Merck Manual

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Margaret R. Hammerschlag

, MD, State University of New York Downstate Medical Center

Last full review/revision May 2021| Content last modified May 2021
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Mycoplasmas are ubiquitous bacteria that differ from other prokaryotes in that they lack a cell wall.

Increasing evidence suggests that Mycoplasma genitalium and Ureaplasma urealyticum cause some cases of nongonococcal urethritis. They (and Mycoplasma hominis) are often present in patients with other urogenital infections (eg, vaginitis, cervicitis, pyelonephritis, pelvic inflammatory disease) and some nonurogenital infections, but their role in these infections is not clear.

Mycoplasmas are not visible with light microscopy. Culture is technically difficult and often unavailable, but laboratory diagnosis is possible with nucleic acid amplification tests (NAATs) or by detection of antibodies (for M. pneumoniae); frequently, diagnosis must be by exclusion. There are now two NAATs available for M. pneumoniae as part of commercially available panels that test for multiple respiratory pathogens. NAATs approved by the U.S. Food and Drug Administration (FDA) that detect M. genitalium are now commercially available.

Treatment of Mycoplasmas

  • Macrolide antibiotics

  • Sometimes fluoroquinolones or tetracyclines

Macrolides are usually the antimicrobials of choice. Most species are also sensitive to fluoroquinolones and tetracyclines. Macrolide resistance in M. pneumoniae has been reported in > 80% of isolates in China and Japan. Preliminary data show the prevalence of resistance may be as high as 12% in the US. Therefore, fluoroquinolones or tetracyclines should be considered in patients with refractory disease, especially in areas with significant macrolide resistance. M. genitalium has been developing widespread resistance to macrolides, tetracyclines, and fluoroquinolones, which makes treating infection with this organism a challenge.

NAATs to detect macrolide resistance in M. pneumoniae and M. genitalium are currently being developed.

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