Microbiological analysis of urine specimens

Question 1

composition of the urinary system

Answer 1

-two kidneys and two ureters
-one urinary bladder and one urethra

Question 2

Which organs do not posses residential microbiota

Answer 2

kidneys, ureters, and bladder
-urine contains some antimicrobial proteins but if left at room temp urine can support bacterial growth

Question 3

What keeps the urine sterile?

Answer 3

the movement of urine from the kidneys to the urinary bladder provides mechanical flushing that keeps urine sterile

Question 4

What bacteria is found externally in females

Answer 4

lactobacillus

Question 5

Where can residential microbiota be found

Answer 5

male/female external genitalia and lower urethra

Question 6

What bacteria is found externally in males

Answer 6

-microbiota similar to those that colonize the epidermis of the skin

Question 7

microbial antagonism

Answer 7

-our residential microbiota in this region can cause this
-it means to occupy space and block access to nutrients making it difficult for pathogens to colonize this region

Question 8

ascending infection (pathway)

Answer 8

normal flora of the urethra/genitalia travel upwards through the urinary bladder to the kidneys
-bacteria will multiply in the urinary bladder and can travel through the ureter to infect the kidneys
-these infections occur more in females than males

Question 9

Descending infection (pathway)

Answer 9

blood carries bacteria from a different infection site to the kidneys
-the bacteria travel with urine through the ureter to the bladder
-these infections are much less frequent than ascending

Question 10

Urine produced from the kidneys will be?

Answer 10

sterile and free of microorganisms

Question 11

when is flora introduced into urine?

Answer 11

-when the urine passes through the lower urethra

Question 12

midstream voided urine sample

Answer 12

the first and last part of urine are not collected to avoid contamination by hands
-from health organisms will contain some microorganisms from their normal microbiota

Question 13

What bacteria causes most urinary infections?

Answer 13

Enterobacteriaceae which is gram negative bacteria from the intestinal microbiota

Question 14

What represents most enteric based UTIs

Answer 14

E.Coli represent about 70%
-Proteus and Klebsiella are also common

Question 15

What represents most non-intestinal bacteria causing UTI infections

Answer 15

Pseudomonas and Staphylococcus

Question 16

Yeast infection ( Candidiasis)

Answer 16

if candida albicans and other candida fungal species reach populations that are too high in this region they are called a UTI

Question 17

What causes E.Coli to have virulence factors

Answer 17

1. flagella permit E.Coli to swim through the ascending pathway
2. fimbriae allow E.Coli to attach to the cells that line the urinary bladder
   3.biofilms like substances help E.Coli evade our immune response

Question 18

How are most urine sample collected?

Answer 18

clean midstream void

Question 19

How can urine be collected directly from the bladder?

Answer 19

aseptic catherization, cystoscopy, and suprapubic aspiration

Question 20

Where is urine stored and collected?

Answer 20

-collected in a sterile container and stored in a refrigerator

Question 21

What media do we use to culture urine samples?

Answer 21

on MacConkey plate or sheep blood agar to determine the colony forming units (CFUs)

Question 22

What do we use to transfer urine to the media plates?

Answer 22

calibrated loop
-allow you to streak an exact volume of urine typically 0.1 ml (100ul) or 0.01 ml (10 ul- yellow loop) or even smaller volumes .001 ml (1ul- blue loop)

Question 23

How to determine CFUs?

Answer 23

counting the number of colonies that formed on the agar culturing the sample

Question 24

How is the numbers of colonies per ml (CFU/ml) calculated?

Answer 24

multiplying the number of colonies counted by a conversion factor dependent on the initial volume used

Question 25

If 0.01 ml (10 ul) was plated what do you multiply it by?

Answer 25

number of colonies * 100

Question 26

If 0.001 ml (1 ul) was plated what do you multiply it by?

Answer 26

number of colonies * 1000

Question 27

clean midstream void <10,000

Answer 27

negative for UTI

Question 28

clean midstream void 10,000-100,000

Answer 28

suspicious or equivocal

Question 29

clean midstream void > 100,000

Answer 29

positive for UTI

Question 30

What are the instances where it is automatically positive for UTI?

Answer 30

-Aseptic catherization, cystoscopy, and suprapubic aspiration

Question 31

Too numerous to count (TNTC)

Answer 31

if a bacterial lawn is grown on the media plate and unable to count individual colonies

Question 32

What does MacConkey agar select for?

Answer 32

gram negative bacteria such as Enterobacteriaceae like E.Coli or Proteus or other UTI causative agents like Klebsiella and Pseudomonas
-Pseudomonas and E.Coli are both gram negative but can be differentiated based on if they ferment lactose

Question 33

E.Coli test results on MacConkey agar

Answer 33

ferments lactose –> acidic/wine pink

Question 34

Pseudomonas results on MacConkey agar

Answer 34

does not ferment lactose

Question 35

What do the bile salts and crystal violet do

Answer 35

-inhibit most gram positive organisms