Infectious Diseases Flashcards
what antibiotics have anti-anaerobic activity?
• Penicillins
• Cephalosporins (except ceftazidime)
• Erythromycin
• Metronidazole
• Tetracycline
which 3 antibiotics have no anti-anaerobic activity?
• Gentamicin
• Ciprofloxacin
• Ceftazidime
what is the incubation period of:
• Scarlet fever
• Influenza
• Diphtheria
• Meningococcus
1 week
what is the incubation period of:
• Malaria
• Measles
• Dengue fever
• T yphoid
1-2 weeks
what is the incubation period of:
• Mumps
• Rubella
• Chickenpox
2-3 weeks
what is the incubation period of:
• Infectious mononucleosis
• Cytomegalovirus
• Viral hepatitis
• HIV
more than 3 weeks
what type of vaccines are:
• BCG
• measles, mumps, rubella (MMR)
• oral polio
• oral typhoid
• yellow fever
-why is it important to note this?
live attenuated
-may pose a risk to immunocompromised patient
what type of vaccines are:
• rabies
• influenza
whole killed organism/inactivated
what type of vaccine is tetanus?
• tetanus: Detoxified exotoxins
what type of vaccine are:
• diphtheria
• pertussis (‘acellular’ vaccine)
• heptitis B
• meningococcus, pneumococcus, hemophilus
Fragment/Extracts of the organism or virus (may also be produced using recombinant DNA technology)
what different types of influenza vaccine exist?
different types are available, including whole inactivated virus, split virion (virus particles disrupted by detergent treatment) and sub-unit (mainly hemagglutinin and neuraminidase)
what does the vaccine for cholera contain?
contains inactivated Inaba and Ogawa strains of Vibrio cholerae together with recombinant B-subunit of the cholera toxin
what does the vaccine for hepatitis B contain?
hepatitis B: contains HBsAg adsorbed onto aluminium hydroxide adjuvant and is prepared from yeast cells using recombinant DNA technology
what may be used in hep A post-exposure prophylaxis?
• Human Normal Immunoglobulin (HNIG) or hepatitis A vaccine may be used depending on the clinical situation
what is done for hepatitis B post-exposure prophylaxis?
-if a person is a known responder to HBV vaccine
-if a person is a non-responder
• HBsAg positive source: if the person exposed is a known responder to HBV vaccine then a booster dose should be given. If they are in the process of being vaccinated or are a non- responder they need to have hepatitis B immune globulin (HBIG) and the vaccine
• Unknown source: for known responders 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 you have an accelerated course of HBV vaccine
what to do for post-exposure prophaxis for hepatitis C?
• Monthly PCR - if seroconversion then interferon +/- ribavirin
what to do for post-exposure prophylaxis for HIV?
• 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
• ↓ risk of transmission by 80%
what to do for post-exposure prophylaxis for varicella zoster?
Varicella zoster
• VZIG for IgG negative pregnant women/immunosuppressed
when is tetanus vaccine given routinely?
Tetanus vaccine is currently given in the UK as part of the routine immunisation schedule at:
• 2 months
• 3 months
• 4 months
• 3-5 years
• 13-18 years
describe what a ‘clean wound’ is?
Wounds less than 6 hours old, non-penetrating with negligible tissue damage
describe what a tetanus prone wound is?
puncture-type injuries acquired in a contaminated environment e.g. gardening injuries
wounds containing foreign bodies
compound fractures
wounds or burns with systemic sepsis
certain animal bites and scratches
describe what a high-risk tetanus prone wound is?
heavy contamination with material likely to contain tetanus spores e.g. soil, manure
wounds or burns that show extensive devitalised tissue
wounds or burns that require surgical intervention
what should be done for a patient with a clean/tetanus prone/high risk tetanus prone wound who has had full course of tetanus vaccines <10 years ago?
Patient has had a full course of tetanus vaccines, with the last dose < 10 years ago
no vaccine nor tetanus immunoglobulin is required, regardless of the wound severity
what should be done for a patient with a
-tetanus prone wound
-high-risk wound
who have had a full course of tetanus vaccine with the last dose >10 years ago?
Patient has had a full course of tetanus vaccines, with the last dose > 10 years ago
if tetanus prone wound: reinforcing dose of vaccine high-risk wounds (e.g. compound fractures, delayed surgical intervention, significant degree of devitalised tissue): reinforcing dose of vaccine + tetanus immunoglobulin
what to do with patients if vaccination history is incomplete or unknown and:
-clean wound
-tetanus prone wound
-high risk wound
If vaccination history is incomplete or unknown
reinforcing dose of vaccine, regardless of the wound severity for tetanus prone and high-risk wounds: reinforcing dose of vaccine + tetanus immunoglobulin
what are the features of tetanus?
• Prodrome fever, lethargy, headache
• Trismus (lockjaw)
• Risus sardonicus
• Opisthotonus (arched back, hyperextended neck)
• Spasms (e.g. Dysphagia)
what is used in the management of tetanus?
• Supportive therapy including ventilatory support and muscle relaxants
• Intramuscular human tetanus immunoglobulin for high-risk wounds (e.g. Compound fractures,
delayed surgical intervention, significant degree of devitalised tissue)
• Metronidazole is now preferred to benzylpenicillin as the antibiotic of choice
HIV seroconversion:
-how many people is this symptomatic in?
-how does this present?
-when does this occur?
-what conveys poorer long term prognosis?
HIV seroconversion is symptomatic in 60-80% of patients and typically presents as a glandular fever type illness. ↑ symptomatic severity is associated with poorer long term prognosis. It typically occurs
3-12 weeks after infection
Man returns from trip abroad with maculopapular rash and flu-like illness - think ?
Man returns from trip abroad with maculopapular rash and flu-like illness - think HIV seroconversion
what are the features of HIV seroconversion?
• Sore throat
• Lymphadenopathy
• Malaise, myalgia, arthralgia
• Diarrhoea
• Maculopapular rash
• Mouth ulcers
• Rarely meningoencephalitis
what is the diagnosis of HIV?
• Antibodies to HIV may not be present
• HIV PCR and p24 antigen tests can confirm
diagnosis
what immunological changes are seen in progressive HIV?
• Reduction in CD4 count
• Increase B2-Microglobulin (IBM)
• Decrease IL-2 production (DIL=DELL)
• Polyclonal B-cell activation
• ↓ NK cell function
• ↓ delayed hypersensitivity responses
what vaccines can only be used in HIV patients who’s CD4 count is >200?
Measles, Mumps, Rubella (MMR) ● V aricella●
Yellow Fever●
what vaccines are contraindicated in HIV patients?
Cholera* CVD103-HgR● Influenza-intranasal● Poliomyelitis-oral (OPV) ● Tuberculosis (BCG) ●
what type of virus in HIV and what are the 2 variants?
HIV is a RNA retrovirus of the lentivirus genus (lentiviruses are characterized by a long incubation period)
two variants - HIV-1 and HIV-2
HIV-2 is more common in west Africa, has a lower transmission rate and is thought to be less pathogenic with a slower progression to AIDS
describe the basic structure of HIV
Basics structure
spherical in shape with two copies of single-stranded RNA enclosed by a capsid of the viral protein p24 a matrix composed of viral protein p17 surrounds the capsid envelope proteins: gp120 and gp41 pol gene encodes for viral enzymes reverse transcriptase, integrase and HIV protease
how does this HIV virus enter cells?
Cell entry
HIV can infect CD4 T cells, macrophages and dendritic cells
gp120 binds to CD4 and CXCR4 on T cells and CD4 and CCR5 on macrophages
mutations in CCR5 can give immunity to HIV
describe how HIV replicates in cells?
Replication
after entering a cell the enzyme reverse transcriptase creates dsDNA from the RNA for integration into the host cell’s genome
what are the most common causes of diarrhoea in HIV?
Diarrhea is common in patients with HIV. This may be due to the effects of the virus itself (HIV enteritis) or opportunistic infections
Possible causes
• Cryptosporidium + other protozoa (most
common)
• Cytomegalovirus
• Mycobacterium avium intracellulare • Giardia
what is the most common cause of diarrhoea in HIV patients?
-what is the incubation period?
Cryptosporidium is the most common infective cause of diarrhoea in HIV patients. It is an intracellular protozoon and has an incubation period of 7 days.
describe the presentation and staining used for cryptosporidium in HIV?
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.
what is the management for cryptosporidium diarrhoea in HIV patients?
Treatment is difficult, with the mainstay of management being supportive therapy. (nitazoxanide is licensed in the US for immunocompetent patients)
what mycobacterium is seen in HIV patients with a CD4 count below 50?
Mycobacterium avium intracellulare is an atypical mycobacteria seen with the CD4 count is below 50.
what are the features of mycobacterium avium intracellulare in HIV patients?
Typical features include fever, sweats, abdominal pain and diarrhoea. There may be hepatomegaly and deranged LFTs.
what is the diagnosis and management of mycobacterium avium intracellulare in HIV patients?
Diagnosis is made by blood cultures and bone marrow examination.
Management is with rifampicin, ethambutol and clarithromycin
what factores can decrease vertical transmission of HIV?
Factors which ↓ vertical transmission (from 25-30% to 2%)
• Maternal antiretroviral therapy
• Mode of delivery (caesarean section)
• Neonatal antiretroviral therapy
• Infant feeding (bottle feeding)
which pregnant women should be screened for HIV?
Screening
• NICE guidelines recommend offering HIV screening to all pregnant women
Pregnant patients with HIV:
-who should be offered antiretroviral therapy?
-when should antiretroviral therapy be offered if women are not currently taking it and are pregnant?
Antiretroviral therapy
• All pregnant women should be offered antiretroviral therapy regardless of whether they were
taking it previously
• If women are not currently taking antiretroviral therapy it is usually commenced between 28
and 32 weeks of gestation and should be continued intrapartum
what mode of delivery is preferable in HIV positive pregnant ladies?
Mode of delivery
• Elective caesarean section
• A zidovudine infusion should be started four hours before beginning the caesarean section
what is usually administered orally to the neonate of a HIV positive mother? how long should this be used for?
Neonatal antiretroviral therapy
• Zidovudine is usually administered orally to the neonate for four to six weeks
what is kaposi’s sarcoma caused by?
• Caused by HHV-8 (Human Herpes Virus 8)
how can kaposi’s sarcoma present?
• 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
hemoptysis and pleural effusion
what is the treatment for kaposi sarcoma?
• Radiotherapy + resection
Pneumocystis carinii pneumonia - who is this common in? and who should recieve prophylaxis?
(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
what are the features of PCP pneumonia?
• Dyspnea
• Dry cough
• Fever
• Very few chest sign
what rare Extrapulmonary manifestations for PCP pneumonia exist?
• Hepatosplenomegaly
• Lymphadenopathy
• Choroid lesions
what is seen on CXR in PCP pnuemonia?
• CXR: typically shows bilateral interstitial pulmonary infiltrates but can present with other x-ray
findings e.g. lobar consolidation. May be normal
what is a clinical feature of PCP pneumonia?
• Exercise-induced desaturation
what investigation can be done for PCP pneumonia?
• Sputum often fails to show PCP, bronchoalveolar lavage (BAL) often needed to demonstrate
PCP (silver stain)
what is the most common cause of biliary disease in patients with HIV?
The most common cause of biliary disease in patients with HIV is sclerosing cholangitis due to
infections such as CMV, Cryptosporidium and Microsporidia
what may pancreatitis in the context of HIV infection be secondary to?
Pancreatitis in the context of HIV infection may be secondary to anti-retroviral treatment
(especially didanosine) or by opportunistic infections e.g. CMV
Describe the CSF findings in bacterial meningitis?
Appearance
Glucose
Protein
White cells
Appearance- cloudy
Glucose - low (<1/2 plasma)
Protein - high (>1g/l)
White cells - 10-5000 polymorphs
Describe the CSF findings in viral meningitis?
Appearance
Glucose
Protein
White cells
Appearance - clear/cloudy
Glucose - normal
Protein - normal/raised
White cells - 15-1000 lymphocytes
Describe the CSF findings in TB meningitis?
Appearance
Glucose
Protein
White cells
Appearance - fibrin web
Glucose - low (<1/2 plasma)
Protein - high (>1g/l)
White cells - 10-1000 lymphocytes
what is used in the detection of TB meningitis?
The Ziehl-Neelsen stain is only 20% sensitive in the detection of tuberculous meningitis and therefore PCR is sometimes used (sensitivity = 75%)
what is the management for meningitis:
Initial empirical therapy aged < 3 months or >50
Intravenous cefotaxime + amoxicillin
Intravenous dexamethasone should also be given to reduce the risk of neurological sequelae.
what is the management for meningitis:
Initial empirical therapy aged 3 months - 50 years
Intravenous cefotaxime if adult, IV ceftriaxone if child
Intravenous dexamethasone should also be given to reduce the risk of neurological sequelae.
what is the treatment for menigococcal meningitis?
Intravenous benzylpenicillin or cefotaxime
Intravenous dexamethasone should also be given to reduce the risk of neurological sequelae.
what is the treatment for penumococcal meningitis or meningitis caused by haemophilus influenzae?
Intravenous cefotaxime
Intravenous dexamethasone should also be given to reduce the risk of neurological sequelae.
what is the treatment for meningitis caued by listeria?
Intravenous amoxicillin + gentamicin
Intravenous dexamethasone should also be given to reduce the risk of neurological sequelae.
what is used for a patient with meningitis with a history of immediate hypersensitivity to penicillin or to cephalosporin?
If the patient has a history of immediate hypersensitivity reaction to penicillin or to cephalosporins the BNF recommends using chloramphenicol.
who should be offered antibiotic prophylaxis for meningitis?
-what is the high risk period?
prophylaxis needs to be offered to household and close contacts of patients affected with meningococcal meningitis.
Prophylaxis should also be offered to people who been exposed to respiratory secretion, regardless of the closeness of contact people who have been exposed to a patient with confirmed bacterial meningitis should be given prophylactic antibiotics if they have close contact within the 7 days before onset
the risk is highest in the first 7 days but persists for at least 4 weeks
what is used for meningitis prophylaxis?
oral ciprofloxacin or rifampicin or may be used. The Health Protection Agency (HPA) guidelines now state that whilst either may be used ciprofloxacin is the drug of choice as it is widely available and only requires one dose
when should meningococcal vaccination be given to close contacts? what about of pneumococcal meningitis?
meningococcal vaccination should be offered to close contacts when serotype results are available, including booster doses to those who had the vaccine in infancy
for pneumococcal meningitis, no prophylaxis is generally needed. There are however exceptions to this. If a cluster of cases of pneumococcal meningitis occur the HPA have a protocol for offering close contacts antibiotic prophylaxis.
what are the investigations for meningococcal septicaemia?
• Blood cultures
• Blood PCR, if antibiotic was already started.
• Lumbar puncture is usually contraindicated
• Full blood count and clotting to assess for disseminated intravascular coagulation
what may streptococci be subdivided into?
may be divided into α haemolytic and β hemolytic types
give two α hemolytic Streptococci?
The most important α hemolytic Streptococcus is Streptococcus pneumoniae (pneumococcus). Pneumococcus is a common cause of pneumonia, meningitis and otitis media. Another clinical example is Streptococcus viridans
how can you subdivide β hemolytic streptococci?
Group A and Group B
Group A strep:
-most important organism
-what can this cause?
-what is the antibiotic of choice?
• Most important organism is Streptococcus pyogenes
• Responsible for erysipelas, impetigo, cellulitis, type 2 necrotizing fasciitis & pharyngitis/tonsillitis • Immunological reactions can cause rheumatic fever or post-streptococcal glomerulonephritis
• Erythrogenic toxins cause scarlet fever
• Penicillin is the antibiotic of choice for group A streptococcal infections
Group B strep:
-what organism is under this and what does it cause?
• Streptococcus agalactiae may lead to neonatal meningitis and septicemia
what are the most common causes of cellulitis?
Streptococcus pyogenes or Staphylcoccus aureus.
what classification is used for cellulitis and describe each class?
Eron classification
Class Features
I There are no signs of systemic toxicity and the person has no uncontrolled co-morbidities
II The person is either systemically unwell or systemically well but with a co-morbidity (for example peripheral arterial disease, chronic venous insufficiency, or morbid obesity) which may complicate or delay resolution of infection
III The person has significant systemic upset such as acute confusion, tachycardia, tachypnoea, hypotension, or unstable co-morbidities that may interfere with a response to treatment, or a limb-threatening infection due to vascular compromize
IV The person has sepsis syndrome or a severe life-threatening infection such as necrotizing fasciitis
what is the criteria for admission for cellulitis?
Has Eron Class III or Class IV cellulitis.
Has severe or rapidly deteriorating cellulitis (for example extensive areas of skin).
Is very young (under 1 year of age) or frail.
Is immunocompromized.
Has significant lymphoedema.
Has facial cellulitis (unless very mild) or periorbital cellulitis.
how is eron class II cellulitis managed?
Admission may not be necessary if the facilities and expertise are available in the community to give intravenous antibiotics and monitor the person - check local guidelines.
what is the management of cellulitis:
-first line
-if penicillin allergic
-if pregnant
-if severe
The BNF recommends flucloxacillin as first-line treatment for mild/moderate cellulitis. Clarithromycin, erythromycin (in pregnancy) or doxycyline is recommended in patients allergic to penicillin.
NICE recommend that patients severe cellulitis should be offered co-amoxiclav, cefuroxime, clindamycin or ceftriaxone.
what is the diagnostic criteria for staphylococcal toxic shock syndrome?
Centers for Disease Control and Prevention diagnostic criteria
• Fever: temperature > 38.9oc
• Hypotension: systolic blood pressure < 90 mmHg
• Diffuse erythematous rash
• Desquamation of rash, especially of the palms and soles
• Involvement of three or more organ systems: e.g. Gastrointestinal (diarrhoea and vomiting),
mucous membrane erythema, renal failure, hepatitis, thrombocytopenia, CNS involvement (e.g. Confusion)
what is type 1 and type 2 necrotising fasciitis?
It can be classified according to the causative organism:
• Type 1 is caused by mixed anaerobes and aerobes (often
occurs post-surgery in diabetics)
• Type 2 is caused by Streptococcus pyogenes
what are the features of nec fasciitis?
Features
• Acute onset
• Painful, erythematous lesion develops (cellulitis like)
• Extremely tender over infected tissue
what is the management for necrotising fasciitis?
Management
• Urgent surgical debridement
• IV antibiotics
what type of bacteria is listeria monocytogenes?
-how is this usually spread?
-what is the complication in pregnancy?
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
how can listeria monocytogenes present?
Features - can present in a variety of ways
• Diarrhoea, flu-like illness
• Pneumonia , meningoencephalitis
• Ataxia and seizures
how should suspected listeria infection be investigated?
Suspected Listeria infection should be investigated by taking blood cultures. CSF may reveal a
pleocytosis, with ‘tumbling motility’ on wet mounts
what is the management of listeria?
Management
• Listeria is sensitive to amoxicillin/ampicillin (cephalosporins usually inadequate)
• Listeria meningitis should be treated with IV amoxicillin/ampicillin and gentamicin
what is anthrax?
-what type of organism is this?
-how is this spread?
Anthrax is caused by Bacillus anthracis, a Gram positive rod. It is spread by infected carcasses
what are the features of anthrax?
Features
• Causes painless black eschar (cutaneous ‘malignant pustule’, but no pus)
• Typically painless and non-tender
• May cause marked edema
• Anthrax can cause gastrointestinal bleeding
what is the management of anthrax?
Management
• The current Health Protection Agency advice for the initial management of cutaneous anthrax is ciprofloxacin
• Further treatment is based on microbiological investigations and expert advice
who should be screened for MRSA?
• All patients awaiting elective admissions (exceptions include day patients having terminations
of pregnancy and ophthalmic surgery. Patients admitted to mental health trusts are also
excluded)
• From 2011 all emergency admissions will be screened
how is a patient screened for MRSA?
• Nasal swab and skin lesions or wounds
• The swab should be wiped around the inside rim of a patient’s nose for 5 seconds
• The microbiology form must be labelled ‘MRSA screen’
what can be used to suppress MRSA in a carrier once identified?
• 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
what antibiotics can be used for MRSA infections?
The following antibiotics are commonly used in the treatment of MRSA infections:
• Vancomycin
• Teicoplanin
Legionnaire’s disease:
-what is this caused by?
-how is this spread?
Legionnaire’s disease is caused by the intracellular bacterium Legionella pneumophilia. It is typically colonizes water tanks and hence questions may hint at air-conditioning systems or foreign holidays. Person-to-person transmission is not seen
what are the features of legionnaires disease?
• Flu-like symptoms
• Dry cough
• Lymphopenia
• Hyponatremia
• Deranged LFTs
what is the diagnosis of legionnaires?
Urinary antigen
what is the treatment of legionnaires?
• Treat with erythromycin
Leptospirosis is AKA? what demographic of people are affected?
leptospirosis is commonly seen in questions referring to sewage workers, farmers, vets or people who work in abattoir.
The term Weil’s disease referrs for the most severe 10% of cases of leptospirosis associated with jaundice
what is leptospirosis caused by? how is this transmitted?
It is caused by the spirochaete Leptospira interrogans (serogroup L icterohemorrhagiae), classically being spread by contact with infected rat urine.
when should weil’s disease be considered?
Weil’s disease should always be considered in high-risk patients with hepatorenal failure.
what are the features of leptospirosis?
• Fever
• Flu-like symptoms → WITHOU PRODUCTIVE COUGH
• Renal failure (seen in 50% of patients)
• Jaundice
• Subconjunctival hemorrhage
• Headache, may herald the onset of meningitis
what is the management of leptospirosis?
• A lumbar puncture should ideally be done first to confirm meningeal involvement, if there are meningeal symptoms.
• High-dose benzylpenicillin or doxycycline
what is acute epiglottitis caused by?
-who does this occur in?
Acute epiglottitis is rare but serious infection caused by Hemophilus influenzae type B. Prompt recognition and treatment is essential as airway obstruction may develop. Epiglottitis generally occurs in children between the ages of 2 and 6 years. The incidence of epiglottitis has ↓ since the introduction of the Hib vaccine
what are the features of acute epiglottitis?
Features
• Rapid onset
• Unwell, toxic child
• Stridor
• Drooling of saliva
what is lyme disease caused by?
Lyme Disease: or borreliosis is an emerging infectious disease caused by at least three species of bacteria belonging to the genus Borrelia. Borrelia burgdorferi sensu stricto is the main cause of Lyme disease in the United States, whereas Borrelia afzelii and Borrelia garinii cause most European cases.
describe the early features of lyme disease
Early features
• Erythema chronicum migrans (small papule often at site of the tick bite which develops into a larger annular lesion with central clearing, occurs in 70% of patients)
• Systemic symptoms: malaise, fever, arthralgia
what are the later features of lyme disease?
Later features
• CVS: heart block, myocarditis
• Neurological: cranial nerve palsies, meningitis
• Polyarthritis
what is used to screen for latent TB?
The Mantoux test is the main technique used to screen for latent tuberculosis. In recent years the interferon-gamma blood test has also been introduced. It is used in a number of specific situations such as:
the Mantoux test is positive or equivocal people where a tuberculin test may be falsely negative (see below)