G S Hotter's research while affiliated with Massey University and other places

To study the occurrence and spatial distribution of Shiga toxin-producing Escherichia coli (STEC) O157 in calves less than 1-week-old (bobby calves) born on dairy farms in the North Island of New Zealand, and to determine the association of concentration of IgG in serum, carcass weight, gender and breed with occurrence of E. coli O157 in these calves. In total, 309 recto-anal mucosal swabs and blood samples were collected from bobby calves at two slaughter plants in the North Island of New Zealand. The address of the farm, tag number, carcass weight, gender and breed of the sampled animals were recorded. Swabs were tested for the presence of E. coli O157 using real time PCR (RT-PCR). All the farms were mapped geographically to determine the spatial distribution of farms positive for E. coli O157. K function analysis was used to test for clustering of these farms. Multiplex PCR was used for the detection of Shiga toxin 1 (stx1), Shiga toxin 2 (stx2), E. coli attaching and effacing (eae) and Enterohaemolysin (ehxA) genes in E. coli O157 isolates. Genotypes of isolates from this study (n = 10) along with human (n = 18) and bovine isolates (n = 4) obtained elsewhere were determined using bacteriophage insertion typing for stx encoding. Of the 309 samples, 55 (17.7%) were positive for E. coli O157 by RT-PCR and originated from 47/197 (23.8%) farms. E. coli O157 was isolated from 10 samples of which seven isolates were positive for stx2, eae and ehxA genes and the other three isolates were positive for stx1, stx2, eae and ehxA. Bacteriophage insertion typing for stx encoding revealed that 12/18 (67%) human and 13/14 (93%) bovine isolates belonged to genotypes 1 and 3. K function analysis showed some clustering of farms positive for E. coli O157. There was no association between concentration of IgG in serum, carcass weight and gender of the calves, and samples positive for E. coli O157, assessed using linear mixed-effects models. However, Jersey calves were less likely to be positive for E. coli O157 by RT-PCR than Friesian calves (p = 0.055). Healthy bobby calves are an asymptomatic reservoir of E. coli O157 in New Zealand and may represent an important source of infection for humans. Carriage was not associated with concentration of IgG in serum, carcass weight or gender.

Campylobacter jejuni is a leading cause of human bacterial gastroenteritis throughout the industrialized world. We investigated whether or not differences in gene complement at the lipooligosaccharide (LOS) biosynthesis locus can identify epidemiologically useful binary genomotypes in 87 C. jejuni isolates from poultry-associated multilocus sequence types (STs) collected during the course of a sentinel surveillance study. Using a PCR-based approach, we correlated assignment of both isolate LOS locus class and binary genomotype with ST. We found that isolates within STs 45, 190, 354 and 474 displayed mosaicism in gene complement at the intra-ST level. For example, based upon their binary genomotypes, we assigned individual ST-45 isolates from human clinical cases as probably originating from either a poultry or wild-bird source. However, intra-ST mosaicism in gene complement was observed alongside broader patterns of congruence in LOS locus class and gene complement that distinguished between isolates from different STs.