Multidrug-resistant strains of Neisseria gonorrhoeae in Greece

Azithromycin Susceptibility Testing and Molecular Investigation of Neisseria gonorrhoeae Isolates Collected in Russia, 2020-2021

The aim of this work was to study the resistance to macrolides (azithromycin) in the modern Russian population of N. gonorrhoeae with the analysis of genetic resistance determinants. Azithromycin is not used to treat gonococcal infection in Russia. However, among 162 isolates collected in 2020-2021, 22 isolates (13.6%) were phenotypically resistant to azithromycin. Mutations in 23S rRNA genes were found only in two isolates; erm and mefA genes were absent. Azithromycin resistance was shown to be predominantly associated with mutations in the mtrR and mtrD genes of the MtrCDE efflux pump and their mosaic alleles which may have formed due to a horizontal transfer from N. meningitidis. A total of 30 types of mtrR alleles and 10 types of mtrD alleles were identified including mosaic variants. Matching between the mtrR and mtrD alleles was revealed to indicate the cooperative molecular evolution of these genes. A link between the mtrR and mtrD alleles and NG-MAST types was found only for NG-MAST 228 and 807, typical of N. gonorrhoeae in Russia. The high level of resistance to azithromycin in Russia may be related to the spread of multiple transferable resistance to antimicrobials regardless of their use in the treatment of gonococcal infection.

Azithromycin resistance and its molecular characteristics in Neisseria gonorrhoeae isolates from a tertiary care centre in North India

Treatment guidelines for management of uncomplicated gonorrhoeae have been recently modified owing to alarming upsurge in azithromycin resistance. This study investigated the prevalence and genetic determinants of gonococcal azithromycin resistance in India. Four (5.7%) of 70 gonococcal isolates were resistant to azithromycin. Of 16 isolates investigated for molecular mechanisms of resistance, 13 (81.3%) and 6 (37.5%) isolates exhibited mutations in coding and promoter regions of mtrR gene, respectively. However, ermA, ermB and ermC genes or mutations in rrl gene were absent in all isolates. Azithromycin resistance is low in India posing no immediate threat to use of dual-therapy for syndromic management.

Molecular characterization of decreased susceptibility to ceftriaxone and genotyping of Neisseria gonorrheae isolates in New Delhi, India

Data on genetic characteristics of Neisseria gonorrhoeae isolates exhibiting decreased susceptibility to extended-spectrum cephalosporins in India is deficient. In this study, we have sequenced penA, porB, mtrR and ponA and bla_TEM genes in 70 clinical isolates of NG with varying ceftriaxone MICs. Amongst these, 22 (31.4%) were PPNG. Additionally, N. gonorrheae Multiantigen Sequence Typing was performed. Fisher exact and χ² were used to evaluate significance of mutations with MICs. A total of six non-mosaic penA (Penicillin binding protein 2 [PBP2]) amino acid patterns were seen (II, IV, IX, XII, XIX, XXII) of which, pattern IX was significantly associated with decreased susceptibility to ceftriaxone. Other significant associations were noted in porB & mtrR genes. There were no mutations in bla_TEM gene. ST6069 was significantly associated with decreased susceptibility to ceftriaxone. To conclude, development of decreased susceptibility to ceftriaxone in gonococci involves cumulation of different mutations in the four chromosomal genes investigated.

Phenotypic and Genotypic Characterization of Neisseria gonorrhoeae Isolates from New Zealand with Reduced Susceptibility to Ceftriaxone

Aim: To characterize mutations in penA, mtrR, ponA, and porB_IB, considered target genes for antimicrobial resistance, in Neisseria gonorrhoeae isolates with elevated minimum inhibitory concentrations (MICs) of ceftriaxone cultured from patients in New Zealand. Results: Out of 28 isolates supplied by the Institute of Environmental Science and Research Limited (ESR), Porirua, New Zealand, 14 were found to show reduced susceptibility to ceftriaxone (MIC of 0.06 mg/L) according to criteria used by the ESR and the Australian Gonococcal Surveillance Programme (AGSP) when tested in our laboratory. Rates of resistance to ciprofloxacin, azithromycin, penicillin, and tetracycline were 100% (28/28), 7% (2/28), 36% (10/28), and 25% (7/28), respectively. Ten different penA (Penicillin binding protein 2 [PBP2]) sequences were observed. The most common mosaic penA M-1 resembled mosaic penA XXXIV, which has been associated with ceftriaxone treatment failures in other countries. Four semimosaic PBP2 sequences were observed and may be novel PBP sequences, while four out of five nonmosaic PBP2 sequences were similar to PBP2 sequences reported in Australia. Twenty-one isolates harbored mutations in all 4 genes (penA, mtrR, porB_IB, and ponA), and 13 of these exhibited reduced susceptibility to ceftriaxone. Conclusion: Mutations in penA, mtrR, porB_IB, and ponA observed in this study may have contributed to reduced susceptibility to ceftriaxone among New Zealand gonococcal isolates. Over half (16/22) of mosaic penA sequences from the gonococcal isolates resembled penA XXXIV.

Emergence of Neisseria gonorrhoeae Strains Harboring a Novel Combination of Azithromycin-Attenuating Mutations

The nimbleness of Neisseria gonorrhoeae to evade the effect of antibiotics has perpetuated the fight against antibiotic-resistant gonorrhea for more than 80 years. The ability to develop resistance to antibiotics is attributable to its indiscriminate nature in accepting and integrating exogenous DNA into its genome. Here, we provide data demonstrating a novel combination of the 23S rRNA A2059G mutation with a mosaic-multiple transferable resistance (mosaic-mtr) locus haplotype in 14 N. gonorrhoeae isolates with high-level azithromycin MICs (≥256 μg/ml), a combination that may confer more fitness than in previously identified isolates with high-level azithromycin resistance. To our knowledge, this is the first description of N. gonorrhoeae strains harboring this novel combination of resistance determinants. These strains were isolated at two independent jurisdictions participating in the Gonococcal Isolate Surveillance Project (GISP) and in the Strengthening the U.S. Response to Resistant Gonorrhea (SURRG) project. The data suggest that the genome of N. gonorrhoeae continues to shuffle its genetic material. These findings further illuminate the genomic plasticity of N. gonorrhoeae, which allows this pathogen to develop mutations to escape the inhibitory effects of antibiotics.

Closed Genome Sequences of Clinical Neisseria gonorrhoeae Strains Obtained from Combined Oxford Nanopore and Illumina Sequencing

Neisseria gonorrhoeae is the etiological agent of gonorrhea, the second most common notifiable disease in the United States. Here, we used a hybrid approach combining Oxford Nanopore Technologies MinION and Illumina MiSeq sequencing data to obtain closed genome sequences of nine clinical N. gonorrhoeae isolates.

Neisseria gonorrhoeae is the etiological agent of gonorrhea, the second most common notifiable disease in the United States. Here, we used a hybrid approach combining Oxford Nanopore Technologies MinION and Illumina MiSeq sequencing data to obtain closed genome sequences of nine clinical N. gonorrhoeae isolates.

Neisseria gonorrhoeae Sequence Typing for Antimicrobial Resistance, a Novel Antimicrobial Resistance Multilocus Typing Scheme for Tracking Global Dissemination of N. gonorrhoeae Strains

A curated Web-based user-friendly sequence typing tool based on antimicrobial resistance determinants in Neisseria gonorrhoeae was developed and is publicly accessible (https://ngstar.canada.ca). The N. gonorrhoeae Sequence Typing for Antimicrobial Resistance (NG-STAR) molecular typing scheme uses the DNA sequences of 7 genes (penA, mtrR, porB, ponA, gyrA, parC, and 23S rRNA) associated with resistance to β-lactam antimicrobials, macrolides, or fluoroquinolones. NG-STAR uses the entire penA sequence, combining the historical nomenclature for penA types I to XXXVIII with novel nucleotide sequence designations; the full mtrR sequence and a portion of its promoter region; portions of ponA, porB, gyrA, and parC; and 23S rRNA sequences. NG-STAR grouped 768 isolates into 139 sequence types (STs) (n = 660) consisting of 29 clonal complexes (CCs) having a maximum of a single-locus variation, and 76 NG-STAR STs (n = 109) were identified as unrelated singletons. NG-STAR had a high Simpson's diversity index value of 96.5% (95% confidence interval [CI] = 0.959 to 0.969). The most common STs were NG-STAR ST-90 (n = 100; 13.0%), ST-42 and ST-91 (n = 45; 5.9%), ST-64 (n = 44; 5.72%), and ST-139 (n = 42; 5.5%). Decreased susceptibility to azithromycin was associated with NG-STAR ST-58, ST-61, ST-64, ST-79, ST-91, and ST-139 (n = 156; 92.3%); decreased susceptibility to cephalosporins was associated with NG-STAR ST-90, ST-91, and ST-97 (n = 162; 94.2%); and ciprofloxacin resistance was associated with NG-STAR ST-26, ST-90, ST-91, ST-97, ST-150, and ST-158 (n = 196; 98.0%). All isolates of NG-STAR ST-42, ST-43, ST-63, ST-81, and ST-160 (n = 106) were susceptible to all four antimicrobials. The standardization of nomenclature associated with antimicrobial resistance determinants through an internationally available database will facilitate the monitoring of the global dissemination of antimicrobial-resistant N. gonorrhoeae strains.

Conjunctivitis caused by Neisseria gonorrhoeae isolates with reduced cephalosporin susceptibility and multidrug resistance

We report two cases of conjunctivitis caused by Neisseria gonorrhoeae with reduced cephalosporin susceptibility. Patients showed no response to cefmenoxime eye drops and intravenous ceftriaxone administration. The patients' condition improved after the addition of oral minocycline. The isolates contained the mosaic penA for reduction of β-lactam susceptibility.

Emergence of increased azithromycin resistance during unsuccessful treatment of Neisseria gonorrhoeae infection with azithromycin (Portland, OR, 2011)

We describe the emergence of an azithromycin-resistant Neisseria gonorrhoeae variant in a man from Portland, Oregon, during sole treatment with 2 g azithromycin. This report highlights the ease with which gonococcal macrolide resistance can emerge, the threat of multidrug resistant N. gonorrhoeae, and the need for adherence to Centers for Disease Control and Prevention treatment guidelines.

Cefixime and ceftriaxone susceptibility of Neisseria gonorrhoeae in Italy from 2006 to 2010

Neisseria gonorrhoeae resistance to cephalosporins, the currently recommended treatment, and treatment failures with cefixime have been reported worldwide. The purposes of the present study were (i) to examine the susceptibility of N. gonorrhoeae isolates isolated in Italy from 2006 through 2010 to cefixime (n = 293) taking into account both European Committee on Antimicrobial Susceptibility Testing (EUCAST) and Clinical And Laboratory Standards Institute (CLSI) criteria for categorization; (ii) to determine the contribution to decreased/resistant susceptibility of mutations in the penA, mtrR, ponA and porB1b genes in a subsample of isolates; and (iii) to genotype the isolates showing decreased susceptibility or resistance to cefixime, by N. gonorrhoeae multi-antigen sequence typing (NG-MAST) and by pulsed-field gel electrophoresis (PFGE) to identify the predominant genotypes. Minimum inhibitory concentrations (MICs) were determined by the E-test and agar dilution method on 293 isolates and results were interpreted according to both EUCAST 2010 (MIC R >0.12 mg/L) and CLSI 2008 (MIC R >0.25 mg/L) criteria. All isolates showed full susceptibility to ceftriaxone, whereas those with a MIC for cefixime ≥0.125 mg/L were on the increase from 2008 through 2010. The same penA gene alterations were found among isolates with MICs close to the EUCAST breakpoint as the resistant ones, and they belong to ST1407. Seven isolates, belonging to various sequence types, showed a different por allele, though similar to the por 908 allele present in ST1407. PFGE divided strains ST1407 into two main groups confirming their genetic relationship.

A novel mechanism of high-level, broad-spectrum antibiotic resistance caused by a single base pair change in Neisseria gonorrhoeae

The MtrC-MtrD-MtrE multidrug efflux pump of Neisseria gonorrhoeae confers resistance to a diverse array of antimicrobial agents by transporting these toxic compounds out of the gonococcus. Frequently in gonococcal strains, the expression of the mtrCDE operon is differentially regulated by both a repressor, MtrR, and an activator, MtrA. The mtrR gene lies 250 bp upstream of and is transcribed divergently from the mtrCDE operon. Previous research has shown that mutations in the mtrR coding region and in the mtrR-mtrCDE intergenic region increase levels of gonococcal antibiotic resistance and in vivo fitness. Recently, a C-to-T transition mutation 120 bp upstream of the mtrC start codon, termed mtr₁₂₀, was identified in strain MS11 and shown to be sufficient to confer high levels of antimicrobial resistance when introduced into strain FA19. Here we report that this mutation results in a consensus −10 element and that its presence generates a novel promoter for mtrCDE transcription. This newly generated promoter was found to be stronger than the wild-type promoter and does not appear to be subject to MtrR repression or MtrA activation. Although rare, the mtr₁₂₀ mutation was identified in an additional clinical isolate during sequence analysis of antibiotic-resistant strains cultured from patients with gonococcal infections. We propose that cis-acting mutations can develop in gonococci that significantly alter the regulation of the mtrCDE operon and result in increased resistance to antimicrobials.

Gonorrhea is the second most prevalent sexually transmitted bacterial infection and a worldwide public health concern. As there is currently no vaccine against Neisseria gonorrhoeae, appropriate diagnostics and subsequent antibiotic therapy remain the primary means of infection control. However, the effectiveness of antibiotic treatment is constantly challenged by the emergence of resistant strains, mandating a thorough understanding of resistance mechanisms to aid in the development of new antimicrobial therapies and genetic methods for antimicrobial resistance testing. This study was undertaken to characterize a novel mechanism of antibiotic resistance regulation in N. gonorrhoeae. Here we show that a single base pair mutation generates a second, stronger promoter for mtrCDE transcription that acts independently of the known efflux system regulators and results in high-level antimicrobial resistance.

Analysis of emergence of quinolone-resistant gonococci in Greece by combined use of Neisseria gonorrhoeae multiantigen sequence typing and multilocus sequence typing

The prevalence of quinolone-resistant Neisseria gonorrhoeae (QRNG) in Greece remained low from 1997 to 2003 but increased dramatically from 11% to 56% between 2004 and 2007. N. gonorrhoeae multiantigen sequence typing (NG-MAST) and multilocus sequence typing (MLST) were used to investigate trends in quinolone resistance from 1997 to 2007 and explore the origins of the recent increase in QRNG. We characterized 295 QRNG isolates from the study period and 233 quinolone-susceptible (QS) gonococci from 2004 and 2005, when the rapid increase in QRNG occurred. From 1997 to 1999, an outbreak of QRNG was due to the dissemination of isolates of serovar Arst that belonged to two closely related genotypes. Few QRNG isolates, of diverse genotypes, were present between 2001 and 2003, whereas the sharp increase in QRNG from 2004 onwards was due to the appearance of serovar Bropyst isolates of several major NG-MAST sequence type (STs) that previously had not been identified in Greece. These isolates were shown by MLST to be variants of a single multiply antibiotic-resistant QRNG strain (ST1901) that appeared in Greece and rapidly diversified into 31 NG-MAST STs. There were no isolates of MLST ST1901 or any of the 31 NG-MAST STs among QS isolates from 2004 and 2005 or among 8 representatives of multiresistant but quinolone-susceptible serovar Bropyst isolates circulating in Greece during the 1990 s, supporting the view that the recent increase in QRNG was due to importation of a QRNG strain(s) of MLST ST1901 into Greece. Recently, multiresistant QRNG isolates of ST1901 with reduced susceptibility to the newer cephalosporins have appeared in Greece.

Changing figures of antimicrobial susceptibility and serovar distribution in Neisseria gonorrhoeae isolated in Greece

OBJECTIVES

To update surveillance data on antimicrobial susceptibility of Neisseria gonorrhoeae isolated in Greece with information for the years 2005 to 2008, and analyze changes occurred from the previous 4-year period.

METHODS

Annual antimicrobial susceptibility rates, susceptibility patterns, and serovars of 635 gonococci isolated in 2005 to 2008 were determined and compared to respective data concerning the gonococcal sample of 2001 to 2004. Genetic similarity of the isolates in phenotypic clusters was investigated by pulsed field gel electrophoresis. Epidemiologic information was also considered.

RESULTS

Despite a reduction in the isolation frequency of penicillinase-producing strains (3.9% vs. 11.6% in the previous period), the rates of resistance and intermediate susceptibility increased for penicillin, as well as for tetracycline, erythromycin, and chloramphenicol, leaving very small proportions of isolates sensitive to these agents (4.3%, 12.8%, 10.2%, and 3.6%, respectively). Resistance to fluoroquinolones increased from 11.3% in 2004 up to 63% in 2008, and strongly correlated with multidrug-resistant isolates of Bropyst serovar, accounting for 72.6% of the quinolone-resistant strains isolated during the last 4 years. All isolates were susceptible to spectinomycin and only 2 exceeded susceptibility breakpoints set for cefotaxime, exhibiting MICs 0.75 to 1 microg/mL. These latter isolates, however, belonged to a cluster of strains with decreased susceptibility to cephalosporins (CDS, cefotaxime MICs >or=0.25 microg/mL) that emerged in late 2006 and increased in frequency up to 20.7% through 2008. Notably, CDS isolates were also quinolone-resistant and multiresistant, further contributing to the increasing rates of quinolone and multidrug resistance in the Greek gonococcal sample.

CONCLUSIONS

Antimicrobial susceptibility figures of Neisseria gonorrhoeae in Greece are worsening due to changes in the synthesis of gonococcal population, resulting from high endemicity rates of multidrug-resistant strains.

Simple, rapid, and inexpensive detection of Neisseria gonorrhoeae resistance mechanisms using heat-denatured isolates and SYBR green-based real-time PCR

Neisseria gonorrhoeae has developed resistance to multiple classes of antimicrobials. There is now growing concern that without the availability of appropriate public health strategies to combat this problem, gonorrhea could become untreatable. For this reason, surveillance for gonococcal antimicrobial resistance must be optimal both in terms of obtaining a representative sample of gonococcal isolates and in terms of having the appropriate tools to identify resistance. To aid with this surveillance, molecular tools are increasingly being used. In the present study, we investigated the use of a simple heat denaturation protocol for isolate DNA preparation combined with SYBR green-based real-time PCR for the identification of mutations associated with N. gonorrhoeae antimicrobial resistance. A total of 109 clinical gonococcal isolates were tested by high-resolution melting (HRM) curve analysis for chromosomal mutations associated with gonococcal resistance to beta-lactam antibiotics: a penA 345A insertion, ponA L421P, mtrR G45D, substitutions at positions 120 and 121 in porB1b, and an adenine deletion in the mtrR promoter. An allele-specific PCR assay was also investigated for its ability to detect the adenine deletion in the mtrR promoter. The results were compared to those obtained by DNA sequencing. Our HRM assays provided the accurate discrimination of heat-treated isolates in which the sequence types differed in GC content, including isolates with the penA 345A insertion and the ponA L421P and mtrR G45D mutations. The allele-specific PCR assay accurately identified isolates with the adenine deletion in the mtrR promoter. Heat-denatured DNA combined with SYBR green-based real-time PCR offers a simple, rapid, and inexpensive means of detecting gonococcal resistance mechanisms. These methods may have broader application in the detection of polymorphisms associated with phenotypes of interest.

Phenotypic and genetic characterization of the 2008 WHO Neisseria gonorrhoeae reference strain panel intended for global quality assurance and quality control of gonococcal antimicrobial resistance surveillance for public health purposes

OBJECTIVES

Emergence and spread of antimicrobial resistance (AMR) in Neisseria gonorrhoeae remain a major global problem and expanded, but valid, AMR surveillance is crucial for public health purposes. The World Health Organization (WHO) Collaborating Centre in Sydney, Australia, continually evaluates N. gonorrhoeae strains used in quality control and assurance aspects of the national, WHO regional and international programmes for AMR surveillance it conducts. Here we phenotypically and genetically characterized the 2008 WHO N. gonorrhoeae reference panel, widely used under existing WHO AMR surveillance protocols.

MATERIALS AND METHODS

The eight N. gonorrhoeae WHO reference strains were phenotypically characterized by antibiogram, auxotype, serovar and prolyliminopeptidase screening; and genetically with regard to resistance plasmid types, polymorphisms in divergent genetic resistance-mediating loci (n = 9), porB sequencing and N. gonorrhoeae multi-antigen sequence typing.

RESULTS

The 2008 WHO reference strains represented all the important susceptible and resistant phenotypes, including corresponding resistance genotypes, and the range of resistances currently seen for relevant antimicrobials. Several pertinent additional phenotypic and genotypic markers, for example, epidemiological markers, were also determined.

CONCLUSIONS

The 2008 WHO N. gonorrhoeae reference strain panel was extensively characterized, which is crucial for the expansion of gonococcal AMR surveillance nationally and internationally. The panel is available through WHO sources for quality assurance and quality control aspects of current phenotypic testing protocols, to allow valid comparison of AMR data derived by divergent methods, and also for the control of present and future molecular assays for AMR detection. Additional WHO reference strains can be included as required by the emergence of additional resistant phenotypes and/or genotypes.

Molecular analysis of tetracycline-resistant gonococci: rapid detection of resistant genotypes using a real-time PCR assay

The aim of this study was to examine tetracycline-resistant gonococci and to set up a real-time PCR method to identify, in the same assay, both the chromosomally and the plasmid-mediated tetracycline-resistant genotypes. A retrospective analysis for tetracycline susceptibility was performed by the E-test and agar dilution methods on 289 gonococci isolated in Italy from 2003 to 2005. Molecular mechanisms of resistance were investigated by both sequence analyses of the three main genes associated with chromosomally mediated resistance (mtrR, penB and rpsJ genes) and by the identification of plasmids carrying the tetM determinant associated with plasmid-mediated resistance, by PCR (American- or Dutch-type plasmids). The genetic relatedness of nonsusceptible strains was evaluated by pulsed field gel electrophoresis (PFGE). The results showed the presence of 22.5% tetracycline-resistant and 49.5% tetracycline-intermediate gonococci. Coexistence of chromosomally and plasmid-mediated resistance to tetracycline was observed in the majority of resistant isolates. No clonal structure was highlighted by analysis of PFGE pattern profiles. Real-time PCR assay was able to identify all the tetracycline nonsusceptible gonococci correctly for the presence of both chromosomally and/or plasmid-mediated genotypes.

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.

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.

Neisseria gonorrhoeae isolates with reduced susceptibility to cefixime and ceftriaxone: association with genetic polymorphisms in penA, mtrR, porB1b, and ponA

The recent emergence and transmission of Neisseria gonorrhoeae isolates with reduced susceptibility to expanded-spectrum cephalosporins such as cefixime and ceftriaxone have been reported. The aim of this study was to determine the correlation of different polymorphisms in the penA, mtrR, porB1b (penB), and ponA genes of N. gonorrhoeae with reduced susceptibility to cefixime and ceftriaxone. Eighteen gonococcal isolates with reduced cefixime and ceftriaxone susceptibility (Cef(i)) and two susceptible isolates were characterized using serovar determination, antibiograms, N. gonorrhoeae multiantigen sequence typing (NG-MAST), and sequencing of penA, mtrR, porB1b, and ponA alleles. For the Cef(i) isolates (n = 18), the MICs of cefixime and ceftriaxone ranged between 0.032 to 0.38 mug/ml and 0.064 to 0.125 mug/ml, respectively. These isolates were assigned five different serovars and six divergent NG-MAST sequence types. Eleven isolates (61%) with higher MICs of cefixime and ceftriaxone contained a nearly identical penA mosaic allele and previously described polymorphisms in mtrR (a single nucleotide [A] deletion in the promoter), penB (mutations in porB1b encoding loop 3 of PorB1b), and ponA (ponA1 polymorphism). The remaining seven Cef(i) isolates (39%), which had somewhat lower MICs of cefixime and ceftriaxone, contained an aspartic acid insertion (Asp-345a) in PBP 2 in conjunction with alterations of 4 to 10 amino acid residues in the C-terminal region of the transpeptidase domain of penA. In conclusion, an unambiguous association between penA mosaic alleles, in conjunction with genetic polymorphisms in mtrR, porB1b, and ponA, and greater reduced susceptibility to cefixime and ceftriaxone was identified.

A novel real-time duplex PCR assay for detecting penA and ponA genotypes in Neisseria gonorrhoeae: Comparison with phenotypes determined by the E-test

BACKGROUND

For many years, the pathogenic bacterium Neisseria gonorrhoeae, the etiologic agent of gonorrhea, was generally susceptible to penicillin, until the emergence of resistant strains. Well-characterized genetic variations in the penicillin resistance-determining region correlate with decreased susceptibility to penicillin. At least 5 genes (penA, penB, mtrR, ponA, and penC) are involved in the chromosomally mediated resistance to this antibiotic. To date, no development of multiplex PCR assays targeting a range of gonococcal genes and variations as a means of predicting antibiotic resistance has been reported.

METHODS

The aim of this study was to develop a duplex assay using DNA from isolated strains. We describe the development and evaluation on the LightCycler platform of a real-time duplex PCR assay (hybridization probe format) for rapid and specific detection of ponA and penA variations, predicting penicillin susceptibilities.

RESULTS

The real-time duplex PCR assay successfully detected variations in ponA and penA genes by use of distinct melting temperatures from a total of 120 Neisseria gonorrhoeae isolates. Moreover, the variation profiles obtained with the real-time PCR and the melting analysis showed good correlation with the pattern of penicillin susceptibility generated with classical antibiograms. Nucleotide sequencing data were in complete agreement with multiplex assay results.

CONCLUSIONS

The presented assay is suitable for the detection of chromosomally mediated resistant strains of Neisseria gonorrhoeae in genotyping studies and could be valuable in the effective antimicrobial strategy to gonococci.

Rapid detection of a chromosomally mediated penicillin resistance-associated ponA mutation in Neisseria gonorrhoeae using a real-time PCR assay

The recent emergence of a decreased susceptibility of Neisseria gonorrhoeae strains to penicillin in New Caledonia has lead clinicians to operate a change in the treatment strategy. In addition, this important health issue has emphasized the need for a rapid means of detecting penicillin resistance in N. gonorrhoeae in order to select an effective treatment and limit the spread of resistant strains. In recent years, the use of fluorescence resonance energy transfer on the LightCycler has proven to be a valuable tool for the screening of mutations occurring in the genome of various microorganisms. In this study, we developed a real-time PCR assay coupled with a fluorometric hybridization probes system to detect a penicillin resistance-associated mutation on the N. gonorrhoeae ponA gene. Following an extensive evaluation involving 136 isolates, melting curve analysis correctly evidenced a 5 degrees C T(m) shift in all N. gonorrhoeae strains possessing this mutation, as determined by conventional sequencing analysis. Moreover, the mutation profiles obtained with the real-time PCR showed good correlation with the pattern of penicillin susceptibility generated with classical antibiograms. Overall, our molecular assay allowed an accurate and reproducible determination of the susceptibility to penicillin corresponding to a mutation present in all chromosomally mediated resistant strains of N. gonorrhoeae.

Antimicrobial susceptibility of Neisseria gonorrhoeae in Greece: data for the years 1994-2004

OBJECTIVES

Surveillance data concerning antimicrobial susceptibilities of Neisseria gonorrhoeae isolated in Greece during the 11 year period 1994-2004 are presented.

METHODS

Antimicrobial susceptibilities of all gonococcal isolates received by the Greek National Reference Center for N. gonorrhoeae during the study period were determined in terms of MICs using Etest. Trends in yearly isolation frequencies by susceptibility category were estimated for defining significant changes in overall susceptibility figures.

RESULTS

Cefotaxime and spectinomycin retained undiminished activity against all isolates throughout the study period. High rates of resistance and intermediate susceptibilities were noticed for penicillin, tetracycline and erythromycin, and even for norfloxacin and ciprofloxacin. A substantial portion (16.5%) of the gonococcal samples consisted of multiresistant strains exhibiting resistance to two or more agents of different antibiotic classes. Although annual rates of low-level chromosomal resistance decreased, high-level resistance owing to the presence of penicillin- and tetracycline-resistance plasmids increased. Fluoroquinolone resistance also showed a significant increasing trend after 1996, reaching a peak rate of 11.3% in 2004.

CONCLUSION

Third-generation cephalosporins and spectinomycin should be considered as first-choice drugs for the empirical treatment of gonorrhoea in Greece.

Analysis of mutations within multiple genes associated with resistance in a clinical isolate of Neisseria gonorrhoeae with reduced ceftriaxone susceptibility that shows a multidrug-resistant phenotype

A Neisseria gonorrhoeae strain with a reduced susceptibility to ceftriaxone (minimum inhibitory concentration (MIC) = 0.5 microg/mL) was isolated among 398 clinical isolates obtained from 2000-2001 in Fukuoka City, Japan. The N. gonorrhoeae strain was negative for penicillinase production but it showed multidrug resistance against penicillin (MIC = 8 microg/mL), tetracycline (MIC = 4 microg/mL), azithromycin (MIC = 0.5 microg/mL) and ciprofloxacin (MIC = 16 microg/mL). The molecular mechanisms of the multidrug-resistant phenotype in this strain were analysed. Polymerase chain reaction and direct DNA sequencing were performed to identify mutations within the penA, ponA, mtrR, penB, gyrA and parC genes of the gonococcal strain, which thus explain the multidrug-resistant phenotype. The N. gonorrhoeae strain contained a significantly different sequence of the penA gene from that of the ceftriaxone-susceptible strains. Some regions of the transpeptidase domain within this penA gene were closely similar to those found in other Neisseria species such as Neisseria subflava, Neisseria flavescens or Neisseria perflava/sicca. This strain also included a ponA mutation that is associated with high-level resistance to penicillin, mtrR mutations that mediate overexpression of the MtrCDE efflux pump responsible for resistance to hydrophobic agents such as azithromycin, and penB mutations that reduce porin permeability to hydrophilic agents such as tetracycline. Moreover, this strain contained gyrA and parC mutations that confer high-level resistance to ciprofloxacin. These results indicate the emergence of a N. gonorrhoeae strain with reduced susceptibility to ceftriaxone, which also showed a multidrug-resistant phenotype that can be explained by the presence of multiple loci mutations associated with antibiotic resistance.

The TetR family of transcriptional repressors

We have developed a general profile for the proteins of the TetR family of repressors. The stretch that best defines the profile of this family is made up of 47 amino acid residues that correspond to the helix-turn-helix DNA binding motif and adjacent regions in the three-dimensional structures of TetR, QacR, CprB, and EthR, four family members for which the function and three-dimensional structure are known. We have detected a set of 2,353 nonredundant proteins belonging to this family by screening genome and protein databases with the TetR profile. Proteins of the TetR family have been found in 115 genera of gram-positive, alpha-, beta-, and gamma-proteobacteria, cyanobacteria, and archaea. The set of genes they regulate is known for 85 out of the 2,353 members of the family. These proteins are involved in the transcriptional control of multidrug efflux pumps, pathways for the biosynthesis of antibiotics, response to osmotic stress and toxic chemicals, control of catabolic pathways, differentiation processes, and pathogenicity. The regulatory network in which the family member is involved can be simple, as in TetR (i.e., TetR bound to the target operator represses tetA transcription and is released in the presence of tetracycline), or more complex, involving a series of regulatory cascades in which either the expression of the TetR family member is modulated by another regulator or the TetR family member triggers a cell response to react to environmental insults. Based on what has been learned from the cocrystals of TetR and QacR with their target operators and from their three-dimensional structures in the absence and in the presence of ligands, and based on multialignment analyses of the conserved stretch of 47 amino acids in the 2,353 TetR family members, two groups of residues have been identified. One group includes highly conserved positions involved in the proper orientation of the helix-turn-helix motif and hence seems to play a structural role. The other set of less conserved residues are involved in establishing contacts with the phosphate backbone and target bases in the operator. Information related to the TetR family of regulators has been updated in a database that can be accessed at www.bactregulators.org.

Surveillance systems for STIs in the European Union: facing a changing epidemiology

OBJECTIVES

To characterise the nature, content, and performance characteristics of existing national STI surveillance systems in the European Union (EU) and Norway, to facilitate collection of comparable surveillance data.

METHODS

Cross sectional survey using a structured questionnaire.

RESULTS

Case reporting from clinicians and/or laboratories is the mainstay of EU surveillance systems for bacterial STIs. Coverage of case reporting varies from less than 10% to over 75%, and lack of and/or heterogeneity in case definitions affect the relative specificity and sensitivity of reporting systems. Considerable variations also exist in STI care sites; the populations who use these services; and in partner notification practices, STI screening practices, and STI laboratory diagnostic tests employed, affecting the representativeness of reported data and the sensitivity of surveillance systems for detecting the true number of STI cases.

CONCLUSIONS

The heterogeneity of current surveillance systems complicates direct comparison of STI incidence rates across Europe. Introduction of standardised case definitions for reporting, and increased coverage of mandatory reporting systems where necessary, are needed. Definition of standardised minimum datasets and use of sentinel and enhanced surveillance systems to supplement universal case/laboratory notification data, could improve our understanding of the distribution and determinants of STIs across Europe, and aid in the design of effective public health responses. In the context of the changing epidemiology of STIs, systems for detection and monitoring of localised outbreaks of acute bacterial STIs (syphilis and antimicrobial resistant gonorrhoea), as well as prevalence monitoring systems for frequently asymptomatic STIs (chlamydial infection and viral STIs), are also necessary.

High Occurrence of Simultaneous Mutations in Target Enzymes and MtrRCDE Efflux System in Quinolone-Resistant Neisseria gonorrhoeae

BACKGROUND

Emergence of multidrug-resistant Neisseria gonorrhoeae resulting from new genetic mutations is a serious threat to controlling gonorrhea.

GOAL

To determine 1) antimicrobial susceptibilities and the corresponding genetic mutations and 2) the role of MtrRCDE efflux system in gonococcal resistance to fluoroquinolones.

STUDY DESIGN

Antimicrobial susceptibility testing and sequence analysis of gyrA, parC, and mtrR loci of 131 N. gonorrhoeae isolates from Japan.

RESULTS

The proportion of N. gonorrhoeae strains resistant and intermediate-resistant to antimicrobials was 25.2% and 48.9% for ciprofloxacin, 25.2% and 30.5% for ofloxacin, 12.2% and 53.4% for penicillin; and 17.6% and 51.1% for tetracycline, respectively. Strains were categorized into 22 mutation profiles, with GyrA-S91F/ParC-D86N/MtrR-G45D being the most predominant profile. The frequency of mutation in gyrA, parC, mtrR, and the mtrR promoter was 71%, 47.3%, 77.1%, and 23.7%, respectively. Seventy-one percent of strains carried mutations in both gyrA and mtrR.

CONCLUSION

This study reports simultaneous mutations in fluoroquinolone target enzymes and the MtrRCDE efflux system as a fluoroquinolone-resistant mechanism in N. gonorrhoeae.

Overexpression of the MtrC-MtrD-MtrE efflux pump due to an mtrR mutation is required for chromosomally mediated penicillin resistance in Neisseria gonorrhoeae

The importance of the mtrCDE-encoded efflux pump in conferring chromosomally mediated penicillin resistance on certain strains of Neisseria gonorrhoeae was determined by using genetic derivatives of penicillin-sensitive strain FA19 bearing defined mutations (mtrR, penA, and penB) donated by a clinical isolate (FA6140) expressing high-level resistance to penicillin and antimicrobial hydrophobic agents (HAs). When introduced into strain FA19 by transformation, a single base pair deletion in the mtrR promoter sequence from strain FA6140 was sufficient to provide high-level resistance to HAs (e.g., erythromycin and Triton X-100) but only a twofold increase in resistance to penicillin. When subsequent mutations in penA and porIB were introduced from strain FA6140 into strain WV30 (FA19 mtrR) by transformation, resistance to penicillin increased incrementally up to a MIC of 1.0 micro g/ml. Insertional inactivation of the gene (mtrD) encoding the membrane transporter component of the Mtr efflux pump in these transformant strains and in strain FA6140 decreased the MIC of penicillin by 16-fold. Genetic analyses revealed that mtrR mutations, such as the single base pair deletion in its promoter, are needed for phenotypic expression of penicillin and tetracycline resistance afforded by the penB mutation. As penB represents amino acid substitutions within the third loop of the outer membrane PorIB protein that modulate entry of penicillin and tetracycline, the results presented herein suggest that PorIB and the MtrC-MtrD-MtrE efflux pump act synergistically to confer resistance to these antibiotics.