Tigecycline is often used for the treatment by Acinetobacter but its breakpoint for Acinetobacter is not prescribed and most of the researcher use criteria for Enterobacteriaceae i.e disk diffusion breakpoints at ≥19 mm and ≤14 mm, but some of the researcher claims using this value gives an unacceptable error of 23.3% (Multicenter Studies of Tigecycline Disk Diffusion Susceptibility Results for Acinetobacter spp. http://jcm.asm.org/content/45/1/227.full)
Is there any standard range addressing about it?
Only 19mm . Whats that mean resistance value or sensitive value!!!
What is the breakpoints range??
Dear Colleague,
EUCAST and CLSI do not have enough evidence to assess susceptibility breakpoints for tigecycline. I am not sure one should use Enterobacteriaceae data, they are not applicable to non fermenters.
If you are in the lab, do not report Tigecycline by disk diffusion. I don't. If you are in the clinic, be careful when you use it in immunocompromised patients (like leukemia). But if you are an epidemiologist, you are lucky because you can apply control measures, since this is a nosocomial bug and its transmission is related to contaminated water and liquid drops, like the water in flower bowls in patient's rooms.
Dear Raluca,
I have gone through lots of literature and most of the researchers have use the breakpoint range of Enterobacteriaceae for the analysis of their data but some researcher doubt over that breakpoint range. So I am searching for any other standard range.
And I'm not in the lab and in Clinic, I need it for the analysis of my thesis work .
Thank you for your suggestion
Dear Saroj,
If your aim is scientific, then I suggest to use E-test, if available to make your determinations. Otherwise, be careful and study the patient outcome each time you have the chance. Make the necessary correlations. I too, doubt about non-standard ranges, since it is a new molecule and assumption of susceptibility may lead to overuse and may compromise an new agent.
Good luck!
I'm afraid nobody is giving you a definitive response, because there is not. FDA criteria recommends 19mm for susceptibility and 14 mm for resistance, bur other authors reduce the diameter for susceptibility to 16 mm. Authors use these criteria though they was initially defined not for Acinetobacter, but for enterobacteria. CLSI and EUCAST have not defined criteria for Acinetobacter. This is a real problema in clinics. Being for your thesis work, I would evaluate both breakpoint; this may give you a very interesting point for discussion.
I was not thinking about using both breakpoint range. Yeah using both could bring interesting point during discussion. I will definitely use both range during analysis lets see how the result will varies.
Thank you Jaun Luis sir for the suggestion.
EUCAST & CLSI have not established a breakpoint for Acinetobacter & tigecycline.
Testing is extremely difficult when using disk diffusion or E-test as there are only certain manufacturers of MH agar that have the correct manganese content in their agar, which can seriously effect your results. MH from Merck & Difco have lower manganese content than Oxoid media (around 195 vs. 409 ppm). It has also been reported that other cations, like magnesium & calcium interfere with the activity of tigecycline. You can consult the following article for more info: J Clin Microbiol 2010;48(6):2243-2246.
Given the fact that this drug is a bacteriostatic, not bactericidal, I think that a comment on patient's neutrophyl count may raise awareness, especially in young doctors. Patients having neutropenia do not benefit from bacteriostatic drugs.
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