Infectious diseases Flashcards
What are some congenital and acquired causes of immunocompromise?
Congenital: B-cell defect, T-cell defect, Complement deficiency, phagocyte deficiencies
Acquired: Malnutrition, HIV, Diabetes, Drugs, Cancer
Give some examples of neutropenic defects causing immunosuppression.
Aplastic anaemia
Chemotherapy (doxorubicin, cyclophosphamide)
Leukaemia
Give some examples of cell defects causing immunosuppression.
Chemotherapy (azathioprine, bleomycin)
HIV/CMV/EBV infection
Malnutrition
Lymphoma
Give some examples of humoral defects causing immunosuppression.
Multiple myeloma
Chronic lymphocytic leukaemia
Chemotherapy (Azathioprine, methotrexate)
Splenectomy
What is infectious mononucleosis?
Glandular fever
Triad of fever, pharyngitis, lymphadenopathy with atypical lymphocytosis
Caused by Epstein Barr virus via saliva
What is pyrexia of unknown origin?
A temperature of >/=38.3 degrees for >/=3 weeks with no identifiable cause after 3 days of hospital evaluation or 3 outpatient visits.
Infection, inflammation, neoplastic, miscellaneous
What blood results may help aid a diagnosis of malaria?
Hypoglycaemia, acidosis and anaemia
What are some complications of severe malaria?
Shock, renal failure, severe anaemia, acidosis, pulmonary oedema
What are the types of plasmodium that cause malaria?
Plasmodium Falciparum- most common cause of severe malaria. Drug resistant
Plasmodium vivax - persistent liver infection, can relate months after initial infection, chloroquine resistant
Plasmodium ovale - persistent liver infection, no drug resistance
Plasmodium malaraie - no liver infection and no resistance
What is Viral Haemorrhagic fever?
A group of serious illness caused by particular viruses.
Ebola, Lassa fever, Marburg, Crimean-congo fever
How does VHF cause illness?
The virus invades the body and lives in macrophages and dendritic cells where it multiples.
It then disseminates into organ systems
This triggers the innate immune response and cytokines and NO is released.
Replication and tissue damage and there is increased permeability of the vessels - DIC
What is dysentry?
Infection of the intestine causing diarrhoea containing blood and mucous
Bacillary caused by Shigella
Ameobic caused by entameobic histolytica
What are some differences in dysentry caused by shigella and caused by entameobic histolytica?
Shigella - 10 loose movements a day with small amounts of stool. Fresh blood coloured and no odour. more pus and mø - risk of HUS
Ameobic - 6-8 loose movement but copious amounts of stool which is dark with a foul odour. more eosinophils and red cell clumps.
What is Leprosy?
Also known as Hansens disease.
A chronic infection with mycobacterium leprae characterised by one or more of the following:
- Hypopigmented or erythematous skin lesions with loss of sensation
- Peripheral nerve damage -> loss of sensation
- Muscle weakness in hands, feet or face
- Paraesthesia (tingling of hands and feet)
What is cholera?
A secretory diarrhoeal illness caused by the gram -ve comma shaped bacilli vibrio cholerae bacteria.
Cholera Enterotoxin stimulate continuous stimulate of adenylate cyclase causing water to be secreted from the intestinal cells in to the lumen and then salt follows. (small bowel)
Shock, dehydration, vomiting, RICE WATER STOOL*, circulatory collapse.
Give IV fluids
What is meningitis?
Inflammation of the meninges (± cerebrum is encephalitis)
Usually a triad: Fever, nuchal rigidity, altered mental state
Meningiococcal rash (non-blanching petechial rash)
(Confusion indicated encephalitis)
What bacteria can cause meningitis?
Nesseria meningitdis - Gram negative diplococci
Streptococcal pneumonia - Gram positive diplococci
Listeria monocytogenes - Gram positive rod
70% of patients with streptococcal pneumoniae caused meningitis have underlying disease, give some examples.
Middle ear disease Head injury (CSF leak) Alcohol Neurosurgery Immunocompromised
What signs are diagnostic of meningitis?
Kernig’s sign - Inability or reluctance to fully extend the knee when the hip is flexed at 90 degrees.
Brudzinskis sign - Spontaneous flexion of the hips when the neck is passively flexed. Examines nuchal rigidity
When might a LP be contraindicated?
GCS=12, papilloedema, immunocompromised, seizures, Coagulopathy (INR>/=1.5), Infection if LP site or abscess, Severe sepsis, respiratory or cardiac compromise
From CSF results how can you tell a bacterial and viral meningitis apart?
Bacteria: Neutrophils - Raised protein, reduced glucose. Cloudy
Viral - Lymphocyes - Raised protein, normal glucose. Clear
How would you treat bacterial meningitis?
N. meningiococcal - IV Ceftriaxone 2g/12hours for 5-7 days
S. pneumococcal - IV Ceftriaxone 2g/12h for 10-14 days
L. monocytogenes - IV Amoxicillin 2g/4h for 21 days
If penicillin allergy - Chlorampenicol (for ceftriaxone) and Co-trimoxazole (for amxo)
PLUS
IV dexamthasone** 10mg/6hr for 4 days
What prophylaxis can you give for someone in contact with someone with meningitis?
Rifampicin or Ciprofloxacin
What are some complications of meningitis?
Purpura fulminants
Deafness (CN palsies)
Seizures
What is progressive multifocal leukoencephalopathy?
Progressive motor dysfunction
Clumsiness, trouble speaking, Partially blind, AMS
Due to JC virus
In immunocompromised, HIV, anti-TNF, transplant
What is Tuberculosis?
A bacterial infection passed on by inhaling tiny droplets from the cough or sneeze of an infected person. Bacilli - Mycobacterium tuberculosis
What is latent TB?
You have the bacteria but it is dormant, surrounded by immune cells in an ceaseating granuloma. It is not transmissible in this stage
How might TB present?
90% have pulmonary TB: Haemoptysis, SoB, cough, sputum
CONSTITUTIONAL SYMPTOMS V IMPORTANT**
Weight loss, night sweats, malaise, loss of appetite, fever and chills, lymphadenopathy, fatigue
What are some high risk factors for TB?
Silicosis, AIDS or HIV and not on antiviral therapy, CKD requiring dialysis, TNF inhibitors, immunosuppressed
What CXR findings are shown in TB?
Consolidation, cavitation, fibrosis, calcification
What is shown on a TB histology?
Caseating granuloma
How would you investigate for TB?
- Mantoux test/ tuberculin skin test (TB antigen injected intradermally, strong +ve indicates active TB. +ve if immunity or had BCG)
- If this is +ve - Interfernon gamma release assay
- If CXR suggests TB - >/=3 sputum samples with at least one form early morning before starting treatment. Use for MC&S for Acid fast bacillus resistance
- Quantiferon TB gold - measures delayed hypersensitivity developed after contact with TB
- PCR and culture of fluids if not pulmonary
What treatment is used in TB?
2 months of all 4 drugs then 4 more months of RI
RIPE
Rifampicin - 600mg PO 3x wk
Isoniazid - 15mg/kg PO 3x wk - give with pyridoxine 10mg/24h for peripheral neuropathy
Pyrazinamide - 2.5g PO 3x wk
Ethambutol - 30mg/kg PO 3x wk
List the SE of the TB drugs.
Rifampicin - Orange bodily secretions, Increases LFTs, decreases platelets. Interfere with warfarin and OCP
Isoniazid - Vit B6 def (dermatitis), peripheral neuropathy, increases LFTs
Pyrazinamide - gout, raised lactate, arthralgia, hepatitis
Ethambutol - Toxic optic neuropathy
What are teh 4 populations of cells in TB and which antibiotic targets them?
Actively growing - isoniazid
Dormant
Semi-dormant but inhibited by an acid environment - pyrazinamide
Semi-dormant with spurts of active metabolism - rifampicin
Multi-drug resistant TB is resistant to isoniazid and rifampicin, what treatment can u give?
Pyrazinamide + 4 second line agents
- Fluoroquinolone
- Injectable - amikacin, kanamycin
- Ethionamide
- cycloserine
What does AIDS mean?
Its a combination of potetially life-threatening infections and cancers that develop when someones immune system has been damaged by HIV
How might you diagnose HIV?
Viral load - aim of tx is to keep it at an undetectable level - <200 copies /mL
CD4 count - Lower means you are at risk of opportunistic infection. <200 cells/mm3 is bad.
If you have an undetectable viral load for 6 months and continue with treatment you are not at risk of passing it on during sex
HIV is managed by highly active anti-retroviral treatment. What does this include?
triple therapy
2 nucleoside/nucleotide reverse transcriptase inhibitors
+ 1 other drug class
(Non-nucleoside reverse transcriptase inhibitor, protease inhibitor, integrase inhibitor)
What treatment is available to prevent HIV?
PEP - post-exposure prophylaxis - then 72 hours after for 28 days. IF high risk
PrEP - Pre-exposure prophylaxis - for high risk
What is septic arthritis?
Inflammation of the synovial membrane of a joint, with effusion into the joint capsule, due to infection.
Most commonly in younger adults with unilateral joint - S.aureus or N.gonnorrhoea
How might bacteria get into a joint and cause septic arthritis?
Haemtogenous spread
Disseminated from osteomyelitis
Spread from adjacent or local soft tissue infection
Therapeutic or diagnostic measures
Penetrating damage from a puncture or trauma
What results from synovial fluid of a joint might indicate septic arthritis?
> 75% neutrophil polymorphs
50,000 WBC/mm3
Low glucose
Positive culture
You need antibiotics that penetrate the bone in treating septic arthritis, list some that can.
Rifampicin, Tazocin, cephalosporin, ciprofloxacin, clindamycin, carbapenems, doxycycline, clindamycin
What is gastroenteritis?
Inflammation of the stomach and the intestines, usually due to an infective source
What are the most common causes of gastroenteritis?
Camplyobacter is the most common cause in the UK
E.coli is the most common cause in travellers **
Norovirus is the most common viral cause (usually on cruise outbreaks)
What is Sjögrens syndrome?
Autoantibodies to the exocrine glands (salivary lacrimal)- Dry eyes and mouth.
Many present with non-specific Sx like arthralgia, chronic fatigue, vaginal dryness, liver problems.
May be Anti-Ro or Anti-Ia
At an increased risk of NHL
What test can be used to test for Sjögrens?
Schirmers test - measures eye moisture with blotting paper
What is antiphospholipid syndrome and how is it diagnosed (clinically)?
Following a thrombotic event and the presence of anti-phospholipid antibodies at 2 different times with no clear causative infection
What dermatological feature may help indicate anti-phospholipid syndrome?
Levido reticularis skin rash
What is the characteristic syndrome in Scleroderma?
CREST syndrome Calcincosis Reynolds phenomenon (1st to present) Oesophageal dysfunction Sclerodacytly Telangiectasia
What antibodies may be present in scleroderma?
Anti-centromere (ANA) in limited cutaneous disease
Anti-ScL70 in diffuse
How might you treat scleroderma?
IV cyclophosphamide Monitor Bp (Watch for pulmonary HTN) and Renal function (incase of renal failure)
What is myositis and what are the types?
A rare autoimmune conditions. Insidious onset progressive, symmetrical, proximal muscle weakness, muscle inflammation with myalgia ± arthralgia.
Muscle weakness may cause dysphagia, dysphonia and respiratory muscle weakness.
What is dermatomyositis and what are some important clinical features?
Muscle weakness that follows a rash
- Malar rash - Shawl sign (+ve over shoulders and back)
- Heliotrope rash on eyelids and oedema
- Gottrons papules - violaceous papules over the knucle
What type of bacteria is C.diff (and all clostridium)?
Anaerobic, spore forming, gram positive bacilli
When might C.diff infection occur?
When the normal bowel flora has been disrupted nu recent antibiotic use
What antibiotics can lead to C.diff infection?
Clindamycin, co-amoxiclav, cephalosporins, ciproflocaxin
Ampicillin, Carbapenems, fluoroquinolones
What are the severity markers for a C.diff infection?
WCC >15 x10^9 Colonic dilation > 6cm Immunosuppression Creatinine > 1.5 x baseline Temperature >38.5
How would you treat C.diff?
Mild-moderate
Severe
life threatening / fulminant
mm - *Metronidazole PO 400mg 10-14days
severe - PO 125mg Vancomycin qds
Fulminant - PO Vancomycin 500mg qds + IV metronidazole 500mg tds
Clostridium Botulism can be got from canned food or honey in infants, what is the consequence of its infection?
Neuromusclar blockade - FLACCID PARALYSIS* and progressive muscle weakness,
chest muscles and diagram weaken - respiratory failure
Difficulty speaking, swallowing, breathing
Drooping of eyelids, double vision, facial muscle weakness
What causes the GRAM -VE SPIROCHETE syphillis and how would you treat it?
Treponema pallidum
Benzathine penicillin IM
How would you distinguish primary, secondary and tertiary syphillis?
Primary - 9-90 days after infection. Chancre (painless ulcer), clear fluid, single ulcer
Secondary - 3 months - 2 years after - rash - Prink/brown macules on the palms and soles of feet. Fever, lymphadenopathy, hepatitis, CN palsies, meningitis, GN
Teritary - Neurosyphillis, gummatous syphillis
What treatment is given for infection with the GRAM -VE DIPLOCOCCAL nesseria gonorrhoea?
Ceftriaxone 1g IM and PO azithromycin
How would you test for chlamydia or gonorrhoea?
Nucleic acid amplification test
(vaginal swab or men - urine)
McCoy cells on rectal microscopy
How would you treat chlamydia trachomatis?
Doxycycline 100mg bd 7 days
or Azithromycin
Give some examples of beta lactam antibiotics and what is their MoA?
They bind to the penicillin binding protein and inhibit cross linking of the peptidoglycan cell wall causing lysis of the bacteria. - Bactericidal
Penicillins (benzylpenicillin, flucloxacillin)
Carbapenems (meropenem)
Cephalopsporins (ceftriaxone, cefixime)
Monobactam (Aztreonam)
What are some side effects of beta lactam antibiotics?
Nausea and vomiting, diarrhoea, cholestasis
Hypersensitivity - T1 - urticaria or T4 - anaphylaxis
What are some side effects of the glycopeptide vancomycin?
Nephrotoxicity at higher doses
Ototoxicity rare
Red man syndrome if infected to fast
Give some examples of protein synthesis inhibitors and the types.
50s ribosomal subunit inhibitors - Macrolides (erythromycin, clarithromycin, azithromycin) clindamycin, chlorampenicol
30s ribosomal subunit inhibitors - Aminoglycosides (gentamicin), Tetracycline (Doxycycline)
Give some side effects of macrolides.
QT prolongation
Hearing loss with long term use
Vomiting and diarrhoea
Clarithromycin had over 400 drug interactions such as simvastatin and warfarin
What are some side effects of chloramphenicol?
Optic neuritis, aplastic anaemia, bone marrow suppression
used as topical therapy for eyes
Give some side effects of the tetracycline doxycycline.
Tooth discolouration and bone abnormalities
Avoid in children and pregnant women
What are some SE of the folate inhibitor trimethoprim?
Elevation in Sr K
Elevation in Sr Cr
Rash and Gi disturbances
What is it called when TB is in the spine?
Potts disease
What might TB look like on CXR?
Gohns complex - ceasating necrosis **
Cavitation, consolidation, calcification, fibrosis
What bacteria might present with bloody diarrhoea, oliguria and haemolytic anaemia?
E.coli 0157 - HUS
Triad - low plts, AKI, MAHA
What bacteria is associated with reheated fried rice?
Bacilus cerus
Aerobic spore forming gram +ve bacilli
What bacteria causes RED current jelly sputum?
Klebsiella - common in alcoholics
Define fever and hypERthermia.
Fever: Physiological response where there is increased body temperature due to the resetting of the normal hypothalamic set point
HypERthermia: Elevated body temperature above the hypothalamic set point - usually due to loss of thermoregulation
Give some examples of causes of PUO.
CMV, EBV, HIV, TB, malaria, abscesses
SLE, Vasculitis, IBD, sarcoidosis, AI hepatitis
Renal cell Ca, lymphoma, leukaemia, hepatic mets
Drug fever, hyperthyroidism, PE
What causes tetanus and what is the triad?
Clostridium tetni - exotoxin
A life-threatening neurological syndrome with tonic muscle spasms and hyperreflexia
Triad: Trismus (locked jaw), Risus Sardonicus (grin caused by facial muscle spasm), opisthotonos (Severe simultaneous spasm of all the muscles)
In a high risk patient who is travelling they can be given prophylactic Abx to present gastroenteritis, what abx can be given?
Ciprofloxacin
In those immunocompromised, CKD, ileostomy
What is healthcare facility onset C.diff infection?
C.diff infection that occurs more than 3 days after admission
What is community onset C.diff?
C.diff infection with no documented overnight stay in a hospital facility over the prior 12 weeks
What is community onset, healthcare facility associated C.diff?
C.diff infection occurring within 28 days after discharge from a healthcare facility
What structure causes MRSA?
Penicillin binding protein 2A encoded by mecA gene
This allows growth of the organism in the presence of beta lactams
Methacillian resistance is defined as an oxacillin min inhibitory conc >/=4
What can be found in a patients blood who has been newly infected with HIV?
p24 antigen - makes up most of the HIV viral core
Only present after infection but before seroconversion due to the production of ab which destroy it
What is the most common STI?
HPV - ano-genital warts
chlamydia is the most common bacteria STI
What is a complication of chlamydia?
LGV - Lymphogranuloma venereum
A painless genital ulcer
Where might you get infected with the gram positive coccobacilli Listeria monocytogenes?
Ready meals, unpasteurised milk, pate, soft cheeses
Initially flu like illness then spreads in blood stream causing meningitis or septicaemia
Can also cause over abscesses, hepatits and perinatal consequences
The gram negative bacilli shigella dysenteriae is associated with HUS*, explain how.
Attaches to terminal ileum and colon. Shiga toxin damages the intestinal epithelium and some target teh glomerular epithelium causing renal failure - HUS
Rice water stool can be caused by the comma shaped gram negative bacilli vobro cholera, what is a consequence of this?
Metabolic acidosis, hypokalaemia, hypovolaemic shock, cardiac failure
What might cause diarrhoea due to infection of contaminated fish and shellfish in warm costal waters?
Vibro parahaemolyticus
What are some complications of infection with the curved gram -ve bacilli Campylobacter jejuni?
Toxic megacolon, bacteraemia, reactive arthritis, guillian barre
