Vibrio, Campylobacter, and Helicobacter PDF

VIBRIO, CAMPYLOBACTER AND HELICOBACTER INTRODUCTION ▪ Group of curved Gram-negative rods/bacilli ▪ Vibrio cholerae, the cause of cholera, one of the first proven infectious diseases. ▪ Campylobacter jejuni is one of the most common causes of diarrhea in virtually every country of the wor...

VIBRIO, CAMPYLOBACTER AND HELICOBACTER INTRODUCTION ▪ Group of curved Gram-negative rods/bacilli ▪ Vibrio cholerae, the cause of cholera, one of the first proven infectious diseases. ▪ Campylobacter jejuni is one of the most common causes of diarrhea in virtually every country of the world. ▪ Helicobacter pylori known to cause peptic ulcers and some other gastric pathologies. VIBRIO ▪ Gram-negative curved rods (comma shaped) ▪ Vibrio cells may be linked end to end, forming S shapes and spirals. ▪ Highly motile with a single polar flagellum and oxidase-positive Sheathed single polar flagellum ▪ They can grow under aerobic or anaerobic conditions. ▪ Vibrios are commonly found in saltwater. ▪ Vibrio cholerae is the cause of water-loss diarrhea called cholera. ▪ Other species cause diarrhea, wound infections, and, rarely, systemic infection VIBRIO Vibrio cholerae BACTERIOLOGY ▪ It produces the Cholera toxin whereas the other species don’t ▪ Possess long filamentous pili that form bundles on the bacterial surface ▪ It has a different lipopolysaccharide 0 antigenic structure different from the other Vibrios ▪ Over 200 serotypes based on the lipopolysaccharide O antigen ▪ Serotype O1 and O139 cause cholera ▪ Have low tolerance to acid but can grow in alkaline conditions. ▪ O139 serotypes produce polysaccharide capsule. ▪ Biofilm produced in environment aids in adhesion/attachment ▪ Biochemical or agglutination reactions can be used to distinguish from other Vibrios. BACTERIOLOGICAL MEDIA ▪ Transport media (keeps the bacteria viable for several weeks without multiplication) ▪ Bile peptone transport medium ▪ Cary blair medium ▪ Enrichment media ▪ Alkaline peptone water ▪ Plating/culture media ▪ Alkaline bile salt agar medium (a modified nutrient agar) ▪ Thiosulphate citrate bile sucrose agar medium (TCBS) ▪ In this media large colonies will be formed in yellow colour (24 hours) ▪ Old colonies turn green CHOLERA TOXIN ▪ Cholera toxin (CT) is a polypeptide containing 2 toxic subunits (A1, A2) and 5 binding units (B) ▪ Causes active secretion of (Na+), (Cl--),(K+), (HCO3 --) & H2O out of the cell into the intestinal lumen. ▪ The massive loss of these electrolytes result in metabolic acidosis, shock, muscle cramps, anuria sometimes death ▪ This results in the hypersecretion of glands in the intestine hence large amounts of intestinal fluids in the lumen ▪ Toxin also increases the capillary permeability resulting in edema EPIDEMIOLOGY Transmitted through water/food contaminated by feces from an infected person. Cholera is likely found and spread in places with: Inadequate water treatment/Poor sanitation/Inadequate hygiene. Brackish and marine waters are the natural environment for the etiologic agents of cholera, Vibrio cholerae serogroup O1 or O139. There are no known animal hosts for Vibrio cholerae, however, the bacteria attach themselves easily to the chitin-containing shells of crabs, shrimps, and other shellfish, which can be a source for human infections when eaten raw or undercooked. Cholera is endemic in India and Africa People who are also likely to be exposed to cholera include healthcare personnel treating cholera patients, cholera response workers, and travelers in an area of active cholera transmission who cannot or do not always follow safe food and water precautions and personal hygiene measures. An estimated 1.3- 4.0 million cases and 21,000-143,000 deaths occur each year around the world (WHO 2019). https://www.afro.who.int/health-topics/cholera/outbreak/21-july-2017-kenya PATHOGENESIS Ingestion of large numbers of bacteria is required (106 to 1011) Incubation period ranges from a few hours to 5 days Ingested bacteria reach the stomach the small intestines start multiplying V. cholerae swim to the small intestines through chemotactic motility V. cholerae swim to the small intestines then adhere to the epithelial surface mediated by Pili and proteins Virulent strains of V. cholerae produce CT after multiplication in the small intestine CT-stimulated intestinal hyper secretion causes diarrhea The outpouring of fluid and electrolytes is greatest in the small intestine The secretory capacity is high and absorptive capacity low. Stools are rice water, containing mucus, large number of vibrios and epithelial cells. CLINICAL MANIFESTATION Cholera infection can be mild or without symptoms but can sometimes be severe. Severe disease characterized by profuse watery diarrhea, vomiting, and leg cramps. Rapid onset of extreme watery diarrhea starts with abdominal fullness and discomfort, rushes of peristalsis, and loose stools. Non-O1, non-O139 strains can cause gastroenteritis but not the disease cholera. The diarrheal fluid can amount to many liters per day) 1 litre per hour Has approximately the same NaCl content as plasma K+ and bicarbonate losses cause hypokalemia and acidosis V. cholerae does not invade or otherwise injure the enterocyte. It can lead to extreme dehydration, hypotension, shock, and death within hours if untreated. Stools quickly become watery, voluminous, almost odorless, and contain mucus flecks, giving it an appearance called rice-water stools. The disease may last 4-5 days Typical clinical features in Cholera aid clinical diagnosis Visible symptoms include: Sunken eyes and cheeks Decreased skin suppleness Dry mucous membranes Urine production is sharply decreased or stopped altogether Renal failure is the most common. BACTERIOLOGICAL DIAGNOSIS ▪ Stool specimen or rectal swab are collected for bacteriological diagnosis. ▪ Microscopic examination – Gram- negative comma shaped bacilli ▪ Culture – TCBS or Alkaline bile salt agar ▪ Biochemical test ▪ Latex agglutination BIOCHEMICAL TEST ▪ Sugar fermentation test: fermentation of glucose, sucrose, and maltose with gas Catalase positive Oxidase positive Motility test positive TREATMENT The course of treatment is decided by the degree of dehydration Three options prove most effective: Oral Rehydration Intravenous Rehydration Antimicrobial Therapy NOTE. Intravenous and oral hydration are both associated with greatly decreased mortality and remain the mainstay of treatment for cholera. Antibiotics- To help reduce resource requirements, consider using antibiotics for patients who are seriously dehydrated or have some dehydration with continued net fluid loss despite rehydration. By decreasing duration of diarrhea and volume of stool, antibiotics result in more rapid recovery and shorter lengths of inpatient stay, both of which contribute to more efficient use of resources during an outbreak. O.R.S. The World Health Organization recommends a solution containing: 3.5 g sodium chloride 2.9 g trisodium citrate/ sodium bicarbonate 1.5 g potassium chloride 20 g glucose or 40 g sucrose Commercially sold over the counter as rehydralyte. DOSAGE – ANTIBIOTIC AGENTS Given orally when vomiting stops. Doxycycline, Erythromycin or Tetracycline are effective. Fluoroquinolones are now an effective alternative in regions where tetracycline resistance is common. WHO guidelines PREVENTION ▪ Proper sanitation and hygiene practice Antibiotic prophylaxis and vaccines are the answer to preventing the spread of disease. ▪ Vaccination is no more required for travelers as risk is small Proper sanitation and hygiene practice. Antibiotic prophylaxis and vaccines are the answer to preventing the spread of disease. Vaccination is no more required for travelers as risk is small. VACCINES Three types of cholera vaccines are currently approved for use. oral cholera vaccines (OCV): Dukoral®, Shanchol™, and Euvichol®. Killed-whole-cell formulation: killed bacterial cells and purified B subunit of the cholera toxin. CAMPYLOBACTER ▪ Motile, oxidase-positive, Gram-negative curved rods ▪ The cells have polar flagella and are often attached at their ends giving pairs “S” shapes. ▪ More than a dozen Campylobacter species have been associated with human disease. ▪ Campylobacter jejuni is by far the most common. Campylobacter jejuni ▪ Produce a membrane-bound protein cytolethal distending toxin (CDT). ▪ CDT has an A/B toxin structure in which the A subunit can cause cell cycle arrest. ▪ Grows well only on enriched media (Skirrow’s media) under microaerophilic conditions. ▪ That is, it requires oxygen at reduced tension (5%-10%) EPIDEMIOLOGY ▪ Animals are primary reservoirs-transmitted to humans. ▪ Commonly found in the normal gastrointestinal and genitourinary flora of sheep, cattle, chickens, wild birds, and many others. ▪ Undercooked poultry and unpasteurized milk are major sources. ▪ Causes diarrhea worldwide and leading cause of gastrointestinal infections in developed countries. ▪ Infecting dose is low (few hundred cells) PATHOGENESIS Colonization of intestines after ingestion Campylobacter infection occurs in the small intestine. Adherence to enterocytes mediated by flagellum. Taken up into cell by endocytosis & move with the assistance of microtubules. Invasion together with cytotoxin CDT & LOS contribute to injury leading to inflammation. The death of these specialized cells is thought to lead to the loss of function and erosion of the protective intestinal epithelial layer thus producing the electrolyte disturbances and malabsorption associated with diarrhea. CLINICAL MANIFESTATION ▪ Incubation period of 2- 7 days ▪ Fever & lower abdominal pain severe enough to mimic acute appendicitis. ▪ Diarrhea that usually contain blood and pus follow. ▪ The illness is typically self-limiting after 3 to 5 days but may last 1 to 2 weeks. DIAGNOSIS ▪ The diagnosis is confirmed by isolation of the organism from the stool. ▪ Selective media for Campylobacter e.g., Campylobacter agar ▪ Incubated in Microaerophilic atmosphere incubator or in jars with anaerobic gas pack kits ANAEROBIC JARS CAMPYLOBACTER AGAR Bacteria appear as small, gray, flat, non-hemolytic, mucoid colonies at 24 and 48 hours Skirrows medium contains vancomycin, polymyxin B, trimethoprim to inhibit other bacteria. TREATMENT Campylobacter infections are self-limiting. Usually not treated unless the disease is severe or prolonged (lasting longer than 1 week). Erythromycin may shorten course. Most people recover from Campylobacter infection without antibiotic treatment. Patients should drink extra fluids as long as diarrhea lasts. Some people with, or at risk for, severe illness might need antibiotic treatment. HELICOBACTER Genus of Gram -ve bacteria, slender curved rods with polar flagella Contains about 35 species most important being Helicobacter pylori. Some members found in lining of the upper GIT in some mammals and birds. Able to thrive in the acidic mammalian stomach by producing enzyme urease. They are motile and fast moving using their flagella. They are Microaerophilic. HELICOBACTER BACTERIAL CELL BACTERIOLOGY ▪ Has morphologic and growth similarities to the campylobacter ▪ Growth requires a Microaerophilic atmosphere and is slow (3–5 days). ▪ Produces high amounts of urease allowing it to persist in acidic environment. Helicobacter pylori Gram stain EPIDEMIOLOGY Most common chronic bacterial infection in the world 50% of the world's population has H. pylori in their upper GIT. Once established, the same strain persists for years, decades, even for life. Transmitted through contaminated water, fecal-oral route and inadequately disinfected endoscopic devices Individuals infected have 10-20% risk of developing complications. It was classified by the WHO as a class 1 carcinogen in 1994 Infected individuals have a 1-2% risk of developing gastric cancer PATHOGENESIS Adhesins enable the bacteria to adhere to the gastric mucosa and resist peristalsis. Motility enables the organism to move to less acidic locale beneath the gastric mucus. It produces urease that breaks down urea to ammonia that neutralizes gastric acid. Multiple factors stimulate inflammation of gastric mucosa (gastritis) Prolonged and aggressive inflammatory response could lead to epithelial cell death and ulcers. Decades of inflammation and assault by the virulence factors just described could cause metaplasia, and eventually cancer Ulcers occur when stomach acid and digestive enzyme pepsin overwhelm protective mechanisms in the stomach and duodenal mucous membranes after inflammation. Cascade of chronic gastritis, atrophic gastritis, intestinal metaplasia (IM), dysplasia, and adenocarcinoma DUODENAL ULCER CLINICAL MANIFESTATION ▪ 85% of those infected are asymptomatic. ▪ Primary infection sometimes causes an illness with nausea and upper abdominal pain lasting up to 2 weeks. ▪ Inflammation of the pyloric antrum is likely to lead to duodenal ulcers. ▪ Inflammation of the stomach body is likely to lead to gastric ulcers. DIAGNOSIS ▪ Non-invasive Diagnostic Tests ▪ Serologic tests – Detection of antibody (IgG and IgA) directed against H. pylori ▪ Urea breath tests – Ingestion of C14 labelled urea & measure labelled CO2 ▪ Stool antigen- immunoassay for the detection of H.pylori antigens in human feces A Helicobacter pylori stool antigen test checks your stool (feces) for Helicobacter pylori antigens. DIAGNOSIS ▪ Invasive tests ▪ Endoscopic Tests- Endoscopic examination and biopsy collection ▪ Rapid Urease Test-diagnostic test contains urea and change in pH induces color change. ▪ Histology ▪ Culture –Inoculation on Blood /chocolate agar or special medium and incubated in Microaerophilic conditions for 3-7 days. ▪ Nucleic acid amplification test- PCR ESOPHAGOGASTRODUODENOSCOPY (EGD) RAPID UREASE TEST Helicobacter pylori colonies on blood agar TREATMENT Primary Treatment Regimens for Hp Infection Triple therapy: PPI (Omeprazole, Esomeprazole), Clarithromycin, And Amoxicillin (each twice daily) or: PPI, Clarithromycin, And Metronidazole (each twice daily)- Appropriate for penicillin- allergic individuals Other antibiotics: - Levofloxacin and Tetracycline Histamine blockers Bismuth subsalicylate