Infectious Diarrhea & Dysentery 2024/2025 PDF

Tropical Medicine Department Infectious diarrhea & dysentery 2024/2025 1  Know different infectious agents causing diarrhea. Know mode of transmission of different organisms. Determine the pathogenesis and pathology involved in each case. Describ...

Tropical Medicine Department Infectious diarrhea & dysentery 2024/2025 1  Know different infectious agents causing diarrhea. Know mode of transmission of different organisms. Determine the pathogenesis and pathology involved in each case. Describe different clinical presentation. Realize possible complications. Realize the diagnostic methods of each condition. Describe the proper treatment. Realize different DD of the case. 2 42 year old male patient presented with severe diarrhea, of 3 days duration associated with abdominal cramps and fever of 38.7 °C. There are mucous and blood in his stool. He sought medical advice and the physician told him that he has gastroenteritis and gave him antibiotic for 1 week. After which the patient was not improved. He returned to his physician who asked him for some investigations. Extended Modular Program 3  Definitions Diarrhea can be defined by increased stool frequency, liquidity, or volume. Health care professionals typically think of diarrhea as an increase in stool frequency; however, for most individuals, the essential characteristic of diarrhea is the passage of loose stools. 1 Types of diarrhea according to onset, course, duration Acute diarrhea Chronic diarrhea  Treatment of Acute Diarrhea Diet Rehydaration (oral, parentral) Antidiarrheal agents (Opioids, Bismth subsalicylate) Antibiotic therapy…..Empiric Abs of all patients with acute diarrhea is not indicated Indications: Patients with non–hospital-acquired diarrhea moderate to severe fever, tenesmus, bloody stools or the presence of fecal lactoferrin immunocompromisation significant dehydration. while the stool bacterial culture is incubating [Fluroquinolones, TMP-SMX, Doxycycline, Rifaximine]. Specific: The infectious diarrheas for which treatment is recommended are shigellosis, cholera, extraintestinal salmonellosis, traveler’s diarrhea, C difficile infection, giardiasis, and amebiasis.  The two broad etiological categories of diarrhea are infectious and noninfectious. Infectious diarrhea can be divided into: Bacterial: Campylobacter jejuni ,E.coli, Shigella,Salmonella,cholera vibrio ,vibrio parahemolyticus etc. Viral: Rota virus, adenovirus ,enterovirus ,norwalk group viruses ,measles virus etc Parasitic: E.histolytica, G.lambia, Cryptosporidium,H.nana , malaria etc. Extended Modular Program 7  Shigellosis Shigella is transmitted from an infected person to another usually by a fecal-oral route. Shigella are present in the diarrheal stools of infected persons while they are ill and for a week or two afterwards. Shigella infections can be acquired by drinking or swimming in contaminated water. 8 Extended Modular Program 9 ❑The characteristic pathology is an acute, locally invasive colitis, ranging from mild to severe inflammation of distal colonic mucosa. ❑The pathological process may extend to involve submucosa and muscle layers. Bacteraemia is uncommon finding in Shigellosis. Extended Modular Program 10 Clinical picture: People infected with Shigella develop diarrhea with mucus and blood in stool, fever and abdominal cramps starting 1-5 days after they are exposed to the bacterium. The diarrhea is often bloody, may be as many as 30 times per day. Shigellosis usually resolves in 5 to 7 days, but in some persons, especially those with extreme ages, hospitalization may be indicated. Some infected patients may manifest no symptoms. Extended Modular Program 11 Complications: Intestinal complications include toxic megacolon, perforation, and a protein-losing enteropathy. Electrolytes disturbances especially prolonged hyponatremia and convulsions may occur. Extra-intestinal complications include Hemolytic uremic syndrome (HUS) and Reiter's syndrome. Extended Modular Program 12 Diagnosis: Determining that Shigella is the cause of the illness depends on laboratory tests that identify the bacteria in the stool of an infected person. Antimicrobial sensitivity should also be determined. Treatment: ❑Rehydration, electrolytes therapy and maintaining adequate level of nutrition are essential in management. ❑Shigellosis can usually be treated with antibiotics. The antibiotics commonly used are ampicillin, trimethoprim/sulfamethoxazole, nalidixic acid and fluoroquinolones. Extended Modular Program 13  Escherichia coli E. coli consists of a diverse group of bacteria. Pathogenic E. coli strains are categorized into pathotypes. Six pathotypes are associated with diarrhea and collectively are referred to as diarrheagenic E. coli. Extended Modular Program 14 1- Shiga toxin-producing E. coli (STEC)—STEC may also be referred to as Verocytotoxin-producing E. coli (VTEC) or enterohemorrhagic E. coli (EHEC). This pathotype is the one most commonly heard about in the news in association with foodborne outbreaks. 2- Enterotoxigenic E coli (ETEC) 3- Enteropathogenic E. coli (EPEC) 4- Enteroaggregative E. coli (EAEC) 5- Enteroinvasive E. coli (EIEC) 6- Diffusely adherent E. coli (DAEC) 15 Shiga toxin-producing E. coli (STEC): The most commonly identified STEC in North America is E. coli O157:H7 (often shortened to E. coli O157 or even just “O157”). When you hear news reports about outbreaks of “E. coli” infections, they are usually talking about E. coli O157. In addition to E. coli O157, many other kinds (called serogroups) of STEC cause disease. Other E. coli serogroups in the STEC group, including E. coli O145, are sometimes called “non-O157 STECs.” 16 The symptoms of STEC infections vary for each person but often include severe stomach cramps, diarrhea (often bloody), and vomiting. If there is fever, it usually is not very high (less than 38.5˚C). Most people get better within 5–7 days. Some infections are very mild, but others are severe or even life-threatening. 17  Non-specific supportive therapy, including hydration, is important. Antibiotics should not be used to treat this infection. There is no evidence that treatment with antibiotics is helpful, and taking antibiotics may increase the risk of HUS. Antidiarrheal agents like Imodium may also increase that risk. 18 Enterotoxigenic E. coli (ETEC) ❑ETEC is an important cause of diarrhea in infants and travelers in developing countries. ❑The diseases vary from minor discomfort to a severe cholera- like syndrome. ❑ ETEC are acquired through faecal-oral route by ingestion of contaminated food and water. Extended Modular Program 19 Clinical picture: Incubation period is 1-2 days, with anorexia, vomiting and abdominal cramps and voluminous watery diarrhea up to 10 times a day. The disease lasts for about 5 days but may extend to 3 weeks. Diagnosis: In developing countries, the diagnosis of E.coli infection is rarely done outside research studies. Diagnosis depends on culture of E.coli in faeces or detection of pathogenicity genes by PCR. Extended Modular Program 20 Treatment: 1- Fluid and electrolytes replacement are the main stay in treatment. 2- Antibiotics shorten the duration of illness, currently the antibiotics of choice include fluoroquinolones and azithromycin. Prevention: 1. An oral ETEC vaccine has been shown to be safe, immunogenic against severe diarrhea in American travelers. 2. Another modified vaccine has been developed and being tested. 3. Improving sanitary conditions is the corner stone for prevention. Extended Modular Program 21  Cholera Cholera continues to be a major public health threat, particularly in countries where clean drinking water, adequate sanitation and hygiene are not optimal. Extended Modular Program 22 Route of transmission: V. cholera is transmitted through faecal-oral route by ingestion, through contaminated water or food. Incubation period ranges between few hours to 5 days. Extended Modular Program 23 Clinical presentation: It ranges from mild diarrhea to severe dehydration with death occurring within hours, asymptomatic cases may occur. 1. Profuse watery diarrhea is a hallmark of cholera. Vomiting, although a prominent manifestation, may not always be present. 2. Electrolytes disturbances and hypoglycemia could occur. 3. Hypotension and hypovolemia lead to impaired consciousness and renal failure. In patients with severe disease, vascular collapse, shock, and death may ensue. Extended Modular Program 24 Diagnosis: In epidemics, the diagnosis of cholera may be made presumptively on clinical and epidemiological grounds. Laboratory diagnosis may be required when sporadic cases occur. Dark-field microscopy of faecal specimens may show the characteristic movement of the vibrios. Extended Modular Program 25 1. For confirmation, culture on selective media may be needed (e.g: thiosulphate citrate bile salt sucrose (TCBS) agar. 2. Polymerase chain reaction (PCR) tests for identifying V cholerae have been developed. 3. Hematocrit, serum-specific gravity, and serum protein are elevated in dehydrated patients because of resulting hemoconcentration. Extended Modular Program 26 Treatment: 1. It involves the rapid intravenous replacement of the lost fluid and ions. Following this replacement, administration of isotonic maintenance solution should continue until the diarrhea ceases. 2. Most antibiotics and chemotherapeutic agents have no value in cholera therapy, although a few (e.g. tetracyclines and doxycycline) may shorten the duration of diarrhea and reduce fluid loss. Co-trimoxazole and furazolidone can be used. Extended Modular Program 27  Clostridium difficile Clostridium difficile (from Latin difficile, "difficult, obstinate"). It is a species of Gram-positive spore-forming bacteria. While it can be a minor part of normal colonic flora, the bacterium is thought to cause disease when competing bacteria in the gut have been reduced by antibiotic treatment. Extended Modular Program 28 Epidemiology: ❑The bacterium can be found worldwide but its role as a cause of diarrheal disease in developing countries is probably underestimated. ❑Of all patients treated for CDI, 20% relapse and 65%of those experiencing a second relapse become chronic cases. Extended Modular Program 29 Transmission: Clostridium difficile are shed in feces, and therefore these bacteria can be transmitted via the fecal-oral route. The spores can survive on almost any surface for months to years which makes the pathogen very difficult to get rid of once established. Extended Modular Program 30 Risk factors: Those most at risk are people, especially older adults, who take antibiotics and also get medical care. 1. Antibiotics: C. difficile-associated diarrhea (CDAD) is most strongly associated with fluoroquinolones, cephalosporins, carbapenems, and clindamycin. Antibiotics especially those with a broad activity spectrum (such as clindamycin) disrupt normal intestinal flora. This can lead to an overgrowth of C. difficile, which flourishes under these conditions. 2. Healthcare environment 3. Acid suppression medication: Increasing rates of community-acquired C. difficile infection is associatedExtended with the use of medication to suppress gastric acid Modular Program production. 31 Clinical picture: Symptoms range from mild diarrhea to severe life-threatening colitis. In adults, a clinical prediction rule found the best signs to be: significant diarrhea ("new onset of more than three partially formed or watery stools per 24-hour period"), recent antibiotic exposure, abdominal pain, fever and a distinctive foul stool odour. Extended Modular Program 32 Laboratory diagnosis: 1- Polymerase chain reaction. This sensitive molecular test can rapidly detect the C. difficile toxin B gene in a stool sample and is highly accurate. 2- GDH/EIA. Some hospitals use a glutamate dehydrogenase (GDH) test in conjunction with an enzyme immunoassay (EIA) test. GDH is a very sensitive assay and can accurately rule out the presence of C. difficile in stool samples. Extended Modular Program 33 3- Enzyme immunoassay. The enzyme immunoassay (EIA) test is faster than other tests but isn't sensitive enough to detect many infections and has a higher rate of falsely normal results. 4- Cell cytotoxicity assay. A cytotoxicity test looks for the effects of the C. difficile toxin on human cells grown in a culture. This type of test is sensitive, but it is less widely available, requires 24 to 48 hours for test results. It's typically used in research settings. 5- Stool leukocyte measurements and stool lactoferrin levels have also been proposed as diagnostic tests, but may have limited diagnostic accuracy. 6- others: as colonscopy and imaging. Extended Modular Program 34 Treatment: Carrying C. difficile without symptoms is common. Treatment in those without symptoms is controversial. In general, mild cases do not require specific treatment. Oral rehydration therapy is useful in treating dehydration associated with the diarrhea. (1) Medications: A number of different antibiotics are used for C. difficile with the available agents being more or less equally effective. Vancomycin is the first line of treatment. Metronidazole is alternative if vancomycin is not available. Extended Modular Program 35  There is insuffiient evidence to support the use of probiotics Surgery: In those with severe C. difficile colitis, colectomy may improve the outcomes. Extended Modular Program 36 Protozoal diarrhea: e.g Amebiasis and Giardiasis. Viral diarrhea: e.g Rota virus and HIV. Extended Modular Program 37 ❑Viral diarrhea frequently presents as watery, noninvasive diarrhea of acute onset, often associated with nonspecific systemic symptoms such as low-grade fever, headache, myalgia, and incidence during the winter months. ❑In immunocompetent adults, symptoms are usually self-limited, lasting less than 48 hours, but they may persist for longer than 1 week. ❑Prolonged and severe illness occurs more often in young children, the elderly, and hospitalized or immunodeficient patients. Extended Modular Program 38  Rotavirus ✓Rotavirus is the leading cause of life-threatening diarrheal diseases among young children. ✓Research over the past several years has provided important insights into mechanism of viral pathogenesis and led to successful development of live, attenuated vaccines for gastroenteritis. ✓Rotavirus primarily infects small intestinal villous cells and can cause watery diarrhea without any significant intestinal inflammation. Extended Modular Program 39  Amoebiasis Amoebiasis is a disease caused by the protozoan Entamoeba histolytica. The disease is distributed worldwide, but is a leading cause of morbidity & mortality in the tropics. E.histolytica inhabits the large intestine of the human host. Mode of infection: ingestion of water or uncooked food contaminated by human feces containing E.histolytica cysts (also through anal/oral sexual practices)  1 4 2 Reminder of the life 3c cycle of E.histolytica Notes: - Only cysts are infective 3b to humans (Trophozoites are not infective since they’re disintegrated by gastric juice) - Autoinfection is possible from contaminated hands 3a  Clinical Picture Incubation period: 2-4 weeks (may take years) Most of infected individuals are ‘asymptomatic cyst passers’ which act a reservoir for transmitting amoebiasis Acute presentations: amoebic dysentery (which may overlap with bacillary dysentery or ulcerative colitis) or diarrhea alternating with constipation Diagnosis: a) Lab: ▪ Stool antigen detection ▪ Microscopic stool examination (for trophozoites containing RBCs) ▪ PCR ▪ Serologic test by immunofluorescence (only 60% of dysenteric amoebiasis) b) Invasive: ▪ Sigmoidoscopy (for flask shaped ulcers) Treatment Tissue amoebicides: (5-10 days) Metronidazole/Tinidazole/Ornidazole Nitazoxanide Luminal amoebicides: (10 days) Diloxanide furoate or Paromomycin → should follow tissue amoebicidal treatment. Prevention: Avoid eating uncooked vegetables or unclean water  Giardiasis Giardiasis is a disease caused by the protozoan Giardia lambia. The disease is distributed worldwide, being common in the tropics. G.lambia inhabits the small intestine (dueodenum & jejunum) of the human host. Mode of infection: mainly by ingestion of unclean water containing G.lambia cysts (uncooked food is another source ) Population at risk: children, immunocompromised individuals & tourists Reminder of the life cycle of G.lambia Notes: - Cysts pass in non-diarrheal stool - With diarrhea, short transit time in the colon yields trophozoites in stool  Clinical Picture Incubation period: 1-3 weeks Presentation may be acute; with diarrhea, abdominal pain, weakness, anorexia, nausea & vomiting Chronic form of Giardiasis presents by: chronic diarrhoea and malabsorption, with bulky greasy stools that float. Diagnosis: a) Lab: ▪ Microscopic stool examination (for cysts) ▪ String test ▪ Stool antigen detection ▪ PCR b) Invasive: ▪ Duodenal or jejunal aspirates by endoscopy ▪ Jejunal biopsy  String Test (Entero-test) a gelatin capsule containing a nylon string with a weight attached to it; patient tapes one end of the string to his or her cheek and swallows the capsule after the gelatin dissolves in the stomach, the weight carries the string into the duodenum the string is left in place for 4-6 hours or overnight while the patient is fasting after removal, it is examined for bilious staining, which indicates successful passage into the duodenum. mucus from the string is examined for trophozoites in an iodine or saline wet mount or after fixation and staining. Treatment Single dose of tinidazole OR Metronidazole for 10 days OR Nitazoxanide for 3 days.  summary Diarrhea can be defined by increased stool frequency, liquidity, or volume. Diarrhea is objectively defined as passing a stool weight or volume Greater than 200 g or 200 mL per 24 hours. The two broad etiological categories of diarrhea are infectious (bacterial-viral- parasitic) and noninfectious. The infectious diarrheas for which treatment is recommended are shigellosis, cholera, extraintestinal salmonellosis, traveler’s diarrhea, C difficile infection, giardiasis, and amebiasis. Extended Modular Program 51  MCQs The gold standard for diagnosis of giardiasis: a) Stool examination T (because it allows detection of Giardia cyst and occasionally trophozoites in stool). b) stool-based PCR F. (because it is emerging diagnostic test for Giardia). c) Direct fluorescent antibody testing F. (because stool examination is more accurate). d) Complete blood count Extended Modular Program 52 Regarding Clostridium difficile: a) It is a species of Gram-negative spore-forming bacteria. F (because it is Gram- positive). b) It commonly causes to toxic megacolon F (because it in rare cases can progress to toxic megacolon). c) It can be a minor part of normal colonic flora T (because the bacterium is thought to cause disease when competing bacteria in the gut have been reduced by antibiotic treatment). d) These bacteria can be transmitted via the fecal-oral route. T (because Clostridium difficile are shed in feces) Extended Modular Program 53 Clinical symptoms of shigellosis: a) People infected with Shigella infection develop diarrhea with mucus and blood in stool T b) Patients may present with abdominal cramps and voluminous watery diarrhea. F (because E. coli produces cholera like toxin). c) Incubation period is may extend to weeks. F (because incubation period is 1-5 days) d) The diarrhea is often severe and bloody T (because it may be as many as 30 times per day). Extended Modular Program 54 Regarding stool microscopy diagnosis in amebic colitis: a) Microscopic examination of fresh stool smears rarely show trophozoites b) Stool examination findings in patients with amebic liver abscess are usually positive. c) Stool leukocytes are numerous d) examination of 3 stool samples can improve the detection rate False as excystation occur in colon resulting in presence of trophozoites in fresh stool smear. False because stool examination findings in patients with amebic liver abscess are usually negative. False because stool leukocytes are few in amebic colitis. True as examination of a single stool sample has a sensitivity of only 33-50%; however, examination of 3 stool samples over no more than 10 days can improve the detection rate to 85-95%. Extended Modular Program 55  References https://wwwnc.cdc.gov/travel/yellowbook/2024/preparing/tr avelers-diarrhea https://www.who.int/news-room/fact- sheets/detail/diarrhoeal-disease Extended Modular Program 56 Extended Modular Program 57