Infectious disease Flashcards

Question

whar are gram positive cocci?

Answer 1

stahylococcus streptococcus enterococcus

Answer 2

Use the mnemonic “corney Mike’s list of basic cars”: ``` Corney – Corneybacteria Mike’s – Mycobacteria List of – Listeria Basic – Bacillus Cars – Nocardia ```

Answer 3

Use the mnemonic “CLAP”: C – Clostridium L – Lactobacillus A – Actinomyces P – Propionibacterium

Answer 4

``` Neisseria meningitis Neisseria gonorrhoea Haemophilia influenza E. coli Klebsiella Pseudomonas aeruginosa Moraxella catarrhalis ```

Answer 5

The definition of atypical bacteria is that they cannot be cultured in the normal way or detected using a gram stain. Atypical bacteria are most often implicated in pneumonia. The atypical bacteria that cause atypical pneumonia can be remembered using the mnemonic “legions of psittaci MCQs”: ``` Legions – Legionella pneumophila Psittaci – Chlamydia psittaci M – Mycoplasma pneumoniae C – Chlamydydophila pneumoniae Qs – Q fever (coxiella burneti) ```

Answer 6

MRSA refers to staphylococcus aureus bacteria that have become resistant to beta-lactam antibiotics such as penicillins, cephalosporins and carbapenems

Answer 7

ESBLs are bacteria that have developed resistance to beta-lactam antibiotics. They produce beta lactamase enzymes that destroy the beta-lactam ring on the antibiotic. They can be resistant to a very broad range of antibiotics. ESBLs tend to be e. coli or klebsiella and typically cause urinary tract infections but can also cause other infections such as pneumonia. They are usually sensitive to carbapenems such as meropenem or imipenem.

Answer 8

Antibiotics with a beta-lactam ring Penicillin Carbapenems such as meropenem Cephalosporins Antibiotics without a beta-lactam ring Vancomycin Teicoplanin

Answer 9

Bacteria produce their own folic acid in a series of steps. This chain starts with para-aminobenzoic acid (PABA), which is directly absorbed in to the cell across the cell membrane. PABA is then converted to dihydrofolic acid (DHFA), then tetrahydrofolic acid (THFA) and finally folic acid. Antibiotics can be used to disrupt steps along this chain: Sulfamethoxazole blocks the conversion of PABA to DHFA Trimethoprim blocks the conversion of DHFA to THFA Co-trimoxazole is a combination of sulfamethoxazole and trimethoprim

Answer 10

The reduction of metronidazole into its active form only occurs in anaerobic cells. When partially reduced metronidazole inhibits nucleic acid synthesis. This is why metronidazole is effective against anaerobes and not aerobes.

Answer 11

``` Macrolides such as erythromycin, clarithromycin and azithromycin Clindamycin Tetracyclines such as doxycycline Gentamicin Chloramphenicol ```

Answer 12

sepsis is a condition where the body launches a large immune response to an infection that causes systemic inflammation and affects the functioning organs of the body sepsis: life-threatening organ dysfunction caused by a dysregulated host response to infection septic shock: a more severe form sepsis, technically defined as 'in which circulatory, cellular, and metabolic abnormalities are associated with a greater risk of mortality than with sepsis alone

Answer 13

The bacteria or other pathogens are recognised by macrophages, lymphocytes and mast cells. These cells release vast amounts of cytokines like interleukins and tumor necrosis factor to alert the immune system of an invader. These cytokines activate other parts of the immune system. This immune activation leads to further release of chemicals such as nitrous oxide that causes vasodilation. This full immune response causes inflammation throughout the body. Many of these cytokines cause the endothelial lining of blood vessels to become more permeable. This causes fluid to leak out of the blood and in to the extracellular space leading to oedema and a reduction in intravascular volume. The oedema around blood vessels creates a space between the blood and the tissues reducing the amount of oxygen that reaches the tissues. Activation of the coagulation system leads to deposition of fibrin throughout the circulation further compromising organ and tissue perfusion. It also leads to consumption of platelets and clotting factors as they are being used up to form the clots within the circulatory system. This leads to thrombocytopenia, haemorrhages and an inability to form clots and stop bleeding. This is called disseminated intravascular coagulopathy (DIC). Blood lactate rises due to hypoperfusion of tissues that starves the tissues of oxygen causing them to switch to anaerobic respiration. A waste product of anaerobic respiration is lactate.

Answer 14

Any condition that impacts the immune system or makes the patient more frail or prone to infection is a risk factor for developing sepsis: - Very young or old patients (under 1 or over 75 years) - Chronic conditions such as COPD and diabetes - Chemotherapy, immunosuppressants or steroids - Surgery or recent trauma or burns - Pregnancy or peripartum - Indwelling medical devices such as catheters or central lines

Answer 15

The National Early Warning Score (NEWS) is used in the UK to pick up the signs of sepsis. This involves checking physical observations and their consciousness level: ``` Temperature Heart rate Respiratory rate Oxygen saturations Blood pressure Consciousness level ```

Answer 16

high temp heart rate increase increased resp rate oxygen sats BP Signs of potential sources such as cellulitis, discharge from a wound, cough or dysuria Non-blanching rash can indicate meningococcal septicaemia Reduced urine output Mottled skin Cyanosis Arrhythmias such as new onset atrial fibrillation

Answer 17

tachypnoea

Answer 18

Elderly patients often present with confusion or drowsiness or simply “off legs”

Answer 19

Neutropenic or immunosuppressed patients may have normal observations and temperature despite being life threatening unwell

Answer 20

Arrange blood tests for patients with suspected sepsis: Full blood count to assess cell count including white cells and neutrophils U&Es to assess kidney function and for acute kidney injury LFTs to assess liver function and for possible source of infection CRP to assess inflammation Clotting to assess for disseminated intravascular coagulopathy (DIC) Blood cultures to assess for bacteraemia Blood gas to assess lactate, pH and glucose Additional investigations can be helpful in locating the source of the infection: Urine dipstick and culture Chest xray CT scan if intra-abdominal infection or abscess is suspected Lumbar puncture for meningitis or encephalitis

Answer 21

quickSOFA - if outside of ICU if they have quickSOFA (qSOFA) score meeting >= 2 of the following criteria: respiratory rate of 22/min or greater, altered mentation, or systolic blood pressure of 100mmHg or less Within an ICU setting a full SOFA score is often used >>> To help identify and categorise patients the Sequential (Sepsis-Related) Organ Failure Assessment Score (SOFA) is increasingly used. The score grades abnormality by organ system and accounts for clinical interventions. However, laboratory variables, namely, PaO2, platelet count, creatinine level, and bilirubin level, are needed for full computation.

Answer 22

RED FLAG Responds only to voice or pain/ unresponsive Acute confusional state Systolic B.P <= 90 mmHg (or drop >40 from normal) Heart rate > 130 per minute Respiratory rate >= 25 per minute Needs oxygen to keep SpO2 >=92% Non-blanching rash, mottled/ ashen/ cyanotic Not passed urine in last 18 h/ UO < 0.5 ml/kg/hr Lactate >=2 mmol/l Recent chemotherapy AMBER Relatives concerned about mental status Acute deterioration in functional ability Immunosuppressed Trauma/ surgery/ procedure in last 6 weeks Respiratory rate 21-24 Systolic B.P 91-100 mmHg Heart rate 91-130 OR new dysrhythmia Not passed urine in last 12-18 hours Temperature < 36ºC Clinical signs of wound, device or skin infection

Answer 23

'sepsis six' should be started straight away: 1. Administer oxygen: Aim to keep saturations > 94% (88-92% if at risk of CO2 retention e.g. COPD) 2. Take blood cultures 3. Give broad spectrum antibiotics 4. Give intravenous fluid challenges: NICE recommend a bolus of 500ml crystalloid over less than 15 minutes 5. Measure serum lactate 6. Measure accurate hourly urine output

Answer 24

neutropenic sepsis isa very important medical emergency. It is sepsis in a patient with a low neutrophle count less than 1 x 10^9/L Have a low threshold for suspecting neutropenic sepsis in patients taking immunosuppressants or medications that may cause neutropenia. Treat any temperature above 38C as neutropenic sepsis in these patients until proven otherwise. They are at high risk of death from sepsis as their immune system cannot adequately fight the infection. They need emergency admission and careful management. Each local hospital will have a neutropenic sepsis policy. Treatment is with immediate broad spectrum antibiotics such as piperacillin with tazobactam (tazocin). The other aspects of management are essentially the same as for sepsis however extra precaution needs to be taken. Time is precious so don’t delay antibiotics while waiting for investigation results.

Answer 25

Anti-cancer chemotherapy Clozapine (schizophrenia) Hydroxychloroquine (rheumatoid arthritis) Methotrexate (rheumatoid arthritis) Sulfasalazine (rheumatoid arthritis) Carbimazole (hyperthyroidism) Quinine (malaria) Infliximab (monoclonal antibody use for immunosuppression) Rituximab (monoclonal antibody use for immunosuppression)

Answer 26

The influenza virus is an RNA virus. There are three types: A, B and C, of which A and B are the most common. The A type has different H and N subtypes and you may hear about different strains, for example H1N1 (swine flu) and H5N1 (avian flu). Outbreaks typically occur during the winter.

Answer 27

``` those at higher risk of developig flu: aged over 65 young children pregnant woman chronic health conditions such as asthma, COPD, heart failure and diabetes healthare workers and carers ```

Answer 28

``` fever coryzal symptoms lethargy and fatigue anorexia muscle and joint aches headache dry cough sore throuat ```

Answer 29

usually treatment is started based on hisotry, risk factors and clinical presentation however viral nasal or throat swabs can be sent to lab for PCR analysis

Answer 30

Health patients not at risk of complications just need fluids and rest those at risk of complications can have medications - oral oseltamivir 75mg twice a day for 5 days or - inhaled zanamivir 10 mg twice daily for 5 days however these tretaments must be started withing 48 h hours of onset of symptoms to be effective Post-exposure prophylaxis can be given to higher risk patients such as those with chronic diseases or immunosuppression within 48 hours of close contact with influenza. This aims to minimise the risk of developing flu and complications. Oral oseltamivir 75mg once daily for 10 days Inhaled zanamivir 10mg once daily for 10 days

Answer 31

``` Otitis media, sinusitis and bronchitis Viral pneumonia Secondary bacteria pneumonia Worsening of chronic health conditions such as COPD and heart failure Febrile convulsions (young children) Encephalitis ```

Answer 32

1 day before symptoms start and 7 days after

Answer 33

HIV is an RNA retrovirus. HIV-1 is most common type. HIV-2 is rare outside West Africa. The virus enters and destroys the CD4 T helper cells. An initial seroconversion flu like illness occurs within a few weeks of infection. The infection is then asymptomatic until it progresses and the patient becomes immunocompromised and develops AIDS defining illnesses and opportunistic infections potentially years later

Answer 34

unprotected anal, vaginal or oral sexual activity mother to child at any stage of pregnancy, birth or breast feeding - vertical transmission mucous membrane, blood or open wound exposure to infected blood or bodily fluids such as sharing needles, needle stick injuries or blood splashed in the eye

Answer 35

There is a long list of AIDS defining illnesses associated with end stage HIV infection where the CD4 count has dropped to a level that allows for unusual opportunistic infections and malignancies to appear. Some examples are: ``` Kaposi’s sarcoma Pneumocystis jirovecii pneumonia (PCP) Cytomegalovirus infection Candidiasis (oesophageal or bronchial) Lymphomas Tuberculosis ```

Answer 36

Antibody blood test. This is the typical test used in hospitals to screen for HIV. There is an option for patients to self sample by requesting a kit online and posting a sample of their blood to get tested for the antibody. PCR testing for the p24 antigen tests directly for this HIV antigen in the blood and can be positive before the antibody test. PCR testing for the HIV RNA levels tests directly for the quantity of the HIV virus in the blood and gives a viral load.

Answer 37

CD4 count This is a count of the number of CD4 cells in the blood. These are the cells destroyed by the HIV virus. The lower the count the higher the risk of opportunistic infection. 500-1200 cells/mm3 is the normal range Under 200 cells/mm3 is considered end stage HIV / AIDS and puts the patient at high risk of opportunistic infections ``` Viral Load (VL) Viral load is the number of copies of HIV RNA per ml of blood. “Undetectable” refers to a viral load below the labs recordable range (usually 50 – 100 copies/ml). The viral load can be in the hundreds of thousands in untreated HIV. ```

Answer 38

a combination of antiretroviral therapy (ART) medications. Some regimes involve only a single combination tablet once per day that has the potential to completely suppress the infection. Specialist blood tests can establish the resistance of each HIV strain to different medications to help tailor treatment. BHIVA guidelines (2015) recommend a starting regime of 2 NRTIs (e.g. tenofovir and emtricitabine) plus a third agent. The aim of treatment is to achieve a normal CD4 count and undetectable viral load. As a general rule when a patient has normal CD4 and undetectable VL on ART treat their physical health problems (e.g. routine chest infections) as you would an HIV -ve patient. When prescribing be aware and check interactions any medication might have with the HIV therapy. Highly Active Anti-Retrovirus Therapy (HAART) Medication Classes Protease Inhibitors (PIs) Integrase Inhibitors (IIs) Nucleoside Reverse Transcriptase Inhibitors (NRTIs) Non-Nucleoside Reverse Transcriptase Inhibitors (NNRTIs) Entry Inhibitors (EIs) Prophylactic co-trimoxazole (Septrin) is given to patients with CD4 < 200/mm3 to protect against pneumocystis jirovecii pneumonia (PCP). HIV infection increases the risk of developing cardiovascular disease. Patients with HIV have close monitoring of cardiovascular risk factors and blood lipids and appropriate treatment (such as statins) to reduce their risk of developing cardiovascular disease. Yearly cervical smears are required for women. HIV predisposes to developing cervical human papillomavirus (HPV) infection and cervical cancer so female patients need close monitoring to ensure early detection of these complications. Vaccinations should be up to date including annual influenza, pneumococcal (every 5-10 years), hepatitis A and B, tetanus, diphtheria and polio. Patients should avoid live vaccines.

Answer 39

Entry inhibitors maraviroc (binds to CCR5, preventing an interaction with gp41), enfuvirtide (binds to gp41, also known as a 'fusion inhibitor') prevent HIV-1 from entering and infecting immune cells

Answer 40

examples: zidovudine (AZT), abacavir, emtricitabine, didanosine, lamivudine, stavudine, zalcitabine, tenofovir general NRTI side-effects: peripheral neuropathy tenofovir: used in BHIVAs two recommended regime NRTI. Adverse effects include renal impairment and ostesoporosis zidovudine: anaemia, myopathy, black nails didanosine: pancreatitis

Answer 41

Non-nucleoside reverse transcriptase inhibitors (NNRTI) examples: nevirapine, efavirenz side-effects: P450 enzyme interaction (nevirapine induces), rashes

Answer 42

Protease inhibitors (PI) examples: indinavir, nelfinavir, ritonavir, saquinavir side-effects: diabetes, hyperlipidaemia, buffalo hump, central obesity, P450 enzyme inhibition indinavir: renal stones, asymptomatic hyperbilirubinaemia ritonavir: a potent inhibitor of the P450 system

Answer 43

Integrase inhibitors | examples: raltegravir, elvitegravir, dolutegravir

Answer 44

toxoplasmosis Primary CNS lymhoma tuberculosis

Answer 45

accounts for around 50% of cerebral lesions in patients with HIV constitutional symptoms, headache, confusion, drowsiness CT: usually single or multiple ring enhancing lesions, mass effect may be seen management: sulfadiazine and pyrimethamine

Answer 46

Primary CNS lymphoma accounts for around 30% of cerebral lesions associated with the Epstein-Barr virus CT: single or multiple homogenous enhancing lesions treatment generally involves steroids (may significantly reduce tumour size), chemotherapy (e.g. methotrexate) + with or without whole brain irradiation. Surgical may be considered for lower grade tumours

Answer 47

Differentiating between toxoplasmosis and lymphoma is a common clinical scenario in HIV patients. It is clearly important given the vastly different treatment strategies. TOXOPLASMOSIS Multiple lesions Ring or nodular enhancement Thallium SPECT negative LYMPHOMA Single lesion Solid (homogenous) enhancement Thallium SPECT positive

Answer 48

Encephalitis may be due to CMV or HIV itself HSV encephalitis but is relatively rare in the context of HIV CT: oedematous brain Cryptococcus most common fungal infection of CNS headache, fever, malaise, nausea/vomiting, seizures, focal neurological deficit CSF: high opening pressure, India ink test positive CT: meningeal enhancement, cerebral oedema meningitis is typical presentation but may occasionally cause a space occupying lesion Progressive multifocal leukoencephalopathy (PML) widespread demyelination due to infection of oligodendrocytes by JC virus (a polyoma DNA virus) symptoms, subacute onset : behavioural changes, speech, motor, visual impairment CT: single or multiple lesions, no mass effect, don't usually enhance. MRI is better - high-signal demyelinating white matter lesions are seen AIDS dementia complex caused by HIV virus itself symptoms: behavioural changes, motor impairment CT: cortical and subcortical atrophy

Answer 49

Oral thrush Secondary to Candida albicans Shingles Secondary to herpes zoster Hairy leukoplakia Secondary to EBV Kaposi sarcoma Secondary to HHV-8

Answer 50

Cryptosporidiosis - Whilst patients with a CD4 count of 200-500 may develop cryptosporidiosis the disease is usually self-limiting and similar to that in immunocompetent hosts Cerebral toxoplasmosis Progressive multifocal leukoencephalopathy- Secondary to the JC virus Pneumocystis jirovecii pneumonia HIV dementia

Answer 51

Aspergillosis Secondary to Aspergillus fumigatus Oesophageal candidiasis Secondary to Candida albicans Cryptococcal meningitis Primary CNS lymphoma Secondary to EBV

Answer 52

Cytomegalovirus retinitis Affects around 30-40% of patients with CD4 < 50 cells/mm³ Mycobacterium avium-intracellulare infection

Answer 53

caused by HHV-8 (human herpes virus 8) presents as purple papules or plaques on the skin or mucosa (e.g. gastrointestinal and respiratory tract) skin lesions may later ulcerate respiratory involvement may cause massive haemoptysis and pleural effusion radiotherapy + resection

Answer 54

Whilst the organism Pneumocystis carinii is now referred to as Pneumocystis jiroveci, the term Pneumocystis carinii pneumonia (PCP) is still in common use Pneumocystis jiroveci is an unicellular eukaryote, generally classified as a fungus but some authorities consider it a protozoa PCP is the most common opportunistic infection in AIDS all patients with a CD4 count < 200/mm³ should receive PCP prophylaxis ``` Features dyspnoea dry cough fever very few chest signs ``` Pneumothorax is a common complication of PCP. Extrapulmonary manifestations are rare (1-2% of cases), may cause hepatosplenomegaly lymphadenopathy choroid lesions Investigation CXR: typically shows bilateral interstitial pulmonary infiltrates but can present with other x-ray findings e.g. lobar consolidation. May be normal exercise-induced desaturation sputum often fails to show PCP, bronchoalveolar lavage (BAL) often needed to demonstrate PCP (silver stain shows characteristic cysts) Management co-trimoxazole IV pentamidine in severe cases aerosolized pentamidine is an alternative treatment for Pneumocystis jiroveci pneumonia but is less effective with a risk of pneumothorax steroids if hypoxic (if pO2 < 9.3kPa then steroids reduce risk of respiratory failure by 50% and death by a third)

Answer 55

Post exposure prophylaxis can be used after exposure to HIV to reduce the risk of transmission. It is not 100% effective and must be commenced within a short period (less than 72 hours). The sooner it is started the better. A risk assessment about the probability of developing HIV should be balanced against the side effects of post exposure prophylaxis. It involves a combination of ART therapy. The current regime is Truvada (emtricitabine / tenofovir) and raltegravir for 28 days. HIV tests should be done initially but also a minimum of 3 months after exposure to confirm a negative status. Individuals should abstain from unprotected activity for a minimum of 3 months until confirmed negative.

Answer 56

herpes simplex virus there are two main strains HSV1 and HSV2. It was previously thought that HSV1 was oral and HSV2 was genital but not thought that they overlap. less commonly primary or recurrent HSV infections may also present at other sites with neurological, ocular, hepatic or respiratory complications

Answer 57

- dysuria in woman - lymphadenopathy - genital ulcer - oral ulcer - they may have tingling sensation - primary infection may present with severe gingivostmatitis

Answer 58

HIV infection immunosupressive medicaions high risk sexual behaviour

Answer 59

- viral culture (when lesions are present) - HSV PCR - glycoprotein G-based type specific serology (gG! and gG2)

Answer 60

``` symphilis chancroid contact dermatitis rheumatological fisease crohns/UC scabies fixed drug erruption squamous cell carcinome shingles ```

Answer 61

if they have gingivostomatitis - oral aciclovir, chlorhexidine mouthwash genital herpes - oral aciclovir, valaciclovir or famiciclovir plus symptomatic treatment (paracetamol, ibuprofen or lidocaine topical) for oral herpes - oral aciclovir, valaciclovir or famciclovir plus symptomatic treatment if pregnant give antiviral prophylaxsis at 36 weeks

Answer 62

fever, headache, psychiatric symptoms, seizures, vomiting focal features - aphasia peripheral lesions (cold sores) have no relation to the resence of HSV encephalitis *typically affects the temporal and inferior frontal lobes

Answer 63

CSF - lymphocytosis, elevated protein PCR for HSV CT - medial temporal and inferior frontal changes (e.g. haemorrhages) MRI EEG - lateralised periodic discharges at 2 Hz

Answer 64

IV aciclovir

Answer 65

syphilis is an STI caused by spirochaete treponema pallidum characterised by primary, secondary and tertiary stages

Answer 66

chancre - painless ulcer at the site of sexual contact local non-tender lymphadenopathy (often not seen in woman as the lesion may be on the cervix )

Answer 67

they occur 6-10 weeks after primary infection - systemic symptoms - fevers, lymphadenopathy - rash on trunk, palms and soles - buccal snail track ulcers - condylomata lata (painless warty lesions of the genitalia)

Answer 68

``` Tertiary features gummas (granulomatous lesions of the skin and bones) ascending aortic aneurysms general paralysis of the insane tabes dorsalis Argyll-Robertson pupil ```

Answer 69

Features of congenital syphilis blunted upper incisor teeth (Hutchinson's teeth), 'mulberry' molars rhagades (linear scars at the angle of the mouth) keratitis saber shins saddle nose deafness

Answer 70

- serum venereal disease research laboratory (VDRL) test - is positive but will become negative after treatment (it is a cardiolipin test) - serum treponema pallidum haemagglutination (TPHA) test - this will be postive but will remain positive after treatment other options - dark field microscopy of swab from lesion - will show coiled spirochaete bacterium with a corkscrew apprearance and motility - serum treponemal enzyme immunoassay will be positive - serum TPPA will be positive

Answer 71

``` pregnancy SLE anti-phospholidpid syndrome TB leprosy malaria HIV ```

Answer 72

IM benzylpenicillin - 1.8g IM single dose if allergic to penicillin alternative is doxycyclne the Jarisch-Herxheimer reaction is sometimes seen following treatment fever, rash, tachycardia after the first dose of antibiotic in contrast to anaphylaxis, there is no wheeze or hypotension it is thought to be due to the release of endotoxins following bacterial death and typically occurs within a few hours of treatment No treatment is needed other than antipyretics if required