Lecture 48 to 53 GIT Infections Flashcards

Question

B. cereus

Answer 1

* 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

Answer 2

* non-enveloped ds RNA virus * Family: reoviridae * 10 serotypes (G1 to G4 important) * most common genotypes: G1, G2, G3, G4 & 9 with [P8] & [P4] * Group 1: worldwide * Group 2: limited distribution (China) * Epi: infection of Rotavirus in children\< 5 yo due to lack of vaccinations in S. America, Africa, and Asia * unsafe water & poor sanitation * seasonal * Transmission: fecal-oral, water-borne, air-borne * **Contaminant: **Raw or mishandled food? * **Incubation:** \< 48 h (1 to 3 d) * **Duration**: 4 to 6 d **Etiopath: ** * replication in epithelial cells of SI * shedding may persist for 10 d or more; peak within 8 d * histopath: * shortening & blunting of villi -\> transient lactose intolerance * patchy, irregular intact mucosa * mononulear cell infiltration of lamina propria * diarrhea results from loss of absorptive area & flux of water/fluid across damaged surface * **Sx:** sudden onset watery diarrhea w or w/o vomiting up to 6 d * **Complications:** dehydration, severe & life-threatening * **Dx: ** * Virus in stool * latex agglutination * **Prevention: r**otavirus vaccine

Answer 3

* +ss RNA, enveloped, calicivirus * family: noroviridae * 4 genera (norovirus, saprovirus, lagovirus, vesivirus) Sapoviruses * children & adults (elderly) * 5 genogroups: humans GI, II, IV, V, VI * 50% of outbreaks of acute, non-bacterial gastroenteritis (US) * Setting: - cruise-ships - long-term care faciility -\> hospital wards closed during Christmas period - restaurants - winter months * Transmission: fecal-oral route, water-borne, * **Contaminant**: food-borne ex. raw shellfish, sandwiches, salads, etc * **Onset: **1 to 2 d * **Duration: **1 to 2 d * **Etiopath:** * virus multiplies in small intestine * produces transient lesions of intestinal mucosa * spares large intestine (No fecal leukocytes) * shed in feces * **Sx:** mild & brief * ab cramps, myalgias, malaise, headache, nausea, low grade fever & watery diarrhea * **Dx:** epi criteria including vomting and no bacteerial agent previously found * difficult to culture * RT-qPCR * **Prevention:** norovirus vaccine from VLP (w chistosan and monophosphoryl lipid A as adjuvants); 2 doses IM, 3 wk apart

Answer 4

* ds DNA, icosahedral * 2 serotypes associated: 40 & 41 (Group F) * Etiiopath: * Main target: RT * Infect: epithelial cells of pharynx, conjunctiva, **small intestine** & occasional other organ systems, * Sx: diarrhea w or w/o vomiting (#2 behind rotavirus)

Answer 5

* family: Astroviridae * small, naked +ss RNA * 2 to 8 % sporadic cases in infants (3rd behind rotavirus)

Answer 6

* Transmission: Fecal-oral-\> mainly food items such as shellfish, strawberries, salad items * jaundice does not appear until other sx have subsided * virus shedding in feces (10 to 14 d after exposure)

Answer 7

* naked +ss RNA * incubation: longer than HAV (mean 6 wk)

Answer 8

* Shigella spp. * Camplyobacter spp. * Vibro parahaemolyticus & V. vulnificus * Salmonella spp. * Yersina * E. coli (EIEC) * EAEC & STEC (EHEC)

Answer 9

* 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

Answer 10

* Location: SE Asia/S America * similar to Shigellosis but no toxin and less severe * infective dose: 10 cells * **Contaminants:** lettuce, manure fertilizer * **Onset: **at least 18 h * **Duration: **uncertain * **Etiopath: ** * enters Large Intestine * shuts down protein synthesis * cell necrosis in WBC (pus) & RBC (blood in stool) * **Sx: **cramps, diarrhoea, fever, dysentery * **Rx**: ORT

Answer 11

* 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 Rx: Fluoroquinolones but antibiotics may prolong sx

Answer 12

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

Answer 13

**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

Answer 14

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

Answer 15

* Etiopath: poorly understood * Induced polyclonal T-cell stimulation (toxin) * Non-specific immune stimulation of invasin binding to b1 integrins on T lymphocyte * Other bacterial antigens * Dx: rising Ab titres in paired serum (4x incr) * Mac Agar (pinpoint colonies/48 h) * Specialised Yersinia media

Answer 16

* not agglutinated by anti-O1 sera * halophilic organisms (common coastal waters) * V. parahaemolyticus * V. alginolyticus: strict halophile requires at 3% NaCl for the growth and can survive salt concentration up to 10% NaCl. It is sucrose fermenter and yields yellow colonies on TCBS agar. * V. vulnificus * V. cholerae (not toxigenic V. cholerae O or O139)

Answer 17

* ingestion of raw/poorly cooked seafood; Japan (raw fish) & US (shellfish) * **Contaminant**: Fish & seafood * **Onset: **12 to 24 h * **Duration: **4 to 7 d * **Sx:** acute ab pain, vomiting & watery diarrhea, sometimes fever & headache * Rx: tetracycline

Answer 18

* **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

Answer 19

* Etiopath: not fully understood * NO EAF (Enteric Adherence factor) * Possess AAF (Aggregative Adherence factor) * 1) Initial adherence to intestinal mucosa and/or mucus layer (fimbriae) * 2) Enhanced mucus prodn

Answer 20

* causes life threatening conditions * HAEMORRHAGIC COLITIS w severe ab pain w/in days of ingestion * HAEMOLYTIC UREMIC SYNDROME (8 -11% cases) bloody diarrhea followed by 3 sx: - in children Acute renal failure Thrombocytopenia Microangiopathic haemolytic anaemia * THROMBOTIC THROMBOCYTOPENIA PURPURA: life-threatening to elderly - similar to HUS but also have neuro sx * Note Edema caused by: 1. heart -\> limbs 2. liver -\> ascites 3. kidney -\> facial swelling generalized = anasarca Etiopath: * Attachment (similar to EPEC) * Phage encoded: CYTOTOXIN - VEROTOXIN * 2 types (VT1 & VT2) both AB toxins * Shiga-like toxin (rRNA) blocks protein synthesis Dx of E. coli * Mac agar: no fermentation of sorbitol * ETEC: innoculate mouse adrenal cells: stimulation of AC by LT/ST * ELISA on toxin bound to Ab * DNA probe to detext toxin genes

Answer 21

Antibiotic-Associated Diarrhoea - C. difficile Gastritis/Duodenal/Gastric Ulcers - H. pylori Gastrointestinal Abscess (Peritonitis, Appendicitis & Diverticulitis) - E. coli & Bacteroides spp. + others

Answer 22

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

Answer 23

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

Answer 24

NOTE: Anaerobes resistant to penicillins, cephalosporins & most amino-glycosides including **Enterotoxicgenic Bacteroides Fragilis (ETBF)** Possibilities Chloramphenicol (succinate): Bacteroides fragilis Metronidazole: All Bacteroides spp. Gentamycin, Tobramycin & Amikacin: useful Clindamycin: 60% Bacteroides spp sensitive

Answer 25

**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

Answer 26

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

Answer 27

**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)

Answer 28

classified in the family Vibrionaceae and contains only one species:Plesiomonas shigelloides and has following characteristics: * Gram negative bacillus * Oxidase positive facultative anaerobe * Motile with multiple polar flagella * Found in brackish water * Infection is associated with ingestion of uncooked shellfish * Plesiomonas shares antigenic and biochemical features with Shigella.