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Journal of Clinical Microbiology, September 2003, p. 4462-4464, Vol. 41, No. 9
0095-1137/03/$08.00+0 DOI: 10.1128/JCM.41.9.4462-4464.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.
In Vivo Development of Quinolone Resistance in Salmonella enterica Serotype Typhimurium DT104
Malthe A. Melau Kristiansen,1* Dorthe Sandvang,2 and Thorkild Bremholm Rasmussen3
Department of Clinical Microbiology, Research Unit for Clinical Microbiology, University of Southern Denmark, 6400 Sønderborg,1
Statens Serum Institut, 2300 Copenhagen,2
Department of Surgery A, Odense University Hospital, 5000 Odense, Denmark3
Received 24 March 2003/
Returned for modification 1 May 2003/
Accepted 2 June 2003

ABSTRACT
Salmonella enterica serotype Typhimurium definitive phage type
104 was isolated several times from the same patient over a
period of 2 years. The strain developed reduced sensitivity
to fluoroquinolones, and a mutation in the
gyrA gene that is
associated with reduced sensitivity to quinolones was identified.

TEXT
Salmonella enterica serotype Typhimurium definitive phage type
104 (DT104) has been reported with increasing frequency worldwide
throughout the last decade in both humans and farm animals.
The majority of Danish
Salmonella serotype Typhimurium DT104
isolates are pentaresistant, and the genes encoding the resistance
marker have been characterized and sequenced (
2,
11). The five
resistance genes are located on the chromosome in a large gene
cluster that was sequenced by Briggs and Fratamico in 1999 (
2)
and have been shown to be mobile (
14). In contrast to that finding,
the resistance mechanism for the quinolones is single-point
mutations in the gyrase genes resulting in decreased affinity
of DNA gyrase for the quinolone (
3,
6).
This study describes the course of illness of a 51-year-old woman over a period of 2 years. Prior to the study, she had undergone sigmoid resection due to perisigmoiditis complicated by a ureter lesion and leakage of the sigmoid anastomosis, both of which had been corrected surgically, and a colostomy had just recently been corrected. An abdominal ultrasound had shown cholecystolithiasis. She was admitted to the medical ward on 15 May 1999 due to diarrhea and dehydration. Within 24 h, the patient's temperature spiked to 40°C and her blood pressure dropped to 65 mm Hg, necessitating her transfer to the intensive care unit, where she received IVs containing metronidazole (500 mg every 8 h [q8h]), ceftriaxon (2g twice a day), and dopamine (10 µg/kg of body weight/min). On 26 May, blood cultures yielded Salmonella serotype Typhimurium DT104 organisms that were fully susceptible to fluoroquinolones. The antibiotic treatment was changed to oral ciprofloxacin (250 mg q12h), which was continued until 4 June, after which the patient was deemed to be free of the Salmonella serotype Typhimurium DT104 infection and was discharged from the hospital.
The patient was readmitted 9 August 2000 due to hypotension, fever, and pain in her left buttocks. An abscess in the gluteal region due to a fistula emanating from the sigmoid anastomosis was identified. The gluteal fascia was split, pus was cultured, and the patient was administered IVs of ampicillin (1g q6h) and metronidazole (500 mg q12h) until 1 September and gentamicin from 9 August to 12 August. Gentamicin was replaced by intravenous ciprofloxacin (200 mg q12h) on 12 August, and ciprofloxacin therapy was continued until 1 September due to culture yielding Streptococcus, ampicillin-resistant Escherichia coli, and Bacteroides. The patient gradually recovered and was deemed free of Salmonella serotype Typhimurium DT104. The patient was readmitted 11 December 2000 due to retraction of the colostomy. Her colon was rejoined, and an ileostomy was performed. Shortly after surgery, she fell ill and produced thin green stool in her stoma. A stool specimen was cultivated, and there was growth of Salmonella serotype Typhimurium DT104 once again. The patient was left untreated and recovered spontaneously. Feces specimens were cultivated again in mid-January 2001 and 5 September 2001, and both yielded Salmonella serotype Typhimurium DT104. In the interim, an attempt had been made to eradicate the Salmonella with a 4-week course of oral ciprofloxacin (250 mg q12h).
Colonies of Salmonella subsp. were serially isolated and serotyped as Salmonella enterica serotype Typhimurium DT104 (Table 1), described by Callow (4) and Anderson et al. (1). A susceptibility test was conducted in accordance with the method and materials described by Threlfall et al. (15), and the MIC of ciprofloxacin was determined by the E-test (AB Biodisk, Solna, Sweden). The extraction and preparation of DNA were performed as described by Gautom (5), and XbaI and BlnI were used for digestion (Roche Holding Ltd., Basel, Switzerland). Isolation of plasmid DNA from bacterial strains and subsequent profiling were performed as described by Kado and Liu (7). DNA preparation and PCR were performed according to the methods of Sandvang et al. (13) and Sandvang (12). The gyrA gene (GenBank accession no. X06744) (16) was amplified by using the primers gyrA-F (base pairs 186 to 213) and gyrA-B (base pairs 811 to 784) and resulted in a PCR product of 626 bp. The PCR products were purified and sequenced according to the methods of Sandvang (12).
The pulsed-field gel electrophoresis (PFGE) pattern of the DNA
digests yielded approximately 15 bands in the area between 50
and 1,000 kb (Fig.
1). Visual comparison showed that the PFGE
patterns of the four
Salmonella strains were indistinguishable.
Plasmid profiling revealed that the four strains all had two
small plasmids of approximate 2.2- and 2.6-kb lengths as well
as the large 95-kb serotype-associated plasmid (virulence plasmid).
All the
Salmonella serotype Typhimurium DT104 strains contained
the 626-bp gyrase PCR amplicons (
16). The three nalidixic acid-resistant
Salmonella serotype Typhimurium DT104 strains showed one-point
mutations in the
gyrA gene. A point mutation from C to T at
nt 431 in the
gyrA gene (
16) was found. The location of this
substitution corresponds to the codon 83 (numbered according
to Yoshida et al.) (
16). A point mutation from T
CC to T
TC (with
the change marked in bold) resulted in an amino acid substitution
from serine to phenylalanine. This substitution is well known
to result in decreased susceptibility to quinolones (
9,
10).
In the above case, the patient developed
Salmonella serotype
Typhimurium DT104 septicemia secondary to a gastrointestinal
infection. The
Salmonella serotype Typhimurium DT104 primarily
found in the patient's blood before antibiotic treatment showed
full susceptibility to fluoroquinolones. The patient was treated
with low doses of ciprofloxacin (250 mg q12h) for 9 days, and
three succeeding cultivations of feces over the next year still
yielded
Salmonella serotype Typhimurium DT104 organisms. Although
the indistinguishable PFGE patterns indicate complete identity
among all four serial isolates, the second isolate of this series
had reduced susceptibility to ciprofloxacin, (MIC, 0.190 µg/ml)
compared with that of the first ciprofloxacin-susceptible isolate
(MIC, 0.008 µg/ml). Resistance to ciprofloxacin remained
for the next isolates and correlated with a mutation present
in the
gyrA gene. Although epidemiological studies suggest a
relationship between the use of quinolones and the development
of quinolone resistance, to our knowledge this is the first
time that the evolution of ciprofloxacin resistance in
Salmonella serotype Typhimurium DT104 has been directly linked to quinolone
therapy in a patient.

ACKNOWLEDGMENTS
Jette Kristiansen is gratefully acknowledged for her comments.
We thank Lene Bay for providing technical assistance and Leonard
Amaral for helpful discussion.

FOOTNOTES
* Corresponding author. Mailing address: Department of Clinical Microbiology, Research Unit for Clinical Microbiology, University of Southern Denmark, Sønderborg Sygehus, Sydvang 1, 6400 Sønderborg, Denmark. Phone: 45 22 17 60 86. Fax: 45 74 18 27 43. E-mail:
makblast{at}hotmail.com.


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Journal of Clinical Microbiology, September 2003, p. 4462-4464, Vol. 41, No. 9
0095-1137/03/$08.00+0 DOI: 10.1128/JCM.41.9.4462-4464.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.
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