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Microbiology A > Salmonella > Flashcards

Salmonella Flashcards

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1
Q

Who discovered the genus Salmonella and in what year?

A

Salmon and Smith in 1885

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2
Q

What family do Salmonella belong to?

A

Enterobacteriaceae

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3
Q

What are the main diseases caused by Salmonella in humans?

A
  • Enteric fever
  • Gastroenteritis
  • Septicemia
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4
Q

How many serotypes of Salmonella are currently recognized?

A

Above 2463 serotypes

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5
Q

What is the nickname of Mary Mallon and why?

A

Typhoid Mary; she was a healthy carrier of Salmonella typhi

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6
Q

What are the morphological characteristics of Salmonella?

A
  • Gram-negative bacilli
  • Size: 2-4 × 0.6 μm
  • Motile with peritrichous flagella (except S. gallinarum and S. pullorum)
  • Non-capsulate
  • Non-sporing
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7
Q

What temperature range can Salmonella grow in?

A

15°C to 45°C (optimum 37°C)

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8
Q

What is the appearance of Salmonella colonies on MacConkey Agar?

A

1-3mm in diameter, pale yellow or nearly colorless

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9
Q

What are the two clinical classifications of Salmonella?

A
  • Typhoidal Salmonella
  • Non-typhoidal Salmonella (NTS)
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10
Q

What are the two species of Salmonella classified by DNA hybridization studies?

A
  • Salmonella enterica
  • Salmonella bongori
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11
Q

Name the three important antigens present in Salmonella.

A
  • Flagellar H antigen
  • Somatic O antigen
  • Surface antigen Vi
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12
Q

What is the Vi antigen, and which serotypes express it?

A

A surface polysaccharide envelope; expressed in S. typhi, S. paratyphi C, S. dublin

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13
Q

True or False: The O antigen is more immunogenic than the H antigen.

A

False

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14
Q

What are the four types of selective media for isolating Salmonella?

A
  • MacConkey Agar
  • Brilliant Green MacConkey Agar
  • Deoxycholate-Citrate Agar (DCA)
  • Xylose Lysine Deoxycholate (XLD) Agar
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15
Q

What are the risk factors that promote transmission of Salmonella?

A
  • Stomach acidity
  • Intestinal integrity
  • Poor sanitation
  • Improper cleaning of drinking water, food and drinks
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16
Q

What are common clinical signs of typhoidal salmonella infection?

A
  • Fever
  • Headache
  • Chills
  • Cough
  • Sweating
  • Myalgia
  • Rashes/rose spots
17
Q

What specimens are used for diagnosing enteric fever?

A
  • Blood
  • Feces
  • Urine
  • Bone marrow
  • Duodenal drainage
18
Q

What biochemical reactions are characteristic of Salmonella?

A
  • Catalase positive
  • Oxidase negative
  • Nitrate reduction positive
  • Ferment glucose and mannitol but not lactose or sucrose
19
Q

What is the treatment for enteric fever?

A

Safe drinking water, proper food hygiene, sanitary sewage disposal, treatment of carriers

20
Q

What are the two major non-typhoidal Salmonella serotypes causing infections?

A
  • S. typhimurium
  • S. enteritidis
21
Q

What is the primary source of non-typhoidal Salmonella infections?

A

Animal food products, especially eggs and poultry

22
Q

Fill in the blank: Salmonella can be transmitted through _______.

A

[contaminated food or water]

23
Q

Name a method used to detect carriers of Salmonella.

A
  • Stool and bile culture
  • Urine culture
24
Q

What is the incubation period for Salmonella infections?

A

7 to 14 days

25
Q

What is the effect of mercuric chloride on Salmonella?

A

Kills within 5 minutes

26
Q

True or False: Non-typhoidal Salmonella are strictly human pathogens.

A

False

27
Q

What is the clinical manifestation of gastroenteritis caused by non-typhoidal Salmonella?

A

Massive neutrophil infiltration into intestinal mucosa

28
Q

What are the most common sources of Non Typhoidal Salmonellae (NTS)?

A

Animal food products, especially eggs, poultry, undercooked ground meat, and dairy products

NTS are acquired from multiple animal reservoirs, making them zoonotic.

29
Q

What characterizes Typhoidal Salmonellae?

A

Strictly human pathogens and mainly waterborne

Typhoidal Salmonellae do not typically originate from animal sources.

30
Q

What are the risk factors for bacteremia associated with Non Typhoidal Salmonellae?

A

NTS serotype, age, and low immunity conditions

Common NTS serotypes include S. Choleraesuis (from pigs) and S. Dublin (from cattle).

31
Q

Which age groups are at higher risk for NTS bacteremia?

A

Infants and elderly people

These groups often have weaker immune responses.

32
Q

What are the clinical manifestations of Non Typhoidal Salmonellae infection?

A

Gastroenteritis characterized by nausea, vomiting, watery diarrhea, fever

Abdominal cramps typically onset 6-48 hours after ingestion of contaminated food.

33
Q

What percentage of patients with NTS gastroenteritis may develop bacteremia?

A

Up to 8%

Bacteremia can lead to endovascular infection or metastasis to various organs.

34
Q

List some types of metastatic localized infections caused by NTS.

A
  • Intra-abdominal infections (e.g., hepatic or splenic abscesses)
  • NTS meningitis (commonly in infants)
  • Pulmonary infections (e.g., lobar pneumonia)
  • UTI (e.g., pyelonephritis and cystitis)
  • Genital tract infections (e.g., ovarian, testicular abscesses)
  • Salmonella osteomyelitis

Sickle cell disease is commonly associated with Salmonella osteomyelitis.

35
Q

What is the standard treatment for uncomplicated NTS gastroenteritis?

A

Conservative treatment with fluid replacement

Antibiotic use can increase rates of carriers and relapse.

36
Q

What antibiotic is given for presumptive treatment of severe NTS gastroenteritis?

A

Ciprofloxacin

Ceftriaxone is indicated for bacteremia and invasive infections.

37
Q

How do drug resistance patterns of NTS compare to typhoidal salmonellae?

A

NTS are more drug resistant than typhoidal salmonellae

MDR strains of NTS are resistant to more than 5 drugs (ACSSuT).

38
Q

What causes the emergence of resistance to ceftriaxone in NTS?

A

Production of AmpC B-lactamases

This resistance is linked to increased use of ceftriaxone for treatment.

39
Q

What genetic change leads to resistance to ciprofloxacin in NTS?

A

Point mutation in DNA gyrase

This mutation is a mechanism that allows NTS to survive despite treatment.

Microbiology A (2 decks)

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