Multiple-locus variable-number tandem repeat analysis of Neisseria gonorrhoeae

Development of multiplex HRM-based loop-mediated isothermal amplification method for specific and sensitive detection of Treponema pallidum

Syphilis is a sexually transmitted disease caused by the spirochaete bacterium Treponema pallidum. This study has developed a multiplex High-Resolution Melt-curve Loop-mediated isothermal amplification (multiplex HRM-LAMP) assay targeting the marker genes polA and tprL to detect T. pallidum. The multiplex HRM-LAMP assay conditions were optimized at 65 °C for 45 min. Real-time melt-curve analysis of multiplex HRM-LAMP shows two melt-curve peaks corresponding to polA and tprL with a Tm value of 80 ± 0.5 °C and 87 ± 0.5 °C, respectively. The detection limit of multiplex HRM-LAMP was found to be 6.4 × 10^-4 ng/μL (3.79 copies/μL) of T. pallidum. The specificity was evaluated using seven different bacterial species, and the developed method was 100% specific in detecting T. pallidum. A total of 64 blood samples of T. pallidum suspected cases were used to validate the assay method. The clinical validation showed that the assay was 96.43% sensitive and 100% specific in detecting syphilis. Thus, the developed method was more rapid and sensitive than other available methods and provides a multigene-based diagnostic approach to detect T. pallidum.

Ceftriaxone Reduced Susceptible Neisseria gonorrhoeae in the Netherlands, 2009 to 2017: From PenA Mosaicism to A501T/V Nonmosaicism

OBJECTIVES

To compare molecular and epidemiological differences between ceftriaxone-reduced susceptible (CRO-RS) and ceftriaxone-susceptible (CRO-S) N. gonorrhoeae (Ng) and to study the genetic relatedness of CRO-RS isolates.

METHODS

Demographic and clinical data and samples for cultures were routinely collected from gonorrhoea patients visiting the Amsterdam STI clinic in 2009 to 2017. Ng multiantigen sequence typing (NG-MAST) and penA types were compared between CRO-RS and CRO-S Ng (frequency matched on year of isolation and sexual risk group). Minimum spanning trees were produced based on multilocus variable number of tandem repeats analysis for Ng (NG-MLVA) genotypes.

RESULTS

We selected 174 CRO-RS isolates (minimum inhibitory concentration, ≥0.064 mg/L) and 174 CRO-S isolates (minimum inhibitory concentration, ≤0.016 mg/L). Demographic and clinical characteristics of patients were overall comparable between those infected with CRO-RS Ng and CRO-S Ng. However, CRO-RS isolates were more often collected from the pharyngeal site (odds ratios [OR], 3.64; P < 0.001), and patients with CRO-RS Ng were less often human immunodeficiency virus (HIV) and syphilis positive (OR, 0.63; P = 0.041 and OR, 0.58; P = 0.028, respectively). We identified 12 clusters based on NG-MLVA genotypes, including 3 large (>25 isolates) clusters predominantly containing CRO-RS isolates. Those from cluster 1 (n = 32) were mostly from 2009 to 2012 (n = 24; 75.0%), with a mosaic penA XXXIV pattern (n = 27; 84.4%) and belonging to NG-MAST genogroup G1407 (n = 24; 75.0%). Isolates from cluster 2 (n = 29) were mostly from 2013 to 2015 (n = 24; 82.7%), had a nonmosaic penA IX + A501T mutation (n = 22; 75.9%) and NG-MAST G2400 (n = 14; 48.3%). Most isolates from cluster 3 (n = 37) were from 2015 to 2017 (n = 26; 70.2%), had a nonmosaic penA IV + A501V mutation (n = 24; 64.9%) and NG-MAST G2318 (n = 22; 59.5%).

CONCLUSIONS

We observed a shift in the predominant penA (from mosaic toward nonmosaic plus A501T/V mutation), NG-MAST and NG-MLVA types among CRO-RS Ng over time. This indicates a successive spread of different CRO-RS Ng clones.

Molecular epidemiology of Neisseria gonorrhoeae strains circulating in Indonesia using multi-locus variable number tandem repeat analysis (MLVA) and Neisseria gonorrhoeae multi-antigen sequence typing (NG-MAST) techniques

BACKGROUND

Control of gonorrhea in resource-limited countries, such as Indonesia, is mostly unsuccessful. Examining Neisseria gonorrhoeae (Ng) transmission networks using strain typing might help prioritizing public health interventions.

METHODS

In 2014, urogenital Ng strains were isolated from clients of sexually transmitted infection clinics in three Indonesian cities. Strains were typed using Multiple-Locus Variable Number Tandem Repeat (VNTR) Analysis (MLVA) and Ng Multi-Antigen Sequence Typing (NG-MAST) at the Public Health Service, Amsterdam, the Netherlands, and compared to Dutch strains collected from 2012 to 2015. Minimum spanning trees (MSTs) were constructed using MLVA profiles incorporating demographics and NG-MAST genogroups. A cluster was defined as ≥5 strains differing in ≤1 VNTR locus. The concordance between MLVA and NG-MAST was examined with the adjusted Wallace coefficients (AW).

RESULTS

We collected a total of 78 Indonesian strains from Yogyakarta (n = 44), Jakarta (n = 25), and Denpasar (n = 9). Seven MLVA clusters and 16 non-clustered strains were identified. No cluster was specific for any geographic area, risk group or age group. Combined with 119 contemporary Dutch strains, 8 MLVA clusters were identified, being four clusters of Indonesian strains, two of Dutch strains, and two of both Indonesian and Dutch strains. Indonesian strains (79.5%) were more often clustered compared to Dutch strains (24.3%). The most prevalent NG-MAST genogroups among Indonesian strains was G1407 (51.3%) and among Dutch strains was G2992 (19.3%). In Indonesian strains, the AW [95% confidence interval] for MLVA to NG-MAST was 0.07 [0.00-0.27] and for NG-MAST to MLVA was 0.03 [0.00-0.12].

CONCLUSION

Indonesian Ng strains are more often clustered than Dutch strains, but show no relation with geographical area, risk group, or age group, suggesting a more clonal Ng epidemic in Indonesia. Some similar Ng strains circulate in both Indonesia and the Netherlands.

Antimicrobial Susceptibility Evaluation and Multiple-Locus Variable Number Tandem Repeat Analysis of Neisseria gonorrhoeae Isolates in China in 2012

OBJECTIVE

This study aimed to gain information on the antimicrobial susceptibility and molecular epidemiological typing of Neisseria gonorrhoeae (NG) isolates in China in 2012.

METHODS

A total of 244 NG isolates were consecutively recovered from patients with uncomplicated gonorrhea attending sexually transmitted disease clinics in 3 Chinese cities-Guangzhou, Nanjing, and Tianjin-in 2012. Neisseria gonorrhoeae susceptibilities to penicillin and tetracycline were examined by detecting penicillinase-producing NG (PPNG) and high-level tetracycline-resistant NG, and NG susceptibilities to ciprofloxacin, spectinomycin, ceftriaxone, and cefixime were determined using an agar dilution method. Neisseria gonorrhoeae isolates were typed by multiple-locus variable number tandem repeat analysis. We conducted a χ analysis to compare clusters with Bonferroni correction and Kruskal-Wallis test.

RESULTS

Neisseria gonorrhoeae isolates gathered from the 3 cities differed significantly in the prevalence of tetracycline-resistant NG (P < 0.001) and NG treated with ceftriaxone with a minimum inhibitory concentration of 0.125 mg/L or higher (P < 0.001). The analysis of the combination of the 7 variable number of tandem repeats loci for all of the 244 isolates yielded 110 multiple-locus variable number tandem repeat analysis types falling into 5 clusters. Cluster III was associated with PPNG, whereas cluster II was associated with non-PPNG (P < 0.05) and NG treated with ceftriaxone with a minimum inhibitory concentration of 0.125 mg/L or higher (P < 0.05).

CONCLUSIONS

Antimicrobials that can be used with confidence to treat NG infection currently in China include ceftriaxone and spectinomycin, but not penicillin, tetracycline, ciprofloxacin, and cefixime. Moreover, some of the resulting clusters were associated with PPNG and NG with decreased ceftriaxone susceptibility.

Gonorrhea in Indonesia: High Prevalence of Asymptomatic Urogenital Gonorrhea but No Circulating Extended Spectrum Cephalosporins-Resistant Neisseria gonorrhoeae Strains in Jakarta, Yogyakarta, and Denpasar, Indonesia

BACKGROUND

Little is known about the epidemiology of asymptomatic urogenital gonorrhea and antimicrobial susceptibility of Neisseria gonorrhoeae (NG) strains circulating in Indonesia. We studied these issues in 3 large Indonesian cities.

METHODS

In 2014, participants were recruited from sexually transmitted infection clinics and through outreach in Jakarta, Yogyakarta, and Denpasar. Neisseria gonorrhoeae detection in genital specimens was performed with NG-qPCR at the Public Health Service in Amsterdam. Antimicrobial susceptibility was investigated using the Etest.

RESULTS

Among 992 participants, 781 were asymptomatic and included in the risk factors analysis: 439 (56.2%) men, 258 (33.0%) women, and 84 (10.8%) transwomen. They differed significantly in age and were mostly men who have sex with men (35.2%) and female sex workers (29.3%).Overall, 175 (22.4%) asymptomatic participants had a positive NG-qPCR result. Factors positively associated with asymptomatic urogenital gonorrhea were being recruited through outreach (vs clinic-based), inconsistent condom use, and being divorced/widowed (vs single).Among 79 urogenital cultured isolates derived from 27 symptomatic and 52 asymptomatic participants, all isolates were susceptible to ceftriaxone and cefixime, and 98.7% of isolates were susceptible to azithromycin. In contrast, resistance to doxycycline (98.7%) and ciprofloxacin (97.4%) was common.

CONCLUSIONS

Prevalence of asymptomatic urogenital gonorrhea among Indonesian key populations is very high. Little to no resistance against extended spectrum cephalosporins and azithromycin was observed. However, almost all isolates were resistant to doxycycline and ciprofloxacin. Strengthening outreach sexually transmitted infections services, composing guidelines to screen asymptomatic individuals, and implementing periodical antimicrobial resistance surveillance are recommended.

Value of light microscopy to diagnose urogenital gonorrhoea: a diagnostic test study in Indonesian clinic-based and outreach sexually transmitted infections services

INTRODUCTION

Gonorrhoea is a common sexually transmitted disease caused by Neisseria gonorrhoeae (Ng) infection. Light microscopy of urogenital smears is used as a simple tool to diagnose urogenital gonorrhoea in many resource-limited settings. We aimed to evaluate the accuracy of light microscopy to diagnose urogenital gonorrhoea as compared with a PCR-based test.

METHODS

In 2014, we examined 632 male urethral and 360 endocervical smears in clinic-based and outreach settings in Jakarta, Yogyakarta and Denpasar, Indonesia. Using the detection of Ng DNA by a validated PCR as reference test, we evaluated the accuracy of two light microscopic criteria to diagnose urogenital gonorrhoea in genital smears: (1) the presence of intracellular Gram-negative diplococci (IGND) and (2) ≥5 polymorphonuclear leucocytes (PMNL)/oil-immersion field (oif) in urethral or ≥20 PMNL/oif in endocervical smears.

RESULTS

In male urethral smears, IGND testing had a sensitivity (95% CI), specificity (95% CI) and kappa±SE of 59.0% (50.1 to 67.4), 89.4% (86.3 to 91.9) and 0.49±0.04, respectively. For PMNL count, these were 59.0% (50.1 to 67.4), 83.7% (80.2 to 86.9) and 0.40±0.04, respectively. The accuracy of IGND in the clinic-based settings (72.0% (57.5 to 83.3), 95.2% (91.8 to 97.5) and 0.68±0.06, respectively) was better than in the outreach settings (51.2% (40.0 to 62.3), 83.4% (78.2 to 87.8) and 0.35±0.06, respectively). In endocervical smears, light microscopy performed poorly regardless of the setting or symptomatology, with kappas ranging from -0.09 to 0.24.

CONCLUSION

Light microscopy using IGND and PMNL criteria can be an option with moderate accuracy to diagnose urethral gonorrhoea among males in a clinic-based setting. The poor accuracy in detecting endocervical infections indicates an urgent need to implement advanced methods, such as PCR. Further investigations are needed to identify the poor diagnostic outcome in outreach services.

A Case-Control Study of Molecular Epidemiology in Relation to Azithromycin Resistance in Neisseria gonorrhoeae Isolates Collected in Amsterdam, the Netherlands, between 2008 and 2015

Neisseria gonorrhoeae resistance to ceftriaxone and azithromycin is increasing, which threatens the recommended dual therapy. We used molecular epidemiology to identify N. gonorrhoeae clusters and associations with azithromycin resistance in Amsterdam, the Netherlands. N. gonorrhoeae isolates (n = 143) were selected from patients visiting the Amsterdam STI Outpatient Clinic from January 2008 through September 2015. We included all 69 azithromycin-resistant isolates (MIC ≥ 2.0 mg/liter) and 74 frequency-matched susceptible controls (MIC ≤ 0.25 mg/liter). The methods used were 23S rRNA and mtrR sequencing, N. gonorrhoeae multiantigen sequence typing (NG-MAST), N. gonorrhoeae multilocus variable-number tandem-repeat analysis (NG-MLVA), and a specific PCR to detect mosaic penA genes. A hierarchical cluster analysis of NG-MLVA related to resistance and epidemiological characteristics was performed. Azithromycin-resistant isolates had C2611T mutations in 23S rRNA (n = 62, 89.9%, P < 0.001) and were NG-MAST genogroup G2992 (P < 0.001), G5108 (P < 0.001), or G359 (P = 0.02) significantly more often than susceptible isolates and were more often part of NG-MLVA clusters (P < 0.001). Two resistant isolates (2.9%) had A2059G mutations, and five (7.3%) had wild-type 23S rRNA. No association between mtrR mutations and azithromycin resistance was found. Twenty-four isolates, including 10 azithromycin-resistant isolates, showed reduced susceptibility to extended-spectrum cephalosporins. Of these, five contained a penA mosaic gene. Four of the five NG-MLVA clusters contained resistant and susceptible isolates. Two clusters consisting mainly of resistant isolates included strains from men who have sex with men and from heterosexual males and females. The co-occurrence of resistant and susceptible strains in NG-MLVA clusters and the frequent occurrence of resistant strains outside of clusters suggest that azithromycin resistance develops independently from the background genome.

Sexually transmitted infections in men who have sex with men

Homosexuality is a global human phenomenon. Although the American Psychiatric Association removed homosexuality from its list of disorders more than 35years ago, homophobia among physicians is still widely prevalent. Men who have sex with men (MSM) form a relatively new epidemiological risk group for STI. To perform correct management, clinicians evaluating men with male-male sex contacts for STI related complaints or STI screening must obtain a thorough sexual history. Emerging STI like lymphogranuloma venereum, hepatitis C, and multidrug resistant N. gonorrhea strains have been described first in MSM. STI related proctitis often occur in MSM. Within the MSM population, HIV positive patients form a special group affected by STI related diseases, such as anal carcinoma and neurosyphilis. The final part of this review concludes with recommendations to reduce the STI burden in MSM.

Treatment failure with 2 g of azithromycin (extended-release formulation) in gonorrhoea in Japan caused by the international multidrug-resistant ST1407 strain of Neisseria gonorrhoeae

OBJECTIVES

Antimicrobial resistance in Neisseria gonorrhoeae is a major public health concern globally. We report the first verified treatment failure of gonorrhoea with 2 g of azithromycin (extended-release formulation) in Japan and characteristics of the corresponding N. gonorrhoeae isolates.

METHODS

Pre- and post-treatment isolates (n = 4) were investigated by Etest for antimicrobial susceptibility. The isolates were examined for molecular epidemiology by multilocus sequence typing (MLST), N. gonorrhoeae multi-antigen sequence typing (NG-MAST) and multiple-locus variable-number tandem repeat analysis (MLVA), and for the presence of azithromycin resistance determinants (23S rRNA gene mutations, erm genes and mtrR mutations).

RESULTS

All isolates were resistant to azithromycin (MIC 4 mg/L) and ciprofloxacin, but remained susceptible to cefixime, ceftriaxone and spectinomycin. All isolates were assigned to MLST ST1901 and NG-MAST ST1407 and three of four isolates possessed MLVA profile 8-3-21-16-1. All isolates contained the previously described C2599T mutation (N. gonorrhoeae numbering) in all four 23S rRNA alleles and the previously described single-nucleotide (A) deletion in the mtrR promoter region.

CONCLUSIONS

This verified treatment failure occurred in a patient infected with an MLST ST1901/NG-MAST ST1407 strain of N. gonorrhoeae. While this international strain commonly shows resistance or decreased susceptibility to multiple antimicrobials, including extended-spectrum cephalosporins, the strain reported here remained fully susceptible to the latter antimicrobials. Hence, two subtypes of azithromycin-resistant gonococcal MLST ST1901/NG-MAST ST1407 appear to have evolved and to be circulating in Japan. Azithromycin should not be recommended as a single antimicrobial for first-line empirical treatment of gonorrhoea.

Multilocus variable-number-tandem-repeats analysis (MLVA) distinguishes a clonal complex of Clavibacter michiganensis subsp. michiganensis strains isolated from recent outbreaks of bacterial wilt and canker in Belgium

BACKGROUND

Clavibacter michiganensis subsp. michiganensis (Cmm) causes bacterial wilt and canker in tomato. Cmm is present nearly in all European countries. During the last three years several local outbreaks were detected in Belgium. The lack of a convenient high-resolution strain-typing method has hampered the study of the routes of transmission of Cmm and epidemiology in tomato cultivation. In this study the genetic relatedness among a worldwide collection of Cmm strains and their relatives was approached by gyrB and dnaA gene sequencing. Further, we developed and applied a multilocus variable number of tandem repeats analysis (MLVA) scheme to discriminate among Cmm strains.

RESULTS

A phylogenetic analysis of gyrB and dnaA gene sequences of 56 Cmm strains demonstrated that Belgian Cmm strains from recent outbreaks of 2010-2012 form a genetically uniform group within the Cmm clade, and Cmm is phylogenetically distinct from other Clavibacter subspecies and from non-pathogenic Clavibacter-like strains. MLVA conducted with eight minisatellite loci detected 25 haplotypes within Cmm. All strains from Belgian outbreaks, isolated between 2010 and 2012, together with two French strains from 2010 seem to form one monomorphic group. Regardless of the isolation year, location or tomato cultivar, Belgian strains from recent outbreaks belonged to the same haplotype. On the contrary, strains from diverse geographical locations or isolated over longer periods of time formed mostly singletons.

CONCLUSIONS

We hypothesise that the introduction might have originated from one lot of seeds or contaminated tomato seedlings that was the source of the outbreak in 2010 and that these Cmm strains persisted and induced infection in 2011 and 2012. Our results demonstrate that MLVA is a promising typing technique for a local surveillance and outbreaks investigation in epidemiological studies of Cmm.

Multiple-locus variable number tandem repeat analysis of Neisseria gonorrhoeae isolates in Russia

In the present study, a multiple-locus variable number tandem repeat analysis (MLVA) was used to assess the molecular epidemiology of Neisseria gonorrhoeae clinical isolates originating from different regions of Russia. MLVA, based on seven loci, was performed on 218 isolates that were previously tested for susceptibility to penicillin, tetracycline and ciprofloxacin and for the presence of certain genetic determinants of drug resistance. In total, 83 MLVA types were identified, indicating that MLVA is a highly discriminatory technique with a Hunter-Gaston discriminatory index of 0.963 (95% CI, 0.950-0.977). MLVA type 16 was shown to be the most prevalent type and is undoubtedly associated with a multidrug resistant phenotype. The spread of MLVA type 16 from Moscow to Irkutsk suggests that this type has a highly successful transmission rate. Hierarchical cluster analysis of the MLVA profiles classified 208 isolates (95%) into six large groups (containing more than 10 isolates). Clusters differed in geographical characteristics and susceptibility profiles. MLVA cluster A comprised in total 34 isolates and was unambiguously associated with multidrug resistance. Most isolates in cluster A carried mutations in penA, ponA, rpsJ, mtrR, gyrA, and parC genes. MLVA cluster D was associated with resistance to penicillin and with mutations in ponA and rpsJ genes and the presence of plasmid-borne bla(TEM-1) gene. MLVA clusters B, C and E were associated with susceptibility to ciprofloxacin and had a lack of mutations in ponA, rpsJ, gyrA, and parC genes. We conclude that MLVA will be a useful tool for N. gonorrhoeae epidemiological studies.

Distinct Neisseria gonorrhoeae transmission networks among men who have sex with men in Amsterdam, The Netherlands

BACKGROUND

Molecular typing was used to elucidate Neisseria gonorrhoeae transmission networks among men who have sex with men (MSM) in Amsterdam, the Netherlands. We determined whether clusters of patients infected with specific N. gonorrhoeae genotypes were related to various epidemiological characteristics.

METHODS

MSM (age ≥18 years) visiting the sexually transmitted infections (STI) clinic between July 2008 and August 2009 were eligible. After STI screening, participants completed a behavioral questionnaire concerning the previous 6 months. N. gonorrhoeae cultures were genotyped using multiple-locus variable-number tandem repeat analysis typing.

RESULTS

We obtained 278 N. gonorrhoeae-positive isolates from 240 MSM. Five large clusters (≥10 isolates), a unique sixth cluster (n = 9), and 8 smaller clusters (5-9 isolates) were identified. Prevalence of human immunodeficiency virus differed between clusters I and VI (P = .003), ranging from 27.8% to 100%. Receptive unprotected anal intercourse was frequently reported by MSM (51.8%) but did not differ significantly among clusters. Significant differences were identified concerning the participant's history of syphilis (P = .030), having met partners at a popular sex venue in Amsterdam (P = .048), and meeting partners outside Amsterdam (P = .036).

CONCLUSIONS

Distinct N. gonorrhoeae transmission networks were present in a mixed high-risk MSM population; concordance between clusters and epidemiological characteristics was present but not marked.

Molecular characterization of Neisseria gonorrhoeae isolates in Almaty, Kazakhstan, by VNTR analysis, Opa-typing and NG-MAST

In the present study, new variable number tandem repeats (VNTR) loci in the Neisseria gonorrhoeae genome were identified in silico. VNTR analysis scheme using PCR and agarose or polyacrylamide gel electrophoresis was developed based on nine VNTR loci with various degrees of polymorphism. The method was used to genotype a collection of 48 isolates, obtained from patients with gonorrhea in Almaty, Kazakhstan during the period from December 2008 to November 2009. This collection of isolates was also characterized by the opa-typing and multiantigen sequence typing (NG-MAST). The discriminatory power of the VNTR analysis translated by Hunter-Gaston Discrimination Index (HGDI) was similar to that of opa typing (HGDI=0.98 versus 0.97) and slightly higher than that of NG-MAST (HDGI=0.95). The adjusted Rand (AR) coefficients and Wallace coefficients showed that the overall concordance between the typing methods was not high. VNTR analysis described here is simple, inexpensive, easy to interpret, and it would be reliable for the comparison of data obtained in different laboratories. The proposed VNTR loci might be used for epidemiological studies of gonococcal infections.

Clonally related Neisseria gonorrhoeae isolates with decreased susceptibility to the extended-spectrum cephalosporin cefotaxime in Amsterdam, the Netherlands

From 2006 to 2008, Neisseria gonorrhoeae isolates were identified with decreased susceptibility to the extended-spectrum cephalosporin (ESC) cefotaxime among visitors of the Amsterdam sexually transmitted infections (STI) clinic, the Netherlands. Spread, clonality, and characteristics of 202 isolates were examined using antibiograms, conventional penA mosaic gene PCR, and N. gonorrhoeae multiple-locus variable-number tandem repeat analysis (NG-MLVA). A strictly defined subset was further characterized by N. gonorrhoeae multiantigen sequence typing (NG-MAST) and sequencing of ESC resistance determinants (penA, mtrR, and porB1b). Seventy-four N. gonorrhoeae isolates with a cefotaxime MIC of >0.125 μg/ml (group A), 54 with a cefotaxime MIC of 0.125 μg/ml (group B), and a control group of 74 with a cefotaxime MIC of <0.125 μg/ml (group C) were included. Fifty-three clonally related penA mosaic-positive isolates (penicillin-binding protein 2 type XXXIV) were identified in group A (n = 47 isolates; 64%) and B (n = 6 isolates; 11%). The 53 penA mosaic-positive isolates were predominantly NG-MAST ST1407 (87%) and contained an mtrR promoter A deletion (98%) and porB1b alterations G101K/A102N. All were assigned to the same NG-MLVA cluster that comprised in total 56 isolates. A correlation was found between decreased cefotaxime susceptibility and ST1407 that was highly prevalent among visitors of the Amsterdam STI clinic. The rapid spread of this strain, which also has been identified in many other countries, might be facilitated by high-risk sexual behavior and should be monitored closely to identify potential treatment failure. Quality-assured surveillance of ESC susceptibility on the national and international levels and exploration of new drugs and/or strategies for treatment of gonorrhea are crucial.

Review and international recommendation of methods for typing neisseria gonorrhoeae isolates and their implications for improved knowledge of gonococcal epidemiology, treatment, and biology

Gonorrhea, which may become untreatable due to multiple resistance to available antibiotics, remains a public health problem worldwide. Precise methods for typing Neisseria gonorrhoeae, together with epidemiological information, are crucial for an enhanced understanding regarding issues involving epidemiology, test of cure and contact tracing, identifying core groups and risk behaviors, and recommending effective antimicrobial treatment, control, and preventive measures. This review evaluates methods for typing N. gonorrhoeae isolates and recommends various methods for different situations. Phenotypic typing methods, as well as some now-outdated DNA-based methods, have limited usefulness in differentiating between strains of N. gonorrhoeae. Genotypic methods based on DNA sequencing are preferred, and the selection of the appropriate genotypic method should be guided by its performance characteristics and whether short-term epidemiology (microepidemiology) or long-term and/or global epidemiology (macroepidemiology) matters are being investigated. Currently, for microepidemiological questions, the best methods for fast, objective, portable, highly discriminatory, reproducible, typeable, and high-throughput characterization are N. gonorrhoeae multiantigen sequence typing (NG-MAST) or full- or extended-length porB gene sequencing. However, pulsed-field gel electrophoresis (PFGE) and Opa typing can be valuable in specific situations, i.e., extreme microepidemiology, despite their limitations. For macroepidemiological studies and phylogenetic studies, DNA sequencing of chromosomal housekeeping genes, such as multilocus sequence typing (MLST), provides a more nuanced understanding.

Evaluation of Neisseria gonorrhoeae multiple-locus variable-number tandem-repeat analysis, N. gonorrhoeae Multiantigen sequence typing, and full-length porB gene sequence analysis for molecular epidemiological typing

The performance characteristics of Neisseria gonorrhoeae multilocus variable-number tandem-repeat analysis were evaluated, by comparison with N. gonorrhoeae multiantigen sequence typing and full-length porB sequence typing. Assessment of the relatedness of intra- and interpatient isolates showed that all three genotyping techniques display a high resolution and typeability.