1 Northern Ireland Public Health Laboratory, Belfast City Hospital, Belfast BT9 7AD, Northern Ireland, UK; 2 Laboratory of Molecular Biology, School of Environmental Health Sciences, Azabu University, 11771 Fuchinobe, Sagamihara, Kanagawa, 8501229, Japan
Keywords: antibiotic resistance, shellfish, urease-positive thermophilic campylobacters
Sir,
Antibiotic resistance arising from the treatment of clinical and veterinary pathogens has become a widely debated topic over the last 5 years, in particular, the use of fluoroquinolones in poultry production and the emergence of ciprofloxacin-resistant thermophilic campylobacters in humans. Currently, what remains unclear is the contributionto antibiotic resistance in human campylobacteriosisof treating poultry with fluoroquinolones, and the contribution of clinical employment of fluoroquinolones in human medicine. Regardless of the source and routes of transmission, fluoroquinolone resistance has now emerged as a significant problem in both human and animal medicine.
We wish to report on the incidence of antibiotic resistance in environmental campylobacters, namely the urease-positive thermophilic Campylobacter (UPTC), isolated from shellfish in Northern Ireland, where no selective antibiotic pressure has been applied and where we have not been able to demonstrate antibiotic resistance, particularly among the fluoroquinolones. UPTC, a microaerophilic and Gram-negative bacterium, is an organism identified only relatively recently in England. After the original descriptions of UPTC appeared, isolates of UPTC were reported in France, Ireland and The Netherlands, and UPTC strains have also been found recently in Japan.1 The UPTC group was first described by Bolton et al.2 These strains were isolated from river water, sea water, mussels and cockles. In 1988, Megraud et al.3 reported the first isolation of UPTC from human clinical infection, where these organisms were isolated from an appendix as well as from human faeces. This group of organisms is the Campylobacter found most frequently in shellfish and waters.
UPTC organisms were isolated by selective enrichment from shellfish grown in several marine inshore waters around Northern Ireland, as previously described.4 From these samples, 21 isolates of this taxon were obtained and their susceptibility to ciprofloxacin (5 µg), enrofloxacin (5 µg), ofloxacin (5 µg), tetracycline (30 µg) and erythromycin (5 µg) was determined by disc susceptibility testing, in accordance with NCCLS methodology. As there is no standardized disc method specifically for Campylobacter, including guidance criteria for interpretation of zone sizes, susceptibility was assigned arbitrarily in comparison with known resistant and susceptible clinical isolates of Campylobacter jejuni, Campylobacter coli and Campylobacter lari isolated from human faeces. Results demonstrated that none of the environmental campylobacters isolated from the shellfish was resistant to any of the antibiotic agents tested. Although UPTC have been described occasionally in humans, we have not identified any of these organisms as a cause of gastrointestinal disease from human faecal specimens submitted to the Northern Ireland Public Health Laboratory for the period 1980present, nor have we been able to isolate these from the stools of healthy individuals. Similarly, we have not been able to isolate these organisms from poultry in Northern Ireland. Previously, we have reported that the niche for these organisms has been aquatic environments and wild seagulls.1,5 Consequently, as these organisms have never been isolated from human and animal sources, where antibiotics may have been used, it is unlikely that they have developed or acquired resistance mechanisms to overcome artificial antibiotic selective pressure. Conversely, where fluoroquinolones have been used in Northern Ireland and the Republic of Ireland in human and animal populations, we do experience varying degrees of fluoroquinolone resistance.6,7 This report therefore suggests that where selective antibiotic pressure is not applied, fluoroquinolone resistance is less likely to be acquired. Therefore, this report supports the concept of minimizing the employment of such antibiotics in both human and veterinary medicine to help reduce the burden of antibiotic resistance.
Acknowledgements
Anne Canney contributed to the work described in this article and in ordinary circumstances would have been a named author. Unfortunately, we were unable to contact her to obtain her consent to the submission of this article and we were therefore unable to add her name to the author list.
Footnotes
* Corresponding author. Tel: +44-28-9026-3554; Fax: +44-28-2589-2887; E-mail: jemoore{at}niphl.dnet.co.uk
References
1 . Matsuda, M., Kaneko, A., Fukuyama, M. et al. (1996). First finding of unease-positive thermophilic strains of campylobacter in river water in the Far East, namely, in Japan, and their phenotypic and genotypic characterization. Journal of Applied Bacteriology 81, 60812.[ISI]
2 . Bolton, F. J., Holt, A. V. & Hutchinson, D. N. (1985). Urease-positive thermophilic campylobacters. Lancet i, 12178.
3 . Megraud, F., Chevrier, D., Desplaces, N. et al. (1988). Urease-positive thermophilic campylobacter (Campylobacter laridis variant) isolated from an appendix and from human faeces. Journal of Clinical Microbiology 26, 10501.[ISI][Medline]
4 . Wilson, I. G. & Moore, J. E. (1996). Presence of Salmonella spp. and Campylobacter spp. in shellfish. Epidemiology and Infection 116, 14753.[ISI][Medline]
5 . Moore, J. E., Gilpin, D., Crothers, E. et al. (2002). Occurrence of Campylobacter spp. and Cryptosporidium spp. in seagulls (Larus spp.). Vector Borne Zoonotic Diseases 2, 1114.[CrossRef]
6
.
Moore, J. E., Crowe, M., Heaney, N. et al. (2001). Antibiotic resistance in Campylobacter spp. isolated from human faeces (19802000) and foods (19972000) in Northern Ireland: an update. Journal of Antimicrobial Chemotherapy 48, 4557.
7 . Lucey, B., Cryan, B., OHalloran, F. et al. (2002). Trends in antimicrobial susceptibility among isolates of Campylobacter species in Ireland and the emergence of resistance to ciprofloxacin. Veterinary Record 151, 31720.[ISI][Medline]
|