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Questions and Answers
Which of the following accurately describes the clinical diagnosis of Typhoid fever during Week 2?
Which of the following accurately describes the clinical diagnosis of Typhoid fever during Week 2?
What is a common complication of untreated Typhoid fever?
What is a common complication of untreated Typhoid fever?
What percentage of stool cultures are typically positive by Week 3 of Typhoid fever?
What percentage of stool cultures are typically positive by Week 3 of Typhoid fever?
What is the significant titer for the O antigen in the Widal test indicating Typhoid fever?
What is the significant titer for the O antigen in the Widal test indicating Typhoid fever?
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What is a recommended initial treatment for Typhoid fever?
What is a recommended initial treatment for Typhoid fever?
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What is an indirect method of diagnosing Typhoid fever?
What is an indirect method of diagnosing Typhoid fever?
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What is a notable sign of Typhoid fever in the third week?
What is a notable sign of Typhoid fever in the third week?
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What laboratory specimen shows 80% positive results by Week 1 in Typhoid fever?
What laboratory specimen shows 80% positive results by Week 1 in Typhoid fever?
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Which serovar of Salmonella is associated with osteomyelitis in sickle cell disease patients?
Which serovar of Salmonella is associated with osteomyelitis in sickle cell disease patients?
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What is the pathogenic dose of Salmonella in normal individuals?
What is the pathogenic dose of Salmonella in normal individuals?
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Which antigen is NOT one of the main antigens that distinguish Salmonella serovars?
Which antigen is NOT one of the main antigens that distinguish Salmonella serovars?
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What is the primary transmission route for Typhoid fever caused by Salmonella?
What is the primary transmission route for Typhoid fever caused by Salmonella?
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What is a significant outcome of the invasion of Salmonella in the ileal mucosa?
What is a significant outcome of the invasion of Salmonella in the ileal mucosa?
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What complication may occur at the end of Week-3 during a Salmonella infection?
What complication may occur at the end of Week-3 during a Salmonella infection?
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During the pathogenesis of salmonellosis, what assists Salmonella in evading lysosomal contents?
During the pathogenesis of salmonellosis, what assists Salmonella in evading lysosomal contents?
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Which of the following is associated with the carrier state of Salmonella?
Which of the following is associated with the carrier state of Salmonella?
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What is the primary cause of abortion and miscarriages in pregnant women related to Brucellosis?
What is the primary cause of abortion and miscarriages in pregnant women related to Brucellosis?
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Which of the following is NOT a symptom associated with acute septicemia in Brucellosis?
Which of the following is NOT a symptom associated with acute septicemia in Brucellosis?
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How can Brucellosis primarily be transmitted?
How can Brucellosis primarily be transmitted?
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What type of bacteria is Brucella classified as?
What type of bacteria is Brucella classified as?
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What diagnostic specimen is most useful for detecting Brucellosis?
What diagnostic specimen is most useful for detecting Brucellosis?
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What is a common complication of untreated Brucellosis?
What is a common complication of untreated Brucellosis?
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What serological test is commonly used for diagnosing Brucellosis?
What serological test is commonly used for diagnosing Brucellosis?
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Which bacteria invade the terminal ileum causing necrotic lesions, and may also present with lymphadenopathy?
Which bacteria invade the terminal ileum causing necrotic lesions, and may also present with lymphadenopathy?
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Study Notes
Salmonella Infections
- Four clinical syndromes (gastroenteritis, particular organ system infections, vascular endothelium focal infections, typhoid fever) and a carrier state are associated with Salmonella genus.
- Typhoid fever is caused by Salmonella enterica subspecies typhi, paratyphi A and B.
- Typhoid fever is a human-only disease with no animal reservoirs.
- Transmission occurs via the fecal-oral route from human carriers and contaminated food.
- The incubation period for typhoid fever is 5 to 21 days.
- Salmonella's pathogenesis includes successful evasion of gastric acid, adhesion to the ileocecal region, and invasion of microfold cells in the ileum mucosa.
- Salmonella utilizes the Salmonella Pathogenicity Island 1 gene and the Vi antigen (capsule) to escape phagocytosis.
- Dendritic cells engulf Salmonella, but the bacteria remain within vesicles due to resistance to lysosomal contents.
- Dendritic cells carry Salmonella to mesenteric lymph nodes within the first week.
- Salmonella spread to the blood (primary bacteremia) by the end of the first and second week.
- Salmonella multiply in macrophages of the reticuloendothelial system (RES) - liver (hepatitis), spleen, and bone marrow during the second and third weeks.
- Secondary continuous bacteremia and septicemia occur by the end of the third week, accompanied by fever, hepatosplenomegaly, and gastrointestinal ulceration.
- Salmonella can invade the gallbladder and kidney, causing cholecystitis and nephritis respectively.
- Gallstones contribute to the carrier state.
- The carrier state involves Salmonella remaining in the gallbladder and being released into the small intestine via bile, causing inflammation and ulceration of Peyer's patches.
- The diagnosis of typhoid fever is based on clinical presentation and laboratory tests.
- Early signs of typhoid fever include gradual temperature increase, relative bradycardia, headache, and constipation or diarrhea.
- During the second week, fever persists, unresponsive to antipyretics, and rose-colored skin spots (exanthem) may appear in 30% of cases.
- Week three is characterized by persistent fever, hepatosplenomegaly, gastrointestinal ulceration with bleeding, perforation, and renal disease.
- Typhoid fever without treatment has a mortality rate of approximately 20%.
- Complications of typhoid fever include chronic carrier state, perforation and peritonitis, osteomyelitis, and septicemia.
- Laboratory diagnosis of typhoid fever involves direct microbiology (blood, stool, and urine cultures) and indirect serology (Widal test).
- Blood culture is usually positive during the first week, while stool culture is positive by the third week.
- The Widal test detects anti-Salmonella antibodies in patient sera with a significant titer of 1/160 or higher.
- Treatment for typhoid fever typically involves injectable ciprofloxacin or third-generation cephalosporin with confirmation through sensitivity testing.
- Chronic carriers may require ciprofloxacin and cholecystectomy if the treatment fails.
- Vaccination against typhoid fever is available as an injectable killed or capsular Vi antigen vaccine, and an oral live attenuated vaccine.
Brucellosis (Malta Fever)
- Brucellosis is a zoonotic disease caused by the genus Brucella, with different species affecting different animals (B. abortus in cattle, B. melitensis in goats).
- Transmission occurs via unpasteurized milk or milk products and direct contact with infected animals.
- The incubation period ranges from five days to several months.
- Brucella is a small, Gram-negative coccobacillus, non-capsulated, and non-motile.
- The pathogenesis involves attachment to intestinal microvillus, engulfment by intestinal macrophages, infection of lymph nodes, and spread to the RES, resulting in septicemia.
- Untreated Brucellosis can lead to granulomatous response with central necrosis.
- Symptoms of Brucellosis include fever with night sweats, joint pain, anorexia, weight loss, and localized infections in the bones, heart, and kidneys.
- Brucellosis can cause abortion and miscarriages in pregnant women and is a potential cause of fever of unknown origin (PUO).
- Diagnosis of Brucellosis involves direct culture from bone marrow aspiration, blood, liver biopsy, and serum.
- Culture is performed on biphasic (solid and liquid) Castaneda media or automated systems.
- Brucella grows best on liver extract agar under aerobic conditions and 5-10% CO2 for primary isolation.
- Indirect serological diagnosis involves the Agglutination Brucella test, with a significant titer of 1/80 to 1/160.
- False-negative reactions may occur due to the prozone phenomenon.
Yersinia enterocolitica and Yersinia pseudotuberculosis
- These bacteria cause invasive enteritis and focal infections.
- They invade the terminal ileum, leading to necrotic lesions of Peyer's patches.
- Yersinia is engulfed by dendritic cells, causing invasion of mesenteric lymph nodes and lymphadenopathy.
- Yersinia are Gram-negative, short coccobacilli, motile at 25°C but not motile at 37°C.
- Yersinia exhibits cold growth, growing well at room temperature.
- Diagnosis involves direct blood culture and indirect serological testing to detect anti-Yersinia antibodies in serum.
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Description
This quiz covers key aspects of Salmonella infections, including the clinical syndromes associated with the genus, transmission pathways, and pathogenesis. Learn about typhoid fever, its causative agents, and the immune evasion strategies employed by Salmonella. Test your knowledge on the important details of this significant disease.
