David R Murdoch

University of Otago, Taieri, Otago Region, New Zealand

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Publications (149)782.5 Total impact

  • Clinical infectious diseases : an official publication of the Infectious Diseases Society of America. 07/2014;
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    ABSTRACT: Previous randomized controlled trials of vitamin D supplementation and blood pressure (BP) mainly have given vitamin D for short periods (<6 months) or at low doses (400 IU per day). This study aims to determine whether long-term high-dose vitamin D taken for 18 months lowers BP. Adults were recruited from a healthcare organization or university into a double-blind controlled trial and randomized to receive either vitamin D3 200 000 IU for 2 months followed by 100 000 IU monthly up to 18 months (n=161) or placebo (n=161). BP was measured at baseline, 5, and 18 months. Subjects had a mean (SD) age of 47.6 (9.7) years, 75% were women, and 94% were of European ancestry (white). Mean (SD) 25-hydroxyvitamin D3 changed from 73 (22) nmol/L at baseline to 124 (28) nmol/L at 18 months in the vitamin D group, and from 71 (22) nmol/L to 56 (22) nmol/L in the placebo group. Mean BP was similar for the vitamin D and placebo groups at baseline (123.4/76.3 versus 122.6/75.6 mm Hg; respectively). The mean change (95% confidence interval) in BP at 18 months minus baseline in the vitamin D group compared with placebo group was -0.6 (-2.8 to 1.6) mm Hg for systolic (P=0.61) and 0.5 (-1.1, 2.2) mm Hg for diastolic (P=0.53). Long-term vitamin D supplementation, which increased mean 25-hydroxyvitamin D3 concentration >100 nmol/L for 18 months, had no effect on systolic or diastolic BP in predominantly white, healthy adults without severe vitamin D deficiency. Beneficial effects on BP cannot be ruled out for other populations.
    Hypertension 06/2014; · 6.87 Impact Factor
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    ABSTRACT: Vitamin D deficiency is associated with infectious diseases; however, it is not known whether vitamin D levels are affected by acute infection. Our aim was to establish whether 25-hydroxyvitamin D (25OHD) levels taken during an acute bacterial infection are representative of baseline levels.
    Journal of Paediatrics and Child Health 06/2014; · 1.25 Impact Factor
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    ABSTRACT: We retrospectively examined medical records of 87 patients with HACEK bacterbaemia to determine whether endocarditis was present as defined by the Duke criteria. The overall positive predictive value (PPV) of HACEK bacteraemia for endocarditis was 60%. The PPV varied with different HACEK species from 0% (Eikenella corrodens) to 100% (Aggregatibacter actinomycetemcomitans).
    Journal of Medical Microbiology 03/2014; · 2.30 Impact Factor
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    ABSTRACT: The International Collaboration on Endocarditis Prospective Cohort Study (ICE-PCS) collected worldwide data on the presentation, management and outcome of infective endocarditis (IE). We present data from patients with endocarditis enrolled from New Zealand. Patients who fulfilled the Duke criteria for definite or probable endocarditis were enrolled from five district health boards: Auckland, Counties Manukau, Waitemata, Capital and Coast, and Canterbury, between June 2000 and September 2005. There were 336 New Zealand patients enrolled in the ICE-PCS. Prosthetic valve endocarditis occurred in 31%. Underlying medical conditions were present in 28% of patients, but only 4% of patients had rheumatic heart disease. Forty patients (12%) had healthcare-associated endocarditis. Viridans streptococci were the most common cause of IE (32%), followed by Staphylococcus aureus (24%). Patients with S. aureus IE were more likely to present within a week of symptom onset than those with viridans streptococcus IE (OR 4.18, 95% CI 2.36-7.42). Surgery was performed in 33% of patients. In total, 20 patients (6%) died in hospital. Those with endocarditis caused by coagulase-negative staphylococci had an increased risk of death compared with those viridans streptococcus endocarditis (RR 4.7, 95% CI 1.2-17). The risk of stroke was higher in those with endocarditis caused by S. aureus and coagulase-negative staphylococci (RR 2.7, 95% CI 1.2-6.05, and 4.9, 95% CI 1.9-13, respectively). While viridans streptococci remain the predominant causative organisms of IE in New Zealand, many 'traditional' clinical and management aspects of this disease no longer apply. This paper provides a reference for local practitioners assessing and managing IE.
    The New Zealand medical journal 01/2014; 127(1391):38-51.
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    ABSTRACT: Pneumococcal disease is a significant cause of morbidity and mortality in young children in Nepal, and currently available pneumococcal conjugate vaccines offer moderate coverage of invasive disease isolates.
    PLoS ONE 01/2014; 9(6):e98739. · 3.53 Impact Factor
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    European Respiratory Journal 12/2013; · 6.36 Impact Factor
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    ABSTRACT: Observational studies have reported an inverse association between serum 25-hydroxyvitamin D (25OHD) concentrations and Staphylococcus aureus nasal carriage; however, clinical trials of vitamin D supplementation are lacking. To assess the effect of vitamin D3 supplementation on persistent S. aureus nasal carriage we conducted a randomized, double-blind, placebo-controlled trial among 322 healthy adults. Participants were given an oral dose of either 200 000 IU vitamin D3 for each of 2 months, followed by 100 000 IU monthly or placebo in an identical dosing regimen, for a total of 18 months. Nasal swabs for S. aureus culture and serum for 25OHD measurement were obtained at baseline, 6, 12 and 18 months of study. The mean baseline concentration of 25OHD was 72 nM (SD 22 nM). Vitamin D3 supplementation increased 25OHD levels which were maintained at >120 nM throughout the study. Nasal colonization by S. aureus was found in 31% of participants at baseline. Persistent carriage, defined as those that had positive S. aureus nasal cultures for all post-baseline swabs, occurred in 20% of the participants but vitamin D3 supplementation was not associated with a reduction in persistent carriage (OR = 1.39, 95% CI 0.63-3.06). Risk factor analysis showed that only gender was significantly associated with carriage, where women were less likely to be carriers than men (relative risk 0.83, 95% CI 0.54-0.99). Serum 25OHD concentrations were not associated with the risk of carriage. In conclusion, monthly administration of 100 000 IU of vitamin D3 did not reduce persistent S. aureus nasal carriage.
    Clinical Microbiology and Infection 07/2013; · 4.58 Impact Factor
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    ABSTRACT: Background. Legionnaires' disease cannot be clinically or radiographically distinguished from other causes of pneumonia, and specific tests are required to make the diagnosis. Currently, testing occurs erratically and, instead, clinicians rely on empiric treatment strategies and ignore public health implications of the diagnosis. We aimed to measure the increase in case detection of legionnaires' disease following the introduction of routine PCR testing of respiratory specimens. PCR is the most sensitive diagnostic tool for legionnaires' disease. Methods. In a quasi-experimental study in Christchurch, New Zealand, we compared the number of hospitalized cases of legionnaires' disease diagnosed during a two-year period before the introduction of a routine PCR testing strategy (November 2008 to October 2010) with a similar period after the introduction (November 2010 to October 2012). With this testing strategy, all respiratory specimens from hospitalized patients with pneumonia sent to the region's sole tertiary-level laboratory were tested for Legionella by PCR, whether requested or not. Results. During November 2008 to October 2010 there were 22 cases of legionnaires' disease compared with 92 during November 2010 to October 2012. Of 1834 samples tested since November 2010, 1 in 20 was positive, increasing to 1 in 9 during peak Legionella season (November to January). Increasing bacterial load was associated with increasing disease severity. Conclusion. In our region, the burden of legionnaires' disease is much greater than was previously recognized. Routine PCR testing provides results within a clinically-relevant time frame and enables improved characterization of the regional epidemiology of legionnaires' disease.
    Clinical Infectious Diseases 07/2013; · 9.37 Impact Factor
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    ABSTRACT: OBJECTIVES: To determine whether systematic testing of faecal samples with a broad range multiplex PCR increases the diagnostic yield in patients with diarrhoea compared with conventional methods and a clinician initiated testing strategy. METHODS: 1758 faecal samples from 1516 patients with diarrhoea submitted to two diagnostic laboratories were tested for viral, bacterial, and parasitic pathogens by Fast-Track Diagnostics multiplex real-time PCR kits and conventional diagnostic tests. RESULTS: Multiplex PCR detected pathogens in 530 samples (30%): adenovirus (51, 3%), astrovirus (95, 5%), norovirus (172, 10%), rotavirus (3, 0.2%), Campylobacter jejuni/coli (85, 5%), Salmonella spp. (22, 1%), Clostridium difficile (72, 4%), entero-haemorrhagic Escherichia coli (21, 1%), Cryptosporidium spp. (3, 0.2%), Entamoeba histolytica (1, 0.1%), and Giardia lamblia (59, 3%). In contrast, conventional testing detected a pathogen in 324 (18%) samples. CONCLUSIONS: Using a systematic approach to the diagnosis of gastroenteritis improved diagnostic yield. This enhanced detection with PCR was achieved by a combination of improved detection of individual pathogens and detection of pathogens not requested or unable to be tested by conventional tests. This approach also allowed earlier identification for most pathogens and created a workflow which is likely to adapt well for many diagnostic laboratories.
    The Journal of infection 04/2013; · 4.13 Impact Factor
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    ABSTRACT: Nucleic acid detection methods are being increasingly used for the diagnosis of Mycobacterium tuberculosis (1).…
    Journal of clinical microbiology 04/2013; · 4.16 Impact Factor
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    ABSTRACT: The Vi capsular polysaccharide (ViPS) protects Salmonella enterica subspecies enterica serotype Typhi (S.Typhi) in vivo by multiple mechanisms. Recent microbiological reports from typhoid endemic countries suggest that acapsulate S.Typhi may occur in nature and contribute to clinical typhoid fever that is indistinguishable from disease caused by capsulate strains. The prevalence and genetic basis of ViPS-negative S.Typhi isolates in children from Kathmandu, Nepal, were tested in 68 isolates. Although 5.9% of isolates tested negative for capsular expression by slide agglutination tests, a novel multiplex PCR assay and individual PCR analyses demonstrated the presence of all 14 genes responsible for the synthesis, transportation and regulation of the ViPS. These data suggest that phenotypically acapsulate S.Typhi may not have a genetic basis for the same.
    Journal of Tropical Pediatrics 04/2013; · 1.01 Impact Factor
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    ABSTRACT: Multiplex PCR has become the test of choice for the detection of multiple respiratory viruses in clinical specimens. However, there are few direct comparisons of different PCR assays. This study compares 4 different multiplex PCR assays for the recovery of common respiratory viruses. We tested 213 respiratory specimens using four different multiplex PCR assays: the xTAG respiratory viral panel fast (Abbott Molecular Laboratories), Fast-track Respiratory Pathogen assay (Fast-track Diagnostics), Easyplex respiratory pathogen 12 kit (Ausdiagnostics), and an in-house multiplex real-time PCR assay. The performance of the four assays was very similar, with 93-100% agreement for all comparisons. Other issues, such as through-put, technical requirements and cost, are likely to be as important for making a decision about which of these assays to use given their comparative performance.
    Journal of virological methods 04/2013; · 2.13 Impact Factor
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    ABSTRACT: A suite of volatiles have previously been identified as specific markers of Mycobacterium tuberculosis metabolism in vitro. These markers - methyl phenylacetate, methyl p-anisate, methyl nicotinate, o-phenylanisole with the addition of methyl salicylate, may also be derived from other sources and confound development of a breath test for tuberculosis. To identify potential sources of these potential biomarkers food products, cosmetics, TB medication, environmental air and cigarette smoke were analysed for these markers using solid phase microextraction coupled with Gas Chromatography/Mass Spectrometry. Breath from healthy subjects, including smokers was also tested. Methyl salicylate was commonly detected, making this unsuitable as a specific marker for M. tuberculosis. Methyl nicotinate was detected repeatedly in cigarettes. Methyl phenylacetate was detected in 1.7% of healthy subjects and o-phenylanisole in just 1% of healthy breath indicating these may be more suitable for inclusion in the tuberculosis breath test due to their low "background" level. These results justify further clinical studies to further explore these markers as specific indicators of M. tuberculosis infection.
    Tuberculosis (Edinburgh, Scotland) 03/2013; · 2.54 Impact Factor
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    ABSTRACT: BACKGROUND: Pneumococcal pneumonia causes significant morbidity and mortality among adults. Given limitations of diagnostic tests for non-bacteremic pneumococcal pneumonia, most studies report the incidence of bacteremic or invasive pneumococcal disease (IPD), and thus, grossly underestimate the pneumococcal pneumonia burden. We aimed to develop a conceptual and quantitative strategy to estimate the non-bacteremic disease burden among adults with community-acquired pneumonia (CAP) using systematic study methods and the availability of a urine antigen assay. METHODS AND FINDINGS: We performed a systematic literature review of studies providing information on the relative yield of various diagnostic assays (BinaxNOW(R) S. pneumoniae urine antigen test (UAT) with blood and/or sputum culture) in diagnosing pneumococcal pneumonia. We estimated the proportion of pneumococcal pneumonia that is bacteremic, the proportion of CAP attributable to pneumococcus, and the additional contribution of the Binax UAT beyond conventional diagnostic techniques, using random effects meta-analytic methods and bootstrapping. We included 35 studies in the analysis, predominantly from developed countries. The estimated proportion of pneumococcal pneumonia that is bacteremic was 24.8% (95% CI: 21.3%, 28.9%). The estimated proportion of CAP attributable to pneumococcus was 27.3% (95% CI: 23.9%, 31.1%). The Binax UAT diagnosed an additional 11.4% (95% CI: 9.6, 13.6%) of CAP beyond conventional techniques. We were limited by the fact that not all patients underwent all diagnostic tests and by the sensitivity and specificity of the diagnostic tests themselves. We address these resulting biases and provide a range of plausible values in order to estimate the burden of pneumococcal pneumonia among adults. CONCLUSIONS: Estimating the adult burden of pneumococcal disease from bacteremic pneumococcal pneumonia data alone significantly underestimates the true burden of disease in adults. For every case of bacteremic pneumococcal pneumonia, we estimate that there are at least 3 additional cases of non-bacteremic pneumococcal pneumonia.
    PLoS ONE 01/2013; 8(4):e60273. · 3.53 Impact Factor
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    ABSTRACT: Cardiac dysfunction is common in acute respiratory diseases and may influence prognosis. We hypothesised that blood levels of N-terminal B-type natriuretic peptide (NT-proBNP) and high-sensitivity Troponin T would predict mortality in adults with community-acquired pneumonia. A prospective cohort of 474 consecutive patients admitted with community-acquired pneumonia to two New Zealand hospitals over one year. Blood taken on admission was available for 453 patients and was analysed for NT-proBNP and Troponin T. Elevated levels of NT-proBNP (>220 pmol/L) were present in 148 (33%) and 86 (19%) of these patients respectively. Among the 26 patients who died within 30 days of admission, 23 (89%) had a raised NT-proBNP and 14 (53%) had a raised Troponin T level on admission compared to 125 (29%) and 72 (17%) of the 427 who survived (p values<0.001). Both NT-proBNP and Troponin T predicted 30-day mortality in age-adjusted analysis but after mutual adjustment for the other cardiac biomarker and the Pneumonia Severity Index, a raised N-terminal pro-brain natriuretic peptide remained a predictor of 30-day mortality (OR = 5.3, 95% CI 1.4-19.8, p = 0.013) but Troponin T did not (OR = 1.3, 95% CI 0.5-3.2, p = 0.630). The areas under the receiver-operating curves to predict 30-day mortality were similar for NT-proBNP (0.88) and the Pneumonia Severity Index (0.87). Elevated N-terminal B-type natriuretic peptide is a strong predictor of mortality from community-acquired pneumonia independent of clinical prognostic indicators. The pathophysiological basis for this is unknown but suggests that cardiac involvement may be an under-recognised determinant of outcome in pneumonia and may require a different approach to treatment. In the meantime, measurement of B-type natriuretic peptides may help to assess prognosis.
    PLoS ONE 01/2013; 8(5):e62612. · 3.53 Impact Factor
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    ABSTRACT: Observational studies have reported an inverse association between serum 25-hydroxyvitamin D (25-OHD) levels and incidence of upper respiratory tract infections (URTIs). However, results of clinical trials of vitamin D supplementation have been inconclusive. To determine the effect of vitamin D supplementation on incidence and severity of URTIs in healthy adults. Randomized, double-blind, placebo-controlled trial conducted among 322 healthy adults between February 2010 and November 2011 in Christchurch, New Zealand. Participants were randomly assigned to receive an initial dose of 200,000 IU oral vitamin D3, then 200,000 IU 1 month later, then 100,000 IU monthly (n = 161), or placebo administered in an identical dosing regimen (n = 161), for a total of 18 months. The primary end point was number of URTI episodes. Secondary end points were duration of URTI episodes, severity of URTI episodes, and number of days of missed work due to URTI episodes. The mean baseline 25-OHD level of participants was 29 (SD, 9) ng/mL. Vitamin D supplementation resulted in an increase in serum 25-OHD levels that was maintained at greater than 48 ng/mL throughout the study. There were 593 URTI episodes in the vitamin D group and 611 in the placebo group, with no statistically significant differences in the number of URTIs per participant (mean, 3.7 per person in the vitamin D group and 3.8 per person in the placebo group; risk ratio, 0.97; 95% CI, 0.85-1.11), number of days of missed work as a result of URTIs (mean, 0.76 days in each group; risk ratio, 1.03; 95% CI, 0.81-1.30), duration of symptoms per episode (mean, 12 days in each group; risk ratio, 0.96; 95% CI, 0.73-1.25), or severity of URTI episodes. These findings remained unchanged when the analysis was repeated by season and by baseline 25-OHD levels. In this trial, monthly administration of 100,000 IU of vitamin D did not reduce the incidence or severity of URTIs in healthy adults. anzctr.org.au Identifier: ACTRN12609000486224.
    JAMA The Journal of the American Medical Association 10/2012; 308(13):1333-9. · 29.98 Impact Factor
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    ABSTRACT: The differentiation of species within the Streptococcus mitis group has posed a problem in the routine diagnostic microbiology laboratory for some time. It also constitutes a major weakness of recently introduced matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) fingerprinting systems. As the phylogenetic resolution of the spectral similarity measures employed by these systems is insufficient to reliably distinguish between the most closely related members of the group, the major pathogen Streptococcus pneumoniae is frequently misidentified. In this study, a comparative analysis of MALDI-TOF spectra of several species from the S. mitis group has been performed in order to identify single peaks that could be used to improve mass spectrometry-based identification of the respective species. A characteristic peak profile could be identified that unambiguously distinguished the 14 S. pneumoniae isolates studied from 33 nonpneumococcal isolates of the S. mitis group. In addition, specific peak combinations could be assigned to other members of the group. The findings of this study suggest that it is possible to distinguish different species of the S. mitis group by close analysis of their mass peak profiles.
    Journal of clinical microbiology 06/2012; 50(9):2863-7. · 4.16 Impact Factor
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    ABSTRACT: In this study four monoclonal antibodies (MAbs) and two polyclonal antisera were raised against pneumococcal surface adhesion A (psaA), a 37 kDa cell wall protein, and were characterized. The MAbs were purified, isotyped, and epitope mapped with peptide microarrays. All monoclonals and polyclonals underwent testing in immunodot blot, Western blot, and ELISA assays to assess their specificity. All monoclonal antibodies belonged to isotype IgG1 κ. Peptide microarray mapping identified two likely epitopes, which could not be confirmed using synthetic peptides of the identified amino acid sequence. All four MAbs detected the 53 pneumococcal serotypes tested in the immunodot blot and only reacted with Streptococcus pseudopneumoniae in cross-reactivity studies by Western blot. The polyclonal antisera also recognized all tested pneumococcal serotypes and cross-reacted with S. pseudopneumoniae and Streptococcus oralis by Western blot. The MAbs cross-reacted with S. pseudopneumoniae in the ELISA. Both polyclonal antisera cross-reacted with all isolates tested in the ELISA. These antisera should be suitable to establish a diagnostic ELISA platform for pneumococcal antigen detection with polyclonal antisera as the capture antibody. The specificity of the four MAbs appears to be high as they only recognized S. pneumoniae and S. pseudopneumoniae. However, further testing of closely related streptococcal species is necessary to confirm this finding.
    Hybridoma (2005) 06/2012; 31(3):168-75. · 0.33 Impact Factor
  • Haur Sen Yew, David R Murdoch
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    ABSTRACT: The global epidemiology of infective endocarditis is becoming better understood with the initiation of multi-center collaborative studies and with an increasing number of case series being reported from countries outside North America and Europe. However, there are still many knowledge gaps and a lack of population-based data. For endocarditis in developed countries, the role of rheumatic heart disease as a predisposing factor is diminishing; the population is increasingly elderly, staphylococci are becoming much more important pathogens, and proportionally more are healthcare-associated. In developing countries, the epidemiology of infective endocarditis remains similar to North America and Europe from the middle of the twentieth century, affecting a younger age group, is often associated with rheumatic heart disease, and is predominantly caused by streptococci.
    Current Infectious Disease Reports 05/2012; 14(4):367-72.

Publication Stats

3k Citations
782.50 Total Impact Points

Institutions

  • 2003–2014
    • University of Otago
      • • Christchurch School of Medicine and Health Sciences
      • • Department of Microbiology and Immunology
      Taieri, Otago Region, New Zealand
    • Himalayan Rescue Association Nepal
      Kantipura, Central Region, Nepal
  • 2013
    • Auckland District Health Board
      Окленд, Auckland, New Zealand
  • 2009–2013
    • University of Oxford
      • Department of Paediatrics
      Oxford, ENG, United Kingdom
    • Johns Hopkins Bloomberg School of Public Health
      • Department of International Health
      Baltimore, Maryland, United States
    • North Carolina Clinical Research
      Raleigh, North Carolina, United States
  • 2006–2013
    • Canterbury Health Laboratories
      Christchurch, Canterbury Region, New Zealand
  • 1995–2013
    • Canterbury District Health Board
      Christchurch, Canterbury Region, New Zealand
  • 2012
    • Patan Academy of Health Sciences
      Lalitpur, Central Region, Nepal
    • University Medical Center Hamburg - Eppendorf
      • Department of Medical Microbiology, Virology and Hygiene
      Hamburg, Hamburg, Germany
    • Mahidol University
      • Department of Tropical Pathology
      Bangkok, Bangkok, Thailand
  • 2011
    • Oxford University Hospitals NHS Trust
      Oxford, England, United Kingdom
    • Turku University Hospital
      Turku, Province of Western Finland, Finland
  • 1999–2011
    • Duke University
      Durham, North Carolina, United States
  • 2008
    • IDIBAPS August Pi i Sunyer Biomedical Research Institute
      Barcino, Catalonia, Spain
  • 2001–2007
    • Duke University Medical Center
      • • Department of Medicine
      • • Division of Infectious Diseases
      Durham, North Carolina, United States
  • 2002
    • University of Canterbury
      Christchurch, Canterbury Region, New Zealand