2ba

Question 1

Closely related to Escherichia – both belong to the same tribe, Escherichieae

Answer 1

Shigella

Question 2

– not members of the GI microbiota, and are considered as “primary pathogens”

Answer 2

Shigella

Question 3

Shigella

All species causes

Answer 3

dysentery (bloody diarrhea with mucus, blood, and leukocytes)

Question 4

Shigella

Biochemical characteristics:
§ fermenters
§ motile?
§ Anaerogenic, except____
§ Do not hyrdrolyse____
§ Do not produce____
§ Do not___ lysine
§ Do not use ______as carbon source

Answer 4

Non-lactose

Non-motile

Shigella flexneri

urea

H2S

decarboxylate

acetate or mucate

Question 5

Biochemically inert

Answer 5

Shigella

Question 6

Shigella
– unique member of the genus
§ Ability to ferment lactose slowly (LLF)

producing pink colonies on MAC agar only after 48 hours of incubation

§ ONPG positive

Answer 6

Shigella sonnei

Question 7

Shigella species – fragile and susceptible to various effects of physical and chemical
agents:

Answer 7

§ Disinfectants
§ High concentrations of acids and bile

Question 8

Differentiate sonnei with other members of the genus

Answer 8

LLF

Question 9

are susceptible to the acid pH of
the stool. Feces suspected of containing ____ spp., must be immediately inoculated to primary culture media to increase recovery of the organisms

Answer 9

Shigella

Question 10

All Shigella species – possess____ antigens, and certain strains possess___ antigens

Answer 10

O

K

Question 11

if present, interfere with the detection of the O antigen during serologic grouping.

Answer 11

K antigens (capsular)

Question 12

Does shigella have H antigen?

Answer 12

No! Non motile!

Question 13

Shigella
Serotypes based on their O antigen
Subgroup A–
Subgroup B–
Subgroup C–
Subgroup D–

Answer 13

S. dysenteriae (Dysentery bacillus)

S. flexneri (Strong’s bacillus)

S. boydii (S. ambigua)

S. sonnei

Question 14

Shigella sp (-) for Mannitol fermentation

Answer 14

S. dysenteriae

Question 15

Shigella sp (+) Ornithine decarboxylase

Answer 15

S. sonnei

Question 16

Shigella
Mode of Transmission
(2)are the only known reservoir!

Answer 16

Humans and other large primates

Question 17

Shigella
Mode of Transmission

Mode of transmission:

May also be transmitted by

…plays a major role in the transmission

Answer 17

direct person-to-person contact,
fecal-oral-route with carriers as the source.

flies, fingers, and food and water contaminated by infected persons

Personal hygiene

Question 18

cause all types of bacillary dysentery– painful type of diarrhea characterized by watery feces w/ mucus, blood streaks & pus cells

Answer 18

Shigella species

Question 19

Shigella

Infective dose: as low as____ bacilli are needed to initiate the disease in some healthy individuals.

Answer 19

100

Question 20

– predominant in the U.S and other industrialized countries

– affects mostly young children. Leading isolate of gastroenteritis among ^men who have sex with men.* HIV infections increases this risk.

§ ____ and ____are the most common isolates in developing countries.

_____remains the most virulence of all the species with a significantly high
morbidity and mortality rate

Answer 20

§ S.sonnei

§ S. flexneri

S.dysenteriae type 1 and S.boydii

S.dysenteriae type 1

Question 21

– attach to and invade the M cells located in Peyer patches.

Answer 21

Shigella

Question 22

The organism secretes four invasion-plasmid antigen (Ipa)
proteins into epithelial cells and macrophages that induce
membrane ruffling on the target cell, leading to engulfment
of bacteria. These proteins include:
§ IpaA
§ IpaB
§ IpaC
§ IpaD

Answer 22

Shigella

Question 23

– lyses the phagocytic vacuole and replicate in the cytoplasm.

Answer 23

Shigella

Question 24

The rearrangement of actin filaments in the host cells propel the bacteria through the cytoplasm through the adjacent cells where cell- to-cell passage occurs.

§ Cell-to-cell passage protects it from immune-mediated clearance.

§ They survive phagocytosis by inducing apoptosis. Apoptotic phagocytes release IL1B that acts as a chemoattractant for
PMNs into the infected tissues. This destabilizes the integrity of the intestinal wall and allows bacteria to reach the deeper epithelial cells

Answer 24

Shigella

Question 25

– produces shiga toxins, similar to the verotoxins produced by EHEC.

Answer 25

Shigella dysenteriae

Question 26

Shigella dysenteriae – produces shiga toxins, similar to the verotoxins produced by EHEC. ______binds to the host cell glycolipid Gb3 receptor and facilitate the transfer of the A subunit into the cell. The______ cleaves the 28S rRNA in the 60S ribosomal subunit, resulting in the disruption of protein synthesis resulting in cell damage and death.

Answer 26

The B subunit A subunit

Question 27

High concentrations of____ are found on intestinal villi and renal endothelial cells. This results in hemorrhagic diarrhea and hemolytic uremic syndrome (HUS)

Answer 27

Gb3

Question 28

– enrichment medium for the isolation of Salmonella spp., and Shigella species from heavily contaminated specimens such as stool.

Answer 28

Selenite broth

Question 29

Many_____ serotypes are typically found in cold-blooded animals as well as in rodents and in birds, which serve as their natural hosts.

Answer 29

Salmonella

Question 30

On selective and differential media –______ produce clear, colorless, non-lactose fermenting colonies. § Colonies with black centers are seen in media with sodium thiosulfate such as HEA, SSA, and XLD § Black precipitates indicate H2S production.

Answer 30

Salmonellae

Question 31

Salmonella – Non-motile All are NLF –except for_____ All are aerogenic – except_____ All are H2S positive –except_____

Answer 31

S.pullorum and S. gallinarum Salmonella Arizona -LLF Salmonella Typhi Salmonella Paratyphi

Question 32

Salmonella Antigenic Structures and Virulence Factors ______: Stable to boiling and acid alcohol ______: More stable ______ are the primary antigenic structures ______: Virulence Ag (K antigen); occurs in ***Salmonella serotype Typhi and a few strains of Salmonella serotype Cholerasius*** § Plays a role in preventing phagocytosis

Answer 32

O Ag H Ag § O and H Vi Ag

Question 33

Salmonella - invasiveness (enables them to traverse the intestinal mucosa); endotoxin, enterotoxins, intracellular capability – for adhesion

Answer 33

Surface Ag’s Fimbriae

Question 34

Salmonella Classification Formerly, there are only 3 known species:

Answer 34

S.enteritidis S. cholerasius S.typhi

Question 35

– also known as the Gardner’s bacillus; formerly S.typhosa is also known as the Eberth’s bacillus

Answer 35

S.enteritidis S.typhi

Question 36

Salmonella Genetic studies have shown that the three previously named species are genetically related and that there are only 2 designated species; _______ (Type species of the genus); and with 6 subspecies. _______(rare isolate) – initially isolated from a lizard and is usually isolated from cold-blooded animals and the environment

Answer 36

§ S.enterica § S,bongori

Question 37

Typhoid fever, the most severe form of enteric fever, caused by_______, and enteric fevers caused by other serotypes such as (2)

Answer 37

Salmonella serotype Typhi Salmonella serotype Paratyhpi and Salmonella serotype Cholerasius.

Question 38

§ Except for (2), Salmonella infect animals that serve as their reservoir § (2)have no known animal reservoirs and infections only occurs in humans. Carriers are often the source of infection

Answer 38

Salmonella Typhi and Salmonella Paratyphi Salmonella Typhi and Salmonella Paratyphi

Question 39

Salmonella Source of infection have been attributed to poultry, milk, eggs, and egg products, as well as to handling pets. Insufficiently cooked eggs and domestic fowl, such as chicken, turkey, and duck and common sources of infection.

Answer 39

Gastroenteritis

Question 40

Salmonella Outbreaks associated with consumptions of foodstuffs such as peanut butter, cantaloupe, puffed rice and wheat cereals, corn-and vegetable-coated snacks, vegan cheese, alfalfa sprouts, cucumber, and raw tomatoes. Cross –contamination through cooking utensils also occur

Answer 40

Gastroenteritis

Question 41

Salmonella Also known as_____ – a febrile disease that results from the ingestion of food contaminated with organisms originating from infected individuals or asymptomatic carriers.

Answer 41

Enteric Fever typhoid fever

Question 42

Salmonella When organisms are ingested – they are resistant to gastric acid Upon reaching the proximal end of the small intestine, they invade and penetrate the intestinal mucosa – patients suffer constipation instead of diarrhea Organisms gain entrance to the lymphatic system and are sustained in the mesenteric lymph nodes. They eventually reach the blood stream and spread to the liver, spleen, and bone marrow, where they are immediately engulfed by mononuclear phagocytes. Organisms multiply intracellularly inside phagocytes and are released in the blood stream for the second time. This results to febrile episode and the organism can be easily isolated from bloo

Answer 42

ENTERIC FEVER 1st Week of infection

Question 43

Salmonella Patient generally sustained fever with prolonged bacteremia The organism invade the gall bladder and the Peyer’s patches of the bowel. They also reach the intestinal tract via the biliary tract. “Rose-spots” - blanching rose-colored papules around the umbilical region also appear during the second week of fever. Involvement of the biliary system initiates GI symptoms as the organisms reinfect the intestinal tract. The organism now exists in large number in the bowel and may be isolated from the stool

Answer 43

ENTERIC FEVER 2nd and 3rd Weeks of Infection

Question 44

Salmonella For asymptomatic carriers, the gallbladder becomes the foci of long- term carriage of the organism From the gallbladder of carriers, the organism is occasionally/intermittently shed in the feces which then result in the spread of infection via fecal-oral route. They become important sources of infections for susceptible persons

Answer 44

Enteric Fever Asymptomatic Carriers

Question 45

Salmonella Specimen Collection and Laboratory Diagnosis – 1st and 2nd week – 3rd and subsequent weeks – can be used indefinitely as clinical specimen NOTE:_____ is the best diagnostic procedure to identify Salmonella

Answer 45

Blood Urine/Stool Stool Culture

Question 46

: “Metallic colonies with a black ring” on BSA

Answer 46

S. Typhi

Question 47

Serologic test that detects the presence of antibodies in the person’s serum against O and H antigens of Salmonella Typhi.

Answer 47

Widal Test

Question 48

Widal Test Interpretation: Titer of______ or more for O agglutinins and_____ or more for H agglutinin should be considered clinically significant as these indicate active infection.

Answer 48

1:100 1:200