L3 E. coli and Klebsiella spp.

Question 1

where does enterobactericeae usually reside?

Answer 1

intestinal tract, environment

Question 2

what are the two main types of enterobacteriaceae

Answer 2

• opportunistic pathogens
• primary pathogens

Question 2

what are some clinically important genera of enterobacteriaceae

Answer 2

-salmonella
- shigella
- edwardsiella
- escherichia coli
- klebsiella
- enterobacter
- serratia
- proteus- providencia- morganella group
- citrobacter
- yersinia

Question 3

what is some general characteristics of enterobacteriaceae

Answer 3

• gram neg bacilli
• ferment glucose
• reduce nitrates to nitrites
• oxidase negative
• all are motile except klebsiella, shigella, yersinia
• grows on MAC and EMB
• grows readily at 35 cel excpet yersinia

Question 4

how do they classify enterobactericeae

Answer 4

tribes

Question 5

what are the antigenic factors of enterobacteriaceae

Answer 5

• ability to colonize, adhere, produce various toxins and invade tissues
• some posseses plasmids that may mediate resistance to antibiotics
• important antigens are used to identify organism- O, H, K

Question 6

give a simple explanation for how cell wall components are an antigenic factor

Answer 6

• cell wall made up of heat stable LPS, cytoplasmic membrane and thin layer of peptidoglycan
• LPS contain lipids, the core or R and O antigen along the outer wall membrane of cell wall
• if LPS is still attached to the bacteria= no pathological effects
• when organism lyse due to antibiotics or immune attacks= lipid A portion can mediate numerous toxic effects

Question 7

what are the 3 major antigens and explain them simply respectively

Answer 7

• O antigens= somatic, cell wall, heat stable-AG
• H antigen = flagellar, heat labile Ag
• K antigen = capsular, heat labile Ag

Question 8

what are the usual clinical symptoms caused by E.coli

Answer 8

UTIs, diarrheal infections and CNS infections

Question 9

what is the morphology of E.coli on gram stain, BA, NA, MAC

Answer 9

• gram neg bacilli
• beta hemolytic on BA
• NA = larger, circular, low convex, grayish white, moist, opaque and smooth colonies
• MAC = lactose fermenter, pink colonies

Question 10

what is the pathogenesis of E.coli

Answer 10

• E.coli is an invasive bacterium
• it colonizes the human intestine and in specific condition, it directly invades the intestinal mucosa or produces toxins to cause intestinal infections
• the bacteria can enter the blood stream and cause septicemia, meningitidis and other systemic manifestation
• the bacteria under certain conditions, directly invades urinary tracts causing UTIs or cause intraabdominal infections

Question 11

what are the 5 major types of E.coli strains

Answer 11

1. enteropathogenic (EPEC)
2. enterotoxigenic (ETEC)
3. enteroinvasive (EIEC)
4. enterohaemorrhagic (EHEC)
5. enteroadherent

Question 12

what are the 2 types of enteroadherent

Answer 12

• enteroaggregative escherichia coli (EAEC)
• diffusely adherent escherichia coli (DAEC)

Question 13

what are the 4 main types of clinical infections for E.coli

Answer 13

• UTI
• gastroenteritis (diarrhea and dysentery)
• pyogenic infection
• septicaemia