2-Diarrheal Diseases-2024.pptx

Infectious Disease and Rural Medicine Module (ID&RM) Module: ID&RM Module code: Course: Medical Microbiology Topic/Session: Diarrheal diseases Student category: Preclerkship-II medical students Instructor: Tesfaye K (PhD)  Diarrheal disease What is Diarrhea? – Diarrhea is loose...

Infectious Disease and Rural Medicine Module (ID&RM) Module: ID&RM Module code: Course: Medical Microbiology Topic/Session: Diarrheal diseases Student category: Preclerkship-II medical students Instructor: Tesfaye K (PhD)  Diarrheal disease What is Diarrhea? – Diarrhea is loose, watery stools. Having diarrhea means passing loose stools three or more times a day. – Measured stool volume greater than 10ml/kg/day, including changed consistency of stool (loose or watery) and frequency (≥3 episodes within 24Hr) – Passage of abnormally liquid or unformed stools at an increased frequency. For adults on a typical diet, stool weight >200 g/d can generally be considered diarrheal. 2  Diarrheal disease… (2) Key facts Diarrheal disease is the second leading cause of death in children < 5 years old. It is both preventable and treatable. Each year diarrhea kills around 525,000 children under five. (Africa Health Organization) A significant proportion of diarrheal disease can be prevented through safe drinking-water and adequate sanitation & hygiene. Globally, there are nearly 1.7 billion cases of childhood diarrheal disease every year. Diarrhea is a leading cause of malnutrition in children < 5 yrs old. 3  Diarrheal disease… (3) Diarrhea is usually a symptom of an infection in the intestinal tract – can be caused by a variety of organisms (bacterial, viral & parasitic). Infection is spread through – contaminated food or drinking-water, or – from person-to-person as a result of poor hygiene. Interventions to prevent diarrhea, including – safe drinking-water, – use of improved sanitation and – hand washing with soap can reduce disease risk. 4  Diarrheal disease… (4) There are three clinical types of diarrhea: Acute diarrhea: The most common. Acute diarrhea is loose watery diarrhea that lasts one to two days. This type doesn’t need treatment and it usually goes away after a few days. – Acute bloody diarrhea – also called dysentery; and – Acute watery diarrhea – lasts several hours or days and includes cholera. Persistent diarrhea: This type of diarrhea generally persists for several weeks – two to four weeks Chronic diarrhea: Diarrhea that lasts for more 5  Pathogenesis/ Pathophysiology Flow in the GI tract involve massive fluid secretion into and absorption from the GI lumen Subtle abnormalities in input or output at any levels can result in diarrhea – Thus, an excessive osmotic load, increased secretion, or diminished fluid resorption may result in diarrhea The causes of diarrhea include inflammatory, osmotic, secretory, motility,6  Common Causes of Diarrheal Diseases/food poisoning Bacterial Non- bacterial  Staphylococcus aureus causes  Vibrio cholerae – Viruses Rotavirus  Shigella spp. Norovirus  Escherichia coli, Adenovirus  Salmonella spp. Hepatitis A  Campylobacter jejuni  Bacillus cereus  Clostridium – Parasites (protozoa/helminths) botulinum Giardia lamblia Other such as chemicals  Yersinia enterocolitica Entamoeba histolytica 7  Invasive Diarrhea By bacterial invasion of the bowel mucosal surface Organisms involved – Salmonella spp. – Campylobacter spp. – Shigella spp. (e.g. Sh. dysenteriae) – E. coli – Vibrio spp. 8 Salmonella species  Contracted by eating undercooked meat, poultry, eggs, and contaminated dairy products  Nausea, vomiting, and diarrhea 6-48 hours after ingestion  Usually self-limiting  Requires a high microbial load for infection  Symptoms last 4-7 days without treatment.  Salmonella is killed by cooking and pasteurization,  But it can contaminate the food processing area and transmitted to another food item. 9 Be curious about 10 Enteric Fever Typhoid fever is most severe Contaminated food and water Organisms invade small bowel & colonic tissue Live and reproduce in monocytes Can invade gall bladder and produce “carrier state” Symptoms include headache, fever, malaise and abdominal tenderness 11 Lab. Dx Fecal WBC lab test – Observe for RBC’s and WBC’s in stool Culture – Look for blue green colonies with black centers on Hektoen Enteric agar – Look for red colonies with black centers on XLD Antibody detection is generally of little value 12 Campylobacter jejuni – Most common cause of bacterial diarrhea in the world Grows best at 42°C in microaerophilic conditions Likes capnophilic conditions – Found in inadequately cooked poultry, untreated water, unpasteurized milk, and exposure to animals with diarrhea – Self-limiting, antibiotics not needed – Manifests with fever, diarrhea and abdominal cramping 13 Gram-negative curved rods, “seagull wings”. Campylobacters stain faintly and can be difficult to visualize. – could be cultured 14 Shigella species – Gram-negative, facultatively anaerobic rods – Most communicable of the diarrheal bacteria – Requires a low microbial load – Symptoms include: fever, malaise, fatigue & anorexia – Symptoms appear 12-50 hrs after exposure – Diarrhea may have blood and pus 15 Fecal WBC lab test Observe blood, WBCs, pus Culture Colorless colonies on MAC Blue green colonies of HE Red/colorless on XLD 16 Escherichia coli  Gram-negative, facultative anaerobic rods  At least five different pathogenic groups cause gastroenteritis –ETEC: Enterotoxigenic - Cause of traveler’s diarrhea – EIEC: Enteroinvasive – Bacteria dysentery – EPEC: Enteropathogenic -Diarrhea outbreaks in infants in hospital setting – EHEC: Enterohemorrhagic -Presence of Shiga-like toxin –EAEC: Enteroaggregative -Chronic diarrhea in HIV patients, travelers, & children in poor countries 17 Organisms grow rapidly on most culture media Specific pathogenic strains, such as E. coli O157:H7 are grown on MacConkey agar (Left) as well as on sorbitol MAC (right) Agar 18 Enterotoxin-Mediated Diarrhea Many cases of food poisoning caused by toxins produced by bacteria – Bacteria may no longer be alive, but toxins can cause food poisoning – Example: S. aureus Clostridium botulinum Bacillus cereus Vibrio cholerae Enterotoxigenic E.coli 19 Staphylococcus aureus It is commonly found on the skin, hair, noses and throats of people and animals. It can multiply quickly at room temperature and produce a toxin that causes Food poisoning Source – Salads, macaroni, – Bakery products, – Cream pies, milk and dairy products, 20  Coagulase and catalase positive, mannitol fermenter Detection of staphylococcal exotoxin may be possible from leftover foods or vomitus Antibody detection is generally of little value 21 Clostridium perfringens  part of the normal flora of vagina & GIT  produces multiple toxins, including alpha toxin that causes lysis of endothelial and blood cells.  Generates spores in improperly cooked foods  Enterotoxin disrupts ion transport in lower portion of small intestine  Causes loss of fluid in intracellular protein 22 Large rectangular Double zone of Gram-positive hemolysis bacilli 23 Bacillus cereus Gram positive rods which are spore-forming – Also acquired by penetrating injuries and intravenous injections It is type of bacteria that produces toxins (diarrheal toxin, emetic toxin) Incubation Period 1-6 hours Source Soil, and in raw, dried and processed foods Lab Diagnosis Produces haemolytic colonies on blood agar 24  Vibrio species  V. cholerae, V. vulnificus, V. parahaemolyticus, etc.  Gram-negative rods, highly motile, facultative anaerobes, with one to three flagella at one end.  Associated with raw or undercooked seafood harvested from contaminated water  Infects the small intestine  Enterotoxin activates adenylate cyclase which initiates an outpouring of fluid into the intestine  Watery diarrhea (rice water stools) evident 25 Lab Diagnosis Utilize TCBS media (Thiosulphate Citrate Bile Salt Agar) - yellow and profuse colonies Inhibits colonic flora Differentiates sucrose fermenters from species of Vibrio that are non- fermenters Stool contains no RBC’s or WBC’s since it is toxin mediated & non- inflammatory 26  Viral Agents Rotavirus – Primarily affects children < 5 years old – Spread by fecal-oral route – Peak incidence from December through June Calicivirus : Norovirus Spread by fecal-oral route by contaminated food or water or environmental fomites, person to person Outbreaks on cruise ships Cause of stomach flu Hard to diagnosis due to the minute virus size Require secondary testing such as cell culture, PCR, EM 27 28 Parasitic Infections Giardia lamblia By ingestion of contaminated water or person-person spread Only lives in the host In chronic infection protracted diarrhea results in malabsorption syndrome (inability to absorb disaccharides) Symptoms include nausea, vomiting, flatulence, cramping and diarrhea Absence of fever and fecal leukocytes 29 30 Entamoeba histolytica - It exists in cyst and trophozoite form - It’s transmitted by feco-oral with food, water or hand Symptoms Abdominal discomfort intense pain in right side => Dysentery 31 Diagnosis – Stool Sample – Direct saline wet mount microscopy – Trichrome Stain (for trophozoites) – Biopsy – Histologically, villi appear flattened – Fluorescent Antibody Tests 32 Risk Factors in general Number of Ingested Organisms Median infectious dose (ID50) The number of ingested organisms that must be ingested to cause a diarrheal illness in 50% of exposed individuals Achlorhydria: Inadequate stomach acidity Reduction in normal flora: use of antibiotics Age, improper food handling, persona 33  Laboratory Dx of Gastrointestinal Pathogens Specimen Collection and Handling  Collect within 4 days of onset of symptoms  Stool should be processed ASAP; NOT refrigerated  Rectal swabs NOT recommended  Use of preservatives not recommended 34 – Fecal Leukocytes Direct microscopic exam almost exclusively performed to detect presence of WBCs and RBCs. Their presence is due to intestinal wall bleeding Differentiates invasive disease from toxin-mediated illnesses, viral illness and parasitic infections – WBC become +ve: Salmonella, Shigella, Yersinia, EIEC, Campylobacter, Vibrio, … Routine stool cultures include testing for: Salmonella species, Shigella species, and Campylobacter jejuni N.B. Enrichment, Selective & Differential media 35  N. Saline mount A drop of methylene blue with diarrheal stool 36 37  Treatment of Diarrhea Patients must be watched for dehydration Antibiotics are NOT effective against viral pathogens, give supportive care for hydration Antibiotics may shorten illness due to invasive bacteria or an enterotoxin-mediated process Antidiarrheal medications work by decreasing bowel motility or the acid (Lomotil, Pepto-Bismol) - Primarily used with enterotoxin mediated diarrhea or viral gastroenteritis Prophylactic therapy not recommended for travelers When traveling, “Boil it, peel it, cook it, or forget it”! Do not eat solid food while nauseous/vomiting but drink plenty of fluids. 38 Antibiotics Eg. Fluoroquinolones (e.g., Prevention Key measures to prevent diarrhea include: – access to safe drinking-water; – use of improved sanitation; – hand washing with soap; – exclusive breastfeeding for the first 6 months of life; – good personal and food hygiene; – health education about how infections spread; and – rotavirus vaccination. In Ethiopia, upto 80% of health problems are due to communicable diseases attributable to unsafe water supply, unhygienic and unsanitary waste disposal. https://www.unicef.org/ethiopia/every-child-clean-water 39  Any question? 40