Enterobacteriaceae Flashcards
- What are the lactose fermenters Enterobacteriaceae? What colony they will give?
- E. Coli
- Klebsiella pneumonia
- Enterobacter
- Citrobacter
- Serratia
Are they gram positive or negative bacteria?
Gram negative
Are they spore forming bacteria?
Non spore forming
Aerobic, anaerobic or facultative anaerobes?
Aerobic or facultative anaerobes
Catalase and oxidase test results?
Catalase positive, oxidase negative
Motile or nonmotile?
Some of them are motile, others are non motile
What are the non-lactose fermenters Enterobacteriaceae?
- Pertussis
- Providencia
- Salmonella
- Shigella
- Morganella
What do we call them?
Enteric bacteria
What are their antigenic structures?
Capsule, flagella, pili, O antigen and LPS
What are the antigens of the capsule and the flagella?
K antigen for the capsule, H antigen for the flagella
Which Ag induces the production of IgM?
O antigen
What are their virulence factors?
Enterotoxin, capsule, antigenic phase variation, exotoxin production, expression of adhesion factors, intracellular survival and multiplication, sequestration of growth factors, resistance to serum killing and antimicrobial resistance.
What is the antigenic phase variation?
Change of antigenicity depending on phase meaning environmental factors
What is the importance of expression of adhesion factors?
Important for colonization, so for the establishment of the disease
What is the importance of the intracellular survival and multiplication?
In order to spread
What do we mean by sequestration of growth factors?
Growth factors that bacteria cannot produce but need for their growth
What is the resistance to serum killing?
Resistance to killing by common antibodies in the serum with bactericidal properties
What is the biggest problem with Enterobacteriaceae?
Their anti-microbial resistance that spreads very quickly
What are bacteriocins?
Substances produced by bacteria to compete with pathogenic ones
Which one will produce colocins?
E. Coli
Which one will produce marcescens and what’s its color?
Serratia marcescens
Red
Which one will produce pyocins and what’s its color?
Pseudomonas
Can be black, red, blue or green
When do they cause opportunistic diseases?
When they acquire virulence factors and depending on the immune system status of the individual
Which Enterobacteriaceae are pathogenic and are not part of our normal flora?
Salmonella and Shigella
Which structure controls the production of bacteriocins?
plasmids
Which one will infect the central nervous system?
E coli
Which bacteria will infect the lower respiratory tract?
Mostly E coli and enterobacter (which are normally not part of the NF of the respiratory tract)
Klebsiella (part of the normal flora of the upper respiratory tract)
Which one will infect the bloodstream?
Any type can cause bacteremia and thus a septic shock
Which one infect gastrointestinal tract?
Salmonella, shigella, yersinia psedotuberculosis and E. coli
Which one will infect the urinary tract?
E. coli, klebsiella, Proteus, Providencia
How can we differentiate between Proteus and Providencia which have similar aspects?
Providencia is uriase negative
What’s Gastroenteritis?
A syndrome characterized by gastrointestinal symptoms including nausea, vomiting, diarrhea and abdominal discomfort
What’s diarrhea?
Abnormal fecal discharge characterized by frequent and/or fluid stool, usually resulting from disease of the small intestine and involving increase in fluid and electrolyte loss
What’s the definition desentery?
Inflammation disorder of the G.I. tract often associated with blood and pus in feces accompanied by symptoms of pain, fever, abdominal cramps, usually resulting from diseases of the large intestine
Define the enterocolitis.
Inflammation involving the mucosa of the small and large intestine
How Enterobacteriaceae are transmitted?
Fecal oral route: we can be infected boy feces from humans or animals containing pathogenic microbes or the toxins, through food, fluid or fingers.
In which medium they are cultured?
McConky medium: it inhibits the growth of gram-positive bacteria
What are the three classes of E. coli?
- Commensals
- ExPEC
- IPEC
Are the commensals part of our normal flora? Pathogenic?
Yes they are
Not pathogenic
When do they cause a disease?
Suppression of the remaining NF by antibiotics or when the peritoneum is ruptured
What are the ExPEC?
Extra intestinal pathogenic E. coli
Are they pathogenic and do they have the ability to invade other places?
They are pathogenic since they have virulence traits and cause diseases outside the intestinal tract, meaning they have the ability to invade other places, but in their normal place they do not cause diseases
What are clinical presentations of ExPEC?
UTI
Pneumonia
Neonatal meningitis
Septic shock
How do they cause urinary tract infections?
They adhere by strain specific pili to urethra causing urethritis. May ascend to the bladder causing cystitis, and in kidneys cause pyelonephritis.
How do they cause septic shock?
By endotoxin release
Why urinary tract infections are more frequent in females?
Because the urinary tract and the rectum are very close
What are the symptoms of urinary tract infections?
Frequent urination, dysuria, abdominal cramps, large amounts of bacteria and leukocyte in midstream urine.
It can be complicated by hematuria and proteinuria
What are the IPEC?
Intestinal pathogenic E. coli
Are they members of the normal flora?
No, they are pathogenic, from outside, and can cause diseases in small and large intestines
What are the clinical presentations of an infection with IPEC?
Watery diarrhea or dysentery, depending on the strain
What are the types of IPEC?
EPEC ETEC EHEC EIEC EAEC
What are the EPEC?
Enteropathogenic E. coli
What is the target age group of EPEC?
Babies and young children in developing countries where there is poor hygiene or daycare centers
How they are transmitted?
Strictly human-human transmission
What is the incubation period?
1 to 2 days
Do they have virulence factors
No they don’t
How do they cause pathology? What is their effect?
They adhere to small intestinal mucosa but do not invade, inducing structural changes in the mucosal cells.
Their effect is effacement (flattening of the microvilli)
Do they induce an inflammatory reaction?
No
What is the outcome of the disease?
Watery diarrhea containing mucus that lasts 1-2 days without fever or abdominal cramps
What is the treatment in this case?
Supportive therapy(electrolytes balance) and antibiotic treatment that can shorten the duration of diarrhea
What’s the most important bacterial cause of diarrhea in children in developing countries and the most common cause of travelers diarrhea?
ETEC: enterotoxingenic E. coli
How is is transmitted?
From animals and humans
Water contaminated by humans or animals sewage may be important in the spread
What is the size of the inner column?
Large
What’s the incubation period?
3 to 4 days
Where the bacteria adhere? Does it invade?
The bacteria adhere to the small intestine but do not invade?
What is the cause of the disease?
The production of toxins
Which 2 toxins are released?
LT and ST
To which toxin in the LT is similar?
Cholera toxin
How the LT cause disease?
It is an AB5 toxin that activates adenylate cyclase, increasing the level of cAMP, so that crypt cells secrete more Cl-, villus cells absorb less Na+, causing osmotic loss of water to lumen. Water and electrolytes increasing, causing a distention responsible for the abdominal cramps.
Can this toxin be destroyed by heating?
Yes
To which toxin the ST is similar?
To Y. enterocolitica toxin
How does it cause disease?
It activates guanylate cyclase, increasing the level of cGMP, so that cotransport of an NaCl into cells decreases, and water remains in the lumen.
Manifestations are pure watery diarrhea and abdominal discomfort.
What is the EHEC?
Enterohemorrhagic E. coli
How it is transmitted?
Food, unpasteurized milk and uncooked meat
What’s the difference between the ETEC and the EHEC concerning the inoculum size?
In the case of EHEC, a small inoculum size cause disease
What’s the incubation period?
5 to 7 days
Where does it adhere?
It adhere to colonic epithelium but do not invade
Which toxin does it produce? How does it cause disease?
Cytotoxic shiga-like toxins (SLT 1 and 2) also called verotoxin since it destroys vero cells which removes the adenine residues from 28S rRNA of the 60S ribosome, thus blocking protein synthesis
What’s the outcome? What are the manifestations?
The outcome is necrotic
Manifestations: it can start with a watery diarrhea, and progressed to a bloody diarrhea here we talk of a dysentery. There is mucus production, abdominal cramps but no fever.
What happens when toxins enter the bloodstream?
Bacteria spread to kidneys causing damage, that will end up with hemolytic uremic syndrome HUS
What is the hemolytic uremic syndrome?
There is an acute renal failure, hemolytic anemia, thrombocytopenia and fever
What is the important cause of diarrhea in areas of poor hygiene?
EIEC
How is it transmitted?
Infections are usually foodborne
What’s the inoculum size?
Large (10^8-10^10)
What’s the incubation period?
It stays about 10 days
Where does it adhere?
It adhere to colonic epithelium and invade mucosal layer
Which toxin does it produce?
SLT 1 and 2
What is the outcome?
Necrosis in different areas of the colon
What are manifestations?
Watery to bloody diarrhea with mucus production, abdominal cramps, with many systemic signs like fever
We have tenesmus which is a continual or recurrent inclination to defecate meaning that the diarrhea is not smooth but it’s not the constipation either.
Dysentery with leukocytes in stool
Why EAEC are called as such ?
Enteroaggregative E. Coli.
Because they aggregate in culture
What is the target age group? In which countries it causes disease?
It causes diarrhea in children in developing countries
How much inoculum it needs?
It needs a very high inoculum
What is the incubation period?
It’s very long, from 14 to 30 days
What are the manifestations of the infection?
Play diarrhea, no colitis, no dysentery
What’s the most common cause of UTI and gram-negative sepsis?
E. coli
What are the most common causes of neonatal meningitis?
Streptococcus B, E. coli, listeria
What are the most common causes of neonatal pneumonia?
Streptococcus B and E. coli
What is the results of the gram staining?
Gram negative rods
How appear lactose fermenters on MacConkey?
They appear red
Which antigens are detected in serology?
O and H antigens
What’s the biggest problem in Enterobacteriaceae?
Their resistance to antibiotics
To which antibiotics they are sensitive?
Third generation cephalosporin, quinolones for UTI
Why prophylaxis given before traveling doesn’t help?
This can increase the time needed for convalescence so the person will be excreting the bacteria in the environment for a longer period which constitutes a problem for the community.
How Klebsiella pneumoniae are transmitted?
They are transmitted directly from person to person.
Who’s the reservoir?
Humans are the only reservoir
What are the clinical presentation?
Pneumonia, UTI
What’s the condition for causing the disease?
The individuals should be immunosuppressed
In which part of the body bacteria that causes pneumonia are normally present?
In the normal flora of the upper respiratory tract
What is the EIEC?
Enteroinvasion E. coli
In which individuals the rate of having a pneumonia is higher?
Alcoholic individuals
How starts the disease? How does it progress?
The disease starts with simple pneumonia that progresses into a consolidation pneumonia and then into a necrotizing hemorrhagic pneumonia.
In which part of the body bacteria that cause UTI are normally present?
They are part of the intestinal tract normal flora
Do they cause frequently UTI?
They very rarely cause UTI.
What is the shape of colonies on microscope?
Big mucoid colonies
What is the drug of choice?
Carbapenem
Which type of infections Enterobacter can cause?
Nosocomial infections (they are present in many areas of the hospital environment)
In which part of our body they are normally present?
Part of the normal flora in or out of the intestines
Which infections do they close locally?
UTI mainly, infections due to indwelling medical devices
Which infections they cause systemically?
Pneumonia after bacteremia, the patient should be immunosuppressed
How do they cause UTI?
They could be introduced by a urinary catheter.
What is the antibiotic treatment?
Imipenem + some 4th generation cephalosporins + quinolones
To which bacteria Serratia marcescens is similar?
Enterobacter since it can cause nosocomial infections too.
What are the clinical presentation of this bacteria?
Endocarditis
What condition should be present?
the patient should be heavily immuno suppressed
How Serratia can be acquired?
After a surgery
What’s the antibiotic treatment?
Imipenem + 4th generation cephalosporins + quinolones
Give two types of Proteus.
Proteus mirabilis, Proteus vulgaris
What are the local infections caused by Proteus?
UTI the most common, struvite stones
Which infection is caused systemically?
Focal abscess
What is their most important virulence factor?
Their motility
In which part of the body they are normally found?
They are part of the normal flora of the G.I. tract.
Where are they found in the environment? How do they enter humans?
They are found in sewage and soil.
They enter humans through the urinary tract
How struvite calculi are formed?
Urease splits urea to form ammonium hydroxide, which raises the pH of urine. The increase in pH precipitates ammonium magnesium phosphate, leading to struvite calculi formation.
What do contain the stones formed?
They contain Proteus.
Why the smell of urine changes?
Because of the ammonia
What happens after bacteria spread in the blood?
They can cause focal abscesses after a bacteremia.
What’s the result of the urease test?
They are urease positive
Why the urine is alkaline?
Because of the ammonia
What’s the antibiotic treatment?
Imipenem + 4th generation cephalosporins + quinolones
What’s the clinical presentation in the case of Providencia infection?
UTI
- Which condition should be present to be infected with Providencia?
The patient has to be hospitalized and catheterized for at least 30 days.
Do they cause disease in immunocompetent individuals?
No
Do they cause systemic diseases?
There is no bacteremia, no sepsis, no pneumonia or any other systemic disease.
Can we give antibiotics as a treatment?
No they are resistant to antimicrobial therapies
What will be the clinical presentation of Citrobacter?
UTI, brain abscess after bacteremia, sepsis
Could it be transmitted easily between infectious individuals?
Yes
Are they aerobic, anaerobic or facultative anaerobic?
Facultative anaerobes
