Multigeographic clinical assessment of a molecular diagnostic assay for detection of key codons to predict decreased susceptibility or resistance to cephalosporins in Neisseria gonorrhoeae

Cephalosporin resistance in Neisseria gonorrhoeae has severely compromised the efficacy of World Health Organization (WHO)-recommended therapies. This study aimed to methodologically evaluate the optimized Six-CodonPlus assay, and additionally conducted a multicenter evaluation to assess its clinical application, especially for predicting antimicrobial resistance (AMR). For methodological evaluation, 397 sequence-known N. gonorrhoeae isolates were evaluated for specificity, 17 nongonococcal isolates were assessed for cross-reactivity, 159 uncultured urogenital swabs and urine samples were evaluated for sensitivity at the clinical level. For multicenter evaluation, 773 isolates with confirmed phenotypic data and 718 clinical urogenital swabs collected from four geographical cities were, respectively, utilized for the evaluation of AMR-prediction strategies and the clinical application of the assay. The assay accurately identified specific single-nucleotide polymorphisms in resistance-associated genes, the detection limits dropped to 10 copies/reaction for individual targets. The specificity reached 100% and no cross-reactivity occurred with double-target confirmation. The assay could be directly applied to clinical samples containing over 20 copies/reaction. Multicenter evaluation formulated two optimal strategies for decreased susceptibility prediction in specific scenarios, and one tactic for prediction of resistance and identification of FC428-like strains. High sensitivity of 86.84% (95% CI, 71.11-95.05) and specificity of 99.59% (95% CI, 98.71-99.89) for resistance prediction were demonstrated for ceftriaxone (CRO). Regarding N. gonorrhoeae identification among multicenter swabs, specificity reached 97.53% (95% CI, 95.49-98.69), and sensitivity reached 93.77% (95% CI, 90.04-96.22). The Six-CodonPlus assay exhibited excellent detection performance and formulated optimal AMR-related prediction strategy with regional adaptability, providing critical information for population screening and clinical treatment.

Highlighting the clinical need for diagnosing Mycoplasma genitalium infection

Despite Mycoplasma genitalium (MG) being increasingly recognised as a genital pathogen in men and women, awareness and utility of commercially available MG-testing has been low. The opinion of UK sexual health clinicians and allied professionals was sought on how MG-testing should be used. Thirty-two consensus statements were developed by an expert group and circulated to clinicians and laboratory staff, who were asked to evaluate their level of agreement with each statement; 75% agreement was set as the threshold for defining consensus for each statement. A modified Delphi approach was used and high levels of agreement obviated the need to test the original statement set further. Of 201 individuals who received questionnaires, 60 responded, most (48) being sexual health consultants, more than 10% of the total in the UK. Twenty-seven (84.4%) of the statements exceeded the 75% threshold. Respondents strongly supported MG-testing of patients with urethritis, pelvic inflammatory disease or unexplained persistent vaginal discharge, or post-coital bleeding. Fewer favoured testing patients with proctitis and support was divided for routinely testing Chlamydia-positive patients. Testing of current sexual contacts of MG-positive patients was supported, as was a test of cure for MG-positive patients, although agreement fell below the 75% threshold. Respondents agreed that all consultant- or specialist-led services should have access to testing for MG (98.3%). There was strong agreement for having MG-testing available for specific patient groups, which may reflect concern over antibiotic resistance and the desire to comply with clinical guidelines that recommend MG-testing in sexual health clinic settings.

Mycoplasma genitalium Infection in Men

Mycoplasmagenitalium is one of the major causes of nongonococcal urethritis (NGU) worldwide but an uncommon sexually transmitted infection (STI) in the general population. The risk of sexual transmission is probably lower than for Chlamydia trachomatis. Infection in men is usually asymptomatic and it is likely that most men resolve infection without developing disease. The incubation period for NGU caused by Mycoplasma genitalium is probably longer than for NGU caused by C. trachomatis. The clinical characteristics of symptomatic NGU have not been shown to identify the pathogen specific etiology. Effective treatment of men and their sexual partner(s) is complicated as macrolide antimicrobial resistance is now common in many countries, conceivably due to the widespread use of azithromycin 1 g to treat STIs and the limited availability of diagnostic tests for M. genitalium. Improved outcomes in men with NGU and better antimicrobial stewardship are likely to arise from the introduction of diagnostic M. genitalium nucleic acid amplification testing including antimicrobial resistance testing in men with symptoms of NGU as well as in their current sexual partner(s). The cost effectiveness of these approaches needs further evaluation. The evidence that M. genitalium causes epididymo-orchitis, proctitis, and reactive arthritis and facilitates human immunodeficiency virus transmission in men is weak, although biologically plausible. In the absence of randomized controlled trials demonstrating cost effectiveness, screening of asymptomatic men cannot be recommended.

Developing a Public Health Response to Mycoplasma genitalium

Although Mycoplasma genitalium is increasingly recognized as a sexually transmitted pathogen, at present there is no defined public health response to this relatively newly identified sexually transmitted infection. Currently available data are insufficient to justify routinely screening any defined population for M. genitalium infection. More effective therapies, data on acceptability of screening and its impact on clinical outcomes, and better information on the natural history of infection will likely be required before the value of potential screening programs can be adequately assessed. Insofar as diagnostic tests are available or become available in the near future, clinicians and public health agencies should consider integrating M. genitalium testing into the management of persons with sexually transmitted infection (STI) syndromes associated with the infection (ie urethritis, cervicitis, and pelvic inflammatory disease) and their sex partners. Antimicrobial-resistant M. genitalium is a significant problem and may require clinicians and public health authorities to reconsider the management of STI syndromes in an effort to prevent the emergence of ever more resistant M. genitalium infections.

Prevalence and antibiotic resistance of Mycoplasma genitalium among STI clinic attendees in Western Canada: a cross-sectional analysis

OBJECTIVES

To determine the prevalence and correlates of Mycoplasma genitalium (MG) infection among men and women, determine the prevalence of gene mutations conferring resistance and compare test performance of female specimen types.

METHODS

A cross-sectional study was conducted on specimens collected for gonorrhoea (NG, Neisseria gonorrhoeae) and chlamydia (CT, Chlamydia trachomatis) among male and female Alberta STI clinic attendees using the M. genitalium transcription-mediated amplification-research use only test. Positive specimens were sequenced for 23SrRNA, parC and gyrA genes. Gender-stratified analysis compared test results using χ2 or Fisher's exact test, Mann-Whitney U test and logistic regression. Female endocervical and urine specimens were compared.

RESULTS

A total of 2254 individuals were tested; 53.8% (n=1212) were male. Male prevalence of MG was 5.3%; CT was 5.9% and NG was 1.8%. Correlates of male infection were a non-gonococcal urethritis diagnosis and NG coinfection. MG prevalence for women was 7.2%; CT was 5.8% and NG was 1.8%. Correlates of female infection were younger age, Indigenous/Other ethnicity and CT/NG coinfection. Nearly two-thirds of eligible specimens had mutations associated with macrolide resistance and 12.2% of specimens had a parC mutation signifying possible moxifloxacin resistance. There was high concordance (98.1%) of results between urine and endocervical swabs.

CONCLUSIONS

The high prevalence of MG relative to CT and NG supports the incorporation of MG testing into routine sexually transmissible infection screening. The high rate of resistance to macrolides and moxifloxacin raises concerns about treatment options. The good concordance of results between urine and endocervical swabs supports the use of female urine specimens for testing.

2016 European guideline on the management of non-gonococcal urethritis

We present the updated International Union against Sexually Transmitted Infections (IUSTI) guideline for the management of non-gonococcal urethritis in men. This guideline recommends confirmation of urethritis in symptomatic men before starting treatment. It does not recommend testing asymptomatic men for the presence of urethritis. All men with urethritis should be tested for Chlamydia trachomatis and Neisseria gonorrhoeae and ideally Mycoplasma genitalium using a nucleic acid amplification test (NAAT) as this is highly likely to improve clinical outcomes. If a NAAT is positive for gonorrhoea, a culture should be performed before treatment. In view of the increasing evidence that azithromycin 1 g may result in the development of antimicrobial resistance in M. genitalium, azithromycin 1 g is no longer recommended as first line therapy, which should be doxycycline 100 mg bd for seven days. If azithromycin is to be prescribed an extended course of 500 mg stat, then 250 mg daily for four days is to be preferred over 1 g stat. In men with persistent NGU, M. genitalium NAAT testing is recommended if not previously undertaken, as is Trichomonas vaginalis NAAT testing in populations where T. vaginalis is detectable in >2% of symptomatic women.