Infectious disease Flashcards
What is tuberculosis?
-Chronic granulomatous disease
What causes tuberculosis?
-Aerobic mycobacterium tuberculosis complex
What are the 3 different mycobacterium tuberculosis complex bacteria called?
- M. Bovis
- M. tuberculosis
- M. africanum
How is tuberculosis caught?
- Spread by infected droplets coughed up by infected patients when the granulomas rupture
- Can live on environmental surfaces for long periods of time
How might a primary infection of tuberculosis present?
- Asymptomatically
- Mild flu-like illness
What is the pathogenesis of TB?
-Droplets inhaled into the alveoli of the lungs
-Macrophages engulf organisms and attempt to control them in the hilar lymph nodes
-Granulomas form
>Some bacteria are eliminated, some lay dormant, some disseminate
Why do only a small proportion of patients progress to active TB?
-The body is usually good enough to control the mycobarcterium but when someone is immunosuppressed (AIDS, long term steroids, age), the TB escapes the granulomas and spreads to the apices.
Why does active TB spread to the apices of the lungs?
-TB is aerobic and the apices receive more oxygenation
What are risk factors for TB?
- Close contact of TB patient
- Ethnic minority groups
- Homeless patients, alcoholics, drug abusers
- HIV
- Extremities of age
- Comorbid patients especially immunosuppressed
What are the systemic clinical features of TB?
-Long progressive history of:
>Fever
>Night sweats
>Weight loss
What are the pulmonary presentations of TB?
- Haemoptysis
- 3/52 productive cough
- Breathlessness
- Chest pain
How does Miliary TB present?
- Kidneys (most common extra-pulmonary site): sterile pyuria
- Meningitis
- Pott disease in lumbar vertebrae
- Addisons
- Hepatitis
- Lymphadenitis
- Arthritis
- Erythema Nodosum
What are the TB differentials?
- Cancer
- Atypical pneumonias
- Fibrotic lung disease
What should be the first thing that is done if you suspect TB in a patient?
- Allocate them a side room
- Barrier nurse with advanced masks
What investigations should be done for a patient suspected with TB?
- Chest Xray
- Ziehl-Neelsen Stain for acid fast bacilli
- Culture on Lowenstein-Jensen slope
- Rapid diagnostic nucleic acid amplification test (expensive)
How long does culture results take for TB?
- 4-6 weeks.
- If have a high suspicion and a positive Ziehl-Neelsen stain and CXR treat for TB
What colour does Ziehl-Neelsen stain turn if Tb is present?
- TB mycobacterium are aerobic acid fast bacilli and will turn red on staining.
- Other acid fast bacilli will also turn red on staining
Apart from sputum samples, what other samples should be cultured if TB is suspected?
- Lymph node biopsies
- Aspirated pus
- Early morning urine
When is the montoux test useful?
-For contact tracing. Identifies anybody with a previous exposure to the mycobacterium
What is the management for TB?
- Side room and TB
- Notify PHE
- RIPE drug treatment
What tests should be done before commencing on TB treatment?
- LFTs
- U&Es
What are the RIPE drugs?
- Rifampicin
- Isoniazid
- Pyrazinamide
- Ethambutol
How long should the RIPE drugs be taken for and why?
- 2 months: Pyrazinamide and ethambutol
- 6 months: Rifampicin and isoniazid
- Drugs only target active TB. Longer treatment time increases chance of latent TB becoming active and destroyed
Which RIPE drugs are bactericidal and which are bacteriostatic?
-Bactericidal >Rifampicin >Isoniazid >Pyrazinamide -Bacteriostatic >Ethambutol
What are the side effects of rifampicin?
-Red body secretions
-Induction of liver enzymes affecting:
>Oestrogens, steroids, phenytoin, anticoagulants
-Hepatitis
What are the side effects of isoniazid?
- Hepatitis
- Neuropathy
What drug reduces the risk of isoniazid induced neuropathy?
-Pyridoxine
What are the side effects of pyrazinamide?
- Hepatitis
- Arthralgia
- Gout
- Rash
What are the side effects of ethambutol?
-Optic neuritis
>Usually resolves if drug is stopped immediately.
What patient group is multi drug resistance likely to occur?
-HIV patients
When is treatment failure likely to happen?
- Incorrect prescribing
- Lack of compliance
How is latent TB managed in a patient without HIV?
-6/12 isoniazid OR 3/12 rifampicin + isoniazid
How is latent TB managed in a patient with HIV?
-6/12 isoniazid
What treatment should be given to patients with known contact to a TB patient?
-6/12 rifampicin
What is HIV
Human Immunodeficiency virus
How does HIV infection lead to AIDs?
-Causes the immune system to fail and not fend off infections
What is the most common HIV strain in the world?
-HIV 1
How is HIV transmitted?
-Sexual intercourse >MSM (most common) >Heterosexual intercourse (M->F usually) -IVDU -Pregnancy >placenta, delivery, breast milk -Blood transfusions
What are the 9 steps of HIV replication?
- Attachment
- Entry
- Uncoating
- Reverse transcription
- Genome integration
- Transcription of RNA
- Splicing of mRNA and translation
- Assembly of new viruses
- Budding
What is HIV formed of?
- An outer envelope
- An inner core containing RNA and RNA reverse transcriptase
What is the HIV surface glycoprotein that binds to CD4 receptors?
-GP120
What immune cells contain CD4 receptors?
- T cells
- Lymphocytes
- Dendritic cells
- Monocytes
- Macrophages
What bacteria is someone that has
a HIV infection presdisposed to?
- Penumoniae
- H. Influenzae
What is the category A section of HIV natural history?
-Primary infection or seroconversion
>Non-specific symptoms: malaise, fever, maculopapular rash, myalgia, headache, meningitis
What is the clinical latency phase?
- Mainly asymptomatic
- Lasts from 6weeks to 10 years
What happens in the category B phase?
- Rise in viral load, fall in CD4 count.
- Development of clinical features due to immunosuppression
What are some examples of category B diseases?
- Bacillary angiomatosis
- Candidiasis
- Oral hairy leukoplakia
- Herpes zoster (>1 dermatome)
- ITP
- Listeriosis
- PID
- Peripheral neuropathy
What are examples of category C diseases?
- Candidiasis of bronchi, trachea, lungs, oesophagus
- Invasive cervical carcinoma
- CMV
- Encephalopathy
- HSV
- Histoplasmosis
- Kaposi’s sarcoma
- Burkitt’s lymphoma
- TB
- PJP
- Recurrent pneumonia
- Recurrent salmonella septicaemia
- Toxoplasmosis of the brain
What are some of the clinical features of AIDS?
- Aseptic meningitis
- Retinal cotton wool spots
- Aphthous ulcerations
- Neutropenia
- HIV enteropathy
- Renal impairment
- Reduced adrenal function
- Myocarditis, cardiomyopathy
- Infections
- Coinfections ie Hep B
How is HIV diagnosed?
-Antibody assays
(detectable 6-12 weeks post infection)
-Viral genotype analysis
How is HIV monitored?
- CD4 count 3 monthly
- <200=greatest risk of HIV related pathology
- rapidly falling CD4 of <350 needs antiretroviral therapy
- HIV RNA 3-6 montly
What is a normal CD4 count?
-500
How is HIV managed?
- Drugs
- Social and psychological care
- Contacting tracing and sexual education
- Prevention of infections
What are the different types of HIV drugs?
- Nucleoside reverse transcriptase inhibitors
- Non-Nucleoside reverse transcriptase inhibitors
- Protease inhibitors
- Fusion inhibitors
- Integrase inhibitors
What is the ideal treatment combination for HIV?
-2NRTI and 1 NNRTI/protease inhibitors
What is the HIV treatment goal?
-Suppress viral load to <50 copies/ml
How do nucleoside reverse transcriptase inhibitors work?
-Inhibits synthesis of DNA by reverse transcriptase and acts as DNA chain terminators
How do non-nucleoside reverse transcriptase inhibitors?
-Bind directly to and inhibit reverse transcriptase
How do protease inhibitors work?
-Acts as competitively on HIV enzyme which prevents production of functional viral proteins and enzymes
What are some examples of nucleoside reverse transcriptase inhibitors?
- Abacavir
- Didanosine
What are some examples of non-nucleoside reverse transcriptase inhibitors?
- Efavirenz
- Etravirine
What are some examples of protease inhibitors?
- Atazanavir
- Darunavir
When should post exposure prophylaxis be taken?
- Combination of oral antiretrovirals immediately for up to 4 weeks
- Testing at 12 weeks
Where are sterile sites within the body?
- Ureter
- CSF
- Peritoneal fluid
- Pericardial fluid
- Pleural fluid
- Synovial fluid
- Bone marrow
- Blood
What are gram +ve bacteria?
- Streptococci
- Staphylococci
How are gram +ve bacteria differentiated?
- Staph = catalast +ve
- Strep = catalase -ve
What conditions can Staph. aureus cause?
- IE
- Wound infections
- Abscesses
- Osteomyelitis
- TSS
- Pneumonia
- Scalded skin syndrome
- Food poisoning (3 hour incubation period
What condition does staph. saprophyticus cause?
-UTI
What causes skin abscesses, cellulitis and tonsilitis?
-Strep pyogenes
>usually sensitive to penicillin (clarithromycin if allergic)
What does strep penumoniae cause?
Who’s more predisposed to the infections?
-CAP Predisposition: -Bronchiectasis -Asplenia -primary ciliarly diskinesia
What does strep viridans cause?
-Deep organ abscesses ie liver and brain
What class of bacteria is diptheria?
-Gram +ve
>eradicated with childhood vaccine
>notifiable disease
What is a gram -ve cocci?
-Neisseria meningitidis
What is an example of gram +ve bacilli?
-Listeria mononcytogenes
(causes meningitis in extremities of age and in the immunosuppressed)
-Treat with amoxicillin
What are examples of alpha haemolytic strep?
- Strep pneumoninae
- Strep viridans
What are examples of beta haemolytic strep?
-Pyogenes
What are examples of lactose fermenting gram -ve bacilli?
- E.coli
- Klebsiella
What are examples of non-lactose fermenting gram -ve bacilli?
- Salmonella
- Shigella
What test is required for mycobacteria?
-Ziehl-Neilson stain
How do you differentiate between shigella and salmonella in the lab?
- Shigella turns XLD agar red
- Salmonella turns XLD agar black
What infections can E.coli cause?
- Food poisoning
- UTI
- Skin wound infections
- Travellers diarrhoea
- Dysentry
What symptoms does a shigella infection present with?
- Dysentry, 30 stools a day
- If shigella toxin enters blood> can target kidney and cause haemolytic uraemic syndrome = kidney failure
How does a cholera infection present?
- From shellfish, untreated water
- Incubation period > hours to 5 days
- Rice water stool, no blood
What is pseudomonas aeruginosa and how does it present?
- Gram -ve bacilli
- Causes infections in cystic fibrosis and bronchiectasis patients
What’s the most common cause of pneumonia in COPD pts?
-Haemophilus influenza
What agar is required to grow Haemophilus influenzae in the lab?
-Chocolate agar
What condition has HiB vaccine decreased incidence of?
-Acute epiglottitis in children
What is legionella pneumophila?
- Gram -ve bacilli
- Causes legionaires disease (atypical pneumonia)
- Grows in shower heads and water tanks/taps - check travel history
What condition does bordatella pertussis cause?
-Whooping cough
>paroxysmal wheeze and cough
What classification is neisseria meningitidis?
-Gram -ve diplococcus
>common cause of meningitis
What class is neisseria gonorrhoea?
-Gram -ve coccus
What is helicobacter pylori?
- Gram -ve spiral
- Causes duodenal ulcers
- Detected by urea breath test or stool test
How is H.pylori treated?
-Metronidazole + clarithromycin + PPI
or
-Amoxicillin + clarithromycin + PPI
What class of bacteria is chlamydia? What does it cause?
- Gram -ve
- STDs, PID, resp tract infections
What are exmaples of spirochetes?
- Syphilis > 3 stages
- Lyme disease
What are the 3 stages of a syphilis infection?
- Primary stage: localised infection ie ulcer on penis
- Second stage: systemic features, skin, lymph, joints, plantar palmar rash
- Tertiary rash: neurosyphilis, CVS syphilis
What is leprosy caused by? How does it present? How is it spread?
- Mycobacteria leprae
- Causes peripheral anaesthesia due to nerve damage (may also see skin lesions)
- Spread by touch
What are the 5 antibiotics that cause C. Difficile?
- Ciprofloxacin
- Clindamycin
- Cephalosporins (cefuroxime. ceftriaxone)
- Co-amoxiclav
- Carbapenams
What is hameolytic uraemic syndrome?
-Seen in young children.
-Triad of:
>Acute renal failure
>Microangiopathic haemolytic anaemia
-Thrombocytopenia
What are the causes of haemolytic uraemic syndrome?
- Post dystentery
- Tumours
- Pregnancy
- Ciclosporin
- The pill
- SLE
- HIV
How is haemolytic uraemic syndrome investigated?
- FBC: anaemia, thrombocytopenia, fragmented blood film
- U&E: raised CR, raise urea
- Stool culture: +ve E. coli
How is haemolytic uraemic syndrome managed?
-Supportive Rx: fluids, blood transfusion, dialysis if required
What are features of Legionnaire’s?
- Flu like symptoms (inc. fever)
- Dry cough
- Bradycardia
- Confusion
- Lymphopaenia
- Hyponatramia
- Deranged LFTs
- Pleural effusion
How is legionnaires diagnosed?
- Urinary antigen for for Legionella
- CXR
- Sputum culture
How is Legionnaire’s treated?
- Erythromycin
- Notifiy PHE
What are features of gonnorrhoea?
- Males: urethral discharge, dysuria
- Females: cervicitis: vaginal discharge, bleeding, dyspareunia
What are some local complications that can result from gonorrhoea infections?
- Urethral strictures
- Epididymitis
- Salpingitis
What are some systemic features of gonnorhoea?
- Gonococcal arthritis
- Tenosynovitis, migratory polyarthritis, dermatitis
How is gonorrhoea treated?
-Ceftriaxone 50mg IM
+ azithromycin 1g PO
What are the features of chlamydia?
- Asymptomatic
- Women: Discharge, bleeding, dysuria
- Men: urethral discharge, dysuria
What are the complications of a chlaydia infection?
- Epididymitis
- PID
- Endometriosis
- Increased incidence of ectopic pregnancies
- Infertility
- Reactive arthritis
How is chlamydia investigated?
-Nucleic acid amplification tests of 1st void urine sample or vulvovaginal swab
How is chlamydia treated?
- Azithromycin 1g PO
- Contact tracing
How is syphilis treated?
-Benzylpenicillin
doxycycline if allergic
What is BV?
-Overgrowth of anaerobic organisms ie gardnerella vaginalis
What are the features of BV?
-Fishy offensive smell
What are the Amels criteria for diagnosing BV?
- Thin, white discharge
- Clue cells in microscopy
- Vaginal pH >4.5
- Positive whiff test
How is BV managed?
-Oral metronidazole 5-7 days
What are implications of BV in pregnancy?
-Increased risk of:
>preterm labour
>low birth weight
>late miscarriage
Which UTI abx should be used in pregnancy? and in breast feeding?
- Pregnancy: nitrofurantoin
- Breastfeeding: trimethoprim
What are the presenting features of trichomonas vaginalis?
- Vaginal discharge: offensive, yellow/green/ frothy
- Vulvovaginitis
- Strawberry cervix
How is trichomonas vaginalis managed?
-Oral metronidazole
What infectious disease can be caught by travel?
- Infective gastroenteritis
- Malaria
- Hepatitis
- Legionella
- Typhoid
- Rabies
- Ebola
What infections do sewage workers get?
- Leptospirosis (from rat urine)
- Gastroenteritis
- Hepatitis
What diseases do farm workers get?
- Orf
- Coxsackie
- Coxiella
What diseass are seen in commercial sex workers?
- STI
- HIV
- Hep B
What diseases are health care workers at increased risk of?
- Hep B
- RTI
- Infectious diarrhoea ie norovirus
What disease can be seen in trekkers?
-Lyme disease
What infections can be caught in restaurants?
- Salmonella
- Campylobacter
Which infectious disease can be caught from shellfish?
- Hep A
- Yersinia
What diseases can be caught from dirty water?
- Hep A & E
- Cholera
- Dysentery causing bacteria
Which infections are patients prone to if they’ve had a splenectomy?
-Pneumococcal sepsis
Which infections are post-transplant pts prone to?
- CMV
- Apergillus
- Fungal infections
- Pneumocystis jiroveci
Which infections are HIV pts at risk of?
- PCP
- Toxoplasma
- Cryptococcus
- Candidiasis
What is an alternative of BenPen for someone who is penicillin allergic with suspected meninigitis?
-Chloramphenicol
What are the possible causes of bacterial meningitis?
- Neisseria meningitidis
- Strep pneumoniae
- Listeria monocytogenes (elderly, babies, immunosuppressed)
What is the most common cause of viral meningitis?
-Enterovirus
What transmits malaria?
-Femal anopheles mosquito transmits plasmodium protozoa
What is the most common plasmodium speciest to cause malaria?
-Plasmodium flaciparum
Where is malaria most common?
- Sub-saharan Africa
- Central Asia
- Eastern Europe
- South East Asia
Risk factors for malaria?
- Travel to endemic area
- Low socioeconomic status
- Young children and infants
- Pregnancy
- Elderly
- Outdoors between dusk and dawn
What are protective factors against malaria?
- Sickle cell trait
- G6PD deficiency
Features of severe malaria?
- Temp >39
- Headache
- Myalgia
- Parasitaemia
- Hypoglycaemia
- Acidosis
- Severe anaemia
- Presence of complications
Signs of malaria?
- Fever
- Splenomegaly
- Hepatosplenomegaly
- Jaundice
Complications of malaria?
- Cerebral malaria: seizures, confusion, coma, death
- Acute renal failure: black water fever due to intravascular haemolysis
- ARDS
- Pulmonary oedema
- Hypoglycaemia
- DIC
Differentials of malaria?
- Typhoid
- Hepatitis
- Dengue fever
- Influenza
- HIV
- Meningitis
- Viral haemorrhagic fever
investigations for suspected malaria?
- Thick and thin blood fims with Giemsa stain
- Rapid diagnostic tests
- FBC: thrombocytopenia, anaemia
- LFTs: abnormal
- U&E: hyponatraemia, ^Cr
How can malaria be prevented?
- Deet
- Mosquite nets
- Long clothes
- Avoid dusk/dawn
- Short term antimalarials: malarone, doxycycline
- Long term antimalarials: Mefloquine, proguanil
1st line Treatment for severe malaria?
-IV artesunate
How does lyme disease present?
- Erythema chronicum migrans 9migrating redness from tick bite)
- Systemic features: fever, arthralgia
- CVS: heart block, myocarditis
- Neuro: CN palsies, meningitis
How is lyme disease treated?
- Oral doxycycline
- Ceftriaxone in disseminated disease
Most commo cause of infective gastroenteritis?
-Campylobacter
How is gastroenteritis investigated?
- Stool sample
- Vital signs
- Assess for dehydration
- FBC, U&E
Treatment for gastroenteritis?
- Normally self limiting. Suportive therapy.
- Analgesia for stomach cramps
If someone works with food and acquires food
poisoning, what action needs taking and when can
they return to work?
- Notify PHE
- 3x -ve stool samples before returnign to work
- 48 hours minimus before returning to work/school
What is cellulitis?
- Inflammation of the skin and subcutaneous tissue
- Typically caused by strep pyogenes or staph. aureus
Features of cellulitis?
- Commonly occurs on the shins
- Erythema
- Pain
- Swelling
How is cellulitis investigated?
- Rule out DVT
- Mark borders
- Swab if exudative
- Blood cultures
Treatment for cellulitis?
- Flucloxacillin
- Sever: IV BenPen and Flucloxacillin
What dangerous condition should be a differential of cellulitis?
-Necrotising fasciitis
What red flag feature points towards nec. fasciitis?
- Severe pain out of proportion with the affected area
- Extremely unwell pt
What is nec. fasciitis?
-Inflammation of the fascia of muscles or other organse and results in rapid destruction of overlying tissues
Features of nec. fasciitis?
- Acute onset
- Painful erythematous lesion
- Extremely tender over infected tissue
- Bubble wrap (subcut emphysema)
- Systemically unwell
Management of nce. fasciitis?
- ABCDE
- surgeons for surgical debridement
- Broad spec IV abx (clindamycin)
What are the main einfective causes of jaundice in the UK?
- Hep B
- Hep C
- Ascending cholangitis
What are features or erythema multiforme?
- Hypersensitivity reaction commonly triggered by infection
- Target lesions seen on bank of hnads and feet and then spread to torso
- Upper limbs > lower limbs
Causes of erythema multiforme?
- Viruses
- Idiopathic
- Bacterial ie mycoplasma, strep
- Drugs: penicillin, carbamazepine, allopurinol
- Connective tissue disease: SLE
- Sarcoidosis
- malignancy
What are the features of mycoplasma pneumonia ?
- Prolonged and gradual onset
- Flu like prodrome and dry cough
- Bilarteral consolidation on x ray
What are some complications of mycoplasma pneumoniae?
- Haemolytic anaemia, thrombocytopenia
- Erythemia multiforme
- Meningoencephalitis, GBS
- Painful vesicles on tympanic membrane
- Pericarditis
- hepatitis
- acute glomerulonephritis
How is mycoplasma pneumonia treated?
-erythromycin/clarithromycin
Which vaccines are live attenuated?
-BCG
-MMR
-Oral polio
-Yellow fever
-Oral typhoid
(AVOID if on immunosuppressants)
Which infective organism is most common cause of chronic wound infections?
-Pseudomonas aeruginosa