Genetic Characterization and Antibiotic Resistance of Campylobacter jejuni Isolated from Meats, Water, and Humans in Sweden

Abstract

The incidence of Campylobacter jejuni has increased during the last decade, and today it is the leading cause of bacterial enteritis in most developed countries. Still, there is a lack of knowledge about infection routes and to what extent identified sources are responsible for spreading the bacterium to humans. The major objective of this work was to explore the genetic similarity between C. jejuni isolated from different sources. C. jejuni isolated from patients (n ‫؍‬ 95), five types of meat (n ‫؍‬ 71), and raw water (n ‫؍‬ 11) during the year 2000 were subtyped by pulsed-field gel electrophoresis (PFGE). The pulsotypes obtained after digestion with SmaI revealed not only that C. jejuni is genetically diverse but also that specific pulsotypes occur frequently. Five clusters comprising 88 of the 162 SmaI-digested isolates were obtained. After digestion with KpnI most isolates in four of the five clusters were still indistinguishable, while the fifth cluster was strongly dissolved. The clusters comprised high frequencies of human and meat isolates, while only one of nine water isolates belonged to a cluster. The largest cluster comprised 21 human isolates, one raw water isolate, and seven chicken meat isolates, originating from at least six different broiler flocks. Low frequencies of antibiotic resistance were revealed when the meat and water isolates were tested for sensitivity to six antibiotics. Interestingly, the five isolates resistant to quinolones displayed similar or identical pulsotypes. The results showed that PFGE has proved useful in identifying clones and will be used in future work focusing on identification and eradication of the major reservoirs for common clones.

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

“…SmaI digestion, while less discriminatory, is sufficient in many cases to demonstrate that isolates are different. We believe that to demonstrate similarity, or that isolates are indistinguishable, digestion with two enzymes is essential, a finding also supported by other researchers (20,27,31 Epidemiological analysis. In this study, 90% of isolates could be linked retrospectively to notified campylobacteriosis cases, which is a rate 10% higher than that reported previously in the Auckland area of New Zealand (33).…”

Risk Factors for Campylobacteriosis: an Epidemiological Surveillance Study of Patients and Retail Poultry

“…Similarly, KpnI cleavage reduced the number of poultry isolates with a pulsotype matching that of a patient isolate from 69 to 41. This degree of overlap between pulsotypes of human and chicken isolates is similar to previously reported values (14,18).…”

“…The evidence for genetic stability is also supported by the results of a Finnish study, which found the same PFGE profiles in strains collected in three different years (11). Similarly, the major PFGE groups in the present study were also found in an earlier Swedish study that analyzed 177 isolates collected in 2000 from retail meat products (mostly chicken), patients, and water (18). In fact, the five major PFGE groups from that study were all among the six largest groups in the Campy-SET study.…”

“…Many studies have concluded that there is a substantial overlap of subtypes between patients and chickens but that the overlap is smaller for potential sources such as water, wild birds (black-headed gulls), wild mammals, sandy beaches, and cattle (4,6,14,18,24,25). However, making a direct correlation between the overlap of subtypes and the source of infection assumes that all subtypes are equal in terms of virulence and survival until the time of ingestion.…”

“…1A). The number of patient isolates with a pulsotype matching that of a poultry isolate was reduced from 72 to 44 after the use of a second restriction enzyme (KpnI) as described by Lindmark et al (18) (Fig. 1B).…”