Enterobacteriaceae Flashcards
What is Enterobacteriaceae?
a phylogenetic grouping including foodborne members Shigella, E. coli, Salmonella, and Yersinia, and opportunistic pathogens Klebsiella, Enterobacter, Serratia, Proteus, Providencia, and Morganella
What are the defining features of the group?
Gram (-) Non-sporulating straight rods facultative anaerobes catalase (+) oxidase (-) glucose fermenters
What are the foodborne members of the group?
Shigella, E. Coli, Salmonella, and Yersinina
What are the opportunistic pathogens in the group?
Klebsiella, Serratia, Enterobacter, Proteus, Providencia, and Morganella
What is another key feature that defines their pathogenicity? Why?
Promisicuous to new DNA (like plasmids)–>new virulence factors and antibiotic resistances
What is a major problem for the whole group?
extreme antiobiotic resistance
How does antimicrobial sensitivity testing work?
smear agar on plate with liquid culture from patient isolate
place disks of various antibiotics on the plate before overnight incubation
successful plating produces lawn of bacteria interrupted by zones of clearing around antibiotics, which are compared to table of standards
What are the important virulence factors in the gut?
pili and type 3 secretions systems
Why do gut bacteria need pili?
for attachment, gut and UT constantly push contents out unless they are anchored
Why do gut bacteria need T3SS?
adhesion, enterotoxins, and subversion of the gut macrophages
What is the major mechanism for enterobacteriacaeae infection?
sampled by M cells in Peyer’s patches–>alter the local macrophages for bacterial survival–>spread to exterior surface of the gut–>goes backward and sideways to affect neighboring cells, local infection
Which bacteria infect primarily by backtracking in neighboring cells?
Shigella, E. Coli,
What bacteria can use macrophages as trojan horses? What does each cause?
locally: Y. enterocolicita–>false appendicitis
systemtically: Salmonella typhi–>typhoid fever
What is meant by using macrophages as trojan horses?
Some bacteria can hijack macrophages to travel to and invade either local or systemic lymph nodes
How are the foodborne Enterobacteriaceae transmitted? What can be done to prevent infections?
fecal-oral; water treatment, handwashing, food pasteurization, and cooking
What is HUS? What infections cause it and who primarily suffers from it?
Hemolytic-Uremic sundrome, caused by shigella or EHEC infections (resulting from release of shiga toxin in blood)
primarily pediatric with a 5-10% mortality rate
What is one of the diagnostic tools for HUS?
Schistocytes present in blood smear
What patients develop reactive arthritis?
THose positive for HLA (human leukocyte antigen)-B27
What is reactive arthritis and who is typically at risk for developing it?
It is a triad of symptoms–>conjuctivitis, arthritis, and urethritis; usually poor, indigent homeles, old, drunk men get this disease
What pathogens result in reactive arthritis?
Shigella, Salmonella, Yersinia, Campylobacter, or chlamydia
What is meant by “ICU bugs”?
These are major opportunistic nocosomial pathogens
What are the major ICU bugs?
Klebsiella, morganella, providencia, porteus, and serratia
Why are ICU bugs important?
They seldom cause symptoms in people that are healthy, but are difficult to treat once introduced by catether, or wound infection or general debilitation
What is the best defense against ICU bugs?
frequent changing of IV lines, catheters, ICU and patient scrubdowns, and minimization of hospital stays
