Molecular epidemiology of Neisseria gonorrhoeae- identification of the first presumed Swedish transmission chain of an azithromycin-resistant strain

Neisseria gonorrhoeae molecular typing for understanding sexual networks and antimicrobial resistance transmission: A systematic review

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Combined molecular and epidemiological data can describe the spread of gonorrhoea.

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Sexual networks can be inferred from molecular clusters of infection.

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Gender and sexual orientation are commonly used to characterise these networks.

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Application of these data within gonorrhoea control interventions is limited.

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Future studies should focus on evaluating molecular typing data in practice.

Objectives

Neisseria gonorrhoeae (NG) is a significant global public health concern due to rising diagnoses rates and antimicrobial resistance. Molecular combined with epidemiological data have been used to understand the distribution and spread of NG, as well as relationships between cases in sexual networks, but the public health value gained from these studies is unclear. We conducted a systematic review to examine how molecular epidemiological studies have informed understanding of sexual networks and NG transmission, and subsequent public health interventions.

Methods

Five research databases were systematically searched up to 31st March 2017 for studies that used sequence-based DNA typing methods, including whole genome sequencing, and linked molecular data to patient-level epidemiological data. Data were extracted and summarised to identify common themes.

Results

Of the 49 studies included, 82% used NG Multi-antigen Sequence Typing. Gender and sexual orientation were commonly used to characterise sexual networks that were inferred using molecular clusters; clusters predominantly of one patient group often contained a small number of isolates from other patient groups. Suggested public health applications included using these data to target interventions at specific populations, confirm outbreaks, and inform partner management, but these were mainly untested.

Conclusions

Combining molecular and epidemiological data has provided insight into sexual mixing patterns, and dissemination of NG, but few studies have applied these findings to design or evaluate public health interventions. Future studies should focus on the application of molecular epidemiology in public health practice to provide evidence for how to prevent and control NG.

Molecular epidemiology of Neisseria gonorrhoeae using multi-antigen sequence typing and pulse-field gel electrophoresis in highly endemic Western Australian populations

Background

The remote and indigenous populations of Western Australia (WA) have one of the highest notification rates of gonorrhoea in the world. Despite this, the low rate of antimicrobial resistance in Neisseria gonorrhoeae from these regions permits the use of amoxycillin as empirical therapy. We describe the first molecular epidemiological study of gonococci isolated from this population using two different typing platforms.

Methods

Pulse-field gel electrophoresis (PFGE), Neisseria gonorrhoeae multi-antigen sequence typing (NG-MAST) and antimicrobial susceptibility tests were performed on 128 consecutive N. gonorrhoeae isolates cultured between January 2011 and December 2013. To highlight clusters isolates were evaluated based on their tbpB sequence types.

Results

No predominant NG-MAST or PFGE types were found. A total of 67 distinct PFGE pulsotypes were identified amongst the 128 isolates in this study with 20 PFGE pulsotypes representing 78 isolates. A total of 59 NG-MAST sequence types were found, represented by 45 porB alleles and 28 tbpB alleles with 13 tbpB genomogroups from 45 NG-MAST sequence types. TbpB genomogroup 29, represented by 45 isolates, was by far the most common genomogroup overall.

Conclusions

Results from this study suggest that gonococcal epidemiology in WA is quite different between remote regions and major population centres and, in some cases, geographically restricted. It is likely that isolates originating from endemic regions of WA mostly represent independent, small sexual networks with an infrequent interchange between other communities and regions. Given the high rate of antimicrobial resistance elsewhere in Australia, ongoing surveillance is essential to ensure the enduring efficacy of amoxycillin empiric use in the remote regions of WA.

Azithromycin resistance and its mechanism in Neisseria gonorrhoeae strains in Hyogo, Japan

Therapeutic options are limited for Neisseria gonorrhoeae infection, especially for oral drugs. The purpose of this study was to investigate the susceptibility of N. gonorrhoeae to oral azithromycin (AZM) and the correlation between AZM resistance-related gene mutations and MIC. We examined the AZM MICs of clinical strains of N. gonorrhoeae, sequenced the peptidyltransferase loop in domain V of 23S rRNA, and investigated the statistical correlation between AZM MIC and the presence and number of the mutations. Among 59 N. gonorrhoeae strains, our statistical data showed that a deletion mutation was seen significantly more often in the higher-MIC group (0.5 μg/ml or higher) (35/37; 94.6%) than in the lower-MIC group (0.25 μg/ml or less) (4/22; 18.2%) (P < 0.0001). However, a mutation of codon 40 (Ala → Asp) in the mtrR gene (helix-turn-helix) was seen significantly more often in the lower-MIC group (12/22; 54.5%) (P < 0.0001). In N. gonorrhoeae multiantigen sequence typing (NG-MAST) analyses, ST4777 was representative of the lower-MIC group and ST1407, ST6798, and ST6800 were representative of the higher-MIC group. NG-MAST type 1407 was detected as the most prevalent type in AZM-resistant or -intermediate strains, as previously described. In conclusion, a deletion mutation in the mtrR promoter region may be a significant indicator for higher MIC (0.5 μg/ml or higher). ST4777 was often seen in the lower-MIC group, and ST1407, ST6798, and ST6800 were characteristic of the higher-MIC group. Further research with a greater number of strains would help elucidate the mechanism of AZM resistance in N. gonorrhoeae infection.

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.

Antimicrobial activity of flavonoids from Piper lanceaefolium and other Colombian medicinal plants against antibiotic susceptible and resistant strains of Neisseria gonorrhoeae

BACKGROUND

The successful treatment of Neisseria gonorrhoeae (NG) infections is increasingly problematic because of the resistance of this pathogen to multiple antimicrobial agents. This development underscores the need for new antimicrobial sources. In the current study, 21 crude methanol extracts, from 19 plants used in Colombian traditional medicine for cutaneous infections, were screened for antimicrobial activity against NG.

METHODS

Extracts were screened by disc susceptibility assay. In addition, the minimum inhibitory concentrations of active compounds from P. lanceaefolium were assayed using a panel of 26 NG strains comprising 12 antibiotic-resistant phenotypes.

RESULTS

In all, 71% of the crude extracts exhibited antibacterial activity against the antibiotic susceptible NG strain WHO V, whereas 10% of the extracts inhibited penicillinase-producing NG strain GC1-182. The crude extract of Piper lanceaefolium was the only extract to show significant activity without ultraviolet (UV) light activation. Preliminary screening identified 3 compounds in this plant possessing antimicrobial activity: the flavonoids 5,7-dihydroxyflavanone (pinocembrin), 2',4',6'-trihydroxychalcone (pinocembrin chalcone), and the prenylated benzoic acid derivative cyclolanceaefolic acid methyl ester. Pinocembrin and pinocembrin chalcone inhibited 100% of the NG panel at 64 μg/mL and 128 μg/mL, respectively, whereas cyclolanceaefolic acid methyl ester inhibited 44% of the strains at 128 μg/mL.

CONCLUSIONS

This is the first report of the antibacterial activity of Columbian plants against NG. The activity of the 2 flavonoids, pinocembrin, and pinocembrin chalcone, toward both susceptible and resistant NG strains makes them promising candidates for further research.

Methods for typing std pathogens (N. Gonorrhoeae, C. Trachomatis, T. Pallidum)

Phenotypic methods were initially used for bacterial typing yet they have a number of drawbacks limiting their use. Methods of molecular and genetic typing have become wide-spread today. Among these methods, bacterial typing based on multilocus sequence typing (Multilocus Sequence Typing - MLST) has been developing at the fastest rate. However, schemes of molecular and genetic typing of STD pathogens as compared to other bacteria are insufficiently developed, which considerably complicates the planning of measures aimed at the reduction of their spread.

Molecular Typing of Neisseria gonorrhoeae Isolates by Opa-Typing and Ribotyping in New Delhi, India

Control and preventive measures for gonococcal infections are based on precise epidemiological characteristics of N. gonorrhoeae isolates. In the present study the potential utility of opa-typing and ribotyping for molecular epidemiological study of consecutive gonococcal strains was determined. Sixty gonococcal isolates were subjected to ribotyping with two restriction enzymes, AvaII and HincII, and opa-typing with TaqI and HpaII for epidemiological characterization of gonococcal population. Ribotyping with AvaII yielded 6 ribotype patterns while twelve RFLP patterns were observed with HincII. Opa-typing of the 60 isolates revealed a total 54 opa-types, which 48 were unique and 6 formed clusters. Fifty-two opa-types were observed with TaqI-digested PCR product while opa-typing with HpaII demonstrated 54 opa-types. The opa-types from isolates that were epidemiologically unrelated were distinct, whereas those from the sexual contacts were identical. The results showed that opa-typing is highly useful for characterizing gonococcal strains from sexual contacts and has more discriminatory than ribotyping that could differentiate between gonococci of the same ribotype. The technique even with a single restriction enzyme has a high level of discrimination (99.9%) between epidemiologically unrelated isolates. In conclusion, the molecular methods such as opa-typing and ribotyping can be used for epidemiological characterization of gonococcal strains.

Emergence of high-level azithromycin resistance in Neisseria gonorrhoeae in England and Wales

OBJECTIVES

This study aimed to investigate the origin of high-level azithromycin resistance that emerged in isolates of Neisseria gonorrhoeae in England and Wales in 2007, and to establish methods for identifying high-level azithromycin resistance.

METHODS

The Gonococcal Resistance to Antimicrobials Surveillance Programme (GRASP) data from 2001-07 were examined for emerging trends in azithromycin susceptibility. Further to the identification of six high-level azithromycin-resistant isolates in GRASP 2007, an additional 102 isolates were selected on the basis of azithromycin susceptibility and geographic origin from the GRASP 2006 and 2007 collections. Susceptibility testing by Etest and disc diffusion was performed on all 108 isolates and 75 of these were typed by N. gonorrhoeae multiantigen sequence typing.

RESULTS

A slight drift towards higher MICs of azithromycin was observed in the gonococcal population since 2001. Of greater concern was the first example of a shift to high-level resistance observed in six isolates in 2007. All six isolates were sequence type 649, which was not observed in any of the lower-level azithromycin-resistant isolates from 2007 or in any isolates tested from the same geographical locations. Contact tracing data for one patient suggested a link with Scotland. Disc diffusion testing of all 108 isolates showed that azithromycin, but not erythromycin, discs can differentiate between low-level and high-level resistance.

CONCLUSIONS

High-level azithromycin resistance has emerged in England and Wales. Contact tracing and typing data suggest this may have originated from Scotland. Surveillance of azithromycin resistance will be key in controlling its further dissemination.

Azithromycin-resistant Neisseria gonorrhoeae strains recently isolated in Italy

OBJECTIVES

The aim of this study was to characterize 22 azithromycin-resistant Neisseria gonorrhoeae isolates, collected in Italy from January 2007 through June 2008, during a study of the prevalence of antibiotic resistance.

METHODS

MICs of azithromycin, ciprofloxacin, ceftriaxone, penicillin and tetracycline were determined by the Etest method. Azithromycin-resistant strains (MIC > or = 1 mg/L) were genetically analysed by N. gonorrhoeae multi-antigen sequence typing (NG-MAST) and PFGE.

RESULTS

A total of 22 azithromycin-resistant isolates were found among the 219 collected. Five of the 22 isolates showed high-level azithromycin resistance (MICs of 128 or 256 mg/L). Sixteen of the 22 were isolated from men who have sex with men. Among the 14 sequence types (STs) found by NG-MAST, 5 STs, containing clusters of two, three or four strains, were homogeneous with respect to epidemiology and/or antibiotic susceptibility. PFGE divided the 22 strains into two main groups that were possibly related.

CONCLUSIONS

This is the first report of gonococci with high-level resistance to azithromycin circulating in Italy. Correlation between NG-MAST results and epidemiological data for some of the analysed strains and patients could be established. This study represents a reference point for future surveillance in Italy and suggests the need to add azithromycin to the antibiotic susceptibility panel for gonococci.

Comparison of Neisseria gonorrhoeae multiantigen sequence typing and porB sequence analysis for identification of clusters of N. gonorrhoeae isolates

porB DNA sequence analysis and Neisseria gonorrhoeae multiantigen sequence typing (NG-MAST) methods were compared for their abilities to discriminate strains and to identify epidemiologically congruent pairs of N. gonorrhoeae. Both methods provided high-level discrimination of strains. NG-MAST further differentiated large porB-based clusters. However, considerations of cost suggest that porB DNA sequence analysis is a useful tool for preliminary molecular analysis of the epidemiology of N. gonorrhoeae.

Clinically relevant mutations that cause derepression of the Neisseria gonorrhoeae MtrC-MtrD-MtrE Efflux pump system confer different levels of antimicrobial resistance and in vivo fitness

The MtrC-MtrD-MtrE efflux pump system confers resistance to macrolide antibiotics and antimicrobial substances of the host innate defence. Clinical isolates with increased resistance to erythromycin and azithromycin frequently harbour mutations in the mtrR structural gene, which encodes a repressor of the mtrCDE operon, or the mtrR promoter region. The MtrC-MtrD-MtrE system is important for gonococcal survival in the murine genital tract, and derepression of the mtrCDE operon via deletion of mtrR confers increased fitness in vivo. Here we compared isogenic strains with naturally occurring mtrR locus mutations for differences in mtrCDE expression and pump-related phenotypes. Mutations upstream of mtrC, including those within the MtrR binding region and a novel mutation that increases mtrC RNA stability conferred the highest levels of derepression as measured by mtrCDE transcription and resistance to antibiotics, progesterone and antimicrobial peptides. In contrast, mutations within the mtrR coding sequence conferred low to intermediate levels of derepression. In vivo, the mtr mutants were more fit than the wild-type strain, the degree to which paralleled in vitro resistance gradients. These studies establish a hierarchy of mtrR locus mutations with regard to regulation of pump efflux, and suggest selection for more derepressed mutants may occur during mixed infections.

Emergence and spread of azithromycin-resistant Neisseria gonorrhoeae in Scotland

OBJECTIVES

The aim of this study was to analyse the trend in azithromycin susceptibility (AzDS) of Neisseria gonorrhoeae in Scotland between April 2004 and December 2007, and to characterize isolates exhibiting decreased AzDS or high-level azithromycin resistance (AzHLR).

METHODS

Antibiotic susceptibility testing and N. gonorrhoeae multiantigen sequence typing (NG-MAST) were performed on all gonococcal isolates received by the Scottish Bacterial Sexually Transmitted Infections Reference Laboratory (SBSTIRL) during the study period.

RESULTS

AzHLR isolates were observed for the first time in 2004 and increased from 0.3% to 3.9% in 2007. AzDS declined from 2.1% to 1.3% in the same period. Taken together, AzDS and AzHLR isolates accounted for 5.2% of the gonococcal infections in Scotland in 2007. NG-MAST revealed that only a small number of sequence types (STs) contained AzHLR and AzDS isolates; these STs also included azithromycin-susceptible isolates. Most STs containing AzHLR isolates were genetically related on the basis of their por and tbpB alleles; however, demographic data suggested that they formed discrete sexual networks.

CONCLUSIONS

AzHLR strains of N. gonorrhoeae are increasing in Scotland. A 1 g dose of azithromycin should not be considered as an alternative antibiotic therapy for gonococcal infections. The use of azithromycin to treat chlamydia in patients co-infected with N. gonorrhoeae results in a level of azithromycin in vivo that is sublethal for N. gonorrhoeae, which may lead to resistance.

The Neisseria gonorrhoeae population in Sweden during 2005-phenotypes, genotypes and antibiotic resistance

In Sweden, the gonorrhoea incidence has significantly increased since an all-time low in 1996. We aimed to phenotypically and genotypically characterise N. gonorrhoeae isolates (n=180) transmitted in Sweden during 2005. All isolates were susceptible to cefixime, ceftriaxone, and spectinomycin. However, 2%, 50% and 75% displayed intermediate susceptibility or resistance to azithromycin, ciprofloxacin and ampicillin, respectively. The isolates were assigned to 28 different serovars using Genetic Systems monoclonal antibodies (Mabs) (discriminatory index, 91.0%) and 46 different serovars using Pharmacia Mabs (index, 94.4%). Furthermore, they displayed 95 porB sequences (index, 97.8%) and 95 N. gonorrhoeae multiantigen sequence typing (NG-MAST) sequence types (STs) (index, 98.0%). 51 (54%) of these STs have not been previously described. 14 ST clusters, comprising between 3 and 15 isolates, were identified that indicate the existence of several transmission chains. The high number of unique STs (n=63) may be associated with import of strains from abroad, local emergence of new STs, incomplete epidemiological surveillance, and/or suboptimal diagnostics, including contact tracing. Overall, the Swedish N. gonorrhoeae population was remarkably diversified. Comprehensive knowledge regarding transmission, phenotypes (including antibiotic resistance), but also in many cases highly discriminative and precise genotypic characteristics of the N. gonorrhoeae strains circulating in our societies, is crucial.

Clusters of circulating Neisseria gonorrhoeae strains and association with antimicrobial resistance in Shanghai

OBJECTIVES

(i) To distinguish Neisseria gonorrhoeae isolates in Shanghai by porB typing; (ii) to ascertain the congruence of porB DNA sequence typing with cases linked epidemiologically; (iii) to determine the association of specific PorB mutations with antimicrobial resistance to penicillin or tetracycline.

METHODS

porB DNA sequences of 174 N. gonorrhoeae isolates, collected from 143 male patients and 31 female sexual partners in Shanghai were determined. Phylogenetic analysis was used to determine sequence associations and concordance with epidemiologically linked cases. PorB protein sequences were compared with the wild-type sequence to identify mutations associated with antimicrobial resistance to penicillin and tetracycline.

RESULTS

porB1a genotypes comprised 27.0% of the isolates and included 15 distinct DNA sequences, while 73.0% of the isolates carried porB1b genotypes with 63 distinct DNA sequences. porB DNA sequence typing was congruent with patient-reported sexual contacts. In addition, porB DNA sequence analysis revealed a number of strains with identical DNA sequences not identified through traditional epidemiological methods. The porB1b isolates had a significantly higher percentage of chromosomally mediated resistance to tetracycline and higher MIC50s to penicillin and ciprofloxacin. G120K/A121D mutations were observed in 71.1% of PIB isolates and were associated with resistance to penicillin and/or tetracycline. The majority of the PIA isolates (82.1%) also carried G120D/A121G double mutations. The index of discrimination for porB DNA sequence analysis was 95%.

CONCLUSIONS

The porB1b genotype was found to be predominant in Shanghai. porB DNA sequence typing was sufficiently discriminatory for differentiating N. gonorrhoeae isolates and was congruent with epidemiological linkages. Novel porB sequences of N. gonorrhoeae and novel mutations of PorB proteins were identified.

Molecular characterization of Neisseria gonorrhoeae identifies transmission and resistance of one ciprofloxacin-resistant strain

A highly discriminative and objective genetic characterization of N. gonorrhoeae, which increases our knowledge of strain populations in different geographic areas, is crucial for the development of improved control measures. In the present study, conventional phenotypic characterization and genetic characterization by means of pulsed-field gel electrophoresis (PFGE), sequencing of the entire porB gene, N. gonorrhoeae multiantigen sequence typing (NG-MAST), and pyrosequencing of a quinolone resistance determining region (QRDR) of the gyrA gene of Swedish ciprofloxacin-resistant N. gonorrhoeae serovar IB-10 isolates (n=45) were performed. The genetic characterization identified one widely spread ciprofloxacin-resistant N. gonorrhoeae ST147 strain. In addition, isolates with slightly different genetic characteristics, which presumably reflect the ongoing evolution only, were also identified. All the isolates contained single nucleotide polymorphisms in QRDR of the gyrA gene that are highly correlated with ciprofloxacin resistance. Consequently, comprehensive characterization identified the first confirmed large domestic transmission, mainly among young heterosexuals, of one ciprofloxacin-resistant N. gonorrhoeae strain in Swedish society during 2002-2003. In conclusion, a precise, i.e. genetic, characterization for identification of individual strains is a very valuable support to the crucial active surveillance of the epidemiological characteristics and the antibiotic susceptibility of N. gonorrhoeae in the effective treatment of gonorrhoea.