Prevalence of and risk factors for curable sexually transmitted infections on Bubaque Island, Guinea Bissau.

OBJECTIVES: Complications from sexually transmitted infections (STIs) can result in severe morbidity and mortality. To date, no STI population studies have been conducted on the Bijagos Islands, Guinea Bissau. Our objective was to estimate the prevalence of and identify risk factors for Chlamydia trachomatis (Ct), Neisseria gonorrhoea (Ng), Mycoplasma genitalium (Mg), Trichomonas vaginalis (Tv) and Treponema pallidum (Tp) on Bubaque, the most populated island. METHODS: A cross-sectional survey was conducted on the island of Bubaque among people aged 16-49 years. Participants were asked to answer a questionnaire on STI risk factors, to provide urine samples (men and women) and vaginal swabs (women) for PCR testing for Ct, Ng, Mg and Tv, and to provide dry blood spots for Tp particle agglutination assays. Data were analysed to estimate the prevalence of STIs and logistic regression was used to identify risk factors. RESULTS: In total, 14.9% of participants were found to have a curable STI, with the highest prevalence being observed for Tv (5.9%) followed by Ct (3.8%), Ng (3.8%), Mg (1.9%) and Tp (0.8%). Significant risk factors for having any STI included being female, younger age and concurrent partnership. Having had a previous STI that was optimally treated was a protective factor. CONCLUSIONS: This study demonstrates that there is a considerable burden of STI on the Bijagos Islands, stressing the need for diagnostic testing to facilitate early detection and treatment of these pathogens to stop ongoing transmission. Moreover, these results indicate the need to conduct further research into the STI burden on the Bijagos Islands to help inform and develop a national STI control strategy.

Genomic analyses of the Chlamydia trachomatis core genome show an association between chromosomal genome, plasmid type and disease.

BACKGROUND: Chlamydia trachomatis (Ct) plasmid has been shown to encode genes essential for infection. We evaluated the population structure of Ct using whole-genome sequence data (WGS). In particular, the relationship between the Ct genome, plasmid and disease was investigated. RESULTS: WGS data from 157 Ct isolates deposited in the Chlamydiales pubMLST database ( http://pubMLST.org/chlamydiales/ ) were annotated with 902 genes including the core and accessory genome. Plasmid associated genes were annotated and a plasmid MLST scheme was defined allowing plasmid sequence types to be determined. Plasmid allelic variation was investigated. Phylogenetic relationships were examined using the Genome Comparator tool available in pubMLST. Phylogenetic analyses identified four distinct Ct core genome clusters and six plasmid clusters, with a strong association between the chromosomal genotype and plasmid. This in turn was linked to ompA genovars and disease phenotype. Horizontal genetic transfer of plasmids was observed for three urogenital-associated isolates, which possessed plasmids more commonly found in isolates resulting from ocular infections. The pgp3 gene was identified as the most polymorphic plasmid gene and pgp4 was the most conserved. CONCLUSION: A strong association between chromosomal genome, plasmid type and disease was observed, consistent with previous studies. This suggests co-evolution of the Ct chromosome and their plasmids, but we confirmed that plasmid transfer can occur between isolates. These data provide a better understanding of the genetic diversity occurring across the Ct genome in association with the plasmid content.

Low Prevalence of Urethral Lymphogranuloma Venereum Infections Among Men Who Have Sex With Men: A Prospective Observational Study, Sexually Transmitted Infection Clinic in Amsterdam, the Netherlands.

In contrast to anorectal lymphogranuloma venereum (LGV), few urogenital LGV cases are reported in men who have sex with men. Lymphogranuloma venereum was diagnosed in 0.06% (7/12,174) urine samples, and 0.9% (109/12,174) anorectal samples. Genital-anal transmission seems unlikely the only mode of transmission. Other modes like oral-anal transmission should be considered.

Does typing of Chlamydia trachomatis using housekeeping multilocus sequence typing reveal different sexual networks among heterosexuals and men who have sex with men?

BACKGROUND: Chlamydia trachomatis infections remain the most common bacterial sexually transmitted infection worldwide. To gain more insight into the epidemiology and transmission of C. trachomatis, several schemes of multilocus sequence typing (MLST) have been developed. We investigated the clustering of C. trachomatis strains derived from men who have sex with men (MSM) and heterosexuals using the MLST scheme based on 7 housekeeping genes (MLST-7) adapted for clinical specimens and a high-resolution MLST scheme based on 6 polymorphic genes, including ompA (hr-MLST-6). METHODS: Specimens from 100 C. trachomatis infected men who have sex with men (MSM) and 100 heterosexual women were randomly selected from previous studies and sequenced. We adapted the MLST-7 scheme to a nested assay to be suitable for direct typing of clinical specimens. All selected specimens were typed using both the adapted MLST-7 scheme and the hr-MLST-6 scheme. Clustering of C. trachomatis strains derived from MSM and heterosexuals was assessed using minimum spanning tree analysis. RESULTS: Sufficient chlamydial DNA was present in 188 of the 200 (94 %) selected samples. Using the adapted MLST-7 scheme, full MLST profiles were obtained for 187 of 188 tested specimens resulting in a high success rate of 99.5 %. Of these 187 specimens, 91 (48.7 %) were from MSM and 96 (51.3 %) from heterosexuals. We detected 21 sequence types (STs) using the adapted MLST-7 and 79 STs using the hr-MLST-6 scheme. Minimum spanning tree analyses was used to examine the clustering of MLST-7 data, which showed no reflection of separate transmission in MSM and heterosexual hosts. Moreover, typing using the hr-MLST-6 scheme identified genetically related clusters within each of clusters that were identified by using the MLST-7 scheme. CONCLUSION: No distinct transmission of C. trachomatis could be observed in MSM and heterosexuals using the adapted MLST-7 scheme in contrast to using the hr-MLST-6. In addition, we compared clustering of both MLST schemes and demonstrated that typing using the hr-MLST-6 scheme is able to identify genetically related clusters of C. trachomatis strains within each of the clusters that were identified by using the MLST-7 scheme.

Global Multilocus Sequence Type Analysis of Chlamydia trachomatis Strains from 16 Countries.

The Uppsala University Chlamydia trachomatis multilocus sequence type (MLST) database (http://mlstdb.bmc.uu.se) is based on five target regions (non-housekeeping genes) and the ompA gene. Each target has various numbers of alleles-hctB, 89; CT058, 51; CT144, 30; CT172, 38; and pbpB, 35-derived from 13 studies. Our aims were to perform an overall analysis of all C. trachomatis MLST sequence types (STs) in the database, examine STs with global spread, and evaluate the phylogenetic capability by using the five targets. A total of 415 STs were recognized from 2,089 specimens. The addition of 49 ompA gene variants created 459 profiles. ST variation and their geographical distribution were characterized using eBURST and minimum spanning tree analyses. There were 609 samples from men having sex with men (MSM), with 4 predominating STs detected in this group, comprising 63% of MSM cases. Four other STs predominated among 1,383 heterosexual cases comprising, 31% of this group. The diversity index in ocular trachoma cases was significantly lower than in sexually transmitted chlamydia infections. Predominating STs were identified in 12 available C. trachomatis whole genomes which were compared to 22 C. trachomatis full genomes without predominating STs. No specific gene in the 12 genomes with predominating STs could be linked to successful spread of certain STs. Phylogenetic analysis showed that MLST targets provide a tree similar to trees based on whole-genome analysis. The presented MLST scheme identified C. trachomatis strains with global spread. It provides a tool for epidemiological investigations and is useful for phylogenetic analyses.

High-resolution multilocus sequence typing reveals novel urogenital Chlamydia trachomatis strains in women in Mopani district, South Africa.

OBJECTIVES: Recently, we reported a high prevalence (16%) of urogenital Chlamydia trachomatis infections among women in a rural setting in South Africa. Molecular epidemiological studies on C. trachomatis infections could provide insights into the characteristics of this epidemic, yet such data are not available. The objective of this study was therefore to assess the distribution of C. trachomatis strains among women from a South African rural community, the Mopani district, and to compare it with strains from Amsterdam, the Netherlands. METHODS: High-resolution multilocus sequence typing (hr-MLST) was used to study urogenital C. trachomatis infections in women visiting primary healthcare facilities across rural Mopani District in Limpopo Province, South Africa. Sequence types (STs) were compared with 100 strains from women visiting the sexually transmitted infection clinic in Amsterdam, the Netherlands. RESULTS: Full hr-MLST data were obtained for C. trachomatis infection in 43 women from Mopani district. Using the complete hr-MLST profile of all 43 women from Mopani district, 26 STs could be identified, of which 18 (69%) were novel to the hr-MLST database. The remaining STs clustered together with strains from Amsterdam. CONCLUSIONS: Hr-MLST data revealed a diverse molecular epidemiology with novel STs and a specific cluster for the Mopani district. Also C. trachomatis types that occur worldwide were detected.

Urogenital Chlamydia trachomatis strain types, defined by high-resolution multilocus sequence typing, in relation to ethnicity and urogenital symptoms among a young screening population in Amsterdam, The Netherlands.

INTRODUCTION: Previous studies found conflicting results regarding associations between urogenital Chlamydia trachomatis infections and ethnicity or urogenital symptoms among at-risk populations using either ompA-based genotyping or high-resolution multilocus sequence typing (MLST). This study applied high-resolution MLST on samples of individuals from a selected young urban screening population to assess the relationship of C. trachomatis strain types with ethnicity and self-reported urogenital symptoms. Demographic and sexual risk behaviour characteristics of the identified clusters were also analysed. METHODS: We selected C. trachomatis-positive samples from the Dutch Chlamydia Screening Implementation study among young individuals in Amsterdam, the Netherlands. All samples were typed using high-resolution MLST. Clusters were assigned using minimum spanning tree analysis and were combined with epidemiological data of the participants. RESULTS: We obtained full MLST data for C. trachomatis-positive samples from 439 participants and detected nine ompA genovars. MLST analysis identified 175 sequence types and six large clusters; in one cluster, participants with Surinamese/Antillean ethnicity were over-represented (58.8%) and this cluster predominantly consisted of genovar I. In addition, we found one cluster with an over-representation of participants with Dutch ethnicity (90.0%) and which solely consisted of genovar G. No association was observed between C. trachomatis clusters and urogenital symptoms. CONCLUSIONS: We found an association between urogenital C. trachomatis clusters and ethnicity among young screening participants in Amsterdam, the Netherlands. However, no association was found between C. trachomatis clusters and self-reported urogenital symptoms.

No indication for tissue tropism in urogenital and anorectal Chlamydia trachomatis infections using high-resolution multilocus sequence typing.

BACKGROUND: Previous studies showed that C. trachomatis strains found in MSM are different from those in heterosexuals. This study investigates whether the differences in strain distribution between MSM and heterosexuals are due to tissue tropism. METHODS: C. trachomatis positive samples were collected from MSM (anorectal) and women (anorectal, cervical, vaginal, pharyngeal) visiting the STI outpatient clinic of Amsterdam between 2008 and 2013. All samples were typed using multilocus sequence typing (MLST). Epidemiological data were derived from electronic patient records. RESULTS: We obtained full MLST data for C. trachomatis from 207 MSM and 185 women, all with anorectal infections. Six large clusters were identified of which 3 consisted predominantly of samples from women (89%-100%), whereas the other 3 consisted predominantly of samples from MSM (97%-100%). Furthermore, we obtained full MLST data from 434 samples of 206 women with concurrent infections at multiple anatomical locations. No association was observed between C. trachomatis cluster and the anatomical location of infection. CONCLUSION: We found no indication for tissue tropism in urogenital, pharyngeal and anorectal C. trachomatis infections. Combined with results from previously conducted studies, we hypothesize that MSM and heterosexuals have different distributions of C. trachomatis strains due to their separate sexual networks.

Field- and laboratory-based studies on correlates of Chlamydia trachomatis transmission by Musca sorbens: Determinants of fly-eye contact and investigations into fly carriage of elementary bodies.

Musca sorbens (Diptera: Muscidae) flies are thought to be vectors of the blinding eye disease trachoma, carrying the bacterium Chlamydia trachomatis (Ct) between the eyes of individuals. While their role as vectors has been convincingly demonstrated via randomised controlled trials in The Gambia, studies of fly-borne trachoma transmission remain scant and as such our understanding of their ability to transmit Ct remains poor. We examined fly-eye contact and caught eye-seeking flies from 494 individuals (79% aged ≤9 years) in Oromia, Ethiopia. Ct-carrying flies (harbouring Ct DNA) were found to cluster spatially in and nearby to households in which at least one resident had Ct infection. Fly-eye contact was positively associated with the presence of trachoma (disease), lower human body weight and increased human body temperature. Studies of laboratory-reared M. sorbens indicated that Ct is found both externally and internally following feeds on Ct culture, with scanning electron microscopy revealing how Ct bodies can cling to fly hairs (setae). Testing for Ct on field-caught M. sorbens found fly 'bodies' (thorax, wings and abdomen) to consistently test positive for Ct while legs and heads were infrequently Ct-positive. These studies strongly support the role of M. sorbens as vectors of trachoma and highlight the need for improved understanding of fly-borne trachoma transmission dynamics and vector competence.

Short communication: prevalence of antibodies against Coxiella burnetii (Q fever) in children in The Gambia, West Africa.

OBJECTIVE: To estimate the prevalence of antibodies against Coxiella burnetii (Q fever) among children in eight villages in The Gambia, West Africa. METHODS: Sera of 796 children aged 1-15 years were tested for presence of antibodies against phase II of C. burnetii by ELISA. RESULTS: IgG and/or IgM phase II antibodies against C. burnetii were detectable in 8.3% (66/796) of all serum samples analysed with significant differences in seroprevalence between villages. Highest prevalence was found in the age group 1-4 years. CONCLUSIONS: Exposure to C. burnetii is considerable in the early years of life in The Gambia, and further studies are warranted to estimate the role of Q fever in acute febrile illness in The Gambia and elsewhere in Africa.

Trachoma risk factors in Oromia Region, Ethiopia.

BACKGROUND: Trachoma, the leading infectious cause of blindness, is caused by the bacterium Chlamydia trachomatis (Ct). Despite enormous disease control efforts and encouraging progress, trachoma remains a significant public health problem in 44 countries. Ethiopia has the greatest burden of trachoma worldwide, however, robust data exploring transmission risk factors and the association between socio-economic status is lacking from some regions. This is the first study to investigate these factors in this South-Eastern region of Oromia, Ethiopia. METHODOLOGY/PRINCIPAL FINDINGS: A total of 1211 individuals were enrolled from 247 households in Shashemene Rural district in Oromia Region between 11th April and 25th June 2018, of whom 628 (51.9%) were female and 526 (43.4%) were children aged 1-9 years. Three standardised ophthalmic nurses examined each participant for the presence of active trachoma using the WHO simplified trachoma grading system. Conjunctival swab samples were collected from the upper tarsal conjunctiva of the left eye of each participant. Ct was detected using quantitative PCR. Risk factor data were collected through structured interviews and direct observations. Clinical signs of trachomatous inflammation-follicular among children aged 1-9 (TF1-9) were observed in at least one eye of 106/526 (20.2%) and trachomatous inflammation-intense among children aged 1-9 (TI1-9) were observed in at least one eye of 10/526 (1.9%). We detected Ct by PCR in 23 individuals, of whom 18 (78.3%) were in children aged 1-9 years. Among the 106 children aged 1-9 years with TF, 12 (11.3%) were Ct PCR positive and among 20 children aged 1-9 years with TI, 4 (20.0%) were Ct PCR positive. In a multivariable model, adjusting for household clustering, active trachoma was associated with younger age, the poorest households (aOR = 2.56, 95% CI 1.21-5.51), presence of flies on the face (aOR = 2.87, 95% CI 1.69-6.46), and ocular discharge (aOR = 1.89, 95% CI 1.03-3.24). Pre-school children face washing more than once a day had lower odds of having active trachoma (aOR = 0.59, 95% CI 0.19-0.84). The same was true for washing children's clothing at least once per week (aOR = 0.27, 95% CI 0.33-1.02). CONCLUSION/SIGNIFICANCE: Younger age, personal hygiene in this age group (presence of ocular and nasal discharges, infrequent washing of faces and clothing) and fly-eye contacts are potential risk factors for trachoma in this setting, suggesting that hygiene interventions and environmental improvements are required to suppress transmission to ensure sustained reduction in disease burden Further studies are needed to evaluate these interventions for trachoma control and elimination. Trachoma remains a disease associated with lower socio-economic status, emphasising the need for continued implementation of control measures in addition to poverty reduction interventions in this region.

Follow-up of 686 patients with acute Q fever and detection of chronic infection.

BACKGROUND: Recent outbreaks in the Netherlands allowed for laboratory follow-up of a large series of patients with acute Q fever and for evaluation of test algorithms to detect chronic Q fever, a condition with considerable morbidity and mortality. METHODS: For 686 patients with acute Q fever, IgG antibodies to Coxiella burnetii were determined using an immunofluorescence assay at 3, 6, and 12 months of follow-up. Polymerase chain reaction (PCR) was performed after 12 months and on earlier serum samples with an IgG phase I antibody titer ≥ 1:1024. RESULTS: In 43% of patients, the IgG phase II antibody titers remained high (≥ 1:1024) at 3, 6, and 12 months of follow-up. Three months after acute Q fever, 14% of the patients had an IgG phase I titer ≥ 1:1024, which became negative later in 81%. IgG phase I antibody titers were rarely higher than phase II titers. Eleven cases of chronic Q fever were identified on the basis of serological profile, PCR results, and clinical presentation. Six of these patients were known to have clinical risk factors at the time of acute Q fever. In a comparison of various serological algorithms, IgG phase I titer ≥ 1:1024 at 6 months had the most favorable sensitivity and positive predictive value for the detection of chronic Q fever. CONCLUSIONS: The wide variation of serological and PCR results during the follow-up of acute Q fever implies that the diagnosis of chronic Q fever, necessitating long-term antibiotic treatment, must be based primarily on clinical grounds. Different serological follow-up strategies are needed for patients with and without known risk factors for chronic Q fever.

Ongoing evolution of Chlamydia trachomatis lymphogranuloma venereum: exploring the genomic diversity of circulating strains.

Lymphogranuloma venereum (LGV), the invasive infection of the sexually transmissible infection (STI) Chlamydia trachomatis, is caused by strains from the LGV biovar, most commonly represented by ompA-genotypes L2b and L2. We investigated the diversity in LGV samples across an international collection over seven years using typing and genome sequencing. LGV-positive samples (n=321) from eight countries collected between 2011 and 2017 (Spain n=97, Netherlands n=67, Switzerland n=64, Australia n=53, Sweden n=37, Hungary n=31, Czechia n=30, Slovenia n=10) were genotyped for pmpH and ompA variants. All were found to contain the 9 bp insertion in the pmpH gene, previously associated with ompA-genotype L2b. However, analysis of the ompA gene shows ompA-genotype L2b (n=83), ompA-genotype L2 (n=180) and several variants of these (n=52; 12 variant types), as well as other/mixed ompA-genotypes (n=6). To elucidate the genomic diversity, whole genome sequencing (WGS) was performed from selected samples using SureSelect target enrichment, resulting in 42 genomes, covering a diversity of ompA-genotypes and representing most of the countries sampled. A phylogeny of these data clearly shows that these ompA-genotypes derive from an ompA-genotype L2b ancestor, carrying up to eight SNPs per isolate. SNPs within ompA are overrepresented among genomic changes in these samples, each of which results in an amino acid change in the variable domains of OmpA (major outer membrane protein, MOMP). A reversion to ompA-genotype L2 with the L2b genomic backbone is commonly seen. The wide diversity of ompA-genotypes found in these recent LGV samples indicates that this gene is under immunological selection. Our results suggest that the ompA-genotype L2b genomic backbone is the dominant strain circulating and evolving particularly in men who have sex with men (MSM) populations.

Viability PCR shows that non-ocular surfaces could contribute to transmission of Chlamydia trachomatis infection in trachoma.

BACKGROUND: The presence of Chlamydia trachomatis (Ct) DNA at non-ocular sites suggests that these sites may represent plausible routes of Ct transmission in trachoma. However, qPCR cannot discriminate between DNA from viable and non-viable bacteria. Here we use a propodium monoazide based viability PCR to investigate how long Ct remains viable at non-ocular sites under laboratory-controlled conditions. METHODS: Cultured Ct stocks (strain A2497) were diluted to final concentrations of 1000, 100, 10 and 1 omcB copies/µL and applied to plastic, woven mat, cotton cloth and pig skin. Swabs were then systemically collected from each surface and tested for the presence Ct DNA using qPCR. If Ct DNA was recovered, Ct viability was assessed over time by spiking multiple areas of the same surface type with the same final concentrations. Swabs were collected from each surface at 0, 2, 4, 6, 8 and 24 hours after spiking. Viability PCR was used to determine Ct viability at each timepoint. RESULTS: We were able to detect Ct DNA on all surfaces except the woven mat. Total Ct DNA remained detectable and stable over 24 hours for all concentrations applied to plastic, pig skin and cotton cloth. The amount of viable Ct decreased over time. For plastic and skin surfaces, only those where concentrations of 100 or 1000 omcB copies/µL were applied still had viable loads detectable after 24 hours. Cotton cloth showed a more rapid decrease and only those where concentrations of 1000 omcB copies/µL were applied still had viable DNA detectable after 24 hours. CONCLUSION: Plastic, cotton cloth and skin may contribute to transmission of the Ct strains that cause trachoma, by acting as sites where reservoirs of bacteria are deposited and later collected and transferred mechanically into previously uninfected eyes.

Detecting extra-ocular Chlamydia trachomatis in a trachoma-endemic community in Ethiopia: Identifying potential routes of transmission.

BACKGROUND: Trachoma elimination efforts are hampered by limited understanding of Chlamydia trachomatis (Ct) transmission routes. Here we aimed to detect Ct DNA at non-ocular sites and on eye-seeking flies. METHODS: A population-based household survey was conducted in Oromia Region, Ethiopia. Ocular and non-ocular (faces, hands, clothing, water containers and sleeping surfaces) swabs were collected from all individuals. Flies were caught from faces of children. Flies, ocular swabs and non-ocular swabs were tested for Ct by quantitative PCR. RESULTS: In total, 1220 individuals in 247 households were assessed. Active trachoma (trachomatous inflammation-follicular) and ocular Ct were detected in 10% and 2% of all-ages, and 21% and 3% of 1-9-year-olds, respectively. Ct was detected in 12% (95% CI:8-15%) of tested non-ocular swabs from ocular-positive households, but in none of the non-ocular swabs from ocular-negative households. Ct was detected on 24% (95% CI:18-32%) of flies from ocular-positive households and 3% (95% CI:1-6%) of flies from ocular-negative households. CONCLUSION: Ct DNA was detected on hands, faces and clothing of individuals living in ocular-positive households suggesting that this might be a route of transmission within Ct infected households. In addition, we detected Ct on flies from ocular-positive households and occasionally in ocular-negative households suggesting that flies might be a vector for transmission within and between Ct infected and uninfected households. These potential transmission routes may need to be simultaneously addressed to suppress transmission.

An Organotypic Reconstructed Human Urethra to Study Chlamydia trachomatis Infection.

Organotypic models to investigate host-microbiome interactions are still a challenge for the field of tissue engineering. This is particularly the case for organs such as the urethra. Several cell line, animal, and tissue models are available to study Chlamydia trachomatis infections, but none fully reflects natural infection in native human tissue. Therefore, we developed an organotypic reconstructed human urethral model (RhU) to study invasive and noninvasive strains of C. trachomatis. Primary urethra cells were used to reconstruct epithelium on a fibroblast populated collagen-fibrin hydrogel, yielding a RhU. Immunohistochemistry was used to compare RhU with native urethral tissue and to visualize the location of C. trachomatis bacteria in RhU after 10-day exposure. RhU closely resembled native urethral tissue with respect to proliferation and differentiation markers (keratins 6, 10, 13, 17, involucrin, SKALP [skin-derived antileucoproteinase], vimentin, and CD31). Exposure of RhU to noninvasive and invasive C. trachomatis strains revealed relevant differences in infection ability because inclusions were observed (indicating active infection) in the epithelial layer after 10 days exposure only to the invasive strain. The noninvasive strain remained localized on the surface of the epithelial layer. Human primary urethral fibroblasts and keratinocytes can be used to construct RhU that closely resembles native tissue and can be used to investigate active C. trachomatis infections. RhU provides a promising model to investigate host-microbiome interactions such as, but not limited to, the human pathogenesis of C. trachomatis.

Monitoring therapy success of urogenital Chlamydia trachomatis infections in women: A prospective observational cohort study.

INTRODUCTION: The use of a nucleic acid amplification test (NAAT) as a test of cure after treatment is subject to discussion, as the presence of C. trachomatis nucleic acids after treatment may be prolonged and intermittent without presence of infectious bacteria. We used cell culture to assess if a positive RNA- or DNA-based NAAT after treatment indicates the presence of viable C. trachomatis. METHODS: We included women with asymptomatic urogenital C. trachomatis infection visiting the Amsterdam STI clinic from September 2015 through June 2016. Endocervical swabs were collected prior to treatment with azithromycin, and during three follow-up visits 7, 21 and 49 days after treatment. Collected swabs were subjected to C. trachomatis culture and a RNA- and DNA-based NAAT. High-resolution multilocus sequence typing (hr-MLST) was used to further differentiate potential re-infections. RESULTS: We included 90 women with a positive RNA-test prior to receiving treatment of whom 81 (90%) were also DNA-positive, and 69 (76.7%) culture-positive. Prolonged and intermittent positive RNA and DNA results over time were observed. Three women had culture positive results at the second visit, but all were negative at the third visit. Five women had NAAT-positive results at the fourth visit of whom three women were also culture-positive indicating a viable infection. All five women reported unprotected sexual contact since the first visit. From 2, hr-MLST sequence types were obtained. One had a different sequence type indicating a new infection the other was identical to the previously found indicating a potentially persisting infection. CONCLUSION: Most RNA- or DNA-positive results after treatment of urogenital C. trachomatis may be caused by non-viable molecular remnants since they cannot be confirmed by culture. In a minority viable C. trachomatis was found in culture at the second visit, indicating that patients may remain infectious at least 7 days after treatment.

Risk factors of Coxiella burnetii (Q fever) seropositivity in veterinary medicine students.

BACKGROUND: Q fever is an occupational risk for veterinarians, however little is known about the risk for veterinary medicine students. This study aimed to assess the seroprevalence of Coxiella burnetii among veterinary medicine students and to identify associated risk factors. METHODS: A cross-sectional study with questionnaire and blood sample collection was performed among all veterinary medicine students studying in The Netherlands in 2006. Serum samples (n = 674), representative of all study years and study directions, were analyzed for C. burnetii IgG and IgM phase I and II antibodies with an immunofluorescence assay (IFA). Seropositivity was defined as IgG phase I and/or II titer of 1:32 and above. RESULTS: Of the veterinary medicine students 126 (18.7%) had IgG antibodies against C. burnetii. Seropositivity associated risk factors identified were the study direction 'farm animals' (Odds Ratio (OR) 3.27 [95% CI 2.14-5.02]), advanced year of study (OR year 6: 2.31 [1.22-4.39] OR year 3-5 1.83 [1.07-3.10]) having had a zoonosis during the study (OR 1.74 [1.07-2.82]) and ever lived on a ruminant farm (OR 2.73 [1.59-4.67]). Stratified analysis revealed study direction 'farm animals' to be a study-related risk factor apart from ever living on a farm. In addition we identified a clear dose-response relation for the number of years lived on a farm with C. burnetii seropositivity. CONCLUSIONS: C. burnetii seroprevalence is considerable among veterinary medicine students and study related risk factors were identified. This indicates Q fever as an occupational risk for veterinary medicine students.