Presentation on theme: "Infectious Diarrhea. Learning Objectives Microbiology –Recognize common and atypical pathogens Pathogenesis –Understand general mechanisms of infection."— Presentation transcript:
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
Case 30 F presents with 3 day history of watery diarrhea with intermittent abdominal cramps. Previously healthy. Further questions?
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?
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
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
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
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
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.
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
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
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.
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
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.
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
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
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.
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.
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
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
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 )
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