Clinical Review

Sexually Transmitted Infections Caused by Mycoplasma genitalium and Neisseria gonorrhoeae: Diagnosis and Treatment


 

References

From the Fargo Veterans Affairs Health Care System, Fargo, ND (Dr. Dietz, Dr. Hammer, Dr. Zegarra, and Dr. Lo), and the Queen Elizabeth Hospital, Hong Kong, China (Dr. Cho).

Abstract

  • Objective: To review the management of patients with Mycoplasma genitalium and Neisseria gonorrhoeae infections.
  • Methods: Review of the literature.
  • Results: Mycoplasma genitalium and Neisseria gonorrhoeae are organisms that cause urethritis, cervicitis, and pelvic inflammatory disease. There is increasing antibiotic resistance to both organisms, which poses significant challenges to clinicians. Additionally, diagnostic tests for M. genitalium are not widely available, and commonly used tests for both organisms do not provide antibiotic sensitivity information. The increasing resistance of both M. genitalium and N. gonorrhoeae to currently used antimicrobial agents is alarming and warrants cautious monitoring.
  • Conclusion: As the yield of new or effective antibiotic therapies has decreased over the past few years, increasing antibiotic resistance will lead to difficult treatment scenarios for sexually transmitted infections caused by these 2 organisms.

Keywords: Mycoplasma genitalium, Neisseria gonorrhoeae, antibiotic resistance, sexually transmitted infections, STIs.

The World Health Organization (WHO) estimates that more than 1 million cases of sexually transmitted Infections (STIs) are acquired every day worldwide,1 and that the majority of STIs have few or no symptoms, making diagnosis difficult. Two organisms of interest are Mycoplasma genitalium and Neisseria gonorrhoeae. In contrast to Chlamydia trachomatis, which is rarely resistant to treatment regimens, M. genitalium and N. gonorrhoeae are becoming increasingly resistant to antibiotic treatment and pose an impending threat. These bacteria can cause urethritis, cervicitis, and pelvic inflammatory disease (PID). Whereas antibiotic resistance to M. genitalium is emerging, resistance to N. gonorrhea has been a continual problem for decades. Drug resistance, especially for N. gonorrhoeae, is listed as a major threat to efforts to reduce the impact of STIs worldwide.2 In 2013, the U.S. Centers for Disease Control and Prevention (CDC) classified N. gonorrhoeae drug resistance as an urgent threat.3 As the yield of new or effective antibiotic therapies has decreased over the past few years, increasing antibiotic resistance will lead to challenging treatment scenarios for STIs caused by these 2 organisms.

Epidemiology and Pathogenesis

M. genitalium

M. genitalium is an emerging pathogen that is an etiologic agent of upper and lower genital tract STIs, such as urethritis, cervicitis, and PID.4-13 In addition, it is thought to be involved in tubal infertility and acquisition of other sexually transmitted pathogens, including HIV.7,8,13 The prevalence of M. genitalium in the general U.S. population in 2016 was reported to be approximately 17.2% for males and 16.1% for females.14 Infections are more common in patients aged 30 years and younger than in older populations.15 Also, patients self-identifying as black were found to have a higher prevalence of M. genitalium.14 This organism was first reported as being isolated from the urethras of 2 men with non-gonococcal urethritis (NGU) in London in 1980.15,16 It is a significant cause of acute and chronic NGU in males, and is estimated to account for 6% to 50% of cases of NGU.17,18M. genitalium in females has been associated with cervicitis4,9 and PID.8,10 A meta-analysis by Lis et al showed that M. genitalium infection was associated with an increased risk for preterm birth and spontaneous abortion.11 In addition, M. genitalium infections occur frequently in HIV-positive patients.19,20 M. genitalium increases susceptibility for passage of HIV across the epithelium by reducing epithelial barrier integrity.19

Beta lactams are ineffective against M. genitalium because mycoplasmas lack a cell wall and thus cell wall penicillin-binding proteins.21M. genitalium’s abilty to invade host epithelial cells is another mechanism that can protect the bacteria from antibiotic exposure.20 One of the first reports of antibiotic sensitivity testing for M. genitalium, published in 1997, noted that the organism was not susceptible to nalidixic acid, cephalosporins, penicillins, and rifampicin.22 In general, mycoplasmas are normally susceptible to antibiotics that inhibit protein synthesis,23 and initial good sensitivity to doxycycline and erythromycin was noted but this has since decreased. New antibiotics are on the horizon, but they have not been extensively tested in vivo.23

N. gonorrhoeae

Gonorrhea is the second most common STI of bacterial origin following C. trachomatis,24-26 which is rarely resistant to conventional regimens. In 2008, the World Health Organization (WHO) estimated that 106 million cases of N. gonorrhoeae infection were acquired annually and that 36.4 million adults were infected with N. gonorrhoeae.27 In the United States, the CDC estimates that gonorrhea cases are under-reported. An estimated 800,000 or more new cases are reported per year.28

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