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Dispatch
Fluoroquinolone Resistance
in Campylobacter Absent from Isolates, Australia
Leanne Unicomb,* John Ferguson,† Thomas V Riley,‡ and Peter Collignon§
*OzFoodNet, Newcastle, Australia; †University of Newcastle, Newcastle,
Australia; ‡Western Australian Centre for Pathology & Medical Research,
Perth, Australia; and §The Canberra Hospital, Garran, Australia
Suggested citation
for this article:
Unicomb L, Ferguson J, Riley TV, Collignon P. Fluoroquinolone resistance
in Campylobacter absent from isolates, Australia. Emerg Infect Dis [serial
online] 2003 Nov [date cited]. Available from: URL: http://www.cdc.gov/ncidod/EID/vol9no11/03-0336.htm
Fluoroquinolone
resistance was detected in 12 of 370 Australian human Campylobacter
isolates; 10 of these were travel-associated, and for 2 isolates travel
status was unknown. No resistance was found in isolates known to be
locally acquired. In Australia, fluoroquinolones have not been licensed
for use in food production animals, a policy that may have relevance
for countries with fluoroquinolone-resistant Campylobacter.
In Australia, Campylobacter is the most commonly reported bacterial
foodborne pathogen with an annual incidence of 125/100,000 population
(1). Fluoroquinolone resistance in this pathogen is recognized
as an emerging public health problem related to the use of these antimicrobial
agents in food production animals. Data from many regions (United States,
Europe, and Thailand) that have licensed fluoroquinolones for therapeutic
use in animals have shown that such use results in the emergence of fluoroquinolone
resistance in Campylobacter jejuni and C. coli isolates
obtained from both humans and animals (2–4). Increasing
resistance in campylobacter may lead to infections that are unresponsive
to antimicrobial drug treatment and more severe disease. Smith (2)
demonstrated that resistant C. jejuni caused more prolonged diarrhea
in patients than susceptible strains.
Fluoroquinolone resistance may emerge during treatment in humans (3);
however, Smith (2) and others (5) demonstrated
that most detected resistant isolates come from patients who have not
been exposed to fluoroquinolones. Furthermore, as human-to-human transmission
of campylobacter is rare, patients infected with resistant campylobacter
are not an important source of resistance for other humans (4).
In Australia, fluoroquinolones have never been licensed for use in food
production animals. A small amount is used in companion animals: imports
of enrofloxacin began in 1995, and 49 kg was used in the financial year
1996–97 (6). In contrast, the average use of quinolones
in humans was 3,200 kg per year from 1992 to 1997 (6).
Australian data on fluoroquinolone resistance in human Campylobacter
isolates are limited. As part of a case-control study of risk factors
for Campylobacter infection conducted in New South Wales from 1999 to
2001, patients infected with this pathogen were recruited, and information
on various exposures was obtained by telephone interview. Patients were
asked about local and international travel in the 4 weeks before onset
of diarrhea. Isolates from patients were stored and subsequently tested
for resistance to 10 antimicrobial agents by using the National Committee
for Clinical Laboratory Standards method for Helicobacter species
(7). The Table shows proportions
of fluoroquinolone-resistant isolates from this case-control study. In
addition, results of two laboratory-based surveys of antimicrobial resistance,
one conducted on isolates from Western Australia and one conducted on
isolates from the Australian Capital Territory, are included. In these
last two studies, information on overseas travel was sought retrospectively.
Fluoroquinolone-resistant human Campylobacter isolates were rarely
detected in Australia. All ciprofloxacin-resistant isolates detected in
the three regions were from patients who appeared to have acquired their
infection outside the country (Table). Two locally
acquired isolates in the New South Wales study were resistant to nalidixic
acid only (i.e., they were sensitive to fluoroquinolones).
As Campylobacter infection is zoonotic, the absence of human, locally
acquired infections attributable to fluoroquinolone-resistant organisms
most likely reflects 1) the lack of use of fluoroquinolones in Australian
poultry (the most common source for C. jejuni) and other potential
meat sources and 2) the presence of little or no viable Campylobacter
organisms on imported chicken, which has been a source of resistant campylobacter
infections in the United Kingdom (5). Only cooked chicken
products can be imported into Australia.
Fluoroquinolones are critical therapeutic agents for many serious bacterial
infections because, in many cases, they may be the only active oral agents
available. Resistance following fluoroquinolone use can develop in many
gram-negative bacteria (campylobacter, salmonellae, and Escherichia
coli) carried by animals. These bacteria can be present in food. If
they subsequently cause infections in humans (or transfer their resistance
genes to other bacteria), no effective antimicrobial agents may be available
for treatment when serious disease occurs. Thus, their use in animals
should be avoided. Australia has never licensed the use of fluoroquinolone
agents in livestock. In contrast with other nations that have licensed
their use, fluoroquinolone resistance in Campylobacter isolates
and subsequent infections in humans acquired from meats eaten within the
country have not emerged in Australia. The Australian experience has implications
for the continued licensing of these agents in other countries for food
production animals.
Antimicrobial testing
of isolates from the New South Wales case-control study was funded by
OzFoodNet, enhanced surveillance program of the Department of Health
and Ageing, Australia.
Ms. Unicomb is an
epidemiologist with OzFoodNet, the Australian enhanced foodborne disease
surveillance program with particular involvement in studies of the risk
factors for campylobacter infection and subtyping methods for that organism.
References
- Blumer C, Roche P, Spencer J, Lin M, Milton A, Bunn
C, et al. Annual
report of the National Notifiable Diseases Surveillance System.
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et al. Quinolone-resistant
Campylobacter jejuni infections in Minnesota, 1992–1998.
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animals. N Engl J Med 1999;340:1581–2.
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| Table.
Fluoroquinolone resistance data for Australian Campylobacter
isolates |
|
|
Study location
|
Isolate source and collection period
|
Total no. tested
|
Proportiona of fluoroquinolone-resistant
isolates (%)
|
|
|
Locally acquired
|
Overseas acquired
|
Unknown acquisition status
|
|
|
New South Wales
|
Human feces
1999–2001
|
180b
|
0/144 (0)
|
3c/7 (43)
|
2c/29 (6.9)
|
|
Western Australia
|
Human feces
1999–2000
|
50b
|
|
4c
|
0/46 (0)
|
|
Australian Capital Territory
|
Human feces/blood 2001–2002
|
140d
|
|
3
|
0/137 (0)
|
|
| aNo. of resistant
isolates by acquisition status/total no. isolates tested in acquisition
status category. |
| bTesting by agar
dilution, Mueller-Hinton agar with 5% lysed sheep blood (7). |
| cResistant to ciprofloxacin
(MIC > 4 mg/L). |
| dTesting by disc-susceptibility
method (8). |
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