f/ 3 Fort Lauderdale ARC Research Report FL 73-4
1 -- Persistence of Oxvtetracvcline H C1 in Coconut Palm
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R. F. McCoy v LIBRARY
IFAS, University of Florida, Agricultural Research Center
Fort Lauderdale, Florida 33314 SEP 29 176
June 1973 1
Objective: A .
Objective: F Univ. of Florida
To determine the longevity and ouantitv of oxvtetricyT1ine-- I4 L ...
present in coconut tissue after direct trunk injection.
Materials and Methods:
A young, vigorous, bearing coconut palm, having approximately 8 ft.
of trunk, was selected for antibiotic injection. Two grams of oxytetra-
cycline H C1 in one liter of water was injected under pressure directly
into the trunk about 2 ft. above the soil surface.
Leaf samples were excised at 3, 7, and 14 days following the anti-
biotic injection. At the same time leaves from a non-injected healthy
coconut palm were collected as a control. All samples were stored in a
freezer until ready for use. Th addition to the leaf samples, an immature
coconut was taken at 14 days and the milk assayed for activity.
Tissue samples were prepared for assay as follows: Ten gram samples
of each treatment were freeze dried and ground to a fine powder in a Wylie
mill. One gram of powder from each sample was mixed with water so that it
was reconstituted to 1/2 its natural concentration in the leaves. The pH
of the samples was 5.0 to 5.5
Samples were centrifuged 15 min at 15,nnn PPM and the supernatent used
for the assay. Non-cPntrifuaed samples were also assayed and were equiva-
lent in activity, however, readings were more difficult to make.
Assays for oxvtetracvcline H Cl .were made usino Racillus cereus
var. mvcoides as the test organism. Pifco antibiotic medium No. 3 nlus
1.5% agar served as the growth substrate. A bacterial spore suspension
was added to the medium after cooling and before pourino into 100 cm dia.
petric dishes. Stainless steel bioassay plates with 6 wells each were
placed in each of 10 poured and seeded netri dishes. To each well was
added 0.1 cc of the supernatent test solution, or a freshly nrenared
antibiotic standard. Plates were incubated overnight at 300C and zones
of inhibition of bacterial growth read the following morning.
Table 1. Rioassav for oxvtetracycline H C1 in coconut tissue usinq
Bacillus cereus var. mycoides as a test organism.
Treatment Dia of zone of inhibition, cm (n1 replicates) Mean deviation
non-injected 0 0 0 0 0 0 n 0
3 day 1.1 1.2 1.1 1.0 1,1 1.4 1.1 1.n 1.1 1.0 1.11 0.12
7 day 0.R 0.9 0.3 0.7 0.9 n.q n.R n.q7 n. n.o o.Pa nO.
14 day 0 0 0 0 0 0 n n 0 0 0 0
Standard 0.1 ppm 0.8 n.R O.p 0.7 0.8 0.7 0.p n.0 n.0 0. 0n.70 0.05
Standard 1.0 ppm 1.5 1.8 1.5 1.6 1.5 1.6 1.A 1.A 1.6 1.5 1.5R n.nO
Comparision of the values obtained in Table 1 with the standard curve
for oxytetracvcline H l1 (Fiq. 1) shows that the concentration was highest
at 3 days at ca. 3 ppm, dropping to ca. 0.2 npm at 7 days. (Since the
tissue samples were reconstituted to 1/? their natural concentration, the
ppm value for these treatments must he multiplied bv ?.) No traces of
oxytetracvcline H Cl were detectable in the non-iniected tissue samples
or in the samples taken 14 days after injection. The sensitivity
level of this test is n.l Dpm. In addition to the leaf tissue samples,
milk from an immature coconut was assayed 14 days after injection and
no traces of antibiotic were found.
Oxvtetracvcline H Cl appears to he rapidly translocated into
coconut foliage after trunk injection. The material is not persistent
and no traces were found after two weeks.
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