Trends in antimicrobial resistance in Neisseria gonorrhoeae isolated in Canada: 2000-2009

Multiplex real-time PCR assays for the prediction of cephalosporin, ciprofloxacin and azithromycin antimicrobial susceptibility of positive Neisseria gonorrhoeae nucleic acid amplification test samples

BACKGROUND

The incidence of antimicrobial-resistant Neisseria gonorrhoeae (GC) is rising in Canada; however, antimicrobial resistance (AMR) surveillance data are unavailable for infections diagnosed directly from clinical specimens by nucleic acid amplification tests (NAATs), representing over 80% of diagnoses. We developed a set of 10 improved molecular assays for surveillance of GC-AMR and prediction of susceptibilities in NAAT specimens.

METHODS

Multiplex real-time PCR (RT-PCR) assays were developed to detect SNPs associated with cephalosporin (ponA, porB, mtrR -35delA, penA A311V, penA A501, N513Y, G545S), ciprofloxacin (gyrA S91, parC D86/S87/S88) and azithromycin [23S (A2059G, C2611T), mtrR meningitidis-like promoter] resistance. The assays were validated on 127 gonococcal isolates, 51 non-gonococcal isolates and 50 NAATs with matched culture isolates. SNPs determined from the assay were compared with SNPs determined from in silico analysis of WGS data. MICs were determined for culture isolates using the agar dilution method.

RESULTS

SNP analysis of the 50 NAAT specimens had 96% agreement with the matched culture RT-PCR analysis. When compared with MICs, presence of penA A311V or penA A501 and two or more other SNPs correlated with decreased susceptibility and presence of three or more other SNPs correlated with intermediate susceptibility to cephalosporins; presence of any associated SNP correlated with ciprofloxacin or azithromycin resistance. NAAT-AMR predictions correlated with matched-culture cephalosporin, ciprofloxacin and azithromycin MICs at 94%, 100% and 98%, respectively.

CONCLUSIONS

We expanded molecular tests for N. gonorrhoeae AMR prediction by adding new loci and multiplexing reactions to improve surveillance where culture isolates are unavailable.

Versatile Electrochemical Sensing Platform for Bacteria

Bacterial infections present one of the leading causes of mortality worldwide, resulting in an urgent need for sensitive, selective, cost-efficient, and easy-to-handle technologies to rapidly detect contaminations and infections with pathogens. The presented research reports a fully functional chemical-detection principle, addressing all of the above-mentioned requirements for a successful biosensing device. With the examples of Escherichia coli and Neisseria gonorrheae, we present an electrochemical biosensor based on the bacterial expression of cytochrome c oxidase for the selective detection of clinically relevant concentrations within seconds after pathogen immobilization. The generality of the biochemical reaction, as well as the easy substitution of target-specific antibodies make this concept applicable to a large number of different pathogenic bacteria. The successful transfer of this semidirect detection principle onto inexpensive, screen-printed electrodes for portable devices represents a potential major advance in the field of biosensor development.

A Comparison of Real-Time Polymerase Chain Reaction Assays for the Detection of Antimicrobial Resistance Markers and Sequence Typing From Clinical Nucleic Acid Amplification Test Samples and Matched Neisseria gonorrhoeae Culture

Real-time polymerase chain reaction (PCR) assays to detect antimicrobial resistance-associated mutations were tested on Neisseria gonorrhoeae-positive clinical samples with matched isolates. Of the nucleic acid amplification tests/cultures, 87.7% (64/73), 98.6% (72/73), and 98.4% (62/63) predicted cephalosporin, ciprofloxacin, and azithromycin susceptibilities, respectively. N. gonorrhoeae multiantigen sequence type was correctly predicted for 98.7% (79/80), and 13 of 58 N. gonorrhoeae-negative specimens showed false-positive results.

High levels of susceptibility to new and older antibiotics in Neisseria gonorrhoeae isolates from Saskatchewan (2003-15): time to consider point-of-care or molecular testing for precision treatment?

Objectives

The antimicrobial susceptibility of Neisseria gonorrhoeae isolates from Saskatchewan was determined retrospectively (2003-15) to ascertain temporal trends to both current and older antimicrobials used for treatment.

Method

The agar dilution method was used to test the antimicrobial susceptibilities of 685 isolates to seven antibiotics.

Results

Over the period, only three (0.4%) gonococcal isolates had reduced susceptibility to cefixime and/or ceftriaxone. All isolates were susceptible to spectinomycin. Over 95% of the isolates tested were susceptible to azithromycin except in 2010 and 2013 (27.6% and 7.2% resistant, respectively). One isolate was resistant to both azithromycin and cefixime. Ciprofloxacin resistance was seen in < 5% of isolates prior to 2010, but in > 5% thereafter. From 2006 to 2012, and in 2015, penicillin resistance was detected in < 5% (0%-4.0%) of isolates, but in > 5% for the rest of the study period. Tetracycline resistance remained >5% (11.8%-89.1%) throughout the study. Plasmid-mediated resistance to tetracycline fluctuated between 0% and 17.5% of isolates tested. Four isolates were MDR and two isolates were XDR.

Conclusions

N. gonorrhoeae isolates were largely susceptible (∼85%) to antibiotics no longer recommended for treatment, such as penicillin and ciprofloxacin. Gonorrhoea in Saskatchewan is primarily (>95%) diagnosed by nucleic acid amplification testing, which does not permit antimicrobial susceptibility testing. The development of molecular testing, or point-of-care tests, to evaluate antimicrobial susceptibility, would enhance knowledge of true levels of resistance and allow discretion as to whether older but still effective antibiotics could be used in individual patient care.

Surveillance of the Antimicrobial Susceptibility of Neisseria gonorrhoeae Isolates Collected in Changsha, China from 2003 to 2015

A total of 1,294 Neisseria gonorrhoeae isolates obtained in Changsha, China from 2003 to 2015 were examined for their susceptibility to penicillin (PEN), ciprofloxacin (CIP), spectinomycin (SPT), and ceftriaxone (CRO) using the disc diffusion method. In addition, the minimum inhibitory concentrations (MICs) of CRO for 460 isolates collected during 2008-2015 was determined by agar dilution method. Isolates with intermediate CRO susceptibility were additionally tested for azithromycin susceptibility. Results demonstrated that the rate of resistance to PEN and CIP were 77.5 % and 94.2 %, respectively. Only 4 SPT-resistant and 2 SPT-intermediate isolates were identified. No CRO-resistant isolates were identified, although the percentage with intermediate susceptibility increased from 1.8% in 2012 to 11.9% in 2015. Among these, 3 isolates showed no susceptibility to azithromycin with 2 isolates showing an MIC of 0.5 μg/mL and 1 isolate showing an MIC of 1.0 μg/mL. We recommend azithromycin for treating strains that demonstrate intermediate susceptible to CRO and azithromycin-susceptible N. gonorrhoeae isolates occurring in Changsha.

Decline in Decreased Cephalosporin Susceptibility and Increase in Azithromycin Resistance in Neisseria gonorrhoeae, Canada

Antimicrobial resistance profiles were determined for Neisseria gonorrhoeae strains isolated in Canada during 2010–2014. The proportion of isolates with decreased susceptibility to cephalosporins declined significantly between 2011 and 2014, whereas azithromycin resistance increased significantly during that period. Continued surveillance of antimicrobial drug susceptibilities is imperative to inform treatment guidelines.

Molecular Assay for Detection of Ciprofloxacin Resistance in Neisseria gonorrhoeae Isolates from Cultures and Clinical Nucleic Acid Amplification Test Specimens

We developed a real-time PCR assay to detect single nucleotide polymorphisms associated with ciprofloxacin resistance in specimens submitted for nucleic acid amplification testing (NAAT). All three single nucleotide polymorphism (SNP) targets produced high sensitivity and specificity values. The presence of ≥2 SNPs was sufficient to predict ciprofloxacin resistance in an organism.

Molecular Assay for Detection of Genetic Markers Associated with Decreased Susceptibility to Cephalosporins in Neisseria gonorrhoeae

The incidence of antimicrobial-resistant Neisseria gonorrhoeae continues to rise in Canada; however, antimicrobial resistance data are lacking for approximately 70% of gonorrhea infections that are diagnosed directly from clinical specimens by nucleic acid amplification tests (NAATs). We developed a molecular assay for surveillance use to detect mutations in genes associated with decreased susceptibility to cephalosporins that can be applied to both culture isolates and clinical samples. Real-time PCR assays were developed to detect single nucleotide polymorphisms (SNPs) in ponA, mtrR, penA, porB, and one N. gonorrhoeae-specific marker (porA). We tested the real-time PCR assay with 252 gonococcal isolates, 50 nongonococcal isolates, 24 N. gonorrhoeae-negative NAAT specimens, and 34 N. gonorrhoeae-positive NAAT specimens. Twenty-four of the N. gonorrhoeae-positive NAAT specimens had matched culture isolates. Assay results were confirmed by comparison with whole-genome sequencing data. For 252 N. gonorrhoeae strains, the agreement between the DNA sequence and real-time PCR was 100% for porA, ponA, and penA, 99.6% for mtrR, and 95.2% for porB. The presence of ≥2 SNPs correlated with decreased susceptibility to ceftriaxone (sensitivities of >98%) and cefixime (sensitivities of >96%). Of 24 NAAT specimens with matched cultures, the agreement between the DNA sequence and real-time PCR was 100% for porB, 95.8% for ponA and mtrR, and 91.7% for penA. We demonstrated the utility of a real-time PCR assay for sensitive detection of known markers for the decreased susceptibility to cephalosporins in N. gonorrhoeae. Preliminary results with clinical NAAT specimens were also promising, as they correlated well with bacterial culture results.

Twenty-five-year changing pattern of gonococcal antimicrobial susceptibility in Shanghai: surveillance and its impact on treatment guidelines

Background

Antimicrobial resistance of Neisseria gonorrhoeae is a serious health problem in China. Gonococcal antimicrobial susceptibility has been monitored in Shanghai since 1988. In this study, we examined the changing pattern of gonococcal antimicrobial susceptibility based on data from N. gonorrhoeae isolates collected over the past 25 years.

Methods

Approximately 100–200 isolates each year (1988–2013) were tested for their susceptibility to penicillin (PEN), tetracycline (TET), ciprofloxacin (CIP), ceftriaxone (CRO) and spectinomycin (SPT), using the agar dilution method. Plasmid-mediated N. gonorrhoeae antimicrobial resistance, comprising penicillinase-producing N. gonorrhoeae (presumed PPNG) and high-level tetracycline resistance N. gonorrhoeae (presumed TRNG), were also determined. Breakpoints for susceptibilities followed those described by the Clinical and Laboratory Standard Institute and the European Committee on Antimicrobial Susceptibility Testing.

Results

A high proportion of isolates were resistant to PEN, TET and CIP, ranging from less than 20% at the beginning of the survey, increasing in the late 1990s and reaching over 90% in recent years. The proportion of isolates exhibiting plasmid-mediated resistance exceeded 38% for presumed PPNG and 20% for presumed TRNG in recent years. The proportion of CRO nonsusceptible isolates (MIC ≥ 0.125 mg/L) ranged from 7% to 13% in most of the study years. Almost all isolates were susceptible to SPT. The SPT MIC₉₀ was 16–32 mg/L for 2008–2013. The proportion of CRO nonsusceptible-associated multiple-drug-resistant (MDR) isolates was over 5% in most of the study years.

Conclusions

N. gonorrhoeae isolates in Shanghai were resistant to PEN, TET and CIP. Furthermore, CRO nonsusceptible and MDR isolates were prevalent. N. gonorrhoeae isolates were also found to be susceptible to SPT. It is recommended that the CRO dose be increased from currently recommended 250 mg to 500 mg and that SPT be an alternative in treating urogenital gonorrhea. Our findings highlight the importance of both regional and national surveillance programs for the prompt modification of treatment guidelines, vital in responding to the changing pattern of gonococcal antimicrobial susceptibility.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-014-0731-9) contains supplementary material, which is available to authorized users.

Antimicrobial susceptibility of Neisseria gonorrhoeae isolates from symptomatic men attending the Nanjing sexually transmitted diseases clinic (2011-2012): genetic characteristics of isolates with reduced sensitivity to ceftriaxone

BACKGROUND

Evolving gonococcal antimicrobial resistance (AMR) poses a serious threat to public health. The aim of this study was to: update antimicrobial susceptibility data of Neisseria gonorrhoeae recently isolated in Nanjing, China and identify specific deteminants of antimicrobial resistance and gentoypes of isolates with decreased sensitivity to ceftriaxone.

METHODS

334 N. gonorrhoeae isolates were collected consecutively from symptomatic men attending the Nanjing STD Clinic between April 2011 and December 2012. The minimum inhibitory concentrations (MICs) for penicillin, tetracycline, ciprofloxacin, spectinomycin and ceftriaxone were determined by agar plate dilution for each isolate. Penicillinase-producing N. gonorrhoeae (PPNG) and tetracycline-resistant N. gonorrhoeae (TRNG) were examined and typed for β-lactamase and tetM encoding plasmids respectively. Isolates that displayed elevated MICs to ceftriaxone (MIC ≥0.125 mg/L) were also tested for mutations in penA, mtrR, porB1b, ponA and pilQ genes and characterized by Neisseria gonorrhoeae multi-antigen sequence typing (NG-MAST).

RESULTS

98.8% (330/334) of N. gonorrhoeae isolates were resistant to ciprofloxacin; 97.9% (327/334) to tetracycline and 67.7% (226/334) to penicillin. All isolates were susceptible to ceftriaxone (MIC ≤0.25 mg/L) and spectinomycin (MIC ≤32 mg/L). Plasmid mediated resistance was exhibited by 175/334 (52%) of isolates: 120/334 (36%) of isolates were PPNG and 104/334 (31%) were TRNG. 90.0% (108/120) of PPNG isolates carried the Asia type β-lactamase encoding plasmid and 96% (100/104) of TRNG isolates carried the Dutch type tetM containing plasmid. Elevated MICs for ceftriaxone were present in 15 (4.5%) isolates; multiple mutations were found in penA, mtrR, porB1b and ponA genes. The 15 isolates were distributed into diverse NG-MAST sequence types; four different non-mosaic penA alleles were identified, including one new type.

CONCLUSIONS

N. gonorrhoeae isolates in Nanjing generally retained similar antimicrobial resistance patterns to isolates obtained five years ago. Fluctuations in resistance plasmid profiles imply that genetic exchange among gonococcal strains is ongoing and is frequent. Ceftriaxone and spectinomycin remain treatments of choice of gonorrhea in Nanjing, however, decreased susceptibility to ceftriaxone and rising MICs for spectinomycin of N. gonorrhoeae isolates underscore the importance of maintaining surveillance for AMR (both phenotypic and genotypic).

Whole-genome phylogenomic heterogeneity of Neisseria gonorrhoeae isolates with decreased cephalosporin susceptibility collected in Canada between 1989 and 2013

A large-scale, whole-genome comparison of Canadian Neisseria gonorrhoeae isolates with high-level cephalosporin MICs was used to demonstrate a genomic epidemiology approach to investigate strain relatedness and dynamics. Although current typing methods have been very successful in tracing short-chain transmission of gonorrheal disease, investigating the temporal evolutionary relationships and geographical dissemination of highly clonal lineages requires enhanced resolution only available through whole-genome sequencing (WGS). Phylogenomic cluster analysis grouped 169 Canadian strains into 12 distinct clades. While some N. gonorrhoeae multiantigen sequence types (NG-MAST) agreed with specific phylogenomic clades or subclades, other sequence types (ST) and closely related groups of ST were widely distributed among clades. Decreased susceptibility to extended-spectrum cephalosporins (ESC-DS) emerged among a group of diverse strains in Canada during the 1990s with a variety of nonmosaic penA alleles, followed in 2000/2001 with the penA mosaic X allele and then in 2007 with ST1407 strains with the penA mosaic XXXIV allele. Five genetically distinct ESC-DS lineages were associated with penA mosaic X, XXXV, and XXXIV alleles and nonmosaic XII and XIII alleles. ESC-DS with coresistance to azithromycin was observed in 5 strains with 23S rRNA C2599T or A2143G mutations. As the costs associated with WGS decline and analysis tools are streamlined, WGS can provide a more thorough understanding of strain dynamics, facilitate epidemiological studies to better resolve social networks, and improve surveillance to optimize treatment for gonorrheal infections.

Using crude whole-genome assemblies of Neisseria gonorrhoeae as a platform for strain analysis: clonal spread of gonorrhea infection in Saskatchewan, Canada

Using crude whole-genome assemblies, we analyzed 25 isolates of Neisseria gonorrhoeae by using a high-resolution single nucleotide polymorphism (SNP) approach for nine housekeeping genes, characterizing penA alleles, and antimicrobial susceptibility phenotypes coupled with population structure analysis. Two clonal complexes, characterized by their spatial and geographical persistence, were identified. In addition, the clonal spread of penicillin-resistant/intermediate phenotypes and a novel introduction of the azithromycin resistance phenotype in Saskatchewan, Canada, were ascertained using this method.

Unique combined penA/mtrR/porB mutations and NG-MAST strain types associated with ceftriaxone and cefixime MIC increases in a 'susceptible' Neisseria gonorrhoeae population

OBJECTIVES

To determine which mutations in penA, mtrR and porB are implicated in increasing minimum MICs of ceftriaxone and cefixime in a susceptible gonococcal population and to ascertain associations with gonococcal strain types (STs).

METHODS

One hundred and forty-six Neisseria gonorrhoeae isolates formed two extended-spectrum cephalosporin susceptibility groups: group 1 isolates with cefixime and ceftriaxone MICs of 0.0005-0.016 mg/L; and group 2 isolates with cefixime MICs of 0.03-0.125 mg/L (n = 24) and ceftriaxone MICs of 0.03-0.06 mg/L (n = 23). Mutation patterns in penicillin-binding protein 2 (PBP2; penA), multiple transfer resistance repressor (MtrR; mtrR) and porin B (PorB; porB) were ascertained by DNA sequence and bioinformatic analysis. STs were determined using N. gonorrhoeae multiantigen sequence typing (NG-MAST).

RESULTS

Most isolates carried PBP2 mutation pattern IX (D345a, F504L, A510V, A516G and P551L; 50/146, 34.2%), a G45D substitution in MtrR (37.7%) and a wild-type (WT) sequence for PorB (43.2%). Group 2 gonococcal isolates were significantly associated with: penA pattern IX; dual mutations in the promoter (A-) and DNA dimerization domain (H105Y) of MtrR; and G120K;A121D substitutions in PorB. There were 50 combined penA/mtrR/porB mutation patterns, with corresponding patterns I/WT/WT and IX/G45D/G120K;A121D predominating. Gonococci susceptible to ceftriaxone and cefixime were significantly associated with NG-MAST ST 25 (33/36; 92%) and the combined penA/mtrR/porB mutation pattern I/WT/WT. No combined mutation pattern or specific ST was associated with elevated ceftriaxone MICs. NG-MAST ST 3654 was significantly associated with the pattern IX/G45D/G120K;A121D and cefixime group 2 isolates.

CONCLUSIONS

Specific single or combined mutation patterns in penA, mtrR and porB and specific STs were associated with differences in susceptibility to ceftriaxone and cefixime.

Molecular approaches to enhance surveillance of gonococcal antimicrobial resistance

The best available data indicate that the world is heading towards a pandemic of extensively drug-resistant Neisseria gonorrhoeae. At the same time, clinical microbiology laboratories have moved away from using culture-based methods to diagnose gonorrhoea, thus undermining our ability to detect antimicrobial resistance (AMR) using current technologies. In this Opinion article, we discuss the problem of N. gonorrhoeae AMR, particularly emerging resistance to the cephalosporin ceftriaxone, outline current concerns about the surveillance of N. gonorrhoeae AMR and propose the use of molecular methods on a large scale to systematically enhance surveillance.

Worldwide susceptibility rates of Neisseria gonorrhoeae isolates to cefixime and cefpodoxime: a systematic review and meta-analysis

BACKGROUND

Neisseria gonorrhoeae (NG) infection is a serious public health problem. The third-generation extended-spectrum cephalosporins (ESCs) have been used as the first-line treatment for NG infection for almost three decades. However, in recent years, treatment failures with the oral third-generation ESCs have been reported worldwide. This study aimed to estimate worldwide susceptibility rates of NG to cefixime and cefpodoxime by analyzing data from all relevant published studies.

METHODOLOGY/PRINCIPAL FINDINGS

Two researchers independently searched five databases to identify studies on susceptibilities of NG to cefixime and cefpodoxime published between January 1, 1984 and October 15, 2012. A fixed-effect model was used to perform group analysis, and a χ2 test was employed to make subgroup comparison. Publication bias was assessed with the Begg rank correlation test. The pooled susceptibility rate of NG isolates to cefixime was 99.8% (95% CI: 99.7%-99.8%). The cefixime susceptibility rate of NG isolates from men was significantly lower than that from patients without information of gender or from men and women; the susceptibility rate of NG isolates from Asia was significantly lower than that from other continents; and the susceptibility rate of NG isolates collected before or during 2003 was significantly higher than that after 2003. The pooled susceptibility rate of NG isolates to cefpodoxime was 92.8% (95% CI: 89.0%-95.3%), which was lower than that to cefixime (92.8% vs. 99.8%, χ2 = 951.809, P<0.01).

CONCLUSIONS

The susceptibility rate of NG isolates to cefixime varied with the gender of patients and geographical location from which NG isolates were collected, and declined with time. The reported lower susceptibility rate of NG isolates to cefixime and associated treatment failures, as well as the emergence of NG strains with cephalosporin resistance call for the more effective control of NG infection and the development of new antibiotics.

Two decades of the gonococcal antimicrobial surveillance program in South America and the Caribbean: challenges and opportunities

OBJECTIVES

The WHO has called for a global action plan to control the spread and impact of antibiotic resistant Neisseria gonorrhoeae. We report on key antimicrobial susceptibility (AMS) trends in countries in Latin America and the Caribbean from 1990 to 2011.

METHODS

Data collected between 1990 and 2011 by up to 23 countries in the Latin American and Caribbean region were aggregated and analysed for overall trends in N gonorrhoeae AMS to six antibiotics. Methods for gonococcal identification, susceptibility testing and interpretation were standardised.

RESULTS

More than 21 500 N gonorrhoeae isolates were tested for AMS between 1990 and 2011. The number of countries reporting yearly declined from 17 in the 1990 s to 7 in 2011. The first isolates (0.4%, 20/5171) with reduced susceptibility (minimum inhibitory concentration ≥ 0.125 mg/L) to ceftriaxone were reported between 2007 and 2011. Ciprofloxacin resistance, first noted in the mid-1990 s, ranged from 1.6% of isolates tested in 1997 rising to 42.1% in 2010. Overall, azithromycin resistance reached a high of 25.8% of isolates tested in 2008 falling to 1.0% in 2010. Resistance to penicillin ranged between 24.2% in 2003 to a high of 48.5% in 1993. Tetracycline resistance ranged between a high of 61.1% of isolates tested in 2001 to 21.8% in 2010. Plasmid mediated penicillin and tetracycline resistance declined over the period.

CONCLUSIONS

Gonococcal AMS surveillance initiatives are urgently needed in every country in the region to ensure that effective treatments for gonococcal infections are in place and to better understand emerging trends in gonococcal antimicrobial resistance.

Neisseria gonorrhoeae and extended-spectrum cephalosporins in California: surveillance and molecular detection of mosaic penA

BACKGROUND

The spread of Neisseria gonorrhoeae strains with mosaic penA alleles and reduced susceptibility to extended-spectrum cephalosporins is a major public health problem. While much work has been performed internationally, little is known about the genetics or molecular epidemiology of N. gonorrhoeae isolates with reduced susceptibility to extended-spectrum cephalosporins in the United States. The majority of N. gonorrhoeae infections are diagnosed without a live culture. Molecular tools capable of detecting markers of extended-spectrum cephalosporin resistance are needed.

METHODS

Urethral N. gonorrhoeae isolates were collected from 684 men at public health clinics in California in 2011. Minimum inhibitory concentrations (MICs) to ceftriaxone, cefixime, cefpodoxime and azithromycin were determined by Etest and categorized according to the U.S. Centers for Disease Control 2010 alert value breakpoints. 684 isolates were screened for mosaic penA alleles using real-time PCR (RTPCR) and 59 reactive isolates were subjected to DNA sequencing of their penA alleles and Neisseria gonorrhoeae multi-antigen sequence typing (NG-MAST). To increase the specificity of the screening RTPCR in detecting isolates with alert value extended-spectrum cephalosporin MICs, the primers were modified to selectively amplify the mosaic XXXIV penA allele.

RESULTS

Three mosaic penA alleles were detected including two previously described alleles (XXXIV, XXXVIII) and one novel allele (LA-A). Of the 29 isolates with an alert value extended-spectrum cephalosporin MIC, all possessed the mosaic XXXIV penA allele and 18 were sequence type 1407, an internationally successful strain associated with multi-drug resistance. The modified RTPCR detected the mosaic XXXIV penA allele in urethral isolates and urine specimens and displayed no amplification of the other penA alleles detected in this study.

CONCLUSION

N. gonorrhoeae isolates with mosaic penA alleles and reduced susceptibility to extended-spectrum cephalosporins are currently circulating in California. Isolates with the same NG-MAST ST, penA allele and extended-spectrum cephalosporin MICs have caused treatment failures elsewhere. The RTPCR assay presented here may be useful for the detection of N. gonorrheoae isolates and clinical specimens with reduced extended-spectrum cephalosporin MICs in settings where antimicrobial susceptibility testing is unavailable. In an era of increasing antimicrobial resistance and decreasing culture capacity, molecular assays capable of detecting extended-spectrum cephalosporin of resistance are essential to public health.

On the pathway to better birth outcomes? A systematic review of azithromycin and curable sexually transmitted infections

The WHO recommends the administration of sulfadoxine-pyrimethamine (SP) to all pregnant women living in areas of moderate (stable) to high malaria transmission during scheduled antenatal visits, beginning in the second trimester and continuing to delivery. Malaria parasites have lost sensitivity to SP in many endemic areas, prompting the investigation of alternatives that include azithromycin-based combination (ABC) therapies. Use of ABC therapies may also confer protection against curable sexually transmitted infections and reproductive tract infections (STIs/RTIs). The magnitude of protection at the population level would depend on the efficacy of the azithromycin-based regimen used and the underlying prevalence of curable STIs/RTIs among pregnant women who receive preventive treatment. This systematic review summarizes the efficacy data of azithromycin against curable STIs/RTIs.

Gonococcal endocarditis: a case report and review of the literature

A 59-year-old Caucasian male presented with progressive dyspnea, arthralgias and fever for three days. A diastolic regurgitation murmur was detected in the aortic area. A transesophageal echocardiograph showed several vegetations and severe aortic regurgitation. Blood cultures yielded Neisseria gonorrhoeae beta-lactamase negative. The patient had not noticed any urogenital discomfort or urethral discharge. The patient successfully underwent surgery for septal abscess debridement. The patient received ceftriaxone 2 g bid for eight weeks and the clinical follow-up was uneventful. The review of the literature revealed a total of the 38 additional cases reported between 1980 and the present. The majority of the patients were young, male and with native valve involvement. There has been a clear tendency for left-sided valve involvement (especially in the aortic valve). All valve cultures were reported negative despite, in most cases, the marked tissue destruction. Polymerase chain reaction was performed in two patients and positive results were shown in both. Cultures of exudates from other locations were negative in most cases. One striking fact is the high proportion of patients who underwent surgery (72 %). Information regarding antibiotic sensitivity was available in 28 cases, with penicillin resistance reported in six patients (21 %) and intermediate sensitivity in four patients (14 %). Resistance to ciprofloxacin was reported in two cases (7 %). A rapid increase and distribution of isolates resistant to third generation cephalosporins have been recently detected. The mortality is high, particularly taking into account that most were young patients who had not presented previous heart disease.

Utility of specimens positive for Neisseria gonorrhoeae by the Aptima Combo 2 assay for assessment of strain diversity and antibiotic resistance

In our jurisdiction, the Aptima Combo 2 assay (Gen-Probe, Inc.) is used to detect Neisseria gonorrhoeae from specimens collected at clinics for sexually transmitted infections (STI) and from select community patients. In addition, swabs are also collected for N. gonorrhoeae culture, susceptibility testing, and sequence typing (ST). Since only a small proportion of samples from provincial cases undergo culture, the available trends in antimicrobial susceptibility and predominant strain types may not be representative of all N. gonorrhoeae infections. Due to the limitations facing the use of N. gonorrhoeae culture to understand these trends in the general community, we performed a molecular analysis for markers of cephalosporin resistance and ST determination by using nucleic acid extracts of specimens sent for Aptima testing. Thirty-four samples submitted for both Aptima testing and N. gonorrhoeae culture from the same anatomic location (within 24 h) were included in the study. Sequence type was determined based on the sequence of the por and tbpB genes, and amino acid changes in the PBP 2 protein, encoded by the penA gene, were considered representative for the assessment of antimicrobial susceptibility. Sequence identity of 100% was observed between the sequences obtained from Aptima-analyzed samples and culture samples. Sequencing results showed an association between decreased susceptibility to extended-spectrum cephalosporins (ESC(ds)), tbp allele 110, ST 1407, and amino acid changes (G545S, I312M, and V316T) in the PBP 2 protein. Our data, generated based on a few representative genes, suggest that gonococcal samples positive by Aptima testing can be used to determine single nucleotide polymorphisms associated with ESC(ds) and the sequence type based on molecular strain typing. Confirmation of these findings may obviate the need for gonorrhea culture in the future.

Antimicrobial susceptibilities and distribution of sequence types of Neisseria gonorrhoeae isolates in Canada: 2010

The monitoring of antimicrobial susceptibilities in Neisseria gonorrhoeae isolates and characterization of N. gonorrhoeae multiantigen sequence types (NG-MAST, ST) provide important surveillance data as resistance rates continue to rise. A total of 2970 N. gonorrhoeae isolates were collected by Canadian provincial public health laboratories in 2010, and 1233 were submitted to the National Microbiology Laboratory for testing. The NG-MAST and minimum inhibitory concentration (MIC) by agar dilution were determined for each isolate. Of the 2970 isolates, 25.1% were resistant to penicillin, 34.6% resistant to tetracycline, 31.5% resistant to erythromycin, 35.9% resistant to ciprofloxacin, and 1.2% resistant to azithromycin. Decreased susceptibility to cefixime (MIC ≥ 0.25 mg/L) and ceftriaxone (MIC ≥ 0.125 mg/L) was identified in 3.2% and 7.3% of the isolates, respectively. The most common STs found in Canada were ST1407 (13.3%), ST3150 (11.3%), and ST3158 (9.0%), with 249 different STs identified among the isolates. Within the ST1407 group, 19.5% and 43.3% isolates have decreased susceptibility to cefixime and ceftriaxone, respectively. ST1407, the most prevalent NG-MAST in Canada in 2010, has been associated with high-level ceftriaxone MICs and with cefixime treatment failure cases worldwide. Identification and monitoring of STs and corresponding antimicrobial resistance profiles may be useful in surveillance programs and be used to inform public health actions.

Cephalosporin and azithromycin susceptibility in Neisseria gonorrhoeae isolates by site of infection, British Columbia, 2006 to 2011

BACKGROUND

Widespread resistance of Neisseria gonorrhoeae to penicillin, tetracycline, and fluoroquinolones has challenged effective treatment and control; recent international case reports of cefixime, ceftriaxone, and azithromycin resistance suggest that the remaining treatment options are now additionally threatened. To explore trends in antimicrobial susceptibility of N. gonorrhoeae, we reviewed provincial laboratory data from British Columbia, 2006 to 2011.

METHODS

Susceptibility testing was performed for all N. gonorrhoeae isolates detected in-house or forwarded to the reference laboratory. Resistance or intermediate resistance (nonsusceptibility) was defined by standard breakpoints for penicillin, tetracycline, ciprofloxacin, and spectinomycin. Elevated minimum inhibitory concentrations (MICs) at serial dilutions of 0.064 μg/mL or greater were explored for cefixime/ceftriaxone and 0.5 μg/mL or greater for azithromycin. Nonsusceptibility/elevated MIC was compared by year, site of infection, sex, and age.

RESULTS

A total of 1837 isolates representing 22% of all reported gonorrhea cases were analyzed. Nonsusceptibility to penicillin was established at baseline. Nonsusceptibility to tetracycline and ciprofloxacin increased over the study period, reaching 96% and 36%, respectively, in 2011. Sixteen isolates (1%) had a cefixime MIC of 0.25 μg/mL (none ≥0.5), none had a ceftriaxone MIC of 0.25 μg/mL or greater, and 15 (1%) had an azithromycin MIC of 2.0 μg/mL or greater. Elevated MIC of these agents showed an increasing trend over time. Nonsusceptibility and elevated MIC were consistently highest at the rectal and pharyngeal sites and higher in isolates from males, including when stratified to the pharyngeal site.

INTERPRETATION

Increases in elevated MIC of cefixime/ceftriaxone/azithromycin were superimposed on a background of established resistance to penicillin, tetracycline, and ciprofloxacin and may signal impending gonococcal resistance to first-line treatments. Ongoing surveillance will inform timely shifts in treatment recommendations.

The influence of target population on nonculture-based detection of markers of Neisseria gonorrhoeae antimicrobial resistance

BACKGROUND

With treatment options for gonorrhoea (Neisseria gonorrhoeae) diminishing, strengthening antimicrobial resistance (AMR) surveillance is paramount.

METHODS

In this study, we investigated polymerase chain reaction (PCR) based methods, in parallel with N. gonorrhoeae multi-antigen sequence typing (NG-MAST), for direct detection of four N. gonorrhoeae chromosomal mechanisms associated with emerging resistance to extended spectrum cephalosporins using noncultured samples: an adenine deletion in the mtrR promoter, a mosaic penicillin-binding protein (PBP) 2, an A501V PBP2 mutation, and alterations at positions 120 and 121 of the porB protein. The PCR assays were validated using a panel of characterised N. gonorrhoeae isolates (n=107) and commensal Neisseria (n=100) species. These PCR assays with NG-MAST were then applied to noncultured clinical specimens from distinct populations in Australia with differing levels of N. gonorrhoeae AMR: the Northern Territory (NT), where resistance has a low population prevalence, and Queensland (Qld), with higher AMR prevalence.

RESULTS

The real-time PCR assays proved highly sensitive and specific. When applied to the noncultured samples, only 1 out of 50 (2%) samples from NT harboured a resistant mechanism, whereas the Qld samples (n=129) collected over different periods showed progressive acquisition of resistant mechanisms, and these were associated with specific NG-MAST types, including Type 225.

CONCLUSIONS

The results suggest that our PCR-based methods could be used to rapidly pinpoint incursion of resistant strains into previously unaffected populations. Likewise, our results show that for molecular AMR surveillance, the population being investigated is as important as the genetic mechanisms being targeted.

Antimicrobial susceptibility and genetic characteristics of Neisseria gonorrhoeae isolates from Vietnam, 2011

BACKGROUND

Antimicrobial resistance (AMR) in Neisseria gonorrhoeae is a major public health concern worldwide. In Vietnam, knowledge regarding N. gonorrhoeae prevalence and AMR is limited, and data concerning genetic characteristics of N. gonorrhoeae is totally lacking. Herein, we investigated the phenotypic AMR (previous, current and possible future treatment options), genetic resistance determinants for extended-spectrum cephalosporins (ESCs), and genotypic distribution of N. gonorrhoeae isolated in 2011 in Hanoi, Vietnam.

METHODS

N. gonorrhoeae isolates from Hanoi, Vietnam isolated in 2011 (n = 108) were examined using antibiograms (Etest for 10 antimicrobials), Neisseria gonorrhoeae multi-antigen sequence typing (NG-MAST), and sequencing of ESC resistance determinants (penA, mtrR and penB).

RESULTS

The levels of in vitro resistance were as follows: ciprofloxacin 98%, tetracycline 82%, penicillin G 48%, azithromycin 11%, ceftriaxone 5%, cefixime 1%, and spectinomycin 0%. The MICs of gentamicin (0.023-6 mg/L), ertapenem (0.002-0.125 mg/L) and solithromycin (<0.016-0.25 mg/L) were relatively low. No penA mosaic alleles were found, however, 78% of the isolates contained an alteration of amino acid A501 (A501V (44%) and A501T (34%)) in the encoded penicillin-binding protein 2. A single nucleotide (A) deletion in the inverted repeat of the promoter region of the mtrR gene and amino acid alterations in MtrR was observed in 91% and 94% of the isolates, respectively. penB resistance determinants were detected in 87% of the isolates. Seventy-five different NG-MAST STs were identified, of which 59 STs have not been previously described.

CONCLUSIONS

In Vietnam, the highly diversified gonococcal population displayed high in vitro resistance to antimicrobials previously recommended for gonorrhoea treatment (with exception of spectinomycin), but resistance also to the currently recommended ESCs were found. Nevertheless, the MICs of three potential future treatment options were low. It is essential to strengthen the diagnostics, case reporting, and epidemiologic surveillance of gonorrhoea in Vietnam. Furthermore, the surveillance of gonococcal AMR and gonorrhoea treatment failures is imperative to reinforce. Research regarding novel antimicrobial treatment strategies (e.g., combination therapy) and new antimicrobials is crucial for future treatment of gonorrhoea.

Longitudinal analysis of the evolution and dissemination of Neisseria gonorrhoeae strains (Saskatchewan, Canada, 2005 to 2008) reveals three major circulating strains and convergent evolution of ciprofloxacin and azithromycin resistance

A longitudinal study combining multilocus sequence typing with molecular evolutionary analysis determined the distribution, population structure, and evolution of antibiotic resistance in Neisseria gonorrhoeae isolates in Saskatchewan that were collected between 2005 and 2008. Of 195 gonococcal isolates examined, 29 sequence types (STs) were identified with 3 major circulating strains (ST-1 through ST-3) comprising 52% of all gonococcal isolates studied. The prevalences, persistence, distribution patterns, and clonalities of these isolates strongly suggest that gonorrhea endemicity within this broad geographic region was driven by these 3 circulating strains. ST-1 exhibited a significantly (P = 0.001) higher prevalence throughout the study than did the others, accounting for ∼25% of the tested isolates each year. The spatial distributions of the gonococcal strains indicated that ST-1 in 2007 entered a linear component of the sexual network, reaching the remote north and resulting in the further spread and maintenance of infection. Ciprofloxacin and azithromycin resistances were observed in distantly related gonococcal lineages, clearly indicating the convergent acquisition of these antibiotic-resistant phenotypes. In addition, all ciprofloxacin- and azithromycin-resistant lineages were found at the edges of the minimum spanning tree, far from the major lineages, suggesting that these antibiotic phenotypes were most likely introduced into the province. In contrast, resistance to penicillin was found mostly in the endemic gonococcal lineages, suggesting that penicillin resistance was probably acquired in Saskatchewan as a result of spontaneous mutations in already-established lineages. Tetracycline resistance was present in all STs except one, indicating its ubiquitous nature in the gonococcal population studied.

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.

Genome sequencing of a Neisseria gonorrhoeae isolate of a successful international clone with decreased susceptibility and resistance to extended-spectrum cephalosporins

The recent emergence of Neisseria gonorrhoeae strains with decreased susceptibility to extended-spectrum cephalosporins is a major concern globally. We sequenced the genome of an N. gonorrhoeae multiantigen sequence typing (NG-MAST) ST1407 isolate (SM-3) with decreased susceptibility and resistance to oral extended-spectrum cephalosporins. The isolate was cultured in 2008 in San Francisco, CA, and possessed mosaic penA allele XXXIV, which is associated with an international clone that possesses decreased susceptibility as well as resistance to oral extended-spectrum cephalosporins globally. The genome sequence of strain NCCP11945 was used as a scaffold, and our assembly resulted in 91 contigs covering 2,029,064 bp (91%; >150× coverage) of the genome. Numerous instances of suspected horizontal genetic transfer events with other Neisseria species were identified, and two genes, opa and txf, acquired from nongonococcal Neisseria species, were identified. Strains possessing mosaic penA alleles (n = 108) and nonmosaic penA alleles (n = 169) from the United States and Europe (15 countries), cultured in 2002 to 2009, were screened for the presence of these genes. The opa gene was detected in most (82%) penA mosaic-containing isolates (mainly from 2007 to 2009) but not in any penA nonmosaic isolates. The txf gene was found in all strains containing opa but also in several (18%) penA nonmosaic strains. Using opa and txf as genetic markers, we identified a strain that possesses mosaic penA allele XXXIV, but the majority of its genome is not genetically related to strain SM-3. This implies that penA mosaic allele XXXIV was transferred horizontally. Such isolates also possessed decreased susceptibility and resistance to oral extended-spectrum cephalosporins. These findings support that genetic screening for particular penA mosaic alleles can be a valuable method for tracking strains with decreased susceptibility as well as resistance to oral extended-spectrum cephalosporins worldwide and that screening using only NG-MAST may not be sufficient.

Activity of JNJ-Q2, a novel fluoroquinolone, tested against Neisseria gonorrhoeae, including ciprofloxacin-resistant strains

JNJ-Q2 is a broad-spectrum fluoroquinolone with activity against Gram-positive and -negative pathogens. The in vitro activity of JNJ-Q2 was evaluated when tested against Neisseria gonorrhoeae isolates, including 31 ciprofloxacin-resistant strains with documented mutations in the quinolone resistance determining region. MIC values were determined using reference agar dilution methods using ciprofloxacin, penicillin, ceftriaxone, tetracycline, and azithromycin as comparators. All isolates were inhibited by ≤0.25 μg/mL of JNJ-Q2 (range, 0.004-0.25 μg/mL; MIC(50/90), 0.03/0.25 μg/mL) which was 8-fold (MIC(50)) and 32-fold more potent (MIC(90)) compared to ciprofloxacin. Few strains were susceptible to penicillin (3.0%) and tetracycline (6.1%), and with the use of the European Committee on Antimicrobial Susceptibility Testing interpretive criteria, 13.6% were resistant to azithromycin. All strains were susceptible to ceftriaxone, the most potent agent (MIC(90), 0.06 μg/mL) followed by JNJ-Q2 (MIC(90), 0.25 μg/mL). JNJ-Q2 appears to be a potent fluoroquinolone when tested against contemporary multidrug-resistant N. gonorrhoeae.

In vitro activity of ertapenem versus ceftriaxone against Neisseria gonorrhoeae isolates with highly diverse ceftriaxone MIC values and effects of ceftriaxone resistance determinants: ertapenem for treatment of gonorrhea?

Clinical resistance to the currently recommended extended-spectrum cephalosporins (ESCs), the last remaining treatment options for gonorrhea, is being reported. Gonorrhea may become untreatable, and new treatment options are crucial. We investigated the in vitro activity of ertapenem, relative to ceftriaxone, against N. gonorrhoeae isolates and the effects of ESC resistance determinants on ertapenem. MICs were determined using agar dilution technique or Etest for international reference strains (n = 17) and clinical N. gonorrhoeae isolates (n = 257), which included the two extensively drug-resistant (XDR) strains H041 and F89 and additional isolates with high ESC MICs, clinical ESC resistance, and other types of clinical high-level and multidrug resistance (MDR). Genetic resistance determinants for ESCs (penA, mtrR, and penB) were sequenced. In general, the MICs of ertapenem (MIC(50) = 0.032 μg/ml; MIC(90) = 0.064 μg/ml) paralleled those of ceftriaxone (MIC(50) = 0.032 μg/ml; MIC(90) = 0.125 μg/ml). The ESC resistance determinants mainly increased the ertapenem MIC and ceftriaxone MIC at similar levels. However, the MIC ranges for ertapenem (0.002 to 0.125 μg/ml) and ceftriaxone (<0.002 to 4 μg/ml) differed, and the four (1.5%) ceftriaxone-resistant isolates (MIC = 0.5 to 4 μg/ml) had ertapenem MICs of 0.016 to 0.064 μg/ml. Accordingly, ertapenem had in vitro advantages over ceftriaxone for isolates with ceftriaxone resistance. These in vitro results suggest that ertapenem might be an effective treatment option for gonorrhea, particularly for the currently identified ESC-resistant cases and possibly in a dual antimicrobial therapy regimen. However, further knowledge regarding the genetic determinants (and their evolution) conferring resistance to both antimicrobials, and clear correlates between genetic and phenotypic laboratory parameters and clinical treatment outcomes, is essential.

Outpatient parenteral antimicrobial therapy with ceftriaxone, a review

BACKGROUND

More than 30 years since it was developed for clinical use, the third-generation cephalosporin ceftriaxone remains the most commonly used agent for outpatient parental antimicrobial therapy (OPAT). Recent antimicrobial stewardship programmes have tended to restrict ceftriaxone use in hospitals to control antibiotic resistance and outbreaks of Clostridium difficle infection (CDI). Considering the expansion of OPAT programmes both in the UK and worldwide, revisiting the role of ceftriaxone in OPAT in the context of changing antimicrobial prescribing practices is timely.

AIM OF THE REVIEW

To identify the evidence base for OPAT, review current and historical data on indications for, and safety of ceftriaxone within the OPAT setting, and to provide some perspectives on the future role of ceftriaxone.

METHOD

We searched PubMed and Scopus for articles published in English, and hand searched reference lists. We also conducted a complementary descriptive analysis of prospectively acquired data on the use of ceftriaxone in more than 1,300 OPAT episodes over a 10-year period in our UK centre.

RESULTS

Ceftriaxone has an excellent safety profile in the OPAT setting, and its broad spectrum of activity makes it an established agent in a wide range of clinical infection syndromes, such as skin and soft-tissue infection, bone and joint infection, streptococcal endocarditis and several others. Intriguingly, in contrast to the inpatient setting, liberal use of ceftriaxone in OPAT has not been strongly linked to CDI, suggesting additional patient and environmental factors may be important in mediating CDI risk.

In vitro activity of the new fluoroketolide solithromycin (CEM-101) against a large collection of clinical Neisseria gonorrhoeae isolates and international reference strains, including those with high-level antimicrobial resistance: potential treatment option for gonorrhea?

Gonorrhea may become untreatable, and new treatment options are essential. We investigated the in vitro activity of the first fluoroketolide, solithromycin. Clinical Neisseria gonorrhoeae isolates and reference strains (n = 246), including the two extensively drug-resistant strains H041 and F89 and additional isolates with clinical cephalosporin resistance and multidrug resistance, were examined. The activity of solithromycin was mainly superior to that of other antimicrobials (n = 10) currently or previously recommended for gonorrhea treatment. Solithromycin might be an effective treatment option for gonorrhea.