Infectious diseases (Disease summaries) Flashcards

Question

course of illness: typhoid

Answer 1

Incubation period: 7-14 days

Answer 2

* Initially systemic upset – fever, headaches, malaise, nausea, anorexia * Relative bradycardia (sphygmothermic dissociation or Faget sign) * Gastrointestinal symptoms – typically pain and constipation (although Salmonella gastroenteritis can cause diarrhoea, enteric fever is associated with constipation) * Rose spots – these are small red macules on the skin of the trunk due to bacterial skin emboli * Since it can infiltrate the bone marrow, osteomyelitis can occur, especially in people with sickle cell disease. Other features can include dehydration, peritonitis, pneumonia, encephalitis, pericarditis, and metastatic abscesses (including the liver, spleen, and heart).

Answer 3

Also known as sphygmothermic dissociation or the Faget sign, this describes fever and bradycardia/unusually low tachycardia, which is the opposite of what is expected (i.e. fever and tachycardia). This sign is associated with intracellular parasites and viral haemorrhagic fever such as typhoid fever, yellow fever, Legionella infection, Q fever, and dengue fever.

Answer 4

Blood, urine and stool **culture** x 2 * Blood (+ve in 40-80%) FBC * Moderate anaemia * Relative lymphopenia, raise CRP * Raised LFTs (transaminase and bilirubin) No serological test

Answer 5

Ceftriaxone (resistant starting- having to use meropenem)

Answer 6

* Vaccine * Eating and drinking

Answer 7

* Food poisoning salmonellas * Widespread distribution including UK e.g. S. typhimurium, S enteridis Symptoms * Diarrhoea * Fever * Vomiting * Abdominal pain Management * Generally self limiting but bacteraemia and deep-seated infections may occur in the immunosuppressed

Answer 8

- Norovirus - Campylobacter - E.coli - Clostridium difficile - Shigella - Bacillus cereus - Cholera - Cryptosporidiosis - Amoebiasis - Giardiasis

Answer 9

* The **most common** bacterial infection of the intestines in the UK * Associated with contaminated food, especially undercooked poultry * Features: flu-like prodrome (e.g. fever, malaise, myalgia) followed by diarrhoea that may be **bloody**, abdominal cramps, nausea, and vomiting. * Usually self-limiting within 2-3 days and resolves within 7 days

Answer 10

* Commonly associated with **foreign travel** * Transmitted through contaminated food via the faecal-oral route * Features: watery stools, abdominal cramps, nausea * Certain strains can cause haemolytic uraemic syndrome * Usually self-limiting and resolves within 10 days

Answer 11

* Transmitted through contaminated food that has been undercooked, classically undercooked reheated **rice** * Features either acute vomiting within ~6 hours (emetic syndrome) or diarrhoea within ~6 hours (diarrhoeal syndrome) however they can overlap * Usually self-limiting and resolves within a day

Answer 12

* Usually caused by recent broad-spectrum antibiotic use, most commonly due to cephalosporins, but also clindamycin * Features: diarrhoea, abdominal pain, pseudomembranous colitis

Answer 13

* Transmitted via the faecal-oral route, often from person-to-person and usually seen in young children (<5 years old) * features: bloody diarrhoea and mucus, along with fever, abdominal cramps, and may have nausea and vomiting. * Usually resolvers within 7 days

Answer 14

Vibrio cholerae * Associated with poverty and may be seen in returning travellers, particularly drinking untreated water, eating contaminated food, or unsanitary living conditions * Features: profuse, watery diarrhoea (‘rice water’ stools that are greyish, cloudy, with mucus) – litres are often lost causing severe dehydration

Answer 15

* The most common protozoal intestinal infection in the UK and associated with foreign travel, transmitted via contaminated food/water * Features: watery diarrhoea, abdominal cramps, nausea, vomiting, and fever * Symptoms usually last 1-2 weeks

Answer 16

stool: modified **Ziehl-Neelsen** stain (acid-fast stain) of the stool may reveal the characteristic **red cysts**

Answer 17

* is largely supportive for immunocompetent patients * if the patient has HIV and is not on antiretroviral therapy then this should be started and often will be enough to resolve the infection * nitazoxanide may be used for immunocompromised patients * rifaximin is also sometimes used for immunocompromised patients/patients with severe disease

Answer 18

* Transmitted via the faecal-oral route, usually seen in foreign travel, and has a long incubation period (>1 week) * Features: can cause amoebic dysentery (bloody diarrhoea and fever) and possibly an **amoebic liver abscess** (right upper quadrant pain, constitutional symptoms, and hepatomegaly)

Answer 19

* Stool OCP (Ova Cyst Parasite) * Not shed constantly, need x 3 stools * Usually absent with invasive disease * Amoebic serology, stool PCR

Answer 20

* IV ceftriaxone (gram positive and negative) * PO metronidazole (anaerobic infections and amoebic) * US guided hepatic train

Answer 21

* Transmitted via the faecal-oral route and has a long incubation period (>1 week) * Features: chronic non-bloody diarrhoea that is initially watery but can lead to steatorrhoea over time, malabsorption, weight loss, and lactose intolerance * Giardiasis should be considered in someone with chronic diarrhoea associated with malabsorption and weight loss.

Answer 22

Tuberculosis (TB) is an infection caused by Mycobacterium tuberculosis. It is spread through inhaling respiratory droplets. TB is a notifiable disease. **Active tuberculosis** – when evidence of symptomatic/progressive disease of the lung and/or other organs. If untreated, one person with active pulmonary TB can spread the infection. **Latent TB** – a persistent immune response to TB antigens without clinical evidence of active TB. The person is asymptomatic but not infectious. It may reactivate, and cause active TB.

Answer 23

* Endemic in parts of Asia, Africa, SA and eastern Europe and was common in the UK until the 1950s (when isoniazid was first developed) * Common for people immigrating to the UK for endemic areas to experience reactivation of latent TB after their arrival (maybe Vitamin D deficiency)

Answer 24

Mycobacterium tuberculosis (acid fast stain)

Answer 25

* Transmitted by aerosol inhalation and causes pulmonary infection, then spreads via haematogenous spread to any site in the body * Initial infection can be asymptomatic and then lie dormant (Latent TB) for many years before reactivating later in life to the active infection * Reactivation risk (10-15%) due to immunosuppression, advancing age or HIV)

Answer 26

Upon entering the lungs, Mycobacterium tuberculosis infects the lungs and can proliferate within alveolar macrophages, resulting in tubercle-laden macrophages known as a **Ghon focus**. These combined with hilar lymph nodes form **Ghon complexes.** In immunocompetent people, the initial lesion heals by fibrosis. However, those who are immunocompromised may develop disseminated TB.

Answer 27

If the person becomes immunocompromised (e.g. HIV), the infection can reactivate, which often happens in the lung apex and can spread. The most common area of secondary infection is the lungs. If bacteraemia occurs in primary/secondary infection, then deposits of bacteria can occur in different organs, which can also reactivate, resulting in disseminated infections. Sites that may be affected include spinal TB (osteomyelitis), TB meningitis, TB pericarditis, and abdominal TB.

Answer 28

symptoms that are seen in regions outside of the lungs, including the meninges, lymph nodes, bones and joints, heart, eyes, and gastrointestinal system etc.

Answer 29

when ≥2 organ systems are affected which is more common in children and immunocompromised people, however, it can occur in the absence of immunodeficiency.

Answer 30

a strain of TB that is resistant to two first-line drugs. Taking the wrong dose or combination, or irregularly can increase the risk of this. Extensively drug-resistant TB may occur if further resistance occurs.

Answer 31

* Living in an endemic area (e.g. Asia, Africa, Eastern Europe, Latin America) * Exposure to a person infected with TB * HIV – the risk of developing active TB is 20-30 times more likely * Immunocompromised states – including immunosuppressive treatment and diabetes mellitus * Lung fibrosis – including silicosis and apical fibrosis * Young children – are more likely to develop severe disease * Poverty and deprivation – including hostels, shelters, prisons etc. * Alcohol * Intravenous drug use * Smoking

Answer 32

Constitutional symptoms * fever * weight loss * drenching night sweats * malaise * anorexia Pulmonary symptoms * cough * sputum * dyspnoea * haemoptysis (a late sign)

Answer 33

* Clubbing * Cachexia * Lymphadenopathy * Hepato/splenomegaly * Erythema nodosum * Crepitation or bronchial breathing if PE

Answer 34

* Skin involvement – erythema nodosum (occurs due to a TB hypersensitivity reaction), lupus vulgaris (painful nodular lesions on the face) * Lymphadenopathy – often painless, rubbery, and in the supraclavicular and cervical regions * Neurological involvement – headache, vomiting, confusion, cranial nerve palsy * Skeletal/joint involvement – bone/joint pain, joint swelling, back pain * Abdominal involvement – abdominal/pelvic pain, constipation, bowel obstruction * Urinary involvement – dysuria, polyuria, haematuria

Answer 35

**Chest X-ray:** * may show hilar lymphadenopathy, cavitation, and pleural effusion * Upper lobe cavitation can suggest reactivated TB * Features tend to affect the upper lobes **Sputum smear** – should be done with 3 specimens: - The sample is stained with the Ziehl-Neelsen stain for acid-fast bacilli - This is non-specific as it will stain positive for all Mycobacteria species **Nucleic acid amplification tests (NAAT):** - Allows quicker diagnosis within 48 hours, but is less sensitive than culturing **Sputum culture** – the gold-standard test: - This also can assess drug sensitivities, however, takes 1-3 weeks **HIV testing** – should be offered to all people with TB: HIV can alter the treatment of TB and may be the cause of its reactivation

Answer 36

Screening tests may identify latent TB, however, their results depend on the person’s immune status, history of TB exposure, and whether they have had the Bacillus Calmette-Guérin (BCG) vaccination. They can include: * **Mantoux test** – tuberculin is injected intradermally: Skin induration >5 mm represents a positive result * **Interferon-gamma release assay (IGRA)** – testing white blood cells’ response to TB antigens: This is faster and less likely to give a false positive result

Answer 37

* The person should be assessed for TB e.g. CXR * If there is no evidence of active infection, then the person should be treated for latent TB to prevent progression to active disease.

Answer 38

* 3 months of rifampicin and isoniazid * or 6 months rifampicin alone * + pyridoxine Treatment reducing risk of reactivation needs to be balanced against hepatotoxicity risk (>35 yo at high risk) - monitor LFTs before and after

Answer 39

* Rifampicin for 6 months * Isoniazid for 6 months * Pyrazinamide for 2 months * Ethambutol for 2 months + pyridoxine Monitor LFTs before and after treatment- if LFTS deranged treatment can either be stopped and drugs gradually reintroduced once they have normalised

Answer 40

Rifampicin - red secretions - hepatotoxicity Isoniazid * Peripheral neuropathy – pyridoxine (vitamin B6) is co-prescribed to prevent this * hepatotoxicity Pyrazinamide * Photosensitivity * Arthralgia * hepatotoxicity Ethambutol * Optic neuritis – visual acuity is checked before and during treatment * Nephrotoxicity

Answer 41

* Characteristic appearance on CXR/CT- widespread throughout patient (CNS/ bone marrow/ pericardium) * Requires neuroimaging and lumbar puncture to exclude CNS involvement * Treatment for miliary TB shouldn’t be delayed whilst awaiting biopsies

Answer 42

* Once a patient has been diagnosed they should be referred to the TB nurses * They will perform contact tracing and will test household contacts with either CXR or QuantiFERON testing and will treat any latent TB * Usually if household contacts were going to catch TB it would be before the patient was admitted so visitors are allowed – unless they have resistant TB

Answer 43

* Patients with non-resistant pulmonary TB should be nursed in a side room. * After 2 weeks of treatment patients are generally considered non-infectious to immunocompetent individuals. * If the ward also manages immunocompromised patients, including HIV (i.e our ward!) then patients with respiratory TB need to be nursed in a side room until discharge regardless of whether they are smear positive or negative (there are criteria by which they can come out but they are very stringent) * Smear positive patients can still be discharged home but would need to quarantine themselves at home until they have completed 2 weeks of treatment. * NICE guidance is that staff do NOT need to wear masks/aprons unless MDR TB is suspected or they are performing an aerosol generating procedure such as giving a nebuliser. * Patients with smear positive TB DO need to wear a mask when leaving their room until they have completed 2 weeks of treatment.

Answer 44

Retrovirus ssRNA **MOA:** By infecting and destroying CD4+ T-cells, HIV causes immunodeficiency. **Transmission** is via blood, blood products, sexual fluids, and breastmilk and may occur via: * Sexual transmission (e.g. unprotected sexual transmission) * Pregnancy (e.g. during delivery, breastfeeding) * Blood transfusion – blood is screened for HIV to reduce the risk * Intravenous drug use and sharing needles * Occupational exposure – such as needlestick injuries

Answer 45

*** Stage 1:** Acute HIV infection (2-4 weeks after infection) – flu like illness- seroconversion *** Stage 2:** Clinical latency/ chronic HIV infection- usually symptomless (some people without HIV treatment can 10-15 years without symptoms *** Stage 3:** AIDS

Answer 46

* Advanced HIV disease (or AIDS) occurs when CD4+ cell counts are very low (<200 cells/mm3) and opportunistic infections or malignancies develop. These conditions are known as AIDS-defining illnesses.

Answer 47

* Unprotected anal or vaginal sex * Multiple sexual partners * High-risk sexual practices (e.g. chemsex) * Other sexually transmitted infections (STIs) including syphilis, Chlamydia, gonorrhoea, and herpes * Sex work * Sharing contaminated needles and intravenous drug use * Injections, transfusions, procedures involving unsterile cutting/piercing without HIV screening * Accidental needlestick injuries and occupational exposure * Living in an area with high HIV prevalence

Answer 48

* Patients with HIV may present with infections not commonly seen in the general population. * Flu like symptoms (fever, chills, rash, night sweats, muscle aches, sore throat, fatigue, swollen lymph nodes, mouth ulcers) AIDs * Rapid weight loss * Recurring fever * Extreme and unexplained tiredness * Swelling of lymph glands in armpits, groin or neck * Diarrhea that lasts for more than a week * Sore of the mouth, anus, or genitals * Pneumonia * Memory loss, depression…

Answer 49

Pneumocystis pneumonia (PCP) TB

Answer 50

Tuberculosis Tuberculosis is a common presenting condition in HIV and can be pulmonary or extrapulmonary. People may present with constitutional symptoms and cough.

Answer 51

Previously known as Pneumocystis carinii, Pneumocystis jirovecii is a fungus that can cause pneumocystis pneumonia (PCP), an opportunistic infection in people with HIV. PCP is the most common AIDS-defining illness and is often seen when the CD4+ count is <200 cells/mm3. PCP can be life-threatening and difficult to diagnose as it is insidious and develops over weeks.

Answer 52

Cerebral toxoplasmosis Cytomegalovirus Encephalitis Cryptococcus AIDs dementia complex

Answer 53

HIV-associated nephropathy- nephrotic syndrome

Answer 54

Kaposi’s sarcoma Lymphoma Cervical cancer

Answer 55

As well as Kaposi’s sarcoma, HIV is associated with skin conditions that are unusually severe, recurrent, or resistant to treatment including: * Fungal infections of the skin and nails (e.g. pityriasis versicolor) * Bacterial infections – such as impetigo or folliculitis * Herpes simplex – particularly if ulcers are unusually large/persistent * Shingles – especially if more than 1 dermatome is affected * Seborrhoeic dermatitis and psoriasis * Molluscum contagiosum * Warts

Answer 56

Oropharyngeal candidiasis Oral hairy leukoplakia Gingivitis Apthous ulcers

Answer 57

Oral hairy leukoplakia is associated with the Epstein-Barr virus and is nearly exclusively seen in people with HIV. This presents with a white patch that is corrugated/hairy on the tongue and occurs due to epithelial hyperplasia of the oral mucosa.

Answer 58

Different opportunistic infections and AIDS-defining illnesses can occur according to the CD4 count. In general: * CD4+ 200-500 cells/mm3: oral candidiasis, shingles, Kaposi’s sarcoma, oral hairy leukoplakia * CD4+ 100-200 cells/mm3: Cerebral toxoplasmosis, PML, PCP, AIDS dementia complex, Cryptosporidium infection * CD4+ 50-100 cells/mm3: oesophageal candidiasis, cryptococcal meningitis, primary cerebral lymphoma, aspergillosis * CD4+ <50 cells/mm3: CMV infection, Mycobacterium avium cellulare infection

Answer 59

Combined: **P24 and HIV antibody testing** are used for the diagnosis and screening of HIV * In asymptomatic people, testing should be done at 4 weeks post-exposure: * If negative, offer a repeat confirmatory test at 12 weeks

Answer 60

**HIV antibodies** HIV antibodies may not be present in early infection, however, they are present in most people at 4-6 weeks and over 90% at 3 months. They are screened for using an ELISA (Enzyme Linked Immuno-Sorbent Assay) test and a repeat test to confirm is done using an HIV-1/HIV-2 differentiation assay. **p24 antigen** The p24 antigen is a viral protein that can be found earlier as viral RNA rises in the blood. It is usually positive at 1-4 weeks after infection.

Answer 61

Post-exposure prophylaxis Pre-exposure prophylaxis

Answer 62

* If PEP is indicated, then combination antiretroviral therapy is started as soon as possible (ideally within 1-2 hours, but up to 72 hours) for 4 weeks. Combined testing is done at 12 weeks post-PEP.

Answer 63

Pre-exposure prophylaxis (PrEP) may be prescribed in specialist sexual health services to people who are at high risk of HIV transmission including: HIV-negative men who have condomless sex with other men. HIV-negative heterosexual men and women having condomless sex with partners who are HIV positive HIV-negative trans women who are identified as being at elevated risk of HIV acquisition through condomless sex

Answer 64

The management of HIV involves the use of a combination of antiretroviral drugs. They are now started as soon as someone is diagnosed with HIV rather than waiting for a CD4+ count of <200 cells/mm3.

Answer 65

should be prescribed Co-trimoxazole 480mg PO OD as primary prophylaxis against PCP.

Answer 66

CD4 <50 Azithromycin 1250mg PO once weekly to protect against MAI Should be assessed by ophthalmology with dilated fundoscopy to look for evidence of intra-ocular infections such as CMV retinitis

Answer 67

Yellow fever is a type of zoonotic viral haemorrhagic fever caused by the yellow fever virus, which is transmitted by Aedes mosquitos. If severe enough, it can cause fever, haemolytic jaundice, and acute kidney injury. Other examples of viral haemorrhagic fever include dengue fever and Ebola.

Answer 68

* Initial 3-4 days of acute fever, headache, malaise, and myalgia followed by a brief remission * After a few days, a second episode of high fever occurs, along with nausea, vomiting, abdominal pain, and drowsiness * Hepatitis, jaundice, and haemorrhage follow (e.g. haematemesis, melaena, petechiae, purpura, epistaxis) * Oliguria and uraemia can develop as acute kidney injury occurs * Bradycardia may be seen

Answer 69

Schistosomiasis describes an infection with parasitic worms, more specifically flukes (trematodes), of the Schistosoma genus. Three clinically-relevant species are: * Schistosoma haematobium – infects the bladder, endemic in Africa and the Middle East * Schistosoma mansoni – infects the colon and portal system, endemic in Egypt, Africa, the West Indies, and South America * Schistosoma japonicum – infects the colon and portal system, endemic in Japan, China, and the Philippines This section will focus on Schistosoma haematobium as it is a risk factor for bladder cancer.

Answer 70

* ‘Swimmers itch’ – an allergic contact dermatitis reaction that occurs in infected skin * Characterised by urticaria, pruritus, and papules * General features – including fever, diarrhoea, myalgia, arthralgia * Urinary symptoms – dysuria and haematuria

Answer 71

* Full blood count (FBC) and differential: may show eosinophilia * Abdominal X-ray: may show calcified areas representing eggs, not the bladder itself * Serum Schistosoma antibodies: often performed in asymptomatic patients * Urine or stool microscopy: often performed in symptomatic patients, shows eggs

Answer 72

single dose of praziquantel

Infectious diseases (Disease summaries) Flashcards

(96 cards)