Enterobacterales Flashcards
What is the gram staining of enterobacterales?
Gram negative bacilli
Enterobacterales are able to grow in what type of oxygen conditions? What is this type of bacteria labeled?
Aerobic or facultative anaerobes (2 types)
They can grow with or without oxygen
Do enterobacterales form spores?
No
How to enterobacterales make energy?
Glucose fermentation
Enterobacterales are catalase (+/-) and oxidase (+/-)
Catalase pos
Oxidase neg
These enterobacterales are strict human pathogens. What are they?
Salmonella typhi
Yersinia pestis
This an enterobacterale that is part of normal GI flora but can become pathogenic by acquiring pathogenic genes or if there is opportunity for infection
Eschericha coli
There are 7 common virulence factors associated with enterobacteriacease
Endotoxin
Capsule
Antigenic phase variation
Type III secretion systems
Sequestration of growth factors
Resistance to serum killing
Antimicrobial resistance
What is antigenic phase variation?
Bacteria changes its surface protein to evade host immune response
Bacteria can do this randomly or based on env cues
What is the type III secretion system?
Protein structure in some bacteria that allows them to inject virulence factors into host cells that let them manipulate the host cells
What is involved in traditional bacterial identification methods?
Use of phenotypic methods such as cultivation on growth and/or selective media, gram staining, and testing to determine metabolic and biochemical properties
What is involved in automated bacterial identification system?
May or may not use a machine
Biochemical assays (may also be used for susceptibility testing)
MALDI-TOF uses mass spec. to identify a sample with computer
Is gram staining beneficial for direct detection of Enterobacteriaceae in stool samples?
No; Enterobacteriaceae are gram neg as are many bacteria part of normal gut flora
Elevated WBCs may suggest enteric infection but their lack is not enough to rule out toxin-mediated GI disease
What diseases are associated with E. Coli?
Gastroenteritis
UTIs
Neonatal sepsis/meningitis
Bacteremia
HAI
What is ETEC?
Enterotoxigenic E. Coli
What site does ETEC infect and what disease(s) does it cause?
Infects the small bowel
Causes traveler’s diarrhea, infant diarrhea in developing countries
What is EPEC?
Enteropathogenic E. Coli
What site does EPEC infect and what disease(s) does it cause?
Infects the small bowel
Causes infant diarrhea in developing countries
What is EAEC?
Enteroaggregative E. Coli
What site does EAEC infect and what disease(s) does it cause?
Small bowel
Infant diarrhea in developing and probably developed countries; travellers diarrhea
What is STEC?
Shiga toxin-producing e. coli
What site does STEC infect and what disease(s) does it cause?
Large bowel
Bloody diarrhea, hemolytic uremic syndrome
What is EIEC?
Enteroinvasive e. coli
What site does EIEC infect and what disease(s) does it cause?
Large bowel
Bloody diarrhea
What toxin do all members of STEC produce what causes the illness(es) associated with these strains?
Shiga toxin 1 and/or 2
What is the most common serotype of STEC associated with illness?
O157:H7
Non-O157 strains of what bacteria cause severe gastroenteritis/HUS/outbreaks
STEC
What is hemolytic uremic syndrome characterized by?
Acute renal failure
Thrombocytopenia
Microangiopathic hemolytic anemia
What can increase the risk hemolytic uremic syndrome with STEC infections?
Administering antibiotics
For this reason, pts suspected of having STEC is not recommended and should be held off on until dx testing is done and STEC is ruled out
What are the diagnostic tools used for identifying STEC?
Sorbitol MacConkey
EIA to detect Shiga toxin
Molecular assays
What specimens can be used for STEC diagnosis?
Stool
Blood
Urine
Bone Marrow (typhoid fever)
What are some culture-independent methods of identifying STEC?
PCR
Serology
What do uropathogenic strain of e. coli produce that allow them to cause UTIs?
Adhesin production (pili, AAF/I, AAF/III, and Dr) —> bladder lining binding
This enzyme in uropathogen strains of e. coli lyse erythrocytes and other cells
Hemolysin HlyA
75% of e. coli strains that cause neonatal meningitis have this virulence factor; what is this called?
K1 capsular antigen
Septicemia commonly originates from what site(s)?
Bladder (UTI) and GI infection (intra-abd infection)
Which Samonella species accounts for most human infections?
S. enterica
What are the 2 species of salmonella?
S. enterica and S. Bongari
Are salmonella part of normal flora?
NO she’s always bad in the body
What are some clinical infections associated with salmonella spp.?
Gastroenteritis
Septicaemia
Typhoid fever
Chronic carriage
Focal infections: osteomyelitis, meningitis, brain abscess, endocarditis
This media is selective for salmonella spp and some shigella spp.
Salmonella-Shigella agar inhibition of certain bacteria and favours growth salmonella spp. via brilliant green and bile salts
What are the 4 species of shigella?
S. Dysenteriae
S. Flexineri
S. Boydii
S. Sonnei
Which strain of shigella makes Shiga toxin?
S. Dysenteriae
What animal(s) are reservoirs for shigella?
Humans only
How is shigella transmitted?
- Fecal-oral route (dirty hands)
- Water and food (less common)
What are the 3 Yersinia species pathogenic in humans?
Y. Pestis
Y. Enterocolitica
Y. Pseudotoberculosis
What is the pathogen for “the plague”?
Y. Pestis
What animal(s) are carriers for Y. Pestis
Rats
Humans
Fleas
What are the 2 clinical manifestations of Y. Pestis?
Bubonic plague
Pneumonic plague
What Yersinia species cause gastroenteritis?
Y. Enterocolicica
Y. Pseudotuberculosis
What is the incubation period of yersinia spp.?
1-10 days avg 4-6 days
What is the clinical presentation of yersinia?
Diarrhea
Fever
Abd pain
Septicemia
Arthritis
Hepatitis
Osteomyelitis
This pathogen is reported to cause blood transfusion-related bacteremia and endotoxic shock
Y. Enterocolitica
What are the two klebsiella spp. commonly associated with causing community or hospital-acquired primary lobar pneumonia?
K. Pneumoniae
K. Oxytoca
This feature is responsible for the virulence and mucoid colony appearance of Klebsiella spp.
Capsule
Other than lung infections, what other infections are associated with Klebsiella spp?
Wound and soft tissue
UTIs
Sepsis
This Klebsiella spp is responsible for donovanosis. What is donovanosis?
K. Granulomatis
STI characterized by ulcerative lesions on the genital and anal area —> granulomatous tissue
What enterobacterales do no need antibiotic therapy?
STEC
Salmonella gastroenteritis in the immunocompetent host
What is ESBL?
Extended-spectrum β-lactamases = intrinsic resistance
Enterobacterales with this enzyme hydrolyze penicillins and cephalosporins
What are some methods of preventing enteric infection?
Education (food handling and prep)
Infection control measures (handwashing, proper diaper disposal)
Vaccines (when available)
Water treatment
What are the surveillance systems in Canada to monitor cases of food borne illness?
FoodNet Canada
National Enteric Surveillance Program (NESP)
PulseNet Canada
