Flashcards in Infectious Disease 2 Deck (138):
What is the most common causative organism of malaria? What are the other 3? New one?
Plasmodium falciparum most common
Plasmodium knowlesi is the new one
Typical incubation period of falciparum malaria? What about vivax/ovale?
Up to a month for falciparum, 6 months for vivax/ovale
Which two organisms might be implicated in a malaria 'relapse' ages after initial presentation?
Vivax and ovale
Malaria parasite associated with long incubation period and nephrotic syndrome?
When are the carriers of malaria parasites most active?
Typical fever pattern for falciparum malaria?
Quotidian - daily
Can be irregular, tertian (every 3rd day) or subtertian (36 hour cycles)
Common symptoms of malaria?
Fever - swinging, recurrent
Chills and rigors
Nausea, vomiting, diarrhoea
Signs of malaria?
What sorts of things indicate severe malaria infection?
Reducing consciousness, fits
Bleeding or shock
Renal failure, nephrotic syndrome
Major differentials for fever in returning traveller?
Diagnostic investigations for malaria?
Blood films - thick (presence) and thin (type)
Nucleic acid based testing
ABCD of malaria prophylaxis?
Awareness of risk - destination, travel advice, high risk categories
Bite avoidance - mosquito nets, keeping inside/covered dusk-dawn
Chemoprophylaxis - chloroquine, mefloquine, malarone, doxycycline
Diagnosis - and prompt treatment
What Chemoprophylaxis is used for low-risk malaria areas? Common side effects?
What chemoprophylaxis is used for high risk malaria areas e.g. Subsaharan Africa? Side effects?
Psychosis, convulsions, coma
What should be suspected in a systemically unwell woman with no obvious source of infection but offensive vaginal discharge?
?retained tampon - staphylococcal toxic shock syndrome
How is typhoid spread?
Fecal-oral incl food (shellfish), water
RFs for typhoid fever?
Foreign travel to risk areas - Asia, Africa, S America
H2RBs, PPIs, antacids, GI pathology
Immunosuppression, extremes of age
How long is the incubation period for typhoid?
Similar to malaria - 1-3 weeks, nearly always within 1 month
Over how long does untreated typhoid manifest?
4 weeks, where 3 is the worst and 4 is start of recovery
Classical key Sx of typhoid?
Gradually worsening persistent fever, evening exacerbation
GI - abdo pain (RIF), distension, hepatosplenomegaly
Rash (rose spots on abdomen, chest)
Investigations for typhoid?
Blood cultures, marrow cultures
Serology for H and O antigens (Widals test)
Is there a vaccine for typhoid?
What is the spectrum of illness with Dengue fever?
Dengue fever -> dengue haemorrhagic fever -> dengue shock syndrome
Virus and vector for dengue fever?
Flavivirus spread by Aedes mosquito
Incubation period of dengue?
2-7 days, typically around 3
Key Sx of dengue?
Abrupt onset high fever
Generalised macular rash
Haemolytic tendencies incl epistaxis
Features of dengue haemorrhagic fever?
Capillary permeability abnormalities - low protein, oedema, pleural effusions etc.
Diagnosis of dengue? What else should be done?
Serum IgM, IgG
Should also do malaria films
Organism and spread of Lyme disease?
Deer tick bites spreading borrelia burgdorferi
Early symptoms of Lyme disease?
Erythema migrans - target lesion >5cm occurring at site of tick attachment, usually within 1m of bite
Plus or minus non-specific illness
Symptoms of disseminated Lyme disease?
Flu like illness
Facial nerve palsies, meningoencephalitis
Lymphocytomas on earlobe/nipples (blue-red swellings)
Late manifestations of Lyme disease?
Arthralgias - typically recurrent, of large joints like knee
Acrodermatitis chronica atrophicans (blue red discolouration of extensor surfaces) alongside swelling and peripheral neuropathies
4 differentials for erythema migrans?
Bug bite reaction
Pathophysiology of infective endocarditis?
Background of Nonbacterial thrombotic endocarditis (platelet-fibrin vegetation) which gets infected
RFs for IE?
Replacement heart valves, catheters, prostheses, haemodialysis
Structural heart abnormalities e.g. VSD, PDA
Recent dental work
Pre-existing valvular disease e.g. Hx of rheumatic fever
Hx of IE
Why do bacterial vegetations not get destroyed in IE/ why is there no substantial neutrophilia?
Valves are poorly vascularised - only platelets do first line attacking
Microemboli trigger RES (humoral arm) in spleen so AgAb complexes start getting formed, causing Sx
3 most common pathogens behind IE?
Strep viridans (a haemolytic)
Coagulase negative staph
What pathogen is most implicated in IVDU or healthcare associated IE?(acute presentation)
What bacteria is most implicated in native valve endocarditis/late prosthetic endocarditis? (Subacute)
Strep viridans (a haemolytic)
What bacteria have the biggest role in new prosthetic valve endocarditis?
Coagulase negative staph
Rarer bacterial causes of IE?
Enterococci and gram negatives
Symptoms of acute/fulminant IE?
Acute heart failure
Common Sx of subacute IE?
Fever, night sweats (PUO)
What does spiking PUO and conduction abnormalities with a heart murmur suggest?
Aortic root abscess secondary to IE
4 areas of signs of IE?
Systemic signs of IE?
Petechial haemorrhages in conjunctiva, palate, buccal
Oslers nodes, janeway lesions
Cardiac signs of IE?
New or changing murmur
Embolic signs of IE?
Stroke, PE, peripheral infarcts, MI, DVT etc.
Immune vasculitis consequences of IE?
Immune complex nephritis -> haematuria, microalbuminuria
What does neutrophilia in the context of IE suggest?
What is diagnostic of IE?
At least 3 sets of blood cultures, taken during temp spikes
Imaging for IE?
Echo - Transoesophageal if poss
What are the general principles behind IE treatment?
High dose, long term (4-6 week) Abx treatment based on culture sensitivities particularly if subacute
Combo synergistic therapy
E.g. Vanc and gent (covers S aureus) or Amox and gent for viridans
When might surgical involvement be required for IE?
If in prosthetic valves (biofilm covered)
Large or persistent vegetations
SIGHT management of suspected C Diff?
Suspected case of infectious diarrhoea, Abx history, no better cause
Isolate and investigate
Gloves and aprons (PPE)
Hand washing with soap and water
What is C Diff?
Gram negative bacillus in many people which typically only causes trouble when normal gut flora wiped out e.g. By Abx treatment.
Can cause a pseudomembranous colitis (acute, exudative) via toxins A and B
How is c diff transmitted and how does it remain in the environment?
Transmitted fecal-orally, can form spores in the environment and stay there for ages
Drugs associated with c diff? (1 non-Abx)
Generally what sorts of antibiotics are associated with c diff infection?
IV, broad spectrum Abx
Symptoms of c diff colitis?
Diarrhoea starting 5-10 days after commencing Abx (varying severity)
Fever, rigors, malaise
Colicky abdo pain
Outline testing process for c diff?
Do stool testing - Glutamate dehydrogenase (GDH) positive = presence of C diff but not necessarily infection, toxins A/B positive = causing infection
What should you do if a patient is positive for GDH but negative for toxins and still has diarrhoea?
Isolate anyway and retest for c diff
2 patients, 1 with C diff 1 with MRSA. Which do you isolate first and why?
C diff, because it can form environmental spores which can be really hard to get rid of
Besides SIGHT, management of c diff?
Stop offending Abx, consider changing to vanc or metronidazole
Conservative - fluids etc.
Major complications of C diff infection?
Fulminant colitis, toxic megacolon, peroration
Dehydration, shock, AKI etc.
Common Sx of HA-MRSA?
Can appear as boil/pustule, abscess particularly around wound sites
Fever, rigors, generally unwell
Potential Sx of CA-MRSA infection?
Can cause severe cellulitis
What type of bacteria is mycobacterium tuberculosis?
Acid fast bacillus
What is the primary TB infection?
Spread by droplets, M TB gets engulfed in the lungs by macrophages and transported to hilar LNs -> granulomas around the body
What may happen at the point of a primary TB infection?
May become symptomatic initially -> overt/active TB, miliary
May eliminate all the bacteria
May lay dormant in granulomas -> secondary infection of LTBI
RFs for TB?
Being born in endemic area, big cities etc.
Social deprivation factors - homeless, alcohol, IVDU
HIV and other Immunocompromise
Elderly and children
Constitutional and pulmonary symptoms of reactivated LTBI?
Fever, weight loss, night sweats TATT, anaemia
Cough, productive +/- bloodstained
Lobar collapse, bronchiectasis, pleural effusion etc.
Second most common TB presentation (extra-pulmonary)?
Sterile pyuria - kidney lesions, abscesses, salpingitis, infertility, epididymitis
MSK presentations of TB?
Potts vertebrae (collapse)
CNS presentations of TB?
What CXR picture does primary TB infection give?
Central apical portion, left lower lobe infiltrate
+/- pleural effusion
What CXR picture does reactivated TB show?
Apical lesions (granulomas) - cavitating lesions
No pleural effusions
What CXR does miliary TB show?
All over the shop (millet seed)
How is TB investigated microbiologically?
Early morning sputum samples - bronchoscopy, lavage and gastric washing if necessary
Cultures take 4-8 weeks for confirmation and a further 3-4 for sensitivities (apart from Rifampicin)
What histological investigation should be done for extra-pulmonary TB?
Biopsy of LNs and CXR
Screening tests for TB?
Tuberculin: Heaf test, Mantoux test (may be positive if had BCG)
IgG testing (IGRA)
Basic management of TB infection?
6 month 4 drug regime, dependant on sensitivities but generally Rifampicin isoniazid ethambutol pyrazinamide for 2m then Rifampicin and isoniazid for another 4
Alternatives to first line TB drugs?
Other macrolides, quinolones
What must be monitored during TB drug therapy?
LFTs as most can derange, renal impairment
Visual impairment (ethambutol)
Peripheral neuropathy (isoniazid)
In whom is disseminated MAC disease most common?
HIV with low cd4 count - AIDS
What does MAC infection cause in kids?
Cervical lymphadenitis - blue-purple discharging LN
What is lady Windermere syndrome?
Pneumonitis in elderly women traditionally who have suppressed their cough reflex, caused by MAC infection
What is hot tub lung?
MAC infection causing granulomatous pneumonitis related to inhaling aerosolised MAC in water, e.g. Poorly maintained hot tubs
What is an important factor, but not pre-requisite in MAC infection?
Immunocompromise e.g. HIV, elderly, CF
What is a Ghon complex?
Initial granuloma + infected lymph node in TB - may be on skin, in lungs
What is leprosy/hansens disease?
Infection with mycobacterium leprae causing nothing initially, then years later skin lesions (discolouration) alongside neuropathy, eye changes and respiratory Sx
Transmission of leprosy?
Droplet, normally close contact with infected
What is impetigo?
Honeycomb golden crusting due to epidermal infection often caused by s aureus
What is a furuncle?
Infection of whole hair follicle down to root causing micronecrosis
Caused by s aureus
What is folliculitis?
Pustule formation around hair follicle caused by s aureus
What is a carbuncle?
Infection of multiple hair follicles causing draining abscess formation
What is flucloxacillin effective against?
What is ludwigs angina?
Nec fasc of submandibular space
What is Fournier's gangrene?
Nec fasc of scrotum/vulva
Signs indicative of nec fasc rather than cellulitis?
Pain disproportionate to visible signs and systemic illness
Bullae or ecchymosis
Tender beyond poorly demarcated borders
What is osteomyelitis?
Infection of the bone marrow, which can spread to cortex and periosteum
Typically caused by s aureus incl MRSA
What is a sequestrum?
Area of dead bone detached from healthy bone seen in osteomyelitis, acting as focus for chronic infection
What is an involcrum?
Periosteum separated from underlying bone in osteomyelitis, acting as source for new bone growth
What is the likely origin of osteomyelitis in kids or those with in dwelling catheters?
Rx for osteomyelitis?
Flucloxacillin and Rifampicin for 4-6 weeks
But wait for culture results!
Gold standard diagnosis for osteomyelitis?
What enzyme distinguishes s aureus from other staph species?
What is STSS?
Streptococcal toxic shock syndrome - shock caused by s pyogenes toxin exotoxin release
What is TSS?
Toxic shock syndrome typically caused by staph aureus
What differentiates STSS from TSS?
TSS often arise as shock with fever in otherwise healthy individual, has characteristic sunburn rash which causes desquamation in couple of weeks
STSS however comes from site of pre-existing skin infection, looks a bit like nec fasc but doesn't include the sunburn rash
What is SSSS?
Staphylococcal Scalded Skin Syndrome; widespread fluid filled blisters, possibly widespread desquamation
Ritter's Disease of the newborn
3 structural pathogenicity factors of s aureus?
What exotoxin in s aureus (MRSA) is associated with high virulence, necrotising pneumonia and potentially neutropenia?
What criteria is used to define haemolytic streptococci?
What is GAS?
B haemolytic streptococci - strep pyogenes
What do B haemolytic streptococci do to blood?
Completely haemolyse it
What is acute rheumatic fever?
A complication of GAS infection; autoimmune attack on endocardium/synovial tissue (migrating polyarthropathy)
What disease does GAS in new mothers?
What causes puerperal fever?
What are 2 examples of alpha haemolytic streptococci? What do they do to blood?
Strep pneumoniae and strep viridans
Weakly oxidising so turn it green
What is the classic GBS?
Important disease caused by GBS?
Neonatal meningitis and pneumonia, also elderly meningitis
What can GBS bacteruria cause in a pregnant woman?
Stillbirth, prematurity, miscarriage
Are enterococci gram positive or negative? 2 most common species?
Enterococcus faecalis and faecium
Alternative name for enterococci?
Are enterococci aerobic or anaerobic?
What do enterococci intrinsically resist?
3 examples of coliform bacteria?
Faecal coliforms e.g. E. coli
3 examples of aminoglycosides?
3 examples of macrolides?
How do macrolides work?
Protein synthesis inhibitors
What type of bacteria are macrolides effective against?
Gram negatives e.g. Gonorrhoea
What are the general side effects of aminoglycosides?
How do vancomycin and teicoplanin work?
Inhibit cell wall synthesis via peptidoglycan formation
General trend working through the generations of cephalosporins?
Better action vs gram negatives
What are tetracyclines commonly used for?
Second line vs pneumonia (if penicillin allergy)
What is metronidazole effective against?
Gram negatives, fungi and protozoa