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PM Infectious Disease > Bacteria and Protozoa > Flashcards

Bacteria and Protozoa Flashcards

1
Q

What causes amoebiasis and how is it transmitted?

A
  • entamoeba histolytica protozoa

- faeco-oral

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2
Q

Symptoms of amoebiasis:

A
  • mild diarrhoea or severe amoebic dysentery
  • liver and colonic abscesses
  • bloody diarrhoea
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3
Q

Investigations of amoebiasis:

A
  • stool microscopy - trophozoites (15 min/hot stool)

- amobie liver abscess - anchovy sauce, single mass right lobe, positive serology

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4
Q

Most common organism in animal bites:

A

pasteurella multocida

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5
Q

Most common organisms in human bites:

A
  • streptococci spp
  • staph aureus
  • eikenella
  • fusobacterium
  • prevotella
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6
Q

What type of organism causes anthrax and how is it transmitted?

A
  • bacillus anthracis
  • gram positive rod
  • infected carcasses
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7
Q

What is anthrax also known as?

A

Woolsorter’s disease

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8
Q

Features of anthrax:

A
  • painless black eschar
  • non-tender
  • marked oedema
  • GI bleeding
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9
Q

How does aspergilloma come about and how does it present?

A
  • mycetoma colonises existing lung cavity secondary to TB, cancer, CF
  • usually asymptomatic
  • cough, haemoptysis
  • may have crescent sign on CXR
  • high titres Aspergillus Precipitins
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10
Q

What causes botulism and what part causes the symptoms?

A
  • gram positive anaerobe clostridium botulinum

- neurotoxin irreversibly blocks Ach release and affects bulbar muscles and ANS

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11
Q

Features of botulism:

A
  • fully conscious, no sensory disturbance
  • flaccid paralysis
  • diplopia
  • ataxia
  • bulbar palsy
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12
Q

What causes campylobacter, transmission and incubation:

A
  • most common bacterial cause infectious intestinal disease
  • gram negative campylobacter jejuni
  • faeco-oral
  • incubation period: 1-6 days
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13
Q

Features of campylobacter:

A
  • headache, malaise
  • diarrhoea often bloody
  • abdominal pain may mimic appendicits
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14
Q

Complications of campylobacter:

A
  • Guillain-Barre syndrome
  • Reiter’s syndrome
  • septicaemia, endocarditis, arthritis
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15
Q

Which organism causes cat scratch disease?

A

gram negative rod: Bartonella Henselae

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16
Q

Which organisms most commonly cause cellulitis?

A
  • streptococcus pyogenes

- staphylococcus aureus

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17
Q

Who should receive IV Abx for cellulitis?

A
  • Eron III or IV
  • severe or rapidly deteriorating
  • <1yo or frail
  • immunocompromised
  • significant lymphoedema
  • facial cellulitis or periorbital cellulitis
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18
Q

Class I Eron classification:

A

no systemic toxicity and no uncontrolled co-morbidities

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19
Q

Class II Eron classification:

A

-systemically unwell
or
-systemically well with co-morbidity

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20
Q

Class III Eron classification:

A 
-significant systemic upset
or
-unstable co-morbidities
or
-life-threatening infection
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21
Q

Class IV Eron classification:

A

-sepsis syndrome
or
-severe life-threatening infection e.g. necrotising fasciitis

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22
Q

What organism causes cholera?

A
  • vibro cholerae

- gram negative

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23
Q

What symptoms does cholera cause?

A
  • profuse rice water diarrhoea
  • dehydration
  • hypoglycaemia
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24
Q

What causes cryptosporidiosis?

A
  • commonest protozoal causes of diarrhoea
  • cryptosporidium hominis and parvum
  • more common in immunocompromised patients and young children
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25
Q

Features of cryptosporidiosis:

A
  • watery diarrhoea
  • abdominal cramps
  • fever
  • immunocompromised: entire GI tract e.g. sclerosing cholangitis and pancreatitis
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26
Q

Diagnosis of cryptosporidiosis:

A
  • stool: modified Ziehl Neelsen stain

- red cysts

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27
Q

What causes diphtheria:

A
  • gram positive Corynebacterium diphtheriae
  • necrotic mucosal cells on tonsils create diphtheric membrane - systemic distribution may cause necrosis of myocardial, neural and renal tissue
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28
Q

Common presentation of diphtheria:

A
  • Eastern Europe/Russia/Asia
  • sore throat - diphtheric membrane - very pseudomembrane on posterior pharyngeal wall
  • bulky cervical lymphadenopathy
  • neuritis e.g. cranial nerves
  • heart block
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29
Q

Investigation of diphtheria:

A

culture of throat swab: tellurite agar or Loeffler’e media

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30
Q

What causes enteric fever and how does it spread?

A
  • Salmonella type and paratyphi

- faeco-oral route

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31
Q

Features of enteric fever:

A
  • initially systemic upset
  • abdominal pain and distension
  • constipation more common in typhoid than diarrhoea
  • rose spots on trunk (more in paratyphoid)
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32
Q

Complications of enteric fever:

A
  • osteomyelitis (esp sickle cell)
  • GI bleed/perforation
  • meningitis
  • cholecystitis
  • chronic carriage
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33
Q

What causes e.coli?

A
  • facultative, anaerobic, lactose fermenting gram negative rod
  • diarrhoea, UTIs, neonatal meningitis
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34
Q

O157:H7

A
  • severe, haemorrhage, watery diarrhoea
  • high mortality
  • complicated by HUS - increased urea
  • contaminated ground beef
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35
Q

Which organism most commonly causes travellers’ diarrhoea?

A

e. coli

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36
Q

Which organisms are the most common causes of acute food poisoning?

A
  • staph aureus
  • bacillus cereus
  • clostridium perfringens
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37
Q

Which gastroenteritis organism causes non-bloody stools?

A
  • e. coli
  • giardiasis
  • cholera
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38
Q

Which gastroenteritis organisms causes bloody stools?

A
  • shigella
  • campylobacter may cause blood diarrhoea
  • amoebiasis
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39
Q

Gastroenteritis incubation period 1-6 hours:

A
  • staph aureus

- bacillus cereus

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40
Q

Gastroenteritis incubation period 12-48 hours:

A
  • salmonella

- e.coli

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41
Q

Gastroenteritis incubation period 48-72 hours:

A
  • shigella

- campylobacter

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42
Q

Gastroenteritis incubation period > 7 days:

A
  • giardiasis

- amoebiasis

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43
Q

Which organism causes giardiasis?

A
  • flagellate protozoan Giardia Lamblia

- faeco-oral

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44
Q

Features of giardiasis?

A
  • often asymptomatic
  • lethargy, bloating, abdominal pain
  • flatulence
  • non-bloody diarrhoea
  • chronic diarrhoea, malabsorption, lactose intolerance
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45
Q

Investigations for giardiasis?

A
  • trophozite stool microscopy and cysts classically negative

- duodenal fluid aspirates or string tests

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46
Q

Risk factors for invasive aspergillosis:

A
  • HIV
  • leukaemia
  • following broad spectrum Abx
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47
Q

Diagnosis of legionella:

A

urinary antigen

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48
Q

What causes leishmaniasis generally?

A

intracellular protozoa Leishmania spread by sand flies

49
Q

What causes cutaneous Leishmaniasis and what are the features?

A
  • Leishmania tropica/mexicana
  • crusted lesion at site of bite
  • South/Central America - risk of mucocutaneous so treat
  • Africa/India conservative treatment
50
Q

What causes mucocutaneous Leishmaniasis and features:

A
  • Leishmania braziliensis

- skin lesions may spread to involve mucosal of nose, pharynx etc.

51
Q

What causes visceral leishmaniasis and features:

A
  • Leishmania donovani
  • Mediterranean, Asia, South America, Africa
  • fever, sweats, rigors
  • massive splenomegaly, hepatomegaly
  • poor appetite, weight loss
  • grey skin
  • pancytopenia secondary to hypersplenism
  • gold standard for diagnosis is bone marrow or splenic aspirate
52
Q

What is Lemierre’s syndrome and which bacteria most commonly causes it?

A
  • infectious thrombophlebitis of internal jugular vein
  • secondary to bacterial sore throat by fusobacterium necrophorum - peritonsillar abscess
  • may have septic pulmonary emboli
53
Q

What is leprosy caused by?

A

mycobacterium leprae

54
Q

Features of leprosy:

A
  • patches of hypopigmented skin, typically buttocks, face and extensor surfaces
  • sensory loss
  • low degree cell mediated immunity - lepromatous (multibacillary) - extensive skin, symmetrical nerve
  • high degree cell mediated immunity - tuberculoid (paucibacillary) - limited skin, asymmetric nerve involvement, hair loss
55
Q

What is leptospirosis cause by and how is it spread?

A
  • spirochaete leptospirosis interrogans
  • contact with infected rat urine
  • consider Weil’s disease in high risk patients with hepatorenal failure
56
Q

Features of leptospirosis:

A 
early phase - bacteraemia
-mild/subclinical
-fever, flu like
-subconjunctival suffusion/haemorrhage + bilateral conjunctivitis 
second immune phase - may lead to weil's
-AKI
-hepatitis
-aseptic meningitis
57
Q

What is Lyme Disease caused by?

A

spirochaete Borrelia Burgdorferi spread by ticks

58
Q

Later features of lyme disease:

A
  • > 30 days
  • CVS: heart block, pericarditis, myocarditis
  • neuro: facial nerve palsy, radicular pain, meningitis
  • polyarthritis
59
Q

Investigations for Lyme disease:

A
  • erythema migrans - start abx
  • ELISA ab to Borrelia first line
  • nothing if asymptomatic
60
Q

What causes malaria:

A
  • plasmodium protozoa - female anopheles mosquito
  • plasmodium falciparum most common
  • vivax, ovale and malariae - benign
61
Q

What is protective against malaria:

A
  • G6PD deficiency
  • HLA B53
  • absence Duffy antigens
62
Q

What symptom is characteristic of malaria?

A

fever on alternating days

  • vivale/ovale: every 48 hours
  • malariae: every 72 hours associated with nephrotic syndrome
63
Q

Features of plasmodium falciparum malaria:

A
  • shizonts on blood film
  • parasitaemia
  • hypoglycaemia
  • acidosis
  • fever
  • severe anaemia
  • complications: cerebral malaria, acute renal failure, ARDS, hypoglycaemia, DIC
64
Q

How do you treat severe falciparum malaria?

A

IV artesunate

65
Q

Where is plasmodium vivax most common?

A

central America, Indian subcontinent

66
Q

Where is plasmodium ovale most common?

A

Africa

67
Q

Antimalarials in pregnancy:

A
  • chloroquine
  • proguanil: folate supplementation
  • doxycycline contraindicated
68
Q

Children prophylaxis malaria:

A
  • DEET for over 2 mo

- doxycyline for children >12yo

69
Q

Which malarial drugs are contraindicated in epilepsy?

A

chloroquine and mefloquine

70
Q

Doxycycline ADR:

A

photosensitivity, oesophagitis

71
Q

Organisms causing meningitis in 0-3mo:

A
  • group B strep
  • e. coli
  • listeria monocytogenes
72
Q

Organisms causing meningitis in 3mo-6yo:

A
  • neisseria meningitidis
  • strep pneumoniae
  • haemophilus influenzae
73
Q

Organisms causing meningitis in 6yo-60yo:

A
  • neisseria meningitidis

- strep pneumoniae

74
Q

Organisms causing meningitis in >60yo:

A
  • strep pneumoniae
  • neisseria meningitidis
  • listeria monocytogenes
75
Q

Organisms causing meningitis in immunocompromised:

A

-listeria monocytogenes

76
Q

CSF appearance in bacterial meningitis:

A
  • cloudy
  • low glucose <1/2
  • high protein >1g/L
  • 10-5000 WC polymorphs/mm3
77
Q

CSF appearance in viral meningitis:

A
  • clear/cloudy
  • 60-80% of plasma glucose
  • normal/raised protein
  • 15-1000 WC lymphocytes/mm3
78
Q

CSF appearance in tuberculous meningitis:

A
  • slightly cloudy, fibrin web
  • low glucose <1/2
  • high protein >1g/L
  • 30-300 lymphocytes/mm3
79
Q

CSF appearance in fungal meningitis:

A
  • cloudy
  • low glucose
  • high proteins
  • > 20-200 lymphocytes/mm3
80
Q

Differences with viral meningitis:

A
  • more benign and common
  • self limiting 7-14 days
  • opening pressure 10-20cm3 (normal)
  • most common non-polio enteroviruses: Coxsackie
81
Q

Who gets screened for MRSA?

A
  • all awaiting elective admissions
  • all emergency admissions
  • nasal swab (inside rim 5 sec) and skin lesions or wounds
82
Q

Management of MRSA:

A
  • nose: mupicorin tds 5 days
  • skin: chlorhexidine glauconite od 5 days (axilla, groin, perineum)
  • Abx: vancomycin, teicoplanin, linezolid
83
Q

What may mycoplasma pneumonia not respond to?

A
  • penicillins or cephalosporins

- lack of pepitdoglycan cell wall

84
Q

Complications of mycoplasma pneumonia:

A
  • cold agglutinins: haemolytic anaemia, thrombocytopenia
  • erythema multiform, erythema nodosum
  • meningoencephalitis, Guillain Barre
  • bullous myringitis: painful vesicles on tympanic membrane
  • pericarditis, myocarditis
  • hepatitis, pancreatitis
  • acute GN
85
Q

Investigations for mycoplasma pneumonia:

A
  • mycoplamsa serology

- positive cold agglutination test

86
Q

Type I necrotising fasciitis:

A
  • mixed aerobes and anaerobes
  • often post surgery in diabetics
  • most common
87
Q

Type II necrotising fasciitis:

A

streptococcus pyogenes

88
Q

Management of necrotising fasciitis:

A
  • urgent surgical referral for debridement

- IV Abx

89
Q

What type of organism is pseudomonas aeruginosa and what does it cause:

A
  • aerobic gram negative, non lactose fermenting, oxidase positive
  • chest infections (especially CF)
  • skin: burns, wound infections, hot tube folliculitis
  • otitis externa (especially in diabetes)
  • UTI
90
Q

What causes schistosomiasis?

A

bilharzia, parasitic flatworm infecting (3 species)

91
Q

Shistosoma haematobium:

A
  • egg clusters (pseudopapillomas) in bladder
  • calcification on x-ray
  • obstructive uropathy and kidney damage
  • swimmer’s itch
  • risk factor for squamous cell bladder cancer
  • management: single oral dose praziquantel
92
Q

Shistosoma mansoni and japonicum:

A
  • mature in liver and go through portal system to distal colon
  • progressive hepatomegaly and splenomegaly
  • cirrhosis, variceal disease, cor pulmonale
93
Q

Shistosoma intercalatum and mekongi:

A
  • less prevalent

- intestinal schistosomiasis

94
Q

How does a spinal epidural abscess come about and what is the most common organism:

A
  • bacteria enters epidural space by contiguous spread (e.g. discitis), or haematogenous spread
  • mostly staph aureus
95
Q

How does staphylococcal toxic shock syndrome come about and what are the common features:

A
  • TSST1 superantigen
  • related to infected tampons
  • fever, hypotension
  • diffuse erythematous rash
  • desquamation of rash esp of palms and soles
  • CNS involvement, hepatitis, thrombocytopenia, renal failure, mucous membrane erythema
96
Q

What is strongyloides stercoralis caused by and what are the features:

A
  • human parasitic nematode worm
  • larvae in soil and penetrate skin
  • diarrhoea, abdominal pain and bloating, papulovesicular lesions where skin penetrate, larva currens, travels to lungs to cause pneumonitis like Loeffler’s
97
Q

Features of tetanus infection:

A
  • prodrome fever, lethargy, headache
  • trismus (lockjaw)
  • risus sardonicus
  • opisthotonus
  • spasms
98
Q

What causes toxoplasmosis?

A
  • toxoplasma gondii - obligate intracellular protozoa that infects via GI, lung or broken skin
  • oocytes release trophozoites which migrate around body
  • usually cats or rats
99
Q

What does toxoplasmosis cause in immunocompetent:

A
  • asymptomatic
  • self-limiting
  • resembles infectious mononucleosis
  • less commonly meningoencephalitis and myocarditis
  • no treatment unless severe or immunocompromised
100
Q

What are the features of congenital toxoplasmosis?

A
  • transplacental spread from mother
  • neurological damage: cerebral calcification, hydrocephalus, chorioretinitis
  • opthalmic damage: retinopathy, cataracts
101
Q

Trypanosoma Rhodesiense:

A
  • African trypanosomiasis - sleeping sickness (East Africa)
  • tsetse fly
  • chancre - painless subcutaneous nodule at site of infection
  • intermitten fever
  • posterior cervical lymphadenopathy
  • later: CNS involvement (IV melarsoprol)
102
Q

American Trypanosomiasis:

A
  • protozoan Trypanosoma cruzi
  • 95% asymptomatic in acute phase - chagoma
  • chronic Chagas’ disease affects heart (myocarditis - cardiomyopathy and arrhythmias) and GI (megaoesophagus and megacolon)
103
Q

MOA of mycobacterium tuberculosis:

A
  • macrophages migrate to regional lymph nodes and lung lesion - Ghon complex
  • granuloma - epithelioid histiocytes
  • caseous necrosis in centre
  • type IV hypersensitivity reaction
104
Q

Screening of tuberculosis:

A
  • waxy membrane prevents binding of normal stains
  • Ziehl Neelsen stain
  • screening: Mantoux test, interferon gamma blood test if mantoux test positive
105
Q

How is a Mantoux test carried out and results interpreted:

A

-0.1ml of 1:1000 PPD injected intradermally
-results 2-3 days later
<6mm - negative (give BCG if unvaccinated)
6-15mm - positive (no BCG, previous TB infection or BCG)
>15mm - strongly positive (suggests TB infection)

106
Q

What might cause a false negative Mantoux test?

A
  • miliary TB
  • sarcoidosis
  • HIV
  • lymphoma
  • very young age
  • steroids
  • fever
  • hypoalbuminaemia
  • anaemia
107
Q

Diagnosis of TB:

A
  • CXR: upper lobe cavitation, bilateral hilar lymphadenopathy
  • sputum smears (Ziehl Neelsen)
  • Sputum culture (more sensitive but slower)
  • NAAT (rapid diagnosis, more sensitive than smear but less than culture)
108
Q

How to treat latent TB:

A

-3m isoniazid (with pyridoxine) and rifampicin
-6m isoniazid (with pyridoxine)
consider interaction with rifampicin

109
Q

Primary TB:

A
  • non-immune hoest develops primary infection of lungs
  • lesion - Ghon complex
  • immunocompetent - initial lesion heals by firosis
  • disseminated disease - miliary tuberculosis travels through pulmonary venous system
110
Q

Secondary TB:

A
  • if host becomes immunocompromised, initial infection reactivated
  • in apex of lungs and may spread
  • extra pulmonary: CNS, vertebral bodies (Pott’s), cervical lymph nodes (scrofuloderma), renal, GI tract
111
Q

Management of active TB in first 2 months (acute phase):

A
  • rifampicin
  • isoniazid
  • pyrazinamide
  • ethambutol
112
Q

Management of TB in continuation phase (next 4 month):

A
  • rifampicin

- isoniazid

113
Q

How do you treat meningeal tuberculosis?

A

12 months min with steroids

114
Q

Rifampicin ADR:

A
  • potent liver enzyme inducer
  • hepatitis
  • orange secretions
  • flu-like
115
Q

Isoniazid ADR:

A
  • peripheral neuropathy (prevent with pyridoxine vit B6)
  • hepatitis
  • agranulocytosis
  • liver enzyme enzyme inhibitor
116
Q

Pyrazinamide ADR:

A
  • hyperuricaemia causing gout
  • arthralgia
  • myalgia
  • hepatitis
117
Q

Ethambutol ADR:

A

optic neuritis

118
Q

Most common surgical site infection:

A

staph aureus

119
Q

Most common organisms causing post splenectomy sepsis:

A
  • haemophilus influenza
  • strep pneumoniae
  • meningococci

PM Infectious Disease (6 decks)

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