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Excited to share this paper on effects of antibiotics on the gastrointestinal resistome in immunocompromised kids! Punchline: prophylactic antibiotics increase resistance to themselves, but *not* to other antibiotics. 
@StJudeResearch https://reader.elsevier.com/reader/sd/pii/S2666524720302020?token=F8E7DCE39750A121320631A00E5BD64296E6884F5852CECFD71AA749258F2E5648FFE7FD81B32BB465E295B9661FC544
@StJudeResearch https://reader.elsevier.com/reader/sd/pii/S2666524720302020?token=F8E7DCE39750A121320631A00E5BD64296E6884F5852CECFD71AA749258F2E5648FFE7FD81B32BB465E295B9661FC544
We used NGS to quantify antibiotic resistance genes in poop samples collected from 49 kids with acute lymphoblastic leukemia before and after intensive induction chemotherapy. All got trimethoprim-sulfamethoxazole (Bactrim or Septra) prophylaxis and some also got levofloxacin.
We found *all* kids had a massive increase in abundance of genes conferring resistance to trimethoprim-sulfamethoxazole, which is universally used to prevent Pneumocystis pneumonia (PCP). [P<0.0001]
![We found *all* kids had a massive increase in abundance of genes conferring resistance to trimethoprim-sulfamethoxazole, which is universally used to prevent Pneumocystis pneumonia (PCP). [P<0.0001]](https://pbs.twimg.com/media/EuW6hfZXAAAUqjv.png "We found *all* kids had a massive increase in abundance of genes conferring resistance to trimethoprim-sulfamethoxazole, which is universally used to prevent Pneumocystis pneumonia (PCP). [P<0.0001]")
But, *only* kids who received the levofloxacin prophylaxis had a significant increase in the prevalence of gene mutations that confer fluoroquinolone resistance. [P<0.0001]
![But, *only* kids who received the levofloxacin prophylaxis had a significant increase in the prevalence of gene mutations that confer fluoroquinolone resistance. [P<0.0001]](https://pbs.twimg.com/media/EuW7DLvXYC07HFC.png "But, *only* kids who received the levofloxacin prophylaxis had a significant increase in the prevalence of gene mutations that confer fluoroquinolone resistance. [P<0.0001]")
There was *no other difference* in resistance genes between kids who got levofloxacin prophylaxis or not.
This is kind of reassuring. We had been worried that levofloxacin prophylaxis might increase *cross-resistance* to other antibiotics, but it seems like it doesn't. It does make us worried about long-term effectiveness, though.
This work was done by an amazing team, none of whom are on Twitter AFAIK!!!!
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