Lecture 48 to 53 GIT Infections Flashcards
1
Q
Colonisation of GIT
A
- Immediately after birth: E. Coli & Strep
- 4 d after birth: facultative anaerobes appear and create reducing environment; Bifidobacterium, clostridium, bacteroides
- Breast fed: only Bifidobacterium levels remain high, all others decline
- Formula fed: Lactobacilli present
- Beginning of weaning: E. coli, strep, and clostridium return to high levels
- Completion of weaning: adult flora
2
Q
Normal commensal flora of Mouth
A
- Strep, Neisseria, Actinomyces, Lactobacillus, Veillonella
- Eruption of 1st teeth: Porphyromonas, Prevetella, Fusobacterium.
- Growth of teeth: Strep. mutans, strep. salivarius, strep. sanguis
3
Q
Stomach: normal commensal flora
A
- nl: sterile or up to 1000 bacteria (strep, staph, lactobacilli, peptostrep)
- pathological: H. pylori, 10e5 to 10e7 in achlorhydria or malabsoprtion syndrome
4
Q
Duodenum: normal commensal flora
A
- sparse but increases w distance away from stomach (0 to 10e5)
- fluctuating: Strep, Staph, Lactobacilli, some yeasts
-
Note: complete absence of coliforms & Bacteroides
- coliform: rod-shaped Gram-negative non-spore formingbacteria which can ferment lactose Ex. E. coli
5
Q
Jejunum-Ileum: nl flora
A
- high counts of Enterobacteriaceae
- some Strep, Staph, Lactobacillus, Bacteroides, Bifidobacterium, Clostridium
- bacteria numbers increase at ileocecal junction and highest, richest at large intestine
- bacteroides
- other anaerobes: bifidobacterium, eubacterium, peptobacterium, clostridium, enterobacteriacea
- also facultative anaerobes: E. coli
6
Q
Upper GI Infections
A
Dental plaque=Biofilm infection
- Strep. mutans & 39 other bacterial spp
- bacteria secrete dextran for adherence
- fusobacteria & actinomyces
- Lactibacilli produce lactic acid that destroy enamel of teeth
Periodontal disease & Tartar
- Porphyromonas causing gingivitis
Oral abscess
- infection in tooth
7
Q
Major causes of Gastroenteritis
A
50% Norovirus
50% bacterial
- Campylobacter
- Salmonella
- Shigella
- STEC O157:H7 E. coli strain
- STEC non-O157:H7
8
Q
Food-poisoning: toxemia
A
- consumption of foods containing toxins so **short incubation period **(except C. bot -> long incubation; below)
- only Clostridium botilinum, Staph. aureus, B. cereus (1 form),
- some fungi: Amanita, Clitocybe & Psilocybes, Aflatoxin
- and marine toxin: Ciguatera, Scromboid, shellfish
- contrast w food-associated infections caused by wide variety of pathogens
- Sx: usually rapid (minutes to hours)
- C. botulinum: 6h to 8 d
- no fever, no fecal leukocytes
- toxins affect:
- C. bot -> only CNS
- S. aureus & B. cereus: -> CNS and intestines
9
Q
A
Staph. aureus: food-poisoning
- Catalase +ve, Coagulase +ve, Beta-hemolytic
- produces 8 exotoxins (A, B, C1, C2, C3, D, E)
- water-soluble, HEAT STABLE (ST) (chromosomal)
- frequently implicated are A & D singly or combination
- Mechanisms: unknown
- neurogenic: vomitting via CN X
- diarrhea: enteric but no cAMP activation
- Contaminant: Ham, meat & poultry products, cream-filled pastries, whipped butter, cheese
- Onset: 1 to 6 h
- Duration: 6 to 24 h
Sx: self-limiting illness
- some emesis but not all vomit
- recovery in 24 to 48 h
- other common sx: headaches, nausea, ab cramps, prostration, muscle aches
- Foods: cooked meats (fish & poultry), cream-filled foods, dairy products, fuit, veggies, salads
- Highest: summer and holiday seasons
Dx & isolation: variety of media available (MSA)
- Baird Parker (selective, diagnostic, recovery)
- Confirm w coagulase test
10
Q
Bacillus cereus (food poisoning)
A
- Gram +ve rods, chains, aerobic or facultative
- spore former
- Encapsulated w protein (Poly-D-Glutamic Acid)
- emetic toxin or enterotoxin
- easily spread to food: cross-contamination
- 2 types of gastro
- Emetic resembles Staph. aureus
- Incubation: short 2 to 3 h
- Duration: 6 to 24 h
- Toxins: ST neurotoxin (peptide), EF (Edema Factor), LF (Lethal Factor)
- Foods:
- boiled rice, ex. Chinese restaurant syndrome
- pulses=lentils, split peas
Sx:
- Nausea, vomiting; sometimes diarrhoea & cramps
- Most common effect of Bacillus infections are cutaneous black eschar
Dx & isolate: implicated foods contains > 10e5
- non-selective medium: blood agar
- EF causes incr cAMP
Rx:
- Fluoroquinolones
- Cyclosporin
11
Q
C. bot (food poisoning)
A
C. bot
- variable size Gram +ve
- Obligate anaerobic
- ferment range of carbs -> gas
- spore former, produce exotoxins, susceptible to penicillin
- habitat: lower GI of human & animals
2 types of botulism:
- food poisoning: rare
- Sausages & fermented foods
- canned foods
- infant bot: most common bot in US
Neurotoxin: Cleves SNARE protein and decr ACh
- 8 types: A, B, C1, C2, D, E, F, G
- Humans: A, B, E, rarely F
- US frequent isolate type A, then B & E
- Europe frequent isolate type B (A rare)
Food poisoning botulism:
- Foods:
Type A&B: vegetables, fruits, meat, fish & poultry
Type E: fish
- Onset: 12 to 36 h
- Duration: months
Etiopath: INGESTION OF PRE-FORMED TOXINS
- almost all GI disturbances from toxin E; 1/3 Pt (toxin A or B)
Sx: mild illness or serioues disease (fatal within 24 h)
- nausea, vomting, and ab pain, diarrhea often present
- constipation
- diplopia
- dysphagia
- no fever in absence of complicating infections
- Descending flaccid paralysis
- Ptosis
Dx:
- presumptive dx: presence of rapidly descending paralysis
- confirmative dx: demonstrate botox in serum/faeces or food (mouse toxin-neutralization test)
12
Q
Infant Botulism
A
Infant botulism: NOT FOOD POISONING (2wk to 6 mo)
- Toxins: Types A & B implicated
Etiopath:
- INGESTION OF SPORE
- From environment -> entry into baby -> spore germination (GI tract) -> vegetative cells -> replicate & release toxin
- Spores commonly found in honey
Sx:
- illness & constipation (overlooked)
- Floppy baby syndrome
- lethargy, sleep more than normal
- suck & gag reflex diminished
- dysphagia becomes evident as drooling
- later: head control lost -> infant becomes flaccid -> resp. arrest
Dx: botox in feces
Rx:
- botulism antitoxin heptavalent (A, B, C, D, E, F, G) (Equine)
- baby botulism Ig (BIG-IV) for A & B toxins
13
Q
Types of diarrhea
A
non-inflammatory= watery; from non-invasive diarrhea or viruses inflammatory = blood or pus -\> from invasive bacteria or those producing cytotoxins
- Invasive diarrhea: do not give anti-diarrheal; cause inflammatory diarrhea; salmonella; break mucosal walls
chronic>4 wk due to:
- medication
- parasites
- malabsorption
14
Q
Mushroom toxin
A
Short acting: wild mushrooms
- toxins: psilocybine, muscarine, museino, coprius artermetaris, ibotenic acid
- incubation < 2h: vomitting, diarrhea
Long acting: amantia mushroom
- toxin: amantia
- incubation 4 to 8 h: cramps, diarrhea
15
Q
Mycotoxigenic fungi
A
- Mycotoxins: aspergillus, fusarium, penicillium
- Aflatoxins: Aspergillus flavus & A. parasiticus
- peanuts, corn & cotton (oil seeds) contamination
- SOA: liver cirrhosis & carcinoma, acute necrosis
16
Q
Marine toxins
A
- Ciguetera poisoning; heat stable toxin so cooking does not destroy
- dinoflagellates produce ciguetera toxin; big fish eat dinoflagellates (Barracuda, Amberjacks, Grouper)
- Sx: acute GI sx 3 to 6 h
- watery diarrhea
- nausea
- abdominal cramp (12 h)
- Complication: neuro sx (extremity paresthesia, severe itching, hot/cold temp reversal)
17
Q
Scromboid poisoning: non-allergic histamine
A
- Bacteria: Stentorophomonas maltophilia, M. morganii
- Toxin: Histamine (scrombotoxin); heat & cold stable toxin so cooking and freezing does not destroy
- Scrombridae fish: tuna, mahi mahi, marlin & bluefin
- Sx: acute GI sx -> minutes to 3 h afger ingestion
- Burning sensation in mouth, a metallic taste
- Watery diarrhea, nausea, lasting 3 to 6h
- dizziness, rash, facial flushing, generalised itching, paresthesias
18
Q
Neurologic shellfish poisoning
A
- dinoflagellate algae: Karenia brevis
- Toxins: brevetoxins
- Incubation: < 1 to 3 h
- Duration: 2 to 3 d
- Paresthesia, mouth numbness, tingling sensation of mouth & extremities, GI upset
19
Q
Paralytic shellfish poisoning
A
- dinoflagellate algae: Alexandrium spp., Gymnodinium catenatum, Pyrodinium bahamense, Gonyaulax spp.
- Toxin: Saxitoxin
- Incubation: < 2 h; duration: 3 days
- Sx: GI sx less common
- tingling & numbness of mouth spread to extremities
- ataxia (muscular in-coordination)
- severe cases: muscular paralysis, respiratory paralysis
20
Q
Non-Inflammatory diarrhea
A
Bacterial
- E. coli (ETEC, EHEC)
- V. cholera
- C. perfringens
- B. cereus
Viral
- Rotavirus
- Norovirus
- Adenovirus
- other
21
Q
EnteroToxigenic E. coli (ETEC)
A
- Disease: Traveler’s diarrhea
- Contaminant: contaminated food & water
- Onset: 10 h to 3 d
- Duration: 3 to 5 d
Common E. coli features
- encapsulated
- Catalase +
- Green colonies on EMB agar
- Lactose fermenter -> pink colonies on Mac agar
- K antigen can lead to neonatal meningitis
- Fimbri allow bacteria to cause UTI infection (#1 cause; see UGI FC)
- Can lead to sepsis
Etiopath:
- bacterial must colonize small intestine:
- CFA pii (colonizing factor)
- heat LABILE LT toxin: binds GM1 at brush border of epithelial cells -> facilitate entry of subunit A -> cAMP -> Cl transporter -> watery diarrhea
- heat STABLE ST toxin: activates cGMP -> watery diarrhea
Sx: rapid onset of watery diarrhea w/o fever, sometimes cramps, nausea & vomiting
Rx: E. coli resistant to trimethroprim
23
Q
Vibrio cholerae
A
Toxin: Vibrio toxin Vibrio cholerae
- single curved Gram -ve rods
- S-shaped when joined together
- “Shooting-star” motililty
- spore forming
- Oxidase +
- Acid-labile
- Antigens: O & S
- O1: El Tor strain
- O139: more recent
Epi: Asia, Africa, Americas
- Contaminant: Fecal-oral -> Food or water contaminated by faeces of infected individuals
- Onset: 2 to 3 d
- Duration: 1 wk
Etiopath: similar to ETEC in:
- Toxin: Vibrio toxin
- fimbriae attaching to GM1
- activates Gs -> AC -> cAMP -> watery diarrhea
- hypokalemia & metabolic acidosis (loss of bicarb)
Sx: rice watery diarrhea (20 to 30 L/d), vomiting, dehydration; fatal if untreated
Dx:
- clinical presentation
- screening of stool sample
- Grows on alkaline media
- Thiosulphate Citrate Bile Salts (TCBS) agar
- Sucrose differentiation media: only Vibrio cholerae sp can ferment sucrose (other Vibro spp cannot)
Rx: ORT & tetracycline
Prevention: sanitation and hygiene
24
Q
C. perfringens
A
- Obligate anaerobe
- Diseases: 2 different disease
- necrotizing enteritis (rare, Papua New Guinea)
- type A food-borne infection; major cause of food-borne infection in US
Contaminant:
- Cooked meat & meat gravy
- Spores in soil; common in military, motorcycle accidents, and trauma
- Onset: 8 to 24 h
- Duration: < 24 h, slow
Etiopath:
- Clostridium Perfringens Enterotoxin (CPE) in the intestinal villi cause cramps and diarrhea
- alpha-toxin affects cell membrane (lecintinase) and hemolysis
Sx:
- slow onset watery diarrhea, severe ab pain, no fever, nausea & vomitting rare
- gas gangrene aka clostridial myonecrosis/osteomyelitis
- gas in tissue on CT scan
- crepitance
Dx:
- Double zone of hemolysis when plated
- case hx & sx
Rx: penicillin
25
Q
B. cereus
A
- Food-borne Bacillus cereus different from toxin B. cereus
- rice not implicated in food-borne B. cereus
- Incubation: 8 to 16 h (longer)
- Duration: 12 to 24 h
- Etiopath: LT Enterotoxin -> AC
- Sx: diarrhea & ab pain
33
Q
Shigella spp.
A
- 4 groups
- S. dysenteriae: most severe form
- S. flexneri: homosexuals & prisons
- S. boydii
- S. sonnei: children < 5 yo (daycare)
- Closely related to E. coli (antigens & toxin-capabilities)
- Transmission: fecal-oral (4F)
Virulence factors
- Type III secretion system for inflammatory cytokines
- Endotoxin: O Ag
- Exotoxin: enterotoxin act as neurotoxin causing
- meningitis
- coma
- NAD glycohydrolase -> destroys all NAD in cells -> necrosis
- Low infective doses (10 cells)
- Contaminant: raw food
- Onset: 12 h to 4 d
- Duration: 4 to 7 d
Etiopath: Shigella dysenteriae type 1 (Shiga bacillus)
- Use of actin filaments to enter M cells
- replicate in M cells and spread to adjacent cells
- Shiga toxin (cytotoxin) inhibits 28s & 60s subunits of ribosomes and shuts down protein synthesis
- lyse cells using ADP hydrolase
- Enterotoxin: produces diarrhea
- Exotoxin: inhibits sugar & aa absorption in SI
- Neurotoxin: affects CNS
Sx:
- Bloody Diarrhoea, fever, nausea, sometimes vomiting & cramps
- HUS common in children
- Glomerular damage
- PLT count drop
Dx: Stool & Mac Agar showing Shigella
- clear colonies on Mac agar (lactose non-fermenter)
- non-motile
- acid stable
- no H2S production except S. flexneri -> green colonies on Hektoen agar
- no gas from glucose
- no utilization citric acid
Rx: antibiotics: chloramphenicol, ampicilin, tetracycline
35
Q
Salmonella genus
A
- Gram -ve bacilli
- encapsulated
- facultative intracell in macrophages
- Type III secretion system for inflammatory cytokines
- Salmonella enterica subspecies enterica serotype XXX
- Salmonellosis 3 clinical manifestations
- Gastroenteritis: S. Typhimurium, S. Enteritidis, S. Newport
- Salmonella septicemia (rare): S. Cholerasui
- Typhoid fever: S. typhi
- Serotypes implicated: S. Typhimurium (whole fat milk, dairy)
- Setting: children playing w friends pet turtle and reptiles and then eating sandwiches
Contamination: S. enteridis
- Raw & undercooked eggs, meat & poultry; raw milk; Reservoir: chicken
- Onset: 5 to 72 h
- Duration: 1 to 4 d
Etiopath:
- No Toxin! Invasive though -> incr prostaglandins & cAMP
- penetration of small and large intestine
- replication in M cells of Peyer’s patches
- causes secretion of electrolytes
- penetration into lamina propria for some individuals
Sx: Inflammatory Diarrhoea, abdominal pain, chills, fever, vomiting, dehydration
Dx: Stool & Mac Agar
- motile
- no lactose fermentation
- H2S production -> black colonies on Hektoen agar plate
- Gas from glucose
- Acid-labile
- serotyping
- motile
Rx: Fluoroquinolones but antibiotics may prolong sx
36
Q
Typhoid/Enteric Fever
A
Typhoid/Enteric Fever
- important morbidity/mortality worldwide
- US: only see in travellers to Asia, Mexico, India
- S. Typhi only (S. paratyphi A, B or C)
- Transmission: fecal-oral
- Prevention: vaccines & good sanitation
- in Gall Bladder of chronic carriers (2 wk post-infection)
Sx:
- Hx of travel to endemic area
- rose coloured spots on abdomen (2 to 4 d)
- constipation
- pea soup diarrhea
- osteomyelitis
- Sickle cell Pt susceptible
- blood tests (anemia, leukopenia, absence of eos)
- isolation of S. Typhi on S-S agar
Dx
- Widal rxn (agglutination of O & H Ag)
- Bismuth sulfite is a selective medium and is used for rapid detection of Salmonella typhi.
Vaccine: live attenuated
37
Q
Campylobacter spp
A
Morphology:
- curved Gram -ve rods, “gulls wings shaped”
- non-spore forming
- Catalase +
- Oxidase +
- microaerophile: 5% O2, 10% CO2
- Growth at 37C (C. jejuni) or 42C (C. intestinalis); no growth at 25C) -> likes heat
- Do not ferment carbs
- Setting: Children playing w cats and dogs; Zoonotic
- considered #1 food-borne disease
Reservor: poultry
- Onset: appear after 3 to 5 d post-ingestion
- Duration: 2 to 10 d
Etiopath:
- invasive
- toxins: endotoxin, enterotoxin (watery diarrhea), verotoxin (similar to Shiga toxin)
Sx: vomiting, bloody stool prostration, ab pain, fever
Dx:
- microscopy: presumptive dx
- culture (spreading; mucoid, grey colour) & biochem (oxidase, catalse): definitive dx
Assoc & Complications:
- Reactive arthritis aka Reiter’s syndrome: knee joint
- GBS -> ascending paralysis
38
Q
Yersinia enterocolytica
A
Yersinia enterocolytica
- lesser cause of Yersiniosis is Y. pseudotuberculosis
- Common in children <7 yrs (1-4 y);
- Rivals Salmonella - acute gastroenteritis (cooler climates)
- -1 - +40oC (Psychrotroph – Facultative psychrophile)
- motile @ 25C
- non-motile @ 37C
Common features of Yersinia
- Gram -ve bacteria
- Encapsulated
- Resistant to cold
Unique features of Y. enterolytica
- Bipolar straining (safety pin appearance)
Contaminant: raw or uncooked pork, contaminated milk
- Incubation: 3 to 7 d;
- Duration: 2 to 3 wk
Etiopath: poorly understood
- Invasive induces inflammatory response
- Distal ileum (gut-associated lymphoid tissue)
- Adjacent tissues & mesenteric lymph nodes also infected (mimic appendicitis)
- (Chromosomal) ST Enterotoxin -> incr cGGMP
Sx:
- RUQ pain mimicing appendicitis
- Bloody diarrhea
- mild fever
- vomiting rare
Rx: oxytetraccline or doxycycline w streptomycin
Vaccine: killed vaccine
42
Q
Vibrio vulnificus
A
- Foods: oyster and shellfish
- Setting: fishermen and sea shore bathers
- Onset: in people w high serum iron 1 day
Sx:
- Severe disease with liver disease
- diarrhea & infection of cuts
- chills, fever, prostration, death
- intense skin lesions (gastroenteritis & even severe bacteremia) -> severe & rapid cellulitis often requiring amputation
Dx: clinical presentation (not cholera)
- screening of stool samples
- oxidase activity
- TCBS agar
- sucorse (differentiating agent)
- sucrose -ve -> V. parahaeolyticus, V. vulnificus
46
Q
C. diff
A
C. diff causing pseudomembranous colitis
- spore-forming
Etiopath: 2 toxins
- Nosocomial infection: C Diff infection after Clindamyin use & poor hygiene by hospital workers.
- Toxin A enterotoxin (fluid accumulation in bowel): affects brush borders of intestines
- Toxin B potent cytotoxin: Decreases cellular protein synthesis & disrupts Actin filament system of cells by depolymerization (similar to diphtheria toxin)
Sx: vary
- Mild diarrhoea→severe abdominal pain accompanied fever (>101oF) & severe weakness
- Diarrhoea: watery usually non-bloody (5-10% bloody); voluminous & greenish
- excess mucus & pus (or blood) Hypoalbumineia & Leukocytosis common
Dx: used to be difficult (see italic text)
- PCR for toxin
- Not distinguished from Ulcerative colitis & Crohn’s
- Colonic examination (presence of pseudomembrane) AND Isolation C. difficile, associated antibiotic therapy Toxin presence
Rx:
- Discontinue antibiotic - symptoms resolve 1-14 days
- Oral Vancomycin (“gold” standard) if severe or no response;
- Oral Metronidazole (milder infections) Relapses in 15-20% patients
- Faecal microbiota transplantation
- Dificid (fidaxomicin) bid 10 days
47
Q
H. pylori
A
H. pylori
- Gram -ve
- Curved to spiral (1-3 turns)
- Motile - polar (5-6) flagella
- Non spore-forming
- Microaerophilic 2-5%O2, 5-10%CO2
- Catalase +
- Urease + Coccoidal forms under culture
- Oxidase +
Etiopath: Gastric colonisation is common
- Risk factors: smoking, alcohol, NSAID, PPI
- Role of cytotoxin, urease, mucinase, flagella mechanisms UNDER INVESTIGATION.
- UREASE allow H. pylori survival at pH 2.0
- Able to split ammonia from urea = alkaline environment
- Virulence Factors: allowing for adhesion & damage to mucosa
- cag PAI:
- VacA cytotoxin;
- BabA;
- OipA
Dx:
- Rapid presumptive: Urea Breath test
- Definitive: culture, serology, histopath stain -> Biopsy & Urease test
Assoc diseases
- Gastritis (stomach atrum)
- Duodenal ulcers (& gastric ulcers)
- Gastric cancer
- MALToma
Rx: Triple, Quadruple or Sequential regimens effective
- PPI
- Macroglide
- Amoxicillin
- Clathrimicin
49
Q
EHEC
A
Contaminant:
- raw or undercooked beef, raw milk, unpasteurized fruit juices
- O157: H7 cause of outbreaks
- does not ferment sorbitol -> colourless on Sorbital Mac (SMAC)
- Onset: 3 to 8 d:
- Duration: 2 to 9 d
Etiopath:
- Shiga-like toxin causes inflammatory diarrhea -> inhibit protein synthesis in LI by nicking 60S ribosome
Sx:
- Watery then bloody diarrhoea but non-invasive (exception)
- kidney failure -> HUS and PLT count drop
50
Q
Listeriosis
A
Listeria Monocytogenes
- Beta-hemolytic
- Catalase +
- Facultative anaerobe
- Tumbling motility
- Motile @ BT by actin polymerization “Actin rockets”
Contaminant:
- Raw milk, soft cheese, processed meats & vegetables
- L. monocytogenes survives in cold!
- Onset: 3-70 days
Sx:
- Pregnant need to stay away from soft cheeses and processed meats
- Meningo-encphalitis;
- septicemia or meningitis in newborns
- still births
Rx:
- Ampicillin along w Vancomycin and Ceftriaxone
51
Q
Klebsiella, Serratia, Enterobacter (Sketchy micro)
A
Common features
- Gram-ve bacilli
- Enteric tract
- MDR
- Lactose fermenters-> pink colonies on Mac agar
- Diseases: Pneumonia & UTI
Enterobacter
- motile
Serratia
- motile
- produces red pigment
- prolonged urethral cath
Klebsiella
- encapsulated
- non-motile
- urease +
- prolonged urethral cath
- Triple A: alcoholics, abscess, aspiration
- Sx: red currant jelly sputum
- Dx: cavitary lesion on CXR (resembes Tb)
