Pathogens of the gastrointestinal tract. Dr. Dóra Szabó Semmelweis University Institute of Medical Microbiology

Transcription

1 Pathogens of the gastrointestinal tract Dr. Dóra Szabó Semmelweis University Institute of Medical Microbiology

2 Gram-negative facultative anaerobic rods (Positive glucose fermentation) Oxidase positive Oxidase negative Vibrionaceae Aeromonadaceae Enterobacteriaceae Facultative pathogenic Obligate pathogenic Vibrio Plesiomonas Aeromonas Escherichia Klebsiella Enterobacter Proteus Serratia Providencia Morganella Edwardsiella Citrobacter Hafnia Salmonella Shigella Yersinia

3 Enterobacteriaceae Morphology and General Characteristics Gram-negative, non-sporing, rod shaped bacteria Oxidase Ferment glucose and may or may not produce gas in the process (aerogenic vs anaerogenic) Differentiation biochemical reactions differences in antigenic structure Slideagglutination!

4 Enterobacteriaceae Member of the normal GI tract GI tract of human and animal Pathogen species Enteral pathogens Extraintestinal pathogens More than 15 species: Escherichia, Shigella, Edwardsiella, Salmonella, Citrobacter, Klebsiella, Enterobacter, Hafnia, Serratia, Proteus, Providencia, Morganella, Yersinia, Erwinia, Pectinobacterium

5 Escherichia coli Member of the normal GI tract Extraintestinal infection urinary tract infections Neonatal meningitis strains with the K1 capsular antigen. Peritonitis, cholecystitis Nosocomial infections Intestinal infections - gastroenteritis

6 E. coli intestinal infections Gastroenteritis there are several distinct types of E. coli that are involved in different types of gastroenteritis: enterotoxigenic E. coli (ETEC), enteroinvasive E. coli (EIEC), enteropathogenic E. coli (EPEC), enteroaggregative E. coli (EAEC), and enterohemorrhagic E. coli (EHEC).

7 Summary of E.coli strains that cause gastroenteritis.

8 E. coli gastroenteritis enteroheamorrhagic E. coli (EHEC). EHEC The organism attaches via pili to the intestinal mucosa and liberates the shiga-like toxin. Symptoms: watery diarrhea,bloody diarrhea without pus and crampy abdominal pain with no fever or a low-grade fever This may progress to hemolytic-uremic syndrome that is characterized by low platelet count, hemolytic anemia, and kidney failure. This is most often caused by serotypes O157:H7. ZOONOSIS, Hamburgers!

9 Gram-negative facultative anaerobic rods (Positive glucose fermentation) Oxidase positive Oxidase negative Vibrionaceae Aeromonadaceae Enterobacteriaceae Facultative pathogenic Obligate pathogenic Vibrio Plesiomonas Aeromonas Escherichia Klebsiella Enterobacter Proteus Serratia Providencia Morganella Edwardsiella Citrobacter Hafnia Salmonella Shigella Yersinia

10 SALMONELLA

11 SALMONELLA SPP. Gram-negative motile rods, peritrich flagella Facultative anaerobic O antigens H (flagella) antigens Salmonella typhi also has a Vi antigen which is a capsular antigen. Biochemical properties: H 2 S production Lactose negative, Urease negative, Indol negative

12 Clinical significance GASTROENTERITIS, SALMONELLOSIS Salmonella enteritidis Salmonella typhimurium ENTERIC FEVER Salmonella typhi S. paratyphi A, B, and C ZOONOZIS

13 GASTROENTERITIS, SALMONELLOSIS

14 SALMONELLOSIS - Pathogenesis

15 SALMONELLOSIS - Clinical picture I. Symptoms generally appear 18 to 36 hours after exposure, but they can occur as quickly as 12 hours or as long as 72 hours after exposure. GASTROENTERITIS, but can be: dizziness vomiting Abdominal pain The symptoms can be similar to dysentery The symptoms moderate in a few days spontan recovery in a week After recovery carrier status can occur That patient can a source of infection later

16 SALMONELLOSIS - Clinical picture I. Transient bacteraemia can occur Permanent bacteraemia, sepsis, meningitis: Very old patient Very young patient Immunsuppressed and AIDS patient Focal infections can occur lung brain in atherosclerotic plaque of aorta prothesis

17 SALMONELLOSIS - Epidemiology One of the most common cause of foodpoisoning More than known cases per year in Hungary 1-10% of the real cases Increasing incidence Reservoirs: Chicken and duck eggs Chicken and swine The feces of some pets, especially those with diarrhea Reptiles: turtles, lizards, snakes Insufficient heat treatment is necessary!!

18 SALMONELLOSIS Microbiological diagnosis I. Clinical specimen: faeces : positive from first week, and may remain positive for severa weeks food leftover Microscopic examination: Direct smear has no value in the diagnosis. Culture: Samples are inoculated onto brilliant green and/or bismuth sulphite selective media. Identification: Biochemical identification, slide agglutination (O and H agglutination

19 SALMONELLOSIS - Therapy 1. Water and electrolytes replacement 2. The vast majority of enterocolitis cases do not require an antibiotic treatment. After antibiotic treatment carrier status occurs more frequently. Antimicrobial treatment of Salmonella infection of neonates, as well as invasive salmonella infections is important. ampicillin sulfomethoxazole + trimethoprim fluoroquinolones 3rd generation cephalosporins Antibiotic susceptibility tests are important

20 ENTERIC FEVER

21 The source is always human!! ENTERIC FEVER THYPHOID FEVER caused by S. typhi, PARATHYPHOID FEVER caused by S. paratyphi A, B and C milder disease

22 ENTERIC FEVER - Pathogenesis

23 ENTERIC FEVER - Clinical picture First week: The disease classically presents with step-ladder fashion rise in temperature (40-41 C) over 4 to 5 days, accompanied by headache, vague abdominal pain, and constipation. Second week: Between the 7 th -10 th day of illness, mild hepato-splenomegally occurs in majority of patients. Relative bradycardia may occur and rose-spots may be seen. Third week: The patient will appear in the "typhoid state" which is a state of prolonged apathy, toxaemia, delirium, disorientation and/or coma. Diarrhoea will then become apparent. If left untreated by this time, there is a high risk (5-10%) of intestinal hemorrhage and perforation. Rare complications: Typhoid hepatitis, Empyema, Osteomyelitis, Cystitis and Psychosis. 2-5% patients may become Gall-bladder carriers

24 Typhoid fever a: petechia, b: Peyer plaque and necrosis of the ileum c, d: perforation of the Peyer-plaque

25 Fig Typhoid fever. Numerous ulcers of the small intestine overlying hyperplastic lymphoid follicles (Peyer s patches). By courtesy of Dr. J. Newman.

26 Rose spots on the chest and abdomen of patients with typhoid fever due to the bacterium Salmonella typhi.

27 ENTERIC FEVER Microbiological diagnosis I. Clinical specimen: faeces: positive from the second or third weeks (45-75% positive) urine : positive from the second week (45-75% positive) bile, bone marrow aspirate (85-95% positive) blood for blood-culture : often positive (70-80%) in the first week Culture: Samples are inoculated onto brilliant green and/or bismuth sulphite selective media. Blood serology: => Gruber-Widal reaction (Widal`s type tube agglutination): (Ag = 'H' as well as 'O' antigens of the laboratory strain of S. typhi) to show presence and establish titre of specific antibodies in the patient s serum.

28 Biochemical identification: (refer to flow charts) Lactose (-), dextrose fermentation w/o gas formation, H2S (+) Serological identification: Slide agglutination with specific antibodies to show presence of S. typhi cells in the culture. Blood serology: => Gruber-Widal reaction (Widal`s type tube agglutination): (Ag = 'H' as well as 'O' antigens of the laboratory strain of S. typhi) to show presence and establish titre of specific antibodies in the patient s serum. High titre of antibody to O antigen > 1:640 is suggestive but not specific. ENTERIC FEVER Microbiological diagnosis II.

29 ENTERIC FEVER Treatment and prevention Treatment Antibiotics according to susceptibility tests: S. typhi strains are usually susceptible to ampicillin, sulfomethoxazole + trimethoprim, 3rd generation cephalosporins. Prevention Specific sanitary measures and control of chronic carriers. Vaccination Injectable Typhoid vaccine (TYPHIM Vi,TYPHIVAX) The live oral vaccine (TYPHORAL) TAB vaccine Carriers 3 % of survivors of typhoid become permanent carriers, harbouring the organisms in the gallbladder, biliary tract or urinary tract.

30 In 1906, Irish immigrant Mary Mallon worked as a cook in the Oyster Bay summer home of New York banker Charles Henry Warren and his family. By the end of the summer, six members of the Mary Mallon (wearing glasses) photographed with bacteriologist Emma Sherman on North Brother Island in 1931 or 1932, over 15 years after she had been quarantined there permanently. household had contracted typhoid fever. Mallon, while immune herself to the disease, was its carrier. For three years, she was isolated on North Brother Island, near Rikers Island, earning the nickname "Typhoid Mary." Instructed not to cook for others upon her release, she nevertheless changed her name and became a cook at a maternity hospital in Manhattan. At least 25 staff members contracted typhoid. "Typhoid Mary" returned to North Brother Island, where she lived alone for 23 years, until her death in She died of a stroke after 23 years in quarantine.

31 SHIGELLA

32 SHIGELLA GENUS Contains four species that differ antigenically based on antigen and to a lesser extent, biochemically. Serogroup A: S. dysenteriae (12 serotypes) Serogroup B: S. flexneri (6 serotypes) Serogroup C: S. boydii (23 serotypes) Serogroup D: S. sonnei (1 serotype) OBLIGATE HUMAN PATHOGEN

33 VIRULENCE FACTORS OF SHIGELLA Shiga toxin chromosomally encoded role in the ulceration of the intestinal mucosa and in the death produced by S. dysenteriae and in smaller amounts by S. flexneri and S. sonnei. Effect the capillar endothel B-subunit binds to Gb3 glycolipid receptor A-subunit inhibit the protein synthesis binding by inactivating the 60S ribosomal subunit of aminoacyl-transfer RNA Iron capturing ability Other toxins: neurotoxic, cytotoxic and enterotoxic

34 SHIGELLOSIS - Pathomechanism I.

35 SHIGELLOSIS - Pathomechanism II. Shigella penetrate the mucosa and epithelial cells of colon, but most commonly in the rectum and ampulla. No before terminal ileum. Lead to inflammation of the colon, and necrosis of the colonic epithelium. The resulting colitis and ulceration of the mucosa result in bloody, mucoid stools, and/or febrile diarrhea

36 SHIGELLOSIS Clinical picture There is an incubation of 1-7 days Fever, cramping, abdominal pain, and diarrhea (due to the toxin) for 1-3 days. This may be followed by frequent, scant stools with blood, mucous, and pus (due to invasion of intestinal mucosa). Complictions: HUS, reactive arthritis Reiter-syndrome The severity of the disease depends upon the species one is infected with. S. dysenteria (producing Shiga toxin) is the most pathogenic followed by S. flexneri, S. sonnei and S. boydii.

37 Colon in dysenteriae

38 Shigellosis. Sigmoidiscopic view of colonic mucosa in a fatal case of infection with S. dysenteriae type 1 showing extensive pseudomembranous colitis. Shigellosis. Sigmoidiscopic view of colonic mucosa in a mild case of infection due to S. flexneri. Note the thin whitish exsudate, which is made up of fibrin and polymorphonuclear leucocytes.

39 SHIGELLOSIS Epidemiology Transmission is via the fecal-oral route, but by food and by wateras well. The infective dose required to cause infection is very low ( organisms). Dirty hand disease Shigella dysenteriea 1: Asia, Africa, Middle-America Shigella sonnei: US, Europe

40 SHIGELLOSIS Microbiological diagnosis Clinical specimen: faeces, food leftover Culture: Samples are inoculated on selective-differentiating medias. -dezoxycholate citrate agar - eosin methylen blue agar Biochemical identification, slide agglutionation for O antigen Positive Serény test. Keratoconjunctivitis in the rabbit produced by the instillation of shigella microorganism

41 SHIGELLOSIS-Treatment and prevention Treatment Water and electrolytes replacement Antimicrobial therapy Sulfonamides are commonly used as are streptomycin, tetracycline, ampicillin, and chloramphenicol. Resistant strains are becoming increasingly common, so sensitivity testing is required. Prevention Vaccination Live attenuated vaccine Subunit vaccines

42 Yersinia Three species are important pathogens in human Yersinia pestis causes plague Yersinia enterocolitica enteropathogenic Yersinia pseudotuberculosis enteropathogenic

43 Yersinia enterocolitica Y. pseudotuberculosis Infection with contaminated food or water fever and abdominal pain Y. enterocolitica *watery diaorrhea Invade the intestinal epithelium by invasion of M cells penetrate into the underlying lymphoid tissue causing inflammation extreme pain associated with the infections (resembles acute appendicitis) drain into adjacent mesenteric lymph nodes, causing mesenteric lymphadenitis Reactive arthritis may occur in some people following Y. enterocolitica infection. It is thought to be due to cross reacting T cells or antibodies that attack the joints Y. enterocolitica is a common cause of human disease, whereas, Y. pseudotuberculosis is mainly a disease of other animals.

44 Gram-negative facultative anaerobic rods (Positive glucose fermentation) Oxidase positive Oxidase negative Vibrionaceae Aeromonadaceae Enterobacteriaceae Facultative pathogenic Obligate pathogenic Vibrio Plesiomonas Aeromonas Escherichia Klebsiella Enterobacter Proteus Serratia Providencia Morganella Edwardsiella Citrobacter Hafnia Salmonella Shigella Yersinia

45 Vibrionaceae Vibrio spp. V. cholerae V. paraheamolyticus Aeromonas spp. Plesiomonas spp. Photobacterium spp.

46 V. cholerae Classification Scheme NON-TOXIGENIC I may not be O1, Or O139! (but I can still stir up trouble) TOXIGENIC I define Vibrios! I m an O1 or O139 Strain panf/cholerae.html

47 Classification Scheme Toxigenic V. cholerae Division into 2 epidemic serotypes O1 Division into 2 biotypes O139 Classical El Tor Each O1 biotype can have 3 serotypes inaba ogawa hikojima Division into ribotypes A & C A & B (A little C) Antigens A, B, C Designed using information presented in review by NS Crowcroft Cholera: Current Epidemiology. The Communicable Disease Report. 4(13): R158-R163.

48 Biochemical Properties Gram-negative Straight or curved rods Oxidase positive Fermentative and oxidative in metabolism

49 Pathogenesis Transmitted by the fecaloral route Adheres and colonizes to the small bowel Toxin co-regulated pili (TCP) Secretes the cholerae enterotoxin (CT) Causes an increase in camp

50 Pathogenesis The organism never invades the cell!! Cholera toxin (AB toxin) will increase the camp level The increased camp causes: Mucosal cells to pump large amounts of Cl - into the intestine Water, Na +, and other electrolytes follow due to the osmotic and electrical gradients Diarrhea results, leading to the classic symptoms of cholerae

51 Clinical Manifestations

52 Modes of Transmission Water (infectious dose = 10 9 ) Food (infectious dose = 10 3 ) Person-to-person The 19th-century illustration depicting the spirit of death at a pump was taken from

53 Diagnosis Severe watery diarrhea Rice-water stool Dehydration Loss of urine production Shock A wet mount of liquid stool can be examined microscopically

54

55 cholerae cot s

56 Microbiological detection Microbiological culture-based methods using fecal or water samples TCBS (thiosulphate citrate bile salts) media Rapid Tests Dark-field microscopy Rapid immunoassays Molecular methods - PCR and DNA probes

57 Cholera Treatment Rehydration Parenteral Oral Antibiotic treatment not recommended! Short duration of illness Antibiotic resistance Limited gain from usage

58 Treatment: Oral Rehydration Salts (ORS) Reduces mortality from over 50% to less than 1% Packets of Oral Rehydration Salts Distributed by WHO, UNICEF Dissolve in 1 L water NaCl, KCl, NaHCO 3, glucose

59 Treatment: How ORS Works Na + transport coupled to glucose transport in small intestine Glucose enables more efficient absorption of fluids and salts Potassium passively absorbed

60 479. Dehydrated patient before treatment

61 480. Rehydration dehydrated patient after treatment

62 Vaccines Need localized mucosal immune response Oral Vaccine Not recommended Travelers have very low risk of contracting disease: 1-2 cases per million international trips Not cost-effective to administer vaccines in endemic regions Brief and incomplete immunity Two types approved for humans: Killed whole-cell Live-attenuated

63 Thank you for the attention!