Salmonella Flashcards
Why the classification of salmonella is very difficult?
Because there are more than 2500 types and some strains lose the motility, Vi antigen or O antigen.
On the basis of which antigen serotyping is done?
O antigen
How we’re going to classify them?
Those that cause the typhoid fever and those that cause the nontyphoidal salmonellosis
How salmonella typhi and paratyphi are transmitted?
- Fecal oral route
- Through the laboratory
Who are the reservoir?
Humans
Where bacteria are found in carriers?
In the gallbladder, the bile, and even in stones
Where bacteria are excreted? What do they contaminate?
From time to time, bacteria leave the gallbladder, and they are excreted in stool.
Feces can contaminate hands, water, food.
What are the clinical presentations?
Asymptomatic carriers
Typhoid fever
On what depends the infectious dose?
It is small if the person is taking antacids, or if intestines are perforated (frequent aspirin takes leads to ulcers in the intestines)
It is large otherwise
What’s the incubation period?
3 to 21 days
It depends on the host and the amount of ingested bacteria, the lesser the amount ingested the longer the incubated period.
How bacteria will cause a primary transient bacteremia?
The large inoculum overcomes the acidity of the stomach, bacteria penetrate to the submucosal layer of the intestine, then go in monocytes and macrophages causing primary transient bacteremia.
Is there symptoms during the primary transient bacteremia?
No it is asymptomatic
How bacteria spread anywhere in the body?
Bacteria take the control in monocytes and macrophages changing many of the proteins in these cells so they can multiply. Bacteria can thus spread anywhere in the body using macrophages as a way of transport.
Where do bacteria go?
They go to the reticuloendothelial system formed by the liver, the spleen, the lymph nodes, and the bone marrow.
How secondary persistent bacteremia occurs?
Bacteria will multiply in the reticuloendothelial system, then a flow of bacteria will pass to the blood causing is secondary persistent bacteremia.
What are the nonspecific GI symptoms?
Sore throat, nausea, sometimes vomiting, constipation for a few days that might be followed by a diarrhea
What are the specific symptoms?
High fever of 39 to 40.5°C for 4 to 8 weeks caused by monokines, hepatosplenomegaly caused by recruitment of mononuclear cells in the spleen and liver where bacteria are present, severe anorexia leading to weight loss, change of sensorium (hallucinations because of the high fever), 5 to 6 days after these manifestations, the patient develops rose spots on the abdomen which contains the bacteria, relative bradycardia.
The least symptoms are the intestinal ones
What are the complications?
Meningitis that participates in the change of sensorium
Pneumonia
Involvement of bones and joints (osteomyelitis)
UTI: S. Typhi and paratyphi cannot cause a UTI directly, but since they are motile, so whenever bacteria are being excreted in stool, they can reach the urinary tract.
The worst complication is that related to the vascular system
What do we have in the complete blood count?
The WBC count can be normal, but we usually have leukopenia.
Individuals with intestinal perforations might be infected by other bacteria leading to leukocytosis.
Anemia because of anorexia, it’s worse in the case of intestinal perforations.
What is their selective medium?
D SS medium
How they are detected after culture?
They are more tile as opposed to shigella
They are H2S producers as opposed to shigella
They are lactose non-fermenting as opposed to E. coli
Which specimen is taken in the first week?
We find bacteria in more than 80% in the blood of disease individuals. Then the amount in blood decreases.
Which specimen should be taken in the second and third weeks?
Bacteria is present in the stool mostly in the third week then the amount in stool decreases
Where it is always found?
It is always present in the CSF whether there is meningitis or not and in the rose spots.
Which test is used in serology?
The Widal test which is an agglutination test
Which antibodies does it detect?
It detects antibodies against the O somatic antigen, the H antigen and the Vi capsular antigen
When each type of antibodies is detected?
Antibodies of the O somatic antigen are detected earliest, then we detect antibodies for the H antigen, then those for the Vi antigen.
Is there a permanent immunity?
Antibodies that are developed do not give a lifelong immunity.
Which antibiotic was the drug of choice in the past?
Chloramphenicol
What is the drug of choice now?
Ceftriaxone given IM for 10 to 14 days
How many vaccines there is?
There are 3 types of vaccines and they all give immunity not for more than five or six years.
What are the three types of vaccines? From what is prepared each one?
- heat killed, prepared from the whole bacteria containing antigens without the nucleic acid
- Ty 21 A, prepared from the live attenuated bacteria that can multiply in the system
- Vi CSP, prepared from the capsular polysaccharides
How Salmonella typhimurium and enteriditis are transmitted?
- Ingestion (fried and frozen food, eggs)
- Contact with infected animals
- Fecal oral route
Who are the reservoirs?
Humans and animals (hen, chicks, ducks and turtles)
How bacteria are transmitted from animals to humans?
Bacteria can infect hen and hen can infect the eggs either while these are being produced in their system or during laying (bacteria are deposited on the shell, and they can penetrate it)
At the time of infection of the egg the amount of bacteria might be small, but it can increase if left at room temperature for 18 to 24 hours. Even cooking cannot destroy this large amount of bacteria.
How bacteria are transmitted due to humans?
Since bacteria is excreted even after recovery, so it can be transmitted from carriers.
What is the clinical presentation?
Gastroenteritis
What is the infectious dose?
a very small inoculum is needed because the disease
What’s the incubation period?
6 to 48 hours after ingestion
Where bacteria are absorbed? Where does it migrate?
By epithelial cells in the terminal portion of the small intestine
Bacteria migrate to the lamina propria layer of the ileocecal region.
Where does bacteria multiply? What do they cause?
Bacteria multiply in lymphoid follicles causing reticuloendothelial hyperplasia and hypertrophy
Which immune cells are involved in the case of salmonellosis?
PMN are involved
What is the cause of manifestations?
The overproduction of cytokines by neutrophils
What is the simplest outcome?
Diarrhea, which starts as watery and mucoid diarrhea and progresses to a bloody type because of the inflammation of the colon (dysentery)
What occurs with diarrhea?
Fever, abdominal cramps and lots of PMN in stool
What are the complications in non-AIDS patients?
Focal abscesses in different organs like the spleen
Arterial system infection (arteritis)
Abscess and deposit of bacteria in joints causing septic arthritis. In many cases drainage is necessary.
Osteomyelitis in the terminal parts of long bones (like with Staph aureus)
Pneumonia, UTI and meningitis are much less common
What are complications in AIDS patients?
There is always bacteremia and sepsis whether or not diarrhea is present. Manifestations are recurrent. bacteremia and sepsis of salmonellosis are among the first manifestations in AIDS patients.
From where the specimen is taken?
From the stool
What is the result of the culture?
They are motile, H2S producers, non-lactose fermenting.
Does the disease cause lifelong immunity?
No
What is the treatment? Is there any vaccine?
Supportive care (fluid and electrolytes) is the best treatment No vaccine
