Infections from Salmonella, Shigella, & Yersinia

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Questions and Answers

Which laboratory medium is suitable for the culture of nontyphoidal Salmonella?

Luria-Bertani agar

Nutrient broth

Chocolate agar

Blood agar (correct)

What is a significant characteristic of Shigella in terms of its host interaction?

It has animal reservoirs.

It causes disease mainly through aerosol transmission.

It primarily infects adult populations.

It is an obligate human pathogen. (correct)

What condition is most commonly mimicked by mesenteric lymphadenitis in children?

Acute gastroenteritis

Acute cholecystitis

Acute appendicitis (correct)

Renal colic

Which patient demographic is at highest risk for severe septicemia from conditions discussed?

Immunocompromised individuals Signup and view all the answers

Which serogroup of Shigella has the highest number of serotypes?

Serogroup C Signup and view all the answers

Which of the following characteristics is NOT true for Salmonella?

Lactose fermenter Signup and view all the answers

What is the primary clinical presentation associated with Salmonella Typhi infection?

Enteric fever Signup and view all the answers

Which diagnostic test is typically NOT used for identifying Salmonella?

Blood culture Signup and view all the answers

What kind of infection can develop after typhoid or paratyphoid fever caused by Salmonella?

Asymptomatic colonization Signup and view all the answers

Which serotype of Salmonella is commonly associated with septicemia?

Salmonella Choleraesuis Signup and view all the answers

What is the estimated number of people affected by typhoid fever globally each year?

17 million Signup and view all the answers

Which category does Salmonella Typhimurium belong to?

Nontyphoidal species Signup and view all the answers

Which of the following Salmonella serotypes is considered a serogroup D?

Salmonella Typhi Signup and view all the answers

Which of the following is a common source for non-typhoidal Salmonella infections in humans?

Poultry Signup and view all the answers

What is the typical infective dose for non-typhoidal Salmonella?

1,000,000 organisms Signup and view all the answers

What is a primary prevention method for controlling Typhoid Fever?

Improving sanitary conditions Signup and view all the answers

Which antibiotic treatment is considered essential for managing Typhoid Fever?

Chloramphenicol Signup and view all the answers

What is a characteristic feature of enteritis caused by Salmonella?

No human reservoir Signup and view all the answers

In which week is isolation from blood typically performed for enteric fever diagnosis?

First week Signup and view all the answers

Which of the following symptoms is NOT associated with enteritis caused by Salmonella?

Severe weight loss Signup and view all the answers

What is a potential consequence of using animal feeds containing antimicrobial drugs?

Development of drug-resistant Salmonella Signup and view all the answers

Study Notes

Infections Due to Salmonella, Shigella, and Yersinia

Objectives include describing bacterial agents causing diarrhea, clinical presentation of infections, recommended diagnostics and common findings, and treatment and management.
Salmonella is a serious public health problem in both developing and developed countries.
Salmonella is a Gram-negative rod-shaped, facultative bacterium, belonging to the Enterobacteriaceae family.
It is catalase-positive, oxidase-, and lactose-non-fermenting.
It typically resides in the large intestine.
Salmonella morphology includes Gram-negative rod shape, facultative bacterium, belonging to the Enterobacteriaceae family, catalase-positive, oxidase-positive, and H2S+. Colonies appear as blue-colored on certain agars (e.g., Hectoen-Enteric agar, Bismuth sulfide agar).
Salmonella is classified into 2500 serotypes, with two main species: S. enterica and S. bangori.
Clinical Salmonella serotypes include Paratyphi A (serogroup A), Paratyphi B (serogroup B), Typhi (serogroup D), Choleraesuis (serogroup C1), and Typhimurium (serogroup B).
Typhoid fever (caused by S. Typhi) is a life-threatening infection affecting 17 million people annually, resulting in 600,000 deaths. S. Paratyphi causes milder infection.
Typhoid fever is common in children under 5 in developing countries.
Transmission occurs through contaminated food and water, specifically via feces and urine of infected patients or carriers. Food handlers can act as carriers.
The pathogen invades the intestines, causing intracellular multiplication in cells of the reticuloendothelial system, eventually leading to systemic infection and/or localized infection.
Laboratory diagnosis for Enterocolitis involves stool culture, identification by biochemical tests (seroagglutination), and phage typing. Enteric fever diagnosis includes blood and urine (2-3 weeks post infection) culture, stool culture (1 week post infection). Serology (Widal test) can be unreliable.
Prevention strategies include controlling the human reservoir, improving water and food sanitation, and vaccination (though currently licensed Vi polysaccharide vaccines are not highly effective).
Therapy for typhoid fever involves antibiotics like chloramphenicol, ampicillin, or TMP-SXT. If resistance is observed, quinolone or 3rd-generation cephalosporins can be used.
Therapy for Enterocolitis often does not require antibiotics, but antibiotics like ciprofloxacin might be required for severe cases, especially in immunocompromised or elderly individuals.

Shigella

Classified into serogroups A, B, C, and D, differentiated by biochemical tests and antigenic characteristics.
Shigella is a strictly human pathogen, unlike Salmonella which has animal reservoirs.
Transmission is fecal-oral, with a low infective dose (< 103 organisms).
It causes bacillary dysentery (shigellosis), characterized by bloody diarrhea, intestinal pain, and pus in feces.
Clinical presentation is very similar to salmonella infection but can involve severe complications.
Laboratory diagnosis involves culturing fresh stool samples on selective media (MacConkey agar, SS agar) and microscopic examination looking for lactose-negative (except S. sonnei) and deoxycholate-resistant colonies.
Treatment involves managing dehydration and using antibiotics such as TMP-SXT or quinolones (for adults), Ceftriaxone .

Yersinia

Yersinia is an animal parasite transmissible to humans directly or via insect vectors.
It grows at 14-37°C (27°C) and is non-haemolytic.
Three human pathogens within the Yersinia genus are Y. pestis, Y. enterocolitica and Y. pseudotuberculosis.
Y. enterocolitica causes Enterocolitis, usually from contaminated, refrigerated food and blood products.
Y. pseudotuberculosis causes a less severe disease, sometimes mimicking acute appendicitis.
Y. pestis is the causative agent of plague (Black Death). It is endemic in some parts of the world, transmitted via infected fleas to humans, resulting in bubonic (painful, swollen lymph nodes), pneumonic (highly contagious droplets, infectious), and septicemic (bloodstream, fatal) forms.
Laboratory diagnosis involves culturing at 27°C on blood agar or MacConkey agar using methylene blue stain for visualization.
Treatment involves using antibiotics like tetracycline immediately upon suspicion of plague.

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Description

This quiz explores infections caused by Salmonella, Shigella, and Yersinia, focusing on the clinical manifestations, diagnostic methods, and treatment options. Learn about the various serotypes of Salmonella and their public health implications, as well as the necessary management strategies for these bacterial infections.