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Infectious Diarrhea. Learning Objectives Microbiology –Recognize common and atypical pathogens Pathogenesis –Understand general mechanisms of infection.

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Presentation on theme: "Infectious Diarrhea. Learning Objectives Microbiology –Recognize common and atypical pathogens Pathogenesis –Understand general mechanisms of infection."— Presentation transcript:

1 Infectious Diarrhea

2 Learning Objectives Microbiology –Recognize common and atypical pathogens Pathogenesis –Understand general mechanisms of infection / categories Clinical approach –Identify important elements in the clinical history –Diagnostic algorithm Review of selected organisms Management of acute infectious diarrhea Common causes of persistent infectious diarrhea

3 Intestinal Infections - Common Viral -Norovirus- Rotovirus Bacterial -Salmonella ( GNR )- Yersinia ( GNR ) -Shigella ( GNR )- Bacillus ( GPR ) -Campylobacter ( GNR )- Clostridium ( GPR ) -Vibrio ( GNR )- Staphylococcus ( GPC ) -E.coli ( GNR ) Protozoal -Giardia- Entamoeba

4 Intestinal Infections - Uncommon Viral –CMV Bacterial –Mycobacteria M. tuberculosis M. avium complex M. bovis –Tropheryma whipplei –Listeria monocytogenes –Brucella species Fungal –Histoplasma –Candida Parasites –Protozoa Cryptosporidia Isospora/Cyclospora –Worms Tapeworms Roundworms

5 Bacterial GI Infections Noninflammatory –Clinical manifestation Diarrhea - watery to loose, ± nausea/vomiting/abd pain –Mechanism: Preformed toxin, enterotoxin Inflammatory –Clinical manifestation Diarrhea – mucoid or bloody, fever, tenesmus, ± abd pain –Mechanism: Cytotoxin, cellular invasion Invasive ( mononuclear inflammation ) –Clinical manifestation Fever & abd pain, ± diarrhea –Mechanism: Cellular invasion

6 Mechanism - Toxin Production Preformed toxin –Food poisoning –Symptoms: nausea, vomiting, abdominal cramps, diarrhea –Onset: within 6 hours after consumption –Heat stable, mechanism not well-described –Examples: Bacillus cereus – GPR, can form spores –Classically reheated rice Staphylococcus aureus – GPC –Classically ham

7 Mechanism - Toxin Production Enterotoxin –Cause intestinal mucosa to secrete fluid –Symptoms: abdominal cramps, watery diarrhea which can be voluminous ( V.cholerae  rice-water diarrhea ) –Onset: >16 (up to 72) hours after consumption –Attachment, local elaboration & delivery of toxin Enterocytes – ↓ Na absorption and ↑ Cl secretion –Examples: Vibrio cholerae Enterotoxigenic E.coli (Traveller’s diarrhea)

8 Mechanism - Toxin Production Cytotoxin –Cause direct mucosal damage –Symptoms: abdominal cramps, bloody or mucoid diarrhea, tenesmus –Onset: >24 hours after consumption –Attachment, local elaboration & delivery of toxin Multiple mechanims of action  inflammation of GI mucosa –Examples: Enterohemorrhagic E.coli (O157:H7) Shigella Clostridium difficile

9 Mechanism – Cellular Invasion Enterocyte invasion –Intracellular replication –Can be complicated with extraintestinal infection –Characterized by neutrophilic inflammation: Incubation period 1-3 days Shigella, Campylobacter, Salmonella (non-typhoid) Listeria –Characterized by mononuclear inflammation: Incubation period 1-3 weeks Salmonella (typhoid)

10 Summary Non-inflammatory –Preformed toxin: Bacillus cereus, Staph aureus –Enterotoxin: Vibrio, ETEC –Non-bacterial causes: Viruses: Noroviruses, Rotoviruses Protozoa: Giardia, Cryptosporidium Inflammatory –Cytotoxin: C.diff, EHEC, Shigella –Invasive: Salmonella, Shigella, Campylobacter, Yersinia, Listeria Amebiasis Invasive ( Mononuclear inflammation ) –Classic: Salmonella, Brucella –Atypical: Mycobacteria, Histoplasma

11 Case 30 F presents with 3 day history of watery diarrhea with intermittent abdominal cramps. Previously healthy. Further questions?

12 Case 30 F presents with 3 day history of watery diarrhea with intermittent abdominal cramps. –Feels a little warm - ? subjective fever –No tenesmus, mucus, blood –No recent travel, sick contacts, pets –Ate a hamburger for lunch today, maybe a little pink in the center –Ate some left-over fried rice 10 days ago –Otherwise nothing undercooked/raw. No shellfish. –Notes almost 10 BMs/day, not getting better Does she need further evaluation?

13 Clinical Terminology Bacterial food poisoning –Preformed toxin Gastroenteritis –Noninflammatory versus inflammatory Enterocolitis –Inflammatory Dysentery –Inflammatory – invasive mechanism (neutrophilic) Enteric fever –Salmonella serotype Typhi or Paratyphi Mesenteric adenitis –Infection of mesenteric lymph nodes – typically due to Yersinia

14 Approach to Infectious Diarrhea Definition of diarrhea: –Increase in water content, volume, or frequency –Acute: ≤14d duration (viral, bacterial) –Persistent: >14d duration (protozoal, non-infectious) What do you need to know from patients: –Duration  acute or persistent Immunocompromised state renders duration unreliable –Symptoms  noninflammatory vs inflammatory –Exposures/travel  affects differential diagnosis –Sick contacts  attack rate –Recent antibiotic use  Clostridium difficile

15 Diagnostic Evaluation Indications: –Dehydration with signs of hypovolemia –Inflammatory diarrhea ( mucus, blood, tenesmus ) –Fever ≥ C –Severe diarrhea ( episodes ≥ 6/d or duration > 2d ) Requiring hospitalization –Severe abdominal pain –Elderly or immunocompromised –Recent antibiotic use –Systemic symptoms

16 Stool Studies –Fecal Leukocytes Sensitivity highly variable –Stool culture Detects: Salmonella, Shigella, Campylobacter Special media: Vibrio, Yersinia –EHEC/STEC immunoassay –Protozoa Giardia/Cryptosporidium immunoassay Entamoeba histolytica antigen[ SENDOUT ] –O&P Special stains required for Cyclospora/Isospora –Virus Norovirus PCR or EIA[ SENDOUT ] Rotavirus EIA[ SENDOUT ]

17 Diagnostic Evaluation Algorithm: AcutePersistent CommunityNosocomialImmuno- competent Immuno- compromised Stool cx +/- Fecal leuks +/- EHEC assay +/- C.diff assay C.diff assay Giardia Cryptosporidia O&P Fecal leuks Extensive

18 Foodborne Infections

19 Pathogenic Escherichia ETEC - Enterotoxigenic –Enterotoxin (similar to cholera toxin), elaborated locally –Non-inflammatory: watery diarrhea EAEC - Enteroaggregative –Adhere to intestinal mucosa and damage microvilli, ± enterotoxin –Variable from noninflammatory to inflammatory EHEC - Enterohemorrhagic / STEC –Cytotoxin (Shiga toxin), can cause hemolytic-uremic syndrome –Inflammatory: bloody diarrhea without fever EIEC - Enteroinvasive –Invasion  phagosome escape  multiply  actin driven spread –Dysentery: fever, abdominal pain, tenesmus, bloody or mucoid stool

20 STEC Shiga toxin-producing E.coli –O157:H7 most common serotype in U.S. –O104:H4 responsible for recent epidemic in Europe Shiga toxin –Receptor-mediated endocytosis  cytosol –Toxin interferes ribosome function  cell death –Enters bloodstream  damages endothelial cells  HUS Clinical disease –Only 5-15% develop HUS –Abd pain, diarrhea  bloody diarrhea after 1-4 days –HUS develops 5-13 days after diarrhea starts –Supportive therapy. Avoid/discontinue antibiotics.

21 E.coli O104:H /NEJMoa

22 STEC Lancet 2010; 376:1428

23 Salmonella - Disease Entities Salmonella enterica TyphoidalNon-typhoidal Typhoid Fever / Enteric FeverInflammatory gastroenteritis serotype Typhi serotype Paratyphi serotype Enteritidis serotype Typhimurium serotype Choleraesuis and many, many more… (2000+) Prolonged systemic infectionSelf-limited intestinal infection Human reservoirAnimal reservoir

24 Epidemiology - NT Salmonella OUTBREAKS 2007 Frozen Pot Pies n= Jalapeno peppers n= Peanut butter n= Eggs n= African frogs n=241 Ground turkey n=78 (8/4/11)

25 Epidemiology - Typhoid Clin Infect Dis 2005; 41:

26 Salmonella Typhoid / Enteric Fever Incubation = 1-3 weeks Clinical characteristics: Fever & abd pain Diarrhea or constipation Hepatosplenomegaly Rose spots Relative bradycardia Laboratory: Leukopenia, hepatitis Dx – blood, BM & stool cxs Complications: Intestinal perforation Neurologic disease Relapsing disease Gastroenteritis Incubation = 1-2 days Clinical characteristics: Diarrhea watery to dysentery-like lasting 3-7 days Variable fever lasting 2-3 days Abx not useful in uncomplicated dz Laboratory: Dx – stool cx Blood cx in immunocompromised Complications: Particularly in immunocompromised Bacteremia (5%) Metastatic infection Recurrent bacteremia

27 Shigella & Campylobacter Shigella –Human reservoir. Person-to-person spread. –Shiga toxin (cytotoxin)  E.coli O157:H7 (HUS) –Classic cause of “Bacillary dysentery” –Complications: Bacteremia, HUS, post-infectious reactive arthritis, acute GN Campylobacter –Animal (wild/domestic) reservoir. Commercial poultry. –Undercooked poultry most common culprit. –Complications: Bacteremia, post-infectious reactive arthritis, GBS

28 Vibrio Vibrio cholerae –Toxigenic (O1 & O139) – contaminated water / food Voluminous watery diarrhea, without fevers / abd pain –Non-toxigenic – shellfish, wounds Vibrio parahemolyticus –Consumption of raw/undercooked shellfish Diarrhea can range from watery to dysentery-like –Diarrhea > wound infection / septicemia Vibrio vulnificus –Consumption of raw/undercooked shellfish. Septicemia with secondary cellulitis in cirrhotics / iron overload –Wound infection with severe cellulitis / necrosis in healthy patients.

29 Acute Infectious Diarrhea Management Rehydration Symptomatic therapy –Anti-motility agent: NO/low-grade fevers, non-bloody stool –Bismuth subsalicylate Antibiotics indicated for: –Immunocompromised host –Severe diarrhea requiring hospitalization –Traveler’s diarrhea – severe (4+ BM/day) or inflammatory symptoms Decreased duration also seen in treatment of mild disease –Isolation of Shigella in stool culture Antibiotics not useful: –EHEC/STEC –Uncomplicated NT Salmonella in healthy host

30 Giardia intestinalis ( G.lamblia ) Surface water contaminated by human or animal source. Cysts survive well in cold water. Person-to-person transmission Infectious dose cysts Daycare centers MSM After treatment, can develop continued diarrhea due to lactose intolerance.

31 Entamoeba histolytica Cysts viable for weeks-months Worldwide distribution, in U.S. Recent immigrants International travel Intestinal disease: Asymptomatic – fulminant colitis Chronic disease confused w/ IBD Extraintestinal disease: Amebic liver abscess Pleuropulmonary amebiasis

32 Cryptosporidium Acquisition of Infection: Ingestion of oocysts Oocysts resistant to chlorination Infective when shed ( person  person ) Low infectious dose ( 10 oocysts ) Microbiology: Sporozoite Binds to intestinal epithelium and induces cell membrane to surround the sporozoite. Trophozoite  Merozoite ( motile ) Merozoite Asexual reproduction Sexual cycle  Gametocytes  Oocysts Cryptosporidium hominis – humans Cryptosporidium parvum Animals (cattle, sheep, pig, pets) & humans

33 Cyclospora Microbiology: –Life-cycle similar to Cryptosporidium: Ingestion of oocyst. Oocyst requires maturation period in warm environment. Invades small intestinal enterocytes – within cytoplasm. Epidemiology: –Distributed worldwide: Nepal, Latin America, Caribbean. –U.S. foodborne outbreaks: imported raspberries, basil, snowpeas, salad greens. Clinical Disease: –Watery diarrhea – cyclic / relapsing. Can last 2-7 weeks or longer. More persistent / severe in immunocompromised patients. Diagnosis: Oocysts require special staining (acid-fast) for detection in stool. Treatment: Trimethoprim-Sulfamethoxazole, Ciprofloxacin.

34 Isospora / Cystoisospora Microbiology: –Life-cycle similar to Cryptosporidium: Ingestion of oocyst. Oocyst infective when passed (person  person). Invades small intestinal enterocytes – within cytoplasm. Epidemiology: –Distributed in tropical / sub-tropical regions: Africa, South America, SE Asia –U.S. – immunocompromised, daycare centers, psychiatric institutions Clinical Disease: –Watery diarrhea. May have peripheral blood eosinophilia. Can last 2-3 weeks or longer. More persistent / severe in immunocompromised patients. Diagnosis: Oocysts require special staining (acid-fast) for detection in stool. Treatment: Trimethoprim-Sulfamethoxazole, Ciprofloxacin.

35 Cyclospora oocyst in stool - acid-fast stain Isospora oocyst in stool - acid-fast stain Isospora oocyst in enterocyte Cyclospora oocyst in stool – autofluoresce under UV microscopy

36 Clinical Cases 51M with low-grade fevers, NS, fatigue x3 wks. No changes in BMs. + Hepatosplenomegaly WBC 50 (87%L)  ALL ALT 500 Blood cultures on admit: Salmonella Reports recent travel to NYC, never outside U.S. No sick contacts, no pet reptiles, no unusual dietary habits or exposures. IV Ceftriaxone x2wks  splenic abscesses  aspirated  Salmonella

37 54 M presents with diarrhea x3 months. No fevers or abd pain. Admitted to OSH 6 weeks ago for chronic diarrhea, weight loss, nausea & vomiting. Found to have HIV / AIDS CD4 count of 70, candidal esophagitis. Cause of diarrhea not determined. Subsequently admitted to BGSMC x3 for chronic diarrhea over 1 month period. Watery, non-bloody. CBC: WBC 4.9 ( 50%N, 25%L, 15%E )

38 50 F with EtOH cirrhosis presents with acute onset of chills, abdominal pain, N/V/D for 1 day. Recently attended a party, where she consumed shrimp cocktail, pizza, and chips. 24h later developed chills, abdominal cramps, and diarrhea - loose, non-bloody, low volume. Next morning was found to be lethargic, confused, and with slurred speech by her husband. Brought to OSH  septic shock. She was intubated, and started on vasopressors and empiric abx. Transferred to BGSMC for higher level of care. SH: pet python, parakeet, fish, dog. LABS: WBC % B, ascites 1399 WBC 70%N

39 Blood Cx Gram Stain


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