Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
68 Cards in this Set
- Front
- Back
|
Salmonella
|
A type of enterobacteriaceae; two species: Salmonella bongori (no disease caused and Salmonella enterica subdivided into six subgroups.)
|
|
|
Most human infections with Salmonella are caused by which specific type?
|
Salmonella enterica, subspecies enterica.
|
|
|
Salmonella enterica subspecies enterica ser typhi is also called what?
|
Salmonella typhi
|
|
|
What are the three clinical syndromes caused by Salmonella?
|
Typhoid fever and enteric fevers, gastroenteritis (common-50,000 cases reported annually in USA), and septicemia (rare).
|
|
|
Typhoid fever
|
Disease caused by Salmonella which is a type of Enterobacteriaceae. It is rare is the US though one should suspect this disease if the patient presents with a history of travel to endemic areas like India, South and Central America and Asia.
|
|
|
Pathogenesis of Typhoid Fever
|
In contrast to other Salmonella (Enterobacteriaceae) infections, bacteria pass through cells lining the intestines and and are engulfed by macrophages. Organisms then transported to bone marrow, liver, spleen (sinusoids) and replicate. 10-14 days after ingestion there is a gradually increasing fever with headache, myalgias, malaise and anorexia. (This is the initial bacteremic phase) which is followed by colonization of gallbladder and then reinfection of intestines.
|
|
|
Cultures to look for in Typhoid fever
|
Bacteremia-look for blood cultures; kidney infection look for urine cultures, skin-septic infarcts in skin.
|
|
|
How is the organism which caused Typhoid fever (Salmonella) maintained in the human population?
|
Asymptomatic carriage; There is chronic carriage for more than one year after symptomatic disease develops in 1-5% of patients (gallbladder most common carriage site.)
|
|
|
When does Typhoid fever occur?
|
When there is food or water contaminated by infected food handlers and then it is ingested; There is NO animal reservoir for this disease.
|
|
|
Most common form of Salmonellosis is what?
|
Gastroenteritis.
|
|
|
Common routes of infection with Salmonella causing gastroenteritis are:
|
Contaminated food, drink (raw poultry) and contact with fecal material from pet reptiles like turtles, snakes, lizards.
|
|
|
Salmonella species are protected from stomach acid and acid pH of phagosome by what?
|
Acid tolerance response gene. ATR gene.
|
|
|
Salmonella is able to invade and replicate in cells lining what?
|
The terminal portion of the small intestine.
|
|
|
Adherence of bacteria to microvilli on cell surface is mediated by what?
|
Type three secretion system which stimulates rearrangement of actin (ruffling) with subsequent engulfment of bacteria within endocytic vesicles. Bacteria remain in vesicles and replicate until the cell is lysed. Catalase and superoxide dismutase protect bacteria from intracellular killing.
|
|
|
The inflammatory response confines Salmonella infection the the GI tract and mediates the release of what?
|
Prostaglandins and also stimulates cAMP and active fluid secretion.
|
|
|
Salmonella is found where?
|
In all animals-poultry, reptiles, livestock, rodents, domestic animals, birds and humans.
|
|
|
What is the most common source of human infections with Salmonella?
|
poultry, eggs, dairy products, foods prepared on contaminated work surfaces like cutting boards where uncooked chicken was prepared.
|
|
|
In order for a symptomatic disease to occur with Salmonella what is required?
|
A large 10^6 to 10^8 required.
|
|
|
Where does Salmonella multiply?
|
In improperly stored or contaminated foods so a small inoculum can become a large ingested dose.
|
|
|
The infective dose for Salmonella is reduced in which populations?
|
Elderly, immunosupressed or underlying disease like leukemia, lymphoma, sickle cell or REDUCED GASTRIC ACIDITY.
|
|
|
What is the clinical syndrome of gastroenteritis caused by Salmonella?
|
Symptoms appear 6-48 hours after consumption of contaminated food or water, initial presentation nausea, vomiting and non-bloody diarrhea. Fever, abdominal cramps, myalgias and headache also common. Mild, self limited symptoms can persist from 2 days to 1 week. In infants or immunocompromised disease may be severe.
|
|
|
Septicemia caused by Salmonella is uncommon except for which kinds?
|
Salmonella typhi and uncommon serotypes of Salmonella enterica subspecies enterica.
|
|
|
What are the four species of Shigella?
|
Shigella dysenteriae, S. flexneri, S. boydii and S. sonnei (which is the only common cause of shigellosis in the developed world).
|
|
|
Epidemiological facts about Shigella (type of Enterobacteriaceae)
|
primarily a pediatric disease (majority of cases occur in children between ages 1-10); epidemic outbreaks occur in day care centers, nurseries and custodial centers, transmission is by fecal oral route, primarily in people with contaminated hands, less commonly in water or food. Low infectious dose (less than 100 organisms) required for infection.
|
|
|
Shigella attach and invade which cells located where?
|
M cells (microfold cells) in Peyer's patches.
|
|
|
How do Shigella species cause disease?
|
The invade and replicate in epithelial cells lining the colonic mucosa. TTSS mediates ruffling.
|
|
|
In an infection with Shigella, actin filaments in host cells are activated and then what happens?
|
Bacteria are propelled through the cytoplasm to adjacent cells where cell-to-cell passage occurs.
|
|
|
Shigella sonnei clinical syndrome
|
lower abdominal cramps and tenesmus with abundant pus and blood in the stool. No bacteremia. Symptoms appear 1 to 3 days after bacilli ingested. Infection generally self-limited but may persis for 1 to 2 weeks.
|
|
|
ETEC toxin is like which other toxin?
|
Antigenically similar to V. cholerae toxin.
|
|
|
EHEC toxin is like which other toxin?
|
Shigella toxin Shiga toxin or Shiga like toxin.
|
|
|
Shiga dysenteriae clinical syndrome
|
Produces exotoxin, Shiga toxin with 1 A subunit and 5 B subunits. B subunits bind to host cell glycolipid (Gb3) and facilitate transfer of the A subunit into the cell.
|
|
|
In Shiga dysenteriae clinical syndrome what does the A subunit do?
|
It cleaves the 28S rRNA in the 60S ribosomal subunit-prevents binding of aminoacyl-transfer RNA and disrupts protein synthesis. Primary manifestation of toxin activity is endothelial damage, renal damage results in hemolytic uremic syndrome.
|
|
|
Yersinia pestis is the agent of what?
|
THE PLAGUE!!!!!!!
|
|
|
Y. enerocolitica and Y. pseudotubercolisis cause what?
|
GI disease in humans: infection mimics appendicitis; In USA infections common only in Great Lakes region.
|
|
|
All three species of Yersinia have a plasmid that carries virulence genes for what?
|
Adherence.
|
|
|
(Yersinia) yadA gene
|
Y. adherence gene
|
|
|
yop genes
|
multifunctional Y. outer membrane protein genes
|
|
|
lcr genes (yersinia)
|
low calcium response genes (regulatory)
|
|
|
Concerning the yad, yop and lcr genes:
|
11 yop genes have cytotoxic activity, inhibit migration and engulfment of phagocytes, inhibit platelet aggregation.
|
|
|
In addition to yad, yop and lcr, Y. pestis has two additional plasmids encoding virulence genes called what?
|
FI gene and Pla gene.
|
|
|
FI gene of Y. pestis
|
codes for antiphagocytic protein capsule
|
|
|
Pla gene
|
degrades complement components C3b (preventing opsonization) and C5a (preventing phagocytic migration); also Pla gene degrades fibrin clots permitting Y. pestis to spread rapidly.
|
|
|
What are the two types of Plague caused by Y. pestis?
|
Pneumonic and bubonic.
|
|
|
Pneumonic plague
|
pulmonary infection; inhalation or hematogenous spread; highly infectious from person to person-transmitted by aerosols
|
|
|
Bubonic Plague
|
Painful bubos (inflammatory swelling of lymph nodes) in groin and axilla; no person to person spread
|
|
|
All Y. pestis infection are classified as what?
|
Zoonotic, humans being the accidental hosts; USA, small wild rodents, Southwest
|
|
|
Plague local: 2 types both spread by what?
|
infected fleas
|
|
|
Urban plague
|
rats are the natural reservoirs, this was the black death of medieval Europe
|
|
|
Sylvatic Plague
|
squirrels, field mice, domestic cats, rabbits, prairie dogs are natural reservoirs.
|
|
|
There are very few cases of the plague that occur annually. What are some risk factors or which populations are at risk?
|
hunters, travel history of hunting and camping, small boys camping in endemic areas.
|
|
|
Enteric Disease-Yersinia enterocolitica, Y. pseudotuberculosis general information:
|
uncommon except in colder areas of north america, common cause of enterocolitis in Scandanavian and other European countries. Gastroenteritis characterized by diarrhea, fever and abdominal pain that lasts for up to two weeks.
|
|
|
Enteric Disease caused by Y. enterocolitica involves invasion of what?
|
cells of the terminal ileum.
|
|
|
In enteric disease caused by Yersinia if the mesenteric lymph nodes become enlarged the disease can mimic what?
|
appendicitis; it is called pseudoappendicitis and it is most common in children.
|
|
|
In 1987 there was a report of transfusion related bacteremia and endotoxic shock with Yersinia. Why is this?
|
Yersinia can grow at 4 degrees C and grow to toxic concentrations in nutritionally rich blood products that are contaminated and refrigerated.
|
|
|
Klebsiella-General information
|
Gram - bacilli, oxidase negative, lactose fermenting, prominent polysaccharide capsule causing mucoid appearance and enhanced virulence, producers of beta lactamase.
|
|
|
What is the most commonly isolated member of Klebsiella?
|
Klebsiella pneumonia-cause of community acquired primary lobar pneumonia in alcoholics (aspiration pneumonia) and people with compromised pulmonary function because of their inability to clear aspirated oral secretions from lower respiratory tract.
|
|
|
Pneumonia caused by Klebsiella frequently involves what type of pathology?
|
necrotic destruction of alveolar spaces, cavity formation, and production of blood-tinged sputum,
|
|
|
In addition to pneumonia, what other types of infections to Klebsiella cause?
|
wound, soft tissue and UTIs.
|
|
|
Proteus-general
|
Gram negative bacilli, oxidase negative, acid from glucose, non lactose fermenting.
|
|
|
What is the most common disease caused by proteus?
|
Infection of the urinary tract with P. mirabilis.
|
|
|
All strains of Proteus produce large quantities of what?
|
Urease which splits urea into CO2 and NH3 (raises the pH of urine to pH 10-11). This rise in pH facilitates formation of renal stones and the increased alkalinity of urine is also toxic to the uroepithelium.
|
|
|
Proteus is common where?
|
In foot ulcers because of the moist environment.
|
|
|
Enterobacter, Citrobacter, Morganella and Serratia
|
Infection rare in immunocompetent patients, non-hospitalized patients; commonly cause nosocomial infections in immunocompromised patients with urinary catheters, people who are intubated; antibiotics can be very ineffective since organisms are frequently resistant to multiple antibiotics.
|
|
|
Lab culture of enterobacteriaceae
|
They grow readily on culture media; specimens from normally sterile sites culture on non selective media; organisms from sites normally contamined with other bateria like stool or sputum use selective media like MacConkey agar
|
|
|
Use of selective agars helps separate enterobaceriaceae into what?
|
Lactose fermenters and non-lactose fermenters.
|
|
|
Highly selective or organism-specific media useful for recovery of what?
|
Salmonella and Shigella in stool
|
|
|
Antibiotic therapy is not recommended for many enterobacteriaceae infections. Why?
|
Prolong fecal carriage of this organism.
|
|
|
What are some prevention methods for enterbacteriaceae infections?
|
Sanitation, infection control and immunization with live, attenuated vaccine for Salmonella typhi
|
