Rachel Pitt

Whole-genome sequences of Chlamydia trachomatis directly from clinical samples without culture

The use of whole-genome sequencing as a tool for the study of infectious bacteria is of growing clinical interest. Chlamydia trachomatis is responsible for sexually transmitted infections and the blinding disease trachoma, which affect hundreds of millions of people worldwide. Recombination is widespread within the genome of C. trachomatis, thus whole-genome sequencing is necessary to understand the evolution, diversity, and epidemiology of this pathogen. Culture of C. trachomatis has, until now, been a prerequisite to obtain DNA for whole-genome sequencing; however, as C. trachomatis is an obligate intracellular pathogen, this procedure is technically demanding and time consuming. Discarded clinical samples represent a large resource for sequencing the genomes of pathogens, yet clinical swabs frequently contain very low levels of C. trachomatis DNA and large amounts of contaminating microbial and human DNA. To determine whether it is possible to obtain whole-genome sequences from bacteria without the need for culture, we have devised an approach that combines immunomagnetic separation (IMS) for targeted bacterial enrichment with multiple displacement amplification (MDA) for whole-genome amplification. Using IMS-MDA in conjunction with high-throughput multiplexed Illumina sequencing, we have produced the first whole bacterial genome sequences direct from clinical samples. We also show that this method can be used to generate genome data from nonviable archived samples. This method will prove a useful tool in answering questions relating to the biology of many difficult-to-culture or fastidious bacteria of clinical concern.

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

Chlamydia trachomatis is the worlds 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 pathogens 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.

Chlamydia and gonorrhoea contamination of clinic surfaces

Introduction Nucleic acid amplification tests, with their ability to detect very small amounts of nucleic acid, have become the principle diagnostic tests for Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (GC) in many sexual health clinics. The aim of this study was to investigate the extent of surface contamination with CT and GC within a city centre sexual health clinic and to evaluate the potential for contamination of containers used for the collection of self-taken swabs. Method Surface contamination with CT and GC was assessed by systematically sampling 154 different sites within one clinic using transcription-mediated amplification (TMA), quantitative PCR and culture. The caps of containers used by patients to collect self-taken samples were also tested for CT and GC using TMA. Results Of the 154 sites sampled, 20 (13.0%) tested positive on TMA. Of these, five (3.2%) were positive for CT alone, 11 (7.1%) for GC alone and four (2.6%) for both CT and GC. The proportion of GC TMA-positive test results differed by gender, with 11 (18.3%) positive results from the male patient clinic area compared with one (1.6%) from the female area (p=0.002). Positive samples were obtained from a variety of locations in the clinic, but the patient toilets were more likely to be contaminated than examination rooms (p=0.015). Quantitative PCR and culture assays were negative for all samples. 46 caps of the containers used for self-taken swabs were negative for both CT and GC on TMA testing. Conclusions Surface contamination with chlamydial and gonococcal rRNA can occur within sexual health clinics, but the quantity of nucleic acid detected is low and infection risk to patients and staff is small. There remains a potential risk of contamination of patient samples leading to false-positive results.

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, Fishers 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.

O031 Pelvic Inflammatory Disease (PID), Mycoplasma genitalium and macrolide resistance in England

Background/introduction Mycoplasma genitalium (MG) is increasingly implicated in PID pathogenesis with many studies showing MG is as common as chlamydia in high-risk women. Current PID treatment guidelines specify antibiotics with low efficacy against MG. Increasing reports of macrolide resistance suggests first line treatment for MG (azithromycin) may have limitations. Aim(s)/objectives To document rates of MG in a cohort of women with acute PID, and the proportion with baseline macrolide resistance. Methods As part of a multicentre, open-label, non-inferiority RCT comparing ofloxacin/metronidazole (arm-1) with azithromycin 1g day-1; 500 mg od day 2–5, metronidazole/ceftriaxone (arm-2), samples were collected for baseline chlamydia, gonorrhoea and mycoplasma infection. Microbiological cure rates were documented at 6–8 weeks. Positive MG specimens were examined for macrolide resistance using a 23S rRNA PCR. Results 313 women were recruited, median age 25. Preliminary results showed chlamydia was confirmed in 9.5%, MG in 8.2% and gonorrhoea in 0.4%. Of the 16 samples available for resistance testing, 9 (56%) had macrolide resistance mutations (A2058G/T, A2059G/C) at baseline. The reference laboratory received test-of-cure samples for only 8 patients with MG, of which 6 were negative, however 2 remained positive, both with A2059G nucleotide substitutions. Further results will be presented. Discussion/conclusion MG infection was nearly as common as chlamydia in this cohort. Failure of patients to return at 6–8 weeks affected our ability to properly assess test-of-cure rates. Baseline macrolide resistance was unexpectedly high and impacted negatively on treatment success.

Detection of markers predictive of macrolide and fluoroquinolone resistance in Mycoplasma genitalium from patients attending sexual health services in England

Objectives Resistance to both macrolides and fluoroquinolones has been reported in Mycoplasma genitalium; however, due to limited diagnostics, studies are often small and confined to specific geographical areas. This study sought to determine the rate of predicted resistance in M. genitalium-positive specimens referred for diagnostic testing. Methods Seventy-four M. genitalium-positive specimens, referred to the national reference laboratory (2010-2013) from 19 centres across England, were blinded and anonymised. Specimens were examined for markers predictive of resistance to macrolides and fluoroquinolones using PCR followed by sequence analysis of 23S rRNA gene, or gyrA and parC, respectively. Results 23S rRNA gene PCR sequencing revealed that 82.4% (61/74) of specimens harboured a single nucleotide polymorphism (SNP) associated with macrolide resistance. Differences were observed between the rates of predicted macrolide resistance in male (95.1% (58/61)) and female (23.1% (3/13)) patients (P = <0.001). By contrast, all specimens for which sequencing data were available (73/74) yielded wild-type gyrA sequences; and 58/61 (95.1%) had wild-type parC genes. Three specimens (3/61 4.9%) had SNPs in the parC gene associated with fluoroquinolone treatment failure, and all three also had predicted resistance to macrolides. Conclusions Eighty-two per cent and 4.9% of M. genitalium specimens had SNPs associated with macrolide and fluoroquinolone resistance, respectively. Due to lack of widespread availability of testing for M. genitalium in the UK, this study sample was likely to be sourced from patients who may have already failed first-line macrolide therapy. Nevertheless, this study highlights the need for both greater access to M. genitalium diagnostics and genetic antimicrobial resistance testing.

Chlamydia trachomatis in Cervical Lymph Node of Man with Lymphogranuloma Venereum, Croatia, 20141

We report an HIV-infected person who was treated for lymphogranuloma venereum cervical lymphadenopathy and proctitis in Croatia in 2014. Infection with a variant L2b genovar of Chlamydia trachomatis was detected in a cervical lymph node aspirate. A prolonged course of doxycycline was required to cure the infection.

Evaluation of the Mycoplasma genitalium Resistance Plus kit for the detection of M. genitalium and mutations associated with macrolide resistance

Objectives To compare performance of the ResistancePlus kit (SpeeDx, Australia) with in-house methods for the detection of Mycoplasma genitalium-specific DNA and mutations associated with resistance to macrolide antimicrobials, directly from clinical specimens. Methods Assay specificity and sensitivity was analysed using DNA from 46 non-M. genitalium organisms and standard curve analysis, respectively. A panel of archived DNA extracted from 97 M. genitalium-positive clinical specimens, for which the macrolide susceptibility genotype had been previously determined, were tested on the assay and results compared. Results Final analytical specificity was 100%. Sensitivity was detected to at least 140 genome copies/µL. The assay detected M. genitalium in 92/97 (94.9%, 95% CI 88.4% to 98.3%) previously positive specimens. The genetic macrolide susceptibility assigned was concordant with previous results in 85/92 (92.4%, 95% CI 85.0% to 96.9%) specimens or 85/97 (87.6%, 95% CI: 79.4% to 93.4%) when the false-negative specimens were included. On seven (7/92, 7.6%) occasions, resistant specimens were called susceptible. Further testing resolved discrepancies for all but five (5.2%) specimens. Conclusions The ResistancePlus assay generally performed well in comparison to methods currently employed at the reference laboratory. It detected a range of different mutations; however, a small number of specimens that were genotyped as macrolide resistant by Sanger sequencing were either not detected by the assay or were genotyped as susceptible. This could impact on treatment outcomes if assay results were used for patient management.