New Zealand Journal of Marine and Freshwater Research abstracts
Assessment of antibiotic activity in surface water of the lower Taieri
Plain and impacts on aquatic bacteria in Lake Waipori, South Otago, New Zealand
Marc Schallenberg†
Amy Armstrong
Department of Zoology
University of Otago
P.O. Box 56
Dunedin, New Zealand
email: marc.schallenberg@stonebow.otago.ac.nz
†Author for correspondence.
Abstract Veterinary antibiotics are widely used in New
Zealand and around the world to treat bacterial infections and for non-therapeutic
use as growth promoters. There is growing concern that un-metabolised antibiotics
pass through stock and enter the environment, facilitating antibiotic resistance
in pathogenic bacteria and harming aquatic ecosystems. Bioassay experiments
showed that filtered water from an agricultural drain reduced the abundance
of aquatic bacteria in Lake Waipori, a shallow coastal lake, whereas most
other planktonic organisms were not inhibited. This result was consistent
with the presence in the drain water of bacteriolytic antibiotics (e.g., penicillin).
Further experiments were conducted to examine the effects of admixtures of
water from the same agricultural drain both on the abundance and respiration
rate of aquatic bacteria in the lake. One of four experiments showed inhibition
of bacterial respiration consistent with the presence of bacteriostatic antibiotics
(e.g., tetracyclines, aminoglycosides, macrolides) in the drain water. No
further significant bacteriolytic effects were observed. A mixture of commonly
used antibiotics was not consistently effective at reducing bacterial abundance
or inhibiting bacterial respiration in lake water. Although we found evidence
of antibacterial activity in the drain water this was intermittent, indicating
either that antibiotic inputs to the drain were also intermittent, that other
environmental factors intermittently affected the potency of antibiotics
in the drain water, and/or that aquatic bacteria exhibited temporally variable
resistance to antibiotics.
Keywords agriculture; veterinary; bioassay; screening;
pharmaceuticals; antibiotics
M02094; Online publication date 15 March 2004; Received 22 November 2002;
accepted 23 October 2003
New Zealand Journal of Marine and Freshwater Research, 2004, Vol. 38:
19-28
0028-8330/04/3801-0019 © The Royal Society of New Zealand 2004
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