Antimicrobial resistance among Shigella in New Zealand.

AIM: We undertook a national survey to provide current information on antimicrobial resistance among Shigella isolated in New Zealand. METHODS: Diagnostic laboratories are requested to refer all Shigella isolates to the Institute of Environmental Science and Research (ESR) for epidemiological typing as part of the national surveillance of shigellosis. The antimicrobial susceptibility of 263 non-duplicate Shigella isolates referred to ESR in 2015 and 2016 was tested. RESULTS: The 263 Shigella comprised 141 (53.6%) S. sonnei, 113 (43.0%) S. flexneri, 7 (2.7%) S. boydii and 2 (0.8%) S. dysenteriae. Among the 141 S. sonnei, the majority were either biotype g (90) or biotype a (50). Rates of resistance to the two currently recommended first-line antibiotics, co-trimoxazole and fluoroquinolones, were relatively high at 56.7% and 22.8%, respectively. Azithromycin is considered a second-line treatment option, but 11.0% of Shigella were categorised as having a non-wildtype (NWT) azithromycin phenotype (ie, having some mechanism of azithromycin resistance although not necessarily clinically resistant). There were several significant differences in resistance between the two most prevalent S. sonnei biotypes, with resistance being significantly more prevalent among biotype g isolates. Shigella from patients who had not travelled overseas were significantly more likely to be azithromycin NWT than isolates from patients who had recently travelled (20.7 vs 5.6%). Azithromycin NWT was more prevalent among Shigella from males than females (13.9 vs 7.7%). CONCLUSIONS: These results suggest there is an immediate need to revise the currently recommended first-line treatment for shigellosis, especially when treatment is given on an empirical basis. Equally concerning is the fact that resistance to the second-line antibiotic for shigellosis, azithromycin, appears to be emerging in New Zealand. As diagnostic laboratories increase their use of culture-independent testing, it is recommended that they should continue to culture specimens from all shigellosis cases so that isolates are available for susceptibility testing and epidemiological typing.

Genomic epidemiology and antimicrobial resistance of Neisseria gonorrhoeae in New Zealand.

Background: Antimicrobial-resistant Neisseria gonorrhoeae is a major threat to public health. No studies to date have examined the genomic epidemiology of gonorrhoea in the Western Pacific Region, where the incidence of gonorrhoea is particularly high. Methods: A population-level study of N. gonorrhoeae in New Zealand (October 2014 to May 2015). Comprehensive susceptibility testing and WGS data were obtained for 398 isolates. Relatedness was inferred using phylogenetic trees, and pairwise core SNPs. Mutations and genes known to be associated with resistance were identified, and correlated with phenotype. Results: Eleven clusters were identified. In six of these clusters, >25% of isolates were from females, while in eight of them, >15% of isolates were from females. Drug resistance was common; 98%, 32% and 68% of isolates were non-susceptible to penicillin, ciprofloxacin and tetracycline, respectively. Elevated MICs to extended-spectrum cephalosporins (ESCs) were observed in 3.5% of isolates (cefixime MICs ≥ 0.12 mg/L, ceftriaxone MICs ≥ 0.06 mg/L). Only nine isolates had penA XXXIV genotypes, three of which had decreased susceptibility to ESCs (MIC = 0.12 mg/L). Azithromycin non-susceptibility was identified in 43 isolates (10.8%); two of these isolates had 23S mutations (C2611T, 4/4 alleles), while all had mutations in mtrR or its promoter. Conclusions: The high proportion of females in clusters suggests transmission is not exclusively among MSM in New Zealand; re-assessment of risk factors for transmission may be warranted in this context. As elevated MICs of ESCs and/or azithromycin were found in closely related strains, targeted public health interventions to halt transmission are urgently needed.

Identification and molecular characterisation of New Delhi metallo-ß-lactamase-1 (NDM-1)- and NDM-6-producing Enterobacteriaceae from New Zealand hospitals.

The global spread of New Delhi metallo-ß-lactamase (NDM) is of significant public health concern. This study sought to determine whether bla(NDM) was present in Enterobacteriaceae isolates displaying resistance to carbapenems that were submitted to the National Antibiotic Reference Laboratory, Institute of Environmental Science and Research (Porirua, New Zealand) during 2009 and 2010. Isolates were tested for the presence of ß-lactamase genes and 16S rRNA methylase genes by polymerase chain reaction (PCR) and sequencing. Plasmid transfer studies were undertaken on isolates found to be harbouring bla(NDM). Molecular typing was performed by multilocus sequence typing (MLST). The bla(NDM-1) gene was identified in four Enterobacteriaceae isolates (two Escherichia coli, one Klebsiella pneumoniae and one Proteus mirabilis) from four patients in New Zealand hospitals in 2009 and 2010. In addition, the bla(NDM-6) gene, which differed from bla(NDM-1) by a point mutation at position 698 (C→T), was also identified in an E. coli isolate from the same patient who harboured the bla(NDM-1)-positive P. mirabilis. All four patients had recently been hospitalised or received health care in India. Four of the isolates also produced a CTX-M-15 extended-spectrum ß-lactamase and/or plasmid-mediated AmpC ß-lactamase, and all five isolates harboured the plasmid-mediated 16S rRNA methylase rmtC gene. The E. coli types were diverse by MLST, and the K. pneumoniae isolate belonged to the internationally disseminated sequence type 11 (ST11) clone. These findings further illustrate the diversity of phenotypic and genotypic features found in association with bla(NDM), in addition to documenting the international spread of this resistance mechanism, notably into a country with historically low rates of antimicrobial resistance.

Prevalence and types of extended-spectrum beta-lactamases among urinary Escherichia coli and Klebsiella spp. in New Zealand.

The aims of this survey were (i) to determine the prevalence of extended-spectrum beta-lactamases (ESBLs) among urinary Escherichia coli and Klebsiella spp. in New Zealand (NZ), (ii) to identify the relative prevalence of ESBL types and (iii) to investigate clonality among ESBL-producing E. coli and Klebsiella spp. During a 4-week period in 2006, 86% of NZ hospital and community diagnostic microbiology laboratories participated in the survey and referred isolates to the national reference laboratory. A total of 86 ESBL-producing isolates were identified, comprising 55 E. coli and 31 Klebsiella spp. (all Klebsiella pneumoniae), equating to prevalence rates of 0.7% and 4.2%, respectively. The majority of the ESBL-producing E. coli (80.0%) and K. pneumoniae (58.6%) were reported to be from community-acquired urinary tract infections. CTX-M-15 and CTX-M-14 accounted for 75.9% and 13.3%, respectively, of the ESBL types identified. A novel ESBL, designated CTX-M-68, was identified. Most CTX-M-15-producing isolates were multiresistant to three or more antibiotic classes. Pulsed-field gel electrophoresis typing identified a wide diversity of strains among the ESBL-producing E. coli, whereas the K. pneumoniae were more clonal. The results of this survey show that the prevalence of ESBLs has increased in recent years in NZ, that CTX-M ESBLs are almost wholly dominant and that ESBL-producing organisms are already established as community-acquired pathogens.

Antimicrobial susceptibility among Neisseria gonorrhoeae in New Zealand in 2002.

AIM: To estimate the prevalence of antimicrobial resistance among Neisseria gonorrhoeae, and to determine whether the increase in ciprofloxacin resistance observed in Auckland in 2001 had occurred in other parts of the country. METHODS: The antimicrobial susceptibility of N. gonorrhoeae (isolated in New Zealand over a 4-month period between April and August 2002) was tested at either LabPlus, Auckland District Health Board, or at ESR, using the same agar dilution method. RESULTS: The prevalence of resistance to the antimicrobials tested was: ceftriaxone, 0%; ciprofloxacin, 6.8%; penicillin, 9.0%; spectinomycin, 0%; and tetracycline, 27.8%. There were few statistically significant geographical differences in resistance within New Zealand. Gonococcal infections acquired in Asia were more likely to be ciprofloxacin and penicillin resistant than infections acquired in New Zealand. CONCLUSIONS: Ciprofloxacin resistance among N. gonorrhoeae in New Zealand has reached a level where this antibiotic is no longer the most appropriate first-line treatment. In fact, ceftriaxone should now be considered the most reliable option for the treatment and control of gonorrhoea in New Zealand, particularly in the Northland/Auckland region.