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What is the characteristic shape of Salmonella bacteria?
Which of the following is NOT a mode of transmission of Salmonella?
What is the preferred method of diagnosis in the first week of illness?
What is the term for the bacterial infections caused by species of Salmonella?
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Which of the following Salmonella strains does not produce hydrogen sulfide?
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Which of the following groups of Salmonella is associated with Enteric fever?
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What is the function of the Type III secretion system (TTSS) encoded by SPI-1?
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What is the term for individuals who have natural immunity to Salmonella and contract only mild or asymptomatic disease?
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What is the purpose of the Salmonella-containing vacuole?
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Which of the following is a characteristic of Salmonella bacteria?
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Which of the following is NOT a recommended treatment for Salmonella infection?
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What is the name of the oral live attenuated vaccine against S.Typhi?
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What is the primary mode of transmission of S.typhi and paratyphi?
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Which Salmonella serovar is the most common cause of food poisoning?
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What is the term for the individuals who can be infected by chronic carriers, especially the elderly, infants, and immunocompromised patients?
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What is the duration of Salmonella infection in immunocompetent individuals?
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What is the primary difference between S. Enteritidis and S. Typhimurium?
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What happens when Salmonella infects chicken flocks?
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What is the function of the Vi antigen?
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What is the basis of the Kauffmann-White scheme for Salmonella classification?
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What is the purpose of adding Poly-O antisera to the suspension in the Kauffmann-White scheme?
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What is the effect of boiling on the H antigen?
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What is the characteristic of the O antigen?
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What is the purpose of repeating the process with O4 and O16 antisera in the Kauffmann-White scheme?
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What was the occupation of the person responsible for several typhoid outbreaks in New York in the early 1900s?
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How many people were infected with typhoid due to the actions of the cook in New York?
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What was the condition for the cook's release from the isolation center on North Brother Island in 1910?
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What is the correct taxonomic name for the organism that causes typhoid fever?
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What is the incubation period of typhoid and paratyphoid infections?
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What is the primary reservoir for Salmonella typhi?
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What is the term for the combined name of typhoid fever and paratyphoid fever?
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What is the primary mode of transmission of Salmonella typhi?
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What method can be used to determine the serotype of an organism?
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What is the problem associated with Salmonella Typhimurium DT104?
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What is the role of marA in Salmonella?
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Why is Salmonellosis a reportable disease?
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What is the role of food handlers in the spread of Salmonellosis?
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How many organisms of Shigella are required to cause disease?
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Where is Shigella typically found?
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How long can carriers of pathogenic Shigella strains excrete the organism?
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Study Notes
Non-Lactose Fermenters (Salmonella, Shigella, Yersinia)
Salmonella
- Gram-negative, rod-shaped, facultatively anaerobic bacterium
- Motile by peritrichous flagella
- Zoonotic, causes economically important disease in humans and livestock
- Causes:
- Enteric fever (Typhoid fever)
- Gastroenteritis
- Septicemias
- Carrier state
- Divided into 2 groups:
- Enteric fever group
- Food-poisoning group
- Habitat:
- S.typhi and paratyphi: only found in humans, not part of normal flora of the bowel
- Other Salmonella spp.: widely disseminated in nature, associated with various animals
- Mode of transmission:
- S.typhi and paratyphi: person-to-person spread by fecal-oral route, ingestion of contaminated food or water
- Other Salmonella spp.: ingestion of contaminated food products, direct person-to-person transmission in healthcare settings
- Carrier state: natural reservoir for the disease, "chronic carriers" contract only mild or asymptomatic disease, but still carry the bacteria in their body for a long time
Typhoid Fever (Salmonella Typhi)
- Caused by Salmonella enterica serovar Typhi
- Incubation period: 6-30 days
- Symptoms: nausea, vomiting, fever, and death
- Can only infect humans, no other host identified
- Septicemia (particularly S.choleraesuis, S.typhi, and S.paratyphi)
- Asymptomatic carriage (gall bladder is the reservoir for Salmonella typhi)
- Lab diagnosis: stool culture not usually positive during the first week of illness, so blood culture is preferred
- S.Typhi: gas not produced during fermentation, K/A+
- Virulence factors:
- Type III secretion system (TTSS)
- Acid resistance
- Salmonella-containing vacuole
Treatment and Prevention
- Fluoroquinolones (such as ciprofloxacin), azithromycin, and ceftriaxone
- Prevention: safe food and water precautions, vaccine (ViCPS, Typhim Vi, and Vivotif)
Salmonella enterica serovar Typhimurium
- Most common cause of food poisoning by Salmonella species
- Causes diarrhea, abdominal cramps, vomiting, and nausea, generally lasting up to 7 days
- Can be fatal in immunocompromised people if not treated with antibiotics
Salmonella Antigenic Structure
- H - Flagella Ag: heat-labile, boiling destroys antigenicity, strongly immunogenic
- O - Somatic Ag: forms integral part of the cell wall, unaffected by boiling, less immunogenic than H Ag
- Vi - Surface Ag (Capsular): covers the O Ag, destroyed by boiling at 60°C for 1 hour, a virulence factor
Salmonella Serotyping
- Classification based on the Kauffmann-White scheme using somatic (O) and flagellar (H) antigens
- Method: using Poly-O and Poly-H antisera, and the Kauffman & White book to determine the serotype
Pathogenesis and Clinical Disease
- Molecular typing methods: phage typing, antibiotic-resistant typing, PCR-based methods, pulsed-field gel electrophoresis (PFGE), and plasmid typing
- Antibiotic resistance: AcrAB, SoxRS, and MarAB implicated in chromosomal-based resistance
- Epidemic measures: reportable disease, prevalent in countries with poor water supply and sanitation, food handlers play a great role in its spread
Shigella
- One of the most infectious bacteria, ingestion of as few as 100 to 200 organisms can cause disease
- Habitat: only found in human GIT at times of infections, not part of normal bowel flora
- Transmission: person-to-person via fecal-oral route, especially in overcrowded areas and areas with poor sanitary conditions
- Carriers of pathogenic strains can excrete the organism up to two weeks after infection and occasionally for longer periods
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Description
This quiz covers non-lactose fermenters, specifically Salmonella, Shigella, and Yersinia, and their characteristics, including shape, motility, and disease causes.
