A set of MRSA isolates can always be compared
on the basis of their susceptibility to a range of rapid results and, above all, is cheap and readily
available in the routine microbiology laboratory.
The major disadvantages are poor discriminatory
ability and lack of reproducibility. Antibiotic resistance
patterns are, to some extent, influenced by the
local environment. Thus, the same antibiogram may
be produced by unrelated strains as a consequence
of the similar selective pressure upon them. It is
equally possible that the antibiograms of two isolates
from the same clone may differ due to the
acquisition or loss of plasmids carrying resistance
genes.
It has been found in practice that a simple categorization
of antibiotics into susceptible and resistant
often cannot discriminate between unrelated strains.
Antibiograms based on relative zone sizes, compared
by direct measurement or with more complicated
computer aided formulae, have also been evaluated.
7,8 In one epidemiological investigation the
quantitative antibiogram was as useful as ribotyping.
8 However, it is not clear how much the results
may be affected by changes in culture conditions or
transfer of plasmids as no assessment of reproducibility
was made.
Strain differentiation has also been increased by
extending the range of antibiotics and other types of
antimicrobial substances tested for each isolate.9
Inevitably some agents will have no discriminatory
value but this can only be assessed once all isolates
have been examined. The time taken to perform the
extra tests, in some cases for no reward, has limited
the appeal of this approach. Some workers may also
feel that the inclusion of toxic chemicals, such as
mercury and ethidium bromide, into the scheme
makes it inappropriate for use in a routine laboratory.
In most circumstances, the antibiogram cannot
be used as the sole typing method for MRSA.
Sometimes, however, the susceptibility pattern of an
endemic or epidemic clone may be so distinctive that
an antibiogram is a useful screening method. In one
outbreak, resistance to rifampicin was used to distinguish
a new strain from those already present in
the hospital thereby excluding staphylococci which
needed no further typing.
A set of MRSA isolates can always be comparedon the basis of their susceptibility to a range of rapid results and, above all, is cheap and readilyavailable in the routine microbiology laboratory.The major disadvantages are poor discriminatoryability and lack of reproducibility. Antibiotic resistancepatterns are, to some extent, influenced by thelocal environment. Thus, the same antibiogram maybe produced by unrelated strains as a consequenceof the similar selective pressure upon them. It isequally possible that the antibiograms of two isolatesfrom the same clone may differ due to theacquisition or loss of plasmids carrying resistancegenes.It has been found in practice that a simple categorizationof antibiotics into susceptible and resistantoften cannot discriminate between unrelated strains.Antibiograms based on relative zone sizes, comparedby direct measurement or with more complicatedcomputer aided formulae, have also been evaluated.7,8 In one epidemiological investigation thequantitative antibiogram was as useful as ribotyping.8 However, it is not clear how much the resultsmay be affected by changes in culture conditions ortransfer of plasmids as no assessment of reproducibilitywas made.Strain differentiation has also been increased byextending the range of antibiotics and other types ofantimicrobial substances tested for each isolate.9Inevitably some agents will have no discriminatoryค่าแต่นี้สามารถเท่านั้นสามารถประเมินเมื่อแยกทั้งหมดมีการตรวจสอบ เวลาที่ใช้ดำเนินการทดสอบเพิ่มเติม ในบางกรณีสำหรับรางวัลไม่ ถูกจำกัดอุทธรณ์ของวิธีการนี้ บางคนอาจจะรวมของสารเคมีที่เป็นพิษ เช่นปรอทและ ethidium โบรไมด์ เป็นโครงร่างทำให้ไม่เหมาะสมสำหรับใช้ในห้องปฏิบัติการตามปกติในกรณีส่วนใหญ่ antibiogram ไม่สามารถใช้เป็นวิธีการพิมพ์แต่เพียงผู้เดียวสำหรับ MRSAบางครั้ง อย่างไรก็ ตาม ภูมิไวรับรูปแบบของการโคลนวี่ หรือเรื้อรังอาจจะโดดเด่นมากที่antibiogram การคือ วิธีการตรวจที่มีประโยชน์ ในหนึ่งระบาด rifampicin เพื่อใช้แยกความแตกต่างต้องใช้ใหม่จากที่มีอยู่แล้วในโรงพยาบาลจึงไม่รวม staphylococci ซึ่งต้องไม่มีสิ่งพิมพ์เพิ่มเติม
การแปล กรุณารอสักครู่..
