Lecture 1 (Salmonelosis and Brucellosis) PDF

12/11/1445 Salmonella typhi, enteric fever and Brucella By Dr : Sameer al Sharapy Course Name: Microbiology of Hematopoietic and Lymphoid System (HLS). Course contents: 1 12/11/1445  1- Medical Microbiology. An Introduction to infec...

12/11/1445 Salmonella typhi, enteric fever and Brucella By Dr : Sameer al Sharapy Course Name: Microbiology of Hematopoietic and Lymphoid System (HLS). Course contents: 1 12/11/1445  1- Medical Microbiology. An Introduction to infectious Diseases. By Sheries, 5th  edition, 2010.  2- Joanne Willey, Kathleen Sandman, Dorothy Wood - Prescott's Microbiology 11th Edition-McGraw-Hill Education (2019).  3- Jennifer Lusk_ M. Kelly Cowan_ Heidi Smith - Microbiology Fundamentals_ A Clinical Approach-McGraw-Hill Education (2019).  Objectives of this lecture  Students should be able to:  Define Salmonellosis and brucellosis.  Describe the causative organism.  Describe pathogenesis and clinical features of the disease.  Mention diagnostic methods of Salmonellosis and brucellosis.  State treatment of Salmonellosis and brucellosis.  Describe prevention and control of the disease. 2 12/11/1445 Salmonellosis  Definition  An infectious disease caused by the bacterium Salmonella typhi (Salmonella enterica Serovar Typhi ) and less commonly by Salmonella paratyphi.  Characteristics of Salmonella  This gram-negative enteric bacillus.  Belongs to the family Enterobacteriaceae.  It is a motile with peritrichous flagella.  Non- sporing.  Non capsulated. some of them are capsulated except S. typhi /paratyphi).  Size varies from 2-4 X 0.6 micron. Cultural Characteristics  They are aerobics, facultative anaerobes.  Growing optimum in the temperature of 37C degree and in the pH of 6-8.  Brows on simple media - Nutrient agar, Temp 15- 41°- c/ 37°- 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.  H2S produced by Salmonella typhi.  Enrichment Medium (Liquid Medium) Tetrathionate broth  Above medium are used for isolation of Salmonella from contaminated specimens particularly stool specimens. 3 12/11/1445 Typhoid fever  Typhoid fever: is a systemic bacterial disease caused primarily by Salmonella Typhi.  Typhoid fever is caused by S. enterica serovar Typhi and is acquired by:  paratyphoid fever is a similar illness but is caused by the organism Salmonella Para typhi , three serotypes A, B and C. Causes 1. Caused by the bacterium Salmonella Typhi. 2. Ingestion of contaminated food or water. 3. Contact with an acute case of typhoid fever. 4. Water is contaminated where inadequate sewerage systems and poor sanitation. 5. Contact with a chronic asymptomatic carrier. 6. Eating food or drinking beverages that handled by a person carrying the bacteria. Antigenic structure of Salmonella  Two sets of antigens detection by serotyping. 1- Somatic or O Antigens: contain long chain polysaccharides ( LPS ) comprises of heat stable polysaccharide commonly.  Forms integral part of Cell wall.  Like Endotoxin.  O Antigens unaffected by boiling.  O antigens are less immunogenic, than H antigens. 2- Flagellar or H Antigens: are strongly immunogenic and induces antibody formation rapidly.  The capsular Vi- Surface antigen in some species only.  Destroyed after boiling at 60 C /1 hour.  Vi a polysaccharide.  Acts as virulence factor, protects the bacilli against Phagocytosis.  Poorly immunogenic.  Low titer of antibodies are produced, Not diagnostic. 4 12/11/1445 Pathogenicity  Salmonella typhi and Salmonella para typhi primarily cause infection in humans.  Man acquires infection via oral route by ingestion of contaminated water or contaminated food.  Typhoid fever can be caused by ingestion of a small number of bacilli.  But the para typhoid fever needs the consumption of large number of bacilli to produce infection.  The Salmonella produces three important clinical diseases, 1- ENTERIC FEVER 2- SEPTICEMIA 3- SALMONELLA ENTEROCOLITIS  1- ENTERIC FEVER  It is usually caused by Salmonella typhi (typhoid fever) and Salmonella para typhi A,B and C (para typhoid fever)  Pathogenicity  TYPHOID FEVER  On reaching the gut via contaminated food or water the bacilli undergone through the following stages. Incubation phase Septicemia phase Localization phase  INCUBATION PHASE It ranges from 10-14 days.  When reaches the bacilli in the abdomen most of them will be destroyed, but some of them are revived and attaches to the epithelial cells of villi.  These cells then enters to the mesentric lymph nodes and multiplication occurs.  After multiplication the bacteria enters to the blood stream and causes primary infection. 5 12/11/1445  Pathogenicity  SEPTICEMIA PHASE  During this stage: the bacilli are entered to the gall bladder, spleen, liver bone marrow, lungs and kidney and the further multiplication occurs.  After multiplication it enters to blood and causes secondary multiplication.  During this time they produce toxins and causes fever and other symptoms.  LOCALIZATION PHASE  Some of the fully grown bacilli will localized in the organs like liver, gall bladder, spleen etc and producing the toxins.  So that the tissue becomes inflammed, necrosis and results in typhoid ulcer.  Later this ulcer leads to hemorrhage and perforation. Signs and symptoms  Once signs and symptoms do appear, you're likely to experience:  Fever that starts low and increases daily, possibly reaching as (40.5 C).  Headache.  Weakness and fatigue.  Muscle aches.  Sweating.  Dry cough.  Loss of appetite and weight.  Abdominal pain.  Diarrhea or constipation.  Rash. High fever Aches and pains  Extremely swollen abdomen 6 12/11/1445  PARATYPHOID FEVER  Paratyphoid fever: is mainly caused by salmonella para typhi A,B and C  PARA TYPHOID A  In this the paratyphoid fever resembles typhoid fever but presents with more abrupt onset and mild symptoms.  The features are fever, headache, abdominal pain, malaise, anorexia, cough, hepatomegaly and splenomegaly.  PARA TYPHOID B  It also causes paratyphoid fever.  It may occur as typhoid like illness or severe gastro enteritis.  Cold sores or fever blisters are frequently seen in this infection.  PARATYPHOID C  It is also causes paratyphoid disease. It is a rare type of infection. LABORATORY DIAGNOSIS  Hematological investigations.  Bacteriological investigations. - Blood culture. - Stool culture. - Urine culture. - duodenal juice or bile culture.  In enteric fevers: a blood culture reveals Salmonella during first 2 weeks of illness.  On MacConkey & EMB agar: Salmonella forms non-lactose-fermenting colonies.  Typhoid fever  Specimen : stool, blood, bone marrow.  GS : Gram negative rod.  Freshly passed stool is the preferred specimen for isolation of salmonella spp.  S typhi or S paratyphi may also be isolated from urine, rose spot biopsy, or gastric or intestinal secretions. 7 12/11/1445 Identifying Enteric Organisms Isolates which are Non lactose fermenting. Motile, Indole positive. Urease negative. Oxidase –ve. Ferment Glucose, Mannitol, Maltose. Do not ferment Lactose, Sucrose. Some of the Paratyphoid form acid and gas.  H2S produced by Salmonella typhi.  Salmonella Paratyphi A do not produce H2S. Methyl Red +  VP –  Citrate +  Serology:  The diagnosis can be made serologically by detecting a rise in antibody titer in the patient's serum.  Widal test: 1:160 is diagnostic.  Widal test detects antibodies in serum against the O&H antigens of salmonella species. 8 12/11/1445 Prevention:  Apply public health and personal hygiene measures.  Proper sewage disposal and proper chlorinated water supply.  Cultures of stool for food handlers to detect carriers.  Pasteurization of milk, proper cooking of poultry, eggs, and meat.  Vaccination:  Two vaccines are available, giving 50-80% protection against S typhi.  One vaccine consists of acetone-killed S typhi organisms, administered I.M.  The other vaccine is a live, attenuated S typhi and is taken orally.  BRUCELLOSIS  Brucellosis is a zoonosis primarily of domestic animals, causing a chronic debilitating septicemic disease leading to abortion.  Morphology of Brucella  Brucella are small (0.4～0.8 ×0.5～1.5μm).  Non-motile,  non-capasulate  gram-negative coccobacilli.  The organism is aerobic. 9 12/11/1445 Brucella  The genus Brucella consists of six species, four of which cause human  Growth Characteristics brucellosis  Nutritional requirements are 1. Brucella melitensis (goats) complex. 2. Brucella suis (swine)  Some strains have been cultivated 3. Brucella abortus (cattle) on defined media containing amino acids, vitamins, salts, and 4. Brucella canis (dogs) glucose.  Are all intracellular organisms.  Inoculated on trypticase-soy  The disease in humans, brucellosis agar or blood culture media. (undulant fever, Malta fever).  Brucellae are moderately sensitive  Characterized by an acute bacteremic to heat and acidity. phase followed by a chronic stage that may extend over many years and may  They are killed in milk by involve many tissues. pasteurization. Antigenic Structure and Classification  A and M antigens are common to 3 mains Brucella spp.  B. melitensis has the highest concentration of M antigen and causes the most serious infections.  The difference between species is related to the amount of the two main antigen: 10 12/11/1445 Spread of Brucella in the body  Mode of transmission  Portals of entry:  Oral entry - most common route  Ingestion of contaminated animal products (often raw milk or its derivatives).  Contact with contaminated fingers.  Aerosols  Inhalation of bacteria.  Contamination of the conjunctivae.  Percutaneous infection through skin abrasions or by accidental inoculation. pathogenesis  Incubation period: is between 2 and 6 weeks.  Common route of infection: ingestion of contaminated milk, mucous membrane droplets.  The organism GIT Regional lymph nodes. Thoracic duct and bloodstream disseminated to other organs (liver, spleen, and bone marrow). There it cause granulomatous nodules may develop abscesses. 11 12/11/1445 Clinical Manifestations  The presentation of brucellosis is characteristically variable.  The onset may be insidious or abrupt.  Influenza-like with fever reaching 38 to 40oC.  Limb and back pains are unusually severe, night sweating.  Anorexia, weakness, severe fatigue and loss of weight, depression.  Headache.  The leukocyte count tends to be normal or reduced, with a relative lymphocytosis.  Relative leukopenia.  On physical examination, splenomegaly may be the only finding. Lab diagnosis  Serology:- most commonly used method of diagnosing brucellosis.  Rose Bengal Test is useful for screening.  Measurement of antibodies.  Titers higher than 1:160 highly suggestive of infection.  Culture: from blood /bone marrow or other tissues ,(definitive diagnosis).  ELISA  High IgM in acute infection.  High IgG in chronic infection.  PCR :is a rapid and accurate method for diagnosis of Brucella species. 12 12/11/1445  CLINICAL DIAGNOSIS o CBC: Non specific, (leucopenia, lymphocytosis, anemia). Moderate elevation of ESR.  Prevention and control  Pasteurization of dairy products and use of protective clothing prevent human infection.  More importantly, systematic identification and elimination of infected animals and vaccination of animals reduces the reservoir.  Eradication of brucellosis in cattle can be attempted by test and slaughter,  Active immunization of humans against brucella infection is experimental.  Control rests on limitation of spread and possible eradication of animal infection. 13 12/11/1445 14