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Kat's Pathology > GI Infections > Flashcards

GI Infections Flashcards

(54 cards)

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1
Q

What groups are most vulnerable to GI infections

A

Infants

Elderly

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2
Q

What are the reportable GI infections of note

A 
Campylobacter
Salmonella 
Shigella 
E.coli O157
Listeria 
Norovirus
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3
Q

No fever or low grade fever

No white blood cells in stool sample

A

Secondary diarrhoea

E.g. vibrio cholerae, ETEC, EAggEC, EPEC, EHEC

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4
Q

Fever

White blood cells in the stool sample (neutrophilia)

A

Inflammatory diarrhoea

E.g. campylobacter jejuni, shigella spp, non-typhoid salmonella serotypes, EIEC

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5
Q

Fever

White blood cells in stool sample (mononuclear cells)

A

Enteric fever
E.g. typhoidal salmonella serotypes
Enteropathogenic yersinia spp
Brucella spp

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6
Q

Incubation period for campylobacter

A

1-10 days

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7
Q

Disease duration of campylobacter

A

2-20 days

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8
Q

Most common source of campylobacter

A

Poultry

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9
Q

Incubation period for E.coli O157

A

1-5 days

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10
Q

Disease duration of e.coli O157

A

1-4 days

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11
Q

Incubation period of shigella

A

12-96 hours

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12
Q

Disease duration of shigella

A

5-7 days

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13
Q

Incubation period of salmonella

A

8-48 hours

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14
Q

Disease duration of salmonella

A

4-7 days

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15
Q

Incubation period of vibrio parahaemolyticus

A

24-72 hours

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16
Q

Disease duration of vibrio parahaemolyticus

A

2-10 days

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17
Q

Most common source of vibrio parahaemolyticus

A

Shellfish

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18
Q

Mechanism of disease of cholera toxins

A

It is a secretory diarrhoea toxin production
cAMP: opens Cl channel at the apical membrane of enterocytes
Efflux of Cl to lumen: loss of H2O and electrolytes

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19
Q

Mechanism of disease of superantigens

A

They are secretory diarrhoea-toxin production
Superantigens bind directly to T cell receptors and MHC class II molecules OUTSIDE the peptide binding site.
This leads to a massive cytokine production by CD4 cells (i.e. systemic toxicity and suppression of adaptive responses)

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20
Q

Host responses in enteric fever

A

Intestinal inflammation –> bacteraemia (in an immunocompromised patient) –> weak stimulation of acute phase responses (monocytes) –> no septic shock and no neutrophilia

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21
Q

Host responses in inflammatory (exudative) diarrhoea

A

Exudative inflammation –> bacteraemia (immunocompromised patient) –> detection of LPS by monocytes expressing TLR4 –> TNFa, IFNg, IL1B –> neutrophilia and septic shock

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22
Q

Features of staphylococcus aureus food poisoning

Study These Flashcards
A

1/3 population chronic carriers, 1/3 transient
Spread by skin lesions on food handlers
Catalase, coagulase positive Gram positive coccus
Appears in tetrads, clusters on Gram stain
Yellow colonies on blood agar
Produces enterotoxin, an exotoxin that can act as a superantigen in the GI tract, releasing IL1 and IL2, causing prominent vomiting and watery, non bloody diarrhoea
Don’t treat, self limited

23
Q

Bacillus cereus

Study These Flashcards
A

Causes food poisoning
Gram positive rod: spore forming
Spores germinate in reheated fried rice (e.g. chinease fried rice)
Heat stable emetic toxin - not destroyed by reheating
Heat labile diarrhoeal toxin - food is not cooked to a high enough temperature

Causes: water non-bloody diarrhoea which is self-limited
Rare cause of bacteraemia in vulnerable population
Can cause cerebral abscesses

24
Q

Clostridium botulinum

Study These Flashcards
A

Gram positive anaerobe
Causes botulism
Source : canned or vacuum packed food (honey / infants)
Ingestion of preformed toxin (inactivated by cooking)
Blocks Ach release from peripheral nerve synapses
Treatment with antitoxin

25
Clostridium pefringens infection
Gram positive anaerobe Causes food poisoning Source : reheated food (meat) Normal flora of colon but not small bowel, where the enterotoxin acts (superantigen) Incubation 8-16hrs Watery diarrhoea, cramps,little vomiting lasting 24hrs
26
Clostridium difficile
Causes pseudomembranous colitis Occurs in 3% general population, 30% of hospitalised patients Antibiotic related colitis (any can cause it, but mainly cephalosporins, ciprofloxacin and clindamycin) Avoidance involved infection control Treatment: metronidazole, vancomycin, and stop the causative antibiotics where possible
27
Listeria monocytogenes infection
Outbreaks of febrile gastroenteritis Beta haemolytic, aesculin positive with tumbling motility Source : refrigerated food (“cold enhancement”),i.e. unpasteurised dairy, vegetables Grows at 4 ºC GI watery diarrhoea, cramps, headache, fever, little vomiting Perinatal infection, immunocompromised patients Treatment : ampicillin
28
Enterobacteriacae infection
Facultative anaerobes, glucose/lactose fermenters (LF), | oxidase negative
29
Escherichia coli infection
Enterobacteriacae Causes traveller's diarrhoea Source: food/water contaminated with human faeces Enterotoxins: Heat labile stimulates adenyl cyclase and cAMP Heat stable stimulates guanylate cyclase Act on the jejeunum, ileum not on colon ETEC; toxigenic, main cause of traveller’s diarrhoea EPEC; pathogenic, infantile diarrhoea EIEC; invasive, dysentery EHEC; haemorrhagic O157:H7 EHEC: shiga- like verocytotoxin causes HUS Avoid antibiotics
30
Salmonella infection
Non lactose fermenters, H2S producers, TSI agar, XLD agar, selenite F broth Antigens: cell wall O (groups A-I) flagellar H capsular Vi (virulence, antiphagocytic) Three species: S. typhi (and paratyphi) S.enteritidis S.cholerasuis
31
S. enteritidis salmonella infection
Causes enterocolitis Transmitted from poultry, eggs, meat Invasion of epi- and sub-epithelial, tissue of small and large bowel Bacteraemia infrequent Self limited non bloody diarrhoea ,usually no treatment Stool positivity
32
S.typhi salmonella infection
``` Causes typhoid (enteric) fever Transmitted only by humans Multiplies in Payer’s patches, Spreads ERS Bacteraemia, 3% carriers ``` ``` Slow onset, fever and constipation, Splenomegaly,rose spots, anaemia, leucopaenia, Bradycardia, haemorrhage and Perforation Blood culture positive Treatment : ceftriaxone ```
33
Shigellae infection
Non lactose fermenters, non H2S producers, non motile Antigens: cell wall O antigens Polysaccharide (groups A-D) : S.sonnei, S.dysenteriae, S.flexneri (MSM) The most effective enteric pathogen (low ID 50) No animal reservoir No carrier state Dysentery: invading cells of mucosa of distal ileum and colon Producing enterotoxin (Shiga toxin) Avoid antibiotics (ciprofloxacin if required)
34
Vibrios infection
Curved, comma shaped, late lactose fermenters, oxidase positive. Subtypes: cholera, parahaemolyticus, vulnificus
35
Vibrios cholera infection
O1 group: epidemics, biotypes El Tor, Cholerae and serotypes Ogawa, Inaba, Hikojima Non O1 group: sporadic or non pathogens Transmitted by contamination of water and food from human faeces ( shellfish, oysters, shrimp) Colonisation of small bowel and secretion of enterotoxin with A and B subunit, causing persistent stimulation of adenylate cyclase Causes massive diarrhoea (rice water stool) without inflammatory cells Treat the losses
36
Vibrio parahaemolytiocus infection
Ingestion of raw or undercooked seafood (ie oysters), Major cause of diarrhoea in Japan..or when cruising in the Carribean.. , Self limited for 3 days Cholerae : grows in salty 8.5% NaCl..
37
Vibrio vulnificus infection
Cellulitis in shellfish handlers Fatal septicaemia with D&V in HIV patients Treat with doxycycline
38
Campylobacter infection
Curved, comma or S shaped Microaerophilic C.jejuni at 42 ºC oxidase pos ,motile Self limiting but symptoms can last for weeks (20 days) Only treat if immunocompromised (macrolide) Transmitted via contaminated food and water with animal faeces (poultry, meat,unpast. milk) ? Enterotoxin (watery diarrhoea) ? Invasion (+/- blood) Watery, foul smelling diarrhoea, bloody stool, fever and severe abdo pain Treat with erythromycin or cipro if in the first 4-5days Associated with GBS syndrome, reactive arthritis, Reiter’s ..
39
Yersinina enterocolitis infection
-Non lactose fermenter, prefers 4ºC “cold enrichment” Transmitted via food contaminated with domestic animals excreta Enterocolitis Mesenteric adenitis Associated with reactive arthritis , Reiter’s
40
Mycobacteria infection (M. tuberculosis, M, avium, intracellulare)
Will appear as gram variable | Always think of TB
41
Entamoeba histolytica infection
``` Protozoa Motile trophozoite in diarrhoea Non motile cyst in nondiarrhoeal illness Killed by boiling, removed by water filters 4 nuclei No animal reservoir Ingestion of cysts -->trophos in ileum -->colonize cecum, colon -->“flask shaped” ulcer ``` Dysentery,flatulence, tenesmus Chronic : wt loss,+/- diarrhoea Liver abscess Diagnosis: stool micro (wet mount, iodine and trichrome), serology in invasive disease Treat : metronidazole + paromomycin in luminal disease
42
Giardia lamblia infection
``` Protozoa Trophozoite “pear shaped” 2 nuclei 4 flagellas and a suction disk Ingestion of cyst from fecally contaminated water,food ``` Excystation at duodenum tropho attaches no invasion malabsorption of protein and fat Travellers, hikers, day care, mental hospitals, MSM Foul smelling non bloody diarrhoea, cramps flatulence, no fever Diagnosis : stool micro, ELISA, “string test” Treatment: metronidazole
43
Cryptosporidium parvum infection
Protozoa infection Infects the jejunum Severe diarrhoea in the immunocomromised Oocysts seen in stool by modified Kinyoun acid fast stain Treatment : reconstitution of immune system
44
Norovirus unfection
``` Causes outbreaks Low ID (18-1000 viral particles) Environmental resilience (0-60 ºC) No long term immunity GII.4 currently predominant strain ```
45
Rotavirus infection
dsRNA “wheel like” Replicates in mucosa of small intestine Secretory diarrhoea, no inflammation Watery diarrhoea ? by stimulation of enteric nervous system By age 6 most children worldwide have antibodies to at least one type Exposure to natural infection twice confers lifelong immunity Huge economic burden worldwide
46
Adenovirus infection
Types 40, 41 cause non bloody diarrhoea <2yrs of age Can affect any type in immunocompromised Diagnosis : stool EM, antigen detection, PCR Types: Poliovirus, Enteroviruses (coxsackie, ECHO), Hepatitis A
47
Best prevention tactics for GI infections
``` Breastfeeding, improved weaning practice Clean water for drinking Safe disposal of stools of young children Precautions when travelling Food handling Public health notification Good handwashing Good handwashing Good handwashing ```
48
What vaccines are available against GI infections
Cholera Campylobacter ETEC Salmonella typhi
49
Cholera vaccine
Serogroups O1(Inaba , Ogawa, biotypes El Tor and classical), O139 Inactivated, whole cell, contains all above + B subunit of toxin (PO) Live attenuated (PO) not recommended
50
Campylobacter vaccine
Military, infants,traveller, candidate vaccines exist..
51
ETEC vaccine
Inactivated and live vaccines in trails
52
Salmonella typhi vaccine
Vi capsular PS (IM) and (PO)live
53
Rotavirus vaccines
Rotarix: live attenuated human strain monovalent, 2(PO) doses Rotateq: pentavalent, 3 (PO) doses, one bovine and four human strains Rotashield and intussusception (8-20 weeks) Age of vaccine is 6-12 weeks.
54
What are the public health implications in GI infections
Notifiable disease Each trust to notify to local Health Protection Unit Notifiable diseases: Campylobacter, Clostridium sp, Listeria monocytogenes, Vibrio, Yersinia Identify outbreaks in areas Environmental Health Officers to inspect premises and take samples from environment and food

Kat's Pathology (105 decks)

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