Mutations in a 23S rRNA gene of Chlamydia trachomatis associated with resistance to macrolides

Phenotypic and Genotypic Antimicrobial Susceptibility Testing of Chlamydia trachomatis Isolates from Patients with Persistent or Clinical Treatment Failure in Spain

The aim of this multicentre project (seven hospitals across the Spanish National Health Service) was to study the phenotypic and genotypic susceptibility of C. trachomatis to the main antimicrobials used (macrolides, doxycycline, and quinolones) in isolates from patients with clinical treatment failure in whom reinfection had been ruled out. During 2018-2019, 73 clinical isolates were selected. Sixty-nine clinical specimens were inoculated onto confluent McCoy cell monolayers for phenotypic susceptibility testing. The minimum inhibitory concentration for azithromycin and doxycycline was defined as the lowest concentration associated with an at least 95% reduction in inclusion-forming units after one passage in the presence of the antibiotic compared to the initial inoculum for each strain (control). Sequencing analysis was performed for the genotypic detection of resistance to macrolides, analysing mutations in the 23S rRNA gene (at positions 2057, 2058, 2059, and 2611), and quinolones, analysing a fragment of the gyrA gene, and searching for the G248T mutation (Ser83->Ile). For tetracyclines, in-house RT-PCR was used to test for the tet(C) gene. The phenotypic susceptibility testing was successful for 10 isolates. All the isolates had minimum inhibitory concentrations for azithromycin ≤ 0.125 mg/L and for doxycycline ≤ 0.064 mg/L and were considered sensitive. Of the 73 strains studied, no mutations were found at positions T2611C or G248T of the gyrA gene. We successfully sequenced 66 isolates. No macrolide resistance-associated mutations were found at positions 2057, 2058, 2059, or T2611C. None of the isolates carried the tet(C) gene. We found no evidence for genomic resistance in this large, clinically relevant dataset.

Chlamydia trachomatis-An Emerging Old Entity?

Chlamydia trachomatis is an evasive pathogen that can prompt severe clinical manifestations in humans such as vaginitis, epididymitis, lymphogranuloma venereum, trachoma, conjunctivitis and pneumonia. If left untreated, chronic infections with C. trachomatis can give rise to long-lasting and even permanent sequelae. To shed some light on its widespread nature, data from original research, systematic reviews and meta-analyses from three databases was collected and analyzed in the context of chlamydial infection, related symptoms and appropriate treatment modalities. This review describes the bacterium's pervasiveness on a global scale, especially in developing countries, and suggests ways to halt its transmission and spread. Infections with C. trachomatis often go unnoticed, as many individuals are asymptomatic and unaware of their diagnosis, contributing to a delay in diagnosis and treatment. The high prevalence of chlamydial infection highlights the need for a universal screening and detection method enabling immediate treatment at its onset. Prognosis is favorable with antibiotic therapy and education for high-risk groups and their sexual partners. In the future, a quick, easily accessible, and inexpensive test should be developed to diagnose and treat infected individuals early on. Along with a vaccine against C. trachomatis, it would halt the transmission and spread of the pathogen worldwide.

Identification and characterization of mixed infections of Chlamydia trachomatis via high-throughput sequencing

Precise genotyping is necessary to understand epidemiology and clinical manifestations of Chlamydia trachomatis infection with different genotypes. Next-generation high-throughput sequencing (NGHTS) has opened new frontiers in microbial genotyping, but has been clinically characterized in only a few settings. This study aimed to determine C. trachomatis genotypes in particular mixed-genotype infections and their association with clinical manifestations and to characterize the sensitivity and accuracy of NGHTS. Cervical specimens were collected from 8,087 subjects from physical examination center (PEC), assisted reproductive technology center (ART) and gynecology clinics (GC) of Chenzhou Hospital of China. The overall prevalence of C. trachomatis was 3.8% (311/8087) whereas a prevalence of 2.8, 3.7 and 4.8% was found in PEC, ART and GC, respectively. The most frequent three C. trachomatis genotypes were E (27.4%, 83/303), F (21.5%, 65/303) and J (18.2%, 55/303). Moreover, NGHTS identified 20 (6.6%, 20/303) mixed-genotype infections of C. trachomatis. Genotype G was more often observed in the subjects with pelvic inflammatory disease than genotype E (adjusted OR = 3.61, 95%CI, 1.02-12.8, p = 0.046). Mixed-genotype infection was associated with severe vaginal cleanliness (degree IV) with an adjusted OR of 5.17 (95%CI 1.03-25.9, p = 0.046) whereas mixed-genotype infection with large proportion of minor genotypes was associated with cervical squamous intraepithelial lesion (SIL) with an adjusted OR of 5.51 (95%CI 1.17-26.01, p = 0.031). Our results indicated that NGHTS is a feasible tool to identity C. trachomatis mixed-genotype infections, which may be associated with worse vaginal cleanliness and cervical SIL.

Rhein inhibits Chlamydia trachomatis infection by regulating pathogen-host cell

The global incidence of genital Chlamydia trachomatis infection increased rapidly as the primary available treatment of C. trachomatis infection being the use of antibiotics. However, the development of antibiotics resistant stain and other treatment failures are often observed in patients. Consequently, novel therapeutics are urgently required. Rhein is a monomer derivative of anthraquinone compounds with an anti-infection activity. This study investigated the effects of rhein on treating C. trachomatis infection. Rhein showed significant inhibitory effects on the growth of C. trachomatis in multiple serovars of C. trachomatis, including D, E, F and L1, and in various host cells, including HeLa, McCoy and Vero. Rhein could not directly inactivate C. trachomatis but could inhibit the growth of C. trachomatis by regulating pathogen-host cell interactions. Combined with azithromycin, the inhibitory effect of rehin was synergistic both in vitro and in vivo. Together these findings suggest that rhein could be developed for the treatment of C. trachomatis infections.

Evaluation of Ureaplasma urealyticum, Chlamydia trachomatis, Mycoplasma genitalium and Neisseria gonorrhoeae in infertile women compared to pregnant women

Infertility is one of the major health problems of patients suffering from bacterial infections. Given the high percentage of infertility, the aim of this study was to investigate the prevalence of Chlamydia trachomatis, Mycoplasma genitalium, Neisseria gonorrhoeae and Ureaplasma urealyticum in fertile and infertile women. In the prospective study, 65 infertile patients and 54 pregnant women referred to Mahdieh Hospital in Tehran were included. After transferring of vaginal swabs to the laboratory, DNA extraction and Polymerase Chain Reaction (PCR) were performed using specific primers. Of the 65 vaginal swab specimens, the prevalence of U. urealyticum, M. genitalium, C. trachomatis and N. gonorrhoeae were as 15 (23.1%), 11 (16.9%), 9 (13.8%) and 4 (6.2%), respectively; However, these rate in fertile group was as 6 (11.1%), 3 (5.5%), 5 (9.2%) and 1 (1.8%), respectively. Bacterial infections were higher in infertile group; therefore, these bacterial agents may be associated with female infertility. Timely control and treatment of infections caused by these organisms, together with other factors, can be important in prevention and treatment of the women's infertility and thereby community health.Impact StatementWhat is already known on this subject? Infertility is one of the most common reproductive health issues in Iran. Female reproductive system is a suitable environment for the growth of many pathogens, which may disrupt any stage of foetal formation, implantation or growth. Chlamydia trachomatis, Neisseria gonorrhoeae, Mycoplasma genitalium and Ureaplasma urealyticum are the most important microorganisms that have been considered in the infertility.What do the results of this study add? The prevalence of C. trachomatis, M. genitalium, N. gonorrhoeae, M. genitalium and U. urealyticum were higher in infertile women, but there was no statistically significant compared to pregnant women. These results suggest that timely control and treatment of infections caused by these organisms, along with other factors, can be used to prevent and treat women infertility and community health.What are the implications of these findings for clinical practice and/or further research? Based on the results, designing and implementing national control programs to prevent subsequent complications is thought to be necessary. Comprehensive analyses of the overall prevalence of these bacteria, particularly in developing countries (including Iran), may help to carry out such a strategy.

Direct assessment of possible mutations in the 23S rRNA gene encoding macrolide resistance in Chlamydia trachomatis

Reports of potential treatment failure have raised particular concerns regarding the efficacy of the single dose azithromycin regimen in the treatment of urogenital and anorectal Chlamydia trachomatis (CT) infections. Several factors have been suggested, including heterotypic resistance. Antimicrobial susceptibility testing in CT requires cell culture with serial dilutions of antibiotics, which is laborious and for which there is no standardized testing methodology. One method to partly overcome these difficulties would be to use a genotypic resistance assay, however most current available assays do still require prior CT culture. In order to facilitate the assessment of genotypic resistance directly from clinical samples, without the need for prior culture, the aim of this study was to develop a CT specific PCR assay for the assessment of resistance associated mutations (RAMs) in the 23S rRNA gene, and to evaluate a sample of clinical cases in which CT PCR’s remained positive during follow-up despite azithromycin treatment. Neither the in silico analysis nor the analytical specificity testing demonstrated clinically relevant cross-reactivity with other bacterial species. These results in conjunction with the analytical sensitivity demonstrating consistent CT 23S rRNA gene detection in the range of 10e3 IFU/mL, exemplify the assay’s apt performance. Although no known macrolide RAMs were detected in the clinical cases, the described assay allows future culture independent macrolide RAM surveillance in CT, and increases accessibility for other laboratories to engage in screening.

Mechanism of action, resistance, synergism, and clinical implications of azithromycin

Background

Azithromycin (AZM), sold under the name Zithromax, is classified as a macrolide. It has many benefits due to its immunomodulatory, anti‐inflammatory, and antibacterial effects. This review aims to study different clinical and biochemisterial aspects and properties of this drug which has a priority based on literature published worldwide.

Methods

Several databases including Web of Science, Google Scholar, PubMed, and Scopus were searched to obtain the relevant studies.

Results

AZM mechanism of action including the inhibition of bacterial protein synthesis, inhibition of proinflammatory cytokine production, inhibition of neutrophil infestation, and macrophage polarization alteration, gives it the ability to act against a wide range of microorganisms. Resistant organisms are spreading and being developed because of the irrational use of the drug in the case of dose and duration. AZM shows synergistic effects with other drugs against a variety of organisms. This macrolide is considered a valuable antimicrobial agent because of its use as a treatment for a vast range of diseases such as asthma, bronchiolitis, COPD, cystic fibrosis, enteric infections, STIs, and periodontal infections.

Conclusions

Our study shows an increasing global prevalence of AZM resistance. Thus, synergistic combinations are recommended to treat different pathogens. Moreover, continuous monitoring of AZM resistance by registry centers and the development of more rapid diagnostic assays are urgently needed.

Whole-genome sequencing of Chlamydia trachomatis isolates from persistently infected patients

BACKGROUND

Current understanding of the causes of treatment failure in Chlamydia trachomatis is poor and antimicrobial susceptibility data are lacking. We used genome sequencing to seek evidence of antimicrobial resistance in isolates sourced from patients who were persistently infected.

METHODS

Genomic DNA was extracted from C. trachomatis isolates cultured in McCoy cell monolayers. Sequencing libraries were prepared using the SureSelect^XT Illumina paired-end protocol. Paired reads were mapped against a reference genome and single nucleotide variants (SNVs) were identified.

RESULTS

Seven isolates from persistently infected patients and five isolates from successfully treated patients were sequenced. No previously reported SNVs associated with antimicrobial resistance were found. A unique SNV was identified in the gyrA gene of one treatment failure isolate but was located outside of the quinolone resistance determining region; this SNV has been previously reported in other members of the Chlamydiaceae family.

CONCLUSION

No genomic evidence was found to explain the differences in clinical outcome for our two groups of patients. A mutation unrelated to antimicrobial susceptibility was found in an isolate from a persistently infected patient. The cause of these persistent infections with C. trachomatis remains unclear.

An overview of genes and mutations associated with Chlamydiae species' resistance to antibiotics

Background

Chlamydiae are intracellular bacteria that cause various severe diseases in humans and animals. The common treatment for chlamydia infections are antibiotics. However, when antibiotics are misused (overuse or self-medication), this may lead to resistance of a number of chlamydia species, causing a real public health problem worldwide.

Materials and methods

In the present work, a comprehensive literature search was conducted in the following databases: PubMed, Google Scholar, Cochrane Library, Science direct and Web of Science. The primary purpose is to analyse a set of data describing the genes and mutations involved in Chlamydiae resistance to antibiotic mechanisms. In addition, we proceeded to a filtration process among 704 retrieved articles, then finished by focusing on 24 studies to extract data that met our requirements.

Results

The present study revealed that Chlamydia trachomatis may develop resistance to macrolides via mutations in the 23S rRNA, rplD, rplV genes, to rifamycins via mutations in the rpoB gene, to fluoroquinolones via mutations in the gyrA, parC and ygeD genes, to tetracyclines via mutations in the rpoB gene, to fosfomycin via mutations in the murA gene, to MDQA via mutations in the secY gene. Whereas, Chlamydia pneumoniae may develop resistance to rifamycins via mutations in the rpoB gene, to fluoroquinolones via mutations in the gyrA gene. Furthermore, the extracted data revealed that Chlamydia psittaci may develop resistance to aminoglycosides via mutations in the 16S rRNA and rpoB genes, to macrolides via mutations in the 23S rRNA gene. Moreover, Chlamydia suis can become resistance to tetracyclines via mutations in the tet(C) gene. In addition, Chlamydia caviae may develop resistance to macrolides via variations in the 23S rRNA gene. The associated mechanisms of resistance are generally: the inhibition of bacteria’s protein synthesis, the inhibition of bacterial enzymes’ action and the inhibition of bacterial transcription process.

Conclusion

This literature review revealed the existence of diverse mutations associated with resistance to antibiotics using molecular tools and targeting chlamydia species’ genes. Furthermore, these mutations were shown to be associated with different mechanisms that led to resistance. In that regards, more mutations and information can be shown by a deep investigation using the whole genome sequencing. Certainly, this can help improving to handle chlamydia infections and healthcare improvement by decreasing diseases complications and medical costs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12941-021-00465-4.

Chlamydial clinical isolates show subtle differences in persistence phenotypes and growth in vitro

Urogenital Chlamydia trachomatis infection is the most common sexually transmitted bacterial infection throughout the world. While progress has been made to better understand how type strains develop and respond to environmental stress in vitro, very few studies have examined how clinical isolates behave under similar conditions. Here, we examined the development and persistence phenotypes of several clinical isolates, to determine how similar they are to each other, and the type strain C. trachomatis D/UW-3/Cx. The type strain was shown to produce infectious progeny at a higher magnitude than each of the clinical isolates, in each of the six tested cell lines. All chlamydial strains produced the highest number of infectious progeny at 44 h post-infection in the McCoy B murine fibroblast cell line, yet showed higher levels of infectivity in the MCF-7 human epithelial cell line. The clinical isolates were shown to be more susceptible than the type strain to the effects of penicillin and iron deprivation persistence models in the MCF-7 cell line. While subtle differences between clinical isolates were observed throughout the experiments conducted, no significant differences were identified. This study reinforces the importance of examining clinical isolates when trying to relate in vitro data to clinical outcomes, as well as the importance of considering the adaptations many type strains have to being cultured in vitro.

High treatment failure rate is better explained by resistance gene detection than by minimum inhibitory concentration in patients with urogenital Chlamydia trachomatis infection

OBJECTIVE

The aim of this study was to investigate the relationships between treatment outcomes of patients with urogenital Chlamydia trachomatis infections and minimum inhibitory concentrations (MICs) and drug resistance genes.

METHODS

The clinical data of 92 patients diagnosed with Chlamydia trachomatis (C. trachomatis) infections were collected. Of these patients, 28 received regular treatment with azithromycin and 64 received minocycline. All patients underwent three monthly follow-ups after the completion of treatment. The microdilution method was used for the in vitro susceptibility tests. The acquisition of 23S rRNA mutations and presence of the tet(M) gene were detected by gene amplification and sequencing.

RESULTS

The MICs of azithromycin, clarithromycin, erythromycin, tetracycline, doxycycline, and minocycline were comparable for isolates from the treatment failure and treatment success groups. Higher detection rates of 23S rRNA gene mutations and tet(M) were found in the treatment failure group (57.14% and 71.43%, respectively) than in the treatment success group (14.29% and 30.23%, respectively) (p < 0.05). The A2057G, C2452A, and T2611C gene mutations of 23S rRNA were detected in eight clinical isolates from the azithromycin treatment failure group, while the T2611C gene mutation was detected in one clinical strain from the treatment success group.

CONCLUSIONS

The detection of resistance genes could better explain the high treatment failure rate than the MIC results in patients with urogenital C. trachomatis infections, highlighting the need for genetic antimicrobial resistance testing in infected patients.

Antimicrobial resistance in sexually transmitted infections

RATIONALE FOR REVIEW

International travel facilitates the spread of drug-resistant infections, including sexually transmitted infections (STIs). In 2016, the World Health Organization highlighted the global burden of 'curable' STIs, estimating 376 million new infections of gonorrhoea, chlamydia, syphilis and trichomoniasis annually, with considerable geographic variation in both the burden of disease and prevalence of resistance. Travelers' risk of contracting and transmitting drug-resistant STIs depends in part on their geographic exposure. In this review, we describe the epidemiology of antimicrobial resistance (AMR) and the management of these four common STIs and Mycoplasma genitalium, an increasingly recognized cause of non-gonococcal urethritis.

KEY FINDINGS

Multi-drug and extensively drug resistant gonorrhoea strains have been associated with international spread, particularly in travelers returning from Southeast Asia. Chlamydia is the most common bacterial STI worldwide. Although in vitro resistance has been reported, surveillance data suggest that clinically significant resistance to macrolides and tetracyclines is rare. Macrolide resistance in syphilis is now endemic in much of the world but there is no documented penicillin resistance, which remains first-line therapy. Trichomoniasis is the most common non-viral STI worldwide. Although clinical failure after treatment occurs, resistance to metronidazole is thought to be uncommon. Mycoplasma genitalium exhibits intrinsic resistance to many antibiotics, and the prevalence of resistance to both first- and second-line regimens (macrolides and fluoroquinolones) is increasing worldwide, with limited alternative therapeutic options.

RECOMMENDATIONS

International travelers are at risk for acquiring resistant STIs with limited therapeutic options. Improved diagnostics are urgently needed to improve AMR surveillance and the management of infected patients. As no vaccinations are currently available for these STIs, and pre-exposure prophylaxis is an area of active study with limited data, condom use is critical for prevention. Travel medicine providers should incorporate STI risk reduction counselling, with an emphasis on condom use, into the routine pre-travel consultation.

Phenotypic antimicrobial susceptibility testing of Chlamydia trachomatis isolates from patients with persistent or successfully treated infections

Objectives

Antimicrobial susceptibility data for Chlamydia trachomatis are lacking. Methodologies for susceptibility testing in C. trachomatis are not well-defined, standardized or performed routinely owing to its intracellular growth requirements. We sought to develop an assay for the in vitro susceptibility testing of C. trachomatis isolates from two patient cohorts with different clinical outcomes.

Methods

Twenty-four clinical isolates (11 from persistently infected and 13 from successfully treated patients) were overlaid with media containing two-fold serial dilutions of azithromycin or doxycycline. After incubation, aliquots were removed from the stock inoculum (SI) and each antimicrobial concentration for total RNA extraction, complementary DNA generation and real-time PCR. The MIC was defined as the lowest antimicrobial concentration where a 95% reduction in transcription was evident in comparison with the SI for each isolate.

Results

MICs of azithromycin were comparable for isolates from the two patient groups (82% ≤ 0.25 mg/L for persistently infected and 100% ≤ 0.25 mg/L for successfully treated patients). Doxycycline MICs were at least two-fold lower for isolates from the successfully treated patients (53.9% ≤ 0.064 mg/L) than for the persistently infected patients (100% ≥ 0.125 mg/L) (P = 0.006, Fisher's exact test). Overall, 96% of isolates gave reproducible MICs when re-tested.

Conclusions

A reproducible assay was developed for antimicrobial susceptibility testing of C. trachomatis. MICs of azithromycin were generally comparable for the two different patient groups. MICs of doxycycline were significantly higher in the persistently infected patients. However, interpretation of elevated MICs in C. trachomatis is extremely challenging in the absence of breakpoints, or wild-type and treatment failure MIC distribution data.

Infections caused by Chlamydia trachomatis (including lymphogranuloma venereum) and Mycoplasma genitalium

Sexually transmitted infections caused by Chlamydia trachomatis, including lymphogranuloma venereum and Mycoplasma genitalium have increased in last decade. This epidemiological scenario presents new challenges in order to improve and strengthen our control and prevention strategies. The routine clinical diagnosis of urethritis and cervicitis must be combined with the active search for the causal agent in men with symptoms of dysuria or proctitis, and in women with pelvic inflammatory disease. We should also include sexually transmitted infections screening in asymptomatic patients with sexual risk behaviours or sexual contact with patients diagnosed with an sexually transmitted infection. The microbiological diagnosis must be based on molecular techniques capable of detecting Chlamydia trachomatis (discriminating between L genotypes associated with lymphogranuloma venereum and other genotypes) and Mycoplasma genitalium (ideally including the identification of macrolide-resistant strains). A faster and specific diagnosis will allow for a targeted treatment with a suitable antibiotic regimen. We also recommend including contact tracing of sexual partners and, occasionally, a cure test. Finally, sexually transmitted infection screening must be widely implemented in those population groups with a high prevalence of sexually transmitted infections.

An in vitro model of azithromycin-induced persistent Chlamydia trachomatis infection

Single-dose azithromycin is recommended for treating Chlamydia trachomatis infections. Here, we established an in vitro cell model of azithromycin-induced persistent infection. Azithromycin inhibited the replication of C. trachomatis in a dose-time-dependent manner. Electron microscopy indicated that small inclusions in the induced model contained enlarged, aberrant and non-infectious reticulate bodies. RT-PCR showed that C. trachomatis still has the ability to express the unprocessed 16S rRNA gene in the model and that C. trachomatis recovered after the removal of azithromycin with a peak recovery time of 24 h. The mutations in 23S rRNA, L4 and L22 genes were not found in persistent infection, and qRT-PCR analysis showed that the relative expression level of euo in azithromycin treated infection was upregulated while omcB was downregulated. In summary, this study provides a novel in vitro cell model to examine the characteristics of azithromycin-induced persistent infection and contribute to the development of treatments for C. trachomatis infection.

Macrolide and fluoroquinolone resistance is uncommon in clinical strains of Chlamydia trachomatis

We analyzed the 23S rRNA, gyrA and parC genes of Chlamydia trachomatis DNAs from men with urethritis and determined microbiological outcomes of an extended-release azithromycin (azithromycin-SR) regimen (2 g once daily for 1 day) and a sitafloxacin regimen (100 mg twice daily for 7 days) for chlamydial urethritis to clarify the macrolide and fluoroquinolone resistance status of clinical strains of C. trachomatis. We amplified the portions of 2 alleles of the 23S rRNA gene and the gyrA and parC genes from C. trachomatis DNAs in 284 first-voided urine specimens from men with chlamydial urethritis by PCR and sequenced their PCR products. We enrolled 369 men with chlamydial urethritis, comprising 314 and 55 treated with the azithromycin-SR regimen and the sitafloxacin regimen, respectively. Alleles 1 and/or 2 of the 23S rRNA gene were analyzed in 162 specimens. No mutations were found in the sequenced regions, including the central portion of domain V. The gyrA and parC genes were analyzed in 118 and 113 specimens, respectively. No amino acid changes were found within the quinolone resistance-determining region of the gyrA gene and in the sequenced region of the parC gene. The microbiological outcomes of the azithromycin-SR and sitafloxacin regimens were assessed in 176 and 30 men, respectively. The eradication rates were 96.0% (95% CI 93.1%-98.9%) for the azithromycin-SR regimen and 100% for the sitafloxacin regimen. Clinical strains of C. trachomatis with macrolide and/or fluoroquinolone resistance would be uncommon, and azithromycin or fluoroquinolone regimens could be recommended as treatments for chlamydial infections.

The macrolide antibiotic renaissance

Macrolides represent a large family of protein synthesis inhibitors of great clinical interest due to their applicability to human medicine. Macrolides are composed of a macrocyclic lactone of different ring sizes, to which one or more deoxy-sugar or amino sugar residues are attached. Macrolides act as antibiotics by binding to bacterial 50S ribosomal subunit and interfering with protein synthesis. The high affinity of macrolides for bacterial ribosomes, together with the highly conserved structure of ribosomes across virtually all of the bacterial species, is consistent with their broad-spectrum activity. Since the discovery of the progenitor macrolide, erythromycin, in 1950, many derivatives have been synthesised, leading to compounds with better bioavailability and acid stability and improved pharmacokinetics. These efforts led to the second generation of macrolides, including well-known members such as azithromycin and clarithromycin. Subsequently, in order to address increasing antibiotic resistance, a third generation of macrolides displaying improved activity against many macrolide resistant strains was developed. However, these improvements were accompanied with serious side effects, leading to disappointment and causing many researchers to stop working on macrolide derivatives, assuming that this procedure had reached the end. In contrast, a recent published breakthrough introduced a new chemical platform for synthesis and discovery of a wide range of diverse macrolide antibiotics. This chemical synthesis revolution, in combination with reduction in the side effects, namely, 'Ketek effects', has led to a macrolide renaissance, increasing the hope for novel and safe therapeutic agents to combat serious human infectious diseases.

Comprehensive global genome dynamics of Chlamydia trachomatis show ancient diversification followed by contemporary mixing and recent lineage expansion

Chlamydia trachomatis is the world's most prevalent bacterial sexually transmitted infection and leading infectious cause of blindness, yet it is one of the least understood human pathogens, in part due to the difficulties of in vitro culturing and the lack of available tools for genetic manipulation. Genome sequencing has reinvigorated this field, shedding light on the contemporary history of this pathogen. Here, we analyze 563 full genomes, 455 of which are novel, to show that the history of the species comprises two phases, and conclude that the currently circulating lineages are the result of evolution in different genomic ecotypes. Temporal analysis indicates these lineages have recently expanded in the space of thousands of years, rather than the millions of years as previously thought, a finding that dramatically changes our understanding of this pathogen's history. Finally, at a time when almost every pathogen is becoming increasingly resistant to antimicrobials, we show that there is no evidence of circulating genomic resistance in C. trachomatis.

Measurement of tissue azithromycin levels in self-collected vaginal swabs post treatment using liquid chromatography and tandem mass spectrometry (LC-MS/MS)

BACKGROUND

Azithromycin is recommended for the treatment of uncomplicated urogenital chlamydia infection although the standard 1gram dose sometimes fails to eradicate the infection (treatment failure). One hypothesis proposed for treatment failure has been insufficient levels of the antibiotic at the site of infection. We developed an assay using liquid chromatography and tandem mass spectrometry (LC-MS/MS) to measure azithromycin concentration in high-vaginal swabs and monitor how concentration changes over time following routine azithromycin treatment.

METHODS

Azithromycin concentrations were measured in two groups of women either within the first 24h of taking a 1g dose (N = 11) or over 9 days (N = 10). Azithromycin concentrations were normalised to an internal standard (leucine enkephalin), and the bulk lipid species phosphatidylcholine [PC(34:1)], using an Agilent 6490 triple quadrupole instrument in positive ionisation mode. The abundances of azithromycin, PC(34:1), and leu-enkephalin were determined by multiple reaction monitoring and absolute levels of azithromycin estimated using standard curves prepared on vaginal specimens.

RESULTS

Vaginal azithromycin concentrations of women were rapidly obtained after 5h post-treatment (mean concentration = 1031mcg/mg of lipid, range = 173-2693mcg/mg). In women followed for 9 days, peak concentrations were highest after day 2 (mean concentration = 2206mcg/mg, range = 721-5791mcg/mg), and remained high for at least 9 days with a mean concentration of 384mcg/mg (range = 139-1024mcg/mg) on day 9.

CONCLUSION

Our study confirmed that a single 1g dose of azithromycin is rapidly absorbed and remains in the vagina at relatively high levels for at least a week, suggesting that poor antibiotic absorption is unlikely to be an explanation for treatment failure.

Antimicrobial susceptibilities of Chlamydia trachomatis isolated from the urethra and pharynx of Japanese males

OBJECTIVES

Sexually transmitted infections due to Chlamydia trachomatis (C. trachomatis) are a worldwide public health problem. The aim of this study was to investigate the drug susceptibilities of C. trachomatis strains isolated from the urethra and pharynx of Japanese males.

METHODS

Urethral and pharyngeal swabs were collected between 2013 and 2014 from Japanese males with urethritis. Using a McCoy cell line, 18 chlamydial strains were isolated from urethra in 18 patients and 7 from the pharynx in 7 of the 18 patients. The minimum inhibitory concentrations (MICs) of levofloxacin (LVFX) and azithromycin (AZM) were measured using the standard method of the Japanese Society of Chemotherapy.

RESULTS

The MICs of LVFX and AZM against urethral chlamydial strains were 0.125-0.5 μg/mL and 0.125-0.25 μg/mL, respectively. In pharyngeal strains, the MICs of LVFX and AZM were 0.125-0.25 μg/mL and 0.125-0.25 μg/mL, respectively. In 7 patients with chlamydial strains isolated from both the urethra and pharynx, the MICs of LVFX between these strains were identical in 3 of 6 patients (no growth was observed for one pharyngeal strain), while the MICs of AZM between these strains were identical in all 6 patients (not performed for one patient).

CONCLUSIONS

Our data suggest that C. trachomatis strains isolated from the urethra and pharynx of Japanese males are susceptible to LVFX and AZM. Although measuring the MICs of chlamydial strains is labor intensive, it is a significant surveillance tool for treating chlamydial infections and preventing the spread of STIs.

Resistance to Macrolide Antibiotics in Public Health Pathogens

Macrolide resistance mechanisms can be target-based with a change in a 23S ribosomal RNA (rRNA) residue or a mutation in ribosomal protein L4 or L22 affecting the ribosome's interaction with the antibiotic. Alternatively, mono- or dimethylation of A2058 in domain V of the 23S rRNA by an acquired rRNA methyltransferase, the product of an erm (erythromycin ribosome methylation) gene, can interfere with antibiotic binding. Acquired genes encoding efflux pumps, most predominantly mef(A) + msr(D) in pneumococci/streptococci and msr(A/B) in staphylococci, also mediate resistance. Drug-inactivating mechanisms include phosphorylation of the 2'-hydroxyl of the amino sugar found at position C5 by phosphotransferases and hydrolysis of the macrocyclic lactone by esterases. These acquired genes are regulated by either translation or transcription attenuation, largely because cells are less fit when these genes, especially the rRNA methyltransferases, are highly induced or constitutively expressed. The induction of gene expression is cleverly tied to the mechanism of action of macrolides, relying on antibiotic-bound ribosomes stalled at specific sequences of nascent polypeptides to promote transcription or translation of downstream sequences.

Nationwide surveillance of the antimicrobial susceptibility of Chlamydia trachomatis from male urethritis in Japan

Genital chlamydial infection is a principal sexually transmitted infection worldwide. Chlamydia trachomatis can cause male urethritis, acute epididymitis, cervicitis, and pelvic inflammatory disease as sexually transmitted infections. Fortunately, homotypic resistant C. trachomatis strains have not been isolated to date; however, several studies have reported the isolation of heterotypic resistant strains from patients. In this surveillance study, clinical urethral discharge specimens were collected from patients with urethritis in 51 hospitals and clinics in 2009 and 38 in 2012. Based on serial cultures, the minimum inhibitory concentration (MIC) could be determined for 19 isolates in 2009 and 39 in 2012. In 2009 and 2012, the MICs (MIC90) of ciprofloxacin, levofloxacin, tosufloxacin, sitafloxacin, doxycycline, minocycline, erythromycin, clarithromycin, and azithromycin were 2 μg/ml and 1 μg/ml, 0.5 μg/ml and 0.5 μg/ml, 0.125 μg/ml and 0.125 μg/ml, 0.063 μg/ml and 0.063 μg/ml, 0.125 μg/ml and 0.125 μg/ml, 0.125 μg/ml and 0.125 μg/ml, 0.016 μg/ml and 0.016 μg/ml, and 0.063 μg/ml and 0.063 μg/ml, respectively. In summary, this surveillance project did not identify any resistant strain against fluoroquinolone, tetracycline, or macrolide agents in Japan.

Comparison of doxycycline with azithromycin in treatment of pharyngeal chlamydia infection

Recent data suggest that azithromycin may not be as effective as doxycycline in eradication of genital chlamydial infection. The aim of this study was to compare the eradication rate of pharyngeal Chlamydia trachomatis infection after treatment with azithromycin 1 g stat with that of doxycycline 100 mg twice a day for seven days. A prospective open-label observational study was conducted on patients with pharyngeal Chlamydia trachomatis diagnosed at Whittall Street Clinic, University Hospitals Birmingham, Birmingham, UK, between July 2012 and July 2013. We confirmed eradication of pharyngeal Chlamydia trachomatis with a negative test of cure. We treated all our patients with azithromycin 1 g stat until February 2013. At that stage, we offered doxycycline to patients with pharyngeal Chlamydia trachomatis A total of 398 patients (52 men, 346 women) were diagnosed with pharyngeal Chlamydia trachomatis during the study period. Of the 172 patients included in the final analysis, 78 were treated with azithromycin and 64 with doxycycline. Treatment failure was identified among 8/78 (10%) patients treated with azithromycin and 1/64 (2%) treated with doxycycline (absolute difference: 8 percentage points, 95% CI: 0-17%, p = 0.041). In our study, doxycycline 100 mg twice a day for seven days was associated with less treatment failure of oropharyngeal chlamydia compared with azithromycin 1 g stat Future randomised studies should investigate whether patients with pharyngeal Chlamydia trachomatis should be followed up with a test of cure when treated with azithromycin, or be treated with doxycycline.

Treatment challenges for urogenital and anorectal Chlamydia trachomatis

While true antimicrobial resistance to Chlamydia trachomatis is a rare occurrence, repeat chlamydia infections continue to be reported following treatment with a single 1 g dose of azithromycin or week long doxycycline - with considerable more concern about azithromycin treatment failure. While most repeat positive cases are likely to be reinfections, emerging evidence indicates treatment failure may play a role. Current data suggests that there may are differences in the efficacy of the drugs between rectal and non-rectal sites of infection and factors such as immune response, drug pharmacokinetics, organism load, auto-inoculation from rectum to cervix in women and the genital microbiome may play a role in treatment failure. Other possible reasons for repeat infection include the low discriminatory power of NAAT tests to differentiate between viable and nonviable organisms and failure to detect LGV infection. This review will present the current evidence regarding the management challenges for urogenital and anorectal chlamydia infections and provide some suggestions for where future research efforts are needed to address important knowledge gaps in this area and provide stronger evidence for the development of robust treatment guidelines.

Differences in 23S ribosomal RNA mutations between wild-type and mutant macrolide-resistant Chlamydia trachomatis isolates

The aim of the present study was to determine the in vitro susceptibility of wild-type and mutant clinical isolates of Chlamydia (C.) trachomatis strains to erythromycin, azithromycin and josamycin, and to identify the resistance-conferring 23S ribosomal (r)RNA mutations in the isolates. The wild-type resistant isolates were defined as those with minimum inhibitory concentration values above the tissue concentration of the antibiotic in the urogenital system. Furthermore, all resistant C. trachomatis isolates were exposed to sub-inhibitory concentrations of macrolides, and 13 resistant mutants were selected following serial passages. Among the 8 wild-type isolates that were resistant to erythromycin, 3 isolates had a mutation at T2611C in the 23S rRNA gene while the others did not show any 23S rRNA mutations. The selected mutant isolates showed a 4- to 16-fold reduction in in vitro sensitivities. With regard to the mutant strains, the T2611C mutation was found in 10 isolates, A2057G mutation in 6 isolates, and A2059G mutation in 1 isolate. Thus, the macrolide-resistant isolates of the wild-type strain had different mutations from those selected by exposure to sub-inhibitory concentrations of macrolides. Also, since 23S rRNA mutations were not identified in certain isolates, it was considered that other molecular mechanisms may also be responsible for the macrolide resistance of C. trachomatis.

Effects of Mentha suaveolens essential oil on Chlamydia trachomatis

Chlamydia trachomatis, the most common cause of sexually transmitted bacterial infection worldwide, has a unique biphasic developmental cycle alternating between the infectious elementary body and the replicative reticulate body. C. trachomatis is responsible for severe reproductive complications including pelvic inflammatory disease, ectopic pregnancy, and obstructive infertility. The aim of our study was to evaluate whether Mentha suaveolens essential oil (EOMS) can be considered as a promising candidate for preventing C. trachomatis infection. Specifically, we investigated the in vitro effects of EOMS towards C. trachomatis analysing the different phases of chlamydial developmental cycle. Our results demonstrated that EOMS was effective towards C. trachomatis, whereby it not only inactivated infectious elementary bodies but also inhibited chlamydial replication. Our study also revealed the effectiveness of EOMS, in combination with erythromycin, towards C. trachomatis with a substantial reduction in the minimum effect dose of antibiotic. In conclusion, EOMS treatment may represent a preventative strategy since it may reduce C. trachomatis transmission in the population and, thereby, reduce the number of new chlamydial infections and risk of developing of severe sequelae.

Whole-genome enrichment and sequencing of Chlamydia trachomatis directly from clinical samples

Background

Chlamydia trachomatis is a pathogen of worldwide importance, causing more than 100 million cases of sexually transmitted infections annually. Whole-genome sequencing is a powerful high resolution tool that can be used to generate accurate data on bacterial population structure, phylogeography and mutations associated with antimicrobial resistance. The objective of this study was to perform whole-genome enrichment and sequencing of C. trachomatis directly from clinical samples.

Methods

C. trachomatis positive samples comprising seven vaginal swabs and three urine samples were sequenced without prior in vitro culture in addition to nine cultured C. trachomatis samples, representing different serovars. A custom capture RNA bait set, that captures all known diversity amongst C. trachomatis genomes, was used in a whole-genome enrichment step during library preparation to enrich for C. trachomatis DNA. All samples were sequenced on the MiSeq platform.

Results

Full length C. trachomatis genomes (>95-100% coverage of a reference genome) were successfully generated for eight of ten clinical samples and for all cultured samples. The proportion of reads mapping to C. trachomatis and the mean read depth across each genome were strongly linked to the number of bacterial copies within the original sample. Phylogenetic analysis confirmed the known population structure and the data showed potential for identification of minority variants and mutations associated with antimicrobial resistance. The sensitivity of the method was >10-fold higher than other reported methodologies.

Conclusions

The combination of whole-genome enrichment and deep sequencing has proven to be a non-mutagenic approach, capturing all known variation found within C. trachomatis genomes. The method is a consistent and sensitive tool that enables rapid whole-genome sequencing of C. trachomatis directly from clinical samples and has the potential to be adapted to other pathogens with a similar clonal nature.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-014-0591-3) contains supplementary material, which is available to authorized users.

Increased carriage of macrolide-resistant fecal E. coli following mass distribution of azithromycin for trachoma control

BACKGROUND

Mass drug treatment with azithromycin (MDA) is part of the WHO-endorsed 'SAFE' strategy for trachoma control in endemic communities. MDA has been associated with reduced trachoma prevalence and short-term reductions in other bacterial infections, but can also lead to increased circulation of macrolide-resistant bacteria.

METHODS

We prospectively monitored macrolide resistance in fecal E. coli collected from young children participating in the PRET+ Study in rural Tanzania. MDA was administered in four villages with >10% trachoma prevalence. Four nearby communities with lower trachoma prevalence served as controls. Rectal swabs were collected during cross-sectional surveys performed at baseline, 1, 3 and 6 months after MDA. Fecal E. coli isolates were screened for macrolide susceptibility using disc diffusion and minimum inhibitory concentration methods. Cross-sectional and longitudinal differences in resistance prevalence by MDA exposure were compared using t-tests and logistic regression.

RESULTS

There was no difference in the proportion of individuals carrying azithromycin-resistant E. coli at baseline (0.21 vs. 0.16, P > 0.05). Azithromycin resistance carriage prevalence remained stable over follow-up in non-MDA villages but increased sharply in MDA villages (0.61 at 1 month, 0.42 at 3 months and 0.31 at 6 months). MDA exposure was highly associated with azithromycin resistance carriage at 1 month post-MDA (OR 15.27, P < 0.001) and subsequent surveys. Younger age and recent diarrhoea were also associated with increased odds of resistance (P < 0.01).

CONCLUSIONS

MDA resulted in significantly increased prevalence of macrolide resistance in E. coli. Although MDA is effective for trachoma elimination, it has costs; it is essential to monitor antimicrobial resistance following MDA.

On the pathway to better birth outcomes? A systematic review of azithromycin and curable sexually transmitted infections

The WHO recommends the administration of sulfadoxine-pyrimethamine (SP) to all pregnant women living in areas of moderate (stable) to high malaria transmission during scheduled antenatal visits, beginning in the second trimester and continuing to delivery. Malaria parasites have lost sensitivity to SP in many endemic areas, prompting the investigation of alternatives that include azithromycin-based combination (ABC) therapies. Use of ABC therapies may also confer protection against curable sexually transmitted infections and reproductive tract infections (STIs/RTIs). The magnitude of protection at the population level would depend on the efficacy of the azithromycin-based regimen used and the underlying prevalence of curable STIs/RTIs among pregnant women who receive preventive treatment. This systematic review summarizes the efficacy data of azithromycin against curable STIs/RTIs.

Advances in sampling and screening for chlamydia

Chlamydia is the most commonly diagnosed bacterial sexually transmitted infection in the developed world, with diagnosis rates continuing to increase each year. As chlamydia is largely asymptomatic, screening and treatment is the main way to detect cases and reduce transmission. Recent advances in self-collected specimens and laboratory tests has made chlamydia screening easier to implement as well as possible in nonclinical settings. This review will discuss new approaches to specimen collection and how these have expanded opportunities for reaching target populations for chlamydia screening. Furthermore, it will discuss how advanced molecular microbiological methods can be used with self-collected specimens to further our knowledge of the epidemiology of chlamydia and the dynamics of transmission.

Presentation of clinically suspected persistent chlamydial infection: a case series

In vivo antimicrobial resistance has yet to be documented in Chlamydia trachomatis; however, there have been anecdotal reports of persistent infection. The purpose of this case series was to describe a group of patients who have persistent chlamydia infection despite adequate treatment and where re-infection was considered unlikely. Patients were selected using a clinical questionnaire. For inclusion patients had to have tested positive for C. trachomatis, at least twice, using a nucleic acid amplification test despite having been fully compliant with at least two rounds of recommended therapy and be deemed to be at low risk of re-infection. Patients were grouped into categories based on sexual behaviour. Twenty-eight patients are included in this case series; 46% declared no sexual contact since initial diagnosis (category 1), a further 36% declaring contact that was considered low risk of re-infection (categories 2-4); 61% showed signs and symptoms at initial presentation increasing to 75% at re-attendance. Thirty-nine percent of patients received azithromycin only while 48% received doxycycline also. This case series identifies patients with persistent chlamydia despite receiving treatment. There is a need for a case definition of clinical treatment failure, development of susceptibility testing methods and guidance on appropriate treatment for patients with persistent infection.

Chlamydial biology and its associated virulence blockers

Chlamydiales are obligate intracellular parasites of eukaryotic cells. They can be distinguished from other Gram-negative bacteria through their characteristic developmental cycle, in addition to special biochemical and physical adaptations to subvert the eukaryotic host cell. The host spectrum includes humans and other mammals, fish, birds, reptiles, insects and even amoeba, causing a plethora of diseases. The first part of this review focuses on the specific chlamydial infection biology and metabolism. As resistance to classical antibiotics is emerging among Chlamydiae as well, the second part elaborates on specific compounds and tools to block chlamydial virulence traits, such as adhesion and internalization, Type III secretion and modulation of gene expression.

Chlamydia trachomatis, Mycoplasma genitalium, and Trichomonas vaginalis infections in men with nongonococcal urethritis: predictors and persistence after therapy

BACKGROUND

Chlamydia trachomatis (CT), Mycoplasma genitalium (MG), and Trichomonas vaginalis (TV) are sexually transmitted infections (STIs) associated with nongonococcal urethritis (NGU). We assessed their predictors and persistence after treatment.

METHODS

We analyzed data from an NGU treatment trial among symptomatic heterosexual men aged 16-45 years from STI clinics. Nucleic acid amplification tests detected CT, MG, and TV at baseline and at 1 and 4 weeks after therapy. Associations between variables and STI detection were investigated.

RESULTS

Among 293 participants, 44% had CT, 31% had MG, and 13% had TV at baseline. In multivariate analysis, CT infection was associated with young age and STI contact. Young age was also associated with MG, and having ≥ 1 new partner was negatively associated with TV. We detected persistent CT in 12% and MG in 44% of participants at 4 weeks after therapy, which were associated with signs and symptoms of NGU. Persistent CT was detected in 23% of participants after azithromycin treatment vs 5% after doxycycline treatment (P = .011); persistent MG was detected in 68% of participants after doxycycline vs 33% after azithromycin (P = .001). All but 1 TV infection cleared after tinidazole.

CONCLUSIONS

Persistent CT and MG after treatment of NGU are common, and were associated with clinical findings and drug regimen.

Whole-genome analysis of diverse Chlamydia trachomatis strains identifies phylogenetic relationships masked by current clinical typing

Chlamydia trachomatis is responsible for both trachoma and sexually transmitted infections causing substantial morbidity and economic cost globally. Despite this, our knowledge of its population and evolutionary genetics is limited. Here we present a detailed whole genome phylogeny from representative strains of both trachoma and lymphogranuloma venereum (LGV) biovars from temporally and geographically diverse sources. Our analysis demonstrates that predicting phylogenetic structure using the ompA gene, traditionally used to classify Chlamydia, is misleading because extensive recombination in this region masks true relationships. We show that in many instances ompA is a chimera that can be exchanged in part or whole, both within and between biovars. We also provide evidence for exchange of, and recombination within, the cryptic plasmid, another important diagnostic target. We have used our phylogenetic framework to show how genetic exchange has manifested itself in ocular, urogenital and LGV C. trachomatis strains, including the epidemic LGV serotype L2b.

Treatment of chlamydial infections

INTRODUCTION

Chlamydiae are obligate intracellular bacterial pathogens whose entry into mucosal epithelial cells is required for intracellular survival and subsequent growth. The life cycle of Chlamydia spp. and the ability to cause persistent, often subclinical infection, has major ramifications for diagnosis and treatment of C. trachomatis and C. pneumoniae infections in humans.

AREAS COVERED

This up-to-date review describes the current state of knowledge of antimicrobial susceptibilities and treatment of genital infections due to C. trachomatis and respiratory infections due to C. pneumoniae.

EXPERT OPINION

Chlamydiae are susceptible to antibiotics that interfere with DNA and protein synthesis, including tetracyclines, macrolides and quinolones, which are the compounds that have been most extensively studied and used for treatment of human infection. Treatment of individuals with C. trachomatis genital infection prevents sexual transmission and complications, including pelvic inflammatory disease. Treatment of pregnant women will prevent the transmission of infection to infants during delivery. The benefits of treatment of respiratory infections due to C. pneumoniae are more difficult to assess, primarily because of the lack of FDA-approved, specific diagnostic tests for detection of the organism in clinical samples. The majority of published studies have relied on serology for diagnosis, making it difficult to assess microbiologic efficacy.

In vitro recombinants of antibiotic-resistant Chlamydia trachomatis strains have statistically more breakpoints than clinical recombinants for the same sequenced loci and exhibit selection at unexpected loci

Lateral gene transfer (LGT) is essential for generating between-strain genomic recombinants of Chlamydia trachomatis to facilitate the organism's evolution. Because there is no reliable laboratory-based gene transfer system for C. trachomatis, in vitro generation of recombinants from antibiotic-resistant strains is being used to study LGT. However, selection pressures imposed on in vitro recombinants likely affect statistical properties of recombination relative to naturally occurring clinical recombinants, including prevalence at particular loci. We examined multiple loci for 16 in vitro-derived recombinants of ofloxacin- and rifampin-resistant L(1) and D strains, respectively, grown with both antibiotics, and compared these with the same sequenced loci among 11 clinical recombinants. Breakpoints and recombination frequency were examined using phylogenetics, bioinformatics, and statistics. In vitro and clinical isolates clustered perfectly into two groups, without misclassification, using Ward's minimum variance based on breakpoint data. As expected, gyrA (confers ofloxacin resistance) and rpoB (confers rifampin resistance) had significantly more breakpoints among in vitro recombinants than among clinical recombinants (P < 0.0001 and P = 0.02, respectively, using the Wilcoxon rank sum test). Unexpectedly, trpA also had significantly more breakpoints for in vitro recombinants (P < 0.0001). There was also significant selection at other loci. The strongest bias was for ompA in strain D (P = 3.3 × 10(-8)). Our results indicate that the in vitro model differs statistically from natural recombination events. Additional genomic studies are needed to determine the factors responsible for the observed selection biases at unexpected loci and whether these are important for LGT to inform approaches for genetically manipulating C. trachomatis.

An Unusual Strain of Haemophilus Parasuis that Fails to React in a Species-Specific Polymerase Chain Reaction Assay

A total of 30 nasal swabs from pigs preweaned and 11 nasal swabs from sick weaned pigs on a farm in Queensland, Australia, were cultured for the presence of Haemophilus parasuis. Enterobacterial repetitive intergenic consensus polymerase chain reaction (ERIC-PCR) genotyping and indirect hemagglutination and gel diffusion serotyping were performed on the retrieved H. parasuis isolates. A total of 3 genotypes were recognized among the 42 isolates recovered, and 4 representative isolates of each genotype were found to be nontypeable in the Kielstein/Rapp-Gabrielson serotyping scheme. A total of 20 of the 22 isolates of genotype 1 did not amplify in the species-specific conventional PCR number 1 (cPCR1) based on the 16S ribosomal RNA (rRNA) gene but did give the expected PCR amplicon in 2 other species-specific PCR assays, one of which is also based on the 16S rRNA gene. Nine selected isolates representing all genotypes, both positive and negative in the cPCR1, were sequenced, and all showed a 4-base mutation occurring at the forward primer annealing site. The quadruple base pair substitution from GTGG to TGTT near the 3' end of the forward primer sequence may explain the failure of amplification. Diagnostic laboratories should be aware that such failures can occur and should consider having an alternative PCR available to confirm negative results or, alternatively, use phenotypic characteristics for the identification of suspect H. parasuis isolates.

Antibiotic resistance in Chlamydiae

There are few documented reports of antibiotic resistance in Chlamydia and no examples of natural and stable antibiotic resistance in strains collected from humans. While there are several reports of clinical isolates exhibiting resistance to antibiotics, these strains either lost their resistance phenotype in vitro, or lost viability altogether. Differences in procedures for chlamydial culture in the laboratory, low recovery rates of clinical isolates and the unknown significance of heterotypic resistance observed in culture may interfere with the recognition and interpretation of antibiotic resistance. Although antibiotic resistance has not emerged in chlamydiae pathogenic to humans, several lines of evidence suggest they are capable of expressing significant resistant phenotypes. The adept ability of chlamydiae to evolve to antibiotic resistance in vitro is demonstrated by contemporary examples of mutagenesis, recombination and genetic transformation. The isolation of tetracycline-resistant Chlamydia suis strains from pigs also emphasizes their adaptive ability to acquire antibiotic resistance genes when exposed to significant selective pressure.

Impact of azithromycin resistance mutations on the virulence and fitness of Chlamydia caviae in guinea pigs

Azithromycin (AZM) is a major drug used in the treatment and prophylaxis of infections caused by Chlamydia, yet no significant clinical resistance has been reported for these obligate intracellular bacteria. Nevertheless, spontaneous AZM resistance (Azm(r)) arose in vitro at frequencies ranging from 3 x 10(-8) to 8 x 10(-10) for clonal isolates of Chlamydia caviae, which is a natural pathogen of guinea pigs. Sequencing of the unique 23S rRNA gene copy in 44 independent Azm(r) isolates identified single mutations at position A(2058) or A(2059) (Escherichia coli numbering system). While SP(6)AZ(1) (A(2058)C) and SP(6)AZ(2) (A(2059)C) Azm(r) mutants showed growth defects in cell culture and were less pathogenic in the guinea pig ocular infection model than in the parent SP(6), the three isogenic C. caviae isolates grew equally well in the animal. On the other hand, coinoculation of the C. caviae parent strain with one of the Azm(r) strains was detrimental for the mutant strain. This apparent lack of association between pathology and bacterial load in vivo showed that virulence of the two Azm(r) mutants of C. caviae was attenuated. While chlamydial growth in vitro reflects the ability of the bacteria to multiply in permissive cells, survival in the host is a balance between cellular multiplication and clearance by the host immune system. The obligate intracellular nature of Chlamydia may therefore limit emergence of resistance in vivo due to the strength of the immune response induced by the wild-type antibiotic-sensitive bacteria at the time of antibiotic treatment.

Chlamydia trachomatis today: treatment, detection, immunogenetics and the need for a greater global understanding of chlamydial disease pathogenesis

Chlamydia trachomatis is an important human pathogen causing a myriad of severe and debilitating diseases. While antibiotics have been a mainstay of treatment, there is increasing evidence for potential drug resistance, reinfection and persistent infections that require a reevaluation of treatment strategies. A critical need to address these issues will be a rapid, sensitive and cost-effective diagnostic that can be used for global screening, treatment and test-of-cure of infected individuals instead of empirical therapy that not only drives drug resistance but is not costeffective. This type of diagnostic would allow clinicians and researchers to evaluate the true incidence and prevalence of chlamydial infections in both developed and developing countries. There are extremely limited data on chlamydial sexually transmitted diseases (STDs) in many developing countries, including those in Central and South America. In addition, advancing our understanding of chlamydial disease pathogenesis will require an evaluation of host genetic susceptibility to infection and sequelae. We provide preliminary data on rates of chlamydial STDs and host genetic factors that predispose to infection among adolescent pregnant and nonpregnant commercial sex worker populations residing in Quito, Ecuador.

A novel inhibitor of Chlamydophila pneumoniae protein kinase D (PknD) inhibits phosphorylation of CdsD and suppresses bacterial replication

Background

We have shown previously that Chlamydophila pneumoniae contains a dual-specific Ser/Thr protein kinase that phosphorylates CdsD, a structural component of the type III secretion apparatus. To further study the role of PknD in growth and development we sought to identify a PknD inhibitor to determine whether PknD activity is required for replication.

Results

Using an in vitro kinase assay we screened 80 known eukaryotic protein kinase inhibitors for activity against PknD and identified a 3'-pyridyl oxindole compound that inhibited PknD autophosphorylation and phosphorylation of CdsD. The PknD inhibitor significantly retarded the growth rate of C. pneumoniae as evidenced by the presence of very small inclusions with a reduced number of bacteria as seen by electron microscopy. These inclusions contained the normal replicative forms including elementary bodies (EB), intermediate bodies (IB) and reticulate bodies (RB), but lacked persistent bodies (PB), indicating that induction of persistence was not the cause of reduced chlamydial growth. Blind passage of C. pneumoniae grown in the presence of this PknD inhibitor for 72 or 84 hr failed to produce inclusions, suggesting this compound blocks an essential step in the production of infectious chlamydial EB. The compound was not toxic to HeLa cells, did not block activation of the MEK/ERK pathway required for chlamydial invasion and did not block intracellular replication of either Chlamydia trachomatis serovar D or Salmonella enterica sv. Typhimurium suggesting that the inhibitory effect of the compound is specific for C. pneumoniae.

Conclusion

We have identified a 3'-pyridyl oxindole compound that inhibits the in vitro kinase activity of C. pneumoniae PknD and inhibits the growth and production of infectious C. pneumoniae progeny in HeLa cells. Together, these results suggest that PknD may play a key role in the developmental cycle of C. pneumoniae.

Genital Chlamydia trachomatis infections

Chlamydia trachomatis infections affect young, sexually active persons. Risk factors include multiple partners and failure to use condoms. The incidence of infection has increased in the past 10 years. Untreated C. trachomatis infections are responsible for a large proportion of salpingitis, ectopic pregnancy, infertility and, to a lesser extent, epididymitis. Screening is a possible intervention to control the infection, which is often asymptomatic. The emergence of lymphogranuloma venereum proctitis in men who have sex with men, in Europe, and of a variant with a deletion in the cryptic plasmid, in Sweden, are new features of C. trachomatis infections in the last years. A diagnosis is best made by using nucleic acid amplification tests, because they perform well and do not require invasive procedures for specimen collection. Single-dose therapy has been a significant development for treatment of an uncomplicated infection of the patient and his or her sexual partner.