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

Abstract

Since 2002, New Zealand's 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.

Same-Day Subtyping of Campylobacter jejuni and C. coli Isolates by Use of Multiplex Ligation-Dependent Probe Amplification–Binary Typing

“…No follow-up investigation was undertaken to identify common infection sources for these small clusters of cases. A small 2002 study of human cases in the same catchment area as the current study also observed numerous small clusters of cases with indistinguishable PFGE profiles (20). A larger 2009 to 2010 study in the same geographical location (21), which also observed clustering of cases based on PFGE, demonstrated how, even with typing data from human, environmental, and food-related isolates, source identification can be difficult.…”

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

“…In addition, our results indicate the P-BIT approach to be more discriminatory than MLST and SmaI-based PFGE typing, another important feature. We found KpnI-based PFGE typing to be the most discriminatory of the methods used in our study, notwithstanding that not all strains prove typeable with this enzyme (18).…”

“…Some C. jejuni strains resist digestion with certain restriction enzymes, making characterization by PFGE typing problematic (13,18), while MLST target genes may not always provide data appropriate for the scheme (40). P-BIT relies on a code derived from positive or negative results of PCR analyses for a wide range of genes widely distributed in C. jejuni genomes and extrachromosomal elements and thus offers complete typeability.…”

“…Although the more widespread use of standardized methodologies for PFGE-based typing of bacterial pathogens has proven valuable for epidemiological studies (2,11,18,19,32), determining and using normalization parameters to enable a meaningful comparison of PFGE macrorestriction profiles can be challenging. Furthermore, the PFGE apparatus is of moderate cost.…”

Pulsed-Field Gel Electrophoresis Analysis of More than One Clinical Isolate of Campylobacter spp. from Each of 49 Patients in New Zealand

“…This paper describes the analysis by PFGE of more than one isolate of Campylobacter from each of 49 human cases of campylobacteriosis. Between April 2009 and February 2010, 673 clinical isolates of Campylobacter were obtained from clinical laboratories in Christchurch, New Zealand, as previously described (6). Isolates were identified as Campylobacter jejuni, C. coli, or C. lari using PCR assays (2,16), and PFGE analysis was performed as previously described (6), using the restriction enzymes SmaI and KpnI.…”