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

Whole genome analysis and antimicrobial resistance of Neisseria gonorrhoeae isolates from Ghana

Introduction

Gonorrhoea is a major public health concern. With the global emergence and spread of resistance to last-line antibiotic treatment options, gonorrhoea threatens to be untreatable in the future. Therefore, this study performed whole genome characterization of Neisseria gonorrhoeae collected in Ghana to identify lineages of circulating strains as well as their phenotypic and genotypic antimicrobial resistance (AMR) profiles.

Methods

Whole genome sequencing (WGS) was performed on 56 isolates using both the Oxford Nanopore MinION and Illumina MiSeq sequencing platforms. The Comprehensive Antimicrobial Resistance Database (CARD) and PUBMLST.org/neisseria databases were used to catalogue chromosomal and plasmid genes implicated in AMR. The core genome multi-locus sequence typing (cgMLST) approach was used for comparative genomics analysis.

Results and Discussion

In vitro resistance measured by the E-test method revealed 100%, 91.0% and 85.7% resistance to tetracycline, penicillin and ciprofloxacin, respectively. A total of 22 sequence types (STs) were identified by multilocus sequence typing (MLST), with ST-14422 (n = 10), ST-1927 (n = 8) and ST-11210 (n = 7) being the most prevalent. Six novel STs were also identified (ST-15634, 15636-15639 and 15641). All isolates harboured chromosomal AMR determinants that confer resistance to beta-lactam antimicrobials and tetracycline. A single cefixime-resistant strain, that belongs to N. gonorrhoeae multiantigen sequence type (NG-MAST) ST1407, a type associated with widespread cephalosporin resistance was identified. Neisseria gonorrhoeae Sequence Typing for Antimicrobial Resistance (NG-STAR), identified 29 unique sequence types, with ST-464 (n = 8) and the novel ST-3366 (n = 8) being the most prevalent. Notably, 20 of the 29 STs were novel, indicative of the unique nature of molecular AMR determinants in the Ghanaian strains. Plasmids were highly prevalent: pTetM and pblaTEM were found in 96% and 92% of isolates, respectively. The TEM-135 allele, which is an amino acid change away from producing a stable extended-spectrum β-lactamase that could result in complete cephalosporin resistance, was identified in 28.5% of the isolates. Using WGS, we characterized N. gonorrhoeae strains from Ghana, giving a snapshot of the current state of gonococcal AMR in the country and highlighting the need for constant genomic surveillance.

Phylogenomic analysis reveals persistence of gonococcal strains with reduced-susceptibility to extended-spectrum cephalosporins and mosaic penA-34

The recent emergence of strains of Neisseria gonorrhoeae associated with treatment failures to ceftriaxone, the foundation of current treatment options, has raised concerns over a future of untreatable gonorrhea. Current global data on gonococcal strains suggest that several lineages, predominately characterized by mosaic penA alleles, are associated with elevated minimum inhibitory concentrations (MICs) to extended spectrum cephalosporins (ESCs). Here we report on whole genome sequences of 813 N. gonorrhoeae isolates collected through the Gonococcal Isolate Surveillance Project in the United States. Phylogenomic analysis revealed that one persisting lineage (Clade A, multi-locus sequence type [MLST] ST1901) with mosaic penA-34 alleles, contained the majority of isolates with elevated MICs to ESCs. We provide evidence that an ancestor to the globally circulating MLST ST1901 clones potentially emerged around the early to mid-20th century (1944, credibility intervals [CI]: 1935-1953), predating the introduction of cephalosporins, but coinciding with the use of penicillin. Such results indicate that drugs with novel mechanisms of action are needed as these strains continue to persist and disseminate globally.

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.

Molecular Typing of Neisseria gonorrhoeae Clinical Isolates in Russia, 2018-2019: A Link Between penA Alleles and NG-MAST Types

This work aimed to study penA gene polymorphisms in clinical isolates of Neisseria gonorrhoeae collected in Russia in 2018-2019 and the contribution of the penA allele type to susceptibility to β-lactam antibiotics. A total of 182 isolates were analyzed. penA allele types were determined by sequencing, and the minimum inhibitory concentrations (MICs) of benzylpenicillin and ceftriaxone were measured. The influence of genetic factors on MICs was evaluated by regression analysis. All isolates were susceptible to ceftriaxone, and 40.1% of isolates were susceptible to penicillin. Eleven penA allele types were identified. The mosaic type XXXIV penA allele and the Gly120Lys substitution in PorB made the greatest contributions to increasing the ceftriaxone MIC; the presence of the bla_TEM plasmid, Gly120Asp, Ala121Gly/Asn substitutions in PorB, and the adenine deletion in the promoter region of the mtrR gene caused an increase in the penicillin MIC. Among 61 NG-MAST types identified, the most frequent were types 228, 807, 9486, 1993, and 6226. A link between penA alleles and Neisseria gonorrhoeae multi-antigen sequence typing (NG-MAST) types was established. Resistance to two groups of β-lactam antibiotics was associated with non-identical changes in penA alleles. To prevent the emergence of ceftriaxone resistance in Russia, NG-MAST genotyping must be supplemented with penA allele analysis.

Evidence of Recent Genomic Evolution in Gonococcal Strains With Decreased Susceptibility to Cephalosporins or Azithromycin in the United States, 2014-2016

BACKGROUND

Given the lack of new antimicrobials or a vaccine, understanding the evolutionary dynamics of Neisseria gonorrhoeae is a significant public and global health priority. We investigated the emergence and spread of gonococcal strains with decreased susceptibility to cephalosporins and azithromycin using detailed genomic analyses of gonococcal isolates collected in the United States, 2014-2016.

METHODS

We sequenced genomes of 649 isolates collected through the Gonococcal Isolate Surveillance Project. We examined the genetic relatedness of isolates and assessed associations between clades and various genotypic and phenotypic combinations.

RESULTS

We identified a large and clonal lineage of strains (MLST ST9363) associated with elevated azithromycin minimum inhibitory concentration (AZIem), characterized by a mosaic mtr locus (C substitution in the mtrR promoter, mosaic mtrR and mtrD). Mutations in 23S rRNA were sporadically distributed among AZIem strains. Another clonal group (MLST ST1901) possessed 7 unique PBP2 patterns, and it shared common mutations in other genes associated with cephalosporin resistance.

CONCLUSIONS

Whole-genome sequencing methods can enhance monitoring of antimicrobial resistant gonococcal strains by identifying gonococcal populations containing mutations of concern. These methods could inform the development of point-of-care diagnostic tests designed to determine the specific antibiotic susceptibility profile of a gonococcal infection in a patient.

Characterization of antimicrobial resistance genes from Neisseria gonorrhoeae positive remnant Aptima urine specimens

Aim: To ascertain the antimicrobial resistance and strain types (STs) of Neisseria gonorrhoeae from 50 remnant Aptima urine specimens using molecular methods. Methods: Mutations predictive of resistance to six antibiotics were identified in eight genes. STs were determined using NG-MAST and NG-STAR. Results: All eight antimicrobial resistance genes could be characterized in 36 specimens. A total of 17 specimens were predicted to be susceptible to all antibiotics, including ceftriaxone. Decreased susceptibility to cefixime and ciprofloxacin resistance was predicted in 11 specimens (PBP2 type 34.001). Overall, 38/50 specimens were predicted to be ciprofloxacin susceptible; three were azithromycin resistant. Nineteen NG-MAST and 21 NG-STAR STs were noted. Conclusion: Molecular analysis of remnant Aptima specimens enabled the prediction of emerging gonococcal cefixime and azithromycin resistance which would otherwise have been undetected.

Multiresistant Neisseria gonorrhoeae: a new threat in second decade of the XXI century

Neisseria gonorrhoeae is an etiologic agent of gonorrhoea, one of the most common sexually transmitted diseases caused by bacteria. For many years, infections caused by N. gonorrhoeae were considered to be relatively easy to treat; however, resistance has emerged successively to all therapeutic agents used in treatment of the disease, e.g., penicillin, ciprofloxacin or azithromycin. Currently, the global problem is the emergence and a threat of spread of N. gonorrhoeae strains resistant to extended-spectrum cephalosporins (ESC), such as injectable ceftriaxone and oral-used cefixime. Especially, dangerous are multi-resistant strains resistant simultaneously to ESC and azithromycin. Three strains with high-level resistance to azithromycin and resistant to ESC were first time isolated in 2018. Moreover, in 2018, the first ESBL was described in N. gonorrhoeae and that makes the threat of appearing the ESBL mechanism of resistance in N. gonorrhoeae more real, even though the strain was sensitive to ceftriaxone. Molecular typing revealed that variants resistant to ESC occurred also among strains belonging to epidemic clonal complex CC1 (genogroup G1407) distinguished in NG-MAST typing system. The G1407 genogroup, in particular the ST1407 sequence type, is currently dominant in most European countries. The presence of different mechanisms of drug resistance significantly affects clinical practice and force changes in treatment regimens and introduction of new drugs.

Association of Neisseria gonorrhoeae genogroups and specific PBP2/MtrR/PorB mutation patterns with susceptibility to penicillin in a susceptible gonococcal population

Objectives

To ascertain whether the antimicrobial susceptibility of Neisseria gonorrhoeae isolates with differing susceptibilities to penicillin is associated with genogroups (GGs) and combined mutation patterns in PBP2 (penA), the multiple transfer resistance repressor (MtrR; mtrR) and porin B (PorB; porB).

Methods

The susceptibility of 146 clinical N. gonorrhoeae isolates to penicillin was determined using the agar dilution method and the interpretation criteria of CLSI. The DNA sequences of penA, mtrR and porB in isolates were compared with WT sequences and mutation patterns were determined. Isolates were typed by N. gonorrhoeae multi-antigen sequence typing (NG-MAST) and STs were grouped into specific GGs.

Results

The isolates tested carried 9 mutation patterns in PBP2 and 12 mutation patterns in each of MtrR and PorB. Of the 146 isolates, 121 (82.9%) were grouped into 13 different GGs. Isolates with penicillin MICs of 0.03-0.06 mg/L were significantly associated with GG25 (P < 0.05) and PBP2/MtrR/PorB mutation pattern I/WT/WT (P < 0.01). Isolates with a penicillin MIC of 1.0 mg/L were associated (P < 0.05) with: (i) GG3655 and mutation pattern XXII/A-;G45D/G120K;A121N; (ii) GG921 and mutation pattern IX/G45D/G120D;A121N; and (iii) GG1109 and mutation pattern IX/G45D/WT. Sixty percent (9/15) of penicillin-resistant isolates (MIC ≥2 mg/L) were GG3654 (P < 0.0001) and carried mutation pattern IX/G45D/G120K;A121D or IX/G45D/G120D;A121D (P < 0.05).

Conclusions

Specific mutation patterns in PBP2/MtrR/PorB were associated with specific GGs and penicillin susceptibility. This approach of typing strains and resistance patterns is ideal for predicting antimicrobial resistance and should be used in instances in which gonococcal culture is not available but DNA can be obtained from clinical specimens.

The first year of the global Enhanced Gonococcal Antimicrobial Surveillance Programme (EGASP) in Bangkok, Thailand, 2015-2016

Antimicrobial-resistant Neisseria gonorrhoeae (NG) infection is a global public health threat, and there is a critical need to monitor patterns of resistance and risk factors. In collaboration with the World Health Organization (WHO), the U.S. Centers for Disease Control and Prevention (CDC), and the Thailand Department of Disease Control (DDC), Ministry of Public Health (MoPH) implemented the first Enhanced Gonococcal Antimicrobial Surveillance Programme (EGASP) in November 2015. Men presenting with urethritis at two clinical settings in Bangkok, Thailand (Bangrak Hospital [BH] and Silom Community Clinic @TropMed [SCC @TropMed]) provided demographic and behavioral information and had a urethral swab for Gram's stain and NG culture collected. The NG isolates were evaluated for antimicrobial susceptibility by the Epsilometer test (Etest) to determine minimum inhibitory concentrations (MICs) for cefixime (CFM), ceftriaxone (CRO), azithromycin (AZI), gentamicin (GEN), and ciprofloxacin (CIP). From November 2015 -October 2016, 1,102 specimens were collected from 1,026 symptomatic men; 861 (78.1%) specimens were from BH and 241 (21.9%) specimens were from SCC @TropMed. Among the 1,102 specimens, 582 (52.8%) had intracellular Gram-negative diplococci and 591 (53.6%) had NG growth (i.e., NG infection); antimicrobial susceptibility testing (AST) was performed on 590 (99.8%) NG isolates. Among all symptomatic men, 293 (28.6%) had sex with men only, 430 (41.9%) were ages 18-29 years, 349 (34.0%) had antibiotic use in the last 2 weeks, and 564 (55.0%) had NG infection. Among 23 men with repeat NG infection during this first year of surveillance, 20 (87.0%) were infected twice, 2 (8.7%) were infected three times, and 1 (4.3%) was infected more than four times. All NG isolates were susceptible to CFM and CRO, and had MICs below 2 μg/mL for AZI and below 16 μg/mL for GEN. Overall, 545 (92.4%) isolates were resistant to CIP. This surveillance activity assessed individual patients, and included demographic and behavioral data linked to laboratory data. The inclusion of both individual and laboratory information in EGASP could help identify possible persistent infection and NG treatment failures. Expansion of EGASP to additional global settings is critical to assess trends and risk factors for NG, and to monitor for the emergence of resistance.

Genomic epidemiology and population structure of Neisseria gonorrhoeae from remote highly endemic Western Australian populations

BACKGROUND

Neisseria gonorrhoeae causes gonorrhoea, the second most commonly notified sexually transmitted infection in Australia. One of the highest notification rates of gonorrhoea is found in the remote regions of Western Australia (WA). Unlike isolates from the major Australian population centres, the remote community isolates have low rates of antimicrobial resistance (AMR). Population structure and whole-genome comparison of 59 isolates from the Western Australian N. gonorrhoeae collection were used to investigate relatedness of isolates cultured in the metropolitan and remote areas. Core genome phylogeny, multilocus sequencing typing (MLST), N. gonorrhoeae multi-antigen sequence typing (NG-MAST) and N. gonorrhoeae sequence typing for antimicrobial resistance (NG-STAR) in addition to hierarchical clustering of sequences were used to characterize the isolates.

RESULTS

Population structure analysis of the 59 isolates together with 72 isolates from an international collection, revealed six population groups suggesting that N. gonorrhoeae is a weakly clonal species. Two distinct population groups, Aus1 and Aus2, represented 63% of WA isolates and were mostly composed of the remote community isolates that carried no chromosomal AMR genotypes. In contrast, the Western Australian metropolitan isolates were frequently multi-drug resistant and belonged to population groups found in the international database, suggesting international transmission of the isolates.

CONCLUSIONS

Our study suggests that the population structure of N. gonorrhoeae is distinct between the communities in remote and metropolitan WA. Given the high rate of AMR in metropolitan regions, ongoing surveillance is essential to ensure the enduring efficacy of the empiric gonorrhoea treatment in remote WA.

Ceftriaxone susceptibility and molecular characteristics of Neisseria gonorrhoeae isolates in Changsha, China

A total of 128 Neisseria gonorrhoeae isolates were consecutively obtained in Changsha, China, between April 2015 and June 2016. The minimum inhibitory concentrations (MICs) of ceftriaxone were measured by agar dilution method for each isolate. Ceftriaxone resistance determinants involving penA, mtrR, porB and ponA were amplified by PCR, and the PCR products were sequenced. N. gonorrhoeae multi-antigen sequence typing (NG-MAST) was conducted for genotyping. The results exhibited 11% (14/128) of isolates were reduced susceptibility or resistant to ceftriaxone. One isolate with a susceptibility MIC of 0.03 mg/L harbored a penA mosaic allele. PBP2 A501V/T or P551S and the PorB1b G120K/A121D mutations were predominant in the 14 decreased susceptible or resistant isolates. Among the 128 isolates, 31 sequence types (STs) were identified, and the most prevalent STs were STnew1 (n = 40), ST5061 (n = 25) and ST9176 (n = 18). The 14 decreased susceptible or resistant isolates were resolved into 9 STs, displaying considerable diversity. The results of ceftriaxone susceptibility testing indicated that ceftriaxone can continue to be recommended as the first-line drug for gonorrhea treatment in Changsha; however, it is important to maintain promptly surveillance for antimicrobial resistance (AMR). Non-mosaic penA alleles with A501V/T, P551S, and porB1b mutations may contribute to ceftriaxone resistance or decreased susceptibility among N. gonorrhoeae in this area, and heterogenous STs in these isolates excluded the clonal expansion for a particular subtype.

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.

Plasmid-mediated resistance to tetracyclines among Neisseria gonorrhoeae strains isolated in Poland between 2012 and 2013

Introduction

One of two main mechanisms of resistance in tetracycline-resistant Neisseria gonorrhoeae (TRNG) is associated with the presence of TetM protein responsible for actively blocking of the tetracycline target site in the 30S ribosomal subunit. This mechanism is encoded by conjugative plasmids. The second mechanism is chromosomal in nature and due to mutations in specific genes.

Aim

To determine the incidence and type of tetM determinants in TRNG strains isolated from patients presenting with gonorrhea infection to the Dermatology and Venereology Clinic in Warsaw in 2012–2013.

Material and methods

Tetracycline and doxycycline susceptibility was determined by E-Tests. The presence and type of the tetM gene were determined by polymerase chain reaction.

Results

Tetracycline resistance was detected in 50.8% of the evaluated strains. The TRNG strains containing the tetM plasmid constituted 13.8% of all the evaluated strains. Dutch type tetM constituted 12.3% and American type tetM 1.5% of all the evaluated strains. In the remaining TRNG strains, resistance to tetracyclines was presumably chromosome-encoded. The minimal inhibitory concentration (MIC) of tetracycline ranged from 0.25 to 32.0 mg/l, MIC₅₀ = 2.0 mg/l, MIC₉₀ = 32.0 mg/l. The MIC of doxycycline ranged from 0.25 to 32.0 mg/l, MIC₅₀ = 4.0 mg/l, MIC₉₀ = 16.0 mg/l.

Conclusions

Unlike most of European countries, in 2012–2013 in Poland, the Dutch type tetM was found to be much more common than the American type. Minimal inhibitory concentration values of tetracycline and doxycycline were similar, with doxycycline exhibiting a somewhat lower effectiveness in vitro than tetracycline towards chromosome-mediated tetracycline resistant strains of N. gonorrhoeae.

Genetic Resistance Determinants for Cefixime and Molecular Analysis of Gonococci Isolated in Italy

A strictly defined subset of gonococci (n = 65) isolated in Italy from 2011 to 2014 was characterized by antimicrobial susceptibility for cefixime (CFM) and ceftriaxone (CRO) and by sequencing of resistance determinant genes (penA, mtrR, porB1b, ponA) for extended-spectrum cephalosporins and Neisseria gonorrhoeae multiantigen sequence typing (NG-MAST). The penA mosaic alleles XXXIV and XXXV were found in all resistant (R) and decreased susceptibility (DS) gonococci to CFM, except for one. They were associated with an adenine deletion in the mtrR promoter plus amino acid substitutions, H105Y or G45D, in the coding region and ponA L421P. The penA mosaic allele XXXIV, and one variant, was found exclusively among genogroup (G) 1407 and its closely related sequence types (STs), as in CFM-DS as well as in CFM-R isolates. Single or combined mutation patterns in penA, mtrR, porB1b, and ponA genes were associated with different CFM susceptibility patterns and NG-MAST STs. Genotyping and antimicrobial resistance (AMR) determinant analyses can be valuable to enhance the gonococcal AMR surveillance.

Neisseria gonorrhoeae antimicrobial susceptibility in Barcelona: penA, ponA, mtrR, and porB mutations and NG-MAST sequence types associated with decreased susceptibility to cephalosporins

The aims of this study were to determine the antimicrobial susceptibility of Neisseria gonorrhoeae (NG) in our area, to analyze the molecular mechanisms involved in cephalosporins resistance, and to undertake molecular typing of our NG strains. Antimicrobial susceptibility was determined using the Etest. The genes penA, mtrR, penB, and ponA were studied. Molecular typing was performed by N. gonorrhoeae multiantigen sequence typing. Of 329 strains analyzed in 2013, none showed high-level cephalosporin resistance, but 8.2 % had resistance to cefixime [minimum inhibitory concentration (MIC) > 0.125 μg/mL] and 0.6 % to ceftriaxone (MIC > 0.125 μg/mL). Azithromycin resistance was documented in 4.3 % and ciprofloxacin resistance in 49.2 %. Among 48 strains with an MIC ≥ 0.125 μg/mL to cefixime, 58.3 % showed the penA mosaic pattern XXXIV, 98 % a Leu → Pro substitution at position 421 of the ponA gene, 100 % amino acid changes at positions 101 and 102 of the PorB1b porin, and 87.5 % of strains an adenine deletion in the promoter region of the MtrC-D-E efflux pump. A significant difference between strains with and without decreased cephalosporin susceptibility (MIC ≥ 0.125 μg/mL) was observed for these four genes. Of the 48 strains with an MIC ≥ 0.125 μg/mL to cefixime, 43.8 % belonged to the genogroup G1407 and 27.1 % belonged to the genogroup G2400. A significant association of G1407 with decreased susceptibility (MIC ≥ 0.125 μg/mL) and G2992 with susceptibility was found, and also between G1407 and mosaic pattern XXXIV and between G2400 and A501T substitution in penA. The NG resistance rate in our area is higher than the median of Europe. We have detected the emergence of G2400, which may be a source of antimicrobial resistance.

Drug Resistance Mechanisms in Bacteria Causing Sexually Transmitted Diseases and Associated with Vaginosis

Here, we review sexually transmitted diseases (STDs) caused by pathogenic bacteria and vaginal infections which result from an overgrowth of opportunistic bacterial microflora. First, we describe the STDs, the corresponding pathogens and the antimicrobials used for their treatment. In addition to the well-known diseases caused by single pathogens (i.e., syphilis, gonococcal infections, and chlamydiosis), we consider polymicrobial reproductive tract infections (especially those that are difficult to effectively clinically manage). Then, we summarize the biochemical mechanisms that lead to antimicrobial resistance and the most recent data on the emergence of drug resistance in STD pathogens and bacteria associated with vaginosis. A large amount of research performed in the last 10-15 years has shed light on the enormous diversity of mechanisms of resistance developed by bacteria. A detailed understanding of the mechanisms of antimicrobials action and the emergence of resistance is necessary to modify existing drugs and to develop new ones directed against new targets.

Novel Genes Related to Ceftriaxone Resistance Found among Ceftriaxone-Resistant Neisseria gonorrhoeae Strains Selected In Vitro

The emergence of ceftriaxone-resistantNeisseria gonorrhoeaeis currently a global public health concern. However, the mechanism of ceftriaxone resistance is not yet fully understood. To investigate the potential genes related to ceftriaxone resistance inNeisseria gonorrhoeae, we subcultured six gonococcal strains with increasing concentrations of ceftriaxone and isolated the strains that became resistant. After analyzing several frequently reported genes involved in ceftriaxone resistance, we found only a single mutation inpenA(A501V). However, differential analysis of the genomes and transcriptomes between pre- and postselection strains revealed many other mutated genes as well as up- and downregulated genes. Transformation of the mutatedpenAgene into nonresistant strains increased the MIC between 2.0- and 5.3-fold, and transformation of mutatedftsXincreased the MIC between 3.3- and 13.3-fold. Genes encoding the ABC transporters FarB, Tfq, Hfq, and ExbB were overexpressed, whilepilM,pilN, andpilQwere downregulated. Furthermore, the resistant strain developed cross-resistance to penicillin and cefuroxime, had an increased biochemical metabolic rate, and presented fitness defects such as prolonged growth time and downregulated PilMNQ. In conclusion, antimicrobial pressure could result in the emergence of ceftriaxone resistance, and the evolution of resistance ofNeisseria gonorrhoeaeto ceftriaxone is a complicated process at both the pretranscriptional and posttranscriptional levels, involving several resistance mechanisms of increased efflux and decreased entry.

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.

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.

Behavioral and socioeconomic risk factors associated with probable resistance to ceftriaxone and resistance to penicillin and tetracycline in Neisseria gonorrhoeae in Shanghai

Globally, incidence of Neisseria gonorrhoeae infection is once again the highest of the bacterial sexually transmitted infections. The bacterium can produce serious complications in those infected, and emerging resistance to third generation cephalosporins could usher in an era of potentially untreatable gonorrhea. This research aimed to identify risk factors for antibiotic resistant gonorrhea infection among clients at a Shanghai sexually transmitted infection clinic over two time periods, 2004-2005 and 2008-2011. Demographic and risk factor behavior data, and biological samples for antimicrobial resistance analysis, were collected. Statistical models were built to identify risk factors associated with probable resistance to ceftriaxone and resistance to penicillin and tetracycline. High levels of ciprofloxacin resistance (98%) in our sample precluded examining its risk factors; all isolates were susceptible to spectinomycin. Overall (P<0.001), chromosomal (P<0.001), and plasmid-mediated (P = 0.01) penicillin resistance decreased from the first to second period of the study. For tetracycline, chromosomal resistance decreased (P = 0.01) and plasmid-mediated resistance increased (P<0.001) between the first and second periods of study. In multi-level multivariable regression models, male gender (P = 0.03) and older age (P = 0.01) were associated with increased minimum inhibitory concentrations to ceftriaxone. Male gender (P = 0.03) and alcohol use (P = 0.02) were associated with increased odds of overall tetracycline resistance. Male gender was associated with increased odds of chromosomally-mediated tetracycline resistance (P = 0.04), and alcohol use was associated with increased odds of plasmid-mediated tetracycline resistance (P = 0.02). Additionally, individuals in middle-salary categories were found to have lower odds of plasmid-mediated resistance to tetracycline compared with those in the lowest salary category (P≤0.02). This study is one of the first to use multilevel analysis to consider the association between risk factors for gonorrhea infections and mechanisms of resistance to individual antibiotics. Such information is urgently needed to combat the growing threat of untreatable gonorrhea.