Medicine - Infectious diseases Flashcards
Define neutropenia
Low WCC and inability to fight off infections
<0.5 or <1 and falling
Define SIRS
systemic inflammatory response syndrome the bodys response to injury Must have: - RR >20 - HR >90 - WCC >12x10^9 - Fever
Define sepsis
- life threatening organ dysfunction in response to infection
Use Q-SOFA:
- BP <100 systolic
- Altered GCS
- RR >22
Define septic shock
Sepsis with a high lactate despite adequate fluid resuscitation
What are the SIRS criteria?
RR > 20
HR > 90
WCC >12
Fever
What are the Q-SOFA criteria?
BP <100 systolic
Altered GCS/confusion
RR >22
What are the three main steps in the pathogenesis of sepsis?
1) Immune system activation
2) Endothelial and coagulation system
3) Inflammation and organ dysfunction
What are the S/Sx and the RFx for sepsis?
RFx:
- malignancy
- immunosuppression
- > 65yrs
- alcohol
- DM
- haemodialysis
S/Sx:
- Reduced UO
- tachy HR/RR
- low GCS
- fever
- reduced CRT
- reduced O2 sats
- cyanosis
Describe the treatment of sepsis
Sepsis 6! (BAFLOU)
Differentiate infection from intoxication
Infection = pathogenesis occurs in gut after ingestion e.g. E.coli, salmonella
Intoxication = pathogen/toxins grow on food before ingestion, shorter incubation period e.g. bacillus cereus
Define gastroenteritis and what are its common causes?
Name 4 organisms which can cause bloody diarrhoea
Gastroenteritis = diarrhoea +/- vomiting due to enteric infection with virus/bacteria/parasite
Campylobacter
E.coli
Salmonella
Shigella
What investigations should be carried out for someone with acute diarrhoea/gastroenteritis?
Hx and Ex Stool cultures Bloods: FBC (WCC, Hb, plts), U&E's (low K, high urea/cr), antibodies? (IBD) AXR Endoscopy
How should gastroenteritis be treated?
Most mild infections resolve spontaneously
Maintain hydration
No anti-motility agents
ONLY use Abx if severe and prolonged
Infection control and pt education/PH measures
Describe the cause, presentation, diagnosis and treatment of influenza
Virus
Types A/B - cause serious infection
Type C - causes no significant illness
Presents: sore throat, cough, in winter, unvaccinated?
Clinical diagnosis
Prophylactic vaccine/can give tamiflu if severe
Complications -> OM, sinusitis, pneumonia
Describe the cause, presentation, diagnosis and treatment of the common cold
Common in winter
Caused by virus: rhinovirus/coronovirus
Presents: sore throat, runny nose, cough, headache
Clinical diagnosis with no vaccine/treatment
Complications -> OM, sinusitis
Describe the cause, presentation, diagnosis and treatment of pharyngitis
Viral or bacterial causes (usually adenovirus)
Presents with:
- red swollen tonsils, red throat, sore head (viral)
- grey furry tongue, red throat, swollen uvula, whitish spots (bacterial)
Describe the cause, presentation, diagnosis and treatment of infectious mononucleosis
EBV infection which targets B lymphocytes and oropharyngeal epithelial cells
Presents:
- sore throat, fever, weight loss, lymphadenopathy, splenomegaly, jaundice, hepatomegaly
Clinical diagnosis
Describe the cause, presentation, diagnosis and treatment of croup
Due to viruses: influenze, parainfluenza, RSV, coronavirus
Upper airway inflammation and oedema, with distinctive barking cough and wheeze/stridor/sternal in-drawing
Clinical diagnosis
Tx with steroids and supportive care
Describe the cause, presentation, diagnosis and treatment of bronchiolitis
Commonly affects children <2 yrs, but also in elderly/immunocompromised adults
Infection of the bronchioles
Nosocomial (originates in hospital) -> usually RSV
Fts: cough, tachypnoea, rhinitis, fever
Clinical diagnosis
Treatment: prophylacis w/ palivizumab (a monoclonal antibody given to those at risk)
What are the main causative agents of cellulitis?
Common organisms:
Group A beta-haemolytic strep (s. pyogenes)
Staph aureus
What are the risk factors for the development of cellulitis?
DM PVD Skin breaks Oedema Venous insufficiency Eczema
What are the signs/symptoms of cellulitis?
Erythema Warm Tender Oedematous Broken skin
What investigations should be carried out for someone with suspected cellulitis?
Hx and Ex FBC (WCC) Blood cultures Skin biopsy ?x-ray (osteomyelitis) ?USS (if abscess) ?MRI (if nec fasc)
Enron classification!
What antibiotics are used to treat cellulitis?
Fat is Clinically Gross
Fluclox
Clindamycin
Gent
What is MRSA and describe why it is so difficult to treat:
Methicillin resistant staph aureus
G+
Causes skin/soft tissue/joint/lung infections
Lives on moist body areas
Chronic carriers have increased infection risk
The bacteria has a MecA gene which encodes for a type of PBP which antibiotics cannot penetrate the wall of the bacteria through
What are the RFx for MRSA development?
Hospitals!
Abx exposure
Surgery
Nursing homes
How is MRSA treated?
If pt is tested positive, give pre-surgery peptidoglycan coverage: vanc/teicoplanin
Prevention is key: hand hygiene, antimicrobial stewardship
Treatment -> clind/vanc/teicoplanin/co-trimoxazole
What is C.Diff and the aetiology behind its infections?
Anaerobic G+ bacterial living in the gut
Forms spores = difficult to eradicate
Is the most common cause of Abx associated diarrhoea
Produces 2 toxins (A&B) (the testing of the toxins in the stool is essential as cultures can be + in healthy individuals)
What antibiotics can cause C.Diff?
Co-amoxiclav
Clindamycin
Ciprofloxacin
Cephalosporins
What are the components of the C.Diff severity score?
(measurements if severe): CAT-WC Creatinine - >1.5x baseline Albumin - <25 Temperature - >38.5 WCC - >15 Colon dilatation - >6cm
How should C.Diff be investigated for its diagnosis?
Bloods: FBC, WCC, albumin, creatinine, CRP…
Stool cultures and toxin testing
AXR/erect CXR
How should C.Diff be treated?
SIGHT Suspect it Isolate Gloves and apron (PPI) Hand washing and soap Test immediately
Stop any potential causative antibiotics Supportive - bowel rest and fluids Oral vanc/metronidazole ?faecal transplant ?surgical intervention
What is the definition of meningitis and its main causes?
Inflammation of meninges +/- cerebrum
Caused by various bacteria
Can be primary or secondary (TB/malaria)
Main bacterial causes:
- neisseria gonorrhoea (G- diplococi)
- strep pneumoniae (G+ strep)
Viral causes:
- mumps, HSV, HIV
What are the RFx and the S/Sx of meningitis?
RFx:
- ear infections
- throat infections
- neurosurgery
- alcohol
- pregnancy
- immunosuppression
S/Sx:
- pyrexia
- meningism (photophobia, neck stiffness, headache, Kernigs sign)
- low GCS
- petechial non-blanching rash
What is a common differential for meningitis which can infect immunocompromised individuals
cryptococcal meningitis
caused by cryptococcus neoformans (fungal!)
How is meningitis investigated (differentiate the LP findings!)
Hx and Ex Blood cultures and PCR Full set of bloods Throat gargle LP! CSF cell count and culture
->
Glucose low if bacterial
WCC high but neutrophils (bacterial) or lymphocytes (viral)
Protein high in bacterial but N/high in viral
Cloudy if bacterial or clear if viral
Opening pressure high/normal if bacterial, or normal if viral
How is meningitis managed?
Antibiotics immediately
- > IV ceftriaxone (if bacterial) and amoxicillin
- > +/- dexamethasone
Prophylactically give close contacts ciprofloxacin/rifampicin
Describe HHV1 & 2
Viruses live in sensory neurons causing lifelong latent infection which can reactivate
Presents as:
- herpes labialis (lips) = HSV1
- genital herpes = HSV2
Tx: clinically/scraping PCR
Give aciclovir
Describe HHV3
Varicella zoster virus
Presents as chicken pox/shingles
Transmitted through respiratory droplets
Chicken pox initially, then virus lives in neurons and when reactivated causes shingles in dermatomal distribution
Chicken pox are infective 1-2 days pre and 5 days post scabbing over
Tx: aciclovir
Prevention: vaccine for >70yr olds to prevent shingles reactivation
VSV immunoglobulin can be given to non-immune exposed and immunosuppressed individuals
Describe HHV4
EBV! Can be lytic or latent infection
See other notes
Can cause benign (IM) and malignant (lymphoma) disease
Describe HHV5
CMV (cytomegalovirus)
usually affects immunosuppressed individuals
can cause infection of the GI tract
Describe some oncogenic viruses
EBV -> lymphoma
HPV -> head/neck/vaginal/cervical cancer
HepB/C -> liver cancer
Describe TB and its risk factors for development:
Bacterial infection with mycobacterium tuberculosis
Can be dormant/active and pulmonary/extra-pulmonary
Latent = the infection without the disease, granulomas form to stop the bacteria being destroyed by immune system
What are the signs/symptoms of TB?
Primary TB -> normally asymptomatic
Post-primary TB -> infection is reactivated and symptoms present: fever/night sweats
Can affect all organ systems:
lungs -> dry productive cough, haemoptysis
lymphadenopathy
systemic -> fever, malaise, weight loss, clubbing, erythema nodosum
GI -> colicky abdominal pain, vomiting, bowel obstruction
CNS -> brain/SC/meninges infection causing neurological defects
GU -> dysuria, loin pain, haematuria, fibrosis, infertility
cardiac -> pericarditis
What are the investigations to diagnose active/latent TB?
Latent TB: - mantoux skin testing - IGRAS (interferon-Y-release assays) measure the release of If-Y from T cells reacting to the TB antigen Active TB: - blood cultures -> take 2/52 to grow and 48 days to confirm with Ziehl Nielson stain (MBT turn red) - sputum testing CXR - NAAT test
What is the treatment of TB?
RIPE!
- rifampicin -> 2/12 int, 4/12 cont. Bacteriocidal. Turns urine red, induces cytochrome P450 system
- isoniazide -> 2/12 int, 4/12 cont. Bacteriocidal. Give prophylactic pyridoxine to avoid peripheral neuropathy as it inhibits vitamin B6 formation
- pyrazinamide -> 2/12 int. Bacteriocidal. Hepatotoxic
- ethambutol -> 2/12 int. Bacteriostatic. Monitor visual acuity as it can cause colour blindness, reduced acuity and optic neuritis
Define HIV and how it can be transmitted:
retrovirus
infects CD4+ T lymphocytes and replicates
progressive immune system dysfunction, opportunistic infection and malignancy can arise
Transmission can be:
- horizontal -> blood, body fluid, sex, breast milk, needle stick
- vertical -> mother to baby
What is the pathogenesis of HIV and the enzymes involved?
- HIV expresses glycoproteins GP41 and GP120 which bind to surface receptors on CD4 cells
- virus then enters CD4 cells and releases 3 enzymes (R-TIP)
- reverse transcriptase -> carries out RT of each RNA strand forming a double helix
- integrase -> cleaves a nucleotide from the end of the viral DNA (makes it sticky), and carries it into the host nucleus to incorporate into the host DNA
- protease -> cleaves large cytoplasmic proteins to make capsid
What are the three phases of HIV infection and the signs/symptoms?
- high risk groups: MSM, black africans IVDU
3 phases: - primary HIV -> symptoms 2-4 weeks after initial infection
- persistent generalised lymphadenopathy -> ~3 months
- asymptomatic latent phase -> HIV virus continually replicates, eventually leading to AIDS
KNOW GRAPH!
What investigations should be carried out to diagnose HIV?
Bloods (low WCC?)
ELIZA = liquid IHC for the HIV Ab/Ag
NAAT/viral PCR -> used to measure viral load and response to treatment
CD4+ cell count -> monitor immune system
-> high = very infectious and symptomatic
-> low = uninfectious and treatment is working
-> <200 cells/ul = AIDS
What are the treatments for HIV?
2 NRTI and 1 drug from another class
(F-NIP)
-fusion inhibitors (stop GP-receptor binding)
-non-nucleoside/nucleoside reverse transcriptase inhibitors (inhibit RT enzyme)
-integrase inhibitors (stop action of integrase so that HIV DNA cannot be incorporated into the genome)
-protease inhibitors (stops protein fragmentation so that new capsid cannot be formed)
PEP and PrEP
- post-exposure prophylaxis (anti-retroviral medication taken <72hrs since possible exposure to prevent infection)
- pre-exposure prophylaxis (pill taken daily to prevent people at high risk of HIV from contracting it)
What complication of HIV can arise?
Acute seroconversion
Describe gonorrohoea
- caused by neisseria gonorrhoea
- causes purulent vaginal/urethral discharge + dysuria
- 50% asymptomatic
- diagnose with NAAT using vaginal swab (F) or first pass urine (M)
- treat with IM ceftriaxone and PO azithromycin
- 1/3rd pts will also have chlamydia
Describe chlamydia
- caused by chlamydia tracheomatis
- sometimes asymptomatic
- in females: dysuria, vaginal discharge, bleeding (inter-menstrual/post-coital)
- in males: discharge, dysuria
- lungs: pneumonia
- eyes: conjunctivitis
- diagnose with NAAT (using vaginal discharge (F) or first pass urine (M))
- treat with doxycycline
- short and long term complications (see notes)
Describe syphilis
- caused by treponema pallidum
- slow growing bacteria therefore long presentation
- various phases of presentation:
- > primary = 3/52 of painless non-itchy chancres on skin and genital regions
- > secondary = 3/12 of hand/skin rash
- > latent phase
- > tertiary phase = cardiac/neuro/skin symptoms
- diagnose with blood test and treat with penicillin injections
- complication -> neurosyphilis
Describe HPV
- human papilloma virus
- strains 6+11 = genital warts
- strains 16 + 18 = cervical cancer
- causes warts of throat/mouth/genitals
- treat with topical therapy/cryotherapy
- prophylactic vaccine available for males and females now
Describe trichomoniasis
- bacterial infection caused by trichomonas vaginalis
- females: profuse vaginal pain and discharge
- males: asymptomatic
- diagnose with NAAT
- treat with metronidazole
Describe bacterial vaginosis
- not a true STI but associated with STI’s
- overgrowth of bacteria naturally found in the vagina
- thin, white, fishy smelling discharge with no irritation/soreness
- 50% cases asymptomatic
- carry out gram-stain to explore vaginal flora
- treat with:
- > oral/PV metronidazole
- > PV clindamycin
Describe the aetiology and pathogenesis of malaria and the common causative agents
Plasmodium falciparum is the most common!
Other types of plasmodium also (vivax, ovale…)
A parasitic infection, with inoculation period of 1-2 weeks
Only female parasites bite
Sporazoites enter in saliva during bite, mature in liver, then move from hepatocytes into RBCs and cause clinical presentation
How does malaria present and what are its differentials?
Non specific: Fever, headaches, malaise, sweats, cough, diarrhoea, myalgia
Other travellers diseases
What investigations should you carry out if you suspect malaria?
Microscopy -> thick and thin blood film (will show ringform trophozoites) PCR antigen testing Bloods -> FBC, LFT, U&E, CRP HIV test Urine/stool microscopy and culture Serology/OCR for Dengue fever CXR Liver USS
How is malaria prevented and treated?
Prevention:
- malarone tablets
- vector control (avoid stagnant wanter, use air conditioning/nets/DEET)
Treatment = Quinine!
Name some common infections in the immunocompromised host:
- neutropenia
- chronic granulomatous disease
- pneumocystitis jerovecii
- aspergillus
- HSV
- VSV
- CMV
- stem cell transplants = GvHD
Name the 4 main causes of fever in the returning traveller
- malaria
- dengue fever
- typhoid (caused by salmonella typhi/paratyphi)
- haemorrhagic fever
What is the predominant virus causing IM?
EBV
What is the definition of pyrexia of unknown origin?
- pyrexia for >3 weeks with no identified cause after 3 days in hospital/>3 outpatient visits
What infection causes tetanus and describe it?
Caused by clostridium tetani spores (found in soil)
Enters through skin breaks and produces a neurotoxin called tetanosporin, causing muscle contraction/spasms
May present with trismus (jaw lock) or risus sardonicus (grin-like posture of hypertonic facial muscles)
What infection causes cholera and describe it?
Caused by vibrio cholerae found in faecally contaminated water
Bacteria produce cholera toxin, causes massive volumes of diarrhoea
- 75% asymptomatic
- 25% = rice water profuse watery stool
- may cause metabolic acidosis and hyperkalaemia
- treatment = hydration
What infection causes leprosy and describe it?
Caused by mycobacterium leprae
5-20 yrs incubation period
affects skin, nerves and mucous membranes: ulcers, weakness, epistaxis, sensory loss
What infection causes rabies and describe it?
Caused by rhabdovirus -> transmitted through saliva/CNS tissue usually from an infected mammal
S/Sx: odd behaviour, paralysis, agitation, fever, malaise
What infection causes roundworm and describe it?
a parasitic infection (ascariasis)
contamination of microscopic ascaris eggs in contaminated food/water
Usually asymptomatic but may notice worms in stool
What infection causes tapeworm and describe it?
a parasitic infection caused by various types of worm (taenia solium, taenia saginata)
What infection causes toxoplasmosis and describe it?
toxoplasma gondii parasite
Can be transmitted in animal faeces/raw meat
90% asymptomatic, 10% self-limiting cervical lymphadeopathy
- if immunosuppressed, disseminated disease can occur (all the -itises e.g. myocarditis, hepatitis, pneumonitis, encephalitis)
What causes lyme disease and describe it
Tick-borne, caused by borrelia burgdofen
Many people do not remember being bitten, infection appears 48-72 after attachment
Present over days -> yrs progressing from pain, itch, fever, erythema on to dermatitis and lyme arthritis
What causes measles and describe it
Highly contagious virus, now rare due to MMR vaccine
Transmitted through respiratory droplets
Common cause of encephalitis
2-4 day prodrome of fever, runny nose, diarrhoea, conjunctivitis -> then koplik spots (white spots on red buccal mucosa) present with a maculopapular rash
What causes mumps and describe it
Highly contagious virus, now rare due to MMR vaccine
Transmitted through respiratory droplets and presents with prodrome of:
- fever
- myalgia
- headache
- painful swollen and tender salivary glands
