inoculating loop

Maryam Monajemzadeh, pathologist

Children Medical Center Hospital

Tehran University Of Medical Sciences

Aim?

Significance of Colony Counts: AHistorical Background

In retrospect,

• all specimens were collected by catheterization

• most asymptomatic women had counts below 10 3 CFU/mL

In the 1960s and 1970s

• women with symptomatic, acute lower UTls (urethra, bladder, or both), 29%to 45% had colony counts lower than 105 CFU/mL by suprapubic aspiration.

1980 102 CFU/mL.

• growth of ≥ 105CFU of bacteria per milliliter of urine highly indicative of infection

• in young, sexually active women with the acute urethral syndrome (dysuria, frequency, and urgency), as few as 102CFU/mL is considered significant in the presence of concomitant pyuria

True urinary infections associated with fewer than 105CFU/mL

• infants and children• in males• in persons who are catheterized• recently treated with antimicrobial agents• drink large amounts of fluids (which dilutes urine)• symptoms and concomitant pyuria• urinary obstruction• pyelonephritis acquired from hematogenous spread (especially

infections due to yeast and S. aureus) • Consequently, proper interpretation of urine culture results

requires communication between clinicians and laboratory personnel.

Quantitative bacterial culture of a urine specimen is done by inoculating appropriate media with a measured amount of urine

most commonly with a plastic or wire calibrated loop designed to deliver a known volume.

A 0.001 mL loop is used to inoculate all urine specimens

except those collected from women with suspected acute urethral syndrome and suprapubic aspirates.

Both the latter are inoculated with a 0.01 mL loop.

Although the inoculating loops are calibrated to deliver the volume of urine prescribed

accuracy has an error rate of as much as 50%, particularly when using the 0.00 l-mL loop.

Vertical sampling from a small container may deliver only 50% of the prescribed volume

horizontal sampling at a 45-degree angle from a large container may deliver 150% of volume.

should be aware of these potential errors derive a standard angle for sampling in their laboratory,

based on the volume of containers being used.

• Accuracy and precision studies on the volume of inoculum can be done

• (I) photometrically• by adding a loop of gentian violet sampled from

a 60-mL reservoir of dye to 2 mL of water in a cuvette and reading it in a spectrophotometer set at 590 nm, or…..

• (2) manometrically• by noting the change in weight when a loop of

water is delivered to a tilter paper disk placed in the pan of a highly sensitive analytical balance.

روش اسپکتروفتومتری

در این روش از یک ماده رنگی که دارای جذب •نوری در طول موج خاص است استفاده می

گردد . اوانس بلو •متیلن بلو•کریستال ویوله•

• 20mg evans blue• 10 mg distilled water

با توجه به کاهش تصاعدی رقت لوله ها از کاغذ •لگاریتمی برای تهیه منحنی استاندارد استفاده میشود .

لوله ۱۰پس از ترسیم منحنی برای کالیبره کردن لوپ • میلی لیتر آب می ریزیم۱برداشته و در هر یک از آنها

به کمک لوپ از محلول رنگی در لوله ها وارد می •کنیم.

نانومتر ۶20خواندن جذب نوری آنها در طول موج • به دست آوردن میانگین جذب نوری • انتقال آن بر روی منحنی •مقدار حجم برداشته شده توسط لوپ•

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