Assessing the added value of group B Streptococcus maternal immunisation in preventing maternal infection and fetal harm: population surveillance study.

OBJECTIVE: To assess the incidence of maternal group B Streptococcus (GBS) infection in England. DESIGN: Population surveillance augmented through data linkage. SETTING: England. POPULATION: All pregnant women accessing the National Health Service (NHS) in England. METHODS: Invasive GBS (iGBS) infections during pregnancy or within 6 weeks of childbirth were identified by linking Public Health England (PHE) national microbiology surveillance data for 2014 to NHS hospital admission records. Capsular serotypes of GBS were determined by reference laboratory typing of clinical isolates from women aged 15-44 years. Post-caesarean section surgical site infection (SSI) caused by GBS was identified in 21 hospitals participating in PHE SSI surveillance (2009-2015). MAIN OUTCOME MEASURES: iGBS rate per 1000 maternities; risk of GBS SSI per 1000 caesarean sections. RESULTS: Of 1601 patients diagnosed with iGBS infections in England in 2014, 185 (12%) were identified as maternal infections, a rate of 0.29 (95% CI 0.25-0.33) per 1000 maternities and representing 83% of all iGBS cases in women aged 18-44 years. Seven (3.8%) were associated with miscarriage. Fetal outcome identified excess rates of stillbirth (3.4 versus 0.5%) and extreme prematurity (<28 weeks of gestation, 3.7 versus 0.5%) compared with national averages (P < 0.001). Caesarean section surveillance in 27 860 women (21 hospitals) identified 47 cases of GBS SSI, with an estimated 4.24 (3.51-5.07) per 1000 caesarean sections, a median time-to-onset of 10 days (IQR 7-13 days) and ten infections that required readmission. Capsular serotype analysis identified a diverse array of strains with serotype III as the most common (43%). CONCLUSIONS: Our assessment of maternal GBS infection in England indicates the potential additional benefit of GBS vaccination in preventing adverse maternal and fetal outcomes.

A protracted iGAS outbreak in a long-term care facility 2014-2015: control measures and the use of whole-genome sequencing.

BACKGROUND: In 2014, two residents of a long-term care facility (LTCF) developed invasive group A streptococcal (iGAS) infections with identical typing (emm 11), resulting in one death. The second resident recovered but had a subsequent episode of emm 11 iGAS infection 10 months later. This second episode was linked to a third case, within 12 days, leading to a further outbreak investigation. AIM: To combine different techniques to establish whether this was a protracted outbreak, understand transmission pathways and inform appropriate control measures. METHODS: Following a routine response to the first cluster, the second investigation included a care record review. This informed network analysis of case interactions with staff and visitors during 10 days prior to infection. These data were combined with post-outbreak whole-genome sequencing (WGS) using isolates from cases, and staff and resident screening (44 GAS isolates: 11 outbreak-related and 33 sporadic isolates). FINDINGS: Two of the three confirmed iGAS cases died (one suffered two episodes). All iGAS cases, and six non-invasive isolates from 2015, were emm 11 (monophylogenetic WGS clade). Network analysis highlighted only indirect contact through staff-visitor interactions between iGAS cases in 2015. This suggested a common source and transmission propagation through carriage and/or environmental contamination over an 11-month period. CONCLUSIONS: This outbreak highlighted benefits of staff/resident screening and typing as part of routine response. Network analysis and highly discriminatory WGS clarified the protracted nature of the outbreak, supporting findings of hygiene and infection control issues and adding to our understanding of the epidemiology.

A real-time PCR for specific detection of the Legionella pneumophila serogroup 1 ST1 complex.

OBJECTIVE: Legionella pneumophila serogroup 1 (Lp1) sequence type (ST) 1 is globally widespread in the environment and accounts for a significant proportion of Legionella infections, including nosocomial Legionnaires' disease (LD). This study aimed to design a sensitive and specific detection method for Lp ST1 that will underpin epidemiological investigations and risk assessment. METHODS: A total of 628 Lp genomes (126 ST1s) were analyzed by comparative genomics. Interrogation of more than 900 accessory genes revealed seven candidate targets for specific ST1 detection and specific primers and hydrolysis probes were designed and evaluated. The analytical sensitivity and specificity of the seven primer and probe sets were evaluated on serially diluted DNA extracted from the reference strain CIP107629 and via qPCR applied on 200 characterized isolates. The diagnostic performance of the assay was evaluated on 142 culture-proven clinical samples from LD cases and a real-life investigation of a case cluster. RESULTS: Of seven qPCR assays that underwent analytical validation, one PCR target (lpp1868) showed higher sensitivity and specificity for ST1 and ST1-like strains. The diagnostic performance of the assay using respiratory samples corresponded to a sensitivity of 95% (19/20) (95% CI (75.1-99.9)) and specificity of 100% (122/122) (95% CI (97-100)). The ST1 PCR assay could link two out of three culture-negative hospitalized LD cases to ST1 during a real-time investigation. CONCLUSION: Using whole genome sequencing (WGS) data, we developed and validated a sensitive and specific qPCR assay for the detection of Lp1 belonging to the ST1 clonal complex by amplification of the lpp1868 gene. The ST1 qPCR is expected to deliver an added value for Lp control and prevention, in conjunction with other recently developed molecular assays.

Real-time whole genome sequencing to control a Streptococcus pyogenes outbreak at a national orthopaedic hospital.

BACKGROUND: Whole genome sequencing (WGS) of Streptococcus pyogenes linked to invasive disease has been used to identify and investigate outbreaks. The clinical application of WGS in real-time for outbreak control is seldom employed. AIMS: A fatal case of bacteraemia at a national orthopaedic hospital prompted an outbreak investigation to identify carriers and halt transmission using real-time WGS. METHODS: Retrospective surveillance was conducted to identify patients with Streptococcus pyogenes infections in the last year. Upon contact tracing, four patients and 179 staff were screened for Streptococcus pyogenes carriage. All isolates identified were emm-typed. WGS was performed in real-time on a subset of isolates. FINDINGS: Twelve isolates of Streptococcus pyogenes from the index case, two patients and eight staff were identified. Six isolates were emm 1.0, including the index case and five staff isolates. The remaining isolates belonged to distinct emm types. WGS analysis was undertaken on the six emm 1.0 isolates. Five were indistinguishable by single nucleotide polymorphism (SNP) analysis, with 0 SNP distance, and one had one SNP difference, supporting the hypothesis of recent local transmission. All screen-positive healthcare workers were offered treatment with penicillin or clindamycin. No further cases were identified. CONCLUSION: The increased molecular discrimination of WGS confirmed the clustering of these cases and the outbreak was contained. This demonstrates the clinical utility of WGS in managing outbreaks of invasive Streptococcus pyogenes in real-time and we recommend its implementation as a routine clinical service.

Genomic sequence investigation Streptococcus pyogenes clusters in England (2010-2015).

OBJECTIVES: To analyse genomic sequence data of referred Streptococcus pyogenes isolates and those pertaining to selected elderly/nursing care or maternity clusters from 2010 to 2015 to ascertain genomic differences between epidemiologically related isolates and unrelated isolates from outbreaks of disease. METHODS: The genomic sequences of 134 S. pyogenes isolates from 21 clusters of infection in elderly care or maternity settings from 2010 to 2015 were analysed using bioinformatics to ascertain genomic phylogeny, single nucleotide polymorphism (SNP) differences and statistical outliers from epidemiologically defined outbreaks. Analysis was undertaken within clusters and compared with sporadic isolates from geographically distinct outbreaks of S. pyogenes infection. RESULTS: Genomic sequence analysis of 21 outbreaks of S. pyogenes infection ranged in size from a single patient (with colonized healthcare worker link) to 18 patient cases of group A streptococcus (GAS) infection in a single setting. Seventeen healthcare workers were identified in 8 of 21 outbreaks with the associated outbreak strain, with multiple staff in 2 of 21 outbreaks. Genomic sequences from epidemiologically linked isolates from patients, staff and healthcare environmental settings were highly conserved, differing by 0-1 SNP in some cases and mirrored geographical data. Four of 21 outbreaks had environmental contamination with the outbreak strain, indistinguishable or of limited SNP difference to the patient isolates. Genomic SNP analysis enabled exclusion of ten isolates from epidemiological outbreaks. CONCLUSIONS: Genomic discrimination can be applied to assist outbreak investigation. It enabled confirmation or exclusion of GAS cases from epidemiologically defined outbreaks. Colonization of healthcare workers and environmental contamination with the outbreak strain was demonstrated for several outbreaks.

Whole-genome sequencing in the investigation of recurrent invasive group A streptococcus outbreaks in a maternity unit.

BACKGROUND: The clinical manifestations of group A streptococcus (GAS) (Streptococcus pyogenes) are diverse, ranging from asymptomatic colonization to devastating invasive disease. Maternity-related clusters of invasive GAS (iGAS) infection are complex to investigate and control, especially if recurrent. AIM: To investigate three episodes of emm 75 GAS/iGAS infection in maternity patients at one hospital site over a four-year period (two with monophyletic ancestry). METHODS: The episodes are described, together with whole-genome sequence (WGS) isolate analyses. Single nucleotide polymorphism differences were compared with contemporaneous emm 75 genomes. FINDINGS: Over the four-year study period, seven mothers had emm 75 GAS/iGAS and one mother had emm 3 iGAS (in year 4) (subsequently discounted as linked). Three (clinical/screening samples) of the seven babies of emm-75-positive mothers and three screened healthcare workers were positive for emm 75 GAS. WGS similarity suggested a shared ancestral lineage and a common source transmission, but directionality of transmission cannot be inferred. However, the findings indicate that persistence of a particular clone in a given setting may be long term. CONCLUSIONS: Occupational health procedures were enhanced, staff were screened, and antibiotic therapy was provided to GAS-positive staff and patients. The definitive source of infection could not be identified, although staff-patient transmission was the most likely route. The pattern of clonal GAS transmission over the four-year study period suggests that long-term persistence of GAS may have occurred.

Antibiotic susceptibility of Legionella pneumophila strains isolated in England and Wales 2007-17.

Objectives: Antibiotic susceptibility of Legionella pneumophila is poorly understood, with treatment of Legionnaires' disease often based on empirical choice. The aim of this study was to determine the antibiotic susceptibility of L. pneumophila strains. Methods: Antibiotic susceptibility of 92 L. pneumophila strains isolated in England and Wales between 2007 and 2017 was determined using a microbroth dilution methodology for each agent tested. MICs and MBCs were determined and compared with published intracellular concentrations of each agent tested. Results: The MIC range of erythromycin was 0.06-1 mg/L, the MIC range of rifampicin was 0.0001 mg/L, the MIC range of ciprofloxacin was 0.004-0.25 mg/L and the MIC range of levofloxacin and moxifloxacin was 0.03-0.25 mg/L. The MBC range of erythromycin was 1-32 mg/L, but the MBC range of ciprofloxacin was the same as the MIC range. For levofloxacin and moxifloxacin the MBC range was elevated by one dilution and two dilutions, respectively. Typically, intracellular bronchial secretion concentrations of erythromycin might be expected to reach a suitable level to exceed the MIC range; however, 91 of 92 (98.9%) isolates had an MBC below the expected intracellular concentrations, which indicated erythromycin may have variable efficacy. MIC and MBC values of ciprofloxacin, levofloxacin and moxifloxacin were below achievable intracellular levels within bronchial secretions. Comparison of the MIC/MBC correlation showed very little clustering for erythromycin, but strong clustering for levofloxacin and to a lesser extent ciprofloxacin. Conclusions: Use of the MIC/MBC linkage analysis seems an appropriate way forward for antimicrobial susceptibility testing and supports current guidance recommending levofloxacin for the treatment of Legionnaires' disease.

Low genomic diversity of Legionella pneumophila within clinical specimens.

OBJECTIVES: Legionella pneumophila is the leading cause of Legionnaires' disease, a severe form of pneumonia acquired from environmental sources. Investigations of both sporadic cases and outbreaks rely mostly on analysis of a single to a few colony pick(s) isolated from each patient. However, because of the lack of data describing diversity within single patients, the optimal number of picks is unknown. Here, we investigated diversity within individual patients using sequence-based typing (SBT) and whole-genome sequencing (WGS). METHODS: Ten isolates of L. pneumophila were obtained from each of ten epidemiologically unrelated patients. SBT and WGS were undertaken, and single-nucleotide polymorphisms (SNPs) were identified between isolates from the same patient. RESULTS: The same sequence type (ST) was obtained for each set of ten isolates. Using genomic analysis, zero SNPs were identified between isolates from seven patients, a maximum of one SNP was found between isolates from two patients, and a maximum of two SNPs was found amongst isolates from one patient. Assuming that the full within-host diversity has been captured with ten isolates, statistical analyses showed that, on average, analysis of one isolate would yield a 70% chance of capturing all observed genotypes, and seven isolates would yield a 90% chance. CONCLUSIONS: SBT and WGS analyses of multiple colony picks obtained from ten patients showed no, or very low, within-host genomic diversity in L. pneumophila, suggesting that analysis of one colony pick per patient will often be sufficient to obtain reliable typing data to aid investigation of cases of Legionnaires' disease.

Have reducing tonsillectomy rates in England led to increasing incidence of invasive Group A Streptococcus infections in children?

OBJECTIVES: To determine whether there is a correlation between falling tonsillectomy numbers and increasing numbers of tonsillitis admissions and invasive Group A ß-haemolytic streptococcus (iGAS) infection in children aged 14 and under in England. DESIGN: An observational cross-sectional study was performed. SETTING: The data extracted covered the period from 1991 until 2014. PARTICIPANTS: Hospital admissions for tonsillectomies, tonsillitis/pharyngitis and all diagnoses of iGAS in children aged 14 and under who had a tonsillectomy. MAIN OUTCOME MEASURES: Correlation between trends in tonsillectomies, tonsillitis/pharyngitis and iGAS. RESULTS: Across all age groups, there was a dramatic reduction in the total number of tonsillectomies performed in England from 28 309 in 1990/1991, down to 6327 in 2013/2014 (77.7% reduction). The numbers of hospital admissions for management of acute tonsillitis and pharyngitis have risen dramatically. iGAS numbers have increased steadily over this time period and more than doubled in children aged 14 and under. There are significant negative correlations between the trend in iGAS infections and numbers of tonsillectomies in all ages. There are also strong positive correlations between the trend in numbers of tonsillitis episodes and the number of iGAS infections in all under 14-year groups; the strongest correlation was seen in the 1- to 4-year age group (+0.92 Pearson correlation coefficient). CONCLUSIONS: There appears to be a correlation between falling tonsillectomy numbers, increasing hospital admissions with tonsillitis and rising iGAS infection in England. Further studies are required to assess the aetiological role of tonsillitis in predisposing to iGAS infection and the potential societal benefit of tonsillectomies.

Rapid detection and evolutionary analysis of Legionella pneumophila serogroup 1 sequence type 47.

OBJECTIVES: Legionella pneumophila serogroup 1 (Lp1) sequence type 47 is the leading cause of legionellosis in north-western Europe, but, surprisingly, it is rarely isolated from environmental samples. Comparative genomics was applied to develop a PCR assay and to better understand the evolution of this strain. METHODS: Comparative analysis of 36 genomes representative of the Lp species was used to identify specific PCR targets, which were then evaluated in silico on 545 sequenced genomes and in vitro on 436 Legionella strains, 106 respiratory samples, and three environmental samples from proven ST47 sources. Phylogenetic analyses were performed to understand the evolution of ST47. RESULTS: The gene LPO_1073 was characterized as being 100% conserved in all 129 ST47 genomes analysed. A real-time PCR designed to detect LPO_1073 was positive for all 110 ST47 strains tested and agreed with culture and typing results previously obtained for 106 respiratory samples. The three environmental samples were also positive. Surprisingly, 26 of the 44 ST109 strains tested among 342 non-ST47 strains scored positive for LPO_1073. SNP-based phylogenetic analysis was undertaken to understand this result: the PCR-positive ST109 genomes were almost identical to ST47 genomes, with the exception of a recombined region probably acquired by ST47 from a ST62(-like) strain. CONCLUSION: The genomic analysis allowed the design of a highly specific PCR assay for rapid detection of ST47 strains. Furthermore, it allowed us to uncover the evolution of ST47 strains from ST109 by homologous recombination with ST62. We hypothesize that this recombination generated the leading cause of legionellosis in north-western Europe.

Heated birthing pools as a source of Legionnaires' disease.

In June 2014 Public Health England confirmed a case of Legionnaires' disease (LD) in a neonate following birth at home in a hired birthing pool incorporating a heater and a recirculation pump which had been filled in advance of labour. The case triggered a public health investigation and a microbiological survey of an additional ten heated birthing pools hired or recently hired to the general public across England. The birthing pool used by the parent of the confirmed case was identified as the source of the neonate's infection following detection of Legionella pneumophila ST48 in both patient and environmental samples. Legionella species were detected by quantitative polymerase chain reaction but not culture in a further three pools together with other opportunistic pathogens identified by culture and matrix-assisted laser desorption ionization-time of flight (MALDI-ToF) mass spectrometry. A Patient Safety Alert from NHS England and Public Health England was issued stating that heated birthing pools filled in advance of labour should not be used for home births. This recommendation remains in place. This investigation in conjunction with other recent reports has highlighted a lack of awareness regarding the microbiological safety of heated birthing pools and their potential to be a source of LD and other opportunistic infections. Furthermore, the investigation raised important considerations with regards to microbiological sampling and testing in such incidents. Public health authorities and clinicians should consider LD in the differential diagnosis of severe respiratory infection in neonates within 14 days of a water birth.

International Mycoplasma pneumoniae typing study: interpretation of M. pneumoniae multilocus variable-number tandem-repeat analysis.

Typing of Mycoplasma pneumoniae by multiple-locus variable-number tandem repeat analysis (MLVA) is increasingly in use. However, no specific internationally agreed guidance is available. Thirty M. pneumoniae DNA samples including serial dilutions of a type strain were sent to six international laboratories to perform MLVA and results were compared. Good correlation was observed, indicating that this methodology can be robustly performed in multiple sites. However, differences due to interpretation of fragment size, repeat sequence identification and repeat numbering led to inconsistency in the final profiles assigned by laboratories. We propose guidelines for interpreting M. pneumoniae MLVA typing and assigning the number of repeats.

Design and validation of a qPCR assay for accurate detection and initial serogrouping of Legionella pneumophila in clinical specimens by the ESCMID Study Group for Legionella Infections (ESGLI).

Prompt detection of Legionella pneumophila is essential for rapid investigation of legionellosis. Furthermore, as the majority of L. pneumophila infections are caused by serogroup 1 (sg1) strains, rapid identification of such strains can be critical in both routine and outbreak scenarios. The ESCMID Study Group for Legionella Infections (ESGLI) was established in 2012 and immediately identified as a priority the validation of a reliable, easy to perform and interpret, cost-effective qPCR assay to standardise the detection of L. pneumophila DNA amongst members. A novel L. pneumophila assay targeting the mip gene was designed and combined with previously published methodologies amplifying the sg1 marker (wzm) and the green fluorescent protein gene (gfp) internal process control. The resulting triplex assay was validated internationally on the three qPCR platforms used by the majority of European Legionella reference laboratories: ABI 7500 (Life Technologies), LightCycler 480 Instrument II (Roche) and Rotor-Gene Q (Qiagen). Clinical and EQA specimens were tested together with a large panel of strains (251 in total) to validate the assay. The assay proved to be 100% specific for L. pneumophila and sg1 DNA both in silico and in vitro. Efficiency values for mip and wzm assays ranged between 91.97 and 97.69%. Limit of detection values estimated with 95% confidence were adopted for mip and wzm assays on all three qPCR platforms. Inhibition was not observed. This study describes a robust assay that could be widely implemented to standardise the molecular detection of L. pneumophila among ESGLI laboratories and beyond.

Prevalence of Trichomonas vaginalis, Mycoplasma genitalium and Ureaplasma urealyticum in men with urethritis attending an urban sexual health clinic.

We conducted a study to determine the prevalence of Trichomonas vaginalis (TV), Mycoplasma genitalium (MG) and Ureaplasma urealyticum (UU) in men with urethritis, attending an urban sexual health clinic, in order to inform screening and treatment policies. Men attending an urban sexual health clinic between June 2011 and January 2012 were evaluated. Urine samples were collected from men with urethritis and tested for Chlamydia trachomatis (CT), Neisseria gonorrhoeae (GC) and TV using transcription-mediated amplification and for MG and UU using polymerase chain reaction. Eighty-three samples were analysed. The prevalence of CT was 33.7% (28/83), GC was 16.8% (14/83), TV was 3.6% (3/83), MG was 12.0% (10/83) and UU was 4.8% (4/83). Fifteen men had recurrent urethritis. Of these, three were found to have had TV, five to have had MG and none to have had UU, at initial presentation. Given the prevalence of MG in this study, there is an urgent need for further larger studies looking at optimal treatment regimens and screening strategies in urethritis.

Increase in scarlet fever notifications in the United Kingdom, 2013/2014.

Increases in scarlet fever above usual seasonal levels are currently being seen across the United Kingdom. Medical practitioners have been alerted to the exceptional increase in incidence. Given the potential for this to signal a population increase in invasive group A streptococcal disease, close monitoring of invasive disease is essential.

Late-onset prosthetic valve endocarditis caused by Mycoplasma hominis, diagnosed using broad-range bacterial PCR.

We report what is believed to be the first case of late-onset prosthetic valve endocarditis caused by Mycoplasma hominis in a case of blood culture-negative endocarditis. The objective of this report is to emphasize the use of a broad-range PCR technique for bacterial 16S rRNA genes in identifying the causative pathogen, thus enabling targeted antimicrobial treatment.

Mycoplasma pneumoniae infection in primary care investigated by real-time PCR in England and Wales.

Real-time PCR was employed to detect a conserved region of the P1 cytadhesin gene of Mycoplasma pneumoniae in combined nose and throat swabs collected from patients attending GP surgeries during 2005-2009 with symptoms of respiratory tract infection (RTI). Samples were collected as part of an annual winter epidemiological and virological linked study in England and Wales. A total of 3,987 samples were tested, 65 (1.7%, 95%CI 1.3-2.1) had detectable M. pneumoniae DNA. Positive patients were detected of both gender, aged from 9 months to 78 years, who had clinical signs of upper RTI, fever and/or myalgia, an influenza-like illness to lower RTI. Mixed infections were identified in four cases, two with influenza A H1, one with H3 and one with influenza B. Children aged 5-14 years were more likely to have detectable M. pneumoniae in samples than all other age groups (Fishers p = 0.03), attributed to the 2005-2006 season in which 6.0% (12/200, 95%CI 3.4-10.3) of 5-14 year olds had detectable M. pneumoniae in comparison to 2.2% in 2006-2007 (3/141 95%CI 0.5-6.4), 2.2% in 2007-2008 (2/89 95%CI 0.1-8.3) and 0% in 2008-2009 (0/151 95%CI 0-2.9).

External quality assessment for the molecular detection of Hepatitis C virus.

UNLABELLED: BACKGROUND, OBJECTIVES AND STUDY DESIGN: External quality assessment (EQA) panels were distributed internationally by UK NEQAS for Microbiology to 159 participants for the detection, quantification and genotyping of Hepatitis C virus (HCV) in freeze-dried plasma from 2000 to 2004. The results were analysed to determine the level of standardisation of qualitative detection, quantitative detection and genotyping. RESULTS: The accurate detection of HCV in the panels varied from 86.9% to 100%. Four genotypes were distributed with the panels and there was no significant difference in the detection of different genotypes of HCV by participants. Further analysis indicated most variation occurred in quantification of HCV at lower concentrations and from 0% to 14.8% reported quantitative values outside 0.5 log(10) of the median value. In addition, three negative specimens were distributed and false positives were found to be rare (0.9-2.2%) with all methods included in the study. CONCLUSION: The laboratory detection of HCV in plasma EQA specimens was varied, with decreasing parity of quantification at lower concentrations of HCV. False positives and negatives were rare, irrespective of the genotype under test.

Canine mycoplasmas.

This review aims to summarise our current understanding of the role of mycoplasmas in domestic dogs. Canine mycoplasmology is a small field, with less than 50 publications in the past 40 years. In this time we have gained knowledge about the number of species and have made associations with infections in dogs. However much evidence is still lacking. The importance of all canine mycoplasmas remains unknown, yet certain species are associated with canine anaemia (Mycoplasma haemocanis), respiratory disease (Mycoplasma cynos) and urogenital tract infections (Mycoplasma canis). Mycoplasmas can be isolated in pure culture from canine clinical specimens and it is hoped that this review will stimulate veterinarians to consider mycoplasmas as a potential cause of disease in dogs, especially when antibiotic therapy is failing.

External quality assessment for detection of Chlamydia trachomatis.

The use of molecular methods for detection of Chlamydia trachomatis is increasing in clinical laboratories. External quality assessment enables unbiased monitoring of the performance of laboratories in the detection of specific pathogens. This study details the results of molecular and enzyme immunosorbent assay (EIA) testing for C. trachomatis detection in simulated endocervical swab specimens recently distributed internationally by United Kingdom National External Quality Assessment Scheme for Microbiology (UK NEQAS for Microbiology) external quality assessment panels. The frequency of accurate detection of C. trachomatis in the panels ranged from 32 to 100%. Participants using molecular methods were significantly more likely to detect C. trachomatis in specimens than those using an EIA. Two strains were distributed with the panels: an L2 laboratory-adapted strain and an uncharacterized primary isolate. Further analysis indicated a difference in detection of C. trachomatis between specific methods only with the L2 strain at lower concentrations. In addition, eight negative specimens were distributed, and false positives were found to be rare by all methods included in the study.