactams?
Penicillin
Flucloxacillin
Amoxicillin/ampicillin
Co-amoxiclav (Augmentin)
Piperacillin-tazobactam (Tazocin)
What are the cephalosporin B-lactams?
Ceftriaxone
Ceftazidime
What antibiotic class is suitable against ESBLs?
Carbapenems
What class of antibiotics is gentamicin and what are the common side effects?
Aminoglycoside
Oto (vestibular) and nephrotoxicity (not suitable for pregnancy)
Which IV antibiotic is suitable against all gram positives but no gram negatives?
Vancomycin, glycopeptide
Nephrotoxic
What class of antibiotics is ciprofloxacin? When is it contraindicated?
Fluoroquinolone. Teratogenic
What class of antibiotic is clarithromycin?
Macrolide
Which antibiotics are effective against Pseudomonas?
Ciprofloxacin
Meropenem
Ceftazidime
Tazocin
Which antibiotics are effective against MRSA?
Vancomycin
Linezolid
Co-trimexazole (septrin)
Risk factors for infective peritonitis?
Spontaneous: 2ry to ascites
Intra-op soiling
Bowel perforation:
- IBD
- ischaemia
- diverticulitis
- appendicitis
- malignancy
- ulceration
Peritoneal dialysis
What are the signs of peritonitis?
Guarding
Rebound tenderness
+ve cough test
Absent bowel sounds
Pneumoperitoneum on erect CXR
NB: ALWAYS CHECK SERUM AMYLASE FOR PANCREATITIS
What are the causes of a liver abscess?
Haematogenous spread of bacteria, esp post-dysentery
Cholangitis
Appendicitis
2ry infection of tumour/mets
Presentation of liver abscess
RUQ tenderness
Malaise, anorexia, nausea
Hepatomegaly
Jaundice
Deranged LFTs
R-sided pleural effusion
What is the difference between biliary colic, cholecystitis, and cholangitis?
Biliary colic: Colicky pain radiating to back due to gallstones in neck of gallbladder. RUQ pain.
Cholecystitis: Acute inflammation of gallbladder neck. Fever + raised WCC. RUQ pain.
Cholangitis: RUQ pain + rigors/fever + jaundice (Charcot’s triad). Due to stone blockage of CBD + infection
What are the symptoms of acute viral hepatitis?
Malaise
Low-grade fever
Arthralgia
What are the signs of acute viral hepatitis?
Jaundice
Hepatomegaly (mild)
Raise ALT and bilirubin
What are the causative agents of acute hepatitis and any distinguishing features/incubation time?
Hep A/E (faeco-oral spread, incubation 2-6w)
CMV/EBV (lymphocytosis c.f. HepA/E)
HBV (incubation up to 75d)
What are the causative agents of chronic hepatitis?
HBV
HCV
Both are blood-borne viruses
How do you distinguish between acute and chronic HBV infection on serology?
Acute has IgM.
Both have sAg and eAg and DNA.
Chronic HBV has ground-glass hepatocytes. Increased risk of HCC.
How do you distinguish between vaccinated and exposed individuals for HBV?
Vaccinees: HBsAb but no HBcAb
Exposed: HBsAb AND HBcAb
What does HBeAg indicate for viral hepatitis?
Marker of replication (along with DNA), indicates early vs late chronic
What are the clinical features of meningitis?
Fever (may be absent in elderly)
Neck stiffness (Examination finding)
Changes in mental status
Headache
Leg/joint pain
Photophobia
Non-blanching purpura (N. meningiditis)
Irritability/lethargy in infants
What are the signs of raised ICP that contraindicate lumbar puncture?
Headache (worse on cough, leaning forward)
Vomiting
Reduced GCS
Papilloedema
Pupil constriction
Low HR and high BP
Hx of CNS lesion/seizures in past week
Focal neurology
How would you investigate ?meningitis?
Lumbar puncture
HIV test (aseptic meningitis)
Blood cultures
FBC
Blood glucose
U+E
Coagulation (for DIC)
What are the LP results in viral meningitis?
Lymphocytosis
Low protein
Normal glucose (>50% BG)
What are the LP results in bacterial meningitis?
Neutrophilia
High protein
High CSF pressure
Low glucose (<50% BG)
What are the LP results in TB meningitis?
Lymphocytosis
Very high protein
Very low (<33%) glucose
High CSF pressure
Clots on standing
What may cause aseptic meningitis?
Viral (incl HIV)
Treated bacterial (culture -ve after 1h for NM, 4-6h for SP, PCR +ve still)
TB/fungal meningitis
What are the risk factors for Listeria meningitis?
>55, neonate, immunocompromised, pregnant
What commonly causes meningitis in children <5?
H influenzae
What commonly causes meningitis in teens?
N. meningiditis (meningococcus)
What commonly causes meningitis in adults?
Strep pneumo (pneumococcus)
What are the features of meningo-encephalitis?
Seizures
Change in GCS
Neurological deficit
Abnormal speech/behaviour
What are the clinical features of a brain abscess?
Early morning headache
Seizures
Fevers
False localising neurology
Papilloedema
What are the causes of brain abscesses?
HIV: Toxoplasma
Otitis media/sinusitis/dental abscess: Streptococcus
Trauma/neurosurgery: Staph aureus
Neutropenia: GNRs
Endocarditis: Staph aureus, strep viridans
What are the clinical features of infective endocarditis?
Symptoms:
- Malaise
- Weight loss/anorexia
- Fevers
- Septic emboli elsewhere
Signs:
- New heart murmur
- Osler nodes/Janeway lesions
- Splinter haemmorhages
- Clubbing
- Heart failure
- Heart block/arrhythmia
What are the risk factors for endocarditis?
IVDU
Rheumatic fever
Prosthetic valve
Other valve disease (usually subacute course)
Previous endocarditis
Long lines/haemodialysis
Poor dentition
What are the major Duke diagnostic criteria for endocarditis?
Blood culture +ve in 2 seperate cultures
Persistently +ve blood cultures (3 >12h apart)
Blood cultures +ve for Coxiella burnetti
Vegetations on echo/valvular lesions on CT
What are the minor duke diagnostic criteria for endocarditis?
Fever >38
IVDU
predisposing heart condition
Vascular signs (emboli, Janeway lesions)
Immunologic signs (glomerulonephritis, Osler’s nodes, Roth spots, splinter haemmorhages)
How do you diagnose endocarditis?
2 major or 1 major + 3 minor
Fever + new murmur = IE until proven otherwise
How do you investigate endocarditis?
3x blood cultures at different times + sites
FBC: normocytic, normochromic anaemia
Urinalysis (microscopic haematuria)
Echo + ECG
What are the common causative organisms for endocarditis?
Staph aureus
C-ve staph
Strep viridans
What is the main concern with aminoglycosides (and give example of one)
Ototoxicity (vestibular symptoms)
Nephrotoxicity (check renal fx)
Gentamicin
How do you treat neutropaenic sepsis?
Oxygen
Fluids - NOT HARTMANNS
Abx - Tazocin (interacts with hartmanns, also penicillin allergy)
Symptoms of norovirus
Acute-onset vomiting, watery diarrhoea, cramps, nausea
Timecourse of norovirus
1d incubation, 24-72h timecourse
Complications of Campylobacter gastroenteritis?
Complications: septicaemia, G-B syndrome, hepatitis, pancreatitis
Complications of Salmonella gastroenteritis?
Bactaraemia, meningitis, osteomyelitis, septic arthritis
Dangerous complication of EHEC?
Do NOT give Abx –> increase risk of HUS due to toxin leak
Haemolytic-uraemic syndrome: haemolytic anaemia + thrombocytopaenia + high urea (AKI)
2-14d after onset of diarrhoea.
First-line treatment for C. diff infection?
Metronidazole
Signs of HIV causing meningitis
HIV: Lymphadenopathy, candidiasis, uveitis, dermatitis
Signs of HSV causing meningitis
cold sores/genital vesicles
Signs of EBV/CMV meningitis
Hx of glandular fever Sore throat, jaundice, lymphadenopathy

Diffuse reticulo-nodular shadowing –> Mycoplasma pneumonia

Bilateral consolidations - legionella

Cavitating lesion - staphylococcal