Evaluation of Two Commercial Real-Time PCR Assays for Detection of Mycoplasma genitalium in Urogenital Specimens

The performance of two commercial real-time PCR kits for the detection of Mycoplasma genitalium was evaluated in comparison to an in-house real-time PCR assay. Concordances of 96% and 93% were found for the TIB MOLBIOL and the Diagenode assays, respectively, compared to the results of the in-house assay.     

Detection and Confirmation of Mycoplasma pneumoniae in Urogenital Specimens by PCR

Following the isolation of Mycoplasma pneumoniae from urogenital specimens (M. Goulet, R. Dular, J. G. Tully, G. Billows, and S. Kasatiya, J. Clin. Microbiol. 33:2823–2825, 1995), a study was undertaken to confirm the observations by PCR. Specific primers directed to the P1 adhesin gene of M. pneumoniae were used. A total of 300 genital specimens were tested for M. pneumoniae and Mycoplasma genitalium by culture and PCR. Of these, 15 were positive by culture and 17 were positive by PCR for M. pneumoniae. No M. genitalium was detected in any of the specimens by either method. The present study demonstrates that PCR is sensitive and rapid compared to cumbersome culture methods and can be used to detect M. pneumoniae in urogenital specimens in a routine diagnostic laboratory.     

Clinical Characteristics Associated with Mycoplasma genitalium among Female Sex Workers in Nairobi,Kenya

The prevalence of Mycoplasma genitalium is high in vulnerable populations of women in low-resource settings. However, the epidemiology of infection in these populations is not well established. To determine the prevalence of Mycoplasma genitalium and its association with cervical cytology and other correlates, we recruited 350 female sex workers (FSW) who were 18 to 50 years old in Nairobi, Kenya, for a cross-sectional study. A questionnaire was administered at baseline to obtain information on sociodemographics and sexual behaviors. Women underwent a pelvic exam, during which a physician collected cervical-exfoliation samples for conventional cytology and sexually transmitted infection (STI) testing. Samples were tested for M. genitalium and other STI organisms (Chlamydia trachomatis, Neisseria gonorrhoeae, Trichomonas vaginalis) and the E6/E7 mRNA of human papillomavirus (HPV) by Aptima nucleic amplification assays. The prevalence of M. genitalium was 12.9%. FSW who engaged in sexual intercourse during menses were less likely to have M. genitalium infection than those who did not (odds ratio [OR], 0.3; 95% confidence interval [95% CI], 0.1, 0.9). M. genitalium was also less prevalent among FSW who had worked in prostitution for >5 years (6.2%) than among those who had worked for <3 years (17.6%) (OR, 0.3; 95% CI, 0.1, 0.8). FSW who reported more frequent condom use were more likely to be infected with M. genitalium than those who reported less frequent use (OR, 3.8; 95% CI, 1.2, 11.6). These correlates differ from those found in M. genitalium studies conducted with FSW from West Africa and China. Further longitudinal analyses assessing associations with persistent M. genitalium infection are needed.     

Direct Detection of Mycobacterium tuberculosis in Clinical Specimens Using Nucleic Acid Amplification Tests

Tuberculosis continues to be a significant cause of morbidity and mortality worldwide. Rapid detection of Mycobacterium tuberculosis directly in clinical specimens using nucleic acid amplification tests enables infected patients to be placed on appropriate therapy much sooner than when results of conventional culture methods are used. The availability of rapid results also facilitates infection control measures to interrupt transmission of tuberculosis in healthcare settings. The era of commercially available molecular diagnostics for detection of M. tuberculosis began 25 years ago and now encompasses multiple assays that can detect organisms in the M. tuberculosis complex. Several assays also detect chromosomal mutations associated with antimicrobial resistance to further refine therapeutic strategies early in the course of disease. NAATs have revolutionized the diagnosis of TB across the globe and have become the standard of care in many high-burden developing countries.     

Direct Detection of Macrolide Resistance in Mycoplasma genitalium Isolates from Clinical Specimens from France by Use of Real-Time PCR and Melting Curve Analysis

Mycoplasma genitalium is a sexually transmitted organism commonly treated with azithromycin. However, macrolide resistance has been reported and is associated with point mutations in the 23S rRNA gene. To evaluate the prevalence of macrolide resistance in M. genitalium isolates from clinical specimens from France, we first used a previously reported high-resolution melting assay. Because susceptible and resistant M. genitalium isolates were hardly discriminated in M. genitalium-positive clinical specimens, we developed a new molecular assay for the rapid detection of macrolide resistance. An assay using real-time PCR based on fluorescence resonance energy transfer (FRET) coupled with melting curve analysis was designed. The assay was first validated on characterized macrolide-resistant M. genitalium isolates and then applied to 202 urogenital M. genitalium-positive specimens collected from 178 patients from France in 2011 and 2012. Resistant genotypes were confirmed by 23S rRNA gene sequencing. Among the 202 M. genitalium-positive specimens, 155 were amplified, demonstrating a sensitivity of 76.7%. A substitution in the 23S rRNA gene was found in 14.2% of the patient samples. Nine and six patients had M. genitalium isolates with a substitution at positions 2059 and 2058, respectively. In four cases, a mixed population of wild-type and mutated M. genitalium isolates was observed. The prevalence of M. genitalium macrolide resistance has been stable in France since its detection in 2006. Our FRET PCR assay is able to discriminate between wild-type and resistant genotypes directly from clinical specimens. This assay will allow clinicians to shorten the time to the initiation of effective disease treatment.     

The mature MgPa-adhesin of Mycoplasma genitalium

A high molecular weight protein of Mycoplasma genitalium (MgPa-protein) was isolated by fractionated solubilization with 1% CHAPS, followed by subsequent extraction with 2% octylglucoside and size exclusion chromatography. The comparison of the N-terminal sequence reported here with published nucleotide sequence data revealed the existence of a signal sequence; the molecular weight of the mature MgPa-protein was calculated to be 153, 134 dalton. The protein shares antigenic determinants with the adhesin of Mycoplasma pneumoniae (P1-protein). Therefore the amino acid sequence of the MgPa-protein was matched to the P1-protein sequence. Five of seven computer predicted hydrophobic regions of both amino acid sequences were located in corresponding regions.     

Isothermal Detection of Mycoplasma pneumoniae Directly from Respiratory Clinical Specimens

Mycoplasma pneumoniae is a leading cause of community-acquired pneumonia (CAP) across patient populations of all ages. We have developed a loop-mediated isothermal amplification (LAMP) assay that enables rapid, low-cost detection of M. pneumoniae from nucleic acid extracts and directly from various respiratory specimen types. The assay implements calcein to facilitate simple visual readout of positive results in approximately 1 h, making it ideal for use in primary care facilities and resource-poor settings. The analytical sensitivity of the assay was determined to be 100 fg by testing serial dilutions of target DNA ranging from 1 ng to 1 fg per reaction, and no cross-reactivity was observed against 17 other Mycoplasma species, 27 common respiratory agents, or human DNA. We demonstrated the utility of this assay by testing nucleic acid extracts (n = 252) and unextracted respiratory specimens (n = 72) collected during M. pneumoniae outbreaks and sporadic cases occurring in the United States from February 2010 to January 2014. The sensitivity of the LAMP assay was 88.5% tested on extracted nucleic acid and 82.1% evaluated on unextracted clinical specimens compared to a validated real-time PCR test. Further optimization and improvements to this method may lead to the availability of a rapid, cost-efficient laboratory test for M. pneumoniae detection that is more widely available to primary care facilities, ultimately facilitating prompt detection and appropriate responses to potential M. pneumoniae outbreaks and clusters within the community.     

Absence of Mycoplasma pneumoniae cytadsorption protein P1 in Mycoplasma genitalium and Mycoplasma gallisepticum

Polyclonal and monoclonal antibodies to Mycoplasma pneumoniae protein P1 were nonreactive with whole-cell or soluble preparations of M. genitalium and M. gallisepticum. However, radioimmunoprecipitation performed with hyperimmune rabbit sera raised against each mycoplasma species indicated antigenic cross-reactivity between M. pneumoniae and M. genitalium.     

Analysis Identifying Common and Distinct Sequences among Texas Clinical Strains of Mycoplasma genitalium

Mycoplasma genitalium is a human bacterial pathogen linked to urethritis and other sexually transmitted diseases. Here, we assessed the incidence of M. genitalium infection in patients attending a sexually transmitted disease clinic in San Antonio, TX, by use of diagnostic real-time PCR. Overall, 16.8% of women and 15.1% of men were found M. genitalium positive. Regions of the mgpB gene, which encodes the MgPa adhesin, were amplified from positive clinical specimens and evaluated for sequence variability, which demonstrated transmission of the pathogen between sexual partners. Follow-up analysis of a subset of patient specimens revealed reinfection by a different strain of M. genitalium, indicating the absence of protective immunity. Eighteen DNA sequence variants were obtained and compared with all other available clinical sequences. Detailed analysis revealed silent mutations of six amino acid residues within the encoded region of the MgPa adhesin in numerous clinical strains. In addition, missense mutations of limited numbers of amino acids were observed. Alignment of putative amino acid sequences revealed the simultaneous occurrence of several mutations and the existence of identical or similar protein variants in strains from different locations.Mycoplasma genitalium is associated with numerous human genitourinary tract maladies, including nonchlamydial, nongonococcal urethritis in men and cervicitis, endometritis, and pelvic inflammatory disease in women (1, 4, 5, 12, 19, 29, 30, 35, 39). Understanding the epidemiological aspects of infections and developing effective treatment require reliable typing of pathogenic microorganisms. Since M. genitalium is very difficult to culture from clinical specimens (13, 21), classical microbiological typing methods are not readily applicable. Furthermore, serological approaches are not widely used because of cross-reactivity with other mycoplasmas, especially with Mycoplasma pneumoniae (15, 26). Therefore, typing of M. genitalium strains relies on DNA sequence data. Recently, sequence variability of the rRNA operon and tandem repeats in the MG309 locus have been evaluated with clinical specimens (28). However, the majority of M. genitalium clinical sequence data available today is based upon the gene mgpB (locus MG191 of sequenced reference strain G37 [11]) encoding the M. genitalium adhesin MgPa (14, 17, 21). An M. genitalium-specific diagnostic PCR assay was designed to target the proximal unique region of this gene (using primers MgPa-1 and MgPa-3 [22] and designated here “MgPa-13”). The MgPa-13 region has exhibited sequence stability in persistently infected patients for up to 21 months (17). Despite this intrastrain stability, high levels of sequence variability between clinical isolates were observed (14, 17). Based on this sequence region, transmission of M. genitalium between sexual partners was shown, as was colonization of different anatomical sites of the same patient by identical strains (14).Here, we present analysis of MgPa-13 sequences generated from clinical specimens collected at the Project S.A.F.E. sexually transmitted disease (STD) clinic in San Antonio, TX (36), from recruited female participants and their male partners. Alignment of MgPa-13 sequences corroborated transmission between partners and colonization of different anatomical sites by the same strain. Comparison of newly recovered sequences with all currently available clinical data (14, 17, 21) revealed not only the presence of several common variants but also distinct sequences. Analyses of encoded amino acids uncovered mutations that determine common features among MgPa-13 region variants.     

Mycoplasma genitalium Rapidly Disseminates to the Upper Reproductive Tracts and Knees of Female Mice following Vaginal Inoculation

Mycoplasma genitalium is an emerging sexually transmitted infection and in women is associated with notable reproductive tract syndromes such as cervicitis, pelvic inflammatory disease, and infertility. Investigations into the causal relationships of M. genitalium infections and clinical disease have been hindered largely by the lack of a well-established small-animal model of genital tract infection. To establish a murine model, female Swiss Webster mice were conditioned with either progesterone or estradiol and then inoculated intravaginally with M. genitalium type strain G37 or a contemporary Danish strain, M2300. Persistent lower tract infection was observed at up to 77 days postinoculation (d.p.i.). Upper reproductive tract colonization was observed as early as 3 d.p.i., with long-term infection observed in estradiol-treated (65%) and progesterone-treated (18%) animals. In the upper tract, more than 90% of M. genitalium PCR-positive samples were from the uterus and oviducts. Ultimately, gross hydrosalpinx was observed 21 days to 10 weeks p.i. in approximately 60% of infected animals, suggesting the presence of tubal occlusion. In addition, dissemination of M. genitalium to the knee tissues was observed as early as 7 d.p.i., with persistent infection detected at up to 28 d.p.i. Mice infected with M. genitalium also developed specific antibodies to the major antigenic outer membrane protein MgPa, elongation factor Tu, pyruvate dehydrogenase E1α, and DnaK (Hsp70), indicating persistent infection despite robust humoral responses to infection. These findings provide strong experimental evidence that M. genitalium can establish long-term infection of reproductive tract and joint tissues, with preliminary evidence of pathological reproductive tract outcomes.Mycoplasma genitalium is an emerging sexually transmitted pathogen that was first identified as a cause of inflammatory urogenital disease in men (reviewed in references 15 and 18). Importantly, M. genitalium infections in women have also been associated with inflammatory syndromes, including cervicitis (8, 24, 27, 32, 50) and pelvic inflammatory disease (12), and (serologically) with impaired fertility (4, 37). Mechanistically, M. genitalium has previously been shown to activate highly expressed Toll-like receptors in reproductive tract epithelia, leading to inflammation (28, 29). Collectively, these associations have led to an increased awareness of M. genitalium as a pathogen that could adversely affect reproductive health. It may also be of considerable importance that M. genitalium is strongly associated with HIV infections in men and women (reviewed in reference 31), suggesting that reproductive tract infections by M. genitalium may increase the likelihood of acquiring or transmitting other genital pathogens.Although the genital tract seems to be a preferred site of colonization, M. genitalium also has been a suspected cause of reactive arthritis, since DNA was previously detected in the knee joints of arthritic patients (45, 47) and in synovial fluid from temporomandibular joints (23). It is possible that M. genitalium may be a cause of sexually acquired reactive arthritis, but to date, no direct evidence exists for an association with an arthritic condition. Furthermore, no published reports have addressed the ability of M. genitalium to disseminate from the vagina to colonize the joint tissues or upper genital tract tissues. Similarly, there is a lack of experimental evidence for the causal associations of M. genitalium infection with inflammatory disease syndromes in women.As epidemiological data continue to implicate M. genitalium as a cause of reproductive tract disease, relevant animal models to investigate pathogenesis and evaluate therapeutic interventions are of utmost importance. Five years after the initial isolation of M. genitalium from men with urethritis (48), several large-animal species, including male cynomolgus monkeys (Macaca fascicularis), male chimpanzees (Pan troglodytes), female squirrel monkeys (Saimiri sciureus), female tamarins (Saguinus mystax), and female marmosets (Callithrix jacchus [44]), were found to be susceptible to experimental urogenital infection. These studies provided excellent preliminary evidence that M. genitalium could establish infection of female reproductive tract tissues. However, the cost of developing and maintaining primate and large-animal models prohibits experimentation employing larger-scale studies to address biological variability as part of an effective model of reproductive tract disease. In contrast, rodent models are cost-effective and afford the opportunity to investigate larger study populations of animals with specific genetic characteristics. Such models also allow evaluation of vaccines and interventions to prioritize lead compounds for subsequent study of larger species. Experiments by Furr and Taylor-Robinson and colleagues provided preliminary evidence that the type strain of M. genitalium (G37) could establish genital tract infection in inbred female BALB/c mice (10). Considering the emerging clinical associations with upper reproductive tract disease, it now seems imperative to address the capacity of M. genitalium to disseminate from the vagina and establish upper reproductive tract infection.Systemic regulation of sex hormones prior to vaginal inoculation affords several important advantages for experimental manipulation, including rendering otherwise-resistant animals susceptible to infection and arresting the reproductive cycle to synchronize the estrus phase of animals within a study (43). With regard to mycoplasmas, it is unclear why some species, such as M. pneumoniae and M. pulmonis, require progesterone treatment whereas others, including the genital pathogen M. fermentans, colonize the genital tract only following estrogen treatment (10). The mouse model proposed by Taylor-Robinson''s group showed that BALB/c mice were susceptible to vaginal M. genitalium infection only following progesterone treatment and not after estradiol benzoate treatment (40, 41). To our knowledge, this model has not been employed since for investigation of M. genitalium genital tract disease.In the present paper, we describe results compiled from more than 3 years of experimentation that show the successful establishment of a reproducible murine model to investigate M. genitalium infection of the female reproductive tract. The presented findings provide strong evidence that, following vaginal exposure of M. genitalium, the lower and upper reproductive tract tissues become persistently colonized, resulting in long-term shedding from the vagina and serious disease in more than half of the members of groups of infected animals. Animals conditioned with either estradiol or progesterone were susceptible to infection, resulting in differential rates of dissemination to upper tract tissues and the development of hydrosalpinx. Importantly, colonization of the knee joints was also observed, providing evidence that M. genitalium can disseminate from the vagina to colonize synovial sites as well. A reproducible small-animal model to study M. genitalium pathobiology would be indispensable for continued investigation into the mechanisms of disease and coinfection with other sexually transmitted infection (STI) pathogens and for evaluation of novel therapeutics, preventatives, and vaccines.     

Serological investigation of Mycoplasma genitalium in infertile women

BACKGROUND: The role of Mycoplasma genitalium in the pathogenesis of pelvic inflammatory disease has not been characterized. METHODS: Sera from 308 infertile women were investigated for antibodies to M. genitalium by immunoblotting. Women with tubal factor infertility (TFI) made up 132 of the patients, 67 of the women had an infertile male partner and 109 were infertile for unknown reasons. RESULTS: Of the TFI patients 29 (22.0%) were seropositive to the major adhesin, MgPa, of M. genitalium versus 11 (6.3%) in the group of women with normal tubes. No cross-reactions between MgPa and P1 of the related Mycoplasma pneumoniae were found. Besides, MgPa positive sera were confirmed by immunoblotting using a cloned fragment of the C-terminal part of MgPa specific to M. genitalium. Chlamydia trachomatis is known to be able to cause infertility as a result of salpingitis. Therefore, the sera were tested against C. trachomatis using a commercial ELISA test. Seventy-five (56.8%) of the TFI patients were seropositive to C. trachomatis. Eight (27.6%) TFI patients seropositive to MgPa were negative to C. trachomatis. CONCLUSIONS: This study indicates that M. genitalium may be an independent risk factor in the development of an inflammatory process leading to scarring of the uterine tubes in women and thereby causing infertility.     

Diagnostic assessment of Mycoplasma genitalium in culture-positive women

Detection of Mycoplasma genitalium-mediated, chlamydia-negative nongonococcal urethritis and other M. genitalium-linked infectious etiologies has been very challenging. Although M. genitalium is considered a leading cause of genitourinary symptoms in men and women, extreme difficulties in its cultivation due to its highly fastidious nature and the lack of routine and effective diagnostic tests have slowed the generation of clinical data which directly implicate the presence of M. genitalium in disease pathogenesis. In this study, we compared enzyme-linked immunosorbent assays (ELISAs) and immunoblot and PCR assays in M. genitalium culture-positive women over 1 to 3 years of clinical visits to determine the usefulness of independent diagnostic strategies. Furthermore, the value of combinatorial diagnostic assessments is described, which provides insights into the dynamics of M. genitalium-host interactions. Overall, we show that neither ELISA nor PCR, alone or in combination, provides the sensitivity required to confidently predict the existence of viable M. genitalium organisms in cervical and vaginal samples. Additionally, culture-positive women exhibited a range of antibody responsiveness to M. genitalium based upon ELISA and immunoblot assessments, indicating immune diversity among this high-risk population.     

Homologous regions shared by adhesin genes of Mycoplasma pneumoniae and Mycoplasma genitalium

A lambda gt11 library of Mycoplasma genitalium genomic DNA was generated, and clones were identified using a pool of monoclonal antibodies directed against different epitopes of the 140 kDa adhesin protein. Because the 140 kDa protein of M. genitalium and the 170 kDa P1 adhesin of M. pneumoniae share biological properties such as a tip-associated location, cytadherence function and immunologic crossreactivity, we performed Southern blot analysis using these cloned partial 140 kDa gene fragments and 14 subclones that span the P1 structural gene of M. pneumoniae. Homologous regions of the two genes were identified.     

Sequence-based typing of Mycoplasma genitalium reveals sexual transmission

Mycoplasma genitalium causes male nonchlamydial, nongonococcal urethritis and is associated with cervicitis and pelvic inflammatory disease in women. Epidemiological studies indicate that M. genitalium is sexually transmitted, and the aim of the present study was to further substantiate this by means of a DNA typing system. A typing assay based on a diagnostic mgpB gene PCR was developed, evaluated, and applied directly to urogenital specimens. The assay had a low limit of detection and hence a high typeability. Sequences of isolates from 52 unrelated patients were divided into 29 different sequence types, giving a discriminatory index of 0.95. Two to six M. genitalium-positive specimens were collected from each of 44 patients over a median interval of 56 days (range, 11 to 1,395). Forty had the same sequence type in consecutive specimens. Specimens collected from two men were repeatedly positive at intervals of 472 and 1,395 days, respectively, but the sequence types had changed. A new strain was introduced in one sexual dyad, and the sequence types changed subsequently. Seventy-nine M. genitalium-positive specimens from 19 couples were investigated, and all partners initially had concordant sequence types, but one couple had discordant types at one time point before a newly introduced strain took over. The present typing system is simple and reproducible and has an excellent discriminatory capacity which might prove useful in studies of sexual networks and for evaluation of treatment failures. In the laboratory, this system may document the uniqueness of newly isolated M. genitalium strains.     

DNA probes for detection and identification of Mycoplasma pneumoniae and Mycoplasma genitalium.

DNA probes specific for Mycoplasma pneumoniae and Mycoplasma genitalium were selected from genomic libraries prepared in pUC13. The 32P-labeled probes could detect, by dot blot hybridization, down to about 0.1 ng of the specific mycoplasma DNA or 10(5) CFU. Biotinylation of probe decreased the sensitivity of detection and produced nonspecific background reactions with nonhomologous DNAs. Sulfonation of probe yielded a similar level of sensitivity with less background.     

Comparison of two Mycoplasma genitalium real-time PCR detection methodologies

Established in-house quantitative PCR (qPCR) assays to detect the Mycoplasma genitalium adhesion protein (MgPa) and the 16S rRNA gene were found to be comparable for screening purposes, with a kappa value of 0.97 (95% confidence interval [CI], 0.94 to 1.01) and no difference in bacterial load quantified (P = 0.4399).