Rapid expansion of Neisseria gonorrhoeae ST7827 clone in Australia, with variable ceftriaxone phenotype unexplained by genotype

BACKGROUND

Neisseria gonorrhoeae is identified as a priority pathogen due to its capacity to rapidly develop antimicrobial resistance (AMR). Following the easing of SARS-CoV-2 pandemic travel restrictions across international borders in the state of New South Wales (NSW), Australia, a surge of gonococcal isolates with raised ceftriaxone MIC values were detected.

METHODS

All N. gonorrhoeae isolates (n = 150) with increased ceftriaxone MIC values in NSW between 1 January 2021 and July 2022 from males and females from all sites were sequenced.

RESULTS

A new emergence and rapid expansion of an N. gonorrhoeae ST7827 clone was documented within NSW, Australia and provides further evidence of the ability of N. gonorrhoeae to undergo sufficient genomic changes and re-emerge as a geographically restricted subclone. Mapping AMR determinants to MIC results did not reveal any genomic pattern that correlated with MIC values.

CONCLUSIONS

The rapid dissemination and establishment of this clone at the population level is a new and concerning demonstration of the agility of this pathogen, and underscores concerns about similar incursions and establishment of MDR clones. Moreover, it is notable that in this context the AMR genotype-phenotype correlates remain unclear, which requires further investigation to enable better understanding of genomic aspects of AMR in N. gonorrhoeae.

Azithromycin-resistant Neisseria gonorrhoeae spreading amongst men who have sex with men (MSM) and heterosexuals in New South Wales, Australia, 2017

Objectives

To identify the genetic basis of resistance as well as to better understand the epidemiology of a recent surge in azithromycin-resistant Neisseria gonorrhoeae in New South Wales, Australia.

Methods

Azithromycin-resistant N. gonorrhoeae isolates (n = 118) collected from 107 males, 10 females and 1 transsexual between January and July 2017 were genotyped using a previously described iPLEX method. The results were compared with phenotypic resistance profiles and available patient data.

Results

The iPLEX results revealed 10 different N. gonorrhoeae genotypes (designated AZI-G1 to AZI-G10) of which three were responsible for the majority of infections; AZI-G10 (74.6%, 88 isolates; 87 males and 1 transsexual), AZI-G4 (11.0%, 13 isolates; 7 males and 6 females) and AZI-G7 (6.8%, 8 isolates; 7 males and 1 female). The observed resistance was attributable to one of two different azithromycin resistance mechanisms; the 23S rRNA C2611T mutation was identified in 24% of isolates, whereas the majority of resistance (76%) was associated with a meningococcal-type mtrR variant. Additionally, one isolate was found to harbour both the 23S rRNA C2611T mutation and a type XXXIV mosaic penA sequence associated with cephalosporin resistance.

Conclusions

These data indicate outbreaks of azithromycin-resistant gonococci amongst networks of MSM and heterosexuals in New South Wales. The results also provide further evidence that azithromycin may soon be an ineffective treatment option for gonococcal infection and highlight the urgent need to explore alternative therapies.

Molecular Antimicrobial Resistance Surveillance for Neisseria gonorrhoeae, Northern Territory, Australia

Neisseria gonorrhoeae antimicrobial resistance (AMR) is a globally recognized health threat; new strategies are needed to enhance AMR surveillance. The Northern Territory of Australia is unique in that 2 different first-line therapies, based primarily on geographic location, are used for gonorrhea treatment. We tested 1,629 N. gonorrhoeae nucleic acid amplification test–positive clinical samples, collected from regions where ceftriaxone plus azithromycin or amoxicillin plus azithromycin are recommended first-line treatments, by using 8 N. gonorrhoeae AMR PCR assays. We compared results with those from routine culture-based surveillance data. PCR data confirmed an absence of ceftriaxone resistance and a low level of azithromycin resistance (0.2%), and that penicillin resistance was <5% in amoxicillin plus azithromycin regions. Rates of ciprofloxacin resistance and penicillinase-producing N. gonorrhoeae were lower when molecular methods were used. Molecular methods to detect N. gonorrhoeae AMR can increase the evidence base for treatment guidelines, particularly in settings where culture-based surveillance is limited.

Changes in the rates of Neisseria gonorrhoeae antimicrobial resistance are primarily driven by dynamic fluctuations in common gonococcal genotypes

Objectives

To examine how gonococcal genotypes and associated changes over time influence rates of Neisseria gonorrhoeae antimicrobial resistance.

Methods

All available N. gonorrhoeae isolates collected in New South Wales, Australia in the first half of both 2012 and 2014 were genotyped using the Agena MassARRAY iPLEX platform. Genotypic data were compared with phenotypic antimicrobial resistance profiles over time. We focused on penicillin and ciprofloxacin as significant increases in resistance to both antibiotics were observed over this time period.

Results

Genotyping data were obtained for 760 and 782 isolates in 2012 and 2014, respectively. A total of 162 distinct genotypes were identified in the study, including 36 (22.2%) genotypes present in both years ( persisting genotypes), 54 (33.3%) observed in 2012 only and 72 (44.4%) observed in 2014 only (s ingle-year genotypes). Overall, persisting genotypes comprised 15 of the 20 most common genotypes, 8 of which showed a significant change in proportion from 2012 to 2014. Persisting genotypes also comprised the majority (>70%) of ciprofloxacin- and penicillin-resistant isolates in both years. Significant fluctuations in the most common persisting genotypes accounted for the majority of observed increases in both ciprofloxacin and penicillin resistance. Single-year genotypes contributed to ∼20% of ciprofloxacin and penicillin resistance in each year.

Conclusions

The results show that the gonococcal genotypes persisting in the study population fluctuated significantly within a 3 year period, with numerous other genotypes appearing or disappearing. It is the net effect of these changes that determines N. gonorrhoeae antimicrobial resistance levels within the population.

Real-time PCR detection of Neisseria gonorrhoeae susceptibility to penicillin

OBJECTIVES

The objective of this study was to develop a real-time PCR assay targeting the gonococcal porB gene (PorB-PCR) for predicting susceptibility of Neisseria gonorrhoeae to penicillin. This complements a previously described PCR assay for detecting penicillinase-producing N. gonorrhoeae (PPNG) developed by our laboratory (PPNG-PCR).

METHODS

The PorB-PCR assay was designed using six probes to characterize various combinations of amino acids at positions 101 and 102 of the PorB1b class protein, including the WT G101/A102 and mutant G101K/A102D, G101K/A102N and G101K/A102G sequences, as well as the PorB1a sequence. The ability of these sequences to predict penicillin susceptibility was initially assessed using 2307 N. gonorrhoeae isolates from throughout Australia for which phenotypic susceptibility data were available. The assay was then applied to N. gonorrhoeae-positive clinical specimens (n = 70). Specificity was assessed by testing commensal Neisseria strains (n = 75) and N. gonorrhoeae-negative clinical specimens (n = 171).

RESULTS

Testing of the 2307 N. gonorrhoeae isolates using PorB-PCR to detect G101/A102 and PorB1a sequences identified a total of 78.4% (61.2% and 17.2%, respectively) of penicillin-susceptible isolates with specificities of 97.4% and 99.3% and positive predictive values of 98.8% and 98.9%, where PPNG strains were simultaneously identified and excluded. Similar performance data were obtained when the PorB-PCR assay was applied to the N. gonorrhoeae-positive clinical specimens. No false-positive results were observed for the N. gonorrhoeae-negative samples and no cross-reactions were observed with the non-gonococcal species.

CONCLUSIONS

When used in parallel with the previously described PPNG-PCR, the PorB-PCR approach has the potential to facilitate individualized treatment of gonorrhoea using penicillin.

Pharyngeal Gonorrhoea in Women: An Important Reservoir for Increasing Neisseria gonorrhoea Prevalence in Urban Australian Heterosexuals?

We aim to characterize sexual behavioral aspects of heterosexual Neisseria gonorrhoea (NG) acquisition in two Sexually Transmitted Diseases clinics in Sydney, Australia, in 2008-2012. Of 167 NG cases, 102 were heterosexually acquired with a trend of increasing NG prevalence in heterosexuals from 1.1% (95% CI 0.6-2.1) in 2008 to 3.0% (95% CI 2.0-4.0) in 2012 (P = 0.027). Of heterosexual male cases, unprotected fellatio was the likely sexual activity for NG acquisition in 21/69 (30.4%) and commercial sex work (CSW) contact the likely source in 28/69 (40.6%). NG prevalence overall in CSW (2.2%) was not significantly higher than in non-CSW (1.2%) (P = 0.15), but in 2012 there was a significant increase in NG prevalence in CSW (8.6%) compared to non-CSW (1.6%) (P < 0.001). Pharyngeal NG was found in 9/33 (27.3%) female cases. Decreased susceptibility to ceftriaxone (MIC ≥ 0.03 mg/L) occurred in 2.5% NG isolates, none heterosexually acquired. All were azithromycin susceptible. A significant trend of increasing prevalence of heterosexual gonorrhoea in an urban Australian STD clinic setting is reported. We advocate maintenance of NG screening in women, including pharyngeal screening in all women with partner change who report fellatio, as pharyngeal NG may be an important reservoir for heterosexual transmission. Outreach to CSW should be enhanced.

Effect of climate on the seasonal endocrine profile of native and crossbred sheep under semi-arid conditions

Thirty-four 2-year-old ewes, of which 17 were native (Chokla) and 17 were Avivastra (Chokla 67.5% x 32.5% Rambouillet) breeds of similar body weights, were selected. Both groups were maintained under the same management conditions with 8 hours daily grazing. In addition to grazing, each ewe received 300 g/day of a concentrate mixture comprising crude protein 20% and 70% total digestible nutrients. The ewes of both breeds were not mated during the study. The daily environmental parameters were recorded throughout the year, consisting of four main seasons, namely rainy, winter, spring and summer. Blood samples were collected into heparinized tubes during the morning hours for seasonal studies via indwelling jugular vein catheters to avoid stress to the animals, but for the diurnal studies the sampling was done twice daily at 07:00 and 17:00 continuously for three days in each season. Cortisol, thyroxine (T4) and triiodothyronine (T3) were estimated in the samples. The T4 and T3 profiles were maximal in the summer, followed by the rainy season in both groups, with no significant differences. However, the cortisol in both the groups was maximal during the spring rather than the summer. No significant differences were found in T3 concentration between morning and afternoon in any season in the native ewes but these animals showed significantly higher levels of T4 in the morning. The opposite was true for the crossbred animals with regard to both the T3 and T4 profiles. Significantly more cortisol was found in the evening than in the morning in both genetic groups in all seasons.