Infectious disease 3 Flashcards
1
Q
management of toxoplasmosis in immunocompetent patient?
A
Immunocompetent patients with toxoplasmosis don’t usually require treatment
2
Q
What is toxoplasmosis?
A
Toxoplasma gondii is an obligate intracellular protozoan that infects the body via the gastrointestinal tract, lung or broken skin. It’s oocysts release trophozoites which migrate widely around the body including to the eye, brain and muscle. The usual animal reservoir is the cat, although other animals such as rats carry the disease.
3
Q
What is Chancroid?
A
Chancroid is a tropical disease caused by Haemophilus ducreyi. It causes painful genital ulcers associated with unilateral, painful inguinal lymph node enlargement. The ulcers typically have a sharply defined, ragged, undermined border.
4
Q
What is the mechanism of action of amantadine as an antiviral?
A
Inhibits uncoating (M2 protein) of virus in cell. Also releases dopamine from nerve endings
5
Q
Management of Gonorrhoea?
A
The new first-line treatment is a single dose of IM ceftriaxone 1g
if ceftriaxone is refused (e.g. needle-phobic) then oral cefixime 400mg (single dose) + oral azithromycin 2g (single dose) should be used
6
Q
What does bone marrow aspirate show in viceral leishmaniasis?
A
A bone marrow aspirate reveals macrophages containing amastigotes.
Amastigotes are the intracellular form of the Leishmania parasite, found within macrophages. Their identification in bone marrow aspirates is a hallmark diagnostic finding for visceral leishmaniasis.
7
Q
Causes of Diarrhoe in patients with HIV?
A
Cryptosporidium + other protozoa (most common)
Cytomegalovirus
Mycobacterium avium intracellulare
Giardia
8
Q
What is the most common cause of diarrhoea in patients with HIV?
What is the treatment?
A
Cryptosporidium is the most common infective cause of diarrhoea in HIV patients. It is an intracellular protozoa and has an incubation period of 7 days. Presentation is very variable, ranging from mild to severe diarrhoea. A modified Ziehl-Neelsen stain (acid-fast stain) of the stool may reveal the characteristic red cysts of Cryptosporidium. Treatment is difficult, with the mainstay of management being supportive therapy
nitazoxanide is licensed in the US for immunocompromised patients
9
Q
When is Mycobacterium avium intracellulare seen? What are the featues? How is it managed?
A
Mycobacterium avium intracellulare is an atypical mycobacteria seen with the CD4 count is below 50.
Typical features include fever, sweats, abdominal pain and diarrhoea. There may be hepatomegaly and deranged LFTs.
Diagnosis is made by blood cultures and bone marrow examination.
Management is with rifabutin, ethambutol and clarithromycin
10
Q
Management of Syphillis?
A
IM ben pen
(alternative is doxycyline)
11
Q
What should be monitored after syhillis managed?
A
nontreponemal (rapid plasma reagin [RPR] or Venereal Disease Research Laboratory [VDRL]) titres should be monitored after treatment to assess the response
a fourfold decline in titres (e.g. 1:16 → 1:4 or 1:32 → 1:8)is often considered an adequate response to treatment
12
Q
What is Jarisch-Herxheimer reaction?
A
he Jarisch-Herxheimer reaction is sometimes seen following treatment of Syphillis
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
13
Q
HIV management?
A
Antiretroviral therapy (ART) involves a combination of at least three drugs, typically two nucleoside reverse transcriptase inhibitors (NRTI) and either a protease inhibitor (PI) or a non-nucleoside reverse transcriptase inhibitor (NNRTI). This combination both decreases viral replication but also reduces the risk of viral resistance emerging
14
Q
What are examples of Entry inhibitors?
A
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
15
Q
What are examples of nucleoside analogue reverse transcriptase inhibitors?
A
Nucleoside analogue reverse transcriptase inhibitors (NRTI)
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
16
Q
What are examples of non-nucleoside reverse transcriptase inhibitors?
A
Non-nucleoside reverse transcriptase inhibitors (NNRTI)
examples: nevirapine, efavirenz
side-effects: P450 enzyme interaction (nevirapine induces), rashes
17
Q
What are examples of protease inhibitors?
A
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
18
Q
What are examples of integrase inhibitors?
A
Integrase inhibitors
block the action of integrase, a viral enzyme that inserts the viral genome into the DNA of the host cell
examples: raltegravir, elvitegravir, dolutegravir
19
Q
What should be done if Anti-HBs levels are low following Hep B vaccination?
A
It is preferable to achieve anti-HBs levels above 100mIU/ml, although levels of 10mIU/ml or more are generally accepted as enough to protect against infection.
Responders with anti-HBs levels greater than or equal to 100mIU/ml do not require any further primary doses. In immunocompetent individuals, once a response has been established further assessment of antibody levels is not indicated. Responders with antiHBs levels of 10 to 100mIU/ml should receive one additional dose of vaccine at that time.
An antibody level below 10mIU/ml is classified as a non-response to vaccine, and testing for markers of current or past infection is good clinical practice. In non-responders, a repeat course of vaccine is recommended, followed by retesting one to two months after the second course. Those who still have anti-HBs levels below 10mIU/ml, and who have no markers of current or past infection, will require HBIG for protection if exposed
to the virus.
20
Q
what kind of virus is hep B?
A
Hepatitis B is a double-stranded DNA hepadnavirus and is spread through exposure to infected blood or body fluids, including vertical transmission from mother to child. The incubation period is 6-20 weeks.
21
Q
Features of hep B ?
A
The features of hepatitis B include fever, jaundice and elevated liver transaminases.
22
Q
Complications of Hep B infection?
A
chronic hepatitis (5-10%). ‘Ground-glass’ hepatocytes may be seen on light microscopy
fulminant liver failure (1%)
hepatocellular carcinoma
glomerulonephritis
polyarteritis nodosa
cryoglobulinaemia
23
Q
Which groups of people should be vaccinated against hep B?
A
children born in the UK are now vaccinated as part of the routine immunisation schedule. This is given at 2, 3 and 4 months of age
at risk groups who should be vaccinated include: healthcare workers, intravenous drug users, sex workers, close family contacts of an individual with hepatitis B, individuals receiving blood transfusions regularly, chronic kidney disease patients who may soon require renal replacement therapy, prisoners, chronic liver disease patients
24
Q
Management of hep B?
A
pegylated interferon-alpha used to be the only treatment available. It reduces viral replication in up to 30% of chronic carriers. A better response is predicted by being female, < 50 years old, low HBV DNA levels, non-Asian, HIV negative, high degree of inflammation on liver biopsy
whilst NICE still advocate the use of pegylated interferon firstl-line other antiviral medications are increasingly used with an aim to suppress viral replication (not in a dissimilar way to treating HIV patients)
examples include tenofovir, entecavir and telbivudine (a synthetic thymidine nucleoside analogue)
25
What cause of pneumonia is associated with caviatin lesions?
Staph aureus
26
Legionella is associated with what when it causes pneumonia?
Deranged LFTs
. Other features include hyponatraemia, headache and dry cough
27
what cause of pneumonia is associated with cold sores?
Streptococcus pneumoniae
28
Stereotypical histories of gastroenteritis?
29
Vaccinations and abx prophylacis post splenectomy?
Vaccination
if elective, should be done 2 weeks prior to operation
Hib, meningitis A & C
annual influenza vaccination
pneumococcal vaccine every 5 years
Antibiotic prophylaxis
penicillin V: unfortunately clear guidelines do not exist of how long antibiotic prophylaxis should be continued. It is generally accepted though that penicillin should be continued for at least 2 years and at least until the patient is 16 years of age, although the majority of patients are usually put on antibiotic prophylaxis for life
29
What are patients at risk of following a splenectomy?
Following a splenectomy patients are particularly at risk from pneumococcus, Haemophilus, meningococcus and Capnocytophaga canimorsus* infections
30
Indications for splenectomy ?
Trauma: 1/4 are iatrogenic
Spontaneous rupture: EBV
Hypersplenism: hereditary spherocytosis or elliptocytosis etc
Malignancy: lymphoma or leukaemia
Splenic cysts, hydatid cysts, splenic abscesses
31
Complications post splenectomy?
Haemorrhage (may be early and either from short gastrics or splenic hilar vessels
Pancreatic fistula (from iatrogenic damage to pancreatic tail)
Thrombocytosis: prophylactic aspirin
Encapsulated bacteria infection e.g. Strep. pneumoniae, Haemophilus influenzae and Neisseria meningitidis
32
What are post splenectomy changes?
Platelets will rise first (therefore in ITP should be given after splenic artery clamped)
Blood film will change over following weeks, Howell-Jolly bodies will appear
Other blood film changes include target cells and Pappenheimer bodies
Increased risk of post-splenectomy sepsis, therefore prophylactic antibiotics and pneumococcal vaccine should be given.
33
Investigations for chlamydia?
traditional cell culture is no longer widely used
nuclear acid amplification tests (NAATs) are now the investigation of choice
urine (first void urine sample), vulvovaginal swab or cervical swab may be tested using the NAAT technique
for women: the vulvovaginal swab is first-line
for men: the urine test is first-line
Chlamydiatesting should be carried out two weeks after a possible exposure
34
Management of Chlamydia?
7 days of Doxycycline
if doxycycline is contraindicated / not tolerated then either azithromycin (1g od for one day, then 500mg od for two days) should be used
if pregnant then azithromycin, erythromycin or amoxicillin may be used.
35
How do you treat cysticercosis?
bendazoles
36
What is infectious mononucleosis?
nfectious mononucleosis (glandular fever) is caused by the Epstein-Barr virus (EBV, also known as human herpesvirus 4, HHV-4) in 90% of cases. Less frequent causes include cytomegalovirus and HHV-6. It is most common in adolescents and young adults.
37
Features of infectious mono?
The classic triad of sore throat, pyrexia and lymphadenopathy is seen in around 98% of patients:
sore throat
lymphadenopathy: may be present in the anterior and posterior triangles of the neck, in contrast to tonsillitis which typically only results in the upper anterior cervical chain being enlarged
pyrexia
Other features include:
malaise, anorexia, headache
palatal petechiae
splenomegaly - occurs in around 50% of patients and may rarely predispose to splenic rupture
hepatitis, transient rise in ALT
lymphocytosis: presence of 50% lymphocytes with at least 10% atypical lymphocytes
haemolytic anaemia secondary to cold agglutins (IgM)
a maculopapular, pruritic rash develops in around 99% of patients who take ampicillin/amoxicillin whilst they have infectious mononucleosis
38
Diagnosis of gladular fever?
heterophil antibody test (Monospot test)
NICE guidelines suggest FBC and Monospot in the 2nd week of the illness to confirm a diagnosis of glandular fever.
39
classification of bacteria?
Remember:
Gram-positive cocci = staphylococci + streptococci (including enterococci)
Gram-negative cocci = Neisseria meningitidis + Neisseria gonorrhoeae, also Moraxella catarrhalis
Therefore, only a small list of Gram-positive rods (bacilli) need to be memorised to categorise all bacteria - mnemonic = ABCD L
Actinomyces
Bacillus anthracis (anthrax)
Clostridium
Diphtheria: Corynebacterium diphtheriae
Listeria monocytogenes
Remaining organisms are Gram-negative rods, e.g.:
Escherichia coli
Haemophilus influenzae
Pseudomonas aeruginosa
Salmonella sp.
Shigella sp.
Campylobacter jejuni
40
Treatment of UTI in non pregnant woman?
local antibiotic guidelines should be followed if available
NICE recommend trimethoprim or nitrofurantoin for 3 days
send a urine culture if:
aged > 65 years
visible or non-visible haematuria
40
What is a common cause of UTI in sexually active young woman?
Staphylococcus saprophyticus is the second most common cause of UTIs in sexually active young women (E. coli is most common). It is a gram-positive coccus that grows in clusters and is coagulase-negative.
41
treatment of UTI in pregnant woman?
if the pregnant woman is symptomatic:
a urine culture should be sent in all cases
should be treated with an antibiotic for 7 days
**first-line: nitrofurantoin (should be avoided near term)**
second-line: amoxicillin or cefalexin
trimethoprim is teratogenic in the first trimester and should be avoided during pregnancy
asymptomatic bacteriuria in pregnant women:
a urine culture should be performed routinely at the first antenatal visit
NICE recommend an immediate antibiotic prescription of either nitrofurantoin (should be avoided near term), amoxicillin or cefalexin. This should be a 7-day course
the rationale of treating asymptomatic bacteriuria is the significant risk of progression to acute pyelonephritis
a further urine culture should be sent following completion of treatment as a test of cure
women who suffer regular urinary tract infections following sexual intercourse can be offered post-coital antibiotic prophylaxis - single dose trimethoprim or nitrofurantoin are used first-line
42
Treatment of UTI in men ?
an immediate antibiotic prescription should be offered for 7 days
as with non-pregnant women, trimethoprim or nitrofurantoin should be offered first-line unless prostatitis is suspected
a urine culture should be sent in all cases before antibiotics are started
NICE state: 'Referral to urology is not routinely required for men who have had one uncomplicated lower urinary tract infection (UTI).'
43
Treatment of UTI in catheterised patients?
Catherised patients
do not treat asymptomatic bacteria in catheterised patients
if the patient is symptomatic they should be treated with an antibiotic
a 7-day, rather than a 3-day course should be given
consider removing or changing the catheter as soon as possible if it has been in place for longer than 7 days
44
Management of pyelonephritis?
For patients with sign of acute pyelonephritis hospital admission should be considered
local antibiotic guidelines should be followed if available
the BNF currently recommends a broad-spectrum cephalosporin or a quinolone (for non-pregnant women) for 10-14 days
45
What type of parasite is toxoplasmosis?
an obligate intracellular protozoan parasite
46
What type of penumoni would cause a blood smear to show red blood cell aggltination?
Mycoplasma pneumoniae
IgM antibodies against Mycoplasma pneumoniae react against human red blood cells at cold temperatures causing them to agglutinate. This can be seen in a peripheral blood smear and is the reason Mycoplasma pneumoniae causes haemolytic anaemia.
47
what types of HPV predispose to genital warts?
6&11
48
Management of genital warts?
Management
topical podophyllum or cryotherapy are commonly used as first-line treatments depending on the location and type of lesion
multiple, non-keratinised warts are generally best treated with topical agents
solitary, keratinised warts respond better to cryotherapy
imiquimod is a topical cream that is generally used second line
genital warts are often resistant to treatment and recurrence is common although the majority of anogenital infections with HPV clear without intervention within 1-2 years
## Footnote
Genital wart treatment
multiple, non-keratinised warts: topical podophyllum
solitary, keratinised warts: cryotherapy
49
Long incubation bloody diarrhoea in traveller?
Long illness watery diarrhoea in traveller?
Acute bloody diarrhoea in UK?
1) LONG incubation bloody diarrhoea in traveller - amoebiasis - METROnidazole
2) LONG illness watery diarrhoea in traveller - giardiasis - METROnidazole
3) aCute bloody diarrhoea in uK - Campylobacter - Clarithromycin / Cipro
V Short bloody diarrhoea - E. Coli
50
What cause of diarrhoea is assoicated with a prodrome?
Campylobacter
Several factors point to Campylobacter - including bloody diarrhoea, prodromal symptoms and abdominal pain mimicking appendicitis
51
What does trimethoprim do to creatinine levels?
Trimethoprim can cause a reversible increase in serum creatinine by inhibiting the tubular secretion of creatinine without affecting glomerular filtration rate (GFR). This does not signify true renal impairment but rather an artificial rise in serum creatinine.
52
Mechanism of action of trimethoprim?
interferes with DNA synthesis by inhibiting dihydrofolate reductase
may, therefore, interact with methotrexate, which also inhibits dihydrofolate reductase
53
Adverse effects of trimethoprim?
myelosuppression
transient rise in creatinine: trimethoprim competitively inhibits the tubular secretion of creatinine resulting in a temporary increase which reverses upon stopping the drug
trimethoprim blocks the ENaC channel in the distal nephron, causing a hyperkalaemic distal RTA (type 4). It also inhibits creatinine secretion, often leading to an increase in creatinine by around 40 points (but not necessarily causing AKI)
Use in pregnancy
the BNF advises that there is a: 'Teratogenic risk in first trimester (folate antagonist). Manufacturers advise avoid during pregnancy.'
54
What type of Abx inhibit protein synthesis?
## Footnote
Buy AT 30
Aminoglycosides
Tetracyclines
CELL for 50
Clindamycin
Erythromycin
Linezolid
55
55
what is diagnostic of strongyloides?
The rhabditiform larvae are diagnostic of strongyloidiasis, and the life-cycle of this worm involves passage through the lungs which causes the intermittent cough.
56
Features of leprosy?
Features
patches of hypopigmented skin typically affecting the buttocks, face, and extensor surfaces of limbs
sensory loss
57
What are the types of leprosy?
The degree of cell mediated immunity determines the type of leprosy a patient will develop.
Low degree of cell mediated immunity → lepromatous leprosy ('multibacillary')
extensive skin involvement
symmetrical nerve involvement
High degree of cell mediated immunity → tuberculoid leprosy ('paucibacillary')
limited skin disease
asymmetric nerve involvement → hypesthesia
hair loss
58
How is Leprosy managed?
WHO-recommended triple therapy: rifampicin, dapsone and clofazimine
59
High risk wounds for tetanus?
Wounds burns needing surgery delayed more than 6 hours
Wounds contaminated with soil
Compound fractures
Wounds containing foreign bodies
Wounds/burns in people with systemic sepsis
60
What malignancies are associated with EBV?
Malignancies associated with EBV infection
Burkitt's lymphoma*
Hodgkin's lymphoma
nasopharyngeal carcinoma
HIV-associated central nervous system lymphomas
The non-malignant condition hairy leukoplakia is also associated with EBV infection.
61
What is Trichomonas vaginalis?
Trichomonas vaginalis is a highly motile, flagellated protozoan parasite. Trichomoniasis is a sexually transmitted infection (STI).
62
Features of trichomonas vaginalis?
vaginal discharge: offensive, yellow/green, frothy
vulvovaginitis
strawberry cervix
pH > 4.5
in men is usually asymptomatic but may cause urethritis
63
Investigations for trichomonas?
microscopy of a wet mount shows motile trophozoites
64
Magament of Trichomonas?
oral metronidazole for 5-7 days, although the BNF also supports the use of a one-off dose of 2g metronidazole
65
Investiations for malaria?
The gold standard for diagnosis of malaria remains the blood film.
Thick and thin blood films
thick: more sensitive
thin: determine species
repeated malarial films may be required to definitively rule out infection
Rapid diagnostic tests
detect plasmodial histidine-rich protein 2
useful in resource-limited environments - they require no electricity or laboratory infrastructure and give results within 15 to 20 minutes
sensitivities from 77-99% and specificities from 83-98% for falciparum malaria
Other tests
thrombocythaemia is characteristic
normochromic normocytic anaemia
normal white cell count
reticulocytosis
66
Aspergilloma -
features?
Investigations?
An aspergilloma is a mycetoma (mass-like fungus ball) which often colonises an existing lung cavity (e.g. secondary to tuberculosis, lung cancer or cystic fibrosis).
Usually asymptomatic but features may include
cough
haemoptysis (may be severe)
Investigations
chest x-ray containing a rounded opacity. A crescent sign may be present
high titres Aspergillus precipitins
67
Aspergilloma vs Invasive aspergillosis?
Aspergilloma - history of tuberculosis, recent weight loss, haemoptysis, and the presence of a solid mass on chest x-ray are all suggestive of an aspergilloma. An aspergilloma is a fungal ball that forms within a pre-existing cavity in the lung, often as a result of previous pulmonary disease such as tuberculosis. The positive Aspergillus precipitin antibody test further supports this diagnosis.
Invasive aspergillosis usually occurs in immunocompromised patients and presents with more severe symptoms such as fever and dyspnea. The presence of a solid mass on chest x-ray is not typical for invasive aspergillosis; instead, it would show multiple nodular infiltrates or consolidation.
68
what are the features of Syphilis?
Primary features
chancre - painless ulcer at the site of sexual contact
local non-tender lymphadenopathy
often not seen in women (the lesion may be on the cervix)
Secondary features - occurs 6-10 weeks after primary infection
systemic symptoms: fevers, lymphadenopathy
rash on trunk, palms and soles
buccal 'snail track' ulcers (30%)
condylomata lata (painless, warty lesions on the genitalia )
Tertiary features
gummas (granulomatous lesions of the skin and bones)
ascending aortic aneurysms
general paralysis of the insane
tabes dorsalis
Argyll-Robertson pupil
69
Features of congenital syphillis?
blunted upper incisor teeth (Hutchinson's teeth), 'mulberry' molars
rhagades (linear scars at the angle of the mouth)
keratitis
saber shins
saddle nose
deafness
70
Management of Syphilis?
IM benpen
Doxycycline
nontreponemal (rapid plasma reagin [RPR] or Venereal Disease Research Laboratory [VDRL]) titres should be monitored after treatment to assess the response
a fourfold decline in titres (e.g. 1:16 → 1:4 or 1:32 → 1:8)is often considered an adequate response to treatment
71
Clinical features of malaria?
Fever, sweating, rigors
GI - N&V, abdominal pain, diarrhoea
Cough
Body aches
Headaches, dizziness
Tachycardia
Hypotension
Thrombocytopenia
AKI
72
Features of severe malaria?
schizonts on a blood film
parasitaemia > 2%
hypoglycaemia
acidosis
temperature > 39 °C
severe anaemia
complications as below
73
How do you supress MRSA from a carrier once identfied?
nose: mupirocin 2% in white soft paraffin, tds for 5 days
skin: chlorhexidine gluconate, od for 5 days. Apply all over but particularly to the axilla, groin and perineum
74
What Abx are used for MSRA infections?
vancomycin
teicoplanin
linezolid
75
What is Katayama fever?
systemic reaction that develops after acute schistosomal infection. This may occur weeks to months after initial infection. It can be very difficult to recognise but is often associated with a severely itchy and bumpy rash. Splenomegaly also points to schistosomiasis.
76
features of leprosy?
Features
patches of hypopigmented skin typically affecting the buttocks, face, and extensor surfaces of limbs
sensory loss
The degree of cell mediated immunity determines the type of leprosy a patient will develop.
Low degree of cell mediated immunity → lepromatous leprosy ('multibacillary')
extensive skin involvement
symmetrical nerve involvement
High degree of cell mediated immunity → tuberculoid leprosy ('paucibacillary')
limited skin disease
asymmetric nerve involvement → hypesthesia
hair loss
77
management of leprosy?
Management
WHO-recommended triple therapy: rifampicin, dapsone and clofazimine
## Footnote
multibacillary leprosy (>6 lesions) so should have triple therapy with rifampicin, dapsone and clofazimine for 12 months. For paucibacillary leprosy (5 or less lesions) you should give rifampicin and dapsone for 6 months.
78
what type of bacteria is Neisseria meningitidis?
Gram-negative cocci
79
What causes cat scratch disease?
Cat scratch disease is generally caused by the Gram negative rod Bartonella henselae
80
What are the features of cat scratch disease?
fever
history of a cat scratch
regional lymphadenopathy
headache, malaise
Diagnosis can be confirmed by microbiology through serology or culture, or histopathology through visualisation of bacilli in Warthin-Starry staining.
81
Vaccination reccomendations for splenecyomy?
Vaccination:
Pneumococcal, Haemophilus type b, and Meningococcal type C vaccines should be administered two weeks before or after splenectomy.
Schedule:
Men C and Hib at two weeks post-splenectomy.
MenACWY vaccine one month later.
Children under 2 may need a booster at 2 years.
Pneumococcal vaccines
Annual influenza vaccination for all patients
82
Treatment of meningococcal infection in pen allergic (analphylaxsis)
Chloramphenicol is the antibiotic of choice for treating meningococcal infection in patients with a known penicillin allergy, particularly when there is a history of anaphylaxis. It has good penetration into the cerebrospinal fluid and is effective against Neisseria meningitidis, the causative organism of meningococcal meningitis.
83
Cause of UTI when dipstick is negative for nitrites?
Gram positive organisms are unable to reduce nitrate to nitrite and therefore, test negative - e.g. staph saprophyticus
Gram negative organisms test positive on the nitrite test as they convert nitrates to nitrites for energy.
84
What are the different types of typhus?
endemic typhus
caused by Rickettsia typhi
reservoir/vector: fleas on rats
occurs throughout the world, typically in warm costal regions
relative bradycardia
epidemic typhus
caused by Rickettsia prowazekii
reservoir/vector: body louse
more common in central and eastern Africa, central and South America
scrub typhus
caused by Orientia tsutsugamushi
reservoir/vector: harvest mites on humans or rodents
more common in Asia
black eschar at site of original inoculation
relative bradycardia despite fever
spotted fever
caused by Rickettsia spotted fever group
spread by ticks
examples include Rocky Mountain spotted fever
## Footnote
Common features
fever, headache, malaise
rash
typically maculopapular
begins on the trunk and spreads to the extremities
later complications
meningoencephalitis
85
Management on typhus?
doxycycline
86
which type of malaria has the shortest cyclical fever?
Plasmodium knowlesi has the shortest replication time. Its full replication cycle lasts just 24 hours, explaining the daily temperature spikes every 24 hours
## Footnote
Plasmodium vivax/ovale: cyclical fever every 48 hours. Plasmodium malariae: cyclical fever every 72 hours
87
Features of non-falciparum malaria?
general features of malaria: fever, headache, splenomegaly
Plasmodium vivax/ovale: cyclical fever every 48 hours. Plasmodium malariae: cyclical fever every 72 hours
Plasmodium malariae: is associated with nephrotic syndrome.
88
Treatment of non-falciparum malaria?
in areas which are known to be chloroquine-sensitive then WHO recommend either an artemisinin-based combination therapy (ACT) or chloroquine
in areas which are known to be chloroquine-resistant an ACT should be used
ACTs should be avoided in pregnant women
patients with ovale or vivax malaria should be given primaquine following acute treatment with chloroquine to destroy liver hypnozoites and prevent relapse
89
Most common cause of non-falciparum malaria?
The most common cause of non-falciparum malaria is Plasmodium vivax, with Plasmodium ovale and Plasmodium malariae accounting for the other cases. Plasmodium vivax is often found in Central America and the Indian Subcontinent whilst Plasmodium ovale typically comes from Africa.
90
Examples of live attenuated vaccines?
BCG
measles, mumps, rubella (MMR)
influenza (intranasal)
oral rotavirus
oral polio
yellow fever
oral typhoid
91
at what cd4 count are live attenuated vaccines contraindicated?
BHIVA guidelines state that live attenuated vaccinations (also known as replicating vaccinations) are contraindicated in patients with CD4 count <200cells/µL due to the risk of vaccine-associated disease.
92
Post exposure prophylaxsis for Hep A?
Human Normal Immunoglobulin (HNIG) or hepatitis A vaccine may be used depending on the clinical situation
93
Post exposure prophylxsis for Hep B
Hepatitis B
HBsAg positive source
if the person exposed is a known responder to the HBV vaccine then a booster dose should be given
if they are a non-responder (anti-HBs < 10mIU/ml 1-2 months post-immunisation) they need to have hepatitis B immune globulin (HBIG) and a booster vaccine
unknown source
for known responders the HBV vaccine the Green Book advises considering a booster dose of HBV vaccine
for known non-responders HBIG + vaccine should be given whilst those in the process of being vaccinated should have an accelerated course of HBV vaccine
94
post exposure prophylaxsis for Hep C?
monthly PCR - if seroconversion then interferon +/- ribavirin
95
Post exposure prophylaxsis for HIV?
the risk of HIV transmission depends heavily on the incident (e.g. needle stick, type of sexual intercourse, human bite etc) and the current viral load of the patient
please see the BHIVA link for charts which outline the risk depending on the incident. Generally, low-risk incidents such as human bites don't require post-exposure prophylaxis
a combination of oral antiretrovirals (e.g. Tenofovir, emtricitabine, lopinavir and ritonavir) as soon as possible (i.e. Within 1-2 hours, but may be started up to 72 hours following exposure) for 4 weeks
serological testing at 12 weeks following completion of post-exposure prophylaxis
reduces risk of transmission by 80%
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Post exposure prophylaxsis for Varicella Zoster?
VZIG for IgG negative pregnant women/immunosuppressed
## Footnote
if there is any doubt about the mother previously having chickenpox maternal blood should be urgently checked for varicella antibodies
historically, exposure has been managed through the timely administration of varicella zoster immunoglobulin (VZIG). However, the guidance has changed due to a national/international VZIG shortage. This was initially a short-term deviation from practice in 2022 but has now become baked into longer-term guidance
oral aciclovir (or valaciclovir) is now the first choice of PEP for pregnant women at any stage of pregnancy
antivirals should be given at day 7 to day 14 after exposure, not immediately
why wait until days 7-14? From the PHE guidelines: 'In a study evaluating the comparative effectiveness of 7 days course of aciclovir given either immediately after exposure or starting at day 7 after exposure to healthy children, the incidence and severity of varicella infection was significantly higher in those given aciclovir immediately (10/13 (77%) who received aciclovir immediately developed clinical varicella compared with 3/14 (21%) who started aciclovir at day 7)'
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Estimates of transmission risk for single needlestick injury of hep B hep C and HIV?
98
When should steroids be given in PCP?
steroids if hypoxic (if pO2 < 9.3kPa then steroids reduce risk of respiratory failure by 50% and death by a third)
99
Which anti-retrovirals interact with the P450 system?
nevirapine (a NNRTI): induces P450
protease inhibitors: inhibits P450
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What is the mechanism of action of macrolides?
Binds to 50S subunit, inhibiting translocation (movement of tRNA from acceptor site to peptidyl site)
101
Which abx bind to the 50S subunit?
Clindamycin
Macrolides
102
What abx bind to the 30S unit?
Aminoglycosides
Tetracyclines
103
What abx promotes acquisition of MSRA?
Ciprofloxacin
104
what is Linezolid?
Linezolid is a type of oxazolidinone antibiotic which has been introduced in recent years. It inhibits bacterial protein synthesis by stopping the formation of the 50s initiation complex and is bacteriostatic in nature.
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When is Linezolid used?
Spectrum, highly active against Gram positive organisms including:
MRSA (Methicillin-resistant Staphylococcus aureus)
VRE (Vancomycin-resistant enterococcus)
GISA (Glycopeptide Intermediate Staphylococcus aureus)
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Adverse effects of linezolid?
Adverse effects
thrombocytopenia (reversible on stopping)
monoamine oxidase inhibitor: avoid tyramine containing foods
107
What type of stain should be used to demonstrate PCP?
Pneumocystis jiroveci pneumonia - silver stain shows characteristic cysts
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What is Rubeanic acid used for?
reagent used to detect copper in tissues. It forms a green complex with copper ions and can be useful in diagnosing Wilson's disease or assessing copper levels in liver biopsies.
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What is Pearl's stain used for?
it is primarily used to identify iron deposits within tissues. This stain involves the reaction between potassium ferrocyanide and ferric ions, resulting in a bright blue color where iron accumulates. Pearl's stain has applications in diagnosing conditions such as hemochromatosis
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What is congo red stain used for?
This stain is used to identify amyloid deposits in tissues by binding to beta-pleated sheet structures present in amyloid fibrils. Congo red-stained amyloid appears as red-orange birefringent material under polarized light microscopy.
111
What kind of reaction is seen in the tuberculin skin test?
Tuberculin skin tests are an example of type IV (delayed) hypersensitivity reactions. These are largely mediated by interferon-γ secreted by Th1 cells which in turn stimulates macrophage activity.
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What may cause a false negative mantoux test ?
miliary TB
sarcoidosis
HIV
lymphoma
very young age (e.g. < 6 months)
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How is active TB diagnosed?
CXR
Sputum smear
Sputum culture
NAAT
114
What abx should be used for prophylaxsis in people who have been exposed to a patient with confirmed bacterial meningitis ?
Oral ciprofloxacin or rifampicin
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What kind of virus is the rabies virus?
Rabies is a viral disease that causes an acute encephalitis. The rabies virus is classed as a RNA rhabdovirus (specifically a lyssavirus) and has a bullet-shaped capsid
## Footnote
After entry, the virus replicates in muscle tissue near the site of the bite before entering the peripheral nervous system. It then travels up to the central nervous system, where it causes encephalitis, leading to severe neurological symptoms. The virus eventually reaches the salivary glands, facilitating transmission.
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Features of rabies?
prodrome: headache, fever, agitation
hydrophobia: water-provoking muscle spasms
hypersalivation
Negri bodies: cytoplasmic inclusion bodies found in infected neurons
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How should patients be managed following a animal bite in a country with high risk of rabies?
the wound should be washed
if an individual is already immunised then 2 further doses of vaccine should be given
if not previously immunised then human rabies immunoglobulin (HRIG) should be given along with a full course of vaccination. If possible, the dose should be administered locally around the wound
If untreated the disease is nearly always fatal.
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What is the mechanism of action of tetanus?
Tetanus toxin (tetanospasmin) blocks the release of the inhibitory neurotransmitters GABA and glycine resulting in continuous motor neuron activity
119
what causes Kaposi's sarcoma?
caused by HHV-8 (human herpes virus 8)
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Features and management of Kaposis sarcoma?
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
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What conditions can cause black Eschars?
Anthrax
Rickettsia
Srub Typhus
122
What kind of bacteria is Cholera?
caused by Vibro cholerae - Gram negative bacteria
123
Whatr are the features of CHolera?
profuse 'rice water' diarrhoea
dehydration
hypoglycaemia
124
Managment of Cholera?
oral rehydration therapy
antibiotics: doxycycline, ciprofloxacin
125
What is Japanese encephalitis?
Japanese encephalitis is the most common cause of viral encephalitis in South East Asia, China the Western Pacific and India, with approx. 50,000 cases annually. It is a flavivirus transmitted by culex mosquitos which breeds in rice paddy fields. The reservoir hosts are aquatic birds, but pigs are an amplification host and therefore close domestic contact with pigs is a risk factor.
126
Symptoms of Japanese encephalitis?
The majority of infection is asymptomatic.
Clinical features are headache, fever, seizures and confusion. Parkinsonian features indicate basal ganglia involvement. It can also present with acute flaccid paralysis.
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Diagnosis of Japanese encephalitis?
Diagnosis is by serology or PCR. Management is supportive.
Prevention is a vaccine and there are a variety of different types.
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What is the H1N1 virus?
Swine Flu
The H1N1 virus is a subtype of the influenza A virus and the most common cause of flu in humans.
129
Who is particularly at risk of H1N1 influenza virus?
patients with chronic illnesses and those on immunosuppressants
pregnant women
young children under 5 years old
130
Features of swine flu?
The majority of symptoms are typical of those seen in a flu-like illness:
fever greater than 38ºC
myalgia
lethargy
headache
rhinitis
sore throat
cough
diarrhoea and vomiting
A minority of patients may go on to develop an acute respiratory distress syndrome which may require ventilatory support.
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Treatment for swine flu?
Oseltamivir (Tamiflu)
Zanamivir (Relenza)
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Mechanism of action and side effects of Oseltamivir?
a neuraminidase inhibitor which prevents new viral particles from being released by infected cells
common side-effects include nausea, vomiting, diarrhoea and headaches
133
Mechanism of action and side effecs of Zanamivir?
also a neuraminidase inhibitor
may induce bronchospasm in asthmatics
134
What is the mechanism of action of cephalosporins?
Inhibit cell wall formation by inhibiting peptidoglycan cross-linking.
## Footnote
Penicillins also inhibit cell wall formation - binds transpeptidase blocking cross-linking of peptidoglycan cell walls
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Which abx inhibit protein Synthesis?
aminoglycosides (cause misreading of mRNA)
chloramphenicol
macrolides (e.g. erythromycin)
tetracyclines
fusidic acid
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Which abx inhibit DNA synthesis and RNA synthesis?
Inhibit DNA synthesis
quinolones (e.g. ciprofloxacin)
metronidazole
sulphonamides
trimethoprim
Inhibit RNA synthesis
rifampicin
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What are streptococci and how are they classified?
Streptococci are gram-positive cocci. They may be divided into alpha and beta haemolytic types
138
Alpha haemolytic streptococci?
The most important alpha haemolytic Streptococcus is Streptococcus pneumoniae (pneumococcus). Pneumococcus is a common cause of pneumonia, meningitis and otitis media. Another clinical example is Streptococcus viridans
139
How can beta haemolytic streptococci be classified?
These can be subdivided into groups A-H. Only groups A, B & D are important in humans.
Group A
most important organism is Streptococcus pyogenes
responsible for erysipelas, impetigo, cellulitis, type 2 necrotizing fasciitis and pharyngitis/tonsillitis
immunological reactions can cause rheumatic fever or post-streptococcal glomerulonephritis
erythrogenic toxins cause scarlet fever
Group B
Streptococcus agalactiae may lead to neonatal meningitis and septicaemia
Group D
Enterococcus
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What can Group A beta haemolytic strep cause?
responsible for erysipelas, impetigo, cellulitis, type 2 necrotizing fasciitis and pharyngitis/tonsillitis
immunological reactions can cause rheumatic fever or post-streptococcal glomerulonephritis
erythrogenic toxins cause scarlet fever
141
Mechanism of actions of abx?
Cell wall - my favourite - penicillin and cephalosporins
Protein synthesis --> Core Medical Trainee is Forever Alone
- Chorampenicol
- Macrolide
- Tetracycline
- Fusidic acid
- Aminoglycosides
R*NA synthesis - R*ifampicin
DNA synthesis - Miss cutie (MS QT)
- Metro
- Sulphonamide
- Quinolone
- Trimethoprim
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who is offered HPV vaccination
The immunisation programme is aimed primarily at 12-13 years olds, both girls and boys but the vaccine is also offered to gay, bisexual, and other men who have sex with men (GBMSM) to protect against anal, throat and penile cancers.
All 12- and 13-year-olds (girls AND boys) in school Year 8 are offered the human papillomavirus (HPV) vaccine.
the vaccine is normally given in school
information given to parents and available on the NHS website make it clear that the child may receive the vaccine against parental wishes
since September 2023 one dose is now given instead of two. This change followed evidence from large studies that one dose provided equivalent protection
## Footnote
eligible GBMSM under the age of 25 also receive 1-dose, offered through sexual health clinics
eligible GBMSM aged 25 to 45 years receive a 2-dose schedule, offered through sexual health clinics
eligible individuals who are immunosuppressed or those known to be HIV-positive receive a 3-dose schedule
143
Which cancers is HPV linked to?
over 99.7% of cervical cancers
HPV testing is now integral to cervical cancer screening
samples are first tested for HPV and only if they are positive is cytology then performed
around 85% of anal cancers
around 50% of vulval and vaginal cancers
around 20-30% of mouth and throat cancers
144
Management of listeria meningitis?
IV amoxicillin and gentamicin
145
How is listeria usually spread?
Listeria monocytogenes is a Gram-positive bacillus which has the unusual ability to multiply at low temperatures. It is typically spread via contaminated food, typically unpasteurised dairy products. Infection is particularly dangerous to the unborn child where it can lead to miscarriage.
146
Risk factors for listeria?
elderly
neonates
immunosuppression
especially glucocorticoids
pregnancy
147
Features of listeria?
gastroenteritis
diarrhoea
bacteraemia
flu-like illness
central nervous system infection
meningoencephalitis
ataxia
seizures
148
Investigations for listeria?
blood cultures
'tumbling motility' on wet mounts
cerebrospinal fluid findings:
pleocytosis, often lymphocytes (nontuberculous bacteria usually cause a rise in neutrophils)
raised protein
reduced glucose
149
Management of listeria?
Listeria is sensitive to amoxicillin/ampicillin (cephalosporins usually inadequate)
Listeria meningitis should be treated with IV amoxicillin/ampicillin and gentamicin
150
Listeria in pregnant woman?
pregnant women are almost 20 times more likely to develop listeriosis compared with the rest of the population due to changes in the immune system
fetal/neonatal infection can occur both transplacentally and vertically during childbirth
complications include miscarriage, premature labour, stillbirth and chorioamnionitis
diagnosis can only be made from blood cultures
treatment is with amoxicillin
151
which anti-retroviral drugs is most characteristically associated with nephrolithiasis?
Indinavir
152
what is Lemierre's syndrome?
Lemierre's syndrome is an infectious thrombophlebitis of the internal jugular vein.
It most often occurs secondary to a bacterial sore throat caused by Fusobacterium necrophorum leading to a peritonsillar abscess. A combination of spread of the infection laterally from the abscess and compression lead to thrombosis of the IJV.
Patients will present with a history of bacterial sore throat followed by neck pain, stiffness and tenderness (may be mistaken for meningitis) and systemic involvement (fevers, rigors, etc). Septic pulmonary emboli may also occur.
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Antibiotics: bactericidal vs. bacteriostatic
Bactericidal antibiotics
penicillins
cephalosporins
aminoglycosides
nitrofurantoin
metronidazole
quinolones
rifampicin
isoniazid
Bacteriostatic antibiotics
chloramphenicol
macrolides
tetracyclines
sulphonamides
trimethoprim
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