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Journal of Clinical Microbiology, June 1998, p. 1787-1789, Vol. 36, No. 6
0095-1137/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Typing of Human Campylobacter jejuni
Isolates in Finland by Pulsed-Field Gel Electrophoresis
Marja-Liisa
Hänninen,1,*
Sini
Pajarre,2
Marja-Liisa
Klossner,2 and
Hilpi
Rautelin3
Department of Food and Environmental Hygiene,
Faculty of Veterinary Medicine1 and
Department of Bacteriology and Immunology, The Haartman
Institute, and Division of Bacteriology and Immunology, Helsinki
University Central Hospital HD Laboratories,3
FIN-00014 Helsinki University, and
Satakunta Central
Hospital, 28500 Pori,2 Finland
Received 5 December 1997/Returned for modification 11 February
1998/Accepted 11 March 1998
 |
ABSTRACT |
A total of 69 pulsed-field gel electrophoresis (PFGE) types were
identified among 176 Campylobacter jejuni isolates from
Finnish patients. In two geographic areas studied, five predominant
PFGE types comprised over 40% of the isolates. One-third of the
isolates had unique PFGE types. In small outbreaks, identical PFGE
patterns were demonstrated, indicating a common source of infection.
 |
TEXT |
Campylobacter
jejuni and Campylobacter coli are the most common
bacterial enteropathogens in developed countries.
Contaminated drinking water, unpasteurized milk, and poultry
consumption have been shown to be risk factors both in epidemics and in
sporadic cases (5, 7, 16). Serotyping has been the most
common typing method (8, 12), although biotyping and phage
typing have also been employed (11) to show the
epidemiologic association of strains isolated from patients or to
trace the possible routes of transmission from animals to
humans. Molecular methods, such as pulsed-field gel
electrophoresis (PFGE) (4, 15), are more distinguishing than
serotyping because several genotypes are found within a serotype. PFGE
has been shown to be a highly discriminatory method if a combination of
two restriction enzymes, SmaI and SacII, is used
(2, 4, 15). In the present study, PFGE typing was applied
for a longitudinal survey of human C. jejuni infections in
two different geographic areas, and the PFGE patterns of human isolates
were compared to those of C. jejuni isolated at the same time from Finnish chickens.
Bacterial isolates.
Two geographic areas were chosen, one to
represent urban living (Helsinki, area 1) and the other to represent a
more rural lifestyle (Satakunta, area 2). C. jejuni isolates
from fecal samples of enteritis patients with no foreign travel within
2 weeks prior to the illness were collected during a 1-year period
(area 1) or during 14 months (area 2). The samples were cultured on
Campylobacter blood-free selective medium (charcoal
cefoperazone deoxycholate agar; Oxoid Ltd., Basingstoke, Hampshire,
England). Chicken fecal samples (48 isolates) and meat samples (25 isolates, representing 10% of all meat samples tested) from area 1 were cultured on Campylobacter charcoal differential agar
medium directly (fecal samples) or after enrichment (meat samples). The
chickens originated from three major Finnish chicken producers. All
isolates were gram negative and oxidase, catalase, and hippurate
positive, and they grew at 37 and 43°C in an atmosphere of 5%
O2-10% CO2-85% N2. After the
original isolation, they were stored at
70°C. All isolates from
area 1 were tested for their susceptibility to ciprofloxacin (5-µg
disk; Oxoid) and erythromycin (15 µg; Oxoid). The susceptibility of
chicken isolates to enrofloxacin (5-µg disk [6]) was
tested.
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TABLE 1.
Predominant PFGE types among 176 human C. jejuni isolates and their presence in urban area 1, rural area
2, and chickens studied
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Typing of isolates by PFGE.
For PFGE analysis, the isolates
were grown on brucella blood agar for 2 days at 37°C in a
microaerobic atmosphere. The bacterial cells were harvested and treated
with formaldehyde to inactivate endogenous nucleases
(3). Otherwise, DNA was prepared by the method of
Maslow et al. (9). The bacteria were embedded in 1%
low-melting-point agarose plugs (SeaPlaque GTG; FMC
Bioproducts, Rockland, Maine). After DNA purification, 2-mm slices of
the agar plugs were digested with SmaI or SacII
restriction enzyme (New England Biolabs, Hertfordshire, United Kingdom)
as described by the manufacturer. The DNA fragments were separated with
Gene Navigator (Pharmacia LKB Biotechnology AB, Uppsala, Sweden) in a
1% agarose gel in 0.5× TBE buffer (45 mmol of Tris, 45 mmol of
boric acid, 1 mmol of EDTA) at 200 V. SmaI
fragments were separated with a ramped pulse from 0.5 to 25 s for 20 h, and SacII fragments were separated
with a ramped pulse from 0.3 to 18 s for 20 h. For the interpretation of PFGE results, the guidelines suggested by Tenover et
al. were used (17). SmaI patterns were designated
by roman numerals, and if isolates with a certain pattern could be
further subdivided by SacII, the additional patterns were
designated by capital letters (such as I/B).
With the two restriction enzymes, 48 combined PFGE types were found
among the area 1 isolates (107) and 30 such types were found among the
area 2 isolates (69). Nine PFGE types were identical in both areas.
Similar results were reported in a study showing that, in spite of
a high degree of diversity in SmaI-digested DNA profiles of
C. jejuni, some identical PFGE patterns were demonstrated in
three geographically separated sampling locations (10).
Although most cases seemed to be sporadic in our study, five
predominant PFGE types covered 42 and 44% of the isolates in area 1 and area 2, respectively (Table 1). The most common SmaI
pattern, I (Fig. 1, lanes 1, 2, and 11),
was further subdivided by SacII into nine different
patterns. A total of 68% of the SmaI pattern I isolates were of SacII type B (I/B [Fig.
2]). SacII pattern E (Fig. 2, lanes 10 and 11) was the most common pattern among chicken isolates. Similarly, SmaI pattern XI (Fig. 1, lane 5) was subdivided
into five patterns by SacII, of which T, Q, and U (Fig.
3, lanes 1 to 6) were seen only among
chicken isolates, whereas patterns R and S (Fig. 3, lanes 7 to 13) were
associated with human infections. SmaI patterns I and
IX formed two lineages with genetically related isolates. PFGE type
VII was identified only among human isolates. The interpretation of
SmaI patterns I and II was complicated, as only five
fragments were produced and small changes in the molecular sizes of two
fragments of about 300 to 350 kb (Fig. 1, lanes 1, 2, 6, 8, and 11)
were seen. SacII pattern analysis increased the information
on the relatedness of these isolates. For example, in Fig. 1, isolates
in lanes 6 and 8 differ in one of five fragments produced by
SmaI but in only 1 of 11 fragments produced by
SacII (Fig. 2, lanes 1 to 4).

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FIG. 1.
Examples of PFGE patterns of SmaI digests of
C. jejuni. Lanes 1, 2, and 11, pattern I; lane 3, pattern V;
lane 4, pattern VII; lane 5, pattern XI; lanes 6 and 8, pattern II;
lanes 7 and 10, pattern VI; lane 9, pattern IV; lane 12, pattern VIII;
lane 13, pattern XX. MW, lambda concatamer molecular size markers (48.5 kb). Numbers on the left indicate molecular sizes of DNA marker
bands.
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FIG. 2.
Examples of PFGE patterns of SmaI type I
strains after digestion with SacII. Included also are
SacII patterns of related SmaI pattern II (two
strains [lanes 1 and 4]) and SmaI pattern V (one strain
[lane 12]). Lanes 2, 3, 5, 6, and 7 represent pattern I/B
(SmaI/SacII), and lanes 8, 9, 10, and 11 represent patterns I/C, I/D, I/E, and I/E, respectively. MW, lambda
concatamer molecular size markers (48.5 kb). Arrows at the left
indicate molecular sizes 48.5, 97, 145, 194, 291, and 436.5 kb (bottom
to top, respectively).
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FIG. 3.
PFGE SacII patterns of SmaI type
XI isolates from chickens (lanes 1 to 6) and from humans (lanes 7 to
13). Lanes 1 to 3, pattern XI/T (chickens from retail shops); lanes 4 and 5, pattern XI/Q; lane 6, pattern XI/U (chicken fecal samples from a
production plant); lanes 7, 8, 9, and 13, pattern XI/R (human isolates,
infection acquired during a cruise in area 1, and a human isolate from
area 2); lanes 10 to 12, pattern XI/S (human isolates, infection
acquired after eating at a certain restaurant). Numbers on the left
indicate molecular sizes of DNA marker bands (lanes MW).
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According to the isolation season, a peak was seen in July-August in
both sampling areas, although this was more pronounced
in area 1. Certain types like I/B, V, and VII predominated in
June to August,
and type IV was common in area 2 during all seasons,
whereas type V was
identified only in area 1 (Table
1). During
late autumn, winter,
and early spring, PFGE types were unique.
Handling and eating poultry have been shown to be clear risk factors in
sporadic campylobacteriosis (
7). In the present
study,
chicken was suspected to be the source of infection in
14 cases with 11 different PFGE types. Eight of these 11 PFGE
types, including the
predominant pattern, I/B, were identical
with those seen in poultry.
This further confirmed the actual
role of poultry products in the
infection of these particular
patients. Four of the 10 most common
human PFGE types were not
found among chicken isolates.
Several small outbreaks were noted. In one outbreak, three patients who
had been on the same cruise had identical PFGE types
XI/R (Fig.
3,
lanes 7 to 9). In addition, three patients with
identical and unique
PFGE types XI/S (Fig.
3, lanes 10 to 12)
had eaten at the same
restaurant. Furthermore, at least five small
family outbreaks with
identical PFGE patterns were identified.
Fluoroquinolone resistance has been reported to be an increasing
problem in many countries (
1,
14). In 1990, 9% of
campylobacters
isolated from Finnish patients were resistant to
ciprofloxacin
(
13), and during the study period, the overall
ciprofloxacin
resistance in campylobacters was 32% at the Department
of Bacteriology
and Immunology. In the present study, all human
isolates tested
were susceptible to erythromycin, only a few (3 of 107)
isolates
were resistant to ciprofloxacin, and all chicken isolates were
susceptible to enrofloxacin. This could be because quinolones
are
not used in Finnish poultry production.
In conclusion, the application of PFGE typing for a longitudinal survey
of
Campylobacter infections in two restricted geographic
areas provided new information on the epidemiology of apparently
sporadic infections. Although PFGE analysis distinguished 69 types
among 176 isolates, five predominant types covered over 40% of
the
isolates in both areas studied. In particular, type I/B and
other types
related to it covered 17% of the isolates studied.
This suggests the
existence of certain common infection sources,
although one-third of
the patients were infected with unique genotypes.
In addition,
geographic differences were obvious, as only nine
PFGE types were
identical in the two areas studied. PFGE typing
not only was useful
in discriminating different
Campylobacter isolates but
also could suggest epidemiologic associations in
several small
outbreaks.
 |
ACKNOWLEDGMENTS |
Our study was financially supported by the Finnish Veterinary
Medical Foundation and the Yrjö Jahnsson Foundation, Helsinki, Finland.
 |
FOOTNOTES |
*
Corresponding author. Mailing address: Department of
Food and Environmental Hygiene, P.O. Box 57, FIN-00014 University of Helsinki, Finland. Phone: 358 9 708 49704. Fax: 358 9 708 49718. E-mail: marja-liisa.hanninen{at}helsinki.fi.
 |
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Journal of Clinical Microbiology, June 1998, p. 1787-1789, Vol. 36, No. 6
0095-1137/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
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