Infection Flashcards
What is gastro enteritis?
3+ loose stools/day
With accompanying features
What causes gastroenteritis?
Contamination of foodstuffs (eg chicken)
Poor storage (allowing proliferation of bacteria)
Travel related infections
Person-person spread - norovirus
What bacteria is the most common foodborne pathogen?
Campylobacter
Which bacteria causes the most hospital admissions for food poisoning?
Salmonella
Types od diarrheal illness
Non-inflammatory/secretory (cholera)
Inflammatory - shingella
Mixed (c.diff)
Describe secretory/non-inflammatory diarrhoea
Secretory toxin-mediated
I.E - cholera raises cAMP levels + cl secretion
Frequent watery stools - little abdominal pain
Rehydration for therapy
Describe inflammatory diarrhoea
Toxin damage causes inflammation + mucosal destruction
Causes pain + fever
Bacterial infection
Often rehydration sufficient. Sometimes antimicrobials
How long does gastroenteritis last?
Normally less than 2 weeks
Investigations into gastroenteritis
Stool culture Blood culture Renal function (dehydration) Blood count Abdominal xray if distended abdomen
What are the differentials of gastroenteritis?
inflammatory bowel disease
Spurious diahrroea
Carcinoma
Define campylobacter gastroenteritis
Up to 7 days incubation
Stools negative within 6 weeks
Severe abdominal pain
Very unlikely to be invasive (into blood <1%)
What can campylobacter gastroenteritis lead to?
Guillian barre syndrome
Reactive arthritis
Define salmonella gastroenteritis
Symptoms usually within 48 hours
Diahrroea lasts for less than 10 days
<5% invasive
20% still have positive stools 20 weeks later
Bacterial cultures - differences
Salmonella are lactose non-fermenters
Campylobacter needs specialised conditions
What are the most common salmonella strains in UK
Salmonella enteritidis
Salmonella typhimurium
Most are imported
What salmonella cause enteric fever?
Salmonella typhi
Salmonella paratyphi
Why strain of e.coli causes gastroenteritis?
E.coli O157
What is characterisitc of E.Coli O157 gastroenteritis?
Frequent bloody stools
Produces toxins which causes harmolytic-uraemic syndrome
E.Coli stays in blood, but toxin enters blood
Often from contminated meat or person to person spread
What is HUS? (haemolytic-ureamic syndrome)
Renal failure
Haemolytic anaemia
Thrombocytopenia
Through binding of globotriaosylceramide
What bacteria cause gastroenteritis outbreaks?
Staph A
Bacillus cereus (from refriend rice)
Clostridium perfringens
When are antibiotics indicated for gastroenteritis?
In immunocomprimised Severe sepsis/invasive infection Valvular heart disease Diabetes Chronic illness
How do you treat c.diff infection?
Metronidazole - First line, no severity markers
Oral vancomycin - 2+ severity markers
Fidaxomaicin
Stool transplants
How do you prevent C.diff
Avoid the 4 c antibiotics Isolate symotomatic patients Wash ahnds (not alcohol gel) between patients
What are the 4 antibiotics to avoid to prevent c.diff
Cephalosporins
Co-amoxiclav
Clindamycin
Clarithromycin
How do you request a parasite screen?
Parasites, cysts + ova
What are the common UK parasites?
Giardia lamblia
Cryptosporidium parvum
Describe Giardia lamblia
Found in contaminated water
Causes diarrhoea, malabsorption + failure to thrive
Cysts seen on stool micropsopy
Treat with metronidazole
Describe Cryptosporidium parvum
Found in contaminated water (animal faeces)
Cysts on micropscopy
No specific treatment required
What is entamoeba histolytica
Parasite causing amoebic dysentery Vegitive form in symptomatic patients - hot stools Cysts in asymptomatic patients May cause liver abscesses long term Treat with metronidazole
What is viral diarrhoea
Common in winter
Often rotaviruses
Sometimes adenoviruses
Common cause of outbreaks (hospital, community, cruise ships)
What are noraviruses
Small round structured viruses Diagnosed through PCR Very infectious Infect through airbourne particles Need strict infection control measures Ward closures common
What is SIRS?
Temperature change ->38 or <36 HR > 90 RR>20 or paCO2 <32 WBCs - >12000 or <4000
What is sepsis?
An infection of blood along with SIRS
What is the mortality with septic shock?
40%
What is qSOFA?
Hypotension - Systolic <100mmHg
Altered mental state
Tachypnea (Resp rate >22)
Score of 2 or more indicates high risk of poor outcome
What is Sepsis 6?
Blood cultures
|-> From two-three different sites, before antibiotics start
Blood lactate
Measure urine output
Oxygen
IV antibiotics
IV fluids
Why is lactate important in sepsis?
A marker of generalised hypoperfusion/severe sepsis/poor prognosis
Type A indicated Hypoperfusion
Type B - mitochondrial toxins, alcohol, malignancy, metabolism errors
When should you refer a septic patient to ITU?
Septic shock
Multi-organ failure
Needing sedation, intubation or ventilation
When should you refer a septic patient to HDU?
Low BP Lactate >2 despite resus Elevated creatinine Oliguria Liver dysfunction Bilateral infiltrates
What is a pyrexia of unkown origin?
No diagnosis after 3 outpatient visits
3 days in hospital
Or one week of outpatient investigation
What is a fabricated fever?
A real fever that is induced by patient ie inject self with foreign material (eg faeces)
Microbiology strongest clue
What is the difference between colonisation and infection?
Colonisation is presence on surfaces open to environment
Infection is presence inside the body that causes damage to body/tissues
Which bactera are spread through direct contact?
Staph A
Coliforms
Which bactera are spread through respiratory/droplets?
Neisseria meningitidis
Mycobacteria tuberculosis
Which bactera are spread through faecal oral?
Clostridium difficile
Salmonella
Which bactera are spread through Penetrating injury?
Group A streptococcus
Blood bourne viruses
What are the modes of HIV infection?
Sexual - mostly MSM in this country
Injecting drug users
Blood products
Organ transplant
What is the virology of HIV?
A type of retrovirus (lentivirus) that attaches to cells with CD4 on surface (lymphocytes) and other chemokine receptors
Uses reverse transcriptase to replicate
Uses integrase to integrate into host cell DNA
What is the main strain of HIV?
HIV-1 group M
What does an HIV infection do to the CD4 count?
Decreases it
What is the CD4 level for AIDS diagnostics?
Below 200
What are the most common (new) opportunistic infections in HIV?
Pneumocytis jiroveci pneumoia
Candidiasis
Mycobacterium avium complex
Cryptosporidious
What are the most common reactivation opportunistic infections in HIV?
Cerebral toxoplasmosis
TB
CMV disease
What is the natural history of HIV?
Acute infection (seroconversion) Asymptomatic HIV related illness AIDS-defining illness Death
What is a seroconversion illness?
When HIV antibodies first develop
Has abrupt onset 2-4 weeks post exposure
Self limiting - lasts 1-2 weeks
What are the symptoms for seroconversion illness
Flu-like illness Fever Malaise/lethargy Pharyngitis Lympjadenopathy Toxic exanthema
Looks like glandular fever but EBV not in keeping
How do you determine length of HIV infection?
If seroconversion illness, date of that
Else stored blood
Else most at risk
What are the respiratory AIDS-defining conditions?
TB
Pneumocystisis
What are neurology AIDS-defining conditions?
Cerebral toxoplasmosis
Primary cerebral lymphoma
Crytptococcal meningitis
Progressive multifocal leucoencephalopathy
What are the dermatology AIDS-defining conditions?
Kaposi’s sarcoma
What are the gastroenterology AIDS-defining conditions?
Persistant cryptosporidosis
What are the Oncology AIDS-defining conditions?
Non-hodgkin’s lymphoma
What are the Gynaecology AIDS-defining conditions?
Cervical cancer
What are the optholomology AIDS-defining conditions?
Cytomegavirus retinitis
How is HIV monitored?
CD4 lymphocyte count
HIV viral load
Clinical features
What is the current treatment for HIV therapy?
Combincation antiretroviral therapy - with 3 drugs from at least 2 groups
What do the different HIV drugs act on?
Different stages of HIV lifecycle
What is the adherance to medication needed to supress HIV? Can this lead to a normal life?
Adherance must be over 90%
cART can lead to a normal life but side effects can be significant
i.e metabolic, lipodystrophy
What are the three main types of medication MOAs for HIV?
Reverse transcriptase inhibtor
Integrase inhibitor
Protease inhibitor (prevents release of new virus)
When should you start HIV treatment?
If CD4 drops below 350cells/mm OR rapidly falling
What is the life expectancy based off CD4 of less than 100 before starting therapy?
52
What is the life expectancy based off CD4 of 100-200 before starting therapy?
62
What is the life expectancy based off CD4 of more than 200 before starting therapy?
70+
Why do HIV treatments fail?
Poor adherance
Not strong enough etc
All leads to viral mutation + resistance
What are the side effects of nucleoside reverse transcriptase inhibitors (HIV drug)?
Marrow toxicity
Neuropathy
Lipodystrophy
What are the side effects of non-nucleoside reverse transcriptase inhibitors drugs (HIV)?
Skin rashes
Hypersensitivity
Drug interactions
What are the side effects of protease inhbitors? (HIV drug)
Drug interactions
Diarrhoea
Lipodystrophy
HYperlipidaemia
What are the side effects of itegrase inhbiitors? (HIV drug)
Rashes
How can you reverse the effects of lipodystrophy (side effect from HIV medication?)
Change drugs Cosmetic procedures Facelift Liposuction Fillers
What is the relationship between HIV and cardiovascular diseae?
Increased MI incidence
Hyperlipidaemia
Insulin resistance
What are the main challenges of HIV care in this day and age?
Osteoporosis Cognitive impairment Malignancy Cerebrovascular disease Renal disease diabetes mellitus Ischaemic heart disease
How can you prevent HIV?
Change behaviour (condoms)
Treatment as prevention
Pre-exposure prophylaxis
Post-exposure prophylaxis
What are the risks of transmission for percutaneous exposure?
HBV positive - 30%
HCV RNA positive blood - 3%
HIV positive blood - 0.3%
What is the mucotaneous exposure of HIV positive blood? (Fluid entering eyes, nose, mouth or broken skin)
0.1%
What fluids have to be handled with the same precautions as blood?
CSF Pleural, peritoneal or pericardial fluid Breast milk Amniotic fluid Vagical secretions or semen Synovial fluid Unfixed tissues/organs Saliva Exudate/tissue fluid from burns or skin lesions
What actions should be taken after bodily fluid exposure?
Wash off splashes on skin with soap/running water
Encorage bleeding
Report to sensior manager or doctor + OHS
How is the risk assesed for bodily fluid exposure?
Source of contamination
Extendt of injury and type of sharp causing it
Liklihood of virus in source
Vaccination history
What is an HAI (healthcare acquired infection?)
Infections that weren’t present at time of admission
Or an infection that arises after 48 hours of admission or within 48 hours of discharge
What is the prevelance of HAIs?
4.9% of all patients in scotland
What are the most common HAIs?
UTI (mainly due to cathertisation) 22.6%
Surgical site infection18.6%
Respiratory tract infection 17.5% (intubation)
Bloodstream infections (catheter related)
GI
Skin + soft tissue
What microbial factors make infection more likely?
Increased resistance Increased virulence Increased transmissability Increased survivability Ability to evade hosts immune
What host factors make HAIs more common?
Devices (catheters etc) Antibiotics taken incorrectly Break in skin Foreign body Immunosuppresion Age extremes Overcrowding
What are the stages in the chain of infectio?
Source of microbe
Tranismission
Host
What are the means of transmission for infections?
Direct contact
Respiratory/droplet
Faecal oral
Penetrating injury
How can you break the chain of infection?
Risk awareness Hand hygiene Appropriate PPE Vaccination Post exposure prophylaxis Standard infection prevention and control precautions
What is the definition of cleaning?
Physical removal of organic material + decreasing microbial load
What is the definition of disinfection?
Large reduction in micrbe numbers, spores may remain
What is the definition of sterilisation?
Removal/destruction of all microbes and spores
When is cleaning appropriate?
Low risk procedures (intact skin contact)
I.e stethoscopes
Cots
Mattresses
When is disinfection appropriate?
Medium risk procedures - mucous membrane contact
Endoscopes
Vaginal specula etc
When is sterilisation appropriate?
High risk (and sometimes medium risk) Eg surgical instruments
What is the cleaning process?
Detergent + water
DRY
Cleaning essential before disinfection + sterilisation if required
What are the methods of disinfection?
Heat (pastureisation/boiling)
Chemical (alcohol etc)
What are the methods of sterilsation?
Steam under pressure
Hot air oven
Gas
Ionising radiation
What is the definition of an outbreak?
2 or more infections linked in time and palce
What are the control measure in an outbreak?
Single room isolation Cohorting of cases Clinical area or ward closure Staff exclusion Staff decolonisation
What are the three main groups of influenza?
A (mammals and birds)
B + C (only humans)
What family does influenza belong to?
Orthomyoxviridae family
8 segment RNA virus
What is antigenic drift?
Mechanism of viral genetic variation
Occurs continually over time by small point mutations
What do the changes in antigenic drift lead to?
Changes the antigenic properties - eventually immune system will not cope as well
Causes worse than normal epidemics + vaccine mismatch
What is antigenic shift?
An abrupt major change in virus - leads to new H/N combinations
This is what allows for strains to jump from one species to another
What can antigenic shift lead to?
Combination of multiple strians to form a new subtype
Reassortment of genome
This can lead to pandemics
What are the differences between seasonal flue and pandemic flu?
Seasonal - every winter
Pandemic sporadically
Seasonal - 10-15% of population
Pandemic - 25%+ of population
Seasonal - unpleasant, not life-threatening
Pandemic - life threatening
What are the two surface proteins on influenza?
Haemaglutinin (H)
Neuramindiase (N)
How many different haemaglutinin antigens are there?
18 (H1-3 affect humans)
How many different N antigens are there?
11
What is the function of haemaglutinin surface protein?
Facilitats viral attachment and entry to host cell
What is the function of neuramindiase surface protein of influenza?
Enables new viron to be released from host cell
What two strains of avian bird flue affect ?humans
H5N1
H7N9
What are the fatality rates of avian flu?
H5N1 - 60%
H7N9 - 35%
What is the incubation period for avian flu?
2-4 days
What are the transmission modes for avian flu?
Direct contact with infected birds (dead or alive)
Occasional transmission with human contact
No know contact by eating properly cooked poultry
What are the clinical features of influenza?
Fever lasting ~ 3 days
+ 2 or more of:
Cough, sore throat, rhinorrhoea, myalgia, headache, malaise
Mostly systemic symptoms
What are the symptoms of swine flu?
Sudden fever + cough
Tiredness, chills
Heaache, sore throat, runny nose, sneezing
Diarrhoea, stomach upset loss of appeitte
Aching muscles, limb or joint pain
What is the tranmission mode for flu?
Aiborne (person to person by large droplets)
Contact - direct vs indirect
How long does the virus survive outside the host?
24-48 hours on no porous surfaces
8-12 hours on porous surface (eg tissue)
What are the high risk groups for catching influenza?
Chronic disease Diabtetes mellits Severe immunosuprresion 65+ Pregant women Children under 6 Morbid obesity
What are common complications of influenza?
Acute bronchitis
Seoncary bacterial penumonia (4-5 days after surgery)
What are some uncommon complcaitions associated with influenza?
Primary viral pneumonia
Myocarditis/pericarditis
Transverse myelitis / guillian barre
Myositis & myoglobinuria
How do you diagnose influenza?
Clinical diagnosis Viral nose/throat swabs Chest x-ray Blood culture Resp rate/pule oximetry U&Es, FBC, CRP
what is the assesment for penumonia?
CURB65 Confusion Urea ?7mmol/l Resp rate >30 Blood pressure (diastolic <60, systolic <90) 65+
What are the two types of antivirals for flu?
Osetamivir (tamiflu) - taken orally
Zanamivir (relenza) - inhaled dry poweder
What areh the side effects of selatamir (tamiflu)?
Common - Nausea, vomitting, abdo pain, diarrhoea
Less common - Headache, hallucinations, insomina + rash
Cautions - renal dosing needed
What are the side effects for zanamivir (relenza)?
Rare - occasional bronchospasm
What is the first + second line in a complicated influenza (not immunocomprimised + immunocomromised)?
Osteamivir PO - 1st line
Zanamivir - 2nd line
What is the treatment for uncomplicated influnza?
No treatment preferred
Osteltamivir PO within 48 hours if at risk of developing complications
What treatment for immunocomprised patients with uncomplicated influenzae?
Oseltamivir PO + commence therapy within 48 hours
What is the treatment in pregancy for influenza?
Antivirals with oseltamivir being first line
Also safe in breastfeeding.
When does a patient become non-infections
24 hrs after last symptom (or after treatment if that is longer)
In immunocomprimised - cases differ
What PPE is needed for healthcare staff in influnzae?
Surgical face mask
Plastic aprom
Gloves
Handwashing after examination
What do seasnonal influnzae vaccines contain?
2 type A and 1 type B subtype viruses
Contraindicated in those with egg allergy
Why should healthcare workers get a vaccination?
Protect themselves + family
Reduce risk to at risk patients
Reduce absence from work
What is a zoonoses?
An infection that can pass between living animcals and humans, with the source being the animal
Note, malaria etc are not zoonoses as depend on human host for part of lifecycle
What is anthroponosis?
Infections from humans to animals
What are some common bacterial zoonoses>
Salmonella Campylobacter Shigella Anthraz Brucella Plague
What are some common viral zoonoses?
Rabies Avian influnza Ebola virus Lassa fever Rift valley fever Yellow fever/west nile fever
What are some parasitc zoonoses?
Toxoplasmosis (Common in the UK) Cysticercosis Echinococcosis Trichinellosis Visceral Larva Migrans (Toxocara)
What are some fungal zoonsoses?
Dermatophytoses
Sporotrichosis
How is rabies transmitted?
From the bite of an infected animal
What is the life cycle of rabies?
Incubation period of 2 weeks in humans Travels to brain via periperal nerves Causes acute encephalitis Progresses to mania, lethargy and coma Overproduction of saliva + tears Unable to swallow and hydrophobia Death by respiratory failure
How do you treat rabies?
Immediate post-exposure prophylaxis
Human rabies immunoglobulin
+ 4 doses of rabies vaccines over 14 days
Fatal if untreated
what is brucellosis?
Was an occupational hazard of animal workers
Due to an organism excreted in milk, placenta and aboreted foetus
How are humans infected with brucellosis?
Milking infected animals
During parturition
Handling carcasses of infected animals
Consumption of unpasteurised dairy products
How does brucellosis present?
Incubation of 5-30 days (up to 6 mongths)
Split into acute, subacute, chronic and subclinical presentations
What is the acute presentation of brucellosis?
1-3 weeks of: High fever Weakness + headaches Drenching sweats Splenomegaly
What is the subacute presentation of brucellosis?
A month or more of fever and joint pains
What are the chronic presentations of brucellosis?
Lasting months to years Flu like symptoms. Depression Maliase Chronic arthritis Endocarditis Rarely - meningism Splenomegaly
What is subclinical brucellosis?
50% have positive serology
How do you treat brucellosis?
Long acting doxycycline for 2-3 months + rifampicin or IM gentamicin for first week
If chronic difficult to treat
If CNS add cotrimoxazole for 2 weeks
What is the most common form of leptospirosis?
L. hardjo (from cattle)
How does leptopriosis present?
Fever, menigism
No Jaundice
What is leptospirosis?
Highly mobile spirochaetesSurvives environment for weeks-months
How do you treat leptospirosis?
Penicillin as early as possible
Prompt dialsysis
Mechanical ventilation
What organisms cause lyme disease?
Borrelia burgdorferi
Spirochaete found in wild deer
How is lyme disease spread to humans?
Via ticks
What is ereythema migrans?
A rash occuring in 80-90% of lyme disease cases
Appears 7-30 days after bite
Can have single or multiple lesions
What is acrodermatitis chronica atroficans ACA? (caused by lyme disease)
Extensor surfaces of distal extremities turn bluish/reddish
Progresses to atrophic disease
Peripheral neuropathy common
Common in elderly
What is lymphocytoma? (caused by lyme disease)
Bluish, solitary + painless nodules
Often in earlobe or areola
More common in children
What is neuroborreliosis? (caused by lyme)
Triad of facial nerve palsy,
radicular pain (migratory and worse at night)
lymphocytoic meningitis
How do you diagnose lyme disease?
Clinical diagnosis
-Single or multiple lesions with red area that then spread
ACA + lymphocytoma, clinical and high serology titres
Arthritis
How do you treat lyme disease?
Oral doxycyline or ammoxicillin, or IV ceftriaxone
Treat for 21 days
Unless arthritis or ACA, then 28 days
What is the main source of toxoplasmosis?
Toxoplasma gondii (found commonly in cats)
How is toxoplasmosis transmitted to humans?
From oocysts in cat faeces
From trophozoites in under-cooked meats
How does tocoplasmosis infection present?
Can be asymptomatic Acute: Pneumonia, fever, cough, rash Chronic: Lymphadenopathy Lymphocytosis Atypical mononuclear cells on blood film
Can present with chorio-retiniits + uveitis Ocasionally congenital (calcification in brain on x-ray. Often fatal)
How is toxoplasmosis treated?
Most don’t require treatment
Sulponamide + pyrimethamine
Ocasionally tetracycline
How is toxoplasmosis treated?
Most don’t require treatment
Sulponamide + pyrimethamine
Ocasionally tetracycline
What are the main three fungal pathogens?
Aspergillus species (fumigatus)
Candida sp. (albicans)
Crytptococcus sp. (neoformans)
Who do fungal infections affect?
As they are oportunistic:
Impaired immune systems (AIDS, malignancies/transplants, primary immunodeficiencies etc)
Chronic lung diseases like asthma/CF
ICU setting
What is the most common type of candida sp. infection
Mucocutaneous candidiasis
i.e nappy rash, thrush
Where do candida infections occur?
Commensal, so on skin
Attracted to moist areas
Often when patient is on antibiotics, steroids (or immuno depressed)
Neonates often affected
What is the pathology of invasive candidiasis?
A comensal gut flora, mostly endogenous origin of infection (going to sterile area)
4th most common blood stream infection, with same clinical presentation as bacterial BSIs
up to 40% mortality
What are the risk factors for invasive candidiasis?
Broad-spectrum antibiotics
IV catheters
Total parenteral nutrition
How is Aspergillosis transmitted between people?
Sproulation - inhaled spores
An intact immune system will have no problem
What are the classifications of pulmonary Aspergiullus disease?
Acute invasive
Chronic (> 3months)
Allergic
What are the predispositions for Acute invasive Aspergillus pulmonary disease?
Neutropnenic patients
Phagocyte defects
What are the predispositions for chronic Aspergillus pulmonary disease?
Patients with underlying chronic lung conditions
What are the predispositions for Allergic Aspergillus pulmonary disease?
Common in CF/asthma
Extrinsic allergic alveolitis
More common in fungal sensitisation
What are the symptoms of Acute invasive pulmonary aspergilliosis?
Rapid + extesive hyphal growth
Thrombosis + haemorrhage
Non-spefici signs
Persistent febrile neutropenia (despite antibiotics)
What is pulmonary aspergillioma?
Fungal mass growing in lung cavities
More common in: TB, Sarcoidosis, cronchiectasis + after pulmonary infections
Where are cryptococcal species found?
Bark of trees
Bird faeces
Organic matter
Which cryyptococcal disease is associated with HIB/AIDS?
Cryptococcal meningoencephalitis
How do you diagnose Cryptococcal meningoencephalitis?
Indian-ink CSF
What are the classes of antifungal drugs?
Polenes
Azoles
Echinocandins
What are the most common Polyene antifungal drugs?
Amphotericin B
Grisofulvin
Nystatin
What are the most common Azole antifungal drugs?
Fluconazole
Voriconaxole
Posaconazole
What are the most common Echinocandin antifungal drugs?
Anidulafungin
Caspofungin
Micafungin
How is invasive aspergilliosis
IV or oral Azole
IV amphotericine B(if serious)
How is invasive candidiasis treated?
Echocandins IV
Fluconazole IV/oral
How is crytptococcal meningitis treated?
IV amphotericine B + flyctosine
Followed by fluconazole
