Dynamics of appearance and expansion of a prolyliminopeptidase- negative subtype among Neisseria gonorrhoeae isolates collected in Sydney, Australia, from 2002 to 2005

Identification of prolyliminopeptidase-negative Neisseria gonorrhoeae strains in Canada

Neisseria gonorrhoeae strains that fail to produce the enzyme prolyliminopeptidase have been identified in Canada. Commercial test panels use prolyliminopeptidase activity for identification and to avoid the misdiagnosis of gonorrhea, at least 2 distinct methods for the confirmatory identification of N. gonorrhoeae is imperative.

Prevalence, phenotypic and genetic characteristics of prolyliminopeptidase-negative Neisseria gonorrhoeae isolates in Sweden during 2000-2007

In Neisseria gonorrhoeae culture diagnostics, species confirmation is commonly performed using commercial biochemical tests relying on prolyliminopeptidase (PIP) activity. It was previously shown that one PIP-negative strain was mainly globally transmitted during 2000-2004. The aims were to investigate the prevalence and phenotypic and genetic characteristics of PIP-negative N. gonorrhoeae isolates in Sweden during 2000-2007. Gonococcal isolates (n = 1230) cultured in Sweden during 2000-2007 were characterized using PIP screening, antibiogram, serovar determination, pip and porB gene sequencing, and N. gonorrhoeae multiantigen sequence typing (NG-MAST). Fifteen (1.2%) of the isolates were PIP-negative. Of those, 13 (87%) were indistinguishable to the previously described globally transmitted strain, i.e. displayed serovar IB-4 (Bpyvut), similar antibiograms, ST210 (n = 10)/ST292 (n = 3) and contained an identical single nucleotide pip gene deletion. Wherever high reliance is placed on PIP activity for N. gonorrhoeae species confirmation, changes in the diagnostic strategies may need to be considered and/or monitoring of the PIP activity is crucial.

Characteristics and population dynamics of mosaic penA allele-containing Neisseria gonorrhoeae isolates collected in Sydney, Australia, in 2007-2008

Eighteen hundred Neisseria gonorrhoeae isolates collected in Sydney, Australia, in 2007 and 2008 were examined for mosaic penA alleles that mediated cephalosporin resistance, and the genotypes of the isolates were evaluated. In 2008, there were substantial increases in numbers (from 15 to 85) and proportions (from 1.5 to 10.3%) of mosaic-containing gonococci and major shifts in genotypic patterns, with 10 new genotypes representing 74 of the 85 mosaic-containing isolates and genotypes detected between 2001 and 2005 having disappeared. Enhanced surveillance of gonococcal resistance to cephalosporins is necessary.

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.

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

OBJECTIVES

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Using epidemiological and molecular methods to investigate an outbreak of gonorrhoea associated with heterosexual contact in Newcastle, NSW, Australia

BACKGROUND

We report a cluster of gonorrhoea among mainly heterosexual men that occurred in October 2005, which was first identified when routine weekly surveillance review procedures indicated a three-fold increase in reporting rates compared with historical data.

METHODS

Each case was followed up with the treating medical officer to review treatment regimes and risk exposures, and to carry out enhanced contact tracing. The phenotype and genotype of the outbreak gonococcal isolates and gonococci prevalent in the months preceding and following the cluster were determined. Links between cases reported from the local Sexual Health Clinic and those reported by general practitioners were established.

RESULTS

Laboratory data indicated that a particular gonococcal subtype (ST 225 and NR/Brpyst) was prevalent during the outbreak.

CONCLUSIONS

Gonorrhoea rates returned to pre-outbreak levels following a targeted health promotion intervention with no further cases of the outbreak subtype detected.

Applications of molecular testing in clinical laboratories for the diagnosis and control of gonorrhea

The potential for enhanced diagnosis and control of gonococcal infection through the application of advances in molecular medicine is now being realized. However, the introduction of diagnostic nucleic acid amplification assays (NAATs) revealed some significant limitations of these applications. Resolution of some, but not all, of these problems has led to recommendations for refined testing algorithms and a better recognition and acceptance of the limitations of NAATs. Resource restriction has limited the use of diagnostic NAATs, especially in less-developed countries where disease rates are highest. However, NAATs have also proved useful in public health approaches to gonorrhea control in all settings. Additional applications including molecular typing of gonococci to identify and interrupt gonococcal transmission chains and definition of antimicrobial resistance patterns in the gonococcus have been proposed. These approaches, especially those for antimicrobial resistance determination, have been less successful for a number of reasons, including their cost and other unresolved issues.

Diversity of penA alterations and subtypes in Neisseria gonorrhoeae strains from Sydney, Australia, that are less susceptible to ceftriaxone

Increasing numbers of Neisseria gonorrhoeae strains with decreased susceptibilities to ceftriaxone and other oral cephalosporins widely used for the treatment of gonorrhea have been isolated in Sydney, Australia, over several years. In this study, we examined the complete penicillin-binding protein 2 (PBP 2) amino acid sequences of 109 gonococci, selected on the basis of their diverse temporal and geographic origins and because they exhibited a range of ceftriaxone MICs: < OR =0.03 microg/ml (n = 59), 0.06 microg/ml (n = 43), and 0.125 microg/ml (n = 7). Auxotyping, serotyping, and genotyping by N. gonorrhoeae multiantigen sequence typing sequence-based analysis was also performed. In total, 20 different amino acid sequence patterns were identified, indicating considerable variation in the PBP 2 sequences in this study sample. Only some of the N. gonorrhoeae isolates with significantly higher ceftriaxone MICs contained a mosaic PBP 2 pattern, while more isolates exhibited a nonmosaic PBP 2 pattern containing an A501V substitution. Although particular N. gonorrhoeae genotypes in our sample were shown to be less susceptible to ceftriaxone, the reduced susceptibility to ceftriaxone was not specific to any particular genotype and was observed in a broad range of auxotypes, serotypes, and genotypes. Overall, the results of our study show that N. gonorrhoeae strains exhibiting reduced sensitivity to ceftriaxone are not of a particular subtype and that a number of different mutations in PBP 2 may contribute to this phenomenon.

Global transmission of prolyliminopeptidase-negative Neisseria gonorrhoeae strains: implications for changes in diagnostic strategies

BACKGROUND

Species confirmation of Neisseria gonorrhoeae is commonly performed with biochemical kits, rely on the activity of the enzyme prolyliminopeptidase (PIP). This enzyme has previously been considered to be almost universally present in N gonorrhoeae. However, increasing numbers of N gonorrhoeae isolates lacking PIP activity have been identified.

OBJECTIVES

To investigate the possibility of a widespread transmission of one or several N gonorrhoeae PIP-negative strains among several countries worldwide.

METHODS

PIP-negative N gonorrhoeae isolates cultured from 2001 to 2004 in Australia, New Zealand and Scotland were comprehensively characterised and compared with previous data from England and Denmark. All isolates were characterised by antibiotic susceptibility testing, serovar determination, pulsed-field gel electrophoresis (PFGE), opa-typing, sequencing of the entire porB gene and N gonorrhoeae multiantigen sequence typing (NG-MAST).

RESULTS

Most (83%) of the viable Australian isolates, and all the New Zealand and Scottish isolates were assigned serovar IB-4, with similar antibiograms, nearly identical porB1b gene sequences, identical (ST210) or highly related (ST292, ST1259) NG-MAST STs, and indistinguishable or related PFGE fingerprints as well as opa-types. The isolates showed characteristics indistinguishable or highly related to the previously described English and Danish outbreak strain.

CONCLUSIONS

A comprehensive characterisation indicates a widespread dissemination, mainly among men who have sex with men (MSM), of indistinguishable and highly related genotypes that have evolved from a single N gonorrhoeae PIP-negative serovar IB-4 strain among several countries worldwide. An increased awareness of PIP-negative N gonorrhoeae strains is crucial and changes in the diagnostic strategies may need to be considered.