August 23, 2017
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Researchers detect rare resistance mutation in UTI-causing pathogen

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Researchers from the University of Florida said they have discovered a rare mutation conferring antibiotic resistance in Ureaplasma parvum — a pathogen that causes urinary tract infections.

“To our knowledge, this is the first report of this specific mutation in Ureaplasma in the United States, and only the third report anywhere in the world,” Mary B. Brown, PhD, professor in the department of infectious diseases and immunology at the College of Veterinary Medicine, University of Florida, said in a press release.

The mutation was detected during the first study of its kind to assess antibiotic resistance levels among college-aged women with urinary tract infections (UTIs). Brown and Marissa A. Valentine-King, MPH, RN, of the department of environmental and global health at the College of Public Health and Health Professions, University of Florida, examined data on 180 patients, 19% of whom had recurrent UTI episodes. The most common uropathogen the researchers detected was Escherichia coli. However, 53% of women with a first-time UTI and 51.4% with recurrent UTIs had Ureaplasma spp. or Mycoplasma hominis as a primary or secondary uropathogen. These bacteria lack cell walls, making them insusceptible to antibiotics that are designed to interfere with cell wall synthesis such as penicillin and beta-lactamases, Brown said in the release.

Brown and Valentine-King further analyzed 60 U. parvum isolates, 13 U. urealyticum isolates and 10 M. hominis isolates. They reported that the rate of antibiotic resistance was low, with less than 3% of isolates exhibiting resistance. Specifically, they found that one U. parvum isolate was resistant to levofloxacin (MIC = 4 g/mL) and another was resistant to tetracycline (MIC = 8 g/mL).

Additional analyses revealed that the levofloxacin-resistant isolate contained a mutation in the gene parC. This mutation, known as S83W, was detected in U. parvum only twice before — the first time in Japan and again in China in 2015. According to Brown, the isolate also appeared to be resistant to ciprofloxacin. She suggested that it may have resistance to other quinolones as well because it is located in the quinolone resistance region of parC. However, additional testing was not completed.

Despite the overall low levels of antibiotic resistance detected during the study, the researchers concluded that clinician researchers should consider periodic surveillance of antibiotic-resistant mycoplasmas such as Ureaplasma and M. hominis, which are not routinely tested in laboratories.

“As elevated levels of [tetracycline resistance] exist regionally and sexual transmission serves as the primary transmission pathway for Ureaplasma spp. and M. hominis in adults, strains harboring this gene could easily spread,” they wrote. “Thus, periodic surveillance can alert providers to changes in regional antibiotic resistance patterns, so they can adjust their empirical treatment selection accordingly to choose the most effective treatment.” – by Stephanie Viguers

Disclosure: Valentine-King reports receiving grant support from the NIH’s National Center for Advancing Translational Sciences.