Decreased affinity of mosaic-structure recombinant penicillin-binding protein 2 for oral cephalosporins in Neisseria gonorrhoeae

Antimicrobial susceptibility of commensal Neisseria species in the Japanese population

OBJECTIVES

We aimed to, for the first time, characterize the antimicrobial susceptibilities of commensal Neisseria species in the general population in Japan. In particular, we assessed if the tetracycline minimum inhibitory concentrations (MICs) of these isolates were changing over time and, given the recent interest in doxycycline post exposure prophylaxis (PEP), if the tetracycline MICs were associated with those of the other antimicrobials.

METHODS

Neisseria spp. were isolated from 1679 patients visiting dental clinics in Japan between 2018 and 2023. The MICs of tetracycline, ceftriaxone, cefixime, penicillin, azithromycin and ciprofloxacin against Neisseria spp. were determined using agar dilution. Linear regression was used to assess if there was an association between MIC and the year the isolate was obtained from, controlling for species identity.

RESULTS

Neisseria spp. were detected in 424 of 1679 individuals sampled. Of these, 417 (98.3 %) isolates were identified as Neisseria subflava, and the remaining 7 (1.7 %) as Neisseria mucosa. The median tetracycline MIC was 0.5 mg/L (IQR 0.5-1 mg/L). The MICs of penicillin, cefixime, ceftriaxone and ciprofloxacin were lower in N. mucosa than in N. subflava. The tetracycline MICs of Neisseria spp. were positively correlated with penicillin, azithromycin and ciprofloxacin. No significant correlations were found with cefixime or ceftriaxone.

CONCLUSIONS

Our results suggest that despite the overall decline in antimicrobial use in Japan, MICs for several antimicrobials have increased over time. In particular, the MIC of tetracycline tends to be high in Japan. These results suggest the need to include surveillance of tetracycline MICs of commensal Neisseria spp. in doxycycline PEP implementation studies.

Differential contribution of PBP occupancy and efflux on the effectiveness of β-lactams at their target site in clinical isolates of Neisseria gonorrhoeae

Neisseria gonorrhoeae exhibits alarming antibiotic resistance trends and poses a significant challenge in therapeutic management. This study aimed to explore the association of penA alleles with penicillin-binding protein (PBP) occupancy patterns and reduced outer membrane permeability, impacting susceptibility to last-line cephalosporins and potential β-lactam candidates. The whole genome sequence, the MICs and PBP IC50s were determined for 12 β-lactams and β-lactamase inhibitors in 8 clinical isolates with varying β-lactam sensitivity, 2 ATCC, and 3 WHO cephalosporin-resistant reference strains. The genetic analysis identified diverse determinants of β-lactam resistance including penA, ponA, porB, and mtrR alterations. Mosaic penA alleles were confirmed to be key determinants of cephalosporin resistance, with notable impacts on PBP2 IC50 affinities (in the presence of all PBPs). Substitutions in positions V316 and A501 exhibited significant effects on β-lactam PBP2 occupancy and MICs. PBP1 inhibition showed marginal effect on β-lactam sensitivity and PBP3 acted as a sink target. Ertapenem and piperacillin emerged as potential therapies against cephalosporin-resistant N. gonorrhoeae strains, along with combination therapies involving tazobactam and/or efflux inhibitors. The study determined the β-lactam PBP-binding affinities of last-line cephalosporins and alternative β-lactam candidates in strains carrying different penA alleles for the first time. These findings provide insights for developing new antimicrobial agents and enhancers against emerging resistant strains. Further research is warranted to optimize therapeutic interventions for cephalosporin-resistant N. gonorrhoeae infections.

Affinity of β-Lactam Antibiotics for Neisseria gonorrhoeae Penicillin-Binding Protein 2 Having Wild, Cefixime-Reduced-Susceptible, and Cephalosporin (Ceftriaxone)-Resistant penA Alleles

Multidrug-resistant Neisseria gonorrhoeae is a serious concern worldwide. Resistance to β-lactam antibiotics occurs through mutations in penicillin-binding proteins (PBPs), acquisition of β-lactamases, and alteration of antibiotic penetration. Mosaic structures of penA, which encodes PBP2, play a major role in resistance to β-lactams, especially cephalosporins. Ceftriaxone (CRO) is recognized as the only satisfiable antibiotic for the treatment of gonococcal infections; however, CRO-resistant isolates have emerged in the community. Here, we examined the affinity of β-lactam antibiotics for recombinant PBP2 in a competition assay using fluorescence-labeled penicillin. We found no or little difference in the affinities of penicillins and meropenem (MEM) for PBP2 from cefixime (CFM)-reduced-susceptible strain and cephalosporin-resistant strain. However, the affinity of cephalosporins, including CRO, for PBP2 from the cephalosporin-resistant strain was markedly lower than that for PBP2 from the CFM-reduced-susceptible-resistant strain. Notably, piperacillin (PIP) showed almost the same affinity for PBP2 from penicillin-susceptible, CFM-reduced-susceptible, and cephalosporin (including CRO)-resistant strains. Thus, PIP/tazobactam and MEM are candidate antibiotics for the treatment of CRO-resistant/multidrug-resistant N. gonorrhoeae.

Antimicrobial resistance prediction in Neisseria gonorrhoeae: Current status and future prospects

INTRODUCTION

Several nucleic acid amplification tests (NAATs), mostly real-time PCRs, to detect antimicrobial resistance (AMR) determinants and predict AMR in Neisseria gonorrhoeae are promising, and some may be ready to apply at the point-of-care (POC), but important limitations remain with most NAATs. Next-generation sequencing (NGS) can overcome many of these limitations.Areas covered: Recent advances, with main focus on publications since 2017, in the development and use of NAATs and NGS to predict gonococcal AMR for surveillance and clinical use, and pros and cons of these tests as well as future perspectives for appropriate use of molecular AMR prediction for N. gonorrhoeae.Expert Commentary: NAATs and/or NGS for AMR prediction should supplement culture-based AMR surveillance, which will remain because it detects also AMR due to unknown AMR determinants, and translation into POC tests is imperative for the end-goal of individualized treatment, sparing ceftriaxone±azithromycin. Several challenges for direct testing of clinical, especially pharyngeal, specimens and for accurate prediction of cephalosporins and azithromycin resistance, especially using NAATs, remain. The choice of AMR prediction assay needs to carefully consider the intended use of the assay; limitations intrinsic to the AMR prediction technology, algorithms and specific to chosen methodology; specimen types analyzed; and cost-effectiveness.

RNA polymerase mutations cause cephalosporin resistance in clinical Neisseria gonorrhoeae isolates

Increasing Neisseria gonorrhoeae resistance to ceftriaxone, the last antibiotic recommended for empiric gonorrhea treatment, poses an urgent public health threat. However, the genetic basis of reduced susceptibility to ceftriaxone is not completely understood: while most ceftriaxone resistance in clinical isolates is caused by target site mutations in penA, some isolates lack these mutations. We show that penA-independent ceftriaxone resistance has evolved multiple times through distinct mutations in rpoB and rpoD. We identify five mutations in these genes that each increase resistance to ceftriaxone, including one mutation that arose independently in two lineages, and show that clinical isolates from multiple lineages are a single nucleotide change from ceftriaxone resistance. These RNA polymerase mutations cause large-scale transcriptional changes without altering susceptibility to other antibiotics, reducing growth rate, or deranging cell morphology. These results underscore the unexpected diversity of pathways to resistance and the importance of continued surveillance for novel resistance mutations.

Antimicrobial resistance (AMR) and molecular characterization of Neisseria gonorrhoeae in Ghana, 2012-2015

Neisseria gonorrhoeae antimicrobial resistance (AMR) surveillance is essential for tracking the emergence and spread of AMR strains in local, national and international populations. This is crucial for developing or refining treatment guidelines. N. gonorrhoeae multiantigen sequence typing (NG-MAST) is beneficial for describing the molecular epidemiology of gonococci at national and international levels. Elucidation of AMR determinants to β-lactam drugs, is a means of monitoring the development of resistance. In Ghana, little is known about the current gonococcal AMR prevalence and no characterization of gonococcal isolates has been previously performed. In this study, gonococcal isolates (n = 44) collected from five health facilities in Ghana from 2012 to 2015, were examined using AMR testing, NG-MAST and sequencing of penA. High rates of resistance were identified to tetracycline (100%), benzylpenicillin (90.9%), and ciprofloxacin (81.8%). One isolate had a high cefixime MIC (0.75 μg/ml). Twenty-eight NG-MAST sequence types (STs) were identified, seventeen of which were novel. The isolate with the high cefixime MIC contained a mosaic penA-34 allele and belonged to NG-MAST ST1407, an internationally spreading multidrug-resistant clone that has accounted for most cefixime resistance in many countries. In conclusion, AMR testing, NG-MAST, and sequencing of the AMR determinant penA, revealed high rates of resistance to tetracycline, benzylpenicillin, and ciprofloxacin; as well as a highly diverse population of N. gonorrhoeae in Ghana. It is imperative to continue with enhanced AMR surveillance and to understand the molecular epidemiology of gonococcal strains circulating in Ghana and other African countries.

Evaluation of Susceptibilities to Carbapenems and Faropenem Against Cephalosporin-Resistant Neisseria gonorrhoeae Clinical Isolates with penA Mosaic Alleles

Neisseria gonorrhoeae is a principal pathogen for sexually transmitted infections, especially for male urethritis. Currently, the prevalence of multidrug resistance is increasing. Carbapenems are broad-spectrum antimicrobials that are widely used in the clinical setting, especially for multidrug-resistant Gram-negative bacteria. However, susceptibility to carbapenems has not been well evaluated for cephalosporin-resistant N. gonorrhoeae isolates. In this study, we determined the susceptibility to a series of carbapenems (meropenem, imipenem, doripenem, and biapenem) and faropenem against cephalosporin-resistant (resistant to cefixime, but susceptible to ceftriaxone) and cephalosporin-susceptible N. gonorrhoeae clinical isolates. The gene mutations associated with β-lactam resistance were evaluated. All cephalosporin-resistant N. gonorrhoeae isolates possessed mosaic mutation alleles in penA (NG-STAR penA-10.001, 27.001, or 108.001). They exhibited a low minimum inhibitory concentration (MIC) (≤0.125 mg/L) for meropenem and markedly high MICs (0.5-2 mg/L) for other carbapenems and faropenem. The strongest association was observed between the mosaic alleles in penA and decreased susceptibility to carbapenems and faropenem compared with mutations in mtrR, porB, and ponA. These results suggest that meropenem may serve as an alternative therapeutic agent for cephalosporin-resistant N. gonorrhoeae with a mosaic allele in penA, whereas other carbapenems and faropenem may be ineffective.

Recent advances in the development and use of molecular tests to predict antimicrobial resistance in Neisseria gonorrhoeae

INTRODUCTION

The number of genetic tests, mostly real-time PCRs, to detect antimicrobial resistance (AMR) determinants and predict AMR in Neisseria gonorrhoeae is increasing. Several of these assays are promising, but there are important shortcomings and few assays have been adequately validated and quality assured. Areas covered: Recent advances, focusing on publications since 2012, in the development and use of molecular tests to predict gonococcal AMR for surveillance and for clinical use, advantages and disadvantages of these tests and of molecular AMR prediction compared with phenotypic AMR testing, and future perspectives for effective use of molecular AMR tests for different purposes. Expert commentary: Several challenges for direct testing of clinical, especially extra-genital, specimens remain. The choice of molecular assay needs to consider the assay target, quality controls, sample types, limitations intrinsic to molecular technologies, and specific to the chosen methodology, and the intended use of the test. Improved molecular- and particularly genome-sequencing-based methods will supplement AMR testing for surveillance purposes, and translate into point-of-care tests that will lead to personalized treatments, while sparing the last available empiric treatment option (ceftriaxone). However, genetic AMR prediction will never completely replace phenotypic AMR testing, which detects also AMR due to unknown AMR determinants.

Alanine 501 Mutations in Penicillin-Binding Protein 2 from Neisseria gonorrhoeae: Structure, Mechanism, and Effects on Cephalosporin Resistance and Biological Fitness

Resistance of Neisseria gonorrhoeae to expanded-spectrum cephalosporins such as ceftriaxone and cefixime has increased markedly in the past decade. The primary cephalosporin resistance determinant is a mutated penA gene, which encodes the essential peptidoglycan transpeptidase, penicillin-binding protein 2 (PBP2). Decreased susceptibility and resistance can be conferred by mosaic penA alleles containing upward of 60 amino acid changes relative to wild-type PBP2, or by nonmosaic alleles with relatively few mutations, the most important of which occurs at Ala501 located near the active site of PBP2. Recently, fully cefixime- and ceftriaxone-resistant clinical isolates that harbored a mosaic penA allele with an A501P mutation were identified. To examine the potential of mutations at Ala501 to increase resistance to expanded-spectrum cephalosporins, we randomized codon 501 in a mosaic penA allele and transformed N. gonorrhoeae to increased cefixime resistance. Interestingly, only five substitutions of Ala501 (A501V, A501T, A501P, A501R, and A501S) that increased resistance and preserved essential transpeptidase function were isolated. To understand their structural implications, these mutations were introduced into the nonmosaic PBP2-6140CT, which contains four C-terminal mutations present in PBP2 from the penicillin-resistant strain FA6140. The crystal structure of PBP2-6140CT-A501T was determined and revealed ordering of a loop near the active site and a new hydrogen bond involving Thr501 that connects the loop and the SxxK conserved active site motif. The structure suggests that increased rigidity in the active site region is a mechanism for cephalosporin resistance mediated by Ala501 mutations in PBP2.

Antimicrobial resistance in Neisseria gonorrhoeae in the 21st century: past, evolution, and future

Neisseria gonorrhoeae is evolving into a superbug with resistance to previously and currently recommended antimicrobials for treatment of gonorrhea, which is a major public health concern globally. Given the global nature of gonorrhea, the high rate of usage of antimicrobials, suboptimal control and monitoring of antimicrobial resistance (AMR) and treatment failures, slow update of treatment guidelines in most geographical settings, and the extraordinary capacity of the gonococci to develop and retain AMR, it is likely that the global problem of gonococcal AMR will worsen in the foreseeable future and that the severe complications of gonorrhea will emerge as a silent epidemic. By understanding the evolution, emergence, and spread of AMR in N. gonorrhoeae, including its molecular and phenotypic mechanisms, resistance to antimicrobials used clinically can be anticipated, future methods for genetic testing for AMR might permit region-specific and tailor-made antimicrobial therapy, and the design of novel antimicrobials to circumvent the resistance problems can be undertaken more rationally. This review focuses on the history and evolution of gonorrhea treatment regimens and emerging resistance to them, on genetic and phenotypic determinants of gonococcal resistance to previously and currently recommended antimicrobials, including biological costs or benefits; and on crucial actions and future advances necessary to detect and treat resistant gonococcal strains and, ultimately, retain gonorrhea as a treatable infection.

Emergence of multidrug-resistant, extensively drug-resistant and untreatable gonorrhea

The new superbug Neisseria gonorrhoeae has retained resistance to antimicrobials previously recommended for first-line treatment and has now demonstrated its capacity to develop resistance to the extended-spectrum cephalosporin, ceftriaxone, the last remaining option for first-line empiric treatment of gonorrhea. An era of untreatable gonorrhea may be approaching, which represents an exceedingly serious public health problem. Herein, we review the evolution, origin and spread of antimicrobial resistance and resistance determinants (with a focus on extended-spectrum cephalosporins) in N. gonorrhoeae, detail the current situation regarding verified treatment failures with extended-spectrum cephalosporins and future treatment options, and highlight essential actions to meet the large public health challenge that arises with the possible emergence of untreatable gonorrhea. Essential actions include: implementing action/response plans globally and nationally; enhancing surveillance of gonococcal antimicrobial resistance, treatment failures and antimicrobial use/misuse; and improving prevention, early diagnosis and treatment of gonorrhea. Novel treatment strategies, antimicrobials (or other compounds) and, ideally, a vaccine must be developed.

Mechanisms of the formation of Neisseria gonorrhoeae resistance to cephalosporins

The authors provide a review of the present-day literature data on the issues of studying the mechanisms of the formation of Neisseria gonorrhoeae resistance to third-generation cephalosporins. Studies in this field are needed in connection with the occurrence of strains resistant to third-generation cephalosporins as well as low-sensitivity strains. The authors emphasize the importance of mutations in porB, penA, mtrR, penB and ponA genes in the development of Neisseria gonorrhoeae resistance to β-lactam antibiotics and describe the prospects of studying the mosaic structure of the penA gene encoding the РВР2 protein as well as spatial structure of this protein.

High-throughput screening for novel inhibitors of Neisseria gonorrhoeae penicillin-binding protein 2

The increasing prevalence of N. gonorrhoeae strains exhibiting decreased susceptibility to third-generation cephalosporins and the recent isolation of two distinct strains with high-level resistance to cefixime or ceftriaxone heralds the possible demise of β-lactam antibiotics as effective treatments for gonorrhea. To identify new compounds that inhibit penicillin-binding proteins (PBPs), which are proven targets for β-lactam antibiotics, we developed a high-throughput assay that uses fluorescence polarization (FP) to distinguish the fluorescent penicillin, Bocillin-FL, in free or PBP-bound form. This assay was used to screen a 50,000 compound library for potential inhibitors of N. gonorrhoeae PBP 2, and 32 compounds were identified that exhibited >50% inhibition of Bocillin-FL binding to PBP 2. These included a cephalosporin that provided validation of the assay. After elimination of compounds that failed to exhibit concentration-dependent inhibition, the antimicrobial activity of the remaining 24 was tested. Of these, 7 showed antimicrobial activity against susceptible and penicillin- or cephalosporin-resistant strains of N. gonorrhoeae. In molecular docking simulations using the crystal structure of PBP 2, two of these inhibitors docked into the active site of the enzyme and each mediate interactions with the active site serine nucleophile. This study demonstrates the validity of a FP-based assay to find novel inhibitors of PBPs and paves the way for more comprehensive high-throughput screening against highly resistant strains of N. gonorrhoeae. It also provides a set of lead compounds for optimization of anti-gonococcal agents.

Analysis of mutations in multiple loci of Neisseria gonorrhoeae isolates reveals effects of PIB, PBP2 and MtrR on reduced susceptibility to ceftriaxone

OBJECTIVES

To elucidate loci in Neisseria gonorrhoeae implicated in reduced susceptibility to ceftriaxone.

METHODS

N. gonorrhoeae isolates were collected in Shanghai, China, in 2005 and 2008. Twenty-eight isolates with reduced susceptibility to ceftriaxone (CRO(Red); MIC = 0.125-0.25 mg/L) were studied for mutations in PorB (porB), MtrR (mtrR), PBP2 (penA) and PBP1 (ponA). The mutation profiles of the 28 CRO(Red) isolates were compared with those of 32 ceftriaxone-susceptible isolates (CRO(S); MIC = 0.004-0.016 mg/L). porB-based DNA sequence typing and N. gonorrhoeae multi-antigen sequence typing (NG-MAST) analyses were performed.

RESULTS

Significantly more CRO(Red) isolates (89.3%) exhibited a PIB phenotype as compared with the CRO(S) isolates (59.4%) (P = 0.02). Double mutations (G45D/H105Y or A39T/H105Y) in MtrR were associated with CRO(Red) phenotypes. A 'wild-type' MtrR protein characterized CRO(Red) isolates (50.0%, 14/28), while a single H105Y mutation was observed only in CRO(S) isolates (43.8%, 14/32). Both CRO(Red) and CRO(S) isolates carried an '-A' deletion in the mtrR promoter. Six of 15 mutation patterns observed in PBP2 were new. Mutation patterns XIII (17.9% of CRO(Red) isolates) and XVII or XVIII (25.0% of CRO(Red) isolates) of PBP2 comprised A501V/G542S or A501V/P551S double mutations and were associated with a CRO(Red) phenotype. The mosaic PBP2 (pattern X) was not observed. The L421P mutation in PBP1 was observed in all CRO(Red) and in 97.0% of CRO(S) isolates. CRO(Red) isolates were non-clonal.

CONCLUSIONS

Reduced susceptibility to ceftriaxone in N. gonorrhoeae is mediated by porB1b alleles and is associated with specific mutations in PBP2 and in the DNA binding and dimerization domains of MtrR.

A duplex PCR method to identify mosaic penA gene and predict reduced susceptibility to oral cephalosporins in Neisseria gonorrhoeae

Neisseria gonorrhoeae with mosaic penicillin-binding protein 2 (PBP2) is associated with reduced susceptibility to third-generation oral cephalosporins. A simple and rapid PCR method using three primers was designed to identify mosaic PBP2, which could help predict reduced susceptibility to expanded-spectrum cephalosporins in N. gonorrhoeae.

Meeting the public health challenge of multidrug- and extensively drug-resistant Neisseria gonorrhoeae

Globally, antimicrobial resistance (AMR) in Neisseria gonorrhoeae is increasing in prevalence, both within and across antibiotic classes, including extended-spectrum cephalosporins, raising concerns that gonorrhea may become untreatable in certain circumstances. The AMR surveillance that is essential to optimize standard treatments is often lacking or of poor quality in countries with high disease rates. Recent initiatives by the WHO to enhance global AMR surveillance that focus on multidrug- and extensively drug-resistant N. gonorrhoeae through revision of surveillance standards and use of a new panel of N. gonorrhoeae control strains are described. Keys to meeting these new challenges posed by gonococcal AMR remain the reduction in global burden of gonorrhea combined with implementation of wider strategies for general AMR control, and better understanding of mechanisms of emergence and spread of AMR.

Genetics of chromosomally mediated intermediate resistance to ceftriaxone and cefixime in Neisseria gonorrhoeae

All strains of Neisseria gonorrhoeae with reduced susceptibility to ceftriaxone and cefixime (cephalosporin-intermediate-resistant [Ceph(i)] strains) contain a mosaic penA allele encoding penicillin-binding protein 2 (PBP 2) with nearly 60 amino acid differences compared to the sequence of wild-type PBP 2, together with a set of resistance determinants (i.e., mtrR, penB, and/or ponA1) that are required for high-level penicillin resistance. To define the individual contributions of these determinants to reduced susceptibility to ceftriaxone and cefixime, we created isogenic strains containing the mosaic penA allele from the Ceph(i) strain 35/02 (penA35) together with one or more of the other resistance determinants and determined the MICs of penicillin G, ceftriaxone, and cefixime. The majority of cefixime resistance is conferred by the penA35 allele, with only a small contribution coming from mtrR and penB, whereas ceftriaxone resistance is nearly equally dependent upon mtrR and penB. Unlike high-level penicillin resistance, the ponA1 allele does not appear to be important for Ceph(i). A strain containing all four determinants has increased resistance to ceftriaxone and cefixime but not to the levels that the donor Ceph(i) strain does, suggesting that Ceph(i) strains, similar to high-level-penicillin-resistant strains, contain an additional unknown determinant that is required to reach donor levels of resistance. Our data also suggest that the original Ceph(i) strains arose from the transformation of penA genes from commensal Neisseria species into a penicillin-resistant strain already harboring mtrR, penB, ponA1, and the unknown gene(s) involved in high-level penicillin resistance.

The use of cephalosporins for gonorrhea: the impending problem of resistance

Gonorrhea remains an important clinical and public health problem throughout the world. Gonococcal infections have historically been diagnosed by Gram stain and culture but are increasingly diagnosed through nucleic acid tests, thereby eliminating the opportunity for antimicrobial susceptibility testing. Gonococcal infections are typically treated with single-dose therapy with an agent found to cure > 95% of cases. Unfortunately, the gonococcus has repeatedly developed resistance to antimicrobials including sulfonamides, penicillin, tetracyclines and fluoroquinolones. This has now left third-generation cephalosporins as the lone class of antimicrobials recommended as first-line therapy for gonorrhea in some regions. However, resistance to oral third-generation cephalosporins has emerged and spread in Asia, Australia and elsewhere. The mechanism of this resistance seems to be associated with a mosaic penicillin binding protein (penA) in addition to other chromosomal mutations previously found to confer resistance to beta-lactam antimicrobials (ponA, mtrR, penB, pilQ). Few good options exist or are in development for treating cephalosporin-resistant isolates, as most have had multidrug resistance. Preventing the spread of resistant isolates will depend on ambitious antimicrobial management programs, strengthening and expanding surveillance networks, and through effective sexually transmitted disease control and prevention.

Genotyping as a tool for antibiotic resistance surveillance of Neisseria gonorrhoeae in New Caledonia: evidence of a novel genotype associated with reduced penicillin susceptibility

Antibiotic resistance in Neisseria gonorrhoeae continues to be a major concern in public health. Resistance of N. gonorrhoeae bacteria to penicillin G is widespread in most developed countries, which has necessitated a change to newer drugs for treatment of gonococcal infections. Recent reports indicate that resistance to these newer drugs is increasing, highlighting the need for accurate therapeutic recommendations. In some countries or communities, however, N. gonorrhoeae isolates are still susceptible to penicillin, so the use of this antibiotic for single-dose treatments of medically under-resourced patients is beneficial. In order to evaluate the adequacy and sustainability of this treatment approach, we explored the presence and prevalence of chromosomally mediated resistance determinants in N. gonorrhoeae isolates collected from 2005 to 2007 in New Caledonia. We developed two new real-time PCR assays targeting the penB and mtrR determinants, to be used together with a previously described duplex assay targeting the penA and ponA determinants. The results of this study provided evidence that neither the most-common mtrR determinants nor the most-resistance-associated penB alleles are currently circulating in New Caledonia, suggesting that penicillin should still be considered a valuable treatment strategy. Additionally, using our genotyping assay, we observed an unexpected penB genotype at a relatively high frequency that was associated with a decreased susceptibility to penicillin (average MIC, 0.15 mug/ml). Sequencing revealed that this genotype corresponded to an A102S mutation in the penB gene. The molecular tools developed in this study can be used successfully for prospective epidemiological monitoring and surveillance of penicillin susceptibility.

Rapid detection of the mosaic structure of the Neisseria gonorrhoeae penA Gene, which is associated with decreased susceptibilities to oral cephalosporins

In Neisseria gonorrhoeae, the mosaic structure of the penA gene (encoding penicillin-binding protein 2 [PBP 2]), which is composed of fragments of the penA genes from Neisseria cinerea and Neisseria perflava, has been significantly associated with decreased susceptibility to cephalosporins, particularly oral cephalosporins. The aim of this study was to develop a rapid assay for the detection of mosaic PBP 2 of N. gonorrhoeae by real-time PCR. This assay successfully detected the mosaic penA gene of N. gonorrhoeae, and its sensitivity was >or=10(1) copies/reaction. Six hundred twenty-one clinical strains were examined by this assay for the presence of mosaic PBP 2, which was detected in 85 (39.4%) of 216 strains from 2002, 69 (40.6%) of 170 strains from 2003, 71 (44.4%) of 160 strains from 2004, and 31 (41.3%) of 75 strains from 2005. The MICs of cephalosporins for strains with the mosaic PBP 2 detected by the assay were statistically higher than those for strains without the mosaic PBP 2. One hundred sixty-six (64.8%) of 256 strains with the mosaic PBP 2 exhibited cefixime MICs of >or=0.5 microg/ml. The emergence and spread of strains with mosaic PBP 2 could be a threat to the cefixime treatment of gonorrhea. This real-time PCR assay for the detection of mosaic PBP 2 of N. gonorrhoeae is thus useful in the prediction of decreased susceptibilities to oral cephalosporins.