Enterobacteriaceae I and II Flashcards
- List the four unvarying biochemical characteristics of the family Enterobacteriaceae
Facultative Gram-Neg rods
Ferment glucose
Reduce nitrate to nitrite
Oxidase negative
- Describe diseases associated with E. coli,
Gram negative sepsis Urinary tract infections – (80% of community acquired UTIs) Wound infections Pneumonia in IC hospitalized patients Meningitis in neonates Gastroenteritis
- Describe diseases associated with Shigella,
• Bacillary Dysentery
- Abdominal cramps, tenesmus, pus and blood in stool
- Tissue invasion limited to epith. cells and submucosa
- Fecal leukocytes present
- Incubation 1-3 days lasting 48 hrs.
- Humans serve as natural host
- Most communicable of bacterial diarrheas
- Transmitted by fecal oral route
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- Describe diseases associated with Edwardsiella
- Primarily causes gastroenteritis, rare cases of septicemia
- Gastrointestinal Disease includes:
- Acute, self-limiting gastroenteritis with watery diarrhea
- Typhoid-like illness with bloody diarrhea and possible fever, nausea, vomiting, colonic ulcerations and terminal ileum nodularity
• Has been mistaken for salmonellosis and inflammatory bowel disease (Crohn’s disease)
- Describe diseases associated with Citrobacte
Nosocomial infections of urinary and respiratory tracts of debilitated, hospitalized patients, endocarditis and hospital acquired bacteremias
C. freundii - rare cause of diarrhea
C. koseri - rare cause of meningitis and brain abscess in neonates
- Describe diseases associated with Klebsiella,
K.pneumoniae and K. oxytoca - Primary lobar pneumonia characterized by destructive changes, necrosis, and hemorrhage (“currant jelly” sputum), bronchopneumonia, bronchitis, accounts for 9% of UTI’s and 14% of bacteremias in hospitalized patients (much more common than the other 2)
K. ozaenae - atrophic rhinitis (ozena), destruction of mucosa and fetid mucopurulent discharge
K. rhinoscleromatis - rhinoscleroma, chronic granulomatous disease involving mucosa of upper respiratory tract
- Describe diseases associated with Enterobacter
Frequent colonizers of hospital patients, cause opportunistic infections involving urinary tract, respiratory tract, cutaneous wounds, occasional cause of septicemia and meningitis
Antibiotic therapy can be ineffective, because the organisms are frequently resistant to multiple antibiotics
- Describe diseases associated with Serratia
Nosocomial infections, pneumoniae, septicemia, UTI, surgical wound and cutaneous infections. Also reported as a cause of endocarditis and osteomyelitis in IV drug addicts
only organism with red colonies
- Describe diseases associated with Proteus
Second only to E. coli in frequency of isolation in the clinical laboratory
P. mirabilis is most frequently isolated species, cause of UTI and wound infections. Strongly urease positive produces highly alkaline urea which can lead to renal calculi composed of struvite (magnesium ammonium phosphate
P. vulgaris most commonly recovered from infected sites in IC patients
colonies grow in a swarming pattern and are Strongly Urease Positive
- Describe diseases associated with Yersinia
Orgs. adheres to and penetrates the ileum, causing terminal ileitis, lymphadenitis, and acute enterocolitis. Mimics appendicitis. Most common in children
Enterocolitis accounts for 2/3 of infection. Diarrhea, fever, abdominal pain lasting as long a 1-2 weeks. Chronic form can persist mos to > yr
Also associated w/transfusion related sepsis, arthritis, intraabdominal abscess, hepatitis, osteomyelitis
Blood contamination occurs do to asymptomatic Y. enterocolitica bacteremia at time of blood donation
Y. enterocolitica can proliferate in blood stored at 4o C after 2-3 weeks
- Name the five genera of Enterobacteriaceae that can cause gastrointestinal disease
Citrobacter
Escherichia
Salmonella
Shigella
- Name the five groups of E. coli that can cause gastroenteritis
Enterotoxigenic E. coli (ETEC)
Enteropathogenic E. coli (EPEC)
Enteroinvasive E. coli (EIEC)
Entero-Hemorrhagic E. coli (EHEC)
-aka Shiga Toxin producing E. coli (STEC)
Enteroaggregative E. coli (EAggEC)
- List the triad of symptoms that defines hemolytic uremic syndrome (HUS)
- acute renal failure
- thrombocytopenia ( lack of platelets)
- hemolytic anemia
Preceded by bloody diarrhea
- Describe the reservoir, and mode of transmission of disease caused by Shiga-toxin producing E. coli
transmission:
STEC is shed in feces of cattle, sheep, deer, and other ruminants.
Human infection is acquired via contaminated food or water, or via direct contact with an infected patient
Foodborne outbreaks most commonly associated with undercooked ground beef
Reservoir in healthy dairy cattle
- Describe the clinical presentation of disease caused by Shiga-toxin producing E. coli
- Causes both bloody and nonbloody diarrhea
- Infections associated with: Hemolytic Uremic Syndrome (HUS) Hemorrhagic Colitis**
- Young children and elderly at increased risk for severe complications
- Abdominal cramps, watery diarrhea, bloody discharge
- No significant fever
- Absence of WBC in stool
- Describe the method of laboratory diagnosis of disease caused by Shiga-toxin producing E. coli
Timing: Collect in early stages of any enteric illness (first 4 days of onset) when organism load is higher and before antibiotic treatment is initiated.
Type: whole stool is preferred; multiple specimens may enhance recovery.
Transport: as soon as possible; refrigerate at 4 C if more than 1-2 hours; transport media can be used.
Antigens: Shiga toxin or the O157 antigen (lipopolysaccharide-LPS)
Direct fecal specimen detection
Enriched broth culture detection (more sensitive)
- Describe the treatment of disease caused by Shiga-toxin producing E. coli
Oral rehydration (Gatorade, Pedialyte), supportive care, and careful monitoring of kidney function.
HUS and renal failure: can be managed by dialysis.
Antibiotics NOT given in STEC
Antimotility agents - NO! NO!
Chemoprophylaxis with SXT or ciprofloxacin for
travelers’ diarrhea NOT recommended
Most strains are very susceptible, however, treatment with antimicrobials has NOT been shown to shorten the duration or severity of disease and treatment possibly increases the risk of developing HUS
- Compare the transmission and clinical manifestations of E. coli, Shigella, Salmonella and Y. enterocolitica
E. coli - feces of cattle, sheep, deer. Contaminated food, person-to-person and rarely contaminated water
Shigella -person to person via fecal oral route. Contaminated water, food, flies, fingers, fomites, feces (5 f’s)
Salmonella - poultry, reptiles
Y. enterocolitica - pigs, lakes, streams
- List the five clinical manifestations of Salmonella infection
- Asymptomatic (carrier)
- Febrile Gastroenteritis
- Septicemia
- focal infections
- enteric fever
general characteristics of enterobacteriaceae
Diverse group of Gram negative rods
Indigenous flora of GI tract (humans and animals)
Colonize respiratory tract of hospitalized patients
Grow rapidly aerobically/anaerobically
Simple growth requirements
LPS (endotoxin) – 3 components
- O-antigen: located on outer most domain. Polysaccharide (repeating monosaccharide trimers in diverse combination and sequences); giving rise to 100-200 distinct serotypes
- Core oligosaccharide that attaches directly to Lipid A
- Lipid A: inner most region of LPS. Responsible for toxicity. When bacterial cells are lysed by the immune system, fragments of membrane containing lipid A are released into the circulation, causing fever, diarrhea, and possible fatal endotoxic shock (also called septic shock).
H-antigen
more than 50 serotypes; located in peritrichous (all around the bacterium) flagella.
found on enterobacteriaceae
K-antigen
more than 80 serotypes; located in capsule (important in causing extraintestinal colonization, UTI, and invasive disease.
virulence factors of Enterobacteriaceae
• Endotoxins
Lipopolysaccharides: major factor in pathogenesis - fever, sepsis, shock & multiorgan failure
• Capsule: protects from phagocytosis
• Antigenic Phase Variation
Altered expression of K,H Agns protects from antibody mediated
cell death
• Type III secretion systems
facilitates secretion of bacterial virulence factors into host cells
• Sequestration of growth factors – eg. Iron scavengers
• Resistance to serum killing
• Antimicrobial resistance
all non-lactose fermenting enterobacteriaceae cause
diarrhea
signs and symptoms of gastroenteritis caused by Enterotoxigenic E. coli (ETEC)
Secretory diarrhea (Traveler’s Diarrhea) similar to V. cholerae. Profuse watery diarrhea* is predominant symptom.
Often accompanied by mild abdominal cramps. Dehydration and vomiting occur in some cases.
signs and symptoms of gastroenteritis caused by Enteropathogenic E. coli (EPEC)
Usually occurs in infants. Characterized by low-grade fever, malaise, vomiting, and diarrhea, with a prominent amount of mucus, but with no gross blood.
signs and symptoms of gastroenteritis caused by Enteroinvasive E. coli (EIEC)
Inflammatory diarrhea (Dysentery) similar to Shigella. Hallmarks are fever and colitis.
Symptoms are urgency and tenesmus; blood, mucus, and many leukocytes in stool.
signs and symptoms of gastroenteritis caused by -Hemorrhagic E. coli (EHEC)
-aka Shiga Toxin producing E. coli (STEC)
Bloody diarrhea without WBCs*.
Often no fever. Abdominal pain is common. May progress to hemolytic uremic syndrome (HUS).
signs and symptoms of gastroenteritis caused by Enteroaggregative E. coli (EAggEC)
Symptoms include watery diarrhea with blood and mucus*
vomiting, dehydration and less commonly, abdominal pain.
A college student returning from a Spring vacation in Puerto Vallarta, Mexico developed a profuse watery diarrhea accompanied by mild abdominal cramps. His diarrhea is so profuse that he is experiencing symptoms of dehydration. While on vacation he was careful not to purchase food from street vendors but did frequent the local bars and had drinks served with ice. Stool exam revealed no blood or WBC’s. What type of diarrheagenic E. coli is most likely to cause the symptoms experienced by this student?
Enterotoxigenic E. coli (ETEC)
what is the most common serotype of Shiga Toxin producing E. coli (STEC)?
E. coli O157
E. coli O157 HUS Can Occur in Two Settings
- Diarrheal related - classical HUS, vast majority of cases
- Non-diarrheal HUS - much less common, can occur in association with
- pneumococcal infection
- chemotherapy
- transplant immunosuppression
A healthy 3-year-old child develops diarrhea that lasts about a week, and that is bloody for a few days. His diarrhea resolves, but he remains lethargic, and passes only a little urine. A blood smear shows fragmented red blood cells and no platelets. What etiologic agent of infection would most likely produce the signs and symptoms displayed in this case?
E. coli 0157
Characteristics of Shigella
Biochemically and antigenically similar to E. coli
Unlike E. coli, Shigella is
Non-lactose fermenter
Non gas producer
Nonmotile
some strains produce Shiga toxin
transmission of shigella
Person to person via fecal oral route
Contaminated water, food, flies, fingers, fomites, feces (5 f’s)
Highest risk:
Young children in day care center, nurseries, custodial institutions,
Siblings and parents of these children
Male homosexuals
Edwardsielleae habitat
Cold blooded vertebrates,fresh water, catfish, snakes
transmission of salmonella
improper food handling
secondary transmission- person to person
About half of salmonella epidemics are result of contaminated poultry and poultry products.
Also associated with reptiles (lizards, snakes, turtles)
characteristics of salmonella
Non-lactose fermenter
Produces hydrogen sulfide (black)
Enteric Fever
prolonged, serious illness. Typhoid Fever is best known example. Caused by S. typhi and S. paratyphi A and B, rare with other serotypes. Incubation 1-2 weeks. Length of illness is 4 weeks characterized by increasing fever for 2 weeks (bacteremic stage) followed by gastrointestinal symptoms for 1-2 weeks. Only known reservoir of S. typhi is man
Presents with fever, headache, rose spots, constipation
Rose spots; pink macules or prupuric lesions
Fever; temperature-pulse dissociation (Refers to relative bradycardia with a pulse rate less than expected at a given body temperature.
Neuropsychiatric manifestions
septiciemia caused by salmonella
without major gastrointestinal involvement - characteristically found in patients with underlying leukemia, lymphoma, AIDS, SLE, sickle cell crisis, and alcoholic hepatitis. Found frequently in infections due to S. choleraesuis, S. dublin, and S. oranienburg. Relapses are common
focal infections caused by salmonella
Osteomyelitis, meningitis, brain abscess, endocarditis
febrile gastroenteritis caused by salmonella
most common presentation in man. Found in 2/3 of patients with culture confirmed Salmonella infections. Incubation 12-48 h. Symptoms include malaise, nausea, sometimes with vomiting, followed by abdominal pain and diarrhea. Self-limited. Duration 3-5 days.
complications of Salmonella Enteric Fever
Complications GI bleeding Perforation of ileal ulcers Circulatory collapse Relapse following treatment Long term carriage
treatment of of Salmonella Bacteremia
Third generation cephalosporin
A 50 year old female returned to Chicago from a 3 week trip to Jakarta (Indonesia) and about 5 days later started having flu like symptoms and a low grade fever. On the day prior to admission she had spiking fevers followed by profuse sweating. Stool cultures, ova and parasite exams and urine cultures were all negative. The blood culture collected after a spiking fever episode grew a glucose-fermenting, gram-negative rod that was oxidase negative. Additional testing showed the organism was lactose-negative and H2S positive. What is the likely etiologic agent of this patient’s symptoms?
Salmonella typhi
stool culture is negative bc it has 2 phases therefore blood and stool should be sent to the lab
Yersinia enterocolitica Epidemiology
- Widely distributed in lakes and reservoirs
- Epizootic outbreaks of diarrhea, lymph-adenopathy, pneumonia, and spontaneous abortions occur in various animals
- Over 50 serogroups, O:3 predom. serotype infecting humans
- Pigs are a major reservoir for infection in humans
- Diarrheal illness assoc. with household preparation of chitterlings
- Portal of entry is oral digestive route
A 1-year-old African-American patient was brought into the emergency room of an intercity hospital suffering from diarrhea and subsequent dehydration. The family reports that the illness began a couple of days after Christmas. In questioning the parents about food-born source of the infection the parents reported serving chitterlings to the adults but not the children. A stool specimen sent to the laboratory grew a lactose-negative gram-negative bacillus that gave biochemical reactions typical of E. coli except that the organism was urease positive. What is the most likely identity of the bacterium?
Yersinia enterocolitica
