Enteric fever


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Enteric fever

  1. 1. ENTERIC FEVER Dr.T.V.Rao MD Dr.T.V.Rao MD 1
  2. 2. Salmonella A Very complex group  Contains more > 2,000 spp  Typed on the basis of Serotyping, and species typing  Divided into two groups  1 Enteric fever group 2 Food poisoning group – 3 Septicemias Dr.T.V.Rao MD 2
  3. 3. Salmonella can cause  Causes Infections in Humans and vertebrates,  Enteric Fever ( Typhoid fever )  Gastroenteritis  Septicemias,  Carrier state a concern Dr.T.V.Rao MD 3
  4. 4. Key points There are more than 2000 different antigenic types of Salmonella; those pathogenic to man are serotypes of S. enterica.  Most serotypes of S. enterica cause food-borne gastroenteritis and have animal reservoirs.  S. enterica serotypes Typhi and Paratyphi cause typhoid fever.  Dr.T.V.Rao MD 4
  5. 5. Enteric Fever Typhoid Fever  Caused by Salmonella typhi, and other Groups called as Paratyphoid A, B, C  Salmonella typhi - Causes Typhoid  Salmonella Paratyphi A,B,C Causes Paratyphoid fevers.  Food Poison group  Spread from Animals – Humans  Causes Gastroenteritis – Septicemias, Localized Infection Dr.T.V.Rao MD 5
  6. 6. Typhoid fevers are prevalent in many regions in the World Dr.T.V.Rao MD 6
  7. 7. Typhoid Mary Most Dangerous Woman in America Dr.T.V.Rao MD 7
  8. 8. Typhoid Mary A Dr.T.V.Rao MD famous example is “Typhoid” Mary Mallon, who was a food handler responsible for infecting at least 78 people, killing 5. These highly infectious carriers pose a great risk to 8
  9. 9. Morphology of Salmonella Gram negative bacilli 1-3 / 0.5 microns, Motile by peritrichous flagella Dr.T.V.Rao MD 9
  10. 10. Bacteriology –Typhoid fever  The Genus Salmonella belong to Enterobacteriaceae  Facultative  Gram anaerobe negative bacilli  Distinguished from other bacteria by Biochemical antigen structure and Dr.T.V.Rao MD 10
  11. 11. Cultural Characters Aerobic / Facultatively anaerobic  Grows on simple media – Nutrient agar,  Temp 15 – 41ºc / 37º c  Colonies appear as large 2 -3 mm, circular, low convex,   On MacConkey medium appear Colorless ( NLF ) Selective Medium - Wilson Blair Bismuth sulphide medium. Produce Jet black colonies H2 S produced by Salmonella typhi Dr.T.V.Rao MD 11
  12. 12. Enrichment Medium Liquid Medium Selenite F medium Tetrathionate broth Above medium are used for isolation of Salmonella from contaminated specimens Particularly stool specimens.. Dr.T.V.Rao MD 12
  13. 13. Identifying Enteric Organisms Isolates which are Non lactose fermenting  Motile, Indole negative  Urease negative  Ferment Glucose,Mannitol,Maltose  Do not ferment Lactose, Sucrose  Typhoid bacilli are anaerogenic  Some of the Paratyphoid form acid and gas  Further identification done by slide agglutination tests  Dr.T.V.Rao MD 13
  14. 14. Biochemical Characters Glucose ,Mannitol ,Maltose produce A/G  Salmonella typhi do not produce gas  Lactose/Salicin/sucrose not fermented.  Indole –  Methyl Red +  VP  Citrate +  Urea –  H2S – produced by Salmonella typhi  Paratyphi A do not produce H2S  Dr.T.V.Rao MD 14
  15. 15. Resistance of Salmonella 55º c – 1 hour 60º c – 15 MT Boiling ,Chlorination, Pasteurization Destroy the Bacilli. Dr.T.V.Rao MD 15
  16. 16. Pathogenicity  Salmonella are definite parasites to humans.  Eg S.typhi.  S.paratyphi A, B ,C  Other groups Salmonella  The important clinical syndromes 1. Enteric fever, Septicemias, gastroenteritis. Dr.T.V.Rao MD 16
  17. 17. Enteric Fever: S. typhi  Ileocecal penetration  intraluminal multiplication  mononuclear response (macrophages)  Salmonella remains alive  2nd week - lymphoid hyperplasia (mesenteric lymph nodes)  back to bowel Dr.T.V.Rao MD 17
  18. 18. Dr.T.V.Rao MD 18
  19. 19. Enteric Fever Typhoid Typhoid – caused by S.typhi Paratyphoid Caused by Paratyphi A,B,C Typhoid --- Like Typhus 7, Infective dose ID50 / 10 Dr.T.V.Rao MD 19
  20. 20. Fever  All the events coincides with Fever and other signs of clinical illness  From Gall bladder further invasion occurs in intestines  Involvement of peyr’s patches, gut lymphoid tissue  Lead to inflammatory reaction, and infiltration with monocular cells  Leads to Necrosis, Sloughing and formation of chacterstic typhoid ulcers Dr.T.V.Rao MD 20
  21. 21. Rashes in Typhoid  May present with rash, rose spots 2 -4 mm in diameter raised discrete irregular blanching pink maculae's found in front of chest  Appear in crops of upto a dozen at a time  Fade after 3 – 4 days Dr.T.V.Rao MD 21
  22. 22. Pathology and Pathogenesis  Bacilli enter through ingestion,  Bacilli attach to Microvilli,ileal mucosa, penetrate to Lamina propria and sub mucosa  Phagocytosis by Polymorphs and Macrophages  Enters the mesenteric lymph nodes  Enter the thoracic duct – Blood stream Dr.T.V.Rao MD 22
  23. 23. Pathology and Pathogenesis  Bacteremia Spread to Liver, Gall bladder, Spleen, Bone marrow, Lymph nodes, Lungs, Multiply in kidneys Once again spill into Blood stream Causes clinical illness. Dr.T.V.Rao MD 23
  24. 24. Dr.T.V.Rao MD 24
  25. 25. Pathology and Pathogenesis  Multiply abundantly in Gall bladder,  Bile rich source of Bacteria  Spill into Intestine, infects payers patches, Lymph follicles  Inflammation – Undergo necrosis, Slough off  Typhoid ulcers  Typhoid ulcers can cause perforation and hemorrhage  Duration of Illness 3 – 4 weeks  Incubation 7 -14, ( 3-56 days ) Dr.T.V.Rao MD 25
  26. 26. S.typhi more serious  The clinical features tend to be more severe with S. Typhi (typhoid fever). After penetration of the ileal mucosa the organisms pass via the lymphatic's to the mesenteric lymph nodes, whence after a period of multiplication they invade the bloodstream via the thoracic duct. Dr.T.V.Rao MD 26
  27. 27. Progress in Enteric Fever  The liver, gall bladder, spleen, kidney and bone marrow become infected during this primary bacteraemic phase in the first 7-10 days of the incubation period. After multiplication in these organs, bacilli pass into the blood, causing a second and heavier bacteraemia, the onset of which approximately coincides with that of fever and other signs of clinical illness. Dr.T.V.Rao MD 27
  28. 28. Progress in Enteric Fever  From the gall bladder, a further invasion of the intestine results. Peyer's patches and other gut lymphoid tissues become involved in an inflammatory reaction, and infiltration with mononuclear cells, followed by necrosis, sloughing and the formation of characteristic typhoid ulcers occurs. Dr.T.V.Rao MD 28
  29. 29. Immunity in Typhoid Typhoid bacilli are Intracellular pathogens Cell mediated immunity is crucial Dr.T.V.Rao MD 29
  30. 30. Clinical manifestations  Head ache, malise,anorexia ,coated tongue  Abdominal discomfort,  Constipation / Diarrhea  Step ladder type fever,  Relative bradycardia,  A soft palpable spleen  Hepatomegaly  Rose spots appear Dr.T.V.Rao MD 30
  31. 31. Complications of Enteric fever  Intestinal perforation,  Hemorrhage,  Circulatory collapse.  Bronchitis Bronchopneumonia,  Meningitis,  Cholecystitis,  Arthritis,Periostitis / Nephritis,  Osteomyletis, Dr.T.V.Rao MD 31
  32. 32. Relapses in Typhoid Fever  Apparent recovery can be followed by relapse in 5-10% of untreated cases. Relapse is usually shorter and of milder character than the initial illness, but can be severe and may be fatal. Severe intestinal haemorrhage and intestinal perforation are serious complications that can occur at any stage of the illness. Dr.T.V.Rao MD 32
  33. 33. Other complications  Causes relapses in particular to patients treated with chloramphenicol.  S.paratyphi produce septicemias. Dr.T.V.Rao MD 33
  34. 34. Typhoid carriers  Salmonella enterica causes approximately 16 million cases of typhoid fever worldwide, killing around 500,000 per year. One in thirty of the survivors, however, become carriers. In carriers the bacteria remain hidden inside cells and the gall bladder, causing new infections as they are shed from an apparently healthy host. Dr.T.V.Rao MD 34
  35. 35. Carrier Stage in Typhoid Fever  Most people infected with salmonella continue to excrete the organism in their stools for days or weeks after complete clinical recovery, but eventual clearance of the bacteria from the body is usual. A few patients continue to excrete the salmonellae for prolonged periods. The term chronic carrier is reserved for those who excrete salmonellae for a year or more. Dr.T.V.Rao MD 35
  36. 36. Carrier Stage in Typhoid Fever  Chronic carriage can follow symptomatic illness or may be the only manifestation of infection. It can occur with any serotype, but is a particularly important feature of enteric fever: up to 5% of convalescents from typhoid and a smaller number of those who have recovered from paratyphoid fever become chronic carriers, many for a lifetime. Dr.T.V.Rao MD 36
  37. 37. How we Diagnose Typhoid Fever  Diagnosis is made by any blood, bone marrow or stool cultures and with the Widal test (demonstration of salmonella antibodies against antigens O-somatic and H-flagellar ). In epidemics and less wealthy countries, after excluding malaria, dysentery or pneumonia, a therapeutic trial time with chloramphenicol is generally undertaken while awaiting the results of Widal test and cultures of the blood and stool. Dr.T.V.Rao MD 37
  38. 38. Laboratory Diagnosis of Typhoid Fever 1 Isolation of Bacilli. A Gold standard  2 Diagnosis for presence of Antibodies,  Positive Blood culture – A gold standard  Isolation from Feces and Urine ?  Detection of Antibodies Inconclusive.  Newer methods Detection of antigen in Blood and Urine Dr.T.V.Rao MD 38
  39. 39. Blood Culture 1 st week Positive in 90 % 2 nd week Positive in 75 % 3 rd week Positive in 60 % > 3 weeks positive in 25 % Draw 5 – 10 cc of Blood by venipuncture. ADD to 50 -100 ml of Bile broth. Incubate at 37 c /Subculture in MacConkey At regular intervals Dr.T.V.Rao MD 39
  40. 40. Blood Cultures in Typhoid Fevers  Bacteremia occurs early in the disease  Blood Cultures are positive in 1st week in 90% 2nd week in 75% 3rd week in 60% 4th week and later in 25% Dr.T.V.Rao MD 40
  41. 41. Castaneda’s method of Blood Culture  Double medium used Solid/Liquid medium in the same Bottle.  Bottle contains Bile broth/agar slant,  For subculture the bottle is merely tilted.  A subculture into MacConkey at regular intervals,  Reduces the chances of contamination  Increases the chances of isolation. Dr.T.V.Rao MD 41
  42. 42. Clot culture  Clot cultures are more productive in yielding better results in isolation. A blood after clotting, the clot is lysed with Streptokinase ,but expensive to perform in developing countries. Dr.T.V.Rao MD 42
  43. 43. Bacteriological Diagnosis of Typhoid Fever  Selective media, such as Deoxycholate-citrate agar or xyloselysine Deoxycholate agar, are used for the isolation of salmonella bacteria from faeces. Fluid enrichment media, such as Tetrathionate or selenite broth, are also useful to detect small numbers of salmonellae in faeces, foods or environmental samples. Dr.T.V.Rao MD 43
  44. 44. Bacteriological Diagnosis of Typhoid Fever  Suspicious colonies from the culture plates are tested directly for the presence of Salmonella somatic (O) antigens by slide agglutination and subcultured to peptone water for the determination of flagellar (H) antigen structure and further biochemical analysis. Dr.T.V.Rao MD 44
  45. 45. Slide agglutination tests  In slide agglutination tests a known serum and unknown culture isolate is mixed, clumping occurs within few minutes  Commercial sera are available for detection of A, B,C1,C2,D, and E. Dr.T.V.Rao MD 45
  46. 46. Bacteriological Diagnosis of Typhoid Fever A presumptive diagnosis of salmonellosis can often be made within 24 h of the receipt of a specimen, although confirmation may take another day, and formal identification of the serotype takes several more days. A negative report must await the result of enrichment cultures - at least 48 h. Dr.T.V.Rao MD 46
  47. 47. Bactec and Radiometric based methods are in recent use Bactek methods in isolation of Salmonella is a rapid and sensitive method in early diagnosis of Enteric fever.  Many Microbiology Diagnostic Laboratories are upgrading to Bactek methods  Dr.T.V.Rao MD 47
  48. 48. Culturing other Specimens  Feces Enrichment in Tetrathionate broth and Selenite broth  Culturing in MacConkey/DCA/Wilson Blair medium – Large black colonies.  Urine Culture – positive in 25 %  Other samples Bone Marrow,Bile,CSF/Sputum Dr.T.V.Rao MD 48
  49. 49. Serology  WIDAL Test – Tube agglutination test.  Detects O and H antibodies  Diagnosis of Typhoid and Paratyphoid  Testing for H agglutinins in Dryers tubes, a narrow tube floccules at the bottom  Testing for O agglutinins in Felix tubes, Chalky  Incubated at 37º c overnight Dr.T.V.Rao MD 49
  50. 50. Diagnosis of Enteric Fever Widal test Serum agglutinins raise abruptly during the 2nd or 3rd week  The Widal test detects antibodies against O and H antigens  Two serum specimens obtained at intervals of 7 – 10 days to read the raise of antibodies.  Serial dilutions on unknown sera are tested against the antigens for respective Salmonella  False positives and False negative limits the utility of the test  The interpretative criteria when single serum specimens are tested vary  Cross reactions limits the specificity  Dr.T.V.Rao MD 50
  51. 51. Widal Test Single test not diagnostic.  Paired samples tests  Diagnostic. O > 1 in 80 H > 1in 160 H agglutinins appear first False positives in Unapparent infection, Immunization Previously infected  Dr.T.V.Rao MD 51
  52. 52. Widal test  Anamnestic response previous infection and responding to unrelated infection  Other Diagnostic tests CIE and ELISA Detection of Circulating antigens Co agglutination test. Dr.T.V.Rao MD 52
  53. 53. Limitation of Widal Test  The Widal test is time consuming and often times when diagnosis is reached it is too late to start an antibiotic regimen.  In spite of several limitation many Physicians depend on Widal Test Dr.T.V.Rao MD 53
  54. 54. False Positive and Negative Reactions with WIDAL Test  The Widal test should be interpreted in the light of baseline titers in a healthy local population. This is especially important when there is a high local prevalence of nontyphoid salmonellosis. The Widal test may be falsely positive in patients who have had previous vaccination or infection with S typhi. Dr.T.V.Rao MD 54
  55. 55. False Positive and Negative Reactions with WIDAL Test  Widal titers have also been reported in association with the dysgammaglobulinaemia of chronic active hepatitis and other autoimmune diseases.64 '8 '9 False negative results may be associated with early treatment, with "hidden organisms" in bone and joints, and with relapses of typhoid fever. Occasionally the infecting strains are poorly immunogenic. Dr.T.V.Rao MD 55
  56. 56. WIDAL A DELETED TEST IN MANY NATIONS Widal test is Discontinued in all Developed countries, However many in Developed countries still depend on this test which lacks Sensitivity and Specificity Dr.T.V.Rao MD 56
  57. 57. Diagnosis of Carriers and Environments  Fecal carriers by isolation from specimens. or Bile aspirated.  Sewer swabs  Bacteriophage typing Dr.T.V.Rao MD 57
  58. 58. Prophylaxis TAB vaccine S.typhi 1,000 millions S Paratyphi A,B 750 millions. Injected subcutaneously 0.5 ml at 4 – 6 weeks. Live Oral Vaccine Typhoral Mutant S.typhi strain Ty 2 1a Lacking enzyme UDP galctose 4 epimerase 10 to9 Viable bacilli Given orally 1 – 3 – 5 days  Dr.T.V.Rao MD 58
  59. 59. Prevention  Vi Polysaccharide vaccine  Administered subcutaneously or intramuscular  Confers protection seven days after injection  Approximately 50% efficacy after three years  Ty 21 vaccine  Live attenuated strain of S. typhi  Administered orally in capsule form  Also available in liquid form which can be taken by children as young as two years of age Dr.T.V.Rao MD 59
  60. 60. Vaccines An Injectable vaccine Typhium Vi Contains purified Vi polysaccharide antigen from S.typhi strain Ty2 A single dose, subcutaneous route Given to children > 5 years Immunity lasts for 2- 3 years. Follow a booster Dr.T.V.Rao MD 60
  61. 61. Treatment  Chloramphenicol 1948 /1970 resistance.  Other Important drugs Ampicillin Amoxicillin, Furazolidine Cotromoxazole Chloramphenical resistance /Mexico Kerala Dr.T.V.Rao MD 61
  62. 62. Antimicrobial Therapy in Typhoid  With prompt antibiotic therapy, more than 99% of the people with typhoid fever are cured, although convalescence may last several months. The antibiotic chloramphenicol Some Trade Names CHLOROMYCETIN is used worldwide, but increasing resistance to it has prompted the use of other antibiotics BACTRIM SEPTRAN or Ciprofloxacin Dr.T.V.Rao MD 62
  63. 63. Other Drugs Fluroquinolones Ciprofloxacillin, Pefloxacillin Ofloxacillin Ceftazidime Ceftriaxone / Cefotoxaime Dr.T.V.Rao MD 63
  64. 64. Epidemiology  Developed countries - Controlled.  Water supply/ Sanitation /Economically poor.  S.typhi and S.paratyphi are prevalent in India  Previously Typhi are more common Paratyphoid A on raise.  Age 5 – 20 years, Sanitation Dr.T.V.Rao MD 64
  65. 65. Epidemiology  Sanitation has great role  Source an active patient or a Carrier shed the Bacilli.  Who are carriers. Convalescent carrier 3 weeks to 3 months Temporary carrier 1 year Chronic carrier 3 months to > 1 year, Women attain more carrier stage Dr.T.V.Rao MD 65
  66. 66. Epidemiology (Contd) Bacilli persist in the Gall bladder and kidney  Food handlers spread the infection  Cooks great role  S.typhi and S.paratyphi in humans  S.para B in Animals,  Typhoid spread through Water, Milk, Food HIV patients potentially susceptible for Typhoid disease.  Dr.T.V.Rao MD 66
  67. 67. A Simple Hand washing has many reasons to prevent Enteric fever Dr.T.V.Rao MD 67
  68. 68. Programme Created by Dr.T.V.Rao MD for Medical and Paramedical Students in the Developing World Email doctortvrao@gmail.com Dr.T.V.Rao MD 68