Lower-Than-Expected Vitamin A Concentrations in a Commercial Diet Associated with Uroliths and Pyelonephritis in Rats.

Five of 95 rats in an oral safety study developed uroliths, with two of these rats also developing pyelonephritis. Histology of the urinary tract revealed squamous metaplasia suggestive of vitamin A deficiency. Analysis of the diet showed around half the expected concentration of vitamin A, although the concentrations were close to the published nutritional requirements for rats. Due to the presence of squamous metaplasia of the transitional epithelium and the low vitamin A concentration in the diet, a presumptive diagnosis of vitamin A deficiency was made, although an interaction between the low vitamin A concentrations and other dietary components appears possible. Although the uroliths did not cause clinical signs of disease, the lesions observed during this study could have been misinterpreted as being due to the test substance. Observations from this study highlight the need for high-quality food to ensure background lesions do not develop when performing safety studies in rats.

Use of Genomics to Investigate Historical Importation of Shiga Toxin-Producing Escherichia coli Serogroup O26 and Nontoxigenic Variants into New Zealand.

Shiga toxin-producing Escherichia coli serogroup O26 is an important public health pathogen. Phylogenetic bacterial lineages in a country can be associated with the level and timing of international imports of live cattle, the main reservoir. We sequenced the genomes of 152 E. coli O26 isolates from New Zealand and compared them with 252 E. coli O26 genomes from 14 other countries. Gene variation among isolates from humans, animals, and food was strongly associated with country of origin and stx toxin profile but not isolation source. Time of origin estimates indicate serogroup O26 sequence type 21 was introduced at least 3 times into New Zealand from the 1920s to the 1980s, whereas nonvirulent O26 sequence type 29 strains were introduced during the early 2000s. New Zealand's remarkably fewer introductions of Shiga toxin-producing Escherichia coli O26 compared with other countries (such as Japan) might be related to patterns of trade in live cattle.

Phylogeographic Analysis Reveals Multiple International transmission Events Have Driven the Global Emergence of Escherichia coli O157:H7.

BACKGROUND: Shiga toxin-producing Escherchia coli (STEC) O157:H7 is a zoonotic pathogen that causes numerous food and waterborne disease outbreaks. It is globally distributed, but its origin and the temporal sequence of its geographical spread are unknown. METHODS: We analyzed whole-genome sequencing data of 757 isolates from 4 continents, and performed a pan-genome analysis to identify the core genome and, from this, extracted single-nucleotide polymorphisms. A timed phylogeographic analysis was performed on a subset of the isolates to investigate its worldwide spread. RESULTS: The common ancestor of this set of isolates occurred around 1890 (1845-1925) and originated from the Netherlands. Phylogeographic analysis identified 34 major transmission events. The earliest were predominantly intercontinental, moving from Europe to Australia around 1937 (1909-1958), to the United States in 1941 (1921-1962), to Canada in 1960 (1943-1979), and from Australia to New Zealand in 1966 (1943-1982). This pre-dates the first reported human case of E. coli O157:H7, which was in 1975 from the United States. CONCLUSIONS: Inter- and intra-continental transmission events have resulted in the current international distribution of E. coli O157:H7, and it is likely that these events were facilitated by animal movements (eg, Holstein Friesian cattle). These findings will inform policy on action that is crucial to reduce the further spread of E. coli O157:H7 and other (emerging) STEC strains globally.

Draft Whole-Genome Sequences of Three Diarrheagenic Escherichia coli Strains Isolated from Farmed Deer in New Zealand.

Escherichia coli bacteria commonly colonize the gastrointestinal tracts of farmed ruminants. Cattle are a well-recognized reservoir of zoonotic E. coli; we report here, however, the draft genome sequences of three diarrheagenic E. coli strains isolated from farmed red deer (Cervus elaphus) in the Manawatu region of New Zealand.

PFGE for Shiga toxin-producing Escherichia coli O157:H7 (STEC O157) and non-O157 STEC.

This chapter describes the procedure of generating pulsed-field gel electrophoresis (PFGE) profiles (DNA fingerprints) of Shiga toxin-producing Escherichia coli O157:H7 (STEC O157) and non-O157 STEC strains within 48 h, based on the standardized laboratory protocol developed by the Centers for Disease Control and Prevention, USA. The protocol describes the preparation of agarose plugs containing STEC O157 and non-O157 STEC cells, the digestion of bacterial DNA in the plugs using restriction endonuclease enzymes, and the electrophoresis conditions to generate the characteristic PFGE profiles of STEC O157 and non-O157 STEC isolates.

Geographic divergence of bovine and human Shiga toxin­producing Escherichia coli O157:H7 genotypes, New Zealand.

Shiga toxin-producing Escherichia coli (STEC)O157:H7 is a zoonotic pathogen of public health concern worldwide. To compare the local and large-scale geographic distributions of genotypes of STEC O157:H7 isolates obtained from various bovine and human sources during 2008­2011, we used pulsed-field gel electrophoresis and Shiga toxin­encoding bacteriophage insertion (SBI) typing. Using multivariate methods, we compared isolates from the North and South Islands of New Zealand with isolates from Australia and the United States. The STEC O157:H7 population structure differed substantially between the 2 islands and showed evidence of finer scale spatial structuring, which is consistent with highly localized transmission rather than disseminated foodborne outbreaks. The distribution of SBI types differed markedly among isolates from New Zealand, Australia, and the United States. Our findings also provide evidence for the historic introduction into New Zealand of a subset of globally circulating STEC O157:H7 strains that have continued to evolve and be transmitted locally between cattle and humans.

A prospective case-control and molecular epidemiological study of human cases of Shiga toxin-producing Escherichia coli in New Zealand.

BACKGROUND: Shiga toxin-producing Escherichia coli (STEC) O157:H7 and related non-O157 STEC strains are enteric pathogens of public health concern worldwide, causing life-threatening diseases. Cattle are considered the principal hosts and have been shown to be a source of infection for both foodborne and environmental outbreaks in humans. The aims of this study were to investigate risk factors associated with sporadic STEC infections in humans in New Zealand and to provide epidemiological information about the source and exposure pathways. METHODS: During a national prospective case-control study from July 2011 to July 2012, any confirmed case of STEC infection notified to regional public health units, together with a random selection of controls intended to be representative of the national demography, were interviewed for risk factor evaluation. Isolates from each case were genotyped using pulsed-field gel electrophoresis (PFGE) and Shiga toxin-encoding bacteriophage insertion (SBI) typing. RESULTS: Questionnaire data from 113 eligible cases and 506 controls were analysed using multivariate logistic regression. Statistically significant animal and environmental risk factors for human STEC infections were identified, notably 'Cattle livestock present in meshblock' (the smallest geographical unit) (odds ratio 1.89, 95% CI 1.04-3.42), 'Contact with animal manure' (OR 2.09, 95% CI 1.12-3.90), and 'Contact with recreational waters' (OR 2.95, 95% CI 1.30-6.70). No food-associated risk factors were identified as sources of STEC infection. E. coli O157:H7 caused 100/113 (88.5%) of clinical STEC infections in this study, and 97/100 isolates were available for molecular analysis. PFGE profiles of isolates revealed three distinctive clusters of genotypes, and these were strongly correlated with SBI type. The variable 'Island of residence' (North or South Island of New Zealand) was significantly associated with PFGE genotype (p = 0.012). CONCLUSIONS: Our findings implicate environmental and animal contact, but not food, as significant exposure pathways for sporadic STEC infections in humans in New Zealand. Risk factors associated with beef and dairy cattle suggest that ruminants are the most important sources of STEC infection. Notably, outbreaks of STEC infections are rare in New Zealand and this further suggests that food is not a significant exposure pathway.

Sero-prevalence of leptospirosis in workers at a New Zealand slaughterhouse.

AIMS: To undertake a pilot study to measure the sero-prevalence to Leptospira serovars Hardjo and Pomona in an occupationally exposed group. To evaluate worker age, sex and previous clinical episodes of leptospirosis as risk factors for sero-positivity. METHODS: A cross-sectional sero-prevalence study was conducted in February and March 2008 at a predominantly sheep slaughterhouse in Hawke's Bay, New Zealand. A single blood sample was collected from 242 meatworkers, comprising 145 men and 97 women. Sera were tested by the Microscopic Agglutination Test (MAT) with a titre cut point of 1:24, using serovars Pomona and Hardjo as antigens. Age, sex, and details of previous clinical episodes of leptospirosis were recorded. RESULTS: Overall sero-prevalence was 9.5%. Ten (4.1%) workers were positive to serovar Hardjo (titres 1:24-1:192), 13 (5.4%) were positive to serovar Pomona (titres 1:24-1:768), and one worker was positive for both serovars. Sero-prevalence was 13.1% and 4.1% in men and women, respectively. The median age for sero-positive workers was 54 years while that for sero-negative workers was 48 years. Twenty-three workers (9.5%) reported a leptospirosis disease episode 1-35 years previously, and 14 of those were sero-positive in the current study. CONCLUSION: The sero-prevalence observed suggests significant exposure to leptospirosis from sheep in meatworkers in the slaughterhouse studied. This sero-prevalence was similar to that reported in a survey in 1982. Further study is needed to determine the link between sero-prevalence and incidence, whether the prevalence of leptospirosis is similar in other slaughterhouses, and to develop a better understanding of risk factors important for the reduction of exposure of this occupationally acquired disease.