m gentialium

as a followup to my recent blog on the CDC guidelines for sexually-transmitted diseases (see http://gmodestmedblogs.blogspot.com/2015/06/new-std-treatment-guidelines.html ), there was a recent study looking at Mycoplasma genitalium resistance in the Netherlands (see STD m genitalium resistance jantimicchemo2015​ in dropbox, or doi:10.1093/jac/dkv136). and this comes right after the comment from prior my blog noting that M genitalium  "does respond to 1-g single dose of azithromycin (though resistance is emerging)". (I will highlight the section on M genitalium below, since it seems to becoming an increasingly important actor on the STD stage). details of the Netherlands study:

--​they looked at all urogenital samples from Feb 2012 to Nov 2014 in the east of the Netherlands to identify the frequency of gene mutations associated with macrolide-resistance
--44 of the 146 samples (30.1% overall, from  55 males and 91 females) had 1 of 3 mutations associated with macrolide resistance
--treatment failure was noted in 4 patients. in 1 patient, using moxifloxacin resulted in microbiologic cure.

in contradistinction to the CDC guidelines below, the above authors state: "M genitalium infections should be treated with the macrolide antibiotic azithromycin, preferably using the 1.5g extended course (500mg once, followed by 250 mg/day for 4 days), since a 1 g single-dose treatment has been shown to lead to a greater development of resistance to macrolide antibiotics". so, not sure how to reconcile this with the CDC recommendations for the 1 gram single dose. and this is, i think, a pretty important issue, with the emergence of M gentalium as a major pathogen causing urethritis, cervicitis, PID and possibly infertility in women (see below). the above study was preliminary, since they did not have great specific followup data on the outcomes of therapy.  but this does further raises the issue of emerging azithromycin resistance, and suggests:
    --that it would be useful for local labs or the public health department to periodically test samples for M genitalium and specific gene sites for azithro resistance, and let us know how things are going. and also track clinical resistance to azithro
    --i'm not sure what to make of the comment that the 5-day course of azithro is better than a single dose of azitho. in my search i could not find data on the 5-day course for chlamydia (though it would make sense, given the efficacy of longer courses of doxy) , so without that data, i would be hesitant to use the longer course of therapy even for patients who are highly likely to adhere to the longer therapy
    ​--but the real take-home message is that we are likely to see increasing M genitalium resistance in the US, that we should still treat as we are with azithro and ceftriaxone empirically to cover the major pathogens, but that we should be very aware of potential resistance and switch to moxifloxacin if clinically appropriate....
    ​--it should be noted, however, both that azithro resistance is happening in other countries (eg, a recent study found 39% of specimens were resistant in Australia), and there is the beginning of emergence of moxifloxacin resistance (another Australian study recently found 43% azithro resistance and 15% fluoroquinolone resistance, with documented cases of clinical resistance to azithro and moxifloxacin).

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