Mycoplasma genitalium Nonadherent Phase Variants Arise by Multiple Mechanisms and Escape Antibody-Dependent Growth Inhibition

Mycoplasmoides genitalium nucleic acid semi-quantitation and molecular macrolide resistance detection via automated assays: gender and specimen source considerations

A laboratory-developed test (LDT) using analyte-specific reagents has been optimized on a commercial platform to detect macrolide resistance-associated mutations (MRM) in 23S rRNA from Mycoplasmoides genitalium from primary clinical specimens. In this study, MRM-LDT was applied to a multi-specimen source study set. One thousand four hundred ninety-five primary specimens testing positive for M. genitalium by commercial transcription-mediated amplification (TMA) were initially titered by the TMA assay using serial 10-fold dilutions to semi-quantitate target nucleic acid burden. Primary specimens were then processed for MRM detection using the MRM-LDT. Findings were stratified by gender and specimen source. The mean log10 target nucleic acid titer of a TMA-positive specimen was 3.51 (median 3; range 0-10). Male specimens (n = 1145) demonstrated a mean log10 M. genitalium TMA titer of 3.67; that value observed in 350 female specimens was 2.98 (P < 0.0001). The MRM-LDT detection rate (88.7%) from specimens with log10 M. genitalium TMA titers ≥ 4 was increased over specimens with log10 titers ≤ 1 (4.5%; P < 0.0002). In females, MRM-LDT was positive from 51.3% of vaginal swab and 34.7% of urine specimens (P = 0.01). In males, MRM-LDT was positive from 65.0% of rectal swab and 55.7% of urine specimens (P = 0.002). Differences were also observed in log10 M. genitalium TMA titers as a function of specimen source. M. genitalium macrolide resistance rates among multiple specimen sources, as determined by MRM-LDT, are high in the United States and can be consistent with target nucleic acid burden within the primary specimen. Caveats experienced within subgroupings support MRM reflex testing on primary M. genitalium-positive specimens.

IMPORTANCE

First-line macrolide treatment failure is of increasing concern with Mycoplasmoides genitalium in multiple settings. Recent sexually-transmitted infection treatment guidelines from the United States Centers for Disease Control and Prevention have predicated therapeutic approaches on the availability of a macrolide resistance/susceptibility result from a primary clinical specimen. In this report, we investigate potential correlation between macrolide resistance mutation detection rates (identified by a molecular amplified laboratory-developed test) and transcription-mediated amplification-based rRNA target semi-quantitation. Data reveal that rRNA semi-quantitation and laboratory-developed test detection rate differences exist as a function of gender and specimen source. These data can guide providers in proper specimen selection not only for the laboratory diagnosis of M. genitalium but also macrolide resistance mutation determination from primary clinical specimens.

Unveiling the stealthy tactics: mycoplasma's immune evasion strategies

Mycoplasmas, the smallest known self-replicating organisms, possess a simple structure, lack a cell wall, and have limited metabolic pathways. They are responsible for causing acute or chronic infections in humans and animals, with a significant number of species exhibiting pathogenicity. Although the innate and adaptive immune responses can effectively combat this pathogen, mycoplasmas are capable of persisting in the host, indicating that the immune system fails to eliminate them completely. Recent studies have shed light on the intricate and sophisticated defense mechanisms developed by mycoplasmas during their long-term co-evolution with the host. These evasion strategies encompass various tactics, including invasion, biofilm formation, and modulation of immune responses, such as inhibition of immune cell activity, suppression of immune cell function, and resistance against immune molecules. Additionally, antigen variation and molecular mimicry are also crucial immune evasion strategies. This review comprehensively summarizes the evasion mechanisms employed by mycoplasmas, providing valuable insights into the pathogenesis of mycoplasma infections.

Update in Epidemiology and Management of Mycoplasma genitalium Infections

Mycoplasma genitalium is a frequent cause of urogenital syndromes in men and women and is associated with adverse sequelae in women. M genitalium also infects the rectum, and may cause proctitis, but rarely infects the pharynx. Diagnosis requires nucleic acid amplification testing. Antibiotic resistance is widespread: more than half of infections are resistant to macrolides and fluoroquinolone resistance is increasing. Resistance-guided therapy is recommended for symptomatic patients, involving initial treatment with doxycycline to reduce organism load followed by azithromycin for macrolide-sensitive infections or moxifloxacin for macrolide-resistant infections. Neither screening nor tests of cure are recommended in asymptomatic persons.

Pathogenicity and virulence of Mycoplasma genitalium: Unraveling Ariadne's Thread

Mycoplasma genitalium, a pathogen from class Mollicutes, has been linked to sexually transmitted diseases and sparked widespread concern. To adapt to its environment, M. genitalium has evolved specific adhesins and motility mechanisms that allow it to adhere to and invade various eukaryotic cells, thereby causing severe damage to the cells. Even though traditional exotoxins have not been identified, secreted nucleases or membrane lipoproteins have been shown to cause cell death and inflammatory injury in M. genitalium infection. However, as both innate and adaptive immune responses are important for controlling infection, the immune responses that develop upon infection do not necessarily eliminate the organism completely. Antigenic variation, detoxifying enzymes, immunoglobulins, neutrophil extracellular trap-degrading enzymes, cell invasion, and biofilm formation are important factors that help the pathogen overcome the host defence and cause chronic infections in susceptible individuals. Furthermore, M. genitalium can increase the susceptibility to several sexually transmitted pathogens, which significantly complicates the persistence and chronicity of M. genitalium infection. This review aimed to discuss the virulence factors of M. genitalium to shed light on its complex pathogenicity and pathogenesis of the infection.

Molecular Tools for Typing Mycoplasma pneumoniae and Mycoplasma genitalium

Mycoplasma pneumoniae and Mycoplasma genitalium are cell wall-less bacteria with strongly reduced genome content and close phylogenetic relatedness. In humans, the only known natural host, the microorganisms colonize the respiratory or genitourinary mucosa and may cause a broad range of clinical presentations. Besides fundamental differences in their tissue specificity, transmission route, and ability to cause prevalence peaks, both species share similarities such as the occurrence of asymptomatic carriers, preferred populations for infection, and problems with high rates of antimicrobial resistance. To further understand the epidemiology of these practically challenging bacteria, typing of strains is necessary. Since the cultivation of both pathogens is difficult and not performed outside of specialized laboratories, molecular typing methods with adequate discriminatory power, stability, and reproducibility have been developed. These include the characterization of genes containing repetitive sequences, of variable genome regions without the presence of repetitive sequences, determination of single and multi-locus variable-number tandem repeats, and detection of single nucleotide polymorphisms in different genes, respectively. The current repertoire of procedures allows reliable differentiation of strains circulating in different populations and in different time periods as well as comparison of strains occurring subsequently in individual patients. In this review, the methods for typing M. pneumoniae and M. genitalium, including the results of their application in different studies, are summarized and current knowledge regarding the association of typing data with the clinical characteristics of infections is presented.

Ascending Reproductive Tract Infection in Pig-Tailed Macaques Inoculated with Mycoplasma genitalium

Mycoplasma genitalium is a sexually transmitted bacterial pathogen that causes urogenital disease in men and women. M. genitalium infections can persist for months to years and can ascend to the upper reproductive tract in women where it is associated with serious sequelae including pelvic inflammatory disease, tubal factor infertility, and preterm birth. An animal model is needed to understand immune evasion strategies that allow persistence, mechanisms of ascending infection, and factors associated with clearance. In earlier studies, we determined that pig-tailed macaques are susceptible to cervical infection; however, not all primates were successfully infected, persistence varied between animals, and ascension to the upper reproductive tract was not observed after 4 or 8 weeks of follow-up. Building on our previous findings, we refined our inoculation methods to increase infection rates, extended observation to 18 weeks, and comprehensively sampled the upper reproductive tract to detect ascending infection. With these improvements, we established infection in all (3/3) primates inoculated with M. genitalium and demonstrated lower tract persistence for 16 to 18 weeks. Ascension to the upper reproductive tract at endpoint was observed in two out of three primates. All three primates developed serum and local antibodies reacting primarily to the MgpB and MgpC adherence proteins. Elevated genital polymorphonuclear leukocytes (PMNs) and inflammatory cytokines and chemokines, erythema of the ectocervix in one primate, and histologic evidence of vaginitis and endocervicitis in two primates suggest a mild to moderate inflammatory response to infection. This model will be valuable to understand the natural history of M. genitalium infection including mechanisms of persistence, immune evasion, and ascension to the upper reproductive tract.

Functional Characterization of the Cell Division Gene Cluster of the Wall-less Bacterium Mycoplasma genitalium

It is well-established that FtsZ drives peptidoglycan synthesis at the division site in walled bacteria. However, the function and conservation of FtsZ in wall-less prokaryotes such as mycoplasmas are less clear. In the genome-reduced bacterium Mycoplasma genitalium, the cell division gene cluster is limited to four genes: mraZ, mraW, MG_223, and ftsZ. In a previous study, we demonstrated that ftsZ was dispensable for growth of M. genitalium under laboratory culture conditions. Herein, we show that the entire cell division gene cluster of M. genitalium is non-essential for growth in vitro. Our analyses indicate that loss of the mraZ gene alone is more detrimental for growth of M. genitalium than deletion of ftsZ or the entire cell division gene cluster. Transcriptional analysis revealed a marked upregulation of ftsZ in the mraZ mutant. Stable isotope labeling by amino acids in cell culture (SILAC)-based proteomics confirmed the overexpression of FtsZ in MraZ-deprived cells. Of note, we found that ftsZ expression was upregulated in non-adherent cells of M. genitalium, which arise spontaneously at relatively high rates. Single cell analysis using fluorescent markers showed that FtsZ localization varied throughout the cell cycle of M. genitalium in a coordinated manner with the chromosome and the terminal organelle (TMO). In addition, our results indicate a possible role for the RNA methyltransferase MraW in the regulation of FtsZ expression at the post-transcriptional level. Altogether, this study provides an extensive characterization of the cell division gene cluster of M. genitalium and demonstrates the existence of regulatory elements controlling FtsZ expression at the temporal and spatial level in mycoplasmas.

Sequence variation and immunogenicity of the Mycoplasma genitalium MgpB and MgpC adherence proteins during persistent infection of men with non-gonococcal urethritis

Mycoplasma genitalium is a sexually transmitted bacterial pathogen that infects men and women. Antigenic variation of MgpB and MgpC, the immunodominant adherence proteins of M. genitalium, is thought to contribute to immune evasion and chronic infection. We investigated the evolution of mgpB and mgpC sequences in men with non-gonococcal urethritis persistently infected with M. genitalium, including two men with anti-M. genitalium antibodies at enrollment and two that developed antibodies during follow-up. Each of the four patients was persistently infected with a different strain type and each patient produced antibodies targeting MgpB and MgpC. Amino acid sequence evolution in the variable regions of MgpB and MgpC occurred in all four patients with changes observed in single and multiple variable regions over time. Using the available crystal structure of MgpC of the G37 type strain we found that predicted conformational B cell epitopes localize predominantly to the variable region of MgpC, amino acids that changed during patient infection lie in these epitopes, and variant amino acids are in close proximity to the conserved sialic acid binding pocket. These findings support the hypothesis that sequence variation functions to avoid specific antibodies thereby contributing to persistence in the genital tract.

Characterization of an Immunoglobulin Binding Protein (IbpM) From Mycoplasma pneumoniae

Bacteria evolved many ways to invade, colonize and survive in the host tissue. Such complex infection strategies of other bacteria are not present in the cell-wall less Mycoplasmas. Due to their strongly reduced genomes, these bacteria have only a minimal metabolism. Mycoplasma pneumoniae is a pathogenic bacterium using its virulence repertoire very efficiently, infecting the human lung. M. pneumoniae can cause a variety of conditions including fever, inflammation, atypical pneumoniae, and even death. Due to its strongly reduced metabolism, M. pneumoniae is dependent on nutrients from the host and aims to persist as long as possible, resulting in chronic diseases. Mycoplasmas evolved strategies to subvert the host immune system which involve proteins fending off immunoglobulins (Igs). In this study, we investigated the role of MPN400 as the putative factor responsible for Ig-binding and host immune evasion. MPN400 is a cell-surface localized protein which binds strongly to human IgG, IgA, and IgM. We therefore named the protein MPN400 immunoglobulin binding protein of Mycoplasma (IbpM). A strain devoid of IbpM is slightly compromised in cytotoxicity. Taken together, our study indicates that M. pneumoniae uses a refined mechanism for immune evasion.

Subversion of the Immune Response by Human Pathogenic Mycoplasmas

Mycoplasmas are a large group of prokaryotes which is believed to be originated from Gram-positive bacteria via degenerative evolution, and mainly capable of causing a wide range of human and animal infections. Although innate immunity and adaptive immunity play crucial roles in preventing mycoplasma infection, immune response that develops after infection fails to completely eliminate this bacterium under certain circumstances. Thus, it is reasonable to speculate that mycoplasmas employ some mechanisms to deal with coercion of host defense system. In this review, we will highlight and provide a comprehensive overview of immune evasion strategies that have emerged in mycoplasma infection, which can be divided into four aspects: (i) Molecular mimicry and antigenic variation on the surface of the bacteria to evade the immune surveillance; (ii) Overcoming the immune effector molecules assaults: Induction of detoxified enzymes to degradation of reactive oxygen species; Expression of nucleases to degrade the neutrophil extracellular traps to avoid killing by Neutrophil; Capture and cleavage of immunoglobulins to evade humoral immune response; (iii) Persistent survival: Invading into the host cell to escape the immune damage; Formation of a biofilm to establish a persistent infection; (iv) Modulation of the immune system to down-regulate the intensity of immune response. All of these features increase the probability of mycoplasma survival in the host and lead to a persistent, chronic infections. A profound understanding on the mycoplasma to subvert the immune system will help us to better understand why mycoplasma is so difficult to eradicate and ultimately provide new insights on the development of therapeutic regimens against this bacterium in future.