Infectious disease 3 Flashcards
management of toxoplasmosis in immunocompetent patient?
Immunocompetent patients with toxoplasmosis don’t usually require treatment
What is toxoplasmosis?
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.
What is Chancroid?
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.
What is the mechanism of action of amantadine as an antiviral?
Inhibits uncoating (M2 protein) of virus in cell. Also releases dopamine from nerve endings
Management of Gonorrhoea?
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
What does bone marrow aspirate show in viceral leishmaniasis?
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.
Causes of Diarrhoe in patients with HIV?
Cryptosporidium + other protozoa (most common)
Cytomegalovirus
Mycobacterium avium intracellulare
Giardia
What is the most common cause of diarrhoea in patients with HIV?
What is the treatment?
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
When is Mycobacterium avium intracellulare seen? What are the featues? How is it managed?
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
Management of Syphillis?
IM ben pen
(alternative is doxycyline)
What should be monitored after syhillis managed?
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
What is Jarisch-Herxheimer reaction?
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
HIV management?
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
What are examples of 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
What are examples of nucleoside analogue reverse transcriptase inhibitors?
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
What are examples of non-nucleoside reverse transcriptase inhibitors?
Non-nucleoside reverse transcriptase inhibitors (NNRTI)
examples: nevirapine, efavirenz
side-effects: P450 enzyme interaction (nevirapine induces), rashes
What are examples of protease inhibitors?
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
What are examples of integrase inhibitors?
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
What should be done if Anti-HBs levels are low following Hep B vaccination?
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.
what kind of virus is hep B?
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.
Features of hep B ?
The features of hepatitis B include fever, jaundice and elevated liver transaminases.
Complications of Hep B infection?
chronic hepatitis (5-10%). ‘Ground-glass’ hepatocytes may be seen on light microscopy
fulminant liver failure (1%)
hepatocellular carcinoma
glomerulonephritis
polyarteritis nodosa
cryoglobulinaemia
Which groups of people should be vaccinated against hep B?
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
Management of hep B?
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)
What cause of pneumonia is associated with caviatin lesions?
Staph aureus
Legionella is associated with what when it causes pneumonia?
Deranged LFTs
. Other features include hyponatraemia, headache and dry cough
what cause of pneumonia is associated with cold sores?
Streptococcus pneumoniae
Stereotypical histories of gastroenteritis?
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
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
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
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
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.
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
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.
How do you treat cysticercosis?
bendazoles
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.
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
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.
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
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
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.
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
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).’
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
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
What type of parasite is toxoplasmosis?
an obligate intracellular protozoan parasite
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.
what types of HPV predispose to genital warts?
6&11
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
Genital wart treatment
multiple, non-keratinised warts: topical podophyllum
solitary, keratinised warts: cryotherapy
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
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
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.
Mechanism of action of trimethoprim?
interferes with DNA synthesis by inhibiting dihydrofolate reductase
may, therefore, interact with methotrexate, which also inhibits dihydrofolate reductase
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.’
What type of Abx inhibit protein synthesis?
Buy AT 30
Aminoglycosides
Tetracyclines
CELL for 50
Clindamycin
Erythromycin
Linezolid
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.
Features of leprosy?
Features
patches of hypopigmented skin typically affecting the buttocks, face, and extensor surfaces of limbs
sensory loss
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
How is Leprosy managed?
WHO-recommended triple therapy: rifampicin, dapsone and clofazimine
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
