C. Nicol

The occurrence of Campylobacter subtypes in environmental reservoirs and potential transmission routes

Aim:  To identify potential reservoirs and transmission routes of human pathogenic Campylobacter spp.

Seasonal variation of Campylobacter types from human cases, veterinary cases, raw chicken, milk and water

During August 1996 (winter) and February 1997 (summer), a total of 180 Campylobacter isolates from a restricted geographical area were obtained from human and veterinary cases, raw milk and chicken, and untreated water. Isolates were typed by Penner serotyping and pulsed‐field gel electrophoresis (PFGE) of restriction enzyme‐produced DNA fragments. Differences were noted between the August and February serotypes, with the most, and fourth most frequently isolated serotypes in February being completely absent in August. Two other serotypes were more frequently found in the February isolates, while the reverse was true for two others. In contrast to the serotyping data, one PFGE restriction profile type was dominant in both seasons, and the pattern of distribution of isolates among the other restriction patterns was similar. Five groups of isolates in each month were indistinguishable by both typing methods. Only one group was common to both months. Another group, which was absent in August, dominated the February isolates. Marked differences in the types isolated in the two seasons were therefore evident. Some isolates from human cases were indistinguishable from others isolated from water and raw chicken, indicating possible routes of infection for humans.

Prevalence, Numbers, and Subtypes of Campylobacter jejuni and Campylobacter coli in Uncooked Retail Meat Samples

A national quantitative survey of Campylobacter jejuni and Campylobacter coli in 1,011 uncooked retail meat samples (beef, unweaned veal, chicken, lamb and mutton, and pork) was undertaken from August 2003 to June 2004 to establish baseline proportionality data. The presence, number, and type of Campylobacter present in each sample was assessed. Prevalences of C. jejuni and C. coli were 89.1% in chicken, 9.1% in pork, 6.9% in lamb and mutton, 3.5% in beef, and 10% in unweaned veal. C. jejuni was identified in the majority of positive samples (246 of 259). In chicken samples positive for C. jejuni, 40.2% had counts of <0.3 most probable number (MPN)/g, 50.5% had 0.3 to 10.0 MPN/g, 8.8% had 10.1 to 50.0 MPN/g, and 0.5% had 110 MPN/g. In other meats (49 samples), Campylobacter counts were < or = 0.3 MPN/g, except for one unweaned veal sample at > 10.9 MPN/g. Penner serotyping and SmaI macrorestriction genotyping using pulsed-field gel electrophoresis with 247 isolates revealed 17 Penner serotypes and 56 electrophoresis profiles. Seven Penner serotypes (HS1 complex, 2, 4 complex, 6, 11, 27, and 42) were represented by 10 or more isolates from chicken. When data from both typing methods were combined, 62 sero-genotypes were generated. In a comparison of these sero-genotypes with historical data for isolates from human cases, 71% of the beef isolates, 50% of the lamb and mutton isolates, 50% of the pork isolates, 41% of the chicken isolates, and 25% of the unweaned veal isolates were common to both sources. These results provide baseline proportionality profiles of Campylobacter in these five meats and will facilitate exposure assessment in combination with other information such as consumption data and subsequent quantitative risk assessment.

Statistical comparison of Campylobacter jejuni subtypes from human cases and environmental sources.

Aim:  To analyse Campylobacter jejuni typing data to define statistically which potential reservoirs and transmission sources contain isolates that are most similar to one another and to isolates from human infections.

Salmonella in uncooked retail meats in New Zealand.

A national quantitative survey of Salmonella in five types of uncooked retail meats in New Zealand was undertaken from August 2003 to May 2005 to establish baseline proportionality data. The overall prevalence of Salmonella in 1,108 meat samples was 1.1% (95% confidence interval, 0.6 to 1.9). Low prevalences of Salmonella in each meat type were observed, with 3% (1.2 to 6.1) in chicken, 1.3% (0.3 to 3.8) in lamb and mutton, 0.5% (0 to 3.0) in unweaned veal, 0.4% (0 to 2.4) in beef, and 0% (0 to 1.6) in pork. The Salmonella serotypes isolated were Salmonella Infantis from beef; Salmonella Typhimurium PT1 from unweaned veal and chicken; Salmonella sp. 6,7:k:-, Salmonella Enteritidis PT9a, Salmonella sp. 4,5,12:-:-, Salmonella sp. 4,12:-:-, and Salmonella Typhimurium PT160 from chicken; and Salmonella sp. 4:-:2 and Salmonella Brandenburg from lamb. Four of the isolates from chicken, Salmonella sp. 4,5,12:-:- (two isolates), Salmonella sp. 4,12:-:-, and Salmonella Typhimurium PT1, were very similar phenotypically and serologically to the attenuated Salmonella vaccine strain used in MeganVacl for poultry. One lamb sample yielded a count of Salmonella Brandenburg of 4.24 most probable number (MPN)/g, while all other positive samples were <1.0 MPN/g. The results provide baseline proportionality data for Salmonella in retail uncooked meats that will contribute invaluably toward future risk assessment in light of other information, such as consumption data that can be used for risk characterization.

A recurring salmonellosis epidemic in New Zealand linked to contact with sheep.

One strain of Salmonella Brandenburg began causing large numbers of human infections in New Zealand in 1998. We investigated the emergence of this strain using combined notification and laboratory data on human and animal disease and a case-control study. S. Brandenburg infection in humans was characterized by spring peaks and high rates in the southern half of the South Island. This epidemic pattern followed very closely that seen in sheep. The case-control study found that infection was significantly associated with occupational contact with sheep and having a household member who had occupational contact with sheep, during the 3 days prior to illness or interview. We conclude that S. Brandenburg has become established as a zoonotic disease in New Zealand. Preventing infection requires control of the epidemic in sheep through vaccination, changes in farm management practices, and promotion of hand washing and other precautions to protect farmers and their families.

Application of Pulsed-Field Gel Electrophoresis To Identify Potential Outbreaks of Campylobacteriosis in New Zealand

ABSTRACT Since 2002, New Zealands incidence of campylobacteriosis has exceeded 300 cases per 100,000 people per annum. To evaluate genetic variation in human isolates, 183 Campylobacter isolates were collected from a single clinical laboratory in Christchurch: 77 during an 8-week period in spring, and the rest 3 months later over a second 8-week period in autumn. Isolates were identified to the species level and subtyped using Penner serotyping (Campylobacter jejuni only) and pulsed-field gel electrophoresis (PFGE) using both SmaI and KpnI. Approximately two-thirds of the isolates could be grouped into clusters of between 2 and 26 isolates with indistinguishable SmaI and KpnI patterns. Less than 10% of the isolates were of the same type between the two sampling periods. The epidemiological relevance of the PFGE clusters was supported by temporal clustering, some spatial clustering, and some statistically significant demographic similarities among cases in a cluster. Conversely, patient cases yielding isolates which did not cluster with isolates from other cases were more likely to report recent overseas travel and less likely to live within larger urban centers. To identify whether these clusters actually represent common-source outbreaks, however, would require the detailed, rapid, and reiterative epidemiological investigation of cases within a PFGE cluster. The combined and timely application of subtyping and epidemiological investigation would appear to be a promising strategy for understanding campylobacteriosis in New Zealand.

Comparison of PCR Binary Typing (P-BIT), a New Approach to Epidemiological Subtyping of Campylobacter jejuni, with Serotyping, Pulsed-Field Gel Electrophoresis, and Multilocus Sequence Typing Methods

ABSTRACT To overcome some of the deficiencies with current molecular typing schema for Campylobacter spp., we developed a prototype PCR binary typing (P-BIT) approach. We investigated the distribution of 68 gene targets in 58 Campylobacter jejuni strains, one Campylobacter lari strain, and two Campylobacter coli strains for this purpose. Gene targets were selected on the basis of distribution in multiple genomes or plasmids, and known or putative status as an epidemicity factor. Strains were examined with Penner serotyping, pulsed-field gel electrophoresis (PFGE; using SmaI and KpnI enzymes), and multilocus sequence typing (MLST) approaches for comparison. P-BIT provided 100% typeability for strains and gave a diversity index of 98.5%, compared with 97.0% for SmaI PFGE, 99.4% for KpnI PFGE, 96.1% for MLST, and 92.8% for serotyping. Numerical analysis of the P-BIT data clearly distinguished strains of the three Campylobacter species examined and correlated somewhat with MLST clonal complex assignations and with previous classifications of “high” and “low” risk. We identified 18 gene targets that conferred the same level of discrimination as the 68 initially examined. We conclude that P-BIT is a useful approach for subtyping, offering advantages of speed, cost, and potential for strain risk ranking unavailable from current molecular typing schema for Campylobacter spp.

Comparison of Campylobacter jejuni genotypes from dairy cattle and human sources from the Matamata-Piako District of New Zealand

Aims:  To identify the prevalence and types of Campylobacter jejuni carried by dairy cattle and the extent of overlap of these types with those causing disease in humans.

Salmonella serotypes isolated from pet chews in New Zealand

Aims:  To survey the prevalence of Salmonella in imported and domestic pet chews for assessing their potential in introducing novel pathogenic and antimicrobial resistant Salmonella serotype clones into New Zealand, and as vehicles of salmonellosis in the domestic home environment.