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Medd 422 > Enteric Pathogens > Flashcards

Enteric Pathogens Flashcards

1
Q

Clostridium difficile is a gram ___ bacillus

A

POSITIVE

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2
Q

Clostridium difficile - 3 types of toxins

A

Binary toxin
Toxin A
Toxin B* (cytotoxin)

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3
Q

Clostridium difficile dx

A

Test stool for toxin A/B by ELISA, PCR for gene (usually toxin B), culture

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4
Q

Clostridium difficile tx

A

Mild/moderate disease: Metronidazole (oral/IV)
Severe disease: Vancomycin 125mg PO QID (oral, not IV)
Alternatives: stool transplant, surgical (toxic megacolon)

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5
Q

Eschericia coli is a gram ____ bacillus

A

NEGATIVE

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6
Q

Bacteria that is most common cause of UTI

A

E. coli

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7
Q

5 different strains of E. Coli

A 
ETEC - Enterotoxigenic E. Coli 
EPEC - Enteropathogenic E.coli 
EIEC - Enteroinvasive E. coli
EAEC - Enteroaggregative E. coli
EHEC - Enterohemorrhagic E. coli
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8
Q

ETEC

A
  • Traveller’s diarrhea (fecal-oral)
  • Mild watery diarrhea and nausea
  • NO VOMITING
  • Usually lasts 1-4d
  • 10^8-10^10 bacteria needed to cause disease
  • Tx: Oral rehydration, dukoral available, can try empiric ABx +/- loperamide/Immodium (ie. Cipro or Azithromycin + immodium)
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9
Q

EHEC

A
  • AKA STEC (Shiga toxin producing E.Coli)
  • Includes E.Coli 0157:H7 (50%) and O104:H4 (50%)
  • (Bloody) diarrhea
  • Possible HUS (hemolytic anemia, AKI, thrombocytopenia)
  • Ingestion of cow fecal matter contaminated food/water
  • 10-100 organisms infective
  • Acts on enterocytes and endothelial cells
  • Tx: No antibiotics, supportive measures (ABX may cause bacteria to die and release more toxins)
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10
Q

2 types of salmonella

A
  1. Non-Typhoidal

2. Typhoidal

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11
Q

Salmonella is a gram _____ bacillus

A

NEGATIVE

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12
Q

2 most common non-typhoidal salmonella serotypes

A
  1. Enteritidis

2. Typhimurium

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13
Q

Non-typhoidal salmonella

A
  • self-resolving gastroenteritis
  • 10^3-10^5 organisms infective
  • Incubation:6-72h; resolves within 4-7d
  • Acute diarrhea, fever, abdo pain
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14
Q

Typhoidal salmonella

A

-typically invasive: fever, systemic symptoms (rash, headache), bacteremia
-Gastroenteritis (diarrhea and/or constipation)
-ONLY HUMANS (no animal reservoir; fecal-oral)
-can lead to intestinal perforation if left untreated
-asymptomatic carriage in gall bladder
Dx: Culture, molecular/PCR

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15
Q

Helicobacter pylori is a gram _____ bacillus

A

NEGATIVE

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16
Q

H pylori

A
  • Nausea, vomiting, epigastric pain, anorexia, acid reflux
  • Most common cause of gastritis
  • Most common chronic bacterial infection in humans
  • Fecal-oral, oral-oral
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17
Q

Non-typhoidal salmonella tx

A

No ABx required unless invasive disease or increased risk population

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18
Q

Typhoidal salmonella tx

A 
Ceftriazone or azithromycin (lots of resistance already to other Abx) 
Vaccine available (~50% effective)
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19
Q

Possible tests for H Pylori

A
  • Possible tests: urease breath test, serology (ELISA IgG), Endoscopy + biopsy
  • Test for eradication if needed = UBT ~4wks after tx
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20
Q

H Pylori tx

A

triple therapy for 2 weeks (PPI + 2 antibiotics = Lansoprazole + Clarithromycin + Amoxicillin)

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21
Q

Hep A

A
  • Fecal-oral
  • Mild, self-limiting
  • Fatigue, nausea, vomiting, diarrhea, abdo pain, fever
  • Severe: jaundice, pruritus, dark urine, pale stools
  • Extra-hepatic: cryoglobinemia, glomerulonephritis, arthritis, leukocytoclastic vasculitis
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22
Q

Hep A tx

A

Supportive, recovery in 2-3mths after infection

lifelong immunity

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23
Q

Hep A LFTs

A

ALT > AST

Transaminases >1000

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24
Q

Hep A vaccine

A

2 doses at least 6 mo apart

Can give as early as 6 mo

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25
Q

2 common bacteria involved in food poisoning:

A
  1. Staph aureus

2. Bacillus cereus

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26
Q

Food bacillus cereus is found a lot in

A

Rice

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27
Q

Food poisoning

A

Acute cause, vomiting, upper GI within 1-6h after ingestion

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28
Q

Food poisoning dx

A

clinical

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29
Q

Food poisoning tx

A

Resolves within 24h without tx

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30
Q

Clostridium botulinum is a gram _____ bacillus

A

positive, rod, anaerobe

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31
Q

MOA of Botulinum Toxin A

A

Binds to receptors on neuron cell surface –> heavy chain stays on receptor while light chain gets taken into cell and damages SNARE proteins –> released ACh vesicles can’t dock on post-synaptic muscle cell –> no ACh received by muscle cell

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32
Q

the 8 Ds of adult symptoms of Botulinum

A
  1. Droopy eyelids
  2. Double vision
  3. Dysphagia
  4. Dysarthria
  5. Dizziness
  6. Dry mouth
  7. Descending flaccid paralysis
  8. Diaphragm paralysis –> death
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33
Q

infant symptoms of Botulinum

A

Floppy baby syndrome = hypotonia/decreased muscle tone

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34
Q

Botulinum dx

A

Clinical presentation

Toxin detection in stool and serum

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35
Q

Botulinum tx

A

Anti-toxin (Ig)
Respiratory support if necessary
Mostly supportive

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36
Q

Abdominal abscess tx

A

(1) Empiric ABx if septic: Piperacillin-Tazobactam OR Ceftriaxone PLUS Metronidazole
(2) Surgical drainage plus culture
(3) Directed ABx based on culture results + anaerobic coverage (continue Metronidazole)

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37
Q

Normal gut flora

A
  • Gram -ve coliforms: E. Coli, Proteus, Klebsiella, Enterobacter = facultative anaerobes
  • Anaerobes: Bacteroides (-), clostridium (+), fusobacterium (-), peptostreptococcus (+)
  • Gram +ve facultative anaerobes: streptococcus, enterococcus
  • Staph aureus
  • Candida
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38
Q

Most common pathogens in abdo abscesses

A

E. coli and Bacteroides

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39
Q

Most common pathogens in patients with ABX/hospital exposure

A

Candida
Enterococcus
Resistant gram -ve bacteria

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40
Q

Entamoeba histolytica

A
  • Protozoa from contaminated food

- Can cause amoebic liver abscess

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41
Q

E. histolytica liver abscess dx

A

Imaging, serology and liver aspirate (anchovy paste)

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42
Q

E. histolytica liver abscess tx

A

NO SURGERY
Metronidazole 5-10d
Paramomycin or iodoquinol (for asymptomatic carriers)

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43
Q

Candida albicans

A
  • Yeast

- Infection with: loss of mucosal barrier, immune deficiency, abx use

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44
Q

Common manifestations of Candida albicans

A
  • Oral thrush in HIV

- Candida esophagitis - dysphagia, odynophagia, nausea, vomiting, anorexia

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45
Q

Candida albicans tx

A

Fluconazole (14-21d)

46
Q

Fluconazole

A

Anti-fungal tx

47
Q

HSV: common infections

A
  • Herpes virus

- Oral, esophagitis, CNS, hepatitis, genital ulcers

48
Q

HSV dx

A

Clinical
Tissue or body fluid –> PCR
Histology: viral inclusions

49
Q

HSV tx

A

Acyclovir (IV/PO)
Valacyclovir (PO)
Prophylaxis if frequent outbreaks

50
Q

CMV: common infections

A
  • Herpes virus

- Esophagitis, retinitis, colitis, hepatitis, pneumonia

51
Q

CMV dx

A

Clinical
Elevated CMV serum viral load
Tissue or body fluid –> PCR
= suggest dx

Histology: owl eyes (enlarged lymphocyte cell with viral inclusion)
=confirms dx

52
Q

CMV tx

A

Ganciclovir (IV)
Valganciclovir (PO)
Reduce immune suppression

53
Q

Mycobacterium avid complex (MAC)

A
  • Non-tuberculous mycobacteria
  • Found in immune suppressed
  • Pneumonia, colitis, disseminated disease, lymphadenitis
  • fever, fatigue, weight loss, diarrhea, lymphadenopathy, cough
54
Q

MAC dx

A
  • clinical
  • imaging: lymphadenopathy, pull cavity/nodular infiltrate
  • culture: need 2 separate resp samples, blood culture
  • histology: colon, bone marrow, lymph node
55
Q

MAC tx

A
  • Rifabutin, Ethambutol AND clarithromycin for at least 12 months
  • Reduce immune suppression
  • Azithromycin prophylaxis when CD4 count <50 (ie. HIV pts)
56
Q

Causes of chronic diarrhea in HIV patients

A

Parasitic protozoa

  • isospora, cyclospora
  • treatable with Trimethoprim-Sulfamethoxazole
  • Microsporidia spp., cryptosporidium
  • immune reconstitution only
57
Q

Strongyloides stercoralis

A

Parasitic helminth

-usually most evident in immunosuppressed patients

58
Q

Infections from recent travel

A
  • ETEC
  • EAEC
  • Campylobacter
59
Q

Infections from day care centres

A
  • EHEC
  • Shigella
  • Norovirus
  • Rotavirus
60
Q

Infection from health care exposure

A

-C. difficile

61
Q

Infections common in immune compromised

A
  • Protozoa
  • MAC
  • CMV
62
Q

Infections common in young people

A
  • HUS
  • Rotavirus
  • Shigella
63
Q

Infections common in old people

A
  • C. Diff
  • Salmonella
  • HUS
64
Q

Empiric tx for febrile, inflammatory diarrhea in immunosuppressed host

A

3rd gen cephalosporin or ciprofloxacin

65
Q

Pathogens that should be considered for tx if symptomatic

A
  • Shigella
  • Campylobacter
  • E. histolytica
  • C.diff
66
Q

Pathogens that should NOT be considered for tx

A
  • EHEC (risk of HUS)

- Salmonella in a healthy host

67
Q

Pathogens that MAY be treated even if asymptomatic

A
  • Shigella to reduce spread in high risk settings (MSM, day care)
  • Salmonella in chronic carriers at high risk of transmission (food workers)
  • Entamoeba histolytica to prevent progression to invasive disease
68
Q

Mild C.diff

A

WBC <15 000 cells/uL AND serum creatinine <1.5x premorbid level

69
Q

Severe C.diff

A

WBC >15 000 cells/uL OR serum creatinine level >/=1.5x premorbid level

70
Q

2 alternatives to vancomycin for severe C.diff

A
  1. Fidaxomicin

2. Increase to 500mgQID PO + metronidazole = combo therapy (only for critically ill)

71
Q

Recurrent C.diff tx

A
  1. Treat again with vancomycin (QID until better, BID for 1 wk, OD for 1wk, q2d, q3d, then stop
  2. Stool transplant (FMT) – good but not always available
72
Q

Giardia lamblia

A

Intestinal protozoa

73
Q

Giardia lamblia tx

A

1st line in Canada = Metronidazole

1st line where available = Tinidazole

74
Q

Cystisospora belli

A

Intestinal protozoa

75
Q

Cystisospora belli tx

A

Self-limited in healthy hosts

Trimethoprim/Sulfamethoxazole (TMP-SMX) if prolonged

76
Q

Cyclospora cayetanensis

A

Intestinal protozoa

77
Q

Cyclospora cayatanensis tx

A

Self-limited

Trimethoprim/sulfamethoxazole if prolonged

78
Q

Cryptosporidium hominis tx

A

In HIV pt - HAART

In immune competent pt - self-limited (maybe nitazoxanide)

79
Q

Blastocystis hominis

A

Intestinal protozoa

Commonly found in asymptomatic individual

80
Q

Blastocystis hominis tx

A

Can consider MTZ, iodoquinol, paromomycin or TMP-SMX

81
Q

Dientamoebe fragilis

A

Intestinal protozoa

82
Q

Dientamoebe fragilis tx

A

If diarrhea >1wk and no other potential pathogen found, consider tx with MTZ, iodoquinol, paromomycin, tetracycline

83
Q

Entamoeba dispar

A

Intestinal protozoa

84
Q

Entamoeba dispar tx

A

No tx needed

85
Q

Non-antibiotic tx for infectious diarrhea

A
  • ORS (most effective)
  • Anti-emetics (ie. ondansetron, metoclopramide, domperidone)
  • Anti-diarrheals (ie. imodium/loperamide)
86
Q

Ondansetron MOA

A

5HT3 antagonist – specific serotonin receptor blocked such that serotonin cannot trigger vagal afferents to activate commit centre in brain

87
Q

Metoclopramide, domperidone MOA

A

dopamine antagonist – blocks dopamine receptors in chemoreceptor trigger zone in CNS (plus can block 5HT3 at high dose)

88
Q

Which drug should be avoided in children/adults with fever or abdominal distention?

A

Anti-diarrheals

Risk of ileus

89
Q

Loperamide MOA

A

u-opioid receptor agonist in myenteric plexus of LI –> decreases muscle contraction in LI = decreased gut motility

90
Q

Tx NOT recommended for gastroenteritis

A
  • Clay minerals (kaopectate) – no evidence
  • Antispasmodics – increased risk of toxic megacolon
  • Vit A – no benefit in acute epis
  • Diphenoxylate/atropine (lomotil) – not for infectious gastroenteritis
  • Opiates should be avoided f possible
91
Q

Recommended prophylactic tx for TD

A
  • Basic hygiene practices
  • Fluoroquinolone chemoprophylaxis (high risk pts)
  • Rifampin chemoprophylaxis (high risk pts)
  • Bismuth subsalicylate (anti-secretory agent)
92
Q

Top causes of fever

A
  • Malaria
  • Arbovirus: Dengue, Chikungunya, Zika
  • Typhoid
  • Rickettsial fevers
93
Q

Malaria

A
  • Returning traveler has malaria unless proven otherwise
  • Fevers, rigors, headaches, myalgia, anorexia
  • Severe: end organ dysfunction
94
Q

5 Malaria species

A 
P. falciparum
P. vivax
P. ovale 
P. malariae 
P. knowlesi
95
Q

Malaria dx

A

Thick and thin blood smears; 3 smears 12-24h apart

Rapid antigen tests (can’t determine parasitemia)

96
Q

Malaria tx

A

Severe pt:
1st line: Artesunate IV + doxy or clindamycin
2nd line: Quinine IV + doxy or clindamycin

Uncomplicated pt:
1st line: Arthemeter-Lumefantrine (not avail in Canada)
Others: Atovaquone-Proguanil (Malarone), Quinine + doxy/clindamycin, chloroquine

Treating oval and vivax (dormant forms in liver): chloroquine + primaquine*

97
Q

Arbovirus - big 3

A

Dengue fever
Chikungunya
Zika

98
Q

Arbovirus

A

Fever, arthralgia, myalgia, headache, blanching rash of dengue, nausea, vomiting, diarrhea, conjunctivitis (zika), low plts (dengue)

99
Q

Zika complication

A

Sexual and materno-fetal transmission
Fetal microcephaly if infection in utero
Infected/potentially-infected reproductive aged women: no attempts at conception for 2 months
Infection/potentially-infected men: no unprotected sex for 6 months

100
Q

Dengue complication

A

Hemorrhagic fever or shock syndrome

Required back to back infections

101
Q

Chikungunya complication

A

Persistent post-infectious arthralgia

102
Q

Zika dx

A

PCR if <10d from symptom onset + serology

103
Q

Dengue and chikungunya dx

A

Serology, acute and convalescent needed

104
Q

Arbovirus tx

A

Supportive care only

105
Q

Typhoid

A 
Salmonella type
Fecal-oral; contaminated water 
Prolonged fever (minimum 3d), fatigue, headache, +/- cough, constipation (adults), mild diarrhea (kids), apathy, neurocognitive findings
106
Q

Typhoid complications

A

~2wks after illness
Usually GI related b/c hangs out in Peyer’s patches
Intestinal perforation, GI bleed, sepsis

107
Q

Typhoid dx

A

Blood culture

108
Q

Typhoid tx

A

Ceftriaxone or azithromycin

109
Q

Rickettsial fevers

A

Spread by fleas, ticks, lice, mice
Some have rash, fevers
Can be life threatening

110
Q

Rickettsial tx

A

DOXYCYCLINE (for all types)

111
Q

C. diff symptoms

A
  • Watery, foul smelling diarrhea
  • Elevated WBCs without appearing very sick
  • Mild abdo discomfort
  • Pseudomembranous colitis (severe)
  • Toxic megacolon (severe)

Medd 422 (4 decks)

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